Journal covers
2024
- H. Guo, T. Ruoko, H. Zeng, and A. Priimagi, “Hydrogen‐Bonded Liquid Crystal Elastomers Combining Shape Memory Programming and Reversible Actuation,” Advanced Functional Materials, vol. 34, iss. 10, p. 2312068, 2024. doi:10.1002/adfm.202312068
[BibTeX] [Abstract] [Download PDF]
Abstract Materials that undergo shape morphing in response to external stimuli have numerous applications, e.g., in soft robotics and biomedical devices. Shape memory polymers utilize kinetically trapped states to, typically irreversibly, transfer between a programmed morphed shape and an equilibrium shape. Liquid crystal elastomers (LCEs), in turn, can undergo reversible actuation in response to several stimuli. This study combines the irreversible and reversible shape morphing processes to obtain LCEs that undergo shape‐programming via the shape memory effect and subsequent reversible actuation of the programmed shape. This is enabled by an LCE crosslinked via dynamic hydrogen bonds that break at high temperatures and reform upon cooling, endowing the shape memory effect, while mild thermal or photothermal stimulation yields the reversible actuation. Through this combination, proof‐of‐concept robotic application scenarios such as grippers that can adjust their shape for grabbing different‐sized objects and crawling robots that can morph their shape to adapt to constrained spaces, are demonstrated. It is anticipated that this work adds new diversity to shape‐programmable soft microrobotics.
@article{guo_hydrogenbonded_2024, title = {Hydrogen‐{Bonded} {Liquid} {Crystal} {Elastomers} {Combining} {Shape} {Memory} {Programming} and {Reversible} {Actuation}}, volume = {34}, issn = {1616-301X, 1616-3028}, url = {https://onlinelibrary.wiley.com/doi/10.1002/adfm.202312068}, doi = {10.1002/adfm.202312068}, abstract = {Abstract Materials that undergo shape morphing in response to external stimuli have numerous applications, e.g., in soft robotics and biomedical devices. Shape memory polymers utilize kinetically trapped states to, typically irreversibly, transfer between a programmed morphed shape and an equilibrium shape. Liquid crystal elastomers (LCEs), in turn, can undergo reversible actuation in response to several stimuli. This study combines the irreversible and reversible shape morphing processes to obtain LCEs that undergo shape‐programming via the shape memory effect and subsequent reversible actuation of the programmed shape. This is enabled by an LCE crosslinked via dynamic hydrogen bonds that break at high temperatures and reform upon cooling, endowing the shape memory effect, while mild thermal or photothermal stimulation yields the reversible actuation. Through this combination, proof‐of‐concept robotic application scenarios such as grippers that can adjust their shape for grabbing different‐sized objects and crawling robots that can morph their shape to adapt to constrained spaces, are demonstrated. It is anticipated that this work adds new diversity to shape‐programmable soft microrobotics.}, language = {en}, number = {10}, urldate = {2024-03-05}, journal = {Advanced Functional Materials}, author = {Guo, Hongshuang and Ruoko, Tero‐Petri and Zeng, Hao and Priimagi, Arri}, month = mar, year = {2024}, pages = {2312068}, file = {Full Text:files/911/Guo et al. - 2024 - Hydrogen‐Bonded Liquid Crystal Elastomers Combinin.pdf:application/pdf}, } - Y. Nemati, Z. Deng, H. Pi, H. Guo, H. Zhang, A. Priimagi, and H. Zeng, “A Scalable, Incoherent‐Light‐Powered, Omnidirectional Self‐Oscillator,” Advanced Intelligent Systems, vol. 6, iss. 2, p. 2300054, 2024. doi:10.1002/aisy.202300054
[BibTeX] [Abstract] [Download PDF]
Light‐fueled self‐oscillators based on stimuli‐responsive soft materials have been explored toward the realization of a myriad of nonequilibrium robotic functions, such as adaptation, autonomous locomotion, and energy conversion. However, the high energy density and unidirectionality of the light field, together with the unscalable design of the existing demonstrations, hinder their further implementation. Herein, a light‐responsive lampshade‐like smart material assembly as a new self‐oscillator model that is unfettered by the abovementioned challenges, is introduced. Liquid crystal elastomer with low phase transition temperature is used as the photomechanical component to provide twisting movement under low‐intensity incoherent light field. A spiral lampshade frame ensures an equal amount of light being shadowed as negative feedback to sustain the oscillation upon constant light field from omnidirectional excitation (0°–360° azimuth and 20°–90° zenith). Different‐sized oscillators with 6, 15, and 50 mm in diameter are fabricated to prove the possibility of scaling up and down the concept. The results provide a viewpoint on the fast‐growing topic of self‐oscillation in soft matter and new implications for self‐sustained soft robots.
@article{nemati_scalable_2024, title = {A {Scalable}, {Incoherent}‐{Light}‐{Powered}, {Omnidirectional} {Self}‐{Oscillator}}, volume = {6}, issn = {2640-4567, 2640-4567}, url = {https://onlinelibrary.wiley.com/doi/10.1002/aisy.202300054}, doi = {10.1002/aisy.202300054}, abstract = {Light‐fueled self‐oscillators based on stimuli‐responsive soft materials have been explored toward the realization of a myriad of nonequilibrium robotic functions, such as adaptation, autonomous locomotion, and energy conversion. However, the high energy density and unidirectionality of the light field, together with the unscalable design of the existing demonstrations, hinder their further implementation. Herein, a light‐responsive lampshade‐like smart material assembly as a new self‐oscillator model that is unfettered by the abovementioned challenges, is introduced. Liquid crystal elastomer with low phase transition temperature is used as the photomechanical component to provide twisting movement under low‐intensity incoherent light field. A spiral lampshade frame ensures an equal amount of light being shadowed as negative feedback to sustain the oscillation upon constant light field from omnidirectional excitation (0°–360° azimuth and 20°–90° zenith). Different‐sized oscillators with 6, 15, and 50 mm in diameter are fabricated to prove the possibility of scaling up and down the concept. The results provide a viewpoint on the fast‐growing topic of self‐oscillation in soft matter and new implications for self‐sustained soft robots.}, language = {en}, number = {2}, urldate = {2024-03-05}, journal = {Advanced Intelligent Systems}, author = {Nemati, Yasaman and Deng, Zixuan and Pi, Haotian and Guo, Hongshuang and Zhang, Hang and Priimagi, Arri and Zeng, Hao}, month = feb, year = {2024}, pages = {2300054}, file = {Full Text:files/897/Nemati et al. - 2024 - A Scalable, Incoherent‐Light‐Powered, Omnidirectio.pdf:application/pdf}, } - A. Berdin, H. T. Rekola, and A. Priimagi, “Complex Fourier Surfaces by Superposition of Multiple Gratings on Azobenzene Thin Films,” Advanced Optical Materials, vol. 12, iss. 4, p. 2301597, 2024. doi:10.1002/adom.202301597
[BibTeX] [Abstract] [Download PDF]
Abstract Diffractive optical elements (DOE) are integral components for lightweight and ultra‐thin optical elements due to their ability to manipulate light efficiently and accurately. However, conventional DOEs are static and cannot be altered after fabrication, which hinders their adaptability to changing requirements. To overcome this limitation, the potential of surface patterning on azobenzene thin films to fabricate reconfigurable DOEs is investigated. Using holographic lithography, surface topographies with sinusoidal surface relief gratings (SRG) are created and the superposition of up to 80 SRGs with high accuracy and minimal information loss in subsequent inscriptions is demonstrated. This is enabled by a surface patterning tool combining holographic lithography and digital holographic microscopy. Reconfigurable and adaptive optical elements can improve the efficiency of optical coupling and increase the sensitivity and selectivity of sensors, especially in applications such as near‐eye displays and plasmonic sensors. These results demonstrate the ability to create complex azobenzene‐based DOEs for advanced photonic applications, where the ability to alter optical elements is of high importance.
@article{berdin_complex_2024, title = {Complex {Fourier} {Surfaces} by {Superposition} of {Multiple} {Gratings} on {Azobenzene} {Thin} {Films}}, volume = {12}, issn = {2195-1071, 2195-1071}, url = {https://onlinelibrary.wiley.com/doi/10.1002/adom.202301597}, doi = {10.1002/adom.202301597}, abstract = {Abstract Diffractive optical elements (DOE) are integral components for lightweight and ultra‐thin optical elements due to their ability to manipulate light efficiently and accurately. However, conventional DOEs are static and cannot be altered after fabrication, which hinders their adaptability to changing requirements. To overcome this limitation, the potential of surface patterning on azobenzene thin films to fabricate reconfigurable DOEs is investigated. Using holographic lithography, surface topographies with sinusoidal surface relief gratings (SRG) are created and the superposition of up to 80 SRGs with high accuracy and minimal information loss in subsequent inscriptions is demonstrated. This is enabled by a surface patterning tool combining holographic lithography and digital holographic microscopy. Reconfigurable and adaptive optical elements can improve the efficiency of optical coupling and increase the sensitivity and selectivity of sensors, especially in applications such as near‐eye displays and plasmonic sensors. These results demonstrate the ability to create complex azobenzene‐based DOEs for advanced photonic applications, where the ability to alter optical elements is of high importance.}, language = {en}, number = {4}, urldate = {2024-03-05}, journal = {Advanced Optical Materials}, author = {Berdin, Alex and Rekola, Heikki T. and Priimagi, Arri}, month = feb, year = {2024}, pages = {2301597}, file = {Full Text:files/909/Berdin et al. - 2024 - Complex Fourier Surfaces by Superposition of Multi.pdf:application/pdf}, } - A. Priimagi, “Stronger together,” Nature Materials, vol. 23, iss. 2, pp. 167-169, 2024. doi:10.1038/s41563-023-01793-w
[BibTeX] [Download PDF]@article{priimagi_stronger_2024, title = {Stronger together}, volume = {23}, issn = {1476-1122, 1476-4660}, url = {https://www.nature.com/articles/s41563-023-01793-w}, doi = {10.1038/s41563-023-01793-w}, language = {en}, number = {2}, urldate = {2024-03-05}, journal = {Nature Materials}, author = {Priimagi, Arri}, month = feb, year = {2024}, pages = {167--169}, }
2023
- A. Koivuporras, A. Mailman, H. Guo, A. Priimagi, and R. Puttreddy, “Halogen Bonding in Halothiophene Building Blocks,” Crystal Growth & Design, vol. 23, iss. 12, pp. 8889-8896, 2023. doi:10.1021/acs.cgd.3c00958
[BibTeX] [Download PDF]@article{koivuporras_halogen_2023, title = {Halogen {Bonding} in {Halothiophene} {Building} {Blocks}}, volume = {23}, issn = {1528-7483, 1528-7505}, url = {https://pubs.acs.org/doi/10.1021/acs.cgd.3c00958}, doi = {10.1021/acs.cgd.3c00958}, language = {en}, number = {12}, urldate = {2024-03-05}, journal = {Crystal Growth \& Design}, author = {Koivuporras, Alisa and Mailman, Aaron and Guo, Hongshuang and Priimagi, Arri and Puttreddy, Rakesh}, month = dec, year = {2023}, pages = {8889--8896}, } - A. Eklund, S. Hu, Y. Fang, H. Savolainen, H. Pi, H. Zeng, A. Priimagi, O. Ikkala, and H. Zhang, “Bright and Switchable Whiteness in Macro‐Crosslinked Hydrogels,” Advanced Optical Materials, p. 2302487, 2023. doi:10.1002/adom.202302487
[BibTeX] [Abstract] [Download PDF]
Abstract Bright white color is often achieved in nature by the combination of polydisperse scattering structures and high refractive index contrast between the scatterer and the surrounding medium. Similarly, synthetic systems have commonly utilized inorganic materials as the scattering centers to achieve white color, which, however, lacks the ability to switch the optical properties. While hydrogels capable of scattering light are utilized in applications such as smart windows, their reflection properties have remained limited due to the low refractive index contrast between the polymer and water. As a result, thick layers in the millimeter range are often required to achieve reasonable whiteness. Here a hydrogel consisting of a temperature‐responsive poly( N ‐isopropylacrylamide) (PNIPAm) and chemically modified agarose used as a chemical macro‐crosslinker is presented. The hydrogel exhibits high whiteness at temperatures above the phase transition (≈31 °C). The reflectance at 800 nm is four times as high as for standard PNIPAm, and a change in transmittance can be induced by laser pulses as short as 30 ms. The macro‐crosslinked structure of this hydrogel provides superior reflectance at a lower thickness compared to reported hydrogel systems, enabling a variety of potential applications including smart windows, responsive displays, optical switches, and camouflage.
@article{eklund_bright_2023, title = {Bright and {Switchable} {Whiteness} in {Macro}‐{Crosslinked} {Hydrogels}}, issn = {2195-1071, 2195-1071}, url = {https://onlinelibrary.wiley.com/doi/10.1002/adom.202302487}, doi = {10.1002/adom.202302487}, abstract = {Abstract Bright white color is often achieved in nature by the combination of polydisperse scattering structures and high refractive index contrast between the scatterer and the surrounding medium. Similarly, synthetic systems have commonly utilized inorganic materials as the scattering centers to achieve white color, which, however, lacks the ability to switch the optical properties. While hydrogels capable of scattering light are utilized in applications such as smart windows, their reflection properties have remained limited due to the low refractive index contrast between the polymer and water. As a result, thick layers in the millimeter range are often required to achieve reasonable whiteness. Here a hydrogel consisting of a temperature‐responsive poly( N ‐isopropylacrylamide) (PNIPAm) and chemically modified agarose used as a chemical macro‐crosslinker is presented. The hydrogel exhibits high whiteness at temperatures above the phase transition (≈31 °C). The reflectance at 800 nm is four times as high as for standard PNIPAm, and a change in transmittance can be induced by laser pulses as short as 30 ms. The macro‐crosslinked structure of this hydrogel provides superior reflectance at a lower thickness compared to reported hydrogel systems, enabling a variety of potential applications including smart windows, responsive displays, optical switches, and camouflage.}, language = {en}, urldate = {2024-03-05}, journal = {Advanced Optical Materials}, author = {Eklund, Amanda and Hu, Shanming and Fang, Yuhuang and Savolainen, Henri and Pi, Haotian and Zeng, Hao and Priimagi, Arri and Ikkala, Olli and Zhang, Hang}, month = dec, year = {2023}, pages = {2302487}, file = {Full Text:files/913/Eklund et al. - 2023 - Bright and Switchable Whiteness in Macro‐Crosslink.pdf:application/pdf}, } - H. Guo, C. Liang, T. Ruoko, H. Meteling, B. Peng, H. Zeng, and A. Priimagi, “Programmable and Self‐Healable Liquid Crystal Elastomer Actuators Based on Halogen Bonding,” Angewandte Chemie International Edition, vol. 62, iss. 43, p. e202309402, 2023. doi:10.1002/anie.202309402
[BibTeX] [Abstract] [Download PDF]
Abstract Shape‐changing polymeric materials have gained significant attention in the field of bioinspired soft robotics. However, challenges remain in versatilizing the shape‐morphing process to suit different tasks and environments, and in designing systems that combine reversible actuation and self‐healing ability. Here, we report halogen‐bonded liquid crystal elastomers (LCEs) that can be arbitrarily shape‐programmed and that self‐heal under mild thermal or photothermal stimulation. We incorporate halogen‐bond‐donating diiodotetrafluorobenzene molecules as dynamic supramolecular crosslinks into the LCEs and show that these relatively weak crosslinks are pertinent for their mechanical programming and self‐healing. Utilizing the halogen‐bonded LCEs, we demonstrate proof‐of‐concept soft robotic motions such as crawling and rolling with programmed velocities. Our results showcase halogen bonding as a promising, yet unexplored tool for the preparation of smart supramolecular constructs for the development of advanced soft actuators.
@article{guo_programmable_2023, title = {Programmable and {Self}‐{Healable} {Liquid} {Crystal} {Elastomer} {Actuators} {Based} on {Halogen} {Bonding}}, volume = {62}, issn = {1433-7851, 1521-3773}, url = {https://onlinelibrary.wiley.com/doi/10.1002/anie.202309402}, doi = {10.1002/anie.202309402}, abstract = {Abstract Shape‐changing polymeric materials have gained significant attention in the field of bioinspired soft robotics. However, challenges remain in versatilizing the shape‐morphing process to suit different tasks and environments, and in designing systems that combine reversible actuation and self‐healing ability. Here, we report halogen‐bonded liquid crystal elastomers (LCEs) that can be arbitrarily shape‐programmed and that self‐heal under mild thermal or photothermal stimulation. We incorporate halogen‐bond‐donating diiodotetrafluorobenzene molecules as dynamic supramolecular crosslinks into the LCEs and show that these relatively weak crosslinks are pertinent for their mechanical programming and self‐healing. Utilizing the halogen‐bonded LCEs, we demonstrate proof‐of‐concept soft robotic motions such as crawling and rolling with programmed velocities. Our results showcase halogen bonding as a promising, yet unexplored tool for the preparation of smart supramolecular constructs for the development of advanced soft actuators.}, language = {en}, number = {43}, urldate = {2024-03-05}, journal = {Angewandte Chemie International Edition}, author = {Guo, Hongshuang and Liang, Chen and Ruoko, Tero‐Petri and Meteling, Henning and Peng, Bo and Zeng, Hao and Priimagi, Arri}, month = oct, year = {2023}, pages = {e202309402}, file = {Full Text:files/906/Guo et al. - 2023 - Programmable and Self‐Healable Liquid Crystal Elas.pdf:application/pdf}, } - J. Gemen, J. R. Church, T. Ruoko, N. Durandin, M. J. Białek, M. Weißenfels, M. Feller, M. Kazes, M. Odaybat, V. A. Borin, R. Kalepu, Y. Diskin-Posner, D. Oron, M. J. Fuchter, A. Priimagi, I. Schapiro, and R. Klajn, “Disequilibrating azobenzenes by visible-light sensitization under confinement,” Science, vol. 381, iss. 6664, pp. 1357-1363, 2023. doi:10.1126/science.adh9059
[BibTeX] [Abstract] [Download PDF]
Photoisomerization of azobenzenes from their stable E isomer to the metastable Z state is the basis of numerous applications of these molecules. However, this reaction typically requires ultraviolet light, which limits applicability. In this study, we introduce disequilibration by sensitization under confinement (DESC), a supramolecular approach to induce the E -to- Z isomerization by using light of a desired color, including red. DESC relies on a combination of a macrocyclic host and a photosensitizer, which act together to selectively bind and sensitize E -azobenzenes for isomerization. The Z isomer lacks strong affinity for and is expelled from the host, which can then convert additional E- azobenzenes to the Z state. In this way, the host–photosensitizer complex converts photon energy into chemical energy in the form of out-of-equilibrium photostationary states, including ones that cannot be accessed through direct photoexcitation. , Editor’s summary Chemists often strive to push reactions metaphorically uphill toward less energetically favorable products. The challenge is to keep those products from rolling right back down. Gemen et al . report a clever tactic for twisting azobenzene into its higher-energy Z conformation. Specifically, they lured the more stable E isomer into a supramolecular host, along with a photosensitizer. When visible light injects energy to induce the twist, the Z isomer no longer fits in the cavity, so it gets pushed out before more light can twist it back. —Jake S. Yeston , Spatial constraints in a supramolecular host selectively convert azobenzenes to their metastable state under visible light.
@article{gemen_disequilibrating_2023, title = {Disequilibrating azobenzenes by visible-light sensitization under confinement}, volume = {381}, issn = {0036-8075, 1095-9203}, url = {https://www.science.org/doi/10.1126/science.adh9059}, doi = {10.1126/science.adh9059}, abstract = {Photoisomerization of azobenzenes from their stable E isomer to the metastable Z state is the basis of numerous applications of these molecules. However, this reaction typically requires ultraviolet light, which limits applicability. In this study, we introduce disequilibration by sensitization under confinement (DESC), a supramolecular approach to induce the E -to- Z isomerization by using light of a desired color, including red. DESC relies on a combination of a macrocyclic host and a photosensitizer, which act together to selectively bind and sensitize E -azobenzenes for isomerization. The Z isomer lacks strong affinity for and is expelled from the host, which can then convert additional E- azobenzenes to the Z state. In this way, the host–photosensitizer complex converts photon energy into chemical energy in the form of out-of-equilibrium photostationary states, including ones that cannot be accessed through direct photoexcitation. , Editor’s summary Chemists often strive to push reactions metaphorically uphill toward less energetically favorable products. The challenge is to keep those products from rolling right back down. Gemen et al . report a clever tactic for twisting azobenzene into its higher-energy Z conformation. Specifically, they lured the more stable E isomer into a supramolecular host, along with a photosensitizer. When visible light injects energy to induce the twist, the Z isomer no longer fits in the cavity, so it gets pushed out before more light can twist it back. —Jake S. Yeston , Spatial constraints in a supramolecular host selectively convert azobenzenes to their metastable state under visible light.}, language = {en}, number = {6664}, urldate = {2024-03-05}, journal = {Science}, author = {Gemen, Julius and Church, Jonathan R. and Ruoko, Tero-Petri and Durandin, Nikita and Białek, Michał J. and Weißenfels, Maren and Feller, Moran and Kazes, Miri and Odaybat, Magdalena and Borin, Veniamin A. and Kalepu, Rishir and Diskin-Posner, Yael and Oron, Dan and Fuchter, Matthew J. and Priimagi, Arri and Schapiro, Igor and Klajn, Rafal}, month = sep, year = {2023}, pages = {1357--1363}, } - N. P. Pinchin, H. Guo, H. Meteling, Z. Deng, A. Priimagi, and H. Shahsavan, “Liquid Crystal Networks Meet Water: It’s Complicated!,” Advanced Materials, p. 2303740, 2023. doi:10.1002/adma.202303740
[BibTeX] [Abstract] [Download PDF]
Abstract Soft robots are composed of compliant materials that facilitate high degrees of freedom, shape‐change adaptability, and safer interaction with humans. An attractive choice of material for soft robotics is crosslinked networks of liquid crystal polymers (LCNs), as they are responsive to a wide variety of external stimuli and capable of undergoing fast, programmable, complex shape morphing, which allows for their use in a wide range of soft robotic applications. However, unlike hydrogels, another popular material in soft robotics, LCNs have limited applicability in flooded or aquatic environments. This can be attributed not only to the poor efficiency of common LCN actuation methods underwater but also to the complicated relationship between LCNs and water. In this review, the relationship between water and LCNs is elaborated and the existing body of literature is surveyed where LCNs, both hygroscopic and non‐hygroscopic, are utilized in aquatic soft robotic applications. Then the challenges LCNs face in widespread adaptation to aquatic soft robotic applications are discussed and, finally, possible paths forward for their successful use in aquatic environments are envisaged.
@article{pinchin_liquid_2023, title = {Liquid {Crystal} {Networks} {Meet} {Water}: {It}'s {Complicated}!}, issn = {0935-9648, 1521-4095}, shorttitle = {Liquid {Crystal} {Networks} {Meet} {Water}}, url = {https://onlinelibrary.wiley.com/doi/10.1002/adma.202303740}, doi = {10.1002/adma.202303740}, abstract = {Abstract Soft robots are composed of compliant materials that facilitate high degrees of freedom, shape‐change adaptability, and safer interaction with humans. An attractive choice of material for soft robotics is crosslinked networks of liquid crystal polymers (LCNs), as they are responsive to a wide variety of external stimuli and capable of undergoing fast, programmable, complex shape morphing, which allows for their use in a wide range of soft robotic applications. However, unlike hydrogels, another popular material in soft robotics, LCNs have limited applicability in flooded or aquatic environments. This can be attributed not only to the poor efficiency of common LCN actuation methods underwater but also to the complicated relationship between LCNs and water. In this review, the relationship between water and LCNs is elaborated and the existing body of literature is surveyed where LCNs, both hygroscopic and non‐hygroscopic, are utilized in aquatic soft robotic applications. Then the challenges LCNs face in widespread adaptation to aquatic soft robotic applications are discussed and, finally, possible paths forward for their successful use in aquatic environments are envisaged.}, language = {en}, urldate = {2024-03-05}, journal = {Advanced Materials}, author = {Pinchin, Natalie P. and Guo, Hongshuang and Meteling, Henning and Deng, Zixuan and Priimagi, Arri and Shahsavan, Hamed}, month = sep, year = {2023}, pages = {2303740}, file = {Full Text:files/901/Pinchin et al. - 2023 - Liquid Crystal Networks Meet Water It's Complicat.pdf:application/pdf}, } - M. Paatelainen, M. Lahikainen, A. Berdin, K. Kuntze, W. M. Nau, Nonappa, and A. Priimagi, “Hydrogel Lasers Via Supramolecular Host–Guest Complexation,” Advanced Optical Materials, vol. 11, iss. 15, p. 2300232, 2023. doi:10.1002/adom.202300232
[BibTeX] [Abstract] [Download PDF]
Abstract Supramolecular host–guest complexes are dynamic systems composed of typically macrocyclic host molecules encapsulating smaller guest molecules. One of their applications is the selective encapsulation of fluorescent dye molecules to tackle quenching and photobleaching in solution. When extended to solid matrices, the efficiency of dyes can be especially poor, limiting their use in fluorescence‐based applications. Here it is demonstrated that supramolecular host–guest complexation in a hydrogel network allows readily tunable hydrogel‐based lasers. Poly( N ‐isopropylacrylamide)‐based copolymer hydrogel is used with covalently linked Rhodamine B molecules. By controlled doping of cucurbit[7]uril as a host molecule in the hydrogel, it is shown that the fluorescent quantum yield increases from 17\% to 51\%, accompanied by 15‐fold enhancement in photostability. As proof of concept, a thin‐film distributed feedback hydrogel laser with wavelength tunability is fabricated. The results reveal a 30\% increase in slope efficiency in the presence of host molecules. These results, combined with the inherent stimuli‐response of hydrogels, enable new possibilities for affordable and small‐scale photonic devices capable of safely interacting with the environment in, for example, sensing applications.
@article{paatelainen_hydrogel_2023, title = {Hydrogel {Lasers} {Via} {Supramolecular} {Host}–{Guest} {Complexation}}, volume = {11}, issn = {2195-1071, 2195-1071}, url = {https://onlinelibrary.wiley.com/doi/10.1002/adom.202300232}, doi = {10.1002/adom.202300232}, abstract = {Abstract Supramolecular host–guest complexes are dynamic systems composed of typically macrocyclic host molecules encapsulating smaller guest molecules. One of their applications is the selective encapsulation of fluorescent dye molecules to tackle quenching and photobleaching in solution. When extended to solid matrices, the efficiency of dyes can be especially poor, limiting their use in fluorescence‐based applications. Here it is demonstrated that supramolecular host–guest complexation in a hydrogel network allows readily tunable hydrogel‐based lasers. Poly( N ‐isopropylacrylamide)‐based copolymer hydrogel is used with covalently linked Rhodamine B molecules. By controlled doping of cucurbit[7]uril as a host molecule in the hydrogel, it is shown that the fluorescent quantum yield increases from 17\% to 51\%, accompanied by 15‐fold enhancement in photostability. As proof of concept, a thin‐film distributed feedback hydrogel laser with wavelength tunability is fabricated. The results reveal a 30\% increase in slope efficiency in the presence of host molecules. These results, combined with the inherent stimuli‐response of hydrogels, enable new possibilities for affordable and small‐scale photonic devices capable of safely interacting with the environment in, for example, sensing applications.}, language = {en}, number = {15}, urldate = {2024-03-05}, journal = {Advanced Optical Materials}, author = {Paatelainen, Matias and Lahikainen, Markus and Berdin, Alex and Kuntze, Kim and Nau, Werner M. and {Nonappa} and Priimagi, Arri}, month = aug, year = {2023}, pages = {2300232}, file = {Full Text:files/899/Paatelainen et al. - 2023 - Hydrogel Lasers Via Supramolecular Host–Guest Comp.pdf:application/pdf}, } - Q. Liu, Y. Zhou, A. Shaukat, Z. Meng, D. Kyllönen, I. Seitz, D. Langerreiter, K. Kuntze, A. Priimagi, L. Zheng, and M. A. Kostiainen, “Optically Controlled Construction of Three‐Dimensional Protein Arrays,” Angewandte Chemie International Edition, vol. 62, iss. 28, p. e202303880, 2023. doi:10.1002/anie.202303880
[BibTeX] [Abstract] [Download PDF]
Abstract Protein crystallization is an important tool for structural biology and nanostructure preparation. Here, we report on kinetic pathway‐dependent protein crystals that are controlled by light. Photo‐responsive crystallites are obtained by complexing the model proteins with cationic azobenzene dyes. The crystalline state is readily switched to a dispersed phase under ultraviolet light and restored by subsequent visible‐light illumination. The switching can be reversibly repeated for multiple cycles without noticeable structure deterioration. Importantly, the photo‐treatment not only significantly increases the crystallinity, but creates crystallites at conditions where no ordered lattices are observed upon directly mixing the components. Further control over the azobenzene isomerization kinetics produces protein single crystals of up to ≈50 μm. This approach offers an intriguing method to fabricate metamaterials and study optically controlled crystallization.
@article{liu_optically_2023, title = {Optically {Controlled} {Construction} of {Three}‐{Dimensional} {Protein} {Arrays}}, volume = {62}, issn = {1433-7851, 1521-3773}, url = {https://onlinelibrary.wiley.com/doi/10.1002/anie.202303880}, doi = {10.1002/anie.202303880}, abstract = {Abstract Protein crystallization is an important tool for structural biology and nanostructure preparation. Here, we report on kinetic pathway‐dependent protein crystals that are controlled by light. Photo‐responsive crystallites are obtained by complexing the model proteins with cationic azobenzene dyes. The crystalline state is readily switched to a dispersed phase under ultraviolet light and restored by subsequent visible‐light illumination. The switching can be reversibly repeated for multiple cycles without noticeable structure deterioration. Importantly, the photo‐treatment not only significantly increases the crystallinity, but creates crystallites at conditions where no ordered lattices are observed upon directly mixing the components. Further control over the azobenzene isomerization kinetics produces protein single crystals of up to ≈50 μm. This approach offers an intriguing method to fabricate metamaterials and study optically controlled crystallization.}, language = {en}, number = {28}, urldate = {2024-03-05}, journal = {Angewandte Chemie International Edition}, author = {Liu, Qing and Zhou, Yu and Shaukat, Ahmed and Meng, Zhuojun and Kyllönen, Daniella and Seitz, Iris and Langerreiter, Daniel and Kuntze, Kim and Priimagi, Arri and Zheng, Lifei and Kostiainen, Mauri A.}, month = jul, year = {2023}, pages = {e202303880}, file = {Full Text:files/904/Liu et al. - 2023 - Optically Controlled Construction of Three‐Dimensi.pdf:application/pdf}, } - K. Dradrach, M. Zmyślony, Z. Deng, A. Priimagi, J. Biggins, and P. Wasylczyk, “Light-driven peristaltic pumping by an actuating splay-bend strip,” Nature Communications, vol. 14, iss. 1, p. 1877, 2023. doi:10.1038/s41467-023-37445-5
[BibTeX] [Abstract] [Download PDF]
Abstract Despite spectacular progress in microfluidics, small-scale liquid manipulation, with few exceptions, is still driven by external pumps and controlled by large-scale valves, increasing cost and size and limiting complexity. By contrast, optofluidics uses light to power, control and monitor liquid manipulation, potentially allowing for small, self-contained microfluidic devices. Here we demonstrate a soft light-propelled actuator made of liquid crystal gel that pumps microlitre volumes of water. The strip of actuating material serves as both a pump and a channel leading to an extremely simple microfluidic architecture that is both powered and controlled by light. The performance of the pump is well explained by a simple theoretical model in which the light-induced bending of the actuator competes with the liquid’s surface tension. The theory highlights that effective pumping requires a threshold light intensity and strip width. The proposed system explores the benefits of shifting the complexity of microfluidic systems from the fabricated device to spatio-temporal control over stimulating light patterns.
@article{dradrach_light-driven_2023, title = {Light-driven peristaltic pumping by an actuating splay-bend strip}, volume = {14}, issn = {2041-1723}, url = {https://www.nature.com/articles/s41467-023-37445-5}, doi = {10.1038/s41467-023-37445-5}, abstract = {Abstract Despite spectacular progress in microfluidics, small-scale liquid manipulation, with few exceptions, is still driven by external pumps and controlled by large-scale valves, increasing cost and size and limiting complexity. By contrast, optofluidics uses light to power, control and monitor liquid manipulation, potentially allowing for small, self-contained microfluidic devices. Here we demonstrate a soft light-propelled actuator made of liquid crystal gel that pumps microlitre volumes of water. The strip of actuating material serves as both a pump and a channel leading to an extremely simple microfluidic architecture that is both powered and controlled by light. The performance of the pump is well explained by a simple theoretical model in which the light-induced bending of the actuator competes with the liquid’s surface tension. The theory highlights that effective pumping requires a threshold light intensity and strip width. The proposed system explores the benefits of shifting the complexity of microfluidic systems from the fabricated device to spatio-temporal control over stimulating light patterns.}, language = {en}, number = {1}, urldate = {2024-03-05}, journal = {Nature Communications}, author = {Dradrach, Klaudia and Zmyślony, Michał and Deng, Zixuan and Priimagi, Arri and Biggins, John and Wasylczyk, Piotr}, month = apr, year = {2023}, pages = {1877}, file = {Full Text:files/902/Dradrach et al. - 2023 - Light-driven peristaltic pumping by an actuating s.pdf:application/pdf}, } - J. Yang, H. Zhang, A. Berdin, W. Hu, and H. Zeng, “Dandelion-Inspired, Wind-Dispersed Polymer-Assembly Controlled by Light,” Advanced Science, vol. n/a, iss. n/a, p. 2206752, 2023. doi:https://doi.org/10.1002/advs.202206752
[BibTeX] [Abstract] [Download PDF]
Abstract The rise of stimuli-responsive polymers has brought about a wealth of materials for small-scale, wirelessly controlled soft-bodied robots. Thinking beyond conventional robotic mobilities already demonstrated in synthetic systems, such as walking, swimming and jumping, flying in air by dispersal, gliding, or even hovering is a frontier yet to be explored by responsive materials. The demanding requirements for actuator’s performance, lightweight, and effective aerodynamic design underlie the grand challenges. Here, a soft matter-based porous structure capable of wind-assisted dispersal and lift-off/landing action under the control of a light beam is reported. The design is inspired by the seed of dandelion, resembling several biomimetic features, i.e., high porosity, lightweight, and separated vortex ring generation under a steady wind flow. Superior to its natural counterparts, this artificial seed is equipped with a soft actuator made of light-responsive liquid crystalline elastomer, which induces reversible opening/closing actions of the bristles upon visible light excitation. This shape-morphing enables manual tuning of terminal velocity, drag coefficient, and wind threshold for dispersal. Optically controlled wind-assisted lift-off and landing actions, and a light-induced local accumulation in descending structures are demonstrated. The results offer novel approaches for wirelessly controlled, miniatured devices that can passively navigate over a large aerial space.
@article{yang_dandelion-inspired_2023, title = {Dandelion-{Inspired}, {Wind}-{Dispersed} {Polymer}-{Assembly} {Controlled} by {Light}}, volume = {n/a}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/advs.202206752}, doi = {https://doi.org/10.1002/advs.202206752}, abstract = {Abstract The rise of stimuli-responsive polymers has brought about a wealth of materials for small-scale, wirelessly controlled soft-bodied robots. Thinking beyond conventional robotic mobilities already demonstrated in synthetic systems, such as walking, swimming and jumping, flying in air by dispersal, gliding, or even hovering is a frontier yet to be explored by responsive materials. The demanding requirements for actuator's performance, lightweight, and effective aerodynamic design underlie the grand challenges. Here, a soft matter-based porous structure capable of wind-assisted dispersal and lift-off/landing action under the control of a light beam is reported. The design is inspired by the seed of dandelion, resembling several biomimetic features, i.e., high porosity, lightweight, and separated vortex ring generation under a steady wind flow. Superior to its natural counterparts, this artificial seed is equipped with a soft actuator made of light-responsive liquid crystalline elastomer, which induces reversible opening/closing actions of the bristles upon visible light excitation. This shape-morphing enables manual tuning of terminal velocity, drag coefficient, and wind threshold for dispersal. Optically controlled wind-assisted lift-off and landing actions, and a light-induced local accumulation in descending structures are demonstrated. The results offer novel approaches for wirelessly controlled, miniatured devices that can passively navigate over a large aerial space.}, number = {n/a}, journal = {Advanced Science}, author = {Yang, Jianfeng and Zhang, Hang and Berdin, Alex and Hu, Wenqi and Zeng, Hao}, year = {2023}, note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.202206752}, pages = {2206752}, } - Z. Deng, H. Zhang, A. Priimagi, and H. Zeng, “Light-fueled Non-reciprocal Self-oscillators for Fluidic Transportation and Coupling,” Advanced Materials, vol. n/a, iss. n/a, p. 2209683, 2023. doi:https://doi.org/10.1002/adma.202209683
[BibTeX] [Abstract] [Download PDF]
Abstract Light-fueled self-oscillators based on soft actuating materials have triggered novel designs for small-scale robotic constructs that self-sustain their motion at non-equilibrium states and possess bioinspired autonomy and adaptive functions. However, the motions of most self-oscillators are reciprocal, which hinders their use in sophisticated biomimetic functions such as fluidic transportation. Here, we report an optically powered soft material strip that can perform non-reciprocal, self-sustained oscillation under water. The actuator is made of planar-aligned liquid crystal elastomer responding to visible light. Two laser beams from orthogonal directions allow for piecewise control over the strip deformation, enabling two self-shadowing effects coupled in one single material to yield non-reciprocal strokes. The non-reciprocity, stroke pattern and handedness are connected to the fluidic pumping efficiency, which can be controlled by the excitation conditions. We demonstrate autonomous microfluidic pumping in clockwise and anticlockwise directions, translocation of a micro-object by liquid propulsion, and coupling between two oscillating strips through liquid medium interaction. The results can offer new concepts for non-equilibrium soft actuators that can perform bio-like functions under water. This article is protected by copyright. All rights reserved
@article{deng_light-fueled_2023, title = {Light-fueled {Non}-reciprocal {Self}-oscillators for {Fluidic} {Transportation} and {Coupling}}, volume = {n/a}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.202209683}, doi = {https://doi.org/10.1002/adma.202209683}, abstract = {Abstract Light-fueled self-oscillators based on soft actuating materials have triggered novel designs for small-scale robotic constructs that self-sustain their motion at non-equilibrium states and possess bioinspired autonomy and adaptive functions. However, the motions of most self-oscillators are reciprocal, which hinders their use in sophisticated biomimetic functions such as fluidic transportation. Here, we report an optically powered soft material strip that can perform non-reciprocal, self-sustained oscillation under water. The actuator is made of planar-aligned liquid crystal elastomer responding to visible light. Two laser beams from orthogonal directions allow for piecewise control over the strip deformation, enabling two self-shadowing effects coupled in one single material to yield non-reciprocal strokes. The non-reciprocity, stroke pattern and handedness are connected to the fluidic pumping efficiency, which can be controlled by the excitation conditions. We demonstrate autonomous microfluidic pumping in clockwise and anticlockwise directions, translocation of a micro-object by liquid propulsion, and coupling between two oscillating strips through liquid medium interaction. The results can offer new concepts for non-equilibrium soft actuators that can perform bio-like functions under water. This article is protected by copyright. All rights reserved}, number = {n/a}, journal = {Advanced Materials}, author = {Deng, Zixuan and Zhang, Hang and Priimagi, Arri and Zeng, Hao}, year = {2023}, note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.202209683}, pages = {2209683}, } - K. Kuntze, J. Viljakka, M. Virkki, C. (. Huang, S. Hecht, and A. Priimagi, “Red-light photoswitching of indigos in polymer thin films,” Chemical Science, vol. 14, iss. 10, pp. 2482-2488, 2023. doi:10.1039/D2SC06790K
[BibTeX] [Abstract] [Download PDF]
Through simple synthetic modifications, the indigo dye becomes an efficient red-light photoswitch – now also in the solid state. , Through simple synthetic derivatisation, the parent indigo dye becomes a red-light E – Z photoswitch exhibiting negative photochromism and tuneable thermal isomerisation kinetics. These attributes make indigo derivatives extremely attractive for applications related to materials and living systems. However, there is a lack of knowledge in translating indigo photoswitching dynamics from solution to solid state – the environment crucial for most applications. Herein, we study the photoswitching performance of six structurally distinct indigo derivatives in five polymers of varying rigidity. Three key strategies are identified to enable efficient photoswitching under red (660 nm) light: (i) choosing a soft polymer matrix to minimise its resistance toward the isomerisation, (ii) creating free volume around the indigo molecules through synthetic modifications, and (iii) applying low dye loading (\textless1\% w/w) to inhibit aggregation. These strategies are shown to improve both photostationary state distributions and the thermal stability of the Z isomer. When all three strategies are implemented, the isomerisation performance (\textgreater80\% Z form in the photostationary state) is nearly identical to that in solution. These findings thus pave the way for designing new red-light photochromic materials based on indigos.
@article{kuntze_red-light_2023, title = {Red-light photoswitching of indigos in polymer thin films}, volume = {14}, issn = {2041-6520, 2041-6539}, url = {http://xlink.rsc.org/?DOI=D2SC06790K}, doi = {10.1039/D2SC06790K}, abstract = {Through simple synthetic modifications, the indigo dye becomes an efficient red-light photoswitch – now also in the solid state. , Through simple synthetic derivatisation, the parent indigo dye becomes a red-light E – Z photoswitch exhibiting negative photochromism and tuneable thermal isomerisation kinetics. These attributes make indigo derivatives extremely attractive for applications related to materials and living systems. However, there is a lack of knowledge in translating indigo photoswitching dynamics from solution to solid state – the environment crucial for most applications. Herein, we study the photoswitching performance of six structurally distinct indigo derivatives in five polymers of varying rigidity. Three key strategies are identified to enable efficient photoswitching under red (660 nm) light: (i) choosing a soft polymer matrix to minimise its resistance toward the isomerisation, (ii) creating free volume around the indigo molecules through synthetic modifications, and (iii) applying low dye loading ({\textless}1\% w/w) to inhibit aggregation. These strategies are shown to improve both photostationary state distributions and the thermal stability of the Z isomer. When all three strategies are implemented, the isomerisation performance ({\textgreater}80\% Z form in the photostationary state) is nearly identical to that in solution. These findings thus pave the way for designing new red-light photochromic materials based on indigos.}, language = {en}, number = {10}, urldate = {2024-03-05}, journal = {Chemical Science}, author = {Kuntze, Kim and Viljakka, Jani and Virkki, Matti and Huang, Chung-Yang (Dennis) and Hecht, Stefan and Priimagi, Arri}, year = {2023}, pages = {2482--2488}, file = {Full Text:files/891/Kuntze et al. - 2023 - Red-light photoswitching of indigos in polymer thi.pdf:application/pdf}, } - K. Kuntze, D. R. S. Pooler, M. Di Donato, M. F. Hilbers, P. Van Der Meulen, W. J. Buma, A. Priimagi, B. L. Feringa, and S. Crespi, “A visible-light-driven molecular motor based on barbituric acid,” Chemical Science, vol. 14, iss. 32, pp. 8458-8465, 2023. doi:10.1039/D3SC03090C
[BibTeX] [Abstract] [Download PDF]
Yeehaw! The rotation of a visible-light-driven molecular motor based on barbituric acid is tamed by a hydrogen bonding “lasso” mechanism between its serendipitously-formed tertiary hydroxy stereocentre and its lower half carbonyl groups. , We present a class of visible-light-driven molecular motors based on barbituric acid. Due to a serendipitous reactivity we observed during their synthesis, these motors possess a tertiary stereogenic centre on the upper half, characterised by a hydroxy group. Using a combination of femto- and nanosecond transient absorption spectroscopy, molecular dynamics simulations and low-temperature 1 H NMR experiments we found that these motors operate similarly to push–pull second-generation overcrowded alkene-based molecular motors. Interestingly, the hydroxy group at the stereocentre enables a hydrogen bond with the carbonyl groups of the barbituric acid lower half, which drives a sub-picosecond excited-state isomerisation, as observed spectroscopically. Computational simulations predict an excited state “lasso” mechanism where the intramolecular hydrogen bond pulls the molecule towards the formation of the metastable state, with a high predicted quantum yield of isomerisation (68\%) in gas phase.
@article{kuntze_visible-light-driven_2023, title = {A visible-light-driven molecular motor based on barbituric acid}, volume = {14}, issn = {2041-6520, 2041-6539}, url = {http://xlink.rsc.org/?DOI=D3SC03090C}, doi = {10.1039/D3SC03090C}, abstract = {Yeehaw! The rotation of a visible-light-driven molecular motor based on barbituric acid is tamed by a hydrogen bonding “lasso” mechanism between its serendipitously-formed tertiary hydroxy stereocentre and its lower half carbonyl groups. , We present a class of visible-light-driven molecular motors based on barbituric acid. Due to a serendipitous reactivity we observed during their synthesis, these motors possess a tertiary stereogenic centre on the upper half, characterised by a hydroxy group. Using a combination of femto- and nanosecond transient absorption spectroscopy, molecular dynamics simulations and low-temperature 1 H NMR experiments we found that these motors operate similarly to push–pull second-generation overcrowded alkene-based molecular motors. Interestingly, the hydroxy group at the stereocentre enables a hydrogen bond with the carbonyl groups of the barbituric acid lower half, which drives a sub-picosecond excited-state isomerisation, as observed spectroscopically. Computational simulations predict an excited state “lasso” mechanism where the intramolecular hydrogen bond pulls the molecule towards the formation of the metastable state, with a high predicted quantum yield of isomerisation (68\%) in gas phase.}, language = {en}, number = {32}, urldate = {2024-03-05}, journal = {Chemical Science}, author = {Kuntze, Kim and Pooler, Daisy R. S. and Di Donato, Mariangela and Hilbers, Michiel F. and Van Der Meulen, Pieter and Buma, Wybren Jan and Priimagi, Arri and Feringa, Ben L. and Crespi, Stefano}, year = {2023}, pages = {8458--8465}, file = {Full Text:files/893/Kuntze et al. - 2023 - A visible-light-driven molecular motor based on ba.pdf:application/pdf}, }
2022
- H. Guo, R. Puttreddy, T. Salminen, A. Lends, K. Jaudzems, H. Zeng, and A. Priimagi, “Halogen-bonded shape memory polymers,” Nature Communications, vol. 13, iss. 1, p. 7436, 2022. doi:10.1038/s41467-022-34962-7
[BibTeX] [Abstract] [Download PDF]
Halogen bonding (XB), a non-covalent interaction between an electron-deficient halogen atom and a Lewis base, is widely adopted in organic synthesis and supramolecular crystal engineering. However, the roadmap towards materials applications is hindered by the challenges in harnessing this relatively weak intermolecular interaction to devise human-commanded stimuli-responsive soft materials. Here, we report a liquid crystalline network comprising permanent covalent crosslinks and dynamic halogen bond crosslinks, which possess reversible thermo-responsive shape memory behaviour. Our findings suggest that I···N halogen bond, a paradigmatic motif in crystal engineering studies, enables temporary shape fixation at room temperature and subsequent shape recovery in response to human body temperature. We demonstrate versatile shape programming of the halogen-bonded polymer networks through human-hand operation and propose a micro-robotic injection model for complex 1D to 3D shape morphing in aqueous media at 37 \textbackslash,$^\textrm\textbackslashcirc$C. Through systematic structure-property-performance studies, we show the necessity of the I···N crosslinks in driving the shape memory effect. The halogen-bonded shape memory polymers expand the toolbox for the preparation of smart supramolecular constructs with tailored mechanical properties and thermoresponsive behaviour, for the needs of, e.g., future medical devices.
@article{guo_halogen-bonded_2022, title = {Halogen-bonded shape memory polymers}, volume = {13}, url = {https://doi.org/10.1038/s41467-022-34962-7}, doi = {10.1038/s41467-022-34962-7}, abstract = {Halogen bonding (XB), a non-covalent interaction between an electron-deficient halogen atom and a Lewis base, is widely adopted in organic synthesis and supramolecular crystal engineering. However, the roadmap towards materials applications is hindered by the challenges in harnessing this relatively weak intermolecular interaction to devise human-commanded stimuli-responsive soft materials. Here, we report a liquid crystalline network comprising permanent covalent crosslinks and dynamic halogen bond crosslinks, which possess reversible thermo-responsive shape memory behaviour. Our findings suggest that I···N halogen bond, a paradigmatic motif in crystal engineering studies, enables temporary shape fixation at room temperature and subsequent shape recovery in response to human body temperature. We demonstrate versatile shape programming of the halogen-bonded polymer networks through human-hand operation and propose a micro-robotic injection model for complex 1D to 3D shape morphing in aqueous media at 37 {\textbackslash},$^{\textrm{{\textbackslash}circ}}$C. Through systematic structure-property-performance studies, we show the necessity of the I···N crosslinks in driving the shape memory effect. The halogen-bonded shape memory polymers expand the toolbox for the preparation of smart supramolecular constructs with tailored mechanical properties and thermoresponsive behaviour, for the needs of, e.g., future medical devices.}, number = {1}, journal = {Nature Communications}, author = {Guo, Hongshuang and Puttreddy, Rakesh and Salminen, Turkka and Lends, Alons and Jaudzems, Kristaps and Zeng, Hao and Priimagi, Arri}, month = dec, year = {2022}, note = {ISBN: 2041-1723}, pages = {7436}, } - H. Zhang, H. Zeng, A. Eklund, H. Guo, A. Priimagi, and O. Ikkala, “Feedback-controlled hydrogels with homeostatic oscillations and dissipative signal transduction,” Nature Nanotechnology, vol. 17, iss. 12, pp. 1303-1310, 2022. doi:10.1038/s41565-022-01241-x
[BibTeX] [Abstract] [Download PDF]
Driving systems out of equilibrium under feedback control is characteristic for living systems, where homeostasis and dissipative signal transduction facilitate complex responses. This feature not only inspires dissipative dynamic functionalities in synthetic systems but also poses great challenges in designing novel pathways. Here we report feedback-controlled systems comprising two coupled hydrogels driven by constant light, where the system can be tuned to undergo stable homeostatic self-oscillations or damped steady states of temperature. We demonstrate that stable temperature oscillations can be utilized for dynamic colours and cargo transport, whereas damped steady states enable signal transduction pathways. Here mechanical triggers cause temperature changes that lead to responses such as bending motions inspired by the single-touch mechanoresponse in Mimosa pudica and the frequency-gated snapping motion inspired by the plant arithmetic in the Venus flytrap. The proposed concepts suggest generalizable feedback pathways for dissipative dynamic materials and interactive soft robotics.
@article{zhang_feedback-controlled_2022, title = {Feedback-controlled hydrogels with homeostatic oscillations and dissipative signal transduction}, volume = {17}, url = {https://doi.org/10.1038/s41565-022-01241-x}, doi = {10.1038/s41565-022-01241-x}, abstract = {Driving systems out of equilibrium under feedback control is characteristic for living systems, where homeostasis and dissipative signal transduction facilitate complex responses. This feature not only inspires dissipative dynamic functionalities in synthetic systems but also poses great challenges in designing novel pathways. Here we report feedback-controlled systems comprising two coupled hydrogels driven by constant light, where the system can be tuned to undergo stable homeostatic self-oscillations or damped steady states of temperature. We demonstrate that stable temperature oscillations can be utilized for dynamic colours and cargo transport, whereas damped steady states enable signal transduction pathways. Here mechanical triggers cause temperature changes that lead to responses such as bending motions inspired by the single-touch mechanoresponse in Mimosa pudica and the frequency-gated snapping motion inspired by the plant arithmetic in the Venus flytrap. The proposed concepts suggest generalizable feedback pathways for dissipative dynamic materials and interactive soft robotics.}, number = {12}, journal = {Nature Nanotechnology}, author = {Zhang, Hang and Zeng, Hao and Eklund, Amanda and Guo, Hongshuang and Priimagi, Arri and Ikkala, Olli}, month = dec, year = {2022}, note = {ISBN: 1748-3395}, pages = {1303--1310}, } - Q. Yang, H. Shahsavan, Z. Deng, H. Guo, H. Zhang, H. Liu, C. Zhang, A. Priimagi, X. Zhang, and H. Zeng, “Semi-Crystalline Rubber as a Light-Responsive, Programmable, Resilient Robotic Material,” Advanced Functional Materials, vol. 32, iss. 41, p. 2206939, 2022. doi:https://doi.org/10.1002/adfm.202206939
[BibTeX] [Abstract] [Download PDF]
Abstract Polymers with large and reversible light-induced deformation offer a plethora of opportunities for the wireless control of small-scale soft robots. However, their widespread adoption in real-world applications is hindered, mainly due to their intrinsic softening upon illumination. Such limitation has detrimental effects on the achievable stress, durability, and precise positional control of the soft actuators after multiple cycles of use. Here, a synthetic rubber from a polybutadiene-polyethylene copolymer is reported as a durable material for light-controlled soft robots. The rubber can be programmed to exhibit various deformation modes controlled by visible-to-infrared light through a photothermal effect. Semi-crystallinity of polyethylene within the rubbery network provides this material with a remarkable modulus at high temperatures (2.5 MPa at 100–140 \textbackslash,$^\textrm\textbackslashcirc$C), deformation repeatability (\textgreater90\%) and shape-recovery (\textgreater98\%) after 100 actuation cycles subject to loads ranging from 10 to 10 000 times of its body weight (1.4 kPa–1.4 MPa). Soft robotic applications are demonstrated, such as thermally-driven jumping and photo-driven cargo transport carrying up to 1200 times its own weight. The results expand the portfolio of materials in designing remotely-controlled, robust, and resilient soft robots working at small scales.
@article{yang_semi-crystalline_2022, title = {Semi-{Crystalline} {Rubber} as a {Light}-{Responsive}, {Programmable}, {Resilient} {Robotic} {Material}}, volume = {32}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.202206939}, doi = {https://doi.org/10.1002/adfm.202206939}, abstract = {Abstract Polymers with large and reversible light-induced deformation offer a plethora of opportunities for the wireless control of small-scale soft robots. However, their widespread adoption in real-world applications is hindered, mainly due to their intrinsic softening upon illumination. Such limitation has detrimental effects on the achievable stress, durability, and precise positional control of the soft actuators after multiple cycles of use. Here, a synthetic rubber from a polybutadiene-polyethylene copolymer is reported as a durable material for light-controlled soft robots. The rubber can be programmed to exhibit various deformation modes controlled by visible-to-infrared light through a photothermal effect. Semi-crystallinity of polyethylene within the rubbery network provides this material with a remarkable modulus at high temperatures (2.5 MPa at 100–140 {\textbackslash},$^{\textrm{{\textbackslash}circ}}$C), deformation repeatability ({\textgreater}90\%) and shape-recovery ({\textgreater}98\%) after 100 actuation cycles subject to loads ranging from 10 to 10 000 times of its body weight (1.4 kPa–1.4 MPa). Soft robotic applications are demonstrated, such as thermally-driven jumping and photo-driven cargo transport carrying up to 1200 times its own weight. The results expand the portfolio of materials in designing remotely-controlled, robust, and resilient soft robots working at small scales.}, number = {41}, journal = {Advanced Functional Materials}, author = {Yang, Qi and Shahsavan, Hamed and Deng, Zixuan and Guo, Hongshuang and Zhang, Hang and Liu, Heng and Zhang, Chunyu and Priimagi, Arri and Zhang, Xuequan and Zeng, Hao}, month = oct, year = {2022}, note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/adfm.202206939}, pages = {2206939}, } - C. Fedele, T. Ruoko, K. Kuntze, M. Virkki, and A. Priimagi, “New tricks and emerging applications from contemporary azobenzene research,” Photochemical & Photobiological Sciences, vol. 21, iss. 10, pp. 1719-1734, 2022. doi:10.1007/s43630-022-00262-8
[BibTeX] [Abstract] [Download PDF]
Azobenzenes have many faces. They are well-known as dyes, but most of all, azobenzenes are versatile photoswitchable molecules with powerful photochemical properties. Azobenzene photochemistry has been extensively studied for decades, but only relatively recently research has taken a steer towards applications, ranging from photonics and robotics to photobiology. In this perspective, after an overview of the recent trends in the molecular design of azobenzenes, we highlight three research areas where the azobenzene photoswitches may bring about promising technological innovations: chemical sensing, organic transistors, and cell signaling. Ingenious molecular designs have enabled versatile control of azobenzene photochemical properties, which has in turn facilitated the development of chemical sensors and photoswitchable organic transistors. Finally, the power of azobenzenes in biology is exemplified by vision restoration and photactivation of neural signaling. Although the selected examples reveal only some of the faces of azobenzenes, we expect the fields presented to develop rapidly in the near future, and that azobenzenes will play a central role in this development.
@article{fedele_new_2022, title = {New tricks and emerging applications from contemporary azobenzene research}, volume = {21}, url = {https://doi.org/10.1007/s43630-022-00262-8}, doi = {10.1007/s43630-022-00262-8}, abstract = {Azobenzenes have many faces. They are well-known as dyes, but most of all, azobenzenes are versatile photoswitchable molecules with powerful photochemical properties. Azobenzene photochemistry has been extensively studied for decades, but only relatively recently research has taken a steer towards applications, ranging from photonics and robotics to photobiology. In this perspective, after an overview of the recent trends in the molecular design of azobenzenes, we highlight three research areas where the azobenzene photoswitches may bring about promising technological innovations: chemical sensing, organic transistors, and cell signaling. Ingenious molecular designs have enabled versatile control of azobenzene photochemical properties, which has in turn facilitated the development of chemical sensors and photoswitchable organic transistors. Finally, the power of azobenzenes in biology is exemplified by vision restoration and photactivation of neural signaling. Although the selected examples reveal only some of the faces of azobenzenes, we expect the fields presented to develop rapidly in the near future, and that azobenzenes will play a central role in this development.}, number = {10}, journal = {Photochemical \& Photobiological Sciences}, author = {Fedele, Chiara and Ruoko, Tero-Petri and Kuntze, Kim and Virkki, Matti and Priimagi, Arri}, month = oct, year = {2022}, note = {ISBN: 1474-9092}, pages = {1719--1734}, } - A. Berdin, J. R. Gill, E. Perivolari, J. Kauppo, V. Apostolopoulos, G. D’Alessandro, M. Kaczmarek, and A. Priimagi, “Analysis of light diffraction by azobenzene-based photoalignment layers,” Opt. Express, vol. 30, iss. 16, pp. 29495-29506, 2022. doi:10.1364/OE.464278
[BibTeX] [Abstract] [Download PDF]
Photoalignment materials, such as the azobenzene-based PAAD series studied here, are becoming increasingly important in liquid crystal-based optical devices and displays. Yet their properties and, in particular, their response to light, are still not fully understood. We investigate, experimentally and theoretically, the photoinduced birefringence, the order parameter and the formation of surface relief gratings, as well as the diffraction caused by them. We show that some of the azobenzene PAAD materials are suitable for the formation of surface relief gratings with high modulation depth, while others exhibit strong photoinduced birefringence. The two effects are inversely correlated: the stronger the surface relief grating is, the weaker is photoinduced birefringence. Analytical formulas based on the Raman-Nath approximation and numerical simulations of Maxwell’s equations are used to quantify the diffraction caused by the induced diffraction gratings, showing excellent agreement between theory and experiment.
@article{berdin_analysis_2022, title = {Analysis of light diffraction by azobenzene-based photoalignment layers}, volume = {30}, url = {https://opg.optica.org/oe/abstract.cfm?URI=oe-30-16-29495}, doi = {10.1364/OE.464278}, abstract = {Photoalignment materials, such as the azobenzene-based PAAD series studied here, are becoming increasingly important in liquid crystal-based optical devices and displays. Yet their properties and, in particular, their response to light, are still not fully understood. We investigate, experimentally and theoretically, the photoinduced birefringence, the order parameter and the formation of surface relief gratings, as well as the diffraction caused by them. We show that some of the azobenzene PAAD materials are suitable for the formation of surface relief gratings with high modulation depth, while others exhibit strong photoinduced birefringence. The two effects are inversely correlated: the stronger the surface relief grating is, the weaker is photoinduced birefringence. Analytical formulas based on the Raman-Nath approximation and numerical simulations of Maxwell's equations are used to quantify the diffraction caused by the induced diffraction gratings, showing excellent agreement between theory and experiment.}, number = {16}, journal = {Opt. Express}, author = {Berdin, Alex and Gill, Jordan R. and Perivolari, Eleni and Kauppo, Joel and Apostolopoulos, Vasilis and D'Alessandro, Giampaolo and Kaczmarek, Malgosia and Priimagi, Arri}, month = aug, year = {2022}, note = {Publisher: Optica Publishing Group}, pages = {29495--29506}, } - D. Ghindani, I. Issah, S. Chervinskii, M. Lahikainen, K. Kuntze, A. Priimagi, and H. Caglayan, “Humidity-Controlled Tunable Emission in a Dye-Incorporated Metal–Hydrogel–Metal Cavity,” ACS Photonics, vol. 9, iss. 7, pp. 2287-2294, 2022. doi:10.1021/acsphotonics.2c00202
[BibTeX] [Download PDF]@article{ghindani_humidity-controlled_2022, title = {Humidity-{Controlled} {Tunable} {Emission} in a {Dye}-{Incorporated} {Metal}–{Hydrogel}–{Metal} {Cavity}}, volume = {9}, url = {https://doi.org/10.1021/acsphotonics.2c00202}, doi = {10.1021/acsphotonics.2c00202}, number = {7}, journal = {ACS Photonics}, author = {Ghindani, Dipa and Issah, Ibrahim and Chervinskii, Semyon and Lahikainen, Markus and Kuntze, Kim and Priimagi, Arri and Caglayan, Humeyra}, month = jun, year = {2022}, note = {\_eprint: https://doi.org/10.1021/acsphotonics.2c00202}, pages = {2287--2294}, } - H. Guo, A. Priimagi, and H. Zeng, “Optically Controlled Latching and Launching in Soft Actuators,” Advanced Functional Materials, vol. 32, iss. 17, p. 2108919, 2022. doi:https://doi.org/10.1002/adfm.202108919
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Abstract Snapping is an abrupt reaction, in which mechanical instability allows the structure to rapidly switch from one stabilized form to another. Snapping is attained through a sudden release of prestored elastic energy. It is perfected by natural species to enhance their preying, locomotion, and reproduction abilities. Recent developments in responsive materials research has allowed the realization of bioinspired snappers and rapidly moving soft robots triggered by external stimuli. However, it remains a grand challenge to reversibly and accurately control the snapping dynamics in terms of, e.g., onset timing and speed of motion. Here, a facile method to obtain light-fueled snapping-like launching with precise control over the elastic energy released and the onset timing is reported. The elastic energy is prestored in a light-responsive liquid crystal elastomer actuator, and the launching event is dictated by releasing the energy through a photothermally induced crystal-to-liquid transition of a liquid-crystalline adhesive latch. The method provides manual control over the amount of prestored energy, motion speed upon multiple launching events, and enables demonstrations such as jumping and catapult motions in soft robots and concerted motions of multiple launchers. The results provide a practical solution for controlled fast motions in soft small-scale robotics.
@article{guo_optically_2022, title = {Optically {Controlled} {Latching} and {Launching} in {Soft} {Actuators}}, volume = {32}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.202108919}, doi = {https://doi.org/10.1002/adfm.202108919}, abstract = {Abstract Snapping is an abrupt reaction, in which mechanical instability allows the structure to rapidly switch from one stabilized form to another. Snapping is attained through a sudden release of prestored elastic energy. It is perfected by natural species to enhance their preying, locomotion, and reproduction abilities. Recent developments in responsive materials research has allowed the realization of bioinspired snappers and rapidly moving soft robots triggered by external stimuli. However, it remains a grand challenge to reversibly and accurately control the snapping dynamics in terms of, e.g., onset timing and speed of motion. Here, a facile method to obtain light-fueled snapping-like launching with precise control over the elastic energy released and the onset timing is reported. The elastic energy is prestored in a light-responsive liquid crystal elastomer actuator, and the launching event is dictated by releasing the energy through a photothermally induced crystal-to-liquid transition of a liquid-crystalline adhesive latch. The method provides manual control over the amount of prestored energy, motion speed upon multiple launching events, and enables demonstrations such as jumping and catapult motions in soft robots and concerted motions of multiple launchers. The results provide a practical solution for controlled fast motions in soft small-scale robotics.}, number = {17}, journal = {Advanced Functional Materials}, author = {Guo, Hongshuang and Priimagi, Arri and Zeng, Hao}, month = apr, year = {2022}, note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/adfm.202108919}, pages = {2108919}, } - H. Guo, H. Zeng, and A. Priimagi, “Optically controlled grasping-slipping robot moving on tubular surfaces,” Multifunctional Materials, vol. 5, iss. 2, p. 024001, 2022.
[BibTeX] [Abstract]
Stimuli-responsive polymers provide unmatched opportunities for remotely controlled soft robots navigating in complex environments. Many of the responsive-material-based soft robots can walk on open surfaces, with movement directionality dictated by the friction anisotropy at the robot-substrate interface. Translocation in one-dimensional space such as on a tubular surface is much more challenging due to the lack of efficient friction control strategies. Such strategies could in long term provide novel application prospects in, e.g. overhaul at high altitudes and robotic operation within confined environments. In this work, we realize a liquid-crystal-elastomer-based soft robot that can move on a tubular surface through optical control over the grasping force exerted on the surface. Photoactuation allows for remotely switched gripping and friction control which, together with cyclic body deformation, enables light-fueled climbing on tubular surfaces of glass, wood, metal, and plastic with various cross-sections. We demonstrate vertical climbing, moving obstacles along the path, and load-carrying ability (at least 3 × body weight). We believe our design offer new prospects for wirelessly driven soft micro-robotics in confined spacing.
@article{guo_optically_2022-1, title = {Optically controlled grasping-slipping robot moving on tubular surfaces}, volume = {5}, abstract = {Stimuli-responsive polymers provide unmatched opportunities for remotely controlled soft robots navigating in complex environments. Many of the responsive-material-based soft robots can walk on open surfaces, with movement directionality dictated by the friction anisotropy at the robot-substrate interface. Translocation in one-dimensional space such as on a tubular surface is much more challenging due to the lack of efficient friction control strategies. Such strategies could in long term provide novel application prospects in, e.g. overhaul at high altitudes and robotic operation within confined environments. In this work, we realize a liquid-crystal-elastomer-based soft robot that can move on a tubular surface through optical control over the grasping force exerted on the surface. Photoactuation allows for remotely switched gripping and friction control which, together with cyclic body deformation, enables light-fueled climbing on tubular surfaces of glass, wood, metal, and plastic with various cross-sections. We demonstrate vertical climbing, moving obstacles along the path, and load-carrying ability (at least 3 × body weight). We believe our design offer new prospects for wirelessly driven soft micro-robotics in confined spacing.}, number = {2}, journal = {Multifunctional Materials}, author = {Guo, Hongshuang and Zeng, Hao and Priimagi, Arri}, month = mar, year = {2022}, pages = {024001}, } - B. Audia, C. Fedele, C. M. Tone, G. Cipparrone, and A. Priimagi, “Surface Stability of Azobenzene-Based Thin Films in Aqueous Environment: Light-Controllable Underwater Blistering,” Advanced Materials Interfaces, vol. 9, iss. 9, p. 2102125, 2022. doi:https://doi.org/10.1002/admi.202102125
[BibTeX] [Abstract] [Download PDF]
Abstract Azobenzene-based light-responsive thin films are emerging as appealing candidates for smart cell-culture substrates. Their attraction lies in the fact that they can be reversibly photo-patterned, providing a route for dynamically mimicking the remodeling of the extracellular matrix. However, since the cells need to be cultured in aqueous environment, a key parameter in the layout of any biological application is the stability of the surface underwater. In this work, the authors perform a detailed investigation on the surface stability of azobenzene-based thin films in water and in a biologically relevant aqueous medium in which surface blistering occurs, as a result of water–material interaction. The phenomenon arises due to film delamination, and it can be prevented by changing the underlying substrate, by an additional coating layer, or by photo-induced control over the film permeability. It is also shown that the blister orientation can be controlled with polarized light. Furthermore, a simple model based on osmotic pressure is proposed to explain the blister formation. These findings provide a comprehensive overview of the interaction between water and the photo-responsive film surface, pertinent for engineering biomaterials with enhanced dynamic control over the cell–material interface.
@article{audia_surface_2022, title = {Surface {Stability} of {Azobenzene}-{Based} {Thin} {Films} in {Aqueous} {Environment}: {Light}-{Controllable} {Underwater} {Blistering}}, volume = {9}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/admi.202102125}, doi = {https://doi.org/10.1002/admi.202102125}, abstract = {Abstract Azobenzene-based light-responsive thin films are emerging as appealing candidates for smart cell-culture substrates. Their attraction lies in the fact that they can be reversibly photo-patterned, providing a route for dynamically mimicking the remodeling of the extracellular matrix. However, since the cells need to be cultured in aqueous environment, a key parameter in the layout of any biological application is the stability of the surface underwater. In this work, the authors perform a detailed investigation on the surface stability of azobenzene-based thin films in water and in a biologically relevant aqueous medium in which surface blistering occurs, as a result of water–material interaction. The phenomenon arises due to film delamination, and it can be prevented by changing the underlying substrate, by an additional coating layer, or by photo-induced control over the film permeability. It is also shown that the blister orientation can be controlled with polarized light. Furthermore, a simple model based on osmotic pressure is proposed to explain the blister formation. These findings provide a comprehensive overview of the interaction between water and the photo-responsive film surface, pertinent for engineering biomaterials with enhanced dynamic control over the cell–material interface.}, number = {9}, journal = {Advanced Materials Interfaces}, author = {Audia, Biagio and Fedele, Chiara and Tone, Caterina M. and Cipparrone, Gabriella and Priimagi, Arri}, month = mar, year = {2022}, note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/admi.202102125}, pages = {2102125}, } - M. Isomäki, C. Fedele, L. Kääriäinen, E. Mäntylä, S. Nymark, T. O. Ihalainen, and A. Priimagi, “Light-Responsive Bilayer Cell Culture Platform for Reversible Cell Guidance,” Small Science, vol. 2, iss. 3, p. 2100099, 2022. doi:https://doi.org/10.1002/smsc.202100099
[BibTeX] [Abstract] [Download PDF]
In vivo, cells are surrounded by a constantly changing microenvironment, which regulates many cell functions such as differentiation, migration, and cell death. Stimuli-responsive biomaterials aim to mimic this interaction between cells and extracellular matrix in vitro. However, reproducing dynamic signaling noninvasively without affecting the cell viability remains a challenge. Herein, a dynamic cell culturing platform consisting of a light-responsive azobenzene molecular glass film and a protective polydimethylsiloxane (PDMS) coating is developed. By tuning the PDMS layer thickness, surface relief gratings (SRGs) can be efficiently photoinscribed on the platform surface. The SRGs can also be erased with light in the presence of PDMS, i.e., the topography can be reversibly photomodulated. The inscribed SRGs can guide epithelial cell orientation along the topography. The erasure parameters are targeted toward cell culturing environment, enabling experiments with live cells. Finally, the photoresponsive platform is patterned with proteins by microcontact printing, allowing its biofunctionalization and the combination of microtopography and protein patterns. This study paves the way for using reconfigurable cell culture platforms for the dynamic control of cell–material interactions. The PDMS coating has potential to protect underneath material, broadening the spectrum of possible materials for dynamic cell culture platforms.
@article{isomaki_light-responsive_2022, title = {Light-{Responsive} {Bilayer} {Cell} {Culture} {Platform} for {Reversible} {Cell} {Guidance}}, volume = {2}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/smsc.202100099}, doi = {https://doi.org/10.1002/smsc.202100099}, abstract = {In vivo, cells are surrounded by a constantly changing microenvironment, which regulates many cell functions such as differentiation, migration, and cell death. Stimuli-responsive biomaterials aim to mimic this interaction between cells and extracellular matrix in vitro. However, reproducing dynamic signaling noninvasively without affecting the cell viability remains a challenge. Herein, a dynamic cell culturing platform consisting of a light-responsive azobenzene molecular glass film and a protective polydimethylsiloxane (PDMS) coating is developed. By tuning the PDMS layer thickness, surface relief gratings (SRGs) can be efficiently photoinscribed on the platform surface. The SRGs can also be erased with light in the presence of PDMS, i.e., the topography can be reversibly photomodulated. The inscribed SRGs can guide epithelial cell orientation along the topography. The erasure parameters are targeted toward cell culturing environment, enabling experiments with live cells. Finally, the photoresponsive platform is patterned with proteins by microcontact printing, allowing its biofunctionalization and the combination of microtopography and protein patterns. This study paves the way for using reconfigurable cell culture platforms for the dynamic control of cell–material interactions. The PDMS coating has potential to protect underneath material, broadening the spectrum of possible materials for dynamic cell culture platforms.}, number = {3}, journal = {Small Science}, author = {Isomäki, Mari and Fedele, Chiara and Kääriäinen, Lotta and Mäntylä, Elina and Nymark, Soile and Ihalainen, Teemu O. and Priimagi, Arri}, month = mar, year = {2022}, note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/smsc.202100099}, pages = {2100099}, } - K. Kuntze, J. Viljakka, E. Titov, Z. Ahmed, E. Kalenius, P. Saalfrank, and A. Priimagi, “Towards low-energy-light-driven bistable photoswitches: ortho-fluoroaminoazobenzenes,” Photochemical & Photobiological Sciences, vol. 21, iss. 2, pp. 159-173, 2022. doi:10.1007/s43630-021-00145-4
[BibTeX] [Abstract] [Download PDF]
Thermally stable photoswitches that are driven with low-energy light are rare, yet crucial for extending the applicability of photoresponsive molecules and materials towards, e.g., living systems. Combined ortho-fluorination and -amination couples high visible light absorptivity of o-aminoazobenzenes with the extraordinary bistability of o-fluoroazobenzenes. Herein, we report a library of easily accessible o-aminofluoroazobenzenes and establish structure–property relationships regarding spectral qualities, visible light isomerization efficiency and thermal stability of the cis-isomer with respect to the degree of o-substitution and choice of amino substituent. We rationalize the experimental results with quantum chemical calculations, revealing the nature of low-lying excited states and providing insight into thermal isomerization. The synthesized azobenzenes absorb at up to 600 nm and their thermal cis-lifetimes range from milliseconds to months. The most unique example can be driven from trans to cis with any wavelength from UV up to 595 nm, while still exhibiting a thermal cis-lifetime of 81 days.
@article{kuntze_towards_2022, title = {Towards low-energy-light-driven bistable photoswitches: ortho-fluoroaminoazobenzenes}, volume = {21}, url = {https://doi.org/10.1007/s43630-021-00145-4}, doi = {10.1007/s43630-021-00145-4}, abstract = {Thermally stable photoswitches that are driven with low-energy light are rare, yet crucial for extending the applicability of photoresponsive molecules and materials towards, e.g., living systems. Combined ortho-fluorination and -amination couples high visible light absorptivity of o-aminoazobenzenes with the extraordinary bistability of o-fluoroazobenzenes. Herein, we report a library of easily accessible o-aminofluoroazobenzenes and establish structure–property relationships regarding spectral qualities, visible light isomerization efficiency and thermal stability of the cis-isomer with respect to the degree of o-substitution and choice of amino substituent. We rationalize the experimental results with quantum chemical calculations, revealing the nature of low-lying excited states and providing insight into thermal isomerization. The synthesized azobenzenes absorb at up to 600 nm and their thermal cis-lifetimes range from milliseconds to months. The most unique example can be driven from trans to cis with any wavelength from UV up to 595 nm, while still exhibiting a thermal cis-lifetime of 81 days.}, number = {2}, journal = {Photochemical \& Photobiological Sciences}, author = {Kuntze, Kim and Viljakka, Jani and Titov, Evgenii and Ahmed, Zafar and Kalenius, Elina and Saalfrank, Peter and Priimagi, Arri}, month = feb, year = {2022}, note = {ISBN: 1474-9092}, pages = {159--173}, } - E. Taipale, N. A. Durandin, J. K. Salunke, N. R. Candeias, T. Ruoko, J. S. Ward, A. Priimagi, and K. Rissanen, “Protonation-induced fluorescence modulation of carbazole-based emitters,” Materials Advances, vol. 3, iss. 3, pp. 1703-1712, 2022. doi:10.1039/D1MA00438G
[BibTeX] [Abstract] [Download PDF]
The development of purely organic fluorescence emitters is of great importance for their low cost and high performance. Responding to this demand, carbazole is a promising emitter due to its extensive freedom for functionalisation, high thermal and chemical stability, as well as low cost. Herein, the effect of protonation on the fluorescence of various pyridine-functionalised carbazole-based bipolar host materials was studied both in solution and in the solid-state. The restriction of intramolecular rotation of the molecules upon protonation of the pyridyl-moiety together with easier planarization of the protonated acceptor and the donor moieties and relocalisation of the LUMO orbital on the protonated species was found to increase the fluorescence quantum yield from 16\% to 80\%. Additionally, in the solid-state, the J-type packing of the molecules further facilitated the increase in the fluorescence quantum yield from 1\% to 49\%. In both cases, the pronounced bathochromic spectral shift was observed indicating that the gap between the emissive state and the first triplet state of the molecules was diminished upon protonation. Therefore, implementing this strategy could further boost the development of future emitters.
@article{taipale_protonation-induced_2022, title = {Protonation-induced fluorescence modulation of carbazole-based emitters}, volume = {3}, url = {http://dx.doi.org/10.1039/D1MA00438G}, doi = {10.1039/D1MA00438G}, abstract = {The development of purely organic fluorescence emitters is of great importance for their low cost and high performance. Responding to this demand, carbazole is a promising emitter due to its extensive freedom for functionalisation, high thermal and chemical stability, as well as low cost. Herein, the effect of protonation on the fluorescence of various pyridine-functionalised carbazole-based bipolar host materials was studied both in solution and in the solid-state. The restriction of intramolecular rotation of the molecules upon protonation of the pyridyl-moiety together with easier planarization of the protonated acceptor and the donor moieties and relocalisation of the LUMO orbital on the protonated species was found to increase the fluorescence quantum yield from 16\% to 80\%. Additionally, in the solid-state, the J-type packing of the molecules further facilitated the increase in the fluorescence quantum yield from 1\% to 49\%. In both cases, the pronounced bathochromic spectral shift was observed indicating that the gap between the emissive state and the first triplet state of the molecules was diminished upon protonation. Therefore, implementing this strategy could further boost the development of future emitters.}, number = {3}, journal = {Materials Advances}, author = {Taipale, Essi and Durandin, Nikita A. and Salunke, Jagadish K. and Candeias, Nuno R. and Ruoko, Tero-Petri and Ward, Jas S. and Priimagi, Arri and Rissanen, Kari}, month = jan, year = {2022}, note = {Publisher: RSC}, pages = {1703--1712}, } - J. Liu, H. Zeng, M. Cheng, Z. Wang, J. Wang, M. Cen, D. Luo, A. Priimagi, and Y. J. Liu, “Photoelastic plasmonic metasurfaces with ultra-large near infrared spectral tuning,” Materials Horizons, vol. 9, iss. 3, pp. 942-951, 2022. doi:10.1039/D1MH01377G
[BibTeX] [Abstract] [Download PDF]
Metasurfaces, consisting of artificially fabricated sub-wavelength meta-atoms with pre-designable electromagnetic properties, provide novel opportunities to a variety of applications such as light detectors/sensors, local field imaging and optical displays. Currently, the tuning of most metasurfaces requires redesigning and reproducing the entire structure, rendering them ineligible for post-fabrication shape-morphing or spectral reconfigurability. Here, we report a photoelastic metasurface with an all-optical and reversible resonance tuning in the near infrared range. The photoelastic metasurface consists of hexagonal gold nanoarrays deposited on a deformable substrate made of a liquid crystalline network. Upon photo-actuation, the substrate deforms, causing the lattice to change and, as a result, the plasmon resonance to shift. The centre wavelength of the plasmon resonance exhibits an ultra-large spectral tuning of over 245 nm, from 1490 to 1245 nm, while the anisotropic deformability also endows light-switchable sensitivity in probing polarization. The proposed concept establishes a light-controlled soft platform that is of great potential for tunable/reconfigurable photonic devices, such as nano-filters, -couplers, -holograms, and displays with structural colors.
@article{liu_photoelastic_2022, title = {Photoelastic plasmonic metasurfaces with ultra-large near infrared spectral tuning}, volume = {9}, url = {http://dx.doi.org/10.1039/D1MH01377G}, doi = {10.1039/D1MH01377G}, abstract = {Metasurfaces, consisting of artificially fabricated sub-wavelength meta-atoms with pre-designable electromagnetic properties, provide novel opportunities to a variety of applications such as light detectors/sensors, local field imaging and optical displays. Currently, the tuning of most metasurfaces requires redesigning and reproducing the entire structure, rendering them ineligible for post-fabrication shape-morphing or spectral reconfigurability. Here, we report a photoelastic metasurface with an all-optical and reversible resonance tuning in the near infrared range. The photoelastic metasurface consists of hexagonal gold nanoarrays deposited on a deformable substrate made of a liquid crystalline network. Upon photo-actuation, the substrate deforms, causing the lattice to change and, as a result, the plasmon resonance to shift. The centre wavelength of the plasmon resonance exhibits an ultra-large spectral tuning of over 245 nm, from 1490 to 1245 nm, while the anisotropic deformability also endows light-switchable sensitivity in probing polarization. The proposed concept establishes a light-controlled soft platform that is of great potential for tunable/reconfigurable photonic devices, such as nano-filters, -couplers, -holograms, and displays with structural colors.}, number = {3}, journal = {Materials Horizons}, author = {Liu, Jianxun and Zeng, Hao and Cheng, Ming and Wang, Zhenming and Wang, Jiawei and Cen, Mengjia and Luo, Dan and Priimagi, Arri and Liu, Yan Jun}, month = jan, year = {2022}, note = {Publisher: The Royal Society of Chemistry}, pages = {942--951}, } - M. Cheng, H. Zeng, Y. Li, J. Liu, D. Luo, A. Priimagi, and Y. J. Liu, “Light-Fueled Polymer Film Capable of Directional Crawling, Friction-Controlled Climbing, and Self-Sustained Motion on a Human Hair,” Advanced Science, vol. 9, iss. 1, p. 2103090, 2022. doi:https://doi.org/10.1002/advs.202103090
[BibTeX] [Abstract] [Download PDF]
Abstract Recent efforts in stimuli-responsive soft materials have enabled wirelessly controlled actuation with increasing degrees of freedom, yielding miniature robots capable of various locomotion in open environments such as on a plane or inside fluids. However, grand challenges remain in harnessing photomechanical deformation to induce locomotion and control of friction during the movement, especially for robotic actuations within constrained spaces. Here, the authors report a centimeter-long polymer strip made of a liquid crystal network that is capable of versatile light-fueled motions along a human hair. The soft polymer robot can translocate directionally upon temporally modulated excitation and climb vertically through friction control with light. A self-oscillating strip is demonstrated to continuously translocate along the hair upon a constant light stimulus, and its gaiting is associated to the smoothness of the hair surface. The results offer new insights to small-scale photo-actuator, mechanical control, and automation in soft micro robotics.
@article{cheng_light-fueled_2022, title = {Light-{Fueled} {Polymer} {Film} {Capable} of {Directional} {Crawling}, {Friction}-{Controlled} {Climbing}, and {Self}-{Sustained} {Motion} on a {Human} {Hair}}, volume = {9}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/advs.202103090}, doi = {https://doi.org/10.1002/advs.202103090}, abstract = {Abstract Recent efforts in stimuli-responsive soft materials have enabled wirelessly controlled actuation with increasing degrees of freedom, yielding miniature robots capable of various locomotion in open environments such as on a plane or inside fluids. However, grand challenges remain in harnessing photomechanical deformation to induce locomotion and control of friction during the movement, especially for robotic actuations within constrained spaces. Here, the authors report a centimeter-long polymer strip made of a liquid crystal network that is capable of versatile light-fueled motions along a human hair. The soft polymer robot can translocate directionally upon temporally modulated excitation and climb vertically through friction control with light. A self-oscillating strip is demonstrated to continuously translocate along the hair upon a constant light stimulus, and its gaiting is associated to the smoothness of the hair surface. The results offer new insights to small-scale photo-actuator, mechanical control, and automation in soft micro robotics.}, number = {1}, journal = {Advanced Science}, author = {Cheng, Ming and Zeng, Hao and Li, Yifei and Liu, Jianxun and Luo, Dan and Priimagi, Arri and Liu, Yan Jun}, month = jan, year = {2022}, note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.202103090}, pages = {2103090}, }
2021
- K. Kuntze, J. Isokuortti, A. Siiskonen, N. Durandin, T. Laaksonen, and A. Priimagi, “Azobenzene Photoswitching with Near-Infrared Light Mediated by Molecular Oxygen,” The Journal of Physical Chemistry B, vol. 125, pp. 12568-12573, 2021. doi:https://doi.org/10.1021/acs.jpcb.1c08012
[BibTeX] [Abstract]
Efficient photoisomerization between the cis and the trans states of azobenzenes using low-energy light is desirable for a range of applications in, e.g., photobiology yet challenging to accomplish directly with modified azobenzenes. Herein, we utilize molecular iodine as a photocatalyst to induce indirect cis-to-trans isomerization of 4,4′-dimethoxyazobenzene with 770 nm near-infrared light, showing robustness during more than 1000 cycles in ambient conditions. Intriguingly, the catalysis is mediated by molecular oxygen, and we demonstrate that other singlet-oxygen-generating photosensitizers besides iodine, i.e., palladium phthalocyanine, catalyze the isomerization as well. Thus, we envision that the approach can be further improved by employing other catalysts with suitable photoelectrochemical properties. Further studies are needed to explore the applicability of the approach with other azobenzene derivatives.
@article{kuntze_azobenzene_2021, title = {Azobenzene {Photoswitching} with {Near}-{Infrared} {Light} {Mediated} by {Molecular} {Oxygen}}, volume = {125}, doi = {https://doi.org/10.1021/acs.jpcb.1c08012}, abstract = {Efficient photoisomerization between the cis and the trans states of azobenzenes using low-energy light is desirable for a range of applications in, e.g., photobiology yet challenging to accomplish directly with modified azobenzenes. Herein, we utilize molecular iodine as a photocatalyst to induce indirect cis-to-trans isomerization of 4,4′-dimethoxyazobenzene with 770 nm near-infrared light, showing robustness during more than 1000 cycles in ambient conditions. Intriguingly, the catalysis is mediated by molecular oxygen, and we demonstrate that other singlet-oxygen-generating photosensitizers besides iodine, i.e., palladium phthalocyanine, catalyze the isomerization as well. Thus, we envision that the approach can be further improved by employing other catalysts with suitable photoelectrochemical properties. Further studies are needed to explore the applicability of the approach with other azobenzene derivatives.}, journal = {The Journal of Physical Chemistry B}, author = {Kuntze, Kim and Isokuortti, Jussi and Siiskonen, Antti and Durandin, Nikita and Laaksonen, Timo and Priimagi, Arri}, month = nov, year = {2021}, pages = {12568--12573}, } - S. Chervinskii, I. Issah, M. Lahikainen, A. R. Rashed, K. Kuntze, A. Priimagi, and H. Caglayan, “Humidity- and Temperature-Tunable Metal–Hydrogel–Metal Reflective Filters,” ACS Applied Materials & Interfaces, vol. 13, pp. 50564-50572, 2021. doi:https://doi.org/10.1021/acsami.1c15616
[BibTeX] [Abstract]
A tunable reflectance filter based on a metal–hydrogel–metal structure responsive to humidity and temperature is reported. The filter employs a poly(N-isopropylacrylamide)–acrylamidobenzophenone (PNIPAm–BP) hydrogel as an insulator layer in the metal–insulator–metal (MIM) assembly. The optical resonance of the structure is tunable by water immersion across the visible and near-infrared range. Swelling/deswelling and the volume phase transition of the hydrogel allow continuous reversible humidity- and/or temperature-induced tuning of the optical resonance. This work paves the way toward low-cost large-area fabrication of actively tunable reversible photonic devices.
@article{chervinskii_humidity-_2021, title = {Humidity- and {Temperature}-{Tunable} {Metal}–{Hydrogel}–{Metal} {Reflective} {Filters}}, volume = {13}, doi = {https://doi.org/10.1021/acsami.1c15616}, abstract = {A tunable reflectance filter based on a metal–hydrogel–metal structure responsive to humidity and temperature is reported. The filter employs a poly(N-isopropylacrylamide)–acrylamidobenzophenone (PNIPAm–BP) hydrogel as an insulator layer in the metal–insulator–metal (MIM) assembly. The optical resonance of the structure is tunable by water immersion across the visible and near-infrared range. Swelling/deswelling and the volume phase transition of the hydrogel allow continuous reversible humidity- and/or temperature-induced tuning of the optical resonance. This work paves the way toward low-cost large-area fabrication of actively tunable reversible photonic devices.}, journal = {ACS Applied Materials \& Interfaces}, author = {Chervinskii, Semyon and Issah, Ibrahim and Lahikainen, Markus and Rashed, Alireza R. and Kuntze, Kim and Priimagi, Arri and Caglayan, Humeyra}, month = oct, year = {2021}, pages = {50564--50572}, } - S. Yang, J. D. Harris, A. Lambai, L. L. Jeliazkov, G. Mohanty, H. Zeng, A. Priimagi, and I. Aprahamian, “Multistage Reversible Tg Photomodulation and Hardening of Hydrazone-Containing Polymers,” Journal of the American Chemical Society, vol. 143, pp. 16348-16353, 2021. doi:https://doi.org/10.1021/jacs.1c07504
[BibTeX] [Abstract]
The glass transition temperature (Tg) of a series of polyacrylate- and polymethacrylate-based polymers having bistable hydrazone photoswitches as pendants increases upon photoisomerization. The ensuing photohardening of the polymeric network was corroborated using nanoindentation measurements. The bistability of the switch allowed us to lock-in and sustain multiple Tg values in the same polymeric material as a function of the hydrazone switch’s Z/E isomer ratio, even at elevated temperatures.
@article{yang_multistage_2021, title = {Multistage {Reversible} {Tg} {Photomodulation} and {Hardening} of {Hydrazone}-{Containing} {Polymers}}, volume = {143}, doi = {https://doi.org/10.1021/jacs.1c07504}, abstract = {The glass transition temperature (Tg) of a series of polyacrylate- and polymethacrylate-based polymers having bistable hydrazone photoswitches as pendants increases upon photoisomerization. The ensuing photohardening of the polymeric network was corroborated using nanoindentation measurements. The bistability of the switch allowed us to lock-in and sustain multiple Tg values in the same polymeric material as a function of the hydrazone switch's Z/E isomer ratio, even at elevated temperatures.}, journal = {Journal of the American Chemical Society}, author = {Yang, Sirun and Harris, Jared D. and Lambai, Aloshious and Jeliazkov, Laura L. and Mohanty, Gaurav and Zeng, Hao and Priimagi, Arri and Aprahamian, Ivan}, month = sep, year = {2021}, pages = {16348--16353}, } - L. Canil, J. Salunke, Q. Wang, M. Liu, H. Köbler, M. Flatken, L. Gregori, D. Meggiolaro, D. Ricciarelli, F. De Angelis, M. Stolterfoht, D. Neher, A. Priimagi, P. Vivo, and A. Abate, “Halogen-Bonded Hole-Transport Material Suppresses Charge Recombination and Enhances Stability of Perovskite Solar Cells,” Advanced Energy Materials, vol. 11, p. 2101553, 2021. doi:https://doi.org/10.1002/aenm.202101553
[BibTeX] [Abstract]
Interfaces play a crucial role in determining perovskite solar cells, (PSCs) performance and stability. It is therefore of great importance to constantly work toward improving their design. This study shows the advantages of using a hole-transport material (HTM) that can anchor to the perovskite surface through halogen bonding (XB). A halo-functional HTM (PFI) is compared to a reference HTM (PF), identical in optoelectronic properties and chemical structure but lacking the ability to form XB. The interaction between PFI and perovskite is supported by simulations and experiments. XB allows the HTM to create an ordered and homogenous layer on the perovskite surface, thus improving the perovskite/HTM interface and its energy level alignment. Thanks to the compact and ordered interface, PFI displays increased resistance to solvent exposure compared to its not-interacting counterpart. Moreover, PFI devices show suppressed nonradiative recombination and reduced hysteresis, with a Voc enhancement of ≥20 mV and a remarkable stability, retaining more than 90\% efficiency after 550 h of continuous maximum-power-point tracking. This work highlights the potential that XB can bring to the context of PSCs, paving the way for a new halo-functional design strategy for charge-transport layers, which tackles the challenges of charge transport and interface improvement simultaneously.
@article{canil_halogen-bonded_2021, title = {Halogen-{Bonded} {Hole}-{Transport} {Material} {Suppresses} {Charge} {Recombination} and {Enhances} {Stability} of {Perovskite} {Solar} {Cells}}, volume = {11}, doi = {https://doi.org/10.1002/aenm.202101553}, abstract = {Interfaces play a crucial role in determining perovskite solar cells, (PSCs) performance and stability. It is therefore of great importance to constantly work toward improving their design. This study shows the advantages of using a hole-transport material (HTM) that can anchor to the perovskite surface through halogen bonding (XB). A halo-functional HTM (PFI) is compared to a reference HTM (PF), identical in optoelectronic properties and chemical structure but lacking the ability to form XB. The interaction between PFI and perovskite is supported by simulations and experiments. XB allows the HTM to create an ordered and homogenous layer on the perovskite surface, thus improving the perovskite/HTM interface and its energy level alignment. Thanks to the compact and ordered interface, PFI displays increased resistance to solvent exposure compared to its not-interacting counterpart. Moreover, PFI devices show suppressed nonradiative recombination and reduced hysteresis, with a Voc enhancement of ≥20 mV and a remarkable stability, retaining more than 90\% efficiency after 550 h of continuous maximum-power-point tracking. This work highlights the potential that XB can bring to the context of PSCs, paving the way for a new halo-functional design strategy for charge-transport layers, which tackles the challenges of charge transport and interface improvement simultaneously.}, journal = {Advanced Energy Materials}, author = {Canil, Laura and Salunke, Jagadish and Wang, Qiong and Liu, Maning and Köbler, Hans and Flatken, Marion and Gregori, Luca and Meggiolaro, Daniele and Ricciarelli, Damiano and De Angelis, Filippo and Stolterfoht, Martin and Neher, Dieter and Priimagi, Arri and Vivo, Paola and Abate, Antonio}, month = aug, year = {2021}, pages = {2101553}, } - P. Lv, X. Yang, H. K. Bisoyi, H. Zeng, X. Zhang, Y. Chen, P. Xue, S. Shi, A. Priimagi, L. Wang, W. Feng, and Q. Li, “Stimulus-driven liquid metal and liquid crystal network actuators for programmable soft robotics,” Materials Horizons, vol. 8, pp. 2475-2484, 2021. doi:10.1039/D1MH00623A
[BibTeX] [Abstract]
Sophisticated soft matter engineering has been endorsed as an emerging paradigm for developing untethered soft robots with built-in electronic functions and biomimetic adaptation capacities. However, the integration of flexible electronic components into soft robotic actuators is challenging due to strain mismatch and material incompatibilities. Herein, we report a general strategy to integrate electrically conductive liquid metals (LMs) and shape-morphing liquid crystal networks (LCNs) towards multifunctional and programmable soft robotics. A unique colloidal LM ink with superior adhesion and photothermal conversion efficiency was judiciously designed and fabricated by ultrasonicating LMs and miniature carboxylated gold nanorods (MiniGNR-COOH) in an aqueous suspension of biological bacterial cellulose. The designed nanocellulose-based colloidal LM ink is used for shape-deformable and electrically conductive LM–LCN soft robots that can be electro- and photo-thermally actuated. As proof-of-concept demonstrations, we present a light-fueled soft oscillator, an inchworm-inspired soft crawler and programmable robotic Shadow Play exhibiting multifunctional controllability. The strategy disclosed here could open up a new technological arena for advanced multifunctional soft materials with potential utility in bioinspired soft machines, integrated soft electronics, human–computer interaction and beyond.
@article{lv_stimulus-driven_2021, title = {Stimulus-driven liquid metal and liquid crystal network actuators for programmable soft robotics}, volume = {8}, doi = {10.1039/D1MH00623A}, abstract = {Sophisticated soft matter engineering has been endorsed as an emerging paradigm for developing untethered soft robots with built-in electronic functions and biomimetic adaptation capacities. However, the integration of flexible electronic components into soft robotic actuators is challenging due to strain mismatch and material incompatibilities. Herein, we report a general strategy to integrate electrically conductive liquid metals (LMs) and shape-morphing liquid crystal networks (LCNs) towards multifunctional and programmable soft robotics. A unique colloidal LM ink with superior adhesion and photothermal conversion efficiency was judiciously designed and fabricated by ultrasonicating LMs and miniature carboxylated gold nanorods (MiniGNR-COOH) in an aqueous suspension of biological bacterial cellulose. The designed nanocellulose-based colloidal LM ink is used for shape-deformable and electrically conductive LM–LCN soft robots that can be electro- and photo-thermally actuated. As proof-of-concept demonstrations, we present a light-fueled soft oscillator, an inchworm-inspired soft crawler and programmable robotic Shadow Play exhibiting multifunctional controllability. The strategy disclosed here could open up a new technological arena for advanced multifunctional soft materials with potential utility in bioinspired soft machines, integrated soft electronics, human–computer interaction and beyond.}, journal = {Materials Horizons}, author = {Lv, Pengfei and Yang, Xiao and Bisoyi, Hari Krishna and Zeng, Hao and Zhang, Xuan and Chen, Yuanhao and Xue, Pan and Shi, Shukuan and Priimagi, Arri and Wang, Ling and Feng, Wei and Li, Quan}, month = jun, year = {2021}, pages = {2475--2484}, } - M. Ristola, C. Fedele, S. Hagman, L. Sukki, F. E. Kapucu, R. Mzezewa, T. Hyvärinen, P. Kallio, A. Priimagi, and S. Narkilahti, “Directional Growth of Human Neuronal Axons in a Microfluidic Device with Nanotopography on Azobenzene-Based Material,” Advanced Materials Interfaces, vol. 8, p. 2100048, 2021. doi:https://doi.org/10.1002/admi.202100048
[BibTeX] [Abstract]
Axonal dysfunction and degeneration are important pathological features of central nervous system (CNS) diseases and traumas, such as Alzheimer’s disease, traumatic brain injury, ischemic stroke and spinal cord injury. Engineered microfluidic chips combined with human pluripotent stem cell (hPSC)-derived neurons provide valuable tools for targeted in vitro research on axons to improve understanding of disease mechanisms and enhance drug development. Here, a polydimethylsiloxane (PDMS) microfluidic chip integrated with a light patterned substrate is utilized to achieve both isolated and unidirectional axonal growth of hPSC-derived neurons. The isolation of axons from somas and dendrites and robust axonal outgrowth to adjacent, axonal compartment, is achieved by optimized cross-sectional area and length of PDMS microtunnels in the microfluidic device. In the axonal compartment, the photoinscribed nanotopography on a thin film of azobenzene-containing molecular glass efficiently guides the growth of axons. Integration of nanotopographic patterns with a compartmentalized microfluidic chip creates a human neuron-based model that supports superior axonal alignment in an isolated microenvironment. The practical utility of the chip by studying oxygen-glucose deprivation-induced damage for the isolated and aligned axons is demonstrated here. The created chip model represents a sophisticated platform and a novel tool for enhanced and long-term axon-targeted in vitro studies.
@article{ristola_directional_2021, title = {Directional {Growth} of {Human} {Neuronal} {Axons} in a {Microfluidic} {Device} with {Nanotopography} on {Azobenzene}-{Based} {Material}}, volume = {8}, doi = {https://doi.org/10.1002/admi.202100048}, abstract = {Axonal dysfunction and degeneration are important pathological features of central nervous system (CNS) diseases and traumas, such as Alzheimer's disease, traumatic brain injury, ischemic stroke and spinal cord injury. Engineered microfluidic chips combined with human pluripotent stem cell (hPSC)-derived neurons provide valuable tools for targeted in vitro research on axons to improve understanding of disease mechanisms and enhance drug development. Here, a polydimethylsiloxane (PDMS) microfluidic chip integrated with a light patterned substrate is utilized to achieve both isolated and unidirectional axonal growth of hPSC-derived neurons. The isolation of axons from somas and dendrites and robust axonal outgrowth to adjacent, axonal compartment, is achieved by optimized cross-sectional area and length of PDMS microtunnels in the microfluidic device. In the axonal compartment, the photoinscribed nanotopography on a thin film of azobenzene-containing molecular glass efficiently guides the growth of axons. Integration of nanotopographic patterns with a compartmentalized microfluidic chip creates a human neuron-based model that supports superior axonal alignment in an isolated microenvironment. The practical utility of the chip by studying oxygen-glucose deprivation-induced damage for the isolated and aligned axons is demonstrated here. The created chip model represents a sophisticated platform and a novel tool for enhanced and long-term axon-targeted in vitro studies.}, journal = {Advanced Materials Interfaces}, author = {Ristola, Mervi and Fedele, Chiara and Hagman, Sanna and Sukki, Lassi and Kapucu, Fikret Emre and Mzezewa, Ropafadzo and Hyvärinen, Tanja and Kallio, Pasi and Priimagi, Arri and Narkilahti, Susanna}, month = may, year = {2021}, pages = {2100048}, } - J. Isokuortti, K. Kuntze, M. Virkki, Z. Ahmed, E. Vuorimaa-Laukkanen, M. A. Filatov, A. Turshatov, T. Laaksonen, A. Priimagi, and N. A. Durandin, “Expanding excitation wavelengths for azobenzene photoswitching into the near-infrared range via endothermic triplet energy transfer,” Chemical Science, vol. 12, pp. 7504-7509, 2021. doi:10.1039/D1SC01717A
[BibTeX] [Abstract]
Developing azobenzene photoswitches capable of selective and efficient photoisomerization by long-wavelength excitation is an enduring challenge. Herein, rapid isomerization from the Z- to E-state of two ortho-functionalized bistable azobenzenes with near-unity photoconversion efficiency was driven by triplet energy transfer upon red and near-infrared (up to 770 nm) excitation of porphyrin photosensitizers in catalytic micromolar concentrations. We show that the process of triplet-sensitized isomerization is efficient even when the sensitizer triplet energy is substantially lower (\textgreater200 meV) than that of the azobenzene used. This makes the approach applicable for a wide variety of sensitizer-azobenzene combinations and enables the expansion of excitation wavelengths into the near-infrared spectral range. Therefore, indirect excitation via endothermic triplet energy transfer provides efficient and precise means for photoswitching upon 770 nm near-infared light illumination with no chemical modification of the azobenzene chromophore, a desirable feature in photocontrollable biomaterials.
@article{isokuortti_expanding_2021, title = {Expanding excitation wavelengths for azobenzene photoswitching into the near-infrared range via endothermic triplet energy transfer}, volume = {12}, doi = {10.1039/D1SC01717A}, abstract = {Developing azobenzene photoswitches capable of selective and efficient photoisomerization by long-wavelength excitation is an enduring challenge. Herein, rapid isomerization from the Z- to E-state of two ortho-functionalized bistable azobenzenes with near-unity photoconversion efficiency was driven by triplet energy transfer upon red and near-infrared (up to 770 nm) excitation of porphyrin photosensitizers in catalytic micromolar concentrations. We show that the process of triplet-sensitized isomerization is efficient even when the sensitizer triplet energy is substantially lower ({\textgreater}200 meV) than that of the azobenzene used. This makes the approach applicable for a wide variety of sensitizer-azobenzene combinations and enables the expansion of excitation wavelengths into the near-infrared spectral range. Therefore, indirect excitation via endothermic triplet energy transfer provides efficient and precise means for photoswitching upon 770 nm near-infared light illumination with no chemical modification of the azobenzene chromophore, a desirable feature in photocontrollable biomaterials.}, journal = {Chemical Science}, author = {Isokuortti, Jussi and Kuntze, Kim and Virkki, Matti and Ahmed, Zafar and Vuorimaa-Laukkanen, Elina and Filatov, Mikhail A. and Turshatov, Andrey and Laaksonen, Timo and Priimagi, Arri and Durandin, Nikita A.}, month = apr, year = {2021}, pages = {7504--7509}, } - H. Daghigh Shirazi, Y. Dong, J. Niskanen, C. Fedele, A. Priimagi, V. P. Jokinen, and J. Vapaavuori, “Multiscale Hierarchical Surface Patterns by Coupling Optical Patterning and Thermal Shrinkage,” ACS Applied Materials & Interfaces, vol. 13, pp. 15563-15571, 2021. doi:10.1021/acsami.0c22436
[BibTeX] [Abstract]
Herein, a simple hierarchical surface patterning method is presented by effectively combining buckling instability and azopolymer-based surface relief grating inscription. In this technique, submicron patterns are achieved using azopolymers, whereas the microscale patterns are fabricated by subsequent thermal shrinkage. The wetting characterization of various topographically patterned surfaces confirms that the method permits tuning of contact angles and choosing between isotropic and anisotropic wetting. Altogether, this method allows efficient fabrication of hierarchical surfaces over several length scales in relatively large areas, overcoming some limitations of fabricating multiscale roughness in lithography and also methods of creating merely random patterns, such as black silicon processing or wet etching of metals. The demonstrated fine-tuning of the surface patterns may be useful in optimizing surface-related material properties, such as wetting and adhesion, producing substrates that are of potential interest in mechanobiology and tissue engineering.
@article{daghigh_shirazi_multiscale_2021, title = {Multiscale {Hierarchical} {Surface} {Patterns} by {Coupling} {Optical} {Patterning} and {Thermal} {Shrinkage}}, volume = {13}, doi = {10.1021/acsami.0c22436}, abstract = {Herein, a simple hierarchical surface patterning method is presented by effectively combining buckling instability and azopolymer-based surface relief grating inscription. In this technique, submicron patterns are achieved using azopolymers, whereas the microscale patterns are fabricated by subsequent thermal shrinkage. The wetting characterization of various topographically patterned surfaces confirms that the method permits tuning of contact angles and choosing between isotropic and anisotropic wetting. Altogether, this method allows efficient fabrication of hierarchical surfaces over several length scales in relatively large areas, overcoming some limitations of fabricating multiscale roughness in lithography and also methods of creating merely random patterns, such as black silicon processing or wet etching of metals. The demonstrated fine-tuning of the surface patterns may be useful in optimizing surface-related material properties, such as wetting and adhesion, producing substrates that are of potential interest in mechanobiology and tissue engineering.}, journal = {ACS Applied Materials \& Interfaces}, author = {Daghigh Shirazi, Hamidreza and Dong, Yujiao and Niskanen, Jukka and Fedele, Chiara and Priimagi, Arri and Jokinen, Ville P. and Vapaavuori, Jaana}, month = mar, year = {2021}, pages = {15563--15571}, } - P. Xue, H. K. Bisoyi, Y. Chen, H. Zeng, J. Yang, X. Yang, P. Lv, X. Zhang, A. Priimagi, L. Wang, X. Xu, and Q. Li, “Near-Infrared Light-Driven Shape-Morphing of Programmable Anisotropic Hydrogels Enabled by MXene Nanosheets,” Angewandte Chemie International Edition, vol. 57, pp. 2532-7, 2021. doi:10.1002/ange.202014533
[BibTeX] [Abstract]
Herein, we report near-infrared (NIR) light-driven shape-morphing of programmable MXene-containing aniso- tropic hydrogel actuators that are fabricated through in situ free-radical copolymerization of a judiciously designed MXene nanomonomer with thermosensitive hydrogel network. A low electric field (few V mm1) was found to enable a spatial distribution of MXene nanosheets and hence introduce aniso- tropy into the hydrogel network. Programmable anisotropic hydrogel actuators were developed by controlling ITO elec- trode pattern, direct-current (DC) electric field direction and mask-assisted photopolymerization. As a proof-of-concept, we demonstrate NIR light-driven shape morphing of the MXene- containing anisotropic hydrogel into various shapes and devise a four-arm soft gripper that can perform distinct photo- mechanical functions such as grasping, lifting/lowering down and releasing an object upon sequential NIR light exposure.
@article{xue_near-infrared_2021, title = {Near-{Infrared} {Light}-{Driven} {Shape}-{Morphing} of {Programmable} {Anisotropic} {Hydrogels} {Enabled} by {MXene} {Nanosheets}}, volume = {57}, doi = {10.1002/ange.202014533}, abstract = {Herein, we report near-infrared (NIR) light-driven shape-morphing of programmable MXene-containing aniso- tropic hydrogel actuators that are fabricated through in situ free-radical copolymerization of a judiciously designed MXene nanomonomer with thermosensitive hydrogel network. A low electric field (few V mm1) was found to enable a spatial distribution of MXene nanosheets and hence introduce aniso- tropy into the hydrogel network. Programmable anisotropic hydrogel actuators were developed by controlling ITO elec- trode pattern, direct-current (DC) electric field direction and mask-assisted photopolymerization. As a proof-of-concept, we demonstrate NIR light-driven shape morphing of the MXene- containing anisotropic hydrogel into various shapes and devise a four-arm soft gripper that can perform distinct photo- mechanical functions such as grasping, lifting/lowering down and releasing an object upon sequential NIR light exposure.}, journal = {Angewandte Chemie International Edition}, author = {Xue, Pan and Bisoyi, Hari Krishna and Chen, Yuanhao and Zeng, Hao and Yang, Jiajia and Yang, Xiao and Lv, Pengfei and Zhang, Xinmu and Priimagi, Arri and Wang, Ling and Xu, Xinhua and Li, Quan}, month = jan, year = {2021}, pages = {2532--7}, }
2020
- C. Fedele, E. Mäntylä, B. Belardi, T. Hamkins-Indik, S. Cavalli, P. A. Netti, D. A. Fletcher, S. Nymark, A. Priimagi, and T. O. Ihalainen, “Azobenzene-based sinusoidal surface topography drives focal adhesion confinement and guides collective migration of epithelial cells,” Scientific Reports, vol. 10, p. 15329, 2020. doi:10.1038/s41598-020-71567-w
[BibTeX] [Abstract]
Surface topography is a key parameter in regulating the morphology and behavior of single cells. At multicellular level, coordinated cell displacements drive many biological events such as embryonic morphogenesis. However, the effect of surface topography on collective migration of epithelium has not been studied in detail. Mastering the connection between surface features and collective cellular behaviour is highly important for novel approaches in tissue engineering and repair. Herein, we used photopatterned microtopographies on azobenzene-containing materials and showed that smooth topographical cues with proper period and orientation can efficiently orchestrate cell alignment in growing epithelium. Furthermore, the experimental system allowed us to investigate how the orientation of the topographical features can alter the speed of wound closure in vitro. Our findings indicate that the extracellular microenvironment topography coordinates their focal adhesion distribution and alignment. These topographic cues are able to guide the collective migration of multicellular systems, even when cell–cell junctions are disrupted.
@article{fedele_azobenzene-based_2020, title = {Azobenzene-based sinusoidal surface topography drives focal adhesion confinement and guides collective migration of epithelial cells}, volume = {10}, doi = {10.1038/s41598-020-71567-w}, abstract = {Surface topography is a key parameter in regulating the morphology and behavior of single cells. At multicellular level, coordinated cell displacements drive many biological events such as embryonic morphogenesis. However, the effect of surface topography on collective migration of epithelium has not been studied in detail. Mastering the connection between surface features and collective cellular behaviour is highly important for novel approaches in tissue engineering and repair. Herein, we used photopatterned microtopographies on azobenzene-containing materials and showed that smooth topographical cues with proper period and orientation can efficiently orchestrate cell alignment in growing epithelium. Furthermore, the experimental system allowed us to investigate how the orientation of the topographical features can alter the speed of wound closure in vitro. Our findings indicate that the extracellular microenvironment topography coordinates their focal adhesion distribution and alignment. These topographic cues are able to guide the collective migration of multicellular systems, even when cell–cell junctions are disrupted.}, journal = {Scientific Reports}, author = {Fedele, Chiara and Mäntylä, Elina and Belardi, Brian and Hamkins-Indik, Tiama and Cavalli, Silvia and Netti, Paolo A. and Fletcher, Daniel A. and Nymark, Soile and Priimagi, Arri and Ihalainen, Teemu O.}, month = dec, year = {2020}, pages = {15329}, } - H. Rekola, A. Berdin, C. Fedele, M. Virkki, and A. Priimagi, “Digital holographic microscopy for real-time observation of surface-relief grating formation on azobenzene-containing films,” Scientific Reports, vol. 10, p. 19642, 2020. doi:10.1038/s41598-020-76573-6
[BibTeX] [Abstract]
Light-induced surface structuring of azobenzene-containing films allows for creation of complex surface relief patterns with varying heights, patterns which would be difficult to create using conventional lithography tools. In order to realize the full potential of these patternable surfaces, understanding their formation dynamics and response to different types of light fields is crucial. In the present work we introduce digital holographic microscopy (DHM) for real time, in-situ observation of surface-relief grating (SRG) formation on azobenzene-containing films. This instrument allows us to measure the surface topography of films while illuminating them with two individually controlled laser beams for creating periodically varying patterns. By utilizing the information of the grating formation dynamics, we combine multiple grating patterns to create pixels with wide gamut structural colors as well as blazed grating structures on the film surface. As long as the material behaviour is linear, any Fourier optical surface can be created utilizing this multiple patterning approach. The DHM instrument presented here has the potential for creating complex 3D surface reliefs with nanometric precision.
@article{rekola_digital_2020, title = {Digital holographic microscopy for real-time observation of surface-relief grating formation on azobenzene-containing films}, volume = {10}, doi = {10.1038/s41598-020-76573-6}, abstract = {Light-induced surface structuring of azobenzene-containing films allows for creation of complex surface relief patterns with varying heights, patterns which would be difficult to create using conventional lithography tools. In order to realize the full potential of these patternable surfaces, understanding their formation dynamics and response to different types of light fields is crucial. In the present work we introduce digital holographic microscopy (DHM) for real time, in-situ observation of surface-relief grating (SRG) formation on azobenzene-containing films. This instrument allows us to measure the surface topography of films while illuminating them with two individually controlled laser beams for creating periodically varying patterns. By utilizing the information of the grating formation dynamics, we combine multiple grating patterns to create pixels with wide gamut structural colors as well as blazed grating structures on the film surface. As long as the material behaviour is linear, any Fourier optical surface can be created utilizing this multiple patterning approach. The DHM instrument presented here has the potential for creating complex 3D surface reliefs with nanometric precision.}, journal = {Scientific Reports}, author = {Rekola, Heikki and Berdin, Alex and Fedele, Chiara and Virkki, Matti and Priimagi, Arri}, month = nov, year = {2020}, pages = {19642}, } - M. Lahikainen, K. Kuntze, H. Zeng, S. Helantera, S. Hecht, and A. Priimagi, “Tunable Photomechanics in Diarylethene-Driven Liquid Crystal Network Actuators,” ACS Applied Materials & Interfaces, vol. 12, pp. 47939-47947, 2020. doi:10.1021/acsami.0c12735
[BibTeX] [Abstract]
The response of soft actuators made of stimuli-responsive materials can be phenomenologically described by a stimulus- deformation curve, depicting the controllability and sensitivity of the actuator system. Manipulating such stimulus-deformation curve allows fabricating soft microrobots with reconfigurable actuation behavior, which is not easily achievable using conventional materials. Here, we report a light-driven actuator based on a liquid crystal polymer network containing diarylethene (DAE) photoswitches as cross-links, in which the stimulus-deformation curve under visible-light illumination is tuned with UV light. The tuning is brought about by the reversible electrocyclization of the DAE units. Because of the excellent thermal stability of the visible-absorbing closed-form DAEs, the absorbance of the actuator can be optically fixed to a desired value, which in turn dictates the efficiency of photothermally induced deformation. We employ the controllability in devising a logical AND gate with macroscopic output, i.e., an actuator that bends negligibly under UV or visible light irradiation, but with profound shape change when addressed to both simultaneously. The results provide design tools for reconfigurable microrobotics and polymer-based logic gating.
@article{lahikainen_tunable_2020, title = {Tunable {Photomechanics} in {Diarylethene}-{Driven} {Liquid} {Crystal} {Network} {Actuators}}, volume = {12}, doi = {10.1021/acsami.0c12735}, abstract = {The response of soft actuators made of stimuli-responsive materials can be phenomenologically described by a stimulus- deformation curve, depicting the controllability and sensitivity of the actuator system. Manipulating such stimulus-deformation curve allows fabricating soft microrobots with reconfigurable actuation behavior, which is not easily achievable using conventional materials. Here, we report a light-driven actuator based on a liquid crystal polymer network containing diarylethene (DAE) photoswitches as cross-links, in which the stimulus-deformation curve under visible-light illumination is tuned with UV light. The tuning is brought about by the reversible electrocyclization of the DAE units. Because of the excellent thermal stability of the visible-absorbing closed-form DAEs, the absorbance of the actuator can be optically fixed to a desired value, which in turn dictates the efficiency of photothermally induced deformation. We employ the controllability in devising a logical AND gate with macroscopic output, i.e., an actuator that bends negligibly under UV or visible light irradiation, but with profound shape change when addressed to both simultaneously. The results provide design tools for reconfigurable microrobotics and polymer-based logic gating.}, journal = {ACS Applied Materials \& Interfaces}, author = {Lahikainen, Markus and Kuntze, Kim and Zeng, Hao and Helantera, Seidi and Hecht, Stefan and Priimagi, Arri}, month = oct, year = {2020}, pages = {47939--47947}, } - J. M. Taskinen, A. J. Moilanen, H. Rekola, K. Kuntze, A. Priimagi, P. Törmä, and T. K. Hakala, “All-Optical Emission Control and Lasing in Plasmonic Lattices,” ACS Photonics, vol. 7, pp. 2850-2858, 2020. doi:10.1021/acsphotonics.0c01099
[BibTeX] [Abstract]
We report on reversible all-optical emission control and lasing in plasmonic nanoparticle lattices. By incorporating photochromic molecules into the liquid gain medium composed of organic fluorescent molecules, we realize all-optical control over gain and absorption, the two key parameters associated with both conventional and nanoscale lasing. We demonstrate reversible photoswitching between two distinct modes of operation: (1) spontaneous emission to the lattice mode, characterized by broad emission line width, low emission intensity, and large angular distribution; and (2) lasing action, characterized by very narrow (sub-nm) line widths due to the emergence of increased gain and temporal coherence in the system, approximately 3 orders of magnitude increase in emission intensity, and narrow 0.7\textbackslash,$^\textrm\textbackslashcirc$ angular divergence of the beam. A rate-equation model is employed to describe the operation of the switchable plasmonic laser. Our results provide the first demonstration of optically tunable losses in plasmonic lattice lasers, which is an important milestone for the development of active plasmonics and paves the way for ultrafast all-optical switching of plasmonic nanolasers.
@article{taskinen_all-optical_2020, title = {All-{Optical} {Emission} {Control} and {Lasing} in {Plasmonic} {Lattices}}, volume = {7}, doi = {10.1021/acsphotonics.0c01099}, abstract = {We report on reversible all-optical emission control and lasing in plasmonic nanoparticle lattices. By incorporating photochromic molecules into the liquid gain medium composed of organic fluorescent molecules, we realize all-optical control over gain and absorption, the two key parameters associated with both conventional and nanoscale lasing. We demonstrate reversible photoswitching between two distinct modes of operation: (1) spontaneous emission to the lattice mode, characterized by broad emission line width, low emission intensity, and large angular distribution; and (2) lasing action, characterized by very narrow (sub-nm) line widths due to the emergence of increased gain and temporal coherence in the system, approximately 3 orders of magnitude increase in emission intensity, and narrow 0.7{\textbackslash},$^{\textrm{{\textbackslash}circ}}$ angular divergence of the beam. A rate-equation model is employed to describe the operation of the switchable plasmonic laser. Our results provide the first demonstration of optically tunable losses in plasmonic lattice lasers, which is an important milestone for the development of active plasmonics and paves the way for ultrafast all-optical switching of plasmonic nanolasers.}, journal = {ACS Photonics}, author = {Taskinen, Jani M. and Moilanen, Antti J. and Rekola, Heikki and Kuntze, Kim and Priimagi, Arri and Törmä, Päivi and Hakala, Tommi K.}, month = oct, year = {2020}, pages = {2850--2858}, } - J. Salunke, X. Guo, M. Liu, Z. Lin, N. R. Candeias, A. Priimagi, J. Chang, and P. Vivo, “N-Substituted Phenothiazines as Environmentally Friendly Hole-Transporting Materials for Low-Cost and Highly Stable Halide Perovskite Solar Cells,” ACS Omega, vol. 5, pp. 23334-23342, 2020. doi:10.1021/acsomega.0c03184
[BibTeX] [Abstract]
Most of the high-performing halide perovskite solar cells (PSCs) leverage toxic chlorinated solvents (e.g., o-dichlorobenzene or chlorobenzene) for the hole-transporting material (HTM) processing and/or antisolvents in the perovskite film fabrication. To minimize the environmental and health-related hazards, it is highly desirable, yet at the same time demanding, to develop HTMs and perovskite deposition processes relying on nonhalogenated solvents. In this work, we designed two small molecules, AZO-III and AZO-IV, and synthesized them via simple and environmentally friendly Schiff base chemistry, by condensation of electron-donating triarylamine and phenothiazine moieties connected through an azomethine bridge. The molecules are implemented as HTMs in PSCs upon processing in a nonchlorinated (toluene) solvent, rendering their synthesis and film preparation eco-friendly. The enhancement in the power conversion efficiency (PCE) was achieved when switching from AZO-III (9.77\%) to AZO-IV (11.62\%), in which the thioethyl group is introduced in the 2-position of the phenothiazine ring. Additionally, unencapsulated PSCs based on AZO-III displayed excellent stabilities (75\% of the initial PCEs is retained after 6 months of air exposure for AZO-III to be compared with a 48\% decrease of the initial PCE for Spiro-OMeTAD-based devices). The outstanding stability and the extremely low production cost (AZO-III = 9.23 \textbackslash/g and AZO-IV = 9.03 \textbackslash/g), together with the environmentally friendly synthesis, purification, and processing, make these materials attractive candidates as HTMs for cost-effective, stable, and eco-friendly PSCs.
@article{salunke_n-substituted_2020, title = {N-{Substituted} {Phenothiazines} as {Environmentally} {Friendly} {Hole}-{Transporting} {Materials} for {Low}-{Cost} and {Highly} {Stable} {Halide} {Perovskite} {Solar} {Cells}}, volume = {5}, doi = {10.1021/acsomega.0c03184}, abstract = {Most of the high-performing halide perovskite solar cells (PSCs) leverage toxic chlorinated solvents (e.g., o-dichlorobenzene or chlorobenzene) for the hole-transporting material (HTM) processing and/or antisolvents in the perovskite film fabrication. To minimize the environmental and health-related hazards, it is highly desirable, yet at the same time demanding, to develop HTMs and perovskite deposition processes relying on nonhalogenated solvents. In this work, we designed two small molecules, AZO-III and AZO-IV, and synthesized them via simple and environmentally friendly Schiff base chemistry, by condensation of electron-donating triarylamine and phenothiazine moieties connected through an azomethine bridge. The molecules are implemented as HTMs in PSCs upon processing in a nonchlorinated (toluene) solvent, rendering their synthesis and film preparation eco-friendly. The enhancement in the power conversion efficiency (PCE) was achieved when switching from AZO-III (9.77\%) to AZO-IV (11.62\%), in which the thioethyl group is introduced in the 2-position of the phenothiazine ring. Additionally, unencapsulated PSCs based on AZO-III displayed excellent stabilities (75\% of the initial PCEs is retained after 6 months of air exposure for AZO-III to be compared with a 48\% decrease of the initial PCE for Spiro-OMeTAD-based devices). The outstanding stability and the extremely low production cost (AZO-III = 9.23 {\textbackslash}/g and AZO-IV = 9.03 {\textbackslash}/g), together with the environmentally friendly synthesis, purification, and processing, make these materials attractive candidates as HTMs for cost-effective, stable, and eco-friendly PSCs.}, journal = {ACS Omega}, author = {Salunke, Jagadish and Guo, Xing and Liu, Maning and Lin, Zhenhua and Candeias, Nuno R. and Priimagi, Arri and Chang, Jingjing and Vivo, Paola}, month = sep, year = {2020}, pages = {23334--23342}, } - J. Vapaavuori, J. E. Koskela, X. Wang, R. H. A. Ras, A. Priimagi, G. C. Bazuin, and C. Pellerin, “Effect of hydrogen-bond strength on photoresponsive properties of polymer-azobenzene complexes,” Canadian Journal of Chemistry, vol. 98, pp. 531-538, 2020. doi:10.1139/cjc-2020-0048
[BibTeX] [Abstract]
Supramolecular complexation between photoresponsive azobenzene chromophores and a photopassive polymer host offers synthetic and design advantages compared with conventional covalent azo-containing polymers. In this context, it is important to understand the impact of the strength of the supramolecular interaction on the optical response. Herein, we study the effect of hydrogen-bonding strength between a photopassive polymer host [poly(4-vinylpyridine), or P4VP] and three azobenzene analogues capable of forming weaker (hydroxyl), stronger (carboxylic acid), or no H-bonding with P4VP. The hydroxyl-functionalized azo forms complete H-bonding complexation up to equimolar ratio with VP, whereas the COOH-functionalized azo reaches only up to 30\% H-bond complexation due to competing acid dimerization that leads to partial phase separation and azo crystallization. We show that the stronger azo-polymer H-bonding nevertheless provides higher photoin-duced orientation and better performance during optical surface patterning, in terms of grating depth and diffraction efficiency, when phase separation is either avoided altogether or is limited by using relatively low azo contents. These results demonstrate the importance of the H-bonding strength on the photoresponse of azopolymer complexes, as well as the need to consider the interplay between different intermolecular interactions that can affect complexation.
@article{vapaavuori_effect_2020, title = {Effect of hydrogen-bond strength on photoresponsive properties of polymer-azobenzene complexes}, volume = {98}, doi = {10.1139/cjc-2020-0048}, abstract = {Supramolecular complexation between photoresponsive azobenzene chromophores and a photopassive polymer host offers synthetic and design advantages compared with conventional covalent azo-containing polymers. In this context, it is important to understand the impact of the strength of the supramolecular interaction on the optical response. Herein, we study the effect of hydrogen-bonding strength between a photopassive polymer host [poly(4-vinylpyridine), or P4VP] and three azobenzene analogues capable of forming weaker (hydroxyl), stronger (carboxylic acid), or no H-bonding with P4VP. The hydroxyl-functionalized azo forms complete H-bonding complexation up to equimolar ratio with VP, whereas the COOH-functionalized azo reaches only up to 30\% H-bond complexation due to competing acid dimerization that leads to partial phase separation and azo crystallization. We show that the stronger azo-polymer H-bonding nevertheless provides higher photoin-duced orientation and better performance during optical surface patterning, in terms of grating depth and diffraction efficiency, when phase separation is either avoided altogether or is limited by using relatively low azo contents. These results demonstrate the importance of the H-bonding strength on the photoresponse of azopolymer complexes, as well as the need to consider the interplay between different intermolecular interactions that can affect complexation.}, journal = {Canadian Journal of Chemistry}, author = {Vapaavuori, Jaana and Koskela, Jenni E. and Wang, Xiaoxiao and Ras, Robin H.A. and Priimagi, Arri and Bazuin, C. Geraldine and Pellerin, Christian}, month = sep, year = {2020}, pages = {531--538}, } - A. S. Kuenstler, M. Lahikainen, H. Zhou, W. Xu, A. Priimagi, and R. C. Hayward, “Reconfiguring Gaussian Curvature of Hydrogel Sheets with Photoswitchable Host-Guest Interactions,” ACS Macro Letters, vol. 9, pp. 1172-1177, 2020. doi:10.1021/acsmacrolett.0c00469
[BibTeX] [Abstract]
Photoinduced shape morphing has implications in fields ranging from soft robotics to biomedical devices. Despite considerable effort in this area, it remains a challenge to design materials that can be both rapidly deployed and reconfigured into multiple different three-dimensional forms, particularly in aqueous environments. In this work, we present a simple method to program and rewrite spatial variations in swelling and, therefore, Gaussian curvature in thin sheets of hydrogels using photoswitchable supramolecular complexation of azobenzene pendent groups with dissolved α-cyclodextrin. We show that the extent of swelling can be programmed via the proportion of azobenzene isomers, with a 60\% decrease in areal swelling from the all trans to the predominantly cis state near room temperature. The use of thin gel sheets provides fast response times in the range of a few tens of seconds, while the shape change is persistent in the absence of light thanks to the slow rate of thermal cis-trans isomerization. Finally, we demonstrate that a single gel sheet can be programmed with a first swelling pattern via spatially defined illumination with ultraviolet light, then erased with white light, and finally redeployed with a different swelling pattern.
@article{kuenstler_reconfiguring_2020, title = {Reconfiguring {Gaussian} {Curvature} of {Hydrogel} {Sheets} with {Photoswitchable} {Host}-{Guest} {Interactions}}, volume = {9}, doi = {10.1021/acsmacrolett.0c00469}, abstract = {Photoinduced shape morphing has implications in fields ranging from soft robotics to biomedical devices. Despite considerable effort in this area, it remains a challenge to design materials that can be both rapidly deployed and reconfigured into multiple different three-dimensional forms, particularly in aqueous environments. In this work, we present a simple method to program and rewrite spatial variations in swelling and, therefore, Gaussian curvature in thin sheets of hydrogels using photoswitchable supramolecular complexation of azobenzene pendent groups with dissolved α-cyclodextrin. We show that the extent of swelling can be programmed via the proportion of azobenzene isomers, with a 60\% decrease in areal swelling from the all trans to the predominantly cis state near room temperature. The use of thin gel sheets provides fast response times in the range of a few tens of seconds, while the shape change is persistent in the absence of light thanks to the slow rate of thermal cis-trans isomerization. Finally, we demonstrate that a single gel sheet can be programmed with a first swelling pattern via spatially defined illumination with ultraviolet light, then erased with white light, and finally redeployed with a different swelling pattern.}, journal = {ACS Macro Letters}, author = {Kuenstler, Alexa S. and Lahikainen, Markus and Zhou, Hantao and Xu, Wenwen and Priimagi, Arri and Hayward, Ryan C.}, month = aug, year = {2020}, pages = {1172--1177}, } - B. O. Asamoah, S. Mohamed, S. Datta, P. Karvinen, H. Rekola, A. Priimagi, and T. K. Hakala, “Optically induced crossover from weak to strong coupling regime between surface plasmon polaritons and photochromic molecules,” Optics Express, vol. 28, p. 26509, 2020. doi:10.1364/oe.400359
[BibTeX] [Abstract]
We demonstrate optically induced crossover from a weak to a strong coupling regime in a single photonic system consisting of propagating surface plasmon polaritons (SPPs) on a planar silver film and ultraviolet (UV)-switchable photochromic molecules. A gradual increase is observed in the vacuum Rabi splitting upon increasing UV exposure, along with intriguing behavior, where the reflectivity initially decreases due to increased losses at the weak coupling regime, and then increases due to the emergence of strongly coupled modes and the associated band gap formation at the resonance frequency of the uncoupled states. This work explicitly demonstrates the optical tunability of the degree of hybridization of the SPP and exciton modes, spanning the range from weak to intermediate and finally to the strong coupling regime.
@article{asamoah_optically_2020, title = {Optically induced crossover from weak to strong coupling regime between surface plasmon polaritons and photochromic molecules}, volume = {28}, doi = {10.1364/oe.400359}, abstract = {We demonstrate optically induced crossover from a weak to a strong coupling regime in a single photonic system consisting of propagating surface plasmon polaritons (SPPs) on a planar silver film and ultraviolet (UV)-switchable photochromic molecules. A gradual increase is observed in the vacuum Rabi splitting upon increasing UV exposure, along with intriguing behavior, where the reflectivity initially decreases due to increased losses at the weak coupling regime, and then increases due to the emergence of strongly coupled modes and the associated band gap formation at the resonance frequency of the uncoupled states. This work explicitly demonstrates the optical tunability of the degree of hybridization of the SPP and exciton modes, spanning the range from weak to intermediate and finally to the strong coupling regime.}, journal = {Optics Express}, author = {Asamoah, Benjamin O. and Mohamed, Sughra and Datta, Srijoyee and Karvinen, Petri and Rekola, Heikki and Priimagi, Arri and Hakala, Tommi K.}, month = aug, year = {2020}, pages = {26509}, } - E. Tervola, K. N. Truong, J. S. Ward, A. Priimagi, and K. Rissanen, “Fluorescence enhancement of quinolines by protonation,” RSC Advances, vol. 10, pp. 29385-29393, 2020. doi:10.1039/d0ra04691d
[BibTeX] [Abstract]
A study of the fluorescence enhancement of isoquinoline, acridine (benzo[b]quinoline) and benzo[h]quinoline is reported with six organic acids of different pKa values. Protonation was found to be an effective tool in the fluorescence enhancement of quinolines. A significant increase in the fluorescence intensity is observed only when strong acids are used, resulting in an over 50-fold increase in fluorescence with trifluoroacetic or benzenesulfonic acid and isoquinoline in a 1.5 : 1 ratio. The benzenesulfonic acid was found to be the most effective in the protonation of the bases despite its higher pKa value compared to trifluoro- and trichloroacetic acid. The X-ray crystal structures of 14 salts reveal the charge-assisted hydrogen bond O⋯N distances to vary very little, from 2.560(2)-2.714(3) Å, with the exception of the isoquinolinium benzenesulfonate where the O⋯N distance of 2.862(7) Å is caused by additional intermolecular interactions in the solid-state.
@article{tervola_fluorescence_2020, title = {Fluorescence enhancement of quinolines by protonation}, volume = {10}, doi = {10.1039/d0ra04691d}, abstract = {A study of the fluorescence enhancement of isoquinoline, acridine (benzo[b]quinoline) and benzo[h]quinoline is reported with six organic acids of different pKa values. Protonation was found to be an effective tool in the fluorescence enhancement of quinolines. A significant increase in the fluorescence intensity is observed only when strong acids are used, resulting in an over 50-fold increase in fluorescence with trifluoroacetic or benzenesulfonic acid and isoquinoline in a 1.5 : 1 ratio. The benzenesulfonic acid was found to be the most effective in the protonation of the bases despite its higher pKa value compared to trifluoro- and trichloroacetic acid. The X-ray crystal structures of 14 salts reveal the charge-assisted hydrogen bond O⋯N distances to vary very little, from 2.560(2)-2.714(3) Å, with the exception of the isoquinolinium benzenesulfonate where the O⋯N distance of 2.862(7) Å is caused by additional intermolecular interactions in the solid-state.}, journal = {RSC Advances}, author = {Tervola, Essi and Truong, Khai Nghi and Ward, Jas S. and Priimagi, Arri and Rissanen, Kari}, month = aug, year = {2020}, pages = {29385--29393}, } - A. Eklund, H. Zhang, H. Zeng, A. Priimagi, and O. Ikkala, “Fast Switching of Bright Whiteness in Channeled Hydrogel Networks,” Advanced Functional Materials, vol. 30, p. 2000754, 2020. doi:10.1002/adfm.202000754
[BibTeX] [Abstract]
Beside pigment absorption and reflection by periodic photonic structures, natural species often use light scattering to achieve whiteness. Synthetic hydrogels offer opportunities in stimuli-responsive materials and devices; however, they are not conventionally considered as ideal materials to achieve high whiteness by scattering due to the ill-defined porosities and the low refractive index contrast between the polymer and water. Herein, a poly(N-isopropylacrylamide) hydrogel network with percolated empty channels (ch-PNIPAm) is demonstrated to possess switchable bright whiteness upon temperature changes, obtained by removing the physical agarose gel in a semi-interpenetrating network of agarose and PNIPAm. The hydrogel is highly transparent at room temperature and becomes brightly white above 35 \textbackslash,$^\textrm\textbackslashcirc$C. Compared to conventional PNIPAm, the ch-PNIPAm hydrogel exhibits 80\% higher reflectance at 800 nm and 18 times faster phase transition kinetics. The nanoscopic channels in the ch-PNIPAm facilitate water diffusion upon phase transition, thus enabling the formation of smaller pores and enhanced whiteness in the gel. Furthermore, fast photothermally triggered response down to tens of milliseconds can be achieved. This unique property of the ch-PNIPAm hydrogel to efficiently scatter visible light can be potentially used for, e.g., smart windows, optical switches, and, as demonstrated in this report, thermoresponsive color displays.
@article{eklund_fast_2020, title = {Fast {Switching} of {Bright} {Whiteness} in {Channeled} {Hydrogel} {Networks}}, volume = {30}, doi = {10.1002/adfm.202000754}, abstract = {Beside pigment absorption and reflection by periodic photonic structures, natural species often use light scattering to achieve whiteness. Synthetic hydrogels offer opportunities in stimuli-responsive materials and devices; however, they are not conventionally considered as ideal materials to achieve high whiteness by scattering due to the ill-defined porosities and the low refractive index contrast between the polymer and water. Herein, a poly(N-isopropylacrylamide) hydrogel network with percolated empty channels (ch-PNIPAm) is demonstrated to possess switchable bright whiteness upon temperature changes, obtained by removing the physical agarose gel in a semi-interpenetrating network of agarose and PNIPAm. The hydrogel is highly transparent at room temperature and becomes brightly white above 35 {\textbackslash},$^{\textrm{{\textbackslash}circ}}$C. Compared to conventional PNIPAm, the ch-PNIPAm hydrogel exhibits 80\% higher reflectance at 800 nm and 18 times faster phase transition kinetics. The nanoscopic channels in the ch-PNIPAm facilitate water diffusion upon phase transition, thus enabling the formation of smaller pores and enhanced whiteness in the gel. Furthermore, fast photothermally triggered response down to tens of milliseconds can be achieved. This unique property of the ch-PNIPAm hydrogel to efficiently scatter visible light can be potentially used for, e.g., smart windows, optical switches, and, as demonstrated in this report, thermoresponsive color displays.}, journal = {Advanced Functional Materials}, author = {Eklund, Amanda and Zhang, Hang and Zeng, Hao and Priimagi, Arri and Ikkala, Olli}, month = jul, year = {2020}, pages = {2000754}, } - O. M. Wani, A. P. H. J. Schenning, and A. Priimagi, “A bifacial colour-tunable system: Via combination of a cholesteric liquid crystal network and hydrogel,” Journal of Materials Chemistry C, vol. 8, pp. 10191-10196, 2020. doi:10.1039/d0tc02189j
[BibTeX] [Abstract]
We present a colour tunable system obtained by combining a humidity-responsive cholesteric liquid crystal network and hydrogel coatings, in a diligently designed cell-geometry. The design enables sensitive colour tuning via temperature-induced changes in humidity inside the cell. Uniquely, the system exhibits a bifacial response, causing either a blue- or red-shift in the reflected color when heated from opposite sides.
@article{wani_bifacial_2020, title = {A bifacial colour-tunable system: {Via} combination of a cholesteric liquid crystal network and hydrogel}, volume = {8}, doi = {10.1039/d0tc02189j}, abstract = {We present a colour tunable system obtained by combining a humidity-responsive cholesteric liquid crystal network and hydrogel coatings, in a diligently designed cell-geometry. The design enables sensitive colour tuning via temperature-induced changes in humidity inside the cell. Uniquely, the system exhibits a bifacial response, causing either a blue- or red-shift in the reflected color when heated from opposite sides.}, journal = {Journal of Materials Chemistry C}, author = {Wani, Owies M. and Schenning, Albertus P.H.J. and Priimagi, Arri}, month = jul, year = {2020}, pages = {10191--10196}, } - M. Lahikainen, H. Zeng, and A. Priimagi, “Design principles for non-reciprocal photomechanical actuation,” Soft Matter, vol. 16, pp. 5951-5958, 2020. doi:10.1039/d0sm00624f
[BibTeX] [Abstract]
Non-reciprocal motions are a sequence of movements exhibiting time-reversal asymmetry. Such movements are common among various natural species, being adopted as a typical strategy for achieving efficient locomotion. Generally, the realization of non-reciprocal motions in man-made robotic devices requires synchronous control of at least two individual actuators, hence posing challenges to soft micro-robotics where the miniaturization limits integration of different mechanical components and the possibility of using onboard batteries. Here, we introduce general concepts for achieving non-reciprocal movements in wirelessly controlled soft actuators made of photomechanically responsive liquid crystal networks. The monolithic actuators are composed of two segments that can be actuated photochemically and photothermally, and the non-reciprocal motion is obtained by a control sequence that temporally modulates light sources of different wavelengths. Through proper selection of photoactive compounds, the number of modulated light sources can be decreased, from three to two, and eventually to one. Finally, we demonstrate non-reciprocal self-oscillation by self-shadowing effect in a flexible strip under a constant light field with no temporal modulation. This study provides general guidelines to light-controlled non-reciprocal actuation, offering new strategies for the control of wireless soft micro-robotics.
@article{lahikainen_design_2020, title = {Design principles for non-reciprocal photomechanical actuation}, volume = {16}, doi = {10.1039/d0sm00624f}, abstract = {Non-reciprocal motions are a sequence of movements exhibiting time-reversal asymmetry. Such movements are common among various natural species, being adopted as a typical strategy for achieving efficient locomotion. Generally, the realization of non-reciprocal motions in man-made robotic devices requires synchronous control of at least two individual actuators, hence posing challenges to soft micro-robotics where the miniaturization limits integration of different mechanical components and the possibility of using onboard batteries. Here, we introduce general concepts for achieving non-reciprocal movements in wirelessly controlled soft actuators made of photomechanically responsive liquid crystal networks. The monolithic actuators are composed of two segments that can be actuated photochemically and photothermally, and the non-reciprocal motion is obtained by a control sequence that temporally modulates light sources of different wavelengths. Through proper selection of photoactive compounds, the number of modulated light sources can be decreased, from three to two, and eventually to one. Finally, we demonstrate non-reciprocal self-oscillation by self-shadowing effect in a flexible strip under a constant light field with no temporal modulation. This study provides general guidelines to light-controlled non-reciprocal actuation, offering new strategies for the control of wireless soft micro-robotics.}, journal = {Soft Matter}, author = {Lahikainen, Markus and Zeng, Hao and Priimagi, Arri}, month = jun, year = {2020}, pages = {5951--5958}, } - H. Zhang, H. Zeng, A. Priimagi, and O. Ikkala, “Viewpoint: Pavlovian Materials — Functional Biomimetics Inspired by Classical Conditioning,” Advanced Materials, vol. 32, p. 1906619, 2020. doi:10.1002/adma.201906619
[BibTeX] [Abstract]
Herein, it is discussed whether the complex biological concepts of (associative) learning can inspire responsive artificial materials. It is argued that classical conditioning, being one of the most elementary forms of learning, inspires algorithmic realizations in synthetic materials, to allow stimuli-responsive materials that learn to respond to a new stimulus, to which they are originally insensitive. Two synthetic model systems coined as “Pavlovian materials” are described, whose stimuli-responsiveness algorithmically mimics programmable associative learning, inspired by classical conditioning. The concepts minimally need a stimulus-triggerable memory, in addition to two stimuli, i.e., the unconditioned and the originally neutral stimuli. Importantly, the concept differs conceptually from the classic stimuli-responsive and shape-memory materials, as, upon association, Pavlovian materials obtain a given response using a new stimulus (the originally neutral one); i.e., the system evolves to a new state. This also enables the functionality to be described by a logic diagram. Ample room for generalization to different stimuli and memory combinations is foreseen, and opportunities to develop future adaptive materials with ever-more intelligent functions are expected.
@article{zhang_viewpoint_2020, title = {Viewpoint: {Pavlovian} {Materials} — {Functional} {Biomimetics} {Inspired} by {Classical} {Conditioning}}, volume = {32}, doi = {10.1002/adma.201906619}, abstract = {Herein, it is discussed whether the complex biological concepts of (associative) learning can inspire responsive artificial materials. It is argued that classical conditioning, being one of the most elementary forms of learning, inspires algorithmic realizations in synthetic materials, to allow stimuli-responsive materials that learn to respond to a new stimulus, to which they are originally insensitive. Two synthetic model systems coined as “Pavlovian materials” are described, whose stimuli-responsiveness algorithmically mimics programmable associative learning, inspired by classical conditioning. The concepts minimally need a stimulus-triggerable memory, in addition to two stimuli, i.e., the unconditioned and the originally neutral stimuli. Importantly, the concept differs conceptually from the classic stimuli-responsive and shape-memory materials, as, upon association, Pavlovian materials obtain a given response using a new stimulus (the originally neutral one); i.e., the system evolves to a new state. This also enables the functionality to be described by a logic diagram. Ample room for generalization to different stimuli and memory combinations is foreseen, and opportunities to develop future adaptive materials with ever-more intelligent functions are expected.}, journal = {Advanced Materials}, author = {Zhang, Hang and Zeng, Hao and Priimagi, Arri and Ikkala, Olli}, month = may, year = {2020}, pages = {1906619}, } - A. Priimagi and S. Hecht, “From Responsive Molecules to Interactive Materials,” Advanced Materials, vol. 32, p. 2000215, 2020. doi:10.1002/adma.202000215
[BibTeX]@article{priimagi_responsive_2020, title = {From {Responsive} {Molecules} to {Interactive} {Materials}}, volume = {32}, doi = {10.1002/adma.202000215}, journal = {Advanced Materials}, author = {Priimagi, Arri and Hecht, Stefan}, month = may, year = {2020}, pages = {2000215}, } - H. Shahsavan, A. Aghakhani, H. Zeng, Y. Guo, Z. S. Davidson, A. Priimagi, and M. Sitti, “Bioinspired underwater locomotion of light-driven liquid crystal gels,” Proceedings of the National Academy of Sciences, vol. 117, pp. 5125-5133, 2020. doi:10.1073/pnas.1917952117
[BibTeX] [Abstract]
Soft-bodied aquatic invertebrates, such as sea slugs and snails, are capable of diverse locomotion modes under water. Recapitulation of such multimodal aquatic locomotion in small-scale soft robots is challenging, due to difficulties in precise spatiotemporal control of deformations and inefficient underwater actuation of existing stimuli-responsive materials. Solving this challenge and devising efficient untethered manipulation of soft stimuli-responsive materials in the aquatic environment would significantly broaden their application potential in biomedical devices. We mimic locomotion modes common to sea invertebrates using monolithic liquid crystal gels (LCGs) with inherent light responsiveness and molecular anisotropy. We elicit diverse underwater locomotion modes, such as crawling, walking, jumping, and swimming, by local deformations induced by selective spatiotemporal light illumination. Our results underpin the pivotal role of the physicomechanical properties of LCGs in the realization of diverse modes of light-driven robotic underwater locomotion. We envisage that our results will introduce a toolbox for designing efficient untethered soft robots for fluidic environments.
@article{shahsavan_bioinspired_2020, title = {Bioinspired underwater locomotion of light-driven liquid crystal gels}, volume = {117}, doi = {10.1073/pnas.1917952117}, abstract = {Soft-bodied aquatic invertebrates, such as sea slugs and snails, are capable of diverse locomotion modes under water. Recapitulation of such multimodal aquatic locomotion in small-scale soft robots is challenging, due to difficulties in precise spatiotemporal control of deformations and inefficient underwater actuation of existing stimuli-responsive materials. Solving this challenge and devising efficient untethered manipulation of soft stimuli-responsive materials in the aquatic environment would significantly broaden their application potential in biomedical devices. We mimic locomotion modes common to sea invertebrates using monolithic liquid crystal gels (LCGs) with inherent light responsiveness and molecular anisotropy. We elicit diverse underwater locomotion modes, such as crawling, walking, jumping, and swimming, by local deformations induced by selective spatiotemporal light illumination. Our results underpin the pivotal role of the physicomechanical properties of LCGs in the realization of diverse modes of light-driven robotic underwater locomotion. We envisage that our results will introduce a toolbox for designing efficient untethered soft robots for fluidic environments.}, journal = {Proceedings of the National Academy of Sciences}, author = {Shahsavan, Hamed and Aghakhani, Amirreza and Zeng, Hao and Guo, Yubing and Davidson, Zoey S. and Priimagi, Arri and Sitti, Metin}, month = mar, year = {2020}, pages = {5125--5133}, } - J. Salunke, A. Singh, D. He, H. D. Pham, Y. Bai, L. Wang, S. Dahlström, M. Nyman, S. Manzhos, K. Feron, R. Österbacka, A. Priimagi, P. Vivo, and P. Sonar, “Fluorination of pyrene-based organic semiconductors enhances the performance of light emitting diodes and halide perovskite solar cells,” Organic Electronics, vol. 77, p. 105524, 2020. doi:10.1016/j.orgel.2019.105524
[BibTeX] [Abstract]
In this work, a fluorinated pyrene-based organic semiconductor (L-F) has been designed and synthesized starting from a low-cost pyrene core functionalized with triphenilamine substituents at 1,3,6,8 positions (L-H), obtained via Suzuki coupling reactions. Its performance when used as green emitter in organic light emitting diodes (OLEDs) or as dopant-free hole-transporting material (HTM) in halide perovskite solar cells (PSCs) is higher than that of the L-H counterpart, in spite of its lower bulk hole-mobility (7.0 × 10−6 cm2/V) to L-H (1.9 × 10−4 cm2/V). In fact, the OLED devices based on a L-F active layer showed excellent green emission (brightness and current efficiency were 1759.8 cd/m2 and 3.7 cd/A, respectively) at a 4.5 V turn-on voltage. When the molecules were employed as a dopant-free HTM in PSCs, L-F led to a power conversion efficiency (PCE) and open circuit voltage (Voc) of 5.9\% and 1.07 V, respectively, thus outperforming those of corresponding devices based on L-H (PCE = 5.0\% and Voc = 0.87 V) under similar experimental conditions (AM 1.5G and 100 mW cm2). We attribute the enhancements of L-F-based optoelectronic devices (OLEDs and PSCs) to the observed better quality of the L-F films. The promising performance of L-F indicates that fluorination of small molecules can be an effective strategy to achieve low-cost and high-performing materials for energy harvesting and display-based organic electronic devices.
@article{salunke_fluorination_2020, title = {Fluorination of pyrene-based organic semiconductors enhances the performance of light emitting diodes and halide perovskite solar cells}, volume = {77}, doi = {10.1016/j.orgel.2019.105524}, abstract = {In this work, a fluorinated pyrene-based organic semiconductor (L-F) has been designed and synthesized starting from a low-cost pyrene core functionalized with triphenilamine substituents at 1,3,6,8 positions (L-H), obtained via Suzuki coupling reactions. Its performance when used as green emitter in organic light emitting diodes (OLEDs) or as dopant-free hole-transporting material (HTM) in halide perovskite solar cells (PSCs) is higher than that of the L-H counterpart, in spite of its lower bulk hole-mobility (7.0 × 10−6 cm2/V) to L-H (1.9 × 10−4 cm2/V). In fact, the OLED devices based on a L-F active layer showed excellent green emission (brightness and current efficiency were 1759.8 cd/m2 and 3.7 cd/A, respectively) at a 4.5 V turn-on voltage. When the molecules were employed as a dopant-free HTM in PSCs, L-F led to a power conversion efficiency (PCE) and open circuit voltage (Voc) of 5.9\% and 1.07 V, respectively, thus outperforming those of corresponding devices based on L-H (PCE = 5.0\% and Voc = 0.87 V) under similar experimental conditions (AM 1.5G and 100 mW cm2). We attribute the enhancements of L-F-based optoelectronic devices (OLEDs and PSCs) to the observed better quality of the L-F films. The promising performance of L-F indicates that fluorination of small molecules can be an effective strategy to achieve low-cost and high-performing materials for energy harvesting and display-based organic electronic devices.}, journal = {Organic Electronics}, author = {Salunke, Jagadish and Singh, Amandeep and He, Dongxu and Pham, Hong Duc and Bai, Yang and Wang, Lianzhou and Dahlström, Staffan and Nyman, Mathias and Manzhos, Sergei and Feron, Krishna and Österbacka, Ronald and Priimagi, Arri and Vivo, Paola and Sonar, Prashant}, month = feb, year = {2020}, pages = {105524}, } - Y. C. Cheng, H. C. Lu, X. Lee, H. Zeng, and A. Priimagi, “Kirigami-Based Light-Induced Shape-Morphing and Locomotion,” Advanced Materials, vol. 32, p. 1906233, 2020. doi:10.1002/adma.201906233
[BibTeX] [Abstract]
The development of stimuli-responsive soft actuators, a task largely undertaken by material scientists, has become a major driving force in pushing the frontiers of microrobotics. Devices made of soft active materials are oftentimes small in size, remotely and wirelessly powered/controlled, and capable of adapting themselves to unexpected hurdles. However, nowadays most soft microscale robots are rather simple in terms of design and architecture, and it remains a challenge to create complex 3D soft robots with stimuli-responsive properties. Here, it is suggested that kirigami-based techniques can be useful for fabricating complex 3D robotic structures that can be activated with light. External stress fields introduce out-of-plane deformation of kirigami film actuators made of liquid crystal networks. Such 2D-to-3D structural transformations can give rise to mechanical actuation upon light illumination, thus allowing the realization of kirigami-based light-fuelled robotics. A kirigami rolling robot is demonstrated, where a light beam controls the multigait motion and steers the moving direction in 2D. The device is able to navigate along different routes and moves up a ramp with a slope of 6\textbackslash,$^\textrm\textbackslashcirc$. The results demonstrate a facile technique to realize complex and flexible 3D structures with light-activated robotic functions.
@article{cheng_kirigami-based_2020, title = {Kirigami-{Based} {Light}-{Induced} {Shape}-{Morphing} and {Locomotion}}, volume = {32}, doi = {10.1002/adma.201906233}, abstract = {The development of stimuli-responsive soft actuators, a task largely undertaken by material scientists, has become a major driving force in pushing the frontiers of microrobotics. Devices made of soft active materials are oftentimes small in size, remotely and wirelessly powered/controlled, and capable of adapting themselves to unexpected hurdles. However, nowadays most soft microscale robots are rather simple in terms of design and architecture, and it remains a challenge to create complex 3D soft robots with stimuli-responsive properties. Here, it is suggested that kirigami-based techniques can be useful for fabricating complex 3D robotic structures that can be activated with light. External stress fields introduce out-of-plane deformation of kirigami film actuators made of liquid crystal networks. Such 2D-to-3D structural transformations can give rise to mechanical actuation upon light illumination, thus allowing the realization of kirigami-based light-fuelled robotics. A kirigami rolling robot is demonstrated, where a light beam controls the multigait motion and steers the moving direction in 2D. The device is able to navigate along different routes and moves up a ramp with a slope of 6{\textbackslash},$^{\textrm{{\textbackslash}circ}}$. The results demonstrate a facile technique to realize complex and flexible 3D structures with light-activated robotic functions.}, journal = {Advanced Materials}, author = {Cheng, Yu Chieh and Lu, Hao Chuan and Lee, Xuan and Zeng, Hao and Priimagi, Arri}, month = feb, year = {2020}, pages = {1906233}, } - H. Zeng, H. Zhang, O. Ikkala, and A. Priimagi, “Associative Learning by Classical Conditioning in Liquid Crystal Network Actuators,” Matter, vol. 2, pp. 194-206, 2020. doi:10.1016/j.matt.2019.10.019
[BibTeX] [Abstract]
Responsive and shape-memory materials allow stimuli-driven switching between fixed states. However, their behavior remains unchanged under repeated stimuli exposure, i.e., their properties do not evolve. By contrast, biological materials allow learning in response to past experiences. Classical conditioning is an elementary form of associative learning, which inspires us to explore simplified routes even for inanimate materials to respond to new, initially neutral stimuli. Here, we demonstrate that soft actuators composed of thermoresponsive liquid crystal networks “learn” to respond to light upon a conditioning process where light is associated with heating. We apply the concept to soft microrobotics, demonstrating a locomotive system that “learns to walk” under periodic light stimulus, and gripping devices able to “recognize” irradiation colors. We anticipate that actuators that algorithmically emulate elementary aspects of associative learning and whose sensitivity to new stimuli can be conditioned depending on past experiences may provide new routes toward adaptive, autonomous soft microrobotics.
@article{zeng_associative_2020, title = {Associative {Learning} by {Classical} {Conditioning} in {Liquid} {Crystal} {Network} {Actuators}}, volume = {2}, doi = {10.1016/j.matt.2019.10.019}, abstract = {Responsive and shape-memory materials allow stimuli-driven switching between fixed states. However, their behavior remains unchanged under repeated stimuli exposure, i.e., their properties do not evolve. By contrast, biological materials allow learning in response to past experiences. Classical conditioning is an elementary form of associative learning, which inspires us to explore simplified routes even for inanimate materials to respond to new, initially neutral stimuli. Here, we demonstrate that soft actuators composed of thermoresponsive liquid crystal networks “learn” to respond to light upon a conditioning process where light is associated with heating. We apply the concept to soft microrobotics, demonstrating a locomotive system that “learns to walk” under periodic light stimulus, and gripping devices able to “recognize” irradiation colors. We anticipate that actuators that algorithmically emulate elementary aspects of associative learning and whose sensitivity to new stimuli can be conditioned depending on past experiences may provide new routes toward adaptive, autonomous soft microrobotics.}, journal = {Matter}, author = {Zeng, Hao and Zhang, Hang and Ikkala, Olli and Priimagi, Arri}, month = jan, year = {2020}, pages = {194--206}, }
2019
- H. Zeng, M. Lahikainen, L. Liu, Z. Ahmed, O. M. Wani, M. Wang, H. Yang, and A. Priimagi, “Light-fuelled freestyle self-oscillators,” Nature Communications, vol. 10, p. 5057, 2019. doi:10.1038/s41467-019-13077-6
[BibTeX] [Abstract]
Self-oscillation is a phenomenon where an object sustains periodic motion upon non-periodic stimulus. It occurs commonly in nature, a few examples being heartbeat, sea waves and fluttering of leaves. Stimuli-responsive materials allow creating synthetic self-oscillators fuelled by different forms of energy, e.g. heat, light and chemicals, showing great potential for applications in power generation, autonomous mass transport, and self-propelled micro-robotics. However, most of the self-oscillators are based on bending deformation, thereby limiting their possibilities of being implemented in practical applications. Here, we report light-fuelled self-oscillators based on liquid crystal network actuators that can exhibit three basic oscillation modes: bending, twisting and contraction-expansion. We show that a time delay in material response dictates the self-oscillation dynamics, and realize a freestyle self-oscillator that combines numerous oscillation modes simultaneously by adjusting the excitation beam position. The results provide new insights into understanding of self-oscillation phenomenon and offer new designs for future self-propelling micro-robots.
@article{zeng_light-fuelled_2019, title = {Light-fuelled freestyle self-oscillators}, volume = {10}, doi = {10.1038/s41467-019-13077-6}, abstract = {Self-oscillation is a phenomenon where an object sustains periodic motion upon non-periodic stimulus. It occurs commonly in nature, a few examples being heartbeat, sea waves and fluttering of leaves. Stimuli-responsive materials allow creating synthetic self-oscillators fuelled by different forms of energy, e.g. heat, light and chemicals, showing great potential for applications in power generation, autonomous mass transport, and self-propelled micro-robotics. However, most of the self-oscillators are based on bending deformation, thereby limiting their possibilities of being implemented in practical applications. Here, we report light-fuelled self-oscillators based on liquid crystal network actuators that can exhibit three basic oscillation modes: bending, twisting and contraction-expansion. We show that a time delay in material response dictates the self-oscillation dynamics, and realize a freestyle self-oscillator that combines numerous oscillation modes simultaneously by adjusting the excitation beam position. The results provide new insights into understanding of self-oscillation phenomenon and offer new designs for future self-propelling micro-robots.}, journal = {Nature Communications}, author = {Zeng, Hao and Lahikainen, Markus and Liu, Li and Ahmed, Zafar and Wani, Owies M. and Wang, Meng and Yang, Hong and Priimagi, Arri}, month = dec, year = {2019}, pages = {5057}, } - H. Zhang, H. Zeng, A. Priimagi, and O. Ikkala, “Programmable responsive hydrogels inspired by classical conditioning algorithm,” Nature Communications, vol. 10, p. 3267, 2019. doi:10.1038/s41467-019-11260-3
[BibTeX] [Abstract]
Living systems have inspired research on non-biological dynamic materials and systems chemistry to mimic specific complex biological functions. Upon pursuing ever more complex life-inspired non-biological systems, mimicking even the most elementary aspects of learning is a grand challenge. We demonstrate a programmable hydrogel-based model system, whose behaviour is inspired by associative learning, i.e., conditioning, which is among the simplest forms of learning. Algorithmically, associative learning minimally requires responsivity to two different stimuli and a memory element. Herein, nanoparticles form the memory element, where a photoacid-driven pH-change leads to their chain-like assembly with a modified spectral behaviour. On associating selected light irradiation with heating, the gel starts to melt upon the irradiation, originally a neutral stimulus. A logic diagram describes such an evolution of the material response. Coupled chemical reactions drive the system out-of-equilibrium, allowing forgetting and memory recovery. The findings encourage to search non-biological materials towards associative and dynamic properties.
@article{zhang_programmable_2019, title = {Programmable responsive hydrogels inspired by classical conditioning algorithm}, volume = {10}, doi = {10.1038/s41467-019-11260-3}, abstract = {Living systems have inspired research on non-biological dynamic materials and systems chemistry to mimic specific complex biological functions. Upon pursuing ever more complex life-inspired non-biological systems, mimicking even the most elementary aspects of learning is a grand challenge. We demonstrate a programmable hydrogel-based model system, whose behaviour is inspired by associative learning, i.e., conditioning, which is among the simplest forms of learning. Algorithmically, associative learning minimally requires responsivity to two different stimuli and a memory element. Herein, nanoparticles form the memory element, where a photoacid-driven pH-change leads to their chain-like assembly with a modified spectral behaviour. On associating selected light irradiation with heating, the gel starts to melt upon the irradiation, originally a neutral stimulus. A logic diagram describes such an evolution of the material response. Coupled chemical reactions drive the system out-of-equilibrium, allowing forgetting and memory recovery. The findings encourage to search non-biological materials towards associative and dynamic properties.}, journal = {Nature Communications}, author = {Zhang, Hang and Zeng, Hao and Priimagi, Arri and Ikkala, Olli}, month = dec, year = {2019}, pages = {3267}, } - M. Saccone, M. Blanke, C. G. Daniliuc, H. Rekola, J. Stelzer, A. Priimagi, J. Voskuhl, and M. Giese, “Mesogens with Aggregation-Induced Emission Formed by Hydrogen Bonding,” ACS Materials Letters, vol. 1, pp. 589-593, 2019. doi:10.1021/acsmaterialslett.9b00371
[BibTeX] [Abstract]
In this contribution, we report a supra-molecular approach toward mesogens showing aggrega-tion-induced emission (AIE). AIE-active aromatic thio-ethers, acting as hydrogen-bond donors, were combined with alkoxystilbazoles as hydrogen-bond acceptors. Upon self-assembly, hydrogen-bonded complexes with mono-tropic liquid crystalline behavior were obtained. In addition, it was found that the introduction of a chiral citronellyl side chain leads to drastic bathochromic shift of the emission, which was not observed for linear alkyl chains. The mesomorphic behavior, as well as the photophysical properties as a solid and in the mesophase of the liquid crystalline assemblies, were studied in detail.
@article{saccone_mesogens_2019, title = {Mesogens with {Aggregation}-{Induced} {Emission} {Formed} by {Hydrogen} {Bonding}}, volume = {1}, doi = {10.1021/acsmaterialslett.9b00371}, abstract = {In this contribution, we report a supra-molecular approach toward mesogens showing aggrega-tion-induced emission (AIE). AIE-active aromatic thio-ethers, acting as hydrogen-bond donors, were combined with alkoxystilbazoles as hydrogen-bond acceptors. Upon self-assembly, hydrogen-bonded complexes with mono-tropic liquid crystalline behavior were obtained. In addition, it was found that the introduction of a chiral citronellyl side chain leads to drastic bathochromic shift of the emission, which was not observed for linear alkyl chains. The mesomorphic behavior, as well as the photophysical properties as a solid and in the mesophase of the liquid crystalline assemblies, were studied in detail.}, journal = {ACS Materials Letters}, author = {Saccone, Marco and Blanke, Meik and Daniliuc, Constantin G. and Rekola, Heikki and Stelzer, Jacqueline and Priimagi, Arri and Voskuhl, Jens and Giese, Michael}, month = nov, year = {2019}, pages = {589--593}, } - H. Zhang, M. Liu, W. Yang, L. Judin, T. I. Hukka, A. Priimagi, Z. Deng, and P. Vivo, “Thionation Enhances the Performance of Polymeric Dopant-Free Hole-Transporting Materials for Perovskite Solar Cells,” Advanced Materials Interfaces, vol. 6, p. 1901036, 2019. doi:10.1002/admi.201901036
[BibTeX] [Abstract]
To date, the most efficient perovskite solar cells (PSCs) require hole-transporting materials (HTMs) that are doped with hygroscopic additives to improve their performance. Unfortunately, such dopants negatively impact the overall PSCs stability and add cost and complexity to the device fabrication. Hence, there is a need to investigate new strategies to boost the typically modest performance of dopant-free HTMs for efficient and stable PSCs. Thionation is a simple and single-step approach to enhance the carrier-transport capability of organic semiconductors, yet still completely unexplored in the context of HTMs for PSCs. In this work, a novel polymeric semiconductor, P1, based on a diketopyrrolopyrrole (DPP) moiety, is proposed as a dopant-free HTM. Its modest performance in PSCs (power conversion efficiency (PCE) = 7.1\%) is significantly enhanced upon thionation of the DPP moiety. The resulting dithioketopyrrolopyrrole-based HTM, P2, leads to PSCs with nearly 40\% performance improvement (PCE = 9.7\%) compared to devices based on the nonthionated HTM (P1). Furthermore, thionation also remarkably boosts the shelf-storage and thermal stability with respect to traditional 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene-based PSCs. This work provides useful insights to further design effective dopant-free HTMs employing the straightforward one-step thionation strategy for efficient and stable PSCs.
@article{zhang_thionation_2019, title = {Thionation {Enhances} the {Performance} of {Polymeric} {Dopant}-{Free} {Hole}-{Transporting} {Materials} for {Perovskite} {Solar} {Cells}}, volume = {6}, doi = {10.1002/admi.201901036}, abstract = {To date, the most efficient perovskite solar cells (PSCs) require hole-transporting materials (HTMs) that are doped with hygroscopic additives to improve their performance. Unfortunately, such dopants negatively impact the overall PSCs stability and add cost and complexity to the device fabrication. Hence, there is a need to investigate new strategies to boost the typically modest performance of dopant-free HTMs for efficient and stable PSCs. Thionation is a simple and single-step approach to enhance the carrier-transport capability of organic semiconductors, yet still completely unexplored in the context of HTMs for PSCs. In this work, a novel polymeric semiconductor, P1, based on a diketopyrrolopyrrole (DPP) moiety, is proposed as a dopant-free HTM. Its modest performance in PSCs (power conversion efficiency (PCE) = 7.1\%) is significantly enhanced upon thionation of the DPP moiety. The resulting dithioketopyrrolopyrrole-based HTM, P2, leads to PSCs with nearly 40\% performance improvement (PCE = 9.7\%) compared to devices based on the nonthionated HTM (P1). Furthermore, thionation also remarkably boosts the shelf-storage and thermal stability with respect to traditional 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene-based PSCs. This work provides useful insights to further design effective dopant-free HTMs employing the straightforward one-step thionation strategy for efficient and stable PSCs.}, journal = {Advanced Materials Interfaces}, author = {Zhang, Haichang and Liu, Maning and Yang, Wenjun and Judin, Lauri and Hukka, Terttu I. and Priimagi, Arri and Deng, Zhifeng and Vivo, Paola}, month = sep, year = {2019}, pages = {1901036}, } - V. Y. Chang, C. Fedele, A. Priimagi, A. Shishido, and C. J. Barrett, “Photoreversible Soft Azo Dye Materials: Toward Optical Control of Bio-Interfaces,” Advanced Optical Materials, vol. 7, p. 1900091, 2019. doi:10.1002/adom.201900091
[BibTeX] [Abstract]
Photoreversible optically switchable azo dye molecules in polymer-based materials can be harnessed to control a wide range of physical, chemical, and mechanical material properties in response to light, that can be exploited for optical control over the bio-interface. As a stimulus for reversibly influencing adjacent biological cells or tissue, light is an ideal triggering mechanism, since it can be highly localized (in time and space) for precise and dynamic control over a biosystem, and low-power visible light is also an inherently gentle, benign, and nondamaging stimulus in a biological environment. Azobenzene-based dyes in particular are emerging as especially attractive candidates among photoreversible molecules, and soft azobenzene-containing materials are promising due to their ease of incorporation, and efficient and robust photochemistry and photophysics. This review provides a current survey of the use of photoreversible azo soft materials in cell biology and tissue engineering bio-interface applications, to afford light control over molecular motion (orientation, flow), by inscribing surface morphological patterns or macroscopically photoactuating surfaces and structures, via three key photophysical and bioactive effects enabled by the azo groups’ light-induced photo-orientation, topological optical patterning, and photomechanical actuation.
@article{chang_photoreversible_2019, title = {Photoreversible {Soft} {Azo} {Dye} {Materials}: {Toward} {Optical} {Control} of {Bio}-{Interfaces}}, volume = {7}, doi = {10.1002/adom.201900091}, abstract = {Photoreversible optically switchable azo dye molecules in polymer-based materials can be harnessed to control a wide range of physical, chemical, and mechanical material properties in response to light, that can be exploited for optical control over the bio-interface. As a stimulus for reversibly influencing adjacent biological cells or tissue, light is an ideal triggering mechanism, since it can be highly localized (in time and space) for precise and dynamic control over a biosystem, and low-power visible light is also an inherently gentle, benign, and nondamaging stimulus in a biological environment. Azobenzene-based dyes in particular are emerging as especially attractive candidates among photoreversible molecules, and soft azobenzene-containing materials are promising due to their ease of incorporation, and efficient and robust photochemistry and photophysics. This review provides a current survey of the use of photoreversible azo soft materials in cell biology and tissue engineering bio-interface applications, to afford light control over molecular motion (orientation, flow), by inscribing surface morphological patterns or macroscopically photoactuating surfaces and structures, via three key photophysical and bioactive effects enabled by the azo groups' light-induced photo-orientation, topological optical patterning, and photomechanical actuation.}, journal = {Advanced Optical Materials}, author = {Chang, Victoria Y. and Fedele, Chiara and Priimagi, Arri and Shishido, Atsushi and Barrett, Christopher J.}, month = aug, year = {2019}, pages = {1900091}, } - M. Liu, H. Zhang, D. Gedamu, P. Fourmont, H. Rekola, A. Hiltunen, S. G. Cloutier, R. Nechache, A. Priimagi, and P. Vivo, “Halide Perovskite Nanocrystals for Next-Generation Optoelectronics,” Small, vol. 15, p. 1900801, 2019. doi:10.1002/smll.201900801
[BibTeX] [Abstract]
Colloidal perovskite nanocrystals (PNCs) combine the outstanding optoelectronic properties of bulk perovskites with strong quantum confinement effects at the nanoscale. Their facile and low-cost synthesis, together with superior photoluminescence quantum yields and exceptional optical versatility, make PNCs promising candidates for next-generation optoelectronics. However, this field is still in its early infancy and not yet ready for commercialization due to several open challenges to be addressed, such as toxicity and stability. Here, the key synthesis strategies and the tunable optical properties of PNCs are discussed. The photophysical underpinnings of PNCs, in correlation with recent developments of PNC-based optoelectronic devices, are especially highlighted. The final goal is to outline a theoretical scaffold for the design of high-performance devices that can at the same time address the commercialization challenges of PNC-based technology.
@article{liu_halide_2019, title = {Halide {Perovskite} {Nanocrystals} for {Next}-{Generation} {Optoelectronics}}, volume = {15}, doi = {10.1002/smll.201900801}, abstract = {Colloidal perovskite nanocrystals (PNCs) combine the outstanding optoelectronic properties of bulk perovskites with strong quantum confinement effects at the nanoscale. Their facile and low-cost synthesis, together with superior photoluminescence quantum yields and exceptional optical versatility, make PNCs promising candidates for next-generation optoelectronics. However, this field is still in its early infancy and not yet ready for commercialization due to several open challenges to be addressed, such as toxicity and stability. Here, the key synthesis strategies and the tunable optical properties of PNCs are discussed. The photophysical underpinnings of PNCs, in correlation with recent developments of PNC-based optoelectronic devices, are especially highlighted. The final goal is to outline a theoretical scaffold for the design of high-performance devices that can at the same time address the commercialization challenges of PNC-based technology.}, journal = {Small}, author = {Liu, Maning and Zhang, Haichang and Gedamu, Dawit and Fourmont, Paul and Rekola, Heikki and Hiltunen, Arto and Cloutier, Sylvain G. and Nechache, Riad and Priimagi, Arri and Vivo, Paola}, month = jul, year = {2019}, pages = {1900801}, } - J. Vapaavuori, J. Grosrenaud, A. Siiskonen, A. Priimagi, C. Pellerin, and G. C. Bazuin, “Photocontrol of Supramolecular Azo-Containing Block Copolymer Thin Films during Dip-Coating: Toward Nanoscale Patterned Coatings,” ACS Applied Nano Materials, vol. 2, pp. 3526-3537, 2019. doi:10.1021/acsanm.9b00496
[BibTeX] [Abstract]
Dip-coating allows nanostructured block copolymer (BCP) thin film fabrication in a fast and facile one-step process. It can also be coupled with external controls, such as illumination. Herein, we expose several design principles that enable photocontrol of the nanostructured surface pattern and thickness of supramolecular BCP thin films. This is done using a polystyrene-poly(4-vinylpyridine) (PS-P4VP) BCP and two hydroxy-functionalized small-molecule (SM) azo derivatives that have different photochemical characteristics and that hydrogen bond to the P4VP block. We show how the film preparation concept provides tunability through the chemical structure of the photoactive SM, the relative amount of SM in the dip-coating solution, and the choice of solvent. It was found that the film thickness and SM uptake in the films are increased by illumination when THF is used but are unchanged when toluene is used as solvent, which is attributed to an optical heating effect observable with volatile solvents. The photocontrol of surface patterns is a result of photoinduced changes in the effective volume fraction of the P4VP+SM phase, which is increased by a greater volume of cis isomers, by higher SM uptake (using THF), and by more trans-cis-trans cycling for systems with shorter cis lifetime. The extent of photoinduced change can also be increased by higher molecular mobility due to more flexible SMs, lower BCP molecular weight, and nonmicellar or softer micellar solutions.
@article{vapaavuori_photocontrol_2019, title = {Photocontrol of {Supramolecular} {Azo}-{Containing} {Block} {Copolymer} {Thin} {Films} during {Dip}-{Coating}: {Toward} {Nanoscale} {Patterned} {Coatings}}, volume = {2}, doi = {10.1021/acsanm.9b00496}, abstract = {Dip-coating allows nanostructured block copolymer (BCP) thin film fabrication in a fast and facile one-step process. It can also be coupled with external controls, such as illumination. Herein, we expose several design principles that enable photocontrol of the nanostructured surface pattern and thickness of supramolecular BCP thin films. This is done using a polystyrene-poly(4-vinylpyridine) (PS-P4VP) BCP and two hydroxy-functionalized small-molecule (SM) azo derivatives that have different photochemical characteristics and that hydrogen bond to the P4VP block. We show how the film preparation concept provides tunability through the chemical structure of the photoactive SM, the relative amount of SM in the dip-coating solution, and the choice of solvent. It was found that the film thickness and SM uptake in the films are increased by illumination when THF is used but are unchanged when toluene is used as solvent, which is attributed to an optical heating effect observable with volatile solvents. The photocontrol of surface patterns is a result of photoinduced changes in the effective volume fraction of the P4VP+SM phase, which is increased by a greater volume of cis isomers, by higher SM uptake (using THF), and by more trans-cis-trans cycling for systems with shorter cis lifetime. The extent of photoinduced change can also be increased by higher molecular mobility due to more flexible SMs, lower BCP molecular weight, and nonmicellar or softer micellar solutions.}, journal = {ACS Applied Nano Materials}, author = {Vapaavuori, Jaana and Grosrenaud, Josué and Siiskonen, Antti and Priimagi, Arri and Pellerin, Christian and Bazuin, C. Geraldine}, month = jun, year = {2019}, pages = {3526--3537}, } - J. Salunke, X. Guo, Z. Lin, J. R. Vale, N. R. Candeias, M. Nyman, S. Dahlström, R. Österbacka, A. Priimagi, J. Chang, and P. Vivo, “Phenothiazine-Based Hole-Transporting Materials toward Eco-friendly Perovskite Solar Cells,” ACS Applied Energy Materials, vol. 2, pp. 3021-3027, 2019. doi:10.1021/acsaem.9b00408
[BibTeX] [Abstract]
Organic hole-transporting materials (HTMs), AZO-I and AZO-II, were synthesized via Schiff base chemistry by functionalizing a phenothiazine core with triarylamine(s) through azomethine bridges. Substantial enhancements in the power conversion efficiency (PCE = 12.6\% and 14\% for AZO-I and AZO-II, respectively) and stability (68\% or 91\% of PCE retained after 60 days for AZO-I or AZO-II, respectively) of perovskite solar cells (PSCs) were achieved when switching from mono-(AZO-I) to disubstituted (AZO-II) HTMs. The extremely low production costs (9 and 12 \$/g for AZO-I and AZO-II, respectively), together with the Pd-catalyst-free synthesis, make these materials excellent candidates for low-cost and eco-friendly PSCs.
@article{salunke_phenothiazine-based_2019, title = {Phenothiazine-{Based} {Hole}-{Transporting} {Materials} toward {Eco}-friendly {Perovskite} {Solar} {Cells}}, volume = {2}, doi = {10.1021/acsaem.9b00408}, abstract = {Organic hole-transporting materials (HTMs), AZO-I and AZO-II, were synthesized via Schiff base chemistry by functionalizing a phenothiazine core with triarylamine(s) through azomethine bridges. Substantial enhancements in the power conversion efficiency (PCE = 12.6\% and 14\% for AZO-I and AZO-II, respectively) and stability (68\% or 91\% of PCE retained after 60 days for AZO-I or AZO-II, respectively) of perovskite solar cells (PSCs) were achieved when switching from mono-(AZO-I) to disubstituted (AZO-II) HTMs. The extremely low production costs (9 and 12 \$/g for AZO-I and AZO-II, respectively), together with the Pd-catalyst-free synthesis, make these materials excellent candidates for low-cost and eco-friendly PSCs.}, journal = {ACS Applied Energy Materials}, author = {Salunke, Jagadish and Guo, Xing and Lin, Zhenhua and Vale, Joaõ R. and Candeias, Nuno R. and Nyman, Mathias and Dahlström, Staffan and Österbacka, Ronald and Priimagi, Arri and Chang, Jingjing and Vivo, Paola}, month = may, year = {2019}, pages = {3021--3027}, } - M. Shin, J. Kim, Y. K. Jung, T. petri Ruoko, A. Priimagi, A. Walsh, and B. Shin, “Low-dimensional formamidinium lead perovskite architectures via controllable solvent intercalation,” Journal of Materials Chemistry C, vol. 7, pp. 3945-3951, 2019. doi:10.1039/c9tc00379g
[BibTeX] [Abstract]
We report the formation of a new class of solvent-intercalated two-dimensional (SI-2D) formamidinium lead halide perovskites. They can be mixed with three-dimensional (3D) stoichiometric perovskites by controlling the ratio of the precursor solutions. The composite leads to greatly improved photoluminescence quantum yield (PLQY) over the 3D compound. The enhanced PLQY is attributed to a type-I band alignment between the 3D and SI-2D, as revealed by first-principles calculations, which results in confined excitons with enhanced radiative recombination. The films exhibited excellent thermal and air stability retaining PLQY \textbackslashtextgreater 20\% over 2 months in ambient conditions. Assemblies of halide perovskites with mixed dimensionality offer a pathway to enhance optoelectronic performance and device lifetimes.
@article{shin_low-dimensional_2019, title = {Low-dimensional formamidinium lead perovskite architectures via controllable solvent intercalation}, volume = {7}, doi = {10.1039/c9tc00379g}, abstract = {We report the formation of a new class of solvent-intercalated two-dimensional (SI-2D) formamidinium lead halide perovskites. They can be mixed with three-dimensional (3D) stoichiometric perovskites by controlling the ratio of the precursor solutions. The composite leads to greatly improved photoluminescence quantum yield (PLQY) over the 3D compound. The enhanced PLQY is attributed to a type-I band alignment between the 3D and SI-2D, as revealed by first-principles calculations, which results in confined excitons with enhanced radiative recombination. The films exhibited excellent thermal and air stability retaining PLQY {\textbackslash}textgreater 20\% over 2 months in ambient conditions. Assemblies of halide perovskites with mixed dimensionality offer a pathway to enhance optoelectronic performance and device lifetimes.}, journal = {Journal of Materials Chemistry C}, author = {Shin, Mingue and Kim, Joonyun and Jung, Young Kwang and petri Ruoko, Tero and Priimagi, Arri and Walsh, Aron and Shin, Byungha}, month = mar, year = {2019}, pages = {3945--3951}, } - M. Saccone, M. Spengler, M. Pfletscher, K. Kuntze, M. Virkki, C. Wölper, R. Gehrke, G. Jansen, P. Metrangolo, A. Priimagi, and M. Giese, “Photoresponsive Halogen-Bonded Liquid Crystals: The Role of Aromatic Fluorine Substitution,” Chemistry of Materials, vol. 31, pp. 462-470, 2019. doi:10.1021/acs.chemmater.8b04197
[BibTeX] [Abstract]
A new strategy for controlling the liquid crystalline and photophysical properties of supramolecular mesogens assembled via halogen bonding is reported. Changing the degree of fluorination at the halogen-bond donor of the supramolecular liquid crystal allows for the fine-tuning of the halogen bond strength and thereby provides control over the temperature range of the mesophase. At least three fluorine atoms have to be present to ensure efficient polarization of the halogen-bond donor and the formation of a mesophase. In addition, it was found that stilbazole acceptors are superior to their azopyridine counterparts in promoting stable liquid crystalline phases. The halogen-bond-driven supramolecular liquid crystals between fluorinated azobenzenes and stilbazole/azopyridine acceptors show a rich variety of photoinduced processes driven by azobenzene photoisomerization, dictated not only by the photochemical properties of the molecular components but also by the difference between the operation temperature and the clearing point.
@article{saccone_photoresponsive_2019, title = {Photoresponsive {Halogen}-{Bonded} {Liquid} {Crystals}: {The} {Role} of {Aromatic} {Fluorine} {Substitution}}, volume = {31}, doi = {10.1021/acs.chemmater.8b04197}, abstract = {A new strategy for controlling the liquid crystalline and photophysical properties of supramolecular mesogens assembled via halogen bonding is reported. Changing the degree of fluorination at the halogen-bond donor of the supramolecular liquid crystal allows for the fine-tuning of the halogen bond strength and thereby provides control over the temperature range of the mesophase. At least three fluorine atoms have to be present to ensure efficient polarization of the halogen-bond donor and the formation of a mesophase. In addition, it was found that stilbazole acceptors are superior to their azopyridine counterparts in promoting stable liquid crystalline phases. The halogen-bond-driven supramolecular liquid crystals between fluorinated azobenzenes and stilbazole/azopyridine acceptors show a rich variety of photoinduced processes driven by azobenzene photoisomerization, dictated not only by the photochemical properties of the molecular components but also by the difference between the operation temperature and the clearing point.}, journal = {Chemistry of Materials}, author = {Saccone, Marco and Spengler, Matthias and Pfletscher, Michael and Kuntze, Kim and Virkki, Matti and Wölper, Christoph and Gehrke, Robert and Jansen, Georg and Metrangolo, Pierangelo and Priimagi, Arri and Giese, Michael}, month = jan, year = {2019}, pages = {462--470}, } - O. M. Wani, R. Verpaalen, H. Zeng, A. Priimagi, and A. P. H. J. Schenning, “An Artificial Nocturnal Flower via Humidity-Gated Photoactuation in Liquid Crystal Networks,” Advanced Materials, vol. 31, p. 1805985, 2019. doi:10.1002/adma.201805985
[BibTeX] [Abstract]
Beyond their colorful appearances and versatile geometries, flowers can self-shape-morph by adapting to environmental changes. Such responses are often regulated by a delicate interplay between different stimuli such as temperature, light, and humidity, giving rise to the beauty and complexity of the plant kingdom. Nature inspires scientists to realize artificial systems that mimic their natural counterparts in function, flexibility, and adaptation. Yet, many of the artificial systems demonstrated to date fail to mimic the adaptive functions, due to the lack of multi-responsivity and sophisticated control over deformation directionality. Herein, a new class of liquid-crystal-network (LCN) photoactuators whose response is controlled by delicate interplay between light and humidity is presented. Using a novel deformation mechanism in LCNs, humidity-gated photoactuation, an artificial nocturnal flower is devised that is closed under daylight conditions when the humidity level is low and/or the light level is high, while it opens in the dark when the humidity level is high. The humidity-gated photoactuators can be fueled with lower light intensities than conventional photothermal LCN actuators. This, combined with facile control over the speed, geometry, and directionality of movements, renders the “nocturnal actuator” promising for smart and adaptive bioinspired microrobotics.
@article{wani_artificial_2019, title = {An {Artificial} {Nocturnal} {Flower} via {Humidity}-{Gated} {Photoactuation} in {Liquid} {Crystal} {Networks}}, volume = {31}, doi = {10.1002/adma.201805985}, abstract = {Beyond their colorful appearances and versatile geometries, flowers can self-shape-morph by adapting to environmental changes. Such responses are often regulated by a delicate interplay between different stimuli such as temperature, light, and humidity, giving rise to the beauty and complexity of the plant kingdom. Nature inspires scientists to realize artificial systems that mimic their natural counterparts in function, flexibility, and adaptation. Yet, many of the artificial systems demonstrated to date fail to mimic the adaptive functions, due to the lack of multi-responsivity and sophisticated control over deformation directionality. Herein, a new class of liquid-crystal-network (LCN) photoactuators whose response is controlled by delicate interplay between light and humidity is presented. Using a novel deformation mechanism in LCNs, humidity-gated photoactuation, an artificial nocturnal flower is devised that is closed under daylight conditions when the humidity level is low and/or the light level is high, while it opens in the dark when the humidity level is high. The humidity-gated photoactuators can be fueled with lower light intensities than conventional photothermal LCN actuators. This, combined with facile control over the speed, geometry, and directionality of movements, renders the “nocturnal actuator” promising for smart and adaptive bioinspired microrobotics.}, journal = {Advanced Materials}, author = {Wani, Owies M. and Verpaalen, Rob and Zeng, Hao and Priimagi, Arri and Schenning, Albert P.H.J.}, month = jan, year = {2019}, pages = {1805985}, } - H. Zeng, M. Lahikainen, O. M. Wani, A. Berdin, and A. Priimagi, “Liquid Crystal Polymer Networks and Elastomers for Light‐Fueled Robotics,” in Photoactive Functional Soft Materials, E. Q. Li, Ed., Wiley, 2019, pp. 197-226. doi:10.1002/9783527816774.ch6
[BibTeX] [Abstract] [Download PDF]
Summary Liquid crystal (LC) polymer networks and elastomers are synthetic cross-linked polymer systems constituting liquid crystalline building blocks, or mesogens. This chapter provides an up-to-date overview of light- fueled LC network (LCN) robotics. It explains photoactuation and light robotics, and discusses the basic physics that a small-scale LCN robot encounters, as the forces at the microscale are very different from common everyday experience. The chapter also introduces the photoactuation mechanisms, making a comparison between photothermal and photochemical actuation strategies, which often times yield distinct actuation behavior and shape changes. Azobenzene-based photochemical actuators often times exhibit photoinduced bending as opposed to in-plane photocontraction. The chapter considers autonomous actuation, driven by dynamic light-response in the material, to adopt a significant role in the design of future LCN robots. Uniaxially aligned LCNs can undergo reversible contraction-expansion along the molecular director axis, thus presenting muscle-like motion under external stimulus.
@incollection{zeng_liquid_2019, title = {Liquid {Crystal} {Polymer} {Networks} and {Elastomers} for {Light}‐{Fueled} {Robotics}}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/9783527816774.ch6}, abstract = {Summary Liquid crystal (LC) polymer networks and elastomers are synthetic cross-linked polymer systems constituting liquid crystalline building blocks, or mesogens. This chapter provides an up-to-date overview of light- fueled LC network (LCN) robotics. It explains photoactuation and light robotics, and discusses the basic physics that a small-scale LCN robot encounters, as the forces at the microscale are very different from common everyday experience. The chapter also introduces the photoactuation mechanisms, making a comparison between photothermal and photochemical actuation strategies, which often times yield distinct actuation behavior and shape changes. Azobenzene-based photochemical actuators often times exhibit photoinduced bending as opposed to in-plane photocontraction. The chapter considers autonomous actuation, driven by dynamic light-response in the material, to adopt a significant role in the design of future LCN robots. Uniaxially aligned LCNs can undergo reversible contraction-expansion along the molecular director axis, thus presenting muscle-like motion under external stimulus.}, booktitle = {Photoactive {Functional} {Soft} {Materials}}, publisher = {Wiley}, author = {Zeng, Hao and Lahikainen, Markus and Wani, Owies M. and Berdin, Alex and Priimagi, Arri}, editor = {Li, Ed Quan}, month = jan, year = {2019}, doi = {10.1002/9783527816774.ch6}, pages = {197--226}, }
2018
- M. Lahikainen, H. Zeng, and A. Priimagi, “Reconfigurable photoactuator through synergistic use of photochemical and photothermal effects,” Nature Communications, vol. 9, p. 4148, 2018. doi:10.1038/s41467-018-06647-7
[BibTeX] [Abstract]
A reconfigurable actuator is a stimuli-responsive structure that can be programmed to adapt different shapes under identical stimulus. Reconfigurable actuators that function without control circuitry and are fueled remotely are in great demand to devise adaptive soft robotic devices. Yet, obtaining fast and reliable reconfiguration remains a grand challenge. Here we report a facile fabrication pathway towards reconfigurability, through synergistic use of photochemical and photothermal responses in light-active liquid crystal polymer networks. We utilize azobenzene photoisomerization to locally control the cis-isomer content and to program the actuator response, while subsequent photothermal stimulus actuates the structure, leading to shape morphing. We demonstrate six different shapes reconfigured from one single actuator under identical illumination conditions, and a light-fueled smart gripper that can be commanded to either grip and release or grip and hold an object after ceasing the illumination. We anticipate this work to enable all-optical control over actuator performance, paving way towards reprogrammable soft micro-robotics.
@article{lahikainen_reconfigurable_2018, title = {Reconfigurable photoactuator through synergistic use of photochemical and photothermal effects}, volume = {9}, doi = {10.1038/s41467-018-06647-7}, abstract = {A reconfigurable actuator is a stimuli-responsive structure that can be programmed to adapt different shapes under identical stimulus. Reconfigurable actuators that function without control circuitry and are fueled remotely are in great demand to devise adaptive soft robotic devices. Yet, obtaining fast and reliable reconfiguration remains a grand challenge. Here we report a facile fabrication pathway towards reconfigurability, through synergistic use of photochemical and photothermal responses in light-active liquid crystal polymer networks. We utilize azobenzene photoisomerization to locally control the cis-isomer content and to program the actuator response, while subsequent photothermal stimulus actuates the structure, leading to shape morphing. We demonstrate six different shapes reconfigured from one single actuator under identical illumination conditions, and a light-fueled smart gripper that can be commanded to either grip and release or grip and hold an object after ceasing the illumination. We anticipate this work to enable all-optical control over actuator performance, paving way towards reprogrammable soft micro-robotics.}, journal = {Nature Communications}, author = {Lahikainen, Markus and Zeng, Hao and Priimagi, Arri}, month = dec, year = {2018}, pages = {4148}, } - J. K. Salunke, N. A. Durandin, T. P. Ruoko, N. R. Candeias, P. Vivo, E. Vuorimaa-Laukkanen, T. Laaksonen, and A. Priimagi, “Halogen-Bond-Assisted Photoluminescence Modulation in Carbazole-Based Emitter,” Scientific Reports, vol. 8, p. 14431, 2018. doi:10.1038/s41598-018-32830-3
[BibTeX] [Abstract]
Halogen bonding between a carbazole-based, pyridine-substituted organic semiconductor and a common halogen-bond donor (pentafluoroiodobenzene) yields efficient halogen-bond-driven fluorescence modulation in solution. Steady-state, time-resolved emission and absorption spectroscopy as well as density functional theory studies demonstrate that the fluorescence modulation arises from halogen-bond-induced intramolecular charge transfer. Fluorescence modulation offers a range of possibilities both in solution and in the solid state, for instance providing a potential pathway for the design of tunable luminescent materials for light-emitting devices.
@article{salunke_halogen-bond-assisted_2018, title = {Halogen-{Bond}-{Assisted} {Photoluminescence} {Modulation} in {Carbazole}-{Based} {Emitter}}, volume = {8}, doi = {10.1038/s41598-018-32830-3}, abstract = {Halogen bonding between a carbazole-based, pyridine-substituted organic semiconductor and a common halogen-bond donor (pentafluoroiodobenzene) yields efficient halogen-bond-driven fluorescence modulation in solution. Steady-state, time-resolved emission and absorption spectroscopy as well as density functional theory studies demonstrate that the fluorescence modulation arises from halogen-bond-induced intramolecular charge transfer. Fluorescence modulation offers a range of possibilities both in solution and in the solid state, for instance providing a potential pathway for the design of tunable luminescent materials for light-emitting devices.}, journal = {Scientific Reports}, author = {Salunke, Jagadish K. and Durandin, Nikita A. and Ruoko, Tero Petri and Candeias, Nuno R. and Vivo, Paola and Vuorimaa-Laukkanen, Elina and Laaksonen, Timo and Priimagi, Arri}, month = dec, year = {2018}, pages = {14431}, } - M. Virkki, A. Maurice, A. Forni, M. Sironi, V. Dichiarante, P. F. Brevet, P. Metrangolo, M. Kauranen, and A. Priimagi, “On the molecular optical nonlinearity of halogen-bond-forming azobenzenes,” Physical Chemistry Chemical Physics, vol. 20, pp. 28810-28817, 2018. doi:10.1039/c8cp05392h
[BibTeX] [Abstract]
We study hyper-Rayleigh scattering and computed molecular hyperpolarizability in a series of azobenzene chromophores in chloroform and dimethylformamide as solvents. The chromophores form halogen or hydrogen bonds of varying strength with dimethylformamide molecules, differently from what is expected for chloroform. We show that hyperpolarizability is unaffected or sligthly lower with the azobenzene forming the strongest halogen bond. Solid supramolecular polymers with the same chromophores have previously demonstrated clearly higher second-order nonlinear responses when a halogen-bond-accepting polymer is used, the larger increase being associated with the stronger halogen bond. The present study proves that the higher optical nonlinearity in polymers lies in the better ordering of the chromophores instead of changes in molecular hyperpolarizability, highlighting the unique properties of halogen bonding in supramolecular chemistry.
@article{virkki_molecular_2018, title = {On the molecular optical nonlinearity of halogen-bond-forming azobenzenes}, volume = {20}, doi = {10.1039/c8cp05392h}, abstract = {We study hyper-Rayleigh scattering and computed molecular hyperpolarizability in a series of azobenzene chromophores in chloroform and dimethylformamide as solvents. The chromophores form halogen or hydrogen bonds of varying strength with dimethylformamide molecules, differently from what is expected for chloroform. We show that hyperpolarizability is unaffected or sligthly lower with the azobenzene forming the strongest halogen bond. Solid supramolecular polymers with the same chromophores have previously demonstrated clearly higher second-order nonlinear responses when a halogen-bond-accepting polymer is used, the larger increase being associated with the stronger halogen bond. The present study proves that the higher optical nonlinearity in polymers lies in the better ordering of the chromophores instead of changes in molecular hyperpolarizability, highlighting the unique properties of halogen bonding in supramolecular chemistry.}, journal = {Physical Chemistry Chemical Physics}, author = {Virkki, Matti and Maurice, Anthony and Forni, Alessandra and Sironi, Maurizio and Dichiarante, Valentina and Brevet, Pierre Francois and Metrangolo, Pierangelo and Kauranen, Martti and Priimagi, Arri}, month = oct, year = {2018}, pages = {28810--28817}, } - M. Saccone, K. Kuntze, Z. Ahmed, A. Siiskonen, M. Giese, and A. Priimagi, “Ortho-Fluorination of azophenols increases the mesophase stability of photoresponsive hydrogen-bonded liquid crystals,” Journal of Materials Chemistry C, vol. 6, pp. 9958-9963, 2018. doi:10.1039/c8tc02611d
[BibTeX] [Abstract]
Photoresponsive liquid crystals (LCs) whose alignment can be controlled with UV-Visible light are appealing for a range of photonic applications. From the perspective of exploring the interplay between the light response and the self-assembly of the molecular components, supramolecular liquid crystals are of particular interest. They allow elaborating the structure-property relationships that govern the optical performance of LC materials by subtle variation of the chemical structures of the building blocks. Herein we present a supramolecular system comprising azophenols and stilbazoles as hydrogen-bond donors and acceptors, respectively, and show that ortho-fluorination of the azophenol dramatically increases the thermal stability of the LC phases, an important characteristics in their further utilization in photonics. The systems exhibit fast photoinduced order-disorder transitions, and rapid recovery of the liquid-crystalline state once the light irradiation is ceased, due to the photochemical properties of azophenols.
@article{saccone_ortho-fluorination_2018, title = {Ortho-{Fluorination} of azophenols increases the mesophase stability of photoresponsive hydrogen-bonded liquid crystals}, volume = {6}, doi = {10.1039/c8tc02611d}, abstract = {Photoresponsive liquid crystals (LCs) whose alignment can be controlled with UV-Visible light are appealing for a range of photonic applications. From the perspective of exploring the interplay between the light response and the self-assembly of the molecular components, supramolecular liquid crystals are of particular interest. They allow elaborating the structure-property relationships that govern the optical performance of LC materials by subtle variation of the chemical structures of the building blocks. Herein we present a supramolecular system comprising azophenols and stilbazoles as hydrogen-bond donors and acceptors, respectively, and show that ortho-fluorination of the azophenol dramatically increases the thermal stability of the LC phases, an important characteristics in their further utilization in photonics. The systems exhibit fast photoinduced order-disorder transitions, and rapid recovery of the liquid-crystalline state once the light irradiation is ceased, due to the photochemical properties of azophenols.}, journal = {Journal of Materials Chemistry C}, author = {Saccone, Marco and Kuntze, Kim and Ahmed, Zafar and Siiskonen, Antti and Giese, Michael and Priimagi, Arri}, month = aug, year = {2018}, pages = {9958--9963}, } - H. Zeng, P. Wasylczyk, D. S. Wiersma, and A. Priimagi, “Light Robots: Bridging the Gap between Microrobotics and Photomechanics in Soft Materials,” Advanced Materials, vol. 30, p. 1703554, 2018. doi:10.1002/adma.201703554
[BibTeX] [Abstract]
For decades, roboticists have focused their efforts on rigid systems that enable programmable, automated action, and sophisticated control with maximal movement precision and speed. Meanwhile, material scientists have sought compounds and fabrication strategies to devise polymeric actuators that are small, soft, adaptive, and stimuli-responsive. Merging these two fields has given birth to a new class of devices—soft microrobots that, by combining concepts from microrobotics and stimuli-responsive materials research, provide several advantages in a miniature form: external, remotely controllable power supply, adaptive motion, and human-friendly interaction, with device design and action often inspired by biological systems. Herein, recent progress in soft microrobotics is highlighted based on light-responsive liquid-crystal elastomers and polymer networks, focusing on photomobile devices such as walkers, swimmers, and mechanical oscillators, which may ultimately lead to flying microrobots. Finally, self-regulated actuation is proposed as a new pathway toward fully autonomous, intelligent light robots of the future.
@article{zeng_light_2018, title = {Light {Robots}: {Bridging} the {Gap} between {Microrobotics} and {Photomechanics} in {Soft} {Materials}}, volume = {30}, doi = {10.1002/adma.201703554}, abstract = {For decades, roboticists have focused their efforts on rigid systems that enable programmable, automated action, and sophisticated control with maximal movement precision and speed. Meanwhile, material scientists have sought compounds and fabrication strategies to devise polymeric actuators that are small, soft, adaptive, and stimuli-responsive. Merging these two fields has given birth to a new class of devices—soft microrobots that, by combining concepts from microrobotics and stimuli-responsive materials research, provide several advantages in a miniature form: external, remotely controllable power supply, adaptive motion, and human-friendly interaction, with device design and action often inspired by biological systems. Herein, recent progress in soft microrobotics is highlighted based on light-responsive liquid-crystal elastomers and polymer networks, focusing on photomobile devices such as walkers, swimmers, and mechanical oscillators, which may ultimately lead to flying microrobots. Finally, self-regulated actuation is proposed as a new pathway toward fully autonomous, intelligent light robots of the future.}, journal = {Advanced Materials}, author = {Zeng, Hao and Wasylczyk, Piotr and Wiersma, Diederik S. and Priimagi, Arri}, month = jun, year = {2018}, pages = {1703554}, } - P. M. J. Szell, A. Siiskonen, L. Catalano, G. Cavallo, G. Terraneo, A. Priimagi, D. L. Bryce, and P. Metrangolo, “Halogen-bond driven self-assembly of triangular macrocycles,” New Journal of Chemistry, vol. 42, pp. 10467-10471, 2018. doi:10.1039/c8nj00759d
[BibTeX] [Abstract]
2-Iodoethynylpyridine and 2-iodoethynyl-1-methyl-imidazole self-assemble under halogen-bonding control into discrete macrocycles, viz. supramolecular triangles.
@article{szell_halogen-bond_2018, title = {Halogen-bond driven self-assembly of triangular macrocycles}, volume = {42}, doi = {10.1039/c8nj00759d}, abstract = {2-Iodoethynylpyridine and 2-iodoethynyl-1-methyl-imidazole self-assemble under halogen-bonding control into discrete macrocycles, viz. supramolecular triangles.}, journal = {New Journal of Chemistry}, author = {Szell, Patrick M.J. and Siiskonen, Antti and Catalano, Luca and Cavallo, Gabriella and Terraneo, Giancarlo and Priimagi, Arri and Bryce, David L. and Metrangolo, Pierangelo}, month = mar, year = {2018}, pages = {10467--10471}, } - M. Poutanen, Z. Ahmed, L. Rautkari, O. Ikkala, and A. Priimagi, “Thermal Isomerization of Hydroxyazobenzenes as a Platform for Vapor Sensing,” ACS Macro Letters, vol. 7, pp. 381-386, 2018. doi:10.1021/acsmacrolett.8b00093
[BibTeX] [Abstract]
Photoisomerization of azobenzene derivatives is a versatile tool for devising light-responsive materials for a broad range of applications in photonics, robotics, microfabrication, and biomaterials science. Some applications rely on fast isomerization kinetics, while for others, bistable azobenzenes are preferred. However, solid-state materials where the isomerization kinetics depends on the environmental conditions have been largely overlooked. Herein, an approach to utilize the environmental sensitivity of isomerization kinetics is developed. It is demonstrated that thin polymer films containing hydroxyazobenzenes offer a conceptually novel platform for sensing hydrogen-bonding vapors in the environment. The concept is based on accelerating the thermal cis-trans isomerization rate through hydrogen-bond-catalyzed changes in the thermal isomerization pathway, which allows for devising a relative humidity sensor with high sensitivity and quick response to relative humidity changes. The approach is also applicable for detecting other hydrogen-bonding vapors such as methanol and ethanol. Employing isomerization kinetics of azobenzenes for vapor sensing opens new intriguing possibilities for using azobenzene molecules in the future.
@article{poutanen_thermal_2018, title = {Thermal {Isomerization} of {Hydroxyazobenzenes} as a {Platform} for {Vapor} {Sensing}}, volume = {7}, doi = {10.1021/acsmacrolett.8b00093}, abstract = {Photoisomerization of azobenzene derivatives is a versatile tool for devising light-responsive materials for a broad range of applications in photonics, robotics, microfabrication, and biomaterials science. Some applications rely on fast isomerization kinetics, while for others, bistable azobenzenes are preferred. However, solid-state materials where the isomerization kinetics depends on the environmental conditions have been largely overlooked. Herein, an approach to utilize the environmental sensitivity of isomerization kinetics is developed. It is demonstrated that thin polymer films containing hydroxyazobenzenes offer a conceptually novel platform for sensing hydrogen-bonding vapors in the environment. The concept is based on accelerating the thermal cis-trans isomerization rate through hydrogen-bond-catalyzed changes in the thermal isomerization pathway, which allows for devising a relative humidity sensor with high sensitivity and quick response to relative humidity changes. The approach is also applicable for detecting other hydrogen-bonding vapors such as methanol and ethanol. Employing isomerization kinetics of azobenzenes for vapor sensing opens new intriguing possibilities for using azobenzene molecules in the future.}, journal = {ACS Macro Letters}, author = {Poutanen, Mikko and Ahmed, Zafar and Rautkari, Lauri and Ikkala, Olli and Priimagi, Arri}, month = mar, year = {2018}, pages = {381--386}, } - O. M. Wani, H. Zeng, P. Wasylczyk, and A. Priimagi, “Programming Photoresponse in Liquid Crystal Polymer Actuators with Laser Projector,” Advanced Optical Materials, vol. 6, p. 1700949, 2018. doi:10.1002/adom.201700949
[BibTeX] [Abstract]
A versatile, laser-projector-based method is demonstrated for programming alignment patterns into monolithic films of liquid crystal polymer networks. Complex images can be photopatterned into the polymer films with sub-100 µm resolution, using relatively short exposure times. The method is further used to devise both photochemically and photothermally driven actuators that can undergo distinct light-induced shape changes, dictated by the programmed alignment patterns. Deformation modes such as buckling and coiling, as well as miniature robotic devices such as a gripper and a light-responsive octopod, are demonstrated. The reported technique enables easy and cost-effective programmable actuation with relatively high throughput, thus significantly facilitating the design and realization of functional soft robotic actuators.
@article{wani_programming_2018, title = {Programming {Photoresponse} in {Liquid} {Crystal} {Polymer} {Actuators} with {Laser} {Projector}}, volume = {6}, doi = {10.1002/adom.201700949}, abstract = {A versatile, laser-projector-based method is demonstrated for programming alignment patterns into monolithic films of liquid crystal polymer networks. Complex images can be photopatterned into the polymer films with sub-100 µm resolution, using relatively short exposure times. The method is further used to devise both photochemically and photothermally driven actuators that can undergo distinct light-induced shape changes, dictated by the programmed alignment patterns. Deformation modes such as buckling and coiling, as well as miniature robotic devices such as a gripper and a light-responsive octopod, are demonstrated. The reported technique enables easy and cost-effective programmable actuation with relatively high throughput, thus significantly facilitating the design and realization of functional soft robotic actuators.}, journal = {Advanced Optical Materials}, author = {Wani, Owies M. and Zeng, Hao and Wasylczyk, Piotr and Priimagi, Arri}, month = jan, year = {2018}, pages = {1700949}, } - H. Zeng, O. M. Wani, P. Wasylczyk, and A. Priimagi, “Light-Driven, Caterpillar-Inspired Miniature Inching Robot,” Macromolecular Rapid Communications, vol. 39, p. 1700224, 2018. doi:10.1002/marc.201700224
[BibTeX] [Abstract]
Liquid crystal elastomers are among the best candidates for artificial muscles, and the materials of choice when constructing microscale robotic systems. Recently, significant efforts are dedicated to designing stimuli-responsive actuators that can reproduce the shape-change of soft bodies of animals by means of proper external energy source. However, transferring material deformation efficiently into autonomous robotic locomotion remains a challenge. This paper reports on a miniature inching robot fabricated from a monolithic liquid crystal elastomer film, which upon visible-light excitation is capable of mimicking caterpillar locomotion on different substrates like a blazed grating and a paper surface. The motion is driven by spatially uniform visible light with relatively low intensity, rendering the robot “human-friendly,” i.e., operational also on human skin. The design paves the way toward light-driven, soft, mobile microdevices capable of operating in various environments, including the close proximity of humans.
@article{zeng_light-driven_2018, title = {Light-{Driven}, {Caterpillar}-{Inspired} {Miniature} {Inching} {Robot}}, volume = {39}, doi = {10.1002/marc.201700224}, abstract = {Liquid crystal elastomers are among the best candidates for artificial muscles, and the materials of choice when constructing microscale robotic systems. Recently, significant efforts are dedicated to designing stimuli-responsive actuators that can reproduce the shape-change of soft bodies of animals by means of proper external energy source. However, transferring material deformation efficiently into autonomous robotic locomotion remains a challenge. This paper reports on a miniature inching robot fabricated from a monolithic liquid crystal elastomer film, which upon visible-light excitation is capable of mimicking caterpillar locomotion on different substrates like a blazed grating and a paper surface. The motion is driven by spatially uniform visible light with relatively low intensity, rendering the robot “human-friendly,” i.e., operational also on human skin. The design paves the way toward light-driven, soft, mobile microdevices capable of operating in various environments, including the close proximity of humans.}, journal = {Macromolecular Rapid Communications}, author = {Zeng, Hao and Wani, Owies M. and Wasylczyk, Piotr and Priimagi, Arri}, month = jan, year = {2018}, pages = {1700224}, } - J. Vapaavuori, G. C. Bazuin, and A. Priimagi, “Supramolecular design principles for efficient photoresponsive polymer-azobenzene complexes,” Journal of Materials Chemistry C, vol. 6, pp. 2168-2188, 2018. doi:10.1039/c7tc05005d
[BibTeX] [Abstract]
Noncovalent binding of azobenzenes to polymers allows harnessing light-induced molecular-level motions (photoisomerization) for inducing macroscopic effects, including photocontrol over molecular alignment and self-assembly of block copolymer nanostructures, and photoinduced surface patterning of polymeric thin films. In the last 10 years, a growing body of literature has proven the utility of supramolecular materials design for establishing structure-property-function guidelines for photoresponsive azobenzene-based polymeric materials. In general, the bond type and strength, engineered by the choice of the polymer and the azobenzene, influence the photophysical properties and the optical response of the material system. Herein, we review this progress, and critically assess the advantages and disadvantages of the three most commonly used supramolecular design strategies: hydrogen, halogen and ionic bonding. The ease and versatility of the design of these photoresponsive materials makes a compelling case for a paradigm shift from covalently-functionalized side-chain polymers to supramolecular polymer-azobenzene complexes.
@article{vapaavuori_supramolecular_2018, title = {Supramolecular design principles for efficient photoresponsive polymer-azobenzene complexes}, volume = {6}, doi = {10.1039/c7tc05005d}, abstract = {Noncovalent binding of azobenzenes to polymers allows harnessing light-induced molecular-level motions (photoisomerization) for inducing macroscopic effects, including photocontrol over molecular alignment and self-assembly of block copolymer nanostructures, and photoinduced surface patterning of polymeric thin films. In the last 10 years, a growing body of literature has proven the utility of supramolecular materials design for establishing structure-property-function guidelines for photoresponsive azobenzene-based polymeric materials. In general, the bond type and strength, engineered by the choice of the polymer and the azobenzene, influence the photophysical properties and the optical response of the material system. Herein, we review this progress, and critically assess the advantages and disadvantages of the three most commonly used supramolecular design strategies: hydrogen, halogen and ionic bonding. The ease and versatility of the design of these photoresponsive materials makes a compelling case for a paradigm shift from covalently-functionalized side-chain polymers to supramolecular polymer-azobenzene complexes.}, journal = {Journal of Materials Chemistry C}, author = {Vapaavuori, Jaana and Bazuin, C. Geraldine and Priimagi, Arri}, year = {2018}, pages = {2168--2188}, }
2017
- Z. Ahmed, A. Siiskonen, M. Virkki, and A. Priimagi, “Controlling azobenzene photoswitching through combined: Ortho -fluorination and -amination,” Chemical Communications, vol. 53, pp. 12520-12523, 2017. doi:10.1039/c7cc07308a
[BibTeX] [Abstract]
We present a series of visible-light-absorbing azobenzene photoswitches with cis-lifetimes ranging from one second to three days. We combine ortho-fluorination to control the cis-lifetimes, and ortho-amination to boost the visible-light absorption. The synthesis is accomplished by selectively replacing one or more ortho-fluorines with amines in the ortho-fluoroazobenzene precursors.
@article{ahmed_controlling_2017, title = {Controlling azobenzene photoswitching through combined: {Ortho} -fluorination and -amination}, volume = {53}, doi = {10.1039/c7cc07308a}, abstract = {We present a series of visible-light-absorbing azobenzene photoswitches with cis-lifetimes ranging from one second to three days. We combine ortho-fluorination to control the cis-lifetimes, and ortho-amination to boost the visible-light absorption. The synthesis is accomplished by selectively replacing one or more ortho-fluorines with amines in the ortho-fluoroazobenzene precursors.}, journal = {Chemical Communications}, author = {Ahmed, Z. and Siiskonen, A. and Virkki, M. and Priimagi, A.}, month = oct, year = {2017}, pages = {12520--12523}, } - J. E. Stumpel, M. Saccone, V. DIchiarante, O. Lehtonen, M. Virkki, P. Metrangolo, and A. Priimagi, “Surface-relief gratings in halogen-bonded polymer-azobenzene complexes: A concentration-dependence study,” Molecules, vol. 22, p. 1844, 2017. doi:10.3390/molecules22111844
[BibTeX] [Abstract]
In recent years, supramolecular complexes comprising a poly(4-vinylpyridine) backbone and azobenzene-based halogen bond donors have emerged as a promising class of materials for the inscription of light-induced surface-relief gratings (SRGs). The studies up to date have focused on building supramolecular hierarchies, i.e., optimizing the polymer-azobenzene noncovalent interaction for efficient surface patterning. They have been conducted using systems with relatively low azobenzene content, and little is known about the concentration dependence of SRG formation in halogen-bonded polymer-azobenzene complexes. Herein, we bridge this gap, and study the concentration dependence of SRG formation using two halogen-bond-donating azobenzene derivatives, one functionalized with a tetrafluoroiodophenyl and the other with an iodoethynylphenyl group. Both have been previously identified as efficient molecules in driving the SRG formation. We cover a broad concentration range, starting from 10 mol \% azobenzene content and going all the way up to equimolar degree of complexation. The complexes are studied as spin-coated thin films, and analyzed by optical microscopy, atomic force microscopy, and optical diffraction arising during the SRG formation. We obtained diffraction efficiencies as high as 35\%, and modulation depths close to 400 nm, which are significantly higher than the values previously reported for halogen-bonded polymer-azobenzene complexes.
@article{stumpel_surface-relief_2017, title = {Surface-relief gratings in halogen-bonded polymer-azobenzene complexes: {A} concentration-dependence study}, volume = {22}, doi = {10.3390/molecules22111844}, abstract = {In recent years, supramolecular complexes comprising a poly(4-vinylpyridine) backbone and azobenzene-based halogen bond donors have emerged as a promising class of materials for the inscription of light-induced surface-relief gratings (SRGs). The studies up to date have focused on building supramolecular hierarchies, i.e., optimizing the polymer-azobenzene noncovalent interaction for efficient surface patterning. They have been conducted using systems with relatively low azobenzene content, and little is known about the concentration dependence of SRG formation in halogen-bonded polymer-azobenzene complexes. Herein, we bridge this gap, and study the concentration dependence of SRG formation using two halogen-bond-donating azobenzene derivatives, one functionalized with a tetrafluoroiodophenyl and the other with an iodoethynylphenyl group. Both have been previously identified as efficient molecules in driving the SRG formation. We cover a broad concentration range, starting from 10 mol \% azobenzene content and going all the way up to equimolar degree of complexation. The complexes are studied as spin-coated thin films, and analyzed by optical microscopy, atomic force microscopy, and optical diffraction arising during the SRG formation. We obtained diffraction efficiencies as high as 35\%, and modulation depths close to 400 nm, which are significantly higher than the values previously reported for halogen-bonded polymer-azobenzene complexes.}, journal = {Molecules}, author = {Stumpel, Jelle E. and Saccone, Marco and DIchiarante, Valentina and Lehtonen, Ossi and Virkki, Matti and Metrangolo, Pierangelo and Priimagi, Arri}, month = oct, year = {2017}, pages = {1844}, } - P. Vivo, J. K. Salunke, and A. Priimagi, “Hole-Transporting Materials for Printable Perovskite Solar Cells,” Materials, vol. 10, p. 1087, 2017. doi:10.3390/ma10091087
[BibTeX] [Abstract]
Perovskite solar cells (PSCs) represent undoubtedly the most significant breakthrough in photovoltaic technology since the 1970s, with an increase in their power conversion efficiency from less than 5\% to over 22\% in just a few years. Hole-transporting materials (HTMs) are an essential building block of PSC architectures. Currently, 2,2′,7,7′-tetrakis-(N,N’-di-p-methoxyphenylamine)-9,9′-spirobifluorene), better known as spiro-OMeTAD, is the most widely-used HTM to obtain high-efficiency devices. However, it is a tremendously expensive material with mediocre hole carrier mobility. To ensure wide-scale application of PSC-based technologies, alternative HTMs are being proposed. Solution-processable HTMs are crucial to develop inexpensive, high-throughput and printable large-area PSCs. In this review, we present the most recent advances in the design and development of different types of HTMs, with a particular focus on mesoscopic PSCs. Finally, we outline possible future research directions for further optimization of the HTMs to achieve low-cost, stable and large-area PSCs.
@article{vivo_hole-transporting_2017, title = {Hole-{Transporting} {Materials} for {Printable} {Perovskite} {Solar} {Cells}}, volume = {10}, doi = {10.3390/ma10091087}, abstract = {Perovskite solar cells (PSCs) represent undoubtedly the most significant breakthrough in photovoltaic technology since the 1970s, with an increase in their power conversion efficiency from less than 5\% to over 22\% in just a few years. Hole-transporting materials (HTMs) are an essential building block of PSC architectures. Currently, 2,2',7,7'-tetrakis-(N,N'-di-p-methoxyphenylamine)-9,9'-spirobifluorene), better known as spiro-OMeTAD, is the most widely-used HTM to obtain high-efficiency devices. However, it is a tremendously expensive material with mediocre hole carrier mobility. To ensure wide-scale application of PSC-based technologies, alternative HTMs are being proposed. Solution-processable HTMs are crucial to develop inexpensive, high-throughput and printable large-area PSCs. In this review, we present the most recent advances in the design and development of different types of HTMs, with a particular focus on mesoscopic PSCs. Finally, we outline possible future research directions for further optimization of the HTMs to achieve low-cost, stable and large-area PSCs.}, journal = {Materials}, author = {Vivo, Paola and Salunke, Jagadish K. and Priimagi, Arri}, month = sep, year = {2017}, pages = {1087}, } - J. Vapaavuori, A. Siiskonen, V. Dichiarante, A. Forni, M. Saccone, T. Pilati, C. Pellerin, A. Shishido, P. Metrangolo, and A. Priimagi, “Supramolecular control of liquid crystals by doping with halogen-bonding dyes,” RSC Advances, vol. 7, pp. 40237-40242, 2017. doi:10.1039/c7ra06397k
[BibTeX] [Abstract]
Introducing photochromic or polymeric dopants into nematic liquid crystals is a well-established method to create stimuli-responsive photonic materials with the ability to “control light with light”. Herein, we demonstrate a new material design concept by showing that specific supramolecular interactions between the host liquid crystal and the guest dopants enhance the optical performance of the doped liquid crystals. By varying the type and strength of the dopant-host interaction, the phase-transition temperature, the order parameter of the guest molecules, and the diffraction signal in response to interference irradiation, can be accurately engineered. Our concept points out the potential of supramolecular interactions in liquid-crystal photonics, being valuable for optimizing the design of dye-doped functional liquid-crystalline systems.
@article{vapaavuori_supramolecular_2017, title = {Supramolecular control of liquid crystals by doping with halogen-bonding dyes}, volume = {7}, doi = {10.1039/c7ra06397k}, abstract = {Introducing photochromic or polymeric dopants into nematic liquid crystals is a well-established method to create stimuli-responsive photonic materials with the ability to "control light with light". Herein, we demonstrate a new material design concept by showing that specific supramolecular interactions between the host liquid crystal and the guest dopants enhance the optical performance of the doped liquid crystals. By varying the type and strength of the dopant-host interaction, the phase-transition temperature, the order parameter of the guest molecules, and the diffraction signal in response to interference irradiation, can be accurately engineered. Our concept points out the potential of supramolecular interactions in liquid-crystal photonics, being valuable for optimizing the design of dye-doped functional liquid-crystalline systems.}, journal = {RSC Advances}, author = {Vapaavuori, Jaana and Siiskonen, Antti and Dichiarante, Valentina and Forni, Alessandra and Saccone, Marco and Pilati, Tullio and Pellerin, Christian and Shishido, Atsushi and Metrangolo, Pierangelo and Priimagi, Arri}, month = aug, year = {2017}, pages = {40237--40242}, } - H. Zeng, O. M. Wani, P. Wasylczyk, R. Kaczmarek, and A. Priimagi, “Self-Regulating Iris Based on Light-Actuated Liquid Crystal Elastomer,” Advanced Materials, vol. 29, p. 1701814, 2017. doi:10.1002/adma.201701814
[BibTeX] [Abstract]
The iris, found in many animal species, is a biological tissue that can change the aperture (pupil) size to regulate light transmission into the eye in response to varying illumination conditions. The self-regulation of the eye lies behind its autofocusing ability and large dynamic range, rendering it the ultimate “imaging device” and a continuous source of inspiration in science. In optical imaging devices, adjustable apertures play a vital role as they control the light exposure, the depth of field, and optical aberrations of the systems. Tunable irises demonstrated to date require external control through mechanical actuation, and are not capable of autonomous action in response to changing light intensity without control circuitry. A self-regulating artificial iris would offer new opportunities for device automation and stabilization. Here, this paper reports the first iris-like, liquid crystal elastomer device that can perform automatic shape-adjustment by reacting to the incident light power density. Similar to natural iris, the device closes under increasing light intensity, and upon reaching the minimum pupil size, reduces the light transmission by a factor of seven. The light-responsive materials design, together with photoalignment-based control over the molecular orientation, provides a new approach to automatic, self-regulating optical systems based on soft smart materials.
@article{zeng_self-regulating_2017, title = {Self-{Regulating} {Iris} {Based} on {Light}-{Actuated} {Liquid} {Crystal} {Elastomer}}, volume = {29}, doi = {10.1002/adma.201701814}, abstract = {The iris, found in many animal species, is a biological tissue that can change the aperture (pupil) size to regulate light transmission into the eye in response to varying illumination conditions. The self-regulation of the eye lies behind its autofocusing ability and large dynamic range, rendering it the ultimate “imaging device” and a continuous source of inspiration in science. In optical imaging devices, adjustable apertures play a vital role as they control the light exposure, the depth of field, and optical aberrations of the systems. Tunable irises demonstrated to date require external control through mechanical actuation, and are not capable of autonomous action in response to changing light intensity without control circuitry. A self-regulating artificial iris would offer new opportunities for device automation and stabilization. Here, this paper reports the first iris-like, liquid crystal elastomer device that can perform automatic shape-adjustment by reacting to the incident light power density. Similar to natural iris, the device closes under increasing light intensity, and upon reaching the minimum pupil size, reduces the light transmission by a factor of seven. The light-responsive materials design, together with photoalignment-based control over the molecular orientation, provides a new approach to automatic, self-regulating optical systems based on soft smart materials.}, journal = {Advanced Materials}, author = {Zeng, Hao and Wani, Owies M. and Wasylczyk, Piotr and Kaczmarek, Rados{\textbackslash}law and Priimagi, Arri}, month = aug, year = {2017}, pages = {1701814}, } - O. M. Wani, H. Zeng, and A. Priimagi, “A light-driven artificial flytrap,” Nature Communications, vol. 8, p. 15546, 2017. doi:10.1038/ncomms15546
[BibTeX] [Abstract]
The sophistication, complexity and intelligence of biological systems is a continuous source of inspiration for mankind. Mimicking the natural intelligence to devise tiny systems that are capable of self-regulated, autonomous action to, for example, distinguish different targets, remains among the grand challenges in biomimetic micro-robotics. Herein, we demonstrate an autonomous soft device, a light-driven flytrap, that uses optical feedback to trigger photomechanical actuation. The design is based on light-responsive liquid-crystal elastomer, fabricated onto the tip of an optical fibre, which acts as a power source and serves as a contactless probe that senses the environment. Mimicking natural flytraps, this artificial flytrap is capable of autonomous closure and object recognition. It enables self-regulated actuation within the fibre-sized architecture, thus opening up avenues towards soft, autonomous small-scale devices.
@article{wani_light-driven_2017, title = {A light-driven artificial flytrap}, volume = {8}, doi = {10.1038/ncomms15546}, abstract = {The sophistication, complexity and intelligence of biological systems is a continuous source of inspiration for mankind. Mimicking the natural intelligence to devise tiny systems that are capable of self-regulated, autonomous action to, for example, distinguish different targets, remains among the grand challenges in biomimetic micro-robotics. Herein, we demonstrate an autonomous soft device, a light-driven flytrap, that uses optical feedback to trigger photomechanical actuation. The design is based on light-responsive liquid-crystal elastomer, fabricated onto the tip of an optical fibre, which acts as a power source and serves as a contactless probe that senses the environment. Mimicking natural flytraps, this artificial flytrap is capable of autonomous closure and object recognition. It enables self-regulated actuation within the fibre-sized architecture, thus opening up avenues towards soft, autonomous small-scale devices.}, journal = {Nature Communications}, author = {Wani, Owies M. and Zeng, Hao and Priimagi, Arri}, month = aug, year = {2017}, pages = {15546}, } - N. Karimi, M. Virkki, A. Alberucci, O. Buchnev, M. Kauranen, A. Priimagi, and G. Assanto, “Molding Optical Waveguides with Nematicons,” Advanced Optical Materials, vol. 5, p. 1700199, 2017. doi:10.1002/adom.201700199
[BibTeX] [Abstract]
Optical waveguides are usually fabricated by top-down methods. Hereby, this study demonstrates a bottom-up approach based on nonlinear optics in reorientational nematic liquid crystals with polymerizable materials. Near-infrared optical spatial solitons – nematicons – in conjunction with UV exposure are employed in order to achieve (i) real-time signal waveguiding for point-to-point beam-induced interconnects by effectively quenching the fluctuations of nematicon trajectories through polymer stabilization; (ii) the molding of permanent channel waveguides in a crosslinked polymer network, so that they persist after turning off the soliton beam and confine signals of various wavelengths and intensities. These findings introduce a novel, highly versatile platform and a wealth of possibilities for guided-wave photonics, signal addressing, and processing in liquid crystalline soft matter.
@article{karimi_molding_2017, title = {Molding {Optical} {Waveguides} with {Nematicons}}, volume = {5}, doi = {10.1002/adom.201700199}, abstract = {Optical waveguides are usually fabricated by top-down methods. Hereby, this study demonstrates a bottom-up approach based on nonlinear optics in reorientational nematic liquid crystals with polymerizable materials. Near-infrared optical spatial solitons – nematicons – in conjunction with UV exposure are employed in order to achieve (i) real-time signal waveguiding for point-to-point beam-induced interconnects by effectively quenching the fluctuations of nematicon trajectories through polymer stabilization; (ii) the molding of permanent channel waveguides in a crosslinked polymer network, so that they persist after turning off the soliton beam and confine signals of various wavelengths and intensities. These findings introduce a novel, highly versatile platform and a wealth of possibilities for guided-wave photonics, signal addressing, and processing in liquid crystalline soft matter.}, journal = {Advanced Optical Materials}, author = {Karimi, Nazanin and Virkki, Matti and Alberucci, Alessandro and Buchnev, Oleksandr and Kauranen, Martti and Priimagi, Arri and Assanto, Gaetano}, month = jul, year = {2017}, pages = {1700199}, } - D. B. Shinde, J. K. Salunke, N. R. Candeias, F. Tinti, M. Gazzano, P. P. Wadgaonkar, A. Priimagi, N. Camaioni, and P. Vivo, “Crystallisation-enhanced bulk hole mobility in phenothiazine-based organic semiconductors,” Scientific Reports, vol. 7, p. 46268, 2017. doi:10.1038/srep46268
[BibTeX] [Abstract]
A series of three novel donor-acceptor systems based on C(3)-malononitrile-substituted phenothiazines was synthesised in good overall yields and their thermal, spectroscopic, and electrochemical properties were characterised. The compounds were prepared through a sequence of Ullmann-coupling, Vilsmeier-Haack formylation and Knoevenagel-condensation, followed by Suzuki-coupling reactions for introduction of aryl substitutents at C(7) position of the phenothiazine. The introduction of a donor unit at the C(7) position exhibited a weak impact on the optical and electrochemical characteristics of the compounds and led to amorphous films with bulk hole mobilities in the typical range reported for phenothiazines, despite the higher charge delocalisation as attested by computational studies. In contrast, highly ordered films were formed when using the C(7)-unsubstituted 3-malononitrile phenothiazine, exhibiting an outstanding mobility of 1 × 10-3 cm2 V-1 s-1, the highest reported for this class of compounds. Computational conformational analysis of the new phenothizanes suggested that free rotation of the substitutents at the C(7) position suppresses the ordering of the system, thereby hampering suitable packing of the new materials needed for high charge carrier mobility.
@article{shinde_crystallisation-enhanced_2017, title = {Crystallisation-enhanced bulk hole mobility in phenothiazine-based organic semiconductors}, volume = {7}, doi = {10.1038/srep46268}, abstract = {A series of three novel donor-acceptor systems based on C(3)-malononitrile-substituted phenothiazines was synthesised in good overall yields and their thermal, spectroscopic, and electrochemical properties were characterised. The compounds were prepared through a sequence of Ullmann-coupling, Vilsmeier-Haack formylation and Knoevenagel-condensation, followed by Suzuki-coupling reactions for introduction of aryl substitutents at C(7) position of the phenothiazine. The introduction of a donor unit at the C(7) position exhibited a weak impact on the optical and electrochemical characteristics of the compounds and led to amorphous films with bulk hole mobilities in the typical range reported for phenothiazines, despite the higher charge delocalisation as attested by computational studies. In contrast, highly ordered films were formed when using the C(7)-unsubstituted 3-malononitrile phenothiazine, exhibiting an outstanding mobility of 1 × 10-3 cm2 V-1 s-1, the highest reported for this class of compounds. Computational conformational analysis of the new phenothizanes suggested that free rotation of the substitutents at the C(7) position suppresses the ordering of the system, thereby hampering suitable packing of the new materials needed for high charge carrier mobility.}, journal = {Scientific Reports}, author = {Shinde, D. B. and Salunke, Jagadish K. and Candeias, Nuno R. and Tinti, Francesca and Gazzano, Massimo and Wadgaonkar, P. P. and Priimagi, Arri and Camaioni, Nadia and Vivo, Paola}, month = may, year = {2017}, pages = {46268}, } - M. Saccone, F. F. Palacio, G. Cavallo, V. Dichiarante, M. Virkki, G. Terraneo, A. Priimagi, and P. Metrangolo, “Photoresponsive ionic liquid crystals assembled: Via halogen bond: En route towards light-controllable ion transporters,” Faraday Discussions, vol. 203, pp. 407-422, 2017. doi:10.1039/c7fd00120g
[BibTeX] [Abstract]
We demonstrate that halogen bonding (XB) can offer a novel approach for the construction of photoresponsive ionic liquid crystals. In particular, we assembled two new supramolecular complexes based on 1-ethyl-3-methylimidazolium iodides and azobenzene derivatives containing an iodotetrafluoro-benzene ring as XB donor, where the iodide anion acted as an XB acceptor. DSC and X-ray diffraction analyses revealed that the preferred stoichiometry between the XB donors and acceptors is 2:1, and that the iodide anions act as bidentate XB-acceptors, binding two azobenzene derivatives. Due to the high directionality of the XB, calamitic superanions are obtained, while the segregation occurring between the charged and uncharged parts of the molecules gives rise to a layered structure in the crystal lattice. Despite the fact that the starting materials are non-mesomorphic, the halogen-bonded supramolecular complexes exhibited monotropic lamellar liquid-crystalline phases over broad temperature ranges, as confirmed with polarized optical microscopy. Due to the presence of the azobenzene moieties, the LCs were photoresponsive, and a LC-to-isotropic phase transition could be obtained by irradiation with UV light. We envisage that the light-induced phase transition, in combination with the ionic nature of the LC, provides a route towards light-induced control over ion transport and conductance in these supramolecular complexes.
@article{saccone_photoresponsive_2017, title = {Photoresponsive ionic liquid crystals assembled: {Via} halogen bond: {En} route towards light-controllable ion transporters}, volume = {203}, doi = {10.1039/c7fd00120g}, abstract = {We demonstrate that halogen bonding (XB) can offer a novel approach for the construction of photoresponsive ionic liquid crystals. In particular, we assembled two new supramolecular complexes based on 1-ethyl-3-methylimidazolium iodides and azobenzene derivatives containing an iodotetrafluoro-benzene ring as XB donor, where the iodide anion acted as an XB acceptor. DSC and X-ray diffraction analyses revealed that the preferred stoichiometry between the XB donors and acceptors is 2:1, and that the iodide anions act as bidentate XB-acceptors, binding two azobenzene derivatives. Due to the high directionality of the XB, calamitic superanions are obtained, while the segregation occurring between the charged and uncharged parts of the molecules gives rise to a layered structure in the crystal lattice. Despite the fact that the starting materials are non-mesomorphic, the halogen-bonded supramolecular complexes exhibited monotropic lamellar liquid-crystalline phases over broad temperature ranges, as confirmed with polarized optical microscopy. Due to the presence of the azobenzene moieties, the LCs were photoresponsive, and a LC-to-isotropic phase transition could be obtained by irradiation with UV light. We envisage that the light-induced phase transition, in combination with the ionic nature of the LC, provides a route towards light-induced control over ion transport and conductance in these supramolecular complexes.}, journal = {Faraday Discussions}, author = {Saccone, Marco and Palacio, Francisco Fernandez and Cavallo, Gabriella and Dichiarante, Valentina and Virkki, Matti and Terraneo, Giancarlo and Priimagi, Arri and Metrangolo, Pierangelo}, month = apr, year = {2017}, pages = {407--422}, } - M. Saccone, A. Siiskonen, F. Fernandez-Palacio, A. Priimagi, G. Terraneo, G. Resnati, and P. Metrangolo, “Halogen bonding stabilizes a cis-azobenzene derivative in the solid state: A crystallographic study,” Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials, vol. 73, pp. 227-233, 2017. doi:10.1107/S2052520617003444
[BibTeX] [Abstract]
Crystals of trans- and cis-isomers of a fluorinated azobenzene derivative have been prepared and characterized by single-crystal X-ray diffraction. The presence of F atoms on the aromatic core of the azobenzene increases the lifetime of the metastable cis-isomer, allowing single crystals of the cis-azobenzene to be grown. Structural analysis on the cis-azobenzene, complemented with density functional theory calculations, highlights the active role of the halogen-bond contact (N…I synthon) in promoting the stabilization of the cis-isomer. The presence of a long aliphatic chain on the azobenzene unit induces a phase segregation that stabilizes the molecular arrangement for both the trans- and cis-isomers. Due to the rarity of cis-azobenzene crystal structures in the literature, our paper makes a step towards understanding the role of non-covalent interactions in driving the packing of metastable azobenzene isomers. This is expected to be important in the future rational design of solid-state, photoresponsive materials based on halogen bonding. We show by single-crystal X-ray diffraction studies and computational analysis that halogen bonding can stabilize a metastable cis-azobenzene derivative in the solid state.
@article{saccone_halogen_2017, title = {Halogen bonding stabilizes a cis-azobenzene derivative in the solid state: {A} crystallographic study}, volume = {73}, doi = {10.1107/S2052520617003444}, abstract = {Crystals of trans- and cis-isomers of a fluorinated azobenzene derivative have been prepared and characterized by single-crystal X-ray diffraction. The presence of F atoms on the aromatic core of the azobenzene increases the lifetime of the metastable cis-isomer, allowing single crystals of the cis-azobenzene to be grown. Structural analysis on the cis-azobenzene, complemented with density functional theory calculations, highlights the active role of the halogen-bond contact (N...I synthon) in promoting the stabilization of the cis-isomer. The presence of a long aliphatic chain on the azobenzene unit induces a phase segregation that stabilizes the molecular arrangement for both the trans- and cis-isomers. Due to the rarity of cis-azobenzene crystal structures in the literature, our paper makes a step towards understanding the role of non-covalent interactions in driving the packing of metastable azobenzene isomers. This is expected to be important in the future rational design of solid-state, photoresponsive materials based on halogen bonding. We show by single-crystal X-ray diffraction studies and computational analysis that halogen bonding can stabilize a metastable cis-azobenzene derivative in the solid state.}, journal = {Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials}, author = {Saccone, Marco and Siiskonen, Antti and Fernandez-Palacio, Franisco and Priimagi, Arri and Terraneo, Giancarlo and Resnati, Giuseppe and Metrangolo, Pierangelo}, month = apr, year = {2017}, pages = {227--233}, } - R. Milani, N. Houbenov, F. Fernandez-Palacio, G. Cavallo, A. Luzio, J. Haataja, G. Giancane, M. Saccone, A. Priimagi, P. Metrangolo, and O. Ikkala, “Hierarchical Self-Assembly of Halogen-Bonded Block Copolymer Complexes into Upright Cylindrical Domains,” Chem, vol. 2, pp. 417-426, 2017. doi:10.1016/j.chempr.2017.02.003
[BibTeX] [Abstract]
Self-assembly of block copolymers into well-defined, ordered arrangements of chemically distinct domains is a reliable strategy for preparing tailored nanostructures. Microphase separation results from the system, minimizing repulsive interactions between dissimilar blocks and maximizing attractive interactions between similar blocks. Supramolecular methods have also achieved this separation by introducing small-molecule additives binding specifically to one block by noncovalent interactions. Here, we use halogen bonding as a supramolecular tool that directs the hierarchical self-assembly of low-molecular-weight perfluorinated molecules and diblock copolymers. Microphase separation results in a lamellar-within-cylindrical arrangement and promotes upright cylindrical alignment in films upon rapid casting and without further annealing. Such cylindrical domains with internal lamellar self-assemblies can be cleaved by solvent treatment of bulk films, resulting in separated and segmented cylindrical micelles stabilized by halogen-bond-based supramolecular crosslinks. These features, alongside the reversible nature of halogen bonding, provide a robust modular approach for nanofabrication.
@article{milani_hierarchical_2017, title = {Hierarchical {Self}-{Assembly} of {Halogen}-{Bonded} {Block} {Copolymer} {Complexes} into {Upright} {Cylindrical} {Domains}}, volume = {2}, doi = {10.1016/j.chempr.2017.02.003}, abstract = {Self-assembly of block copolymers into well-defined, ordered arrangements of chemically distinct domains is a reliable strategy for preparing tailored nanostructures. Microphase separation results from the system, minimizing repulsive interactions between dissimilar blocks and maximizing attractive interactions between similar blocks. Supramolecular methods have also achieved this separation by introducing small-molecule additives binding specifically to one block by noncovalent interactions. Here, we use halogen bonding as a supramolecular tool that directs the hierarchical self-assembly of low-molecular-weight perfluorinated molecules and diblock copolymers. Microphase separation results in a lamellar-within-cylindrical arrangement and promotes upright cylindrical alignment in films upon rapid casting and without further annealing. Such cylindrical domains with internal lamellar self-assemblies can be cleaved by solvent treatment of bulk films, resulting in separated and segmented cylindrical micelles stabilized by halogen-bond-based supramolecular crosslinks. These features, alongside the reversible nature of halogen bonding, provide a robust modular approach for nanofabrication.}, journal = {Chem}, author = {Milani, Roberto and Houbenov, Nikolay and Fernandez-Palacio, Francisco and Cavallo, Gabriella and Luzio, Alessandro and Haataja, Johannes and Giancane, Gabriele and Saccone, Marco and Priimagi, Arri and Metrangolo, Pierangelo and Ikkala, Olli}, month = mar, year = {2017}, pages = {417--426}, } - J. Noga, A. Sobolewska, S. Bartkiewicz, M. Virkki, and A. Priimagi, “Periodic Surface Structures Induced by a Single Laser Beam Irradiation,” Macromolecular Materials and Engineering, vol. 302, p. 1600329, 2017. doi:10.1002/mame.201600329
[BibTeX] [Abstract]
Methods for inscribing periodic surface patterns by light, especially those characterized by the ability to control the pattern dimensions, are continuously sought for. In this paper, a periodic pattern, which is called the willow structure, is written to a supramolecular polymer-azobenzene complex using a single coherent laser beam of linear polarization. The willow structure can be an alternative to the commonly used surface relief grating written with an interference pattern once it is known how to manipulate its period. It is shown that the periodicity of the structure obtained with the one-beam approach can be controlled by changing the thickness of the polymer layer and the inscription temperature, in addition to the wavelength of the inscribing light. This information is useful for the utilization of the single-beam method as a way for obtaining periodic structures with desired dimensions.
@article{noga_periodic_2017, title = {Periodic {Surface} {Structures} {Induced} by a {Single} {Laser} {Beam} {Irradiation}}, volume = {302}, doi = {10.1002/mame.201600329}, abstract = {Methods for inscribing periodic surface patterns by light, especially those characterized by the ability to control the pattern dimensions, are continuously sought for. In this paper, a periodic pattern, which is called the willow structure, is written to a supramolecular polymer-azobenzene complex using a single coherent laser beam of linear polarization. The willow structure can be an alternative to the commonly used surface relief grating written with an interference pattern once it is known how to manipulate its period. It is shown that the periodicity of the structure obtained with the one-beam approach can be controlled by changing the thickness of the polymer layer and the inscription temperature, in addition to the wavelength of the inscribing light. This information is useful for the utilization of the single-beam method as a way for obtaining periodic structures with desired dimensions.}, journal = {Macromolecular Materials and Engineering}, author = {Noga, Joanna and Sobolewska, Anna and Bartkiewicz, Stanislaw and Virkki, Matti and Priimagi, Arri}, month = feb, year = {2017}, pages = {1600329}, } - A. Siiskonen and A. Priimagi, “Benchmarking DFT methods with small basis sets for the calculation of halogen-bond strengths,” Journal of Molecular Modeling, vol. 23, p. 50, 2017. doi:10.1007/s00894-017-3212-4
[BibTeX] [Abstract]
In recent years, halogen bonding has become an important design tool in crystal engineering, supramolecular chemistry and biosciences. The fundamentals of halogen bonding have been studied extensively with high-accuracy computational methods. Due to its non-covalency, the use of triple-zeta (or larger) basis sets is often recommended when studying halogen bonding. However, in the large systems often encountered in supramolecular chemistry and biosciences, large basis sets can make the calculations far too slow. Therefore, small basis sets, which would combine high computational speed and high accuracy, are in great demand. This study focuses on comparing how well density functional theory (DFT) methods employing small, double-zeta basis sets can estimate halogen-bond strengths. Several methods with triple-zeta basis sets are included for comparison. Altogether, 46 DFT methods were tested using two data sets of 18 and 33 halogen-bonded complexes for which the complexation energies have been previously calculated with the high-accuracy CCSD(T)/CBS method. The DGDZVP basis set performed far better than other double-zeta basis sets, and it even outperformed the triple-zeta basis sets. Due to its small size, it is well-suited to studying halogen bonding in large systems.
@article{siiskonen_benchmarking_2017, title = {Benchmarking {DFT} methods with small basis sets for the calculation of halogen-bond strengths}, volume = {23}, doi = {10.1007/s00894-017-3212-4}, abstract = {In recent years, halogen bonding has become an important design tool in crystal engineering, supramolecular chemistry and biosciences. The fundamentals of halogen bonding have been studied extensively with high-accuracy computational methods. Due to its non-covalency, the use of triple-zeta (or larger) basis sets is often recommended when studying halogen bonding. However, in the large systems often encountered in supramolecular chemistry and biosciences, large basis sets can make the calculations far too slow. Therefore, small basis sets, which would combine high computational speed and high accuracy, are in great demand. This study focuses on comparing how well density functional theory (DFT) methods employing small, double-zeta basis sets can estimate halogen-bond strengths. Several methods with triple-zeta basis sets are included for comparison. Altogether, 46 DFT methods were tested using two data sets of 18 and 33 halogen-bonded complexes for which the complexation energies have been previously calculated with the high-accuracy CCSD(T)/CBS method. The DGDZVP basis set performed far better than other double-zeta basis sets, and it even outperformed the triple-zeta basis sets. Due to its small size, it is well-suited to studying halogen bonding in large systems.}, journal = {Journal of Molecular Modeling}, author = {Siiskonen, Antti and Priimagi, Arri}, month = feb, year = {2017}, pages = {50}, } - J. Wang, Y. Aihara, M. Kinoshita, J. Mamiya, A. Priimagi, and A. Shishido, “Orientational optical nonlinearities is polymer-stabilized dye-doped liquid crystals,” Journal of the Japanese Liquid Crystal Society, vol. 21, pp. 57-67, 2017.
[BibTeX] [Abstract]
Dye-doped liquid crystals have drawn much attention for their potential in nonlinear optical applications. To invoke nonlinear optical effects, high light intensities are typically required. This review briefly introduces our group’s efforts on developing highly nonlinear, dye-doped LC systems. By (i) using an effective oligothiophene dye, (ii) introducing polymer stabilization of the LC host and (iii) using hybrid molecular alignment, we have achieved self-focusing, a common third-order nonlinear process, even using a low-power, handheld laser-pointer.
@article{wang_orientational_2017, title = {Orientational optical nonlinearities is polymer-stabilized dye-doped liquid crystals}, volume = {21}, abstract = {Dye-doped liquid crystals have drawn much attention for their potential in nonlinear optical applications. To invoke nonlinear optical effects, high light intensities are typically required. This review briefly introduces our group's efforts on developing highly nonlinear, dye-doped LC systems. By (i) using an effective oligothiophene dye, (ii) introducing polymer stabilization of the LC host and (iii) using hybrid molecular alignment, we have achieved self-focusing, a common third-order nonlinear process, even using a low-power, handheld laser-pointer.}, journal = {Journal of the Japanese Liquid Crystal Society}, author = {Wang, J and Aihara, Y and Kinoshita, M and Mamiya, J and Priimagi, A and Shishido, A}, month = jan, year = {2017}, pages = {57--67}, }
2016
- P. Hiekkataipale, T. I. Löbling, M. Poutanen, A. Priimagi, V. Abetz, O. Ikkala, and A. H. Gröschel, “Controlling the shape of Janus nanostructures through supramolecular modification of ABC terpolymer bulk morphologies,” Polymer, vol. 107, pp. 456-465, 2016. doi:10.1016/j.polymer.2016.05.076
[BibTeX] [Abstract]
Block copolymers microphase separate into a variety of bulk morphologies that serve as scaffolds, templates, masks and source for polymeric nano-particles. While supramolecular additives are common to complex within diblock copolymers to modify the morphology, the subtle effects of complexation on ABC triblock terpolymer morphologies are less explored. Here, we describe the manipulation of polystyrene-block-poly(4-vinylpyridine)-block-poly(tert-butyl methacrylate) (PS-b-P4VP-b-PT or S4VT) triblock terpolymer bulk morphologies through supramolecular complexation with rod-like 4-(4-pentylphenylazo)phenol (5PAP). The 5PAP molecule hydrogen bonds by phenolic groups to the 4VP repeating units and with increasing molar fraction of 5PAP, initially observed P4VP cylinders flatten into elliptic cylinders until a morphological transition occurs into a third (P4VP/5PAP) lamella. At sufficient 5PAP loadings, the cylinders can even merge into a perforated P4VP lamella located at the PS/PT interface. Quaternization of the P4VP phase and re-dispersion in organic solvent allows liberating S4VT Janus nanostructures from the bulk, including Janus cylinders, nanoporous Janus membranes and Janus sheets. The manipulation of “sandwiched” microphases through supramolecular binding motifs could allow the preparation of previously inaccessible terpolymer bulk morphologies and, in case of cross-linkable phases, lead to a larger library of Janus nano-objects.
@article{hiekkataipale_controlling_2016, title = {Controlling the shape of {Janus} nanostructures through supramolecular modification of {ABC} terpolymer bulk morphologies}, volume = {107}, doi = {10.1016/j.polymer.2016.05.076}, abstract = {Block copolymers microphase separate into a variety of bulk morphologies that serve as scaffolds, templates, masks and source for polymeric nano-particles. While supramolecular additives are common to complex within diblock copolymers to modify the morphology, the subtle effects of complexation on ABC triblock terpolymer morphologies are less explored. Here, we describe the manipulation of polystyrene-block-poly(4-vinylpyridine)-block-poly(tert-butyl methacrylate) (PS-b-P4VP-b-PT or S4VT) triblock terpolymer bulk morphologies through supramolecular complexation with rod-like 4-(4-pentylphenylazo)phenol (5PAP). The 5PAP molecule hydrogen bonds by phenolic groups to the 4VP repeating units and with increasing molar fraction of 5PAP, initially observed P4VP cylinders flatten into elliptic cylinders until a morphological transition occurs into a third (P4VP/5PAP) lamella. At sufficient 5PAP loadings, the cylinders can even merge into a perforated P4VP lamella located at the PS/PT interface. Quaternization of the P4VP phase and re-dispersion in organic solvent allows liberating S4VT Janus nanostructures from the bulk, including Janus cylinders, nanoporous Janus membranes and Janus sheets. The manipulation of “sandwiched” microphases through supramolecular binding motifs could allow the preparation of previously inaccessible terpolymer bulk morphologies and, in case of cross-linkable phases, lead to a larger library of Janus nano-objects.}, journal = {Polymer}, author = {Hiekkataipale, Panu and Löbling, Tina I. and Poutanen, Mikko and Priimagi, Arri and Abetz, Volker and Ikkala, Olli and Gröschel, Andre H.}, month = dec, year = {2016}, pages = {456--465}, } - F. Fernandez-Palacio, M. Poutanen, M. Saccone, A. Siiskonen, G. Terraneo, G. Resnati, O. Ikkala, P. Metrangolo, and A. Priimagi, “Efficient light-induced phase transitions in halogen-bonded liquid crystals,” Chemistry of Materials, vol. 28, pp. 8314-8321, 2016. doi:10.1021/acs.chemmater.6b03460
[BibTeX] [Abstract]
Here, we present a new family of light-responsive, fluorinated supramolecular liquid crystals (LCs) showing efficient and reversible light-induced LC-to-isotropic phase transitions. Our materials design is based on fluorinated azobenzenes, where the fluorination serves to strengthen the noncovalent interaction with bond-accepting stilbazole molecules, and increase the lifetime of the cis-form of the azobenzene units. The halogen-bonded LCs were characterized by means of X-ray diffraction, hot-stage polarized optical microscopy, and differential scanning calorimetry. Simultaneous analysis of light-induced changes in birefringence, absorption, and optical scattering allowed us to estimate that \textbackslashtextless4\% of the mesogenic units in the cis-form suffices to trigger the full LC-to-isotropic phase transition. We also report a light-induced and reversible crystal-to-isotropic phase transition, which has not been previously observed in supramolecular complexes. In addition to fundamental understanding of light-responsive supramolecular complexes, we foresee this study to be important in the development of bistable photonic devices and supramolecular actuators.
@article{fernandez-palacio_efficient_2016, title = {Efficient light-induced phase transitions in halogen-bonded liquid crystals}, volume = {28}, doi = {10.1021/acs.chemmater.6b03460}, abstract = {Here, we present a new family of light-responsive, fluorinated supramolecular liquid crystals (LCs) showing efficient and reversible light-induced LC-to-isotropic phase transitions. Our materials design is based on fluorinated azobenzenes, where the fluorination serves to strengthen the noncovalent interaction with bond-accepting stilbazole molecules, and increase the lifetime of the cis-form of the azobenzene units. The halogen-bonded LCs were characterized by means of X-ray diffraction, hot-stage polarized optical microscopy, and differential scanning calorimetry. Simultaneous analysis of light-induced changes in birefringence, absorption, and optical scattering allowed us to estimate that {\textbackslash}textless4\% of the mesogenic units in the cis-form suffices to trigger the full LC-to-isotropic phase transition. We also report a light-induced and reversible crystal-to-isotropic phase transition, which has not been previously observed in supramolecular complexes. In addition to fundamental understanding of light-responsive supramolecular complexes, we foresee this study to be important in the development of bistable photonic devices and supramolecular actuators.}, journal = {Chemistry of Materials}, author = {Fernandez-Palacio, Francisco and Poutanen, Mikko and Saccone, Marco and Siiskonen, Antti and Terraneo, Giancarlo and Resnati, Giuseppe and Ikkala, Olli and Metrangolo, Pierangelo and Priimagi, Arri}, month = nov, year = {2016}, pages = {8314--8321}, } - Í. Neto, J. Andrade, A. S. Fernandes, C. Pinto Reis, J. K. Salunke, A. Priimagi, N. R. Candeias, and P. Rijo, “Multicomponent Petasis-borono Mannich Preparation of Alkylaminophenols and Antimicrobial Activity Studies,” ChemMedChem, vol. 11, pp. 2015-2023, 2016. doi:10.1002/cmdc.201600244
[BibTeX] [Abstract]
In this work we report the antibacterial activity of alkylaminophenols. A series of such compounds was prepared by a multicomponent Petasis-borono Mannich reaction starting from salicylaldehyde and its derivatives. The obtained compounds were tested against a large panel of microorganisms, Gram-positive and Gram-negative bacteria, and a yeast. Among the several tertiary amine derivatives tested, indoline-derived aminophenols containing a nitro group at the para-phenol position showed considerable activity against bacteria tested with minimal inhibitory concentrations as low as 1.36 μm against Staphyloccocus aureus and Mycobacterium smegmatis. Cytotoxicity of the new para-nitrophenol derivatives was observed only at concentrations much higher than those required for antibacterial activity.
@article{neto_multicomponent_2016, title = {Multicomponent {Petasis}-borono {Mannich} {Preparation} of {Alkylaminophenols} and {Antimicrobial} {Activity} {Studies}}, volume = {11}, doi = {10.1002/cmdc.201600244}, abstract = {In this work we report the antibacterial activity of alkylaminophenols. A series of such compounds was prepared by a multicomponent Petasis-borono Mannich reaction starting from salicylaldehyde and its derivatives. The obtained compounds were tested against a large panel of microorganisms, Gram-positive and Gram-negative bacteria, and a yeast. Among the several tertiary amine derivatives tested, indoline-derived aminophenols containing a nitro group at the para-phenol position showed considerable activity against bacteria tested with minimal inhibitory concentrations as low as 1.36 μm against Staphyloccocus aureus and Mycobacterium smegmatis. Cytotoxicity of the new para-nitrophenol derivatives was observed only at concentrations much higher than those required for antibacterial activity.}, journal = {ChemMedChem}, author = {Neto, Íris and Andrade, Joana and Fernandes, A. S. and Pinto Reis, Catarina and Salunke, Jagadish K. and Priimagi, Arri and Candeias, Nuno R. and Rijo, Patrícia}, month = sep, year = {2016}, pages = {2015--2023}, } - N. Akamatsu, M. Aizawa, R. Tatsumi, K. Hisano, A. Priimagi, and A. Shishido, “Photoresponsive liquid-crystalline polymer films bilayered with an inverse opal structure,” Journal of Photopolymer Science and Technology, vol. 29, pp. 145-148, 2016. doi:10.2494/photopolymer.29.145
[BibTeX] [Abstract]
An inverse opal film was layered to a photodeformable film, and its photoresponsive behavior was investigated. This bilayer films composed of colorless photonic crystal using inverse opal structures and colored photoresponsive layers with azobenzene-containing CLCP.
@article{akamatsu_photoresponsive_2016, title = {Photoresponsive liquid-crystalline polymer films bilayered with an inverse opal structure}, volume = {29}, doi = {10.2494/photopolymer.29.145}, abstract = {An inverse opal film was layered to a photodeformable film, and its photoresponsive behavior was investigated. This bilayer films composed of colorless photonic crystal using inverse opal structures and colored photoresponsive layers with azobenzene-containing CLCP.}, journal = {Journal of Photopolymer Science and Technology}, author = {Akamatsu, Norihisa and Aizawa, Miho and Tatsumi, Ryoichi and Hisano, Kyohei and Priimagi, Arri and Shishido, Atsushi}, month = aug, year = {2016}, pages = {145--148}, } - M. Poutanen, O. Ikkala, and A. Priimagi, “Structurally Controlled Dynamics in Azobenzene-Based Supramolecular Self-Assemblies in Solid State,” Macromolecules, vol. 49, pp. 4095-4101, 2016. doi:10.1021/acs.macromol.6b00562
[BibTeX] [Abstract]
Light-responsive supramolecular self-assemblies exhibit interplay between order and dynamics of the self-assembling motifs, through which the thermal isomerization rate of azobenzene chromophores can be tuned by orders of magnitude. By using supramolecular complexes of 4-(4-alkylphenylazo)phenols hydrogen-bonded to poly(4-vinylpyridine) as model systems, we demonstrate that the thermal isomerization rate of the hydroxyazobenzene derivatives increases 5700-fold when the material undergoes a transformation from a disordered, low-azobenzene-concentration state to a high-concentration state exhibiting lamellar, smectic-like self-assembly. Drastically smaller thermal isomerization rates are observed in disordered structures. This allows us to attribute the change to a combination of increased number density of the hydroxyazobenzenes inducing plasticization, and cooperativity created by the chromophore-chromophore interactions through self-assembled molecular order and alignment. Our results pinpoint the importance of molecular self-assembly and intermolecular interactions in modifying the dynamics in supramolecular complexes in a controlled manner. We foresee this to be important in light-controlled dynamic materials.
@article{poutanen_structurally_2016, title = {Structurally {Controlled} {Dynamics} in {Azobenzene}-{Based} {Supramolecular} {Self}-{Assemblies} in {Solid} {State}}, volume = {49}, doi = {10.1021/acs.macromol.6b00562}, abstract = {Light-responsive supramolecular self-assemblies exhibit interplay between order and dynamics of the self-assembling motifs, through which the thermal isomerization rate of azobenzene chromophores can be tuned by orders of magnitude. By using supramolecular complexes of 4-(4-alkylphenylazo)phenols hydrogen-bonded to poly(4-vinylpyridine) as model systems, we demonstrate that the thermal isomerization rate of the hydroxyazobenzene derivatives increases 5700-fold when the material undergoes a transformation from a disordered, low-azobenzene-concentration state to a high-concentration state exhibiting lamellar, smectic-like self-assembly. Drastically smaller thermal isomerization rates are observed in disordered structures. This allows us to attribute the change to a combination of increased number density of the hydroxyazobenzenes inducing plasticization, and cooperativity created by the chromophore-chromophore interactions through self-assembled molecular order and alignment. Our results pinpoint the importance of molecular self-assembly and intermolecular interactions in modifying the dynamics in supramolecular complexes in a controlled manner. We foresee this to be important in light-controlled dynamic materials.}, journal = {Macromolecules}, author = {Poutanen, Mikko and Ikkala, Olli and Priimagi, Arri}, month = jun, year = {2016}, pages = {4095--4101}, } - G. Cavallo, G. Terraneo, A. Monfredini, M. Saccone, A. Priimagi, T. Pilati, G. Resnati, P. Metrangolo, and D. W. Bruce, “Superfluorinated ionic liquid crystals based on supramolecular, halogen-bonded anions,” Angewandte Chemie International Edition, vol. 55, pp. 6300-6304, 2016. doi:10.1002/anie.201601278
[BibTeX] [Abstract]
Unconventional ionic liquid crystals in which the liquid crystallinity is enabled by halogen-bonded supramolecular anions [CnF2 n+1-I⋯I⋯I-CnF2 n+1]- are reported. The material system is unique in many ways, demonstrating for the first time 1) ionic, halogen-bonded liquid crystals, and 2) imidazolium-based ionic liquid crystals in which the occurrence of liquid crystallinity is not driven by the alkyl chains of the cation. Out of the ordinary: The high directionality of halogen bonds and the fluorophobic effect were exploited in the design and synthesis of a new family of unconventional superfluorinated ionic liquid crystals. The liquid crystallinity of the system is driven by halogen-bonded supramolecular anions [CnF2 n+1-I⋯I⋯I-CnF2 n+1]- which act as rigid rod-like calamitic units.
@article{cavallo_superfluorinated_2016, title = {Superfluorinated ionic liquid crystals based on supramolecular, halogen-bonded anions}, volume = {55}, doi = {10.1002/anie.201601278}, abstract = {Unconventional ionic liquid crystals in which the liquid crystallinity is enabled by halogen-bonded supramolecular anions [CnF2 n+1-I⋯I⋯I-CnF2 n+1]- are reported. The material system is unique in many ways, demonstrating for the first time 1) ionic, halogen-bonded liquid crystals, and 2) imidazolium-based ionic liquid crystals in which the occurrence of liquid crystallinity is not driven by the alkyl chains of the cation. Out of the ordinary: The high directionality of halogen bonds and the fluorophobic effect were exploited in the design and synthesis of a new family of unconventional superfluorinated ionic liquid crystals. The liquid crystallinity of the system is driven by halogen-bonded supramolecular anions [CnF2 n+1-I⋯I⋯I-CnF2 n+1]- which act as rigid rod-like calamitic units.}, journal = {Angewandte Chemie International Edition}, author = {Cavallo, Gabriella and Terraneo, Giancarlo and Monfredini, Alessandro and Saccone, Marco and Priimagi, Arri and Pilati, Tullio and Resnati, Giuseppe and Metrangolo, Pierangelo and Bruce, Duncan W.}, month = may, year = {2016}, pages = {6300--6304}, } - M. Virkki, O. Tuominen, M. Kauranen, and A. Priimagi, “Photoinduced nonlinear optical response in azobenzene-functionalized molecular glass,” Optics Express, vol. 24, p. 4964, 2016. doi:10.1364/oe.24.004964
[BibTeX] [Abstract]
We show that mexylaminotriazine molecular glass functionalized with the azobenzene derivative Disperse Red 1 shows equally strong second-order nonlinear optical response as well-known polymers with the same photoactive component. Furthermore, even high chromophore loading does not adversely affect the nonlinear response. This suggests that chromophore-chromophore intermolecular interactions do not greatly limit the response of such molecular glasses, which therefore provide an excellent materials platform for nonlinear optical applications.
@article{virkki_photoinduced_2016, title = {Photoinduced nonlinear optical response in azobenzene-functionalized molecular glass}, volume = {24}, doi = {10.1364/oe.24.004964}, abstract = {We show that mexylaminotriazine molecular glass functionalized with the azobenzene derivative Disperse Red 1 shows equally strong second-order nonlinear optical response as well-known polymers with the same photoactive component. Furthermore, even high chromophore loading does not adversely affect the nonlinear response. This suggests that chromophore-chromophore intermolecular interactions do not greatly limit the response of such molecular glasses, which therefore provide an excellent materials platform for nonlinear optical applications.}, journal = {Optics Express}, author = {Virkki, Matti and Tuominen, Ossi and Kauranen, Martti and Priimagi, Arri}, month = mar, year = {2016}, pages = {4964}, } - N. Karimi, A. Alberucci, M. Virkki, A. Priimagi, M. Kauranen, and G. Assanto, “Quenching nematicon fluctuations via photo-stabilization,” Photonics Letters of Poland, vol. 8, pp. 2-4, 2016. doi:10.4302/plp.2016.1.02
[BibTeX] [Abstract]
Light localization into optical spatial solitons can be achieved by launching optical beams in nonlocal nonlinear nematic liquid crystals. Such solitons often undergo undesired fluctuations of their trajectories. We demonstrate that partial polymerization in monoacrylate-doped nematic liquid crystals is effective in quenching such fluctuations in transverse space.
@article{karimi_quenching_2016, title = {Quenching nematicon fluctuations via photo-stabilization}, volume = {8}, doi = {10.4302/plp.2016.1.02}, abstract = {Light localization into optical spatial solitons can be achieved by launching optical beams in nonlocal nonlinear nematic liquid crystals. Such solitons often undergo undesired fluctuations of their trajectories. We demonstrate that partial polymerization in monoacrylate-doped nematic liquid crystals is effective in quenching such fluctuations in transverse space.}, journal = {Photonics Letters of Poland}, author = {Karimi, Nazanin and Alberucci, Alessandro and Virkki, Matti and Priimagi, Arri and Kauranen, Martti and Assanto, Gaetano}, month = mar, year = {2016}, pages = {2--4}, } - G. Cavallo, P. Metrangolo, R. Milani, T. Pilati, A. Priimagi, G. Resnati, and G. Terraneo, “The halogen bond,” Chemical Reviews, vol. 116, pp. 2478-2601, 2016. doi:10.1021/acs.chemrev.5b00484
[BibTeX] [Abstract]
The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.
@article{cavallo_halogen_2016, title = {The halogen bond}, volume = {116}, doi = {10.1021/acs.chemrev.5b00484}, abstract = {The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.}, journal = {Chemical Reviews}, author = {Cavallo, Gabriella and Metrangolo, Pierangelo and Milani, Roberto and Pilati, Tullio and Priimagi, Arri and Resnati, Giuseppe and Terraneo, Giancarlo}, month = feb, year = {2016}, pages = {2478--2601}, } - F. Fernandez-Palacio, M. Saccone, A. Priimagi, G. Terraneo, T. Pilati, P. Metrangolo, and G. Resnati, “Coordination networks incorporating halogen-bond donor sites and azobenzene groups,” CrystEngComm, vol. 18, pp. 2251-2257, 2016. doi:10.1039/c6ce00059b
[BibTeX] [Abstract]
Two Zn coordination networks, \[Zn(1)(Py)2]2(2-propanol)\n (3) and \[Zn(1)2(Bipy)2](DMF)2\n (4), incorporating halogen-bond (XB) donor sites and azobenzene groups have been synthesized and fully characterized. Obtaining 3 and 4 confirms that it is possible to use a ligand wherein its coordination bond acceptor sites and XB donor sites are on the same molecular scaffold (i.e., an aromatic ring) without interfering with each other. We demonstrate that XBs play a fundamental role in the architectures and properties of the obtained coordination networks. In 3, XBs promote the formation of 2D supramolecular layers, which, by overlapping each other, allow the incorporation of 2-propanol as a guest molecule. In 4, XBs support the connection of the layers and are essential to firmly pin DMF solvent molecules through I⋯O contacts, thus increasing the stability of the solvated systems.
@article{fernandez-palacio_coordination_2016, title = {Coordination networks incorporating halogen-bond donor sites and azobenzene groups}, volume = {18}, doi = {10.1039/c6ce00059b}, abstract = {Two Zn coordination networks, \{[Zn(1)(Py)2]2(2-propanol)\}n (3) and \{[Zn(1)2(Bipy)2](DMF)2\}n (4), incorporating halogen-bond (XB) donor sites and azobenzene groups have been synthesized and fully characterized. Obtaining 3 and 4 confirms that it is possible to use a ligand wherein its coordination bond acceptor sites and XB donor sites are on the same molecular scaffold (i.e., an aromatic ring) without interfering with each other. We demonstrate that XBs play a fundamental role in the architectures and properties of the obtained coordination networks. In 3, XBs promote the formation of 2D supramolecular layers, which, by overlapping each other, allow the incorporation of 2-propanol as a guest molecule. In 4, XBs support the connection of the layers and are essential to firmly pin DMF solvent molecules through I⋯O contacts, thus increasing the stability of the solvated systems.}, journal = {CrystEngComm}, author = {Fernandez-Palacio, Francisco and Saccone, Marco and Priimagi, Arri and Terraneo, Giancarlo and Pilati, Tullio and Metrangolo, Pierangelo and Resnati, Giuseppe}, month = jan, year = {2016}, pages = {2251--2257}, }
2015
- M. Saccone, V. Dichiarante, A. Forni, A. Goulet-Hanssens, G. Cavallo, J. Vapaavuori, G. Terraneo, C. J. Barrett, G. Resnati, P. Metrangolo, and A. Priimagi, “Supramolecular hierarchy among halogen and hydrogen bond donors in light-induced surface patterning,” Journal of Materials Chemistry C, vol. 3, pp. 759-768, 2015. doi:10.1039/c4tc02315c
[BibTeX] [Abstract]
Halogen bonding, a noncovalent interaction possessing several unique features compared to the more familiar hydrogen bonding, is emerging as a powerful tool in functional materials design. Herein, we unambiguously show that one of these characteristic features, namely high directionality, renders halogen bonding the interaction of choice when developing azobenzene-containing supramolecular polymers for light-induced surface patterning. The study is conducted by using an extensive library of azobenzene molecules that differ only in terms of the bond-donor unit. We introduce a new tetrafluorophenol-containing azobenzene photoswitch capable of forming strong hydrogen bonds, and show that an iodoethynyl-containing azobenzene comes out on top of the supramolecular hierarchy to provide unprecedented photoinduced surface patterning efficiency. Specifically, the iodoethynyl motif seems highly promising in future development of polymeric optical and photoactive materials driven by halogen bonding.
@article{saccone_supramolecular_2015, title = {Supramolecular hierarchy among halogen and hydrogen bond donors in light-induced surface patterning}, volume = {3}, doi = {10.1039/c4tc02315c}, abstract = {Halogen bonding, a noncovalent interaction possessing several unique features compared to the more familiar hydrogen bonding, is emerging as a powerful tool in functional materials design. Herein, we unambiguously show that one of these characteristic features, namely high directionality, renders halogen bonding the interaction of choice when developing azobenzene-containing supramolecular polymers for light-induced surface patterning. The study is conducted by using an extensive library of azobenzene molecules that differ only in terms of the bond-donor unit. We introduce a new tetrafluorophenol-containing azobenzene photoswitch capable of forming strong hydrogen bonds, and show that an iodoethynyl-containing azobenzene comes out on top of the supramolecular hierarchy to provide unprecedented photoinduced surface patterning efficiency. Specifically, the iodoethynyl motif seems highly promising in future development of polymeric optical and photoactive materials driven by halogen bonding.}, journal = {Journal of Materials Chemistry C}, author = {Saccone, Marco and Dichiarante, Valentina and Forni, Alessandra and Goulet-Hanssens, Alexis and Cavallo, Gabriella and Vapaavuori, Jaana and Terraneo, Giancarlo and Barrett, Christopher J. and Resnati, Giuseppe and Metrangolo, Pierangelo and Priimagi, Arri}, month = nov, year = {2015}, pages = {759--768}, } - J. Vapaavuori, I. T. S. Heikkinen, V. Dichiarante, G. Resnati, P. Metrangolo, R. G. Sabat, G. C. Bazuin, A. Priimagi, and C. Pellerin, “Photomechanical Energy Transfer to Photopassive Polymers through Hydrogen and Halogen Bonds,” Macromolecules, vol. 48, pp. 7535-7542, 2015. doi:10.1021/acs.macromol.5b01813
[BibTeX] [Abstract]
The supramolecular assembly of photoactive azobenzenes with passive polymers via halogen or hydrogen bonding is a cost-effective way to design materials for various photomechanical applications that convert light energy directly into macroscopic motion, for instance, in all-optical surface patterning and photochemical imaging of plasmonic structures. To elucidate the molecular-level origins of this motion, we show, by coupling dynamic infrared spectroscopy to a photo-orientation setup, that supramolecular bonds above a certain interaction strength threshold are photostable under vigorous photoisomerization cycling and capable of translating the photo-orientation of azobenzenes into the orientation of nonabsorbing host polymer side chains. A correlation is found between azobenzene photoinduced molecular orientation and macroscopic all-optical surface patterning efficiency. The improved performance of halogen-bonded systems in photopatterning applications can be related to the absence of a plasticizing effect on the polymer matrix, which may enable the material to retain an optimal glass transition temperature, in contrast to hydrogen-bonded and nonbonded references. Thus, our results provide design guidelines in terms of the nature and strength of the supramolecular interaction and of the degree of azo functionalization needed to optimize the motion transfer to passive polymers.
@article{vapaavuori_photomechanical_2015, title = {Photomechanical {Energy} {Transfer} to {Photopassive} {Polymers} through {Hydrogen} and {Halogen} {Bonds}}, volume = {48}, doi = {10.1021/acs.macromol.5b01813}, abstract = {The supramolecular assembly of photoactive azobenzenes with passive polymers via halogen or hydrogen bonding is a cost-effective way to design materials for various photomechanical applications that convert light energy directly into macroscopic motion, for instance, in all-optical surface patterning and photochemical imaging of plasmonic structures. To elucidate the molecular-level origins of this motion, we show, by coupling dynamic infrared spectroscopy to a photo-orientation setup, that supramolecular bonds above a certain interaction strength threshold are photostable under vigorous photoisomerization cycling and capable of translating the photo-orientation of azobenzenes into the orientation of nonabsorbing host polymer side chains. A correlation is found between azobenzene photoinduced molecular orientation and macroscopic all-optical surface patterning efficiency. The improved performance of halogen-bonded systems in photopatterning applications can be related to the absence of a plasticizing effect on the polymer matrix, which may enable the material to retain an optimal glass transition temperature, in contrast to hydrogen-bonded and nonbonded references. Thus, our results provide design guidelines in terms of the nature and strength of the supramolecular interaction and of the degree of azo functionalization needed to optimize the motion transfer to passive polymers.}, journal = {Macromolecules}, author = {Vapaavuori, Jaana and Heikkinen, Ismo T.S. and Dichiarante, Valentina and Resnati, Giuseppe and Metrangolo, Pierangelo and Sabat, Ribal Georges and Bazuin, C. Geraldine and Priimagi, Arri and Pellerin, Christian}, month = oct, year = {2015}, pages = {7535--7542}, } - J. Wang, Y. Aihara, M. Kinoshita, J. I. Mamiya, A. Priimagi, and A. Shishido, “Laser-pointer-induced self-focusing effect in hybrid-aligned dye-doped liquid crystals,” Scientific Reports, vol. 5, p. 9890, 2015. doi:10.1038/srep09890
[BibTeX] [Abstract]
Nonlinear optics deals with phenomena where “light controls light”; e.g., there is mediation by an intensity-dependent medium through which light propagates. This field has attracted much attention for its immense potential in applications dependent on nonlinear processes, such as frequency conversion, multiple-photon absorption, self-phase modulation, and so on. However, such nonlinearities are typically only observed at very high light intensities and thus they require costly lasers. Here, we report on a self-focusing effect induced with a 1 mW handheld laser pointer. We prepared polymer-stabilized dye-doped liquid crystals, in which the molecular director orientation gradually changes from homeotropic at one surface to homogeneous at the other. This is referred to as hybrid alignment. In such films, the threshold intensity needed to form diffraction rings was reduced by a factor of 8.5 compared to that in conventional homeotropic cells, which enabled the induction of the self-focusing effect with a laser pointer.
@article{wang_laser-pointer-induced_2015, title = {Laser-pointer-induced self-focusing effect in hybrid-aligned dye-doped liquid crystals}, volume = {5}, doi = {10.1038/srep09890}, abstract = {Nonlinear optics deals with phenomena where "light controls light"; e.g., there is mediation by an intensity-dependent medium through which light propagates. This field has attracted much attention for its immense potential in applications dependent on nonlinear processes, such as frequency conversion, multiple-photon absorption, self-phase modulation, and so on. However, such nonlinearities are typically only observed at very high light intensities and thus they require costly lasers. Here, we report on a self-focusing effect induced with a 1 mW handheld laser pointer. We prepared polymer-stabilized dye-doped liquid crystals, in which the molecular director orientation gradually changes from homeotropic at one surface to homogeneous at the other. This is referred to as hybrid alignment. In such films, the threshold intensity needed to form diffraction rings was reduced by a factor of 8.5 compared to that in conventional homeotropic cells, which enabled the induction of the self-focusing effect with a laser pointer.}, journal = {Scientific Reports}, author = {Wang, Jing and Aihara, Yosuke and Kinoshita, Motoi and Mamiya, Jun Ichi and Priimagi, Arri and Shishido, Atsushi}, month = sep, year = {2015}, pages = {9890}, } - M. Saccone, G. Cavallo, P. Metrangolo, G. Resnati, and A. Priimagi, “Halogen-bonded photoresponsive materials,” Topics in Current Chemistry, vol. 359, pp. 147-166, 2015. doi:10.1007/128_2014_615
[BibTeX] [Abstract]
The aim of the present review is to illustrate to the reader the state of the art on the construction of supramolecular azobenzene-containing materials formed by halogen bonding. These materials include several examples of polymeric, liquid crystalline or crystalline species whose performances are either superior to the corresponding performances of their hydrogen-bonded analogues or simply distinctive of the halogen-bonded species.
@article{saccone_halogen-bonded_2015, title = {Halogen-bonded photoresponsive materials}, volume = {359}, doi = {10.1007/128_2014_615}, abstract = {The aim of the present review is to illustrate to the reader the state of the art on the construction of supramolecular azobenzene-containing materials formed by halogen bonding. These materials include several examples of polymeric, liquid crystalline or crystalline species whose performances are either superior to the corresponding performances of their hydrogen-bonded analogues or simply distinctive of the halogen-bonded species.}, journal = {Topics in Current Chemistry}, author = {Saccone, Marco and Cavallo, Gabriella and Metrangolo, Pierangelo and Resnati, Giuseppe and Priimagi, Arri}, month = mar, year = {2015}, pages = {147--166}, } - M. Virkki, O. Tuominen, A. Forni, M. Saccone, P. Metrangolo, G. Resnati, M. Kauranen, and A. Priimagi, “Halogen bonding enhances nonlinear optical response in poled supramolecular polymers,” Journal of Materials Chemistry C, vol. 3, pp. 3003-3006, 2015. doi:10.1039/c5tc00484e
[BibTeX] [Abstract]
We demonstrate that halogen bonding strongly enhances the nonlinear optical response of poled supramolecular polymer systems. We compare three nonlinear optical chromophores with similar electronic structures but different bond-donating units, and show that both the type and the strength of the noncovalent interaction between the chromophores and the polymer matrix play their own distinctive roles in the optical nonlinearity of the systems.
@article{virkki_halogen_2015, title = {Halogen bonding enhances nonlinear optical response in poled supramolecular polymers}, volume = {3}, doi = {10.1039/c5tc00484e}, abstract = {We demonstrate that halogen bonding strongly enhances the nonlinear optical response of poled supramolecular polymer systems. We compare three nonlinear optical chromophores with similar electronic structures but different bond-donating units, and show that both the type and the strength of the noncovalent interaction between the chromophores and the polymer matrix play their own distinctive roles in the optical nonlinearity of the systems.}, journal = {Journal of Materials Chemistry C}, author = {Virkki, Matti and Tuominen, Ossi and Forni, Alessandra and Saccone, Marco and Metrangolo, Pierangelo and Resnati, Giuseppe and Kauranen, Martti and Priimagi, Arri}, month = mar, year = {2015}, pages = {3003--3006}, } - J. Vapaavuori, R. H. A. Ras, M. Kaivola, G. C. Bazuin, and A. Priimagi, “From partial to complete optical erasure of azobenzene-polymer gratings: Effect of molecular weight,” Journal of Materials Chemistry C, vol. 3, pp. 11011-11016, 2015. doi:10.1039/c5tc01776a
[BibTeX] [Abstract]
The ability to control surface functionality by optical inscription and erasure of surface patterns is highly appealing, since it opens up the possibility for the design of complex, spatially varying surface topographies. We show through a supramolecular approach, which allows us to attach nominally equal amounts of azobenzene into polymers of varying molecular weight, that the completeness of optical erasure of high-modulation-depth surface-relief gratings on polymer-azobenzene complexes depends on the molecular weight of the polymer, and therefore on the glass transition temperature of the material used. The optical erasure is further applied to realize surface patterns with varying grating vector directions through masking. All patterning is done at a temperature well below the glass transition temperatures of the materials, which allows different patterning steps to be frozen into the material.
@article{vapaavuori_partial_2015, title = {From partial to complete optical erasure of azobenzene-polymer gratings: {Effect} of molecular weight}, volume = {3}, doi = {10.1039/c5tc01776a}, abstract = {The ability to control surface functionality by optical inscription and erasure of surface patterns is highly appealing, since it opens up the possibility for the design of complex, spatially varying surface topographies. We show through a supramolecular approach, which allows us to attach nominally equal amounts of azobenzene into polymers of varying molecular weight, that the completeness of optical erasure of high-modulation-depth surface-relief gratings on polymer-azobenzene complexes depends on the molecular weight of the polymer, and therefore on the glass transition temperature of the material used. The optical erasure is further applied to realize surface patterns with varying grating vector directions through masking. All patterning is done at a temperature well below the glass transition temperatures of the materials, which allows different patterning steps to be frozen into the material.}, journal = {Journal of Materials Chemistry C}, author = {Vapaavuori, Jaana and Ras, Robin H.A. and Kaivola, Matti and Bazuin, C. Geraldine and Priimagi, Arri}, year = {2015}, pages = {11011--11016}, }
2014
- J. E. Koskela, J. Vapaavuori, R. H. A. Ras, and A. Priimagi, “Light-driven surface patterning of supramolecular polymers with extremely low concentration of photoactive molecules,” ACS Macro Letters, vol. 3, pp. 1196-1200, 2014. doi:10.1021/mz500616q
[BibTeX] [Abstract]
Light-induced surface patterning in azobenzene-containing polymers and other materials is a widely studied phenomenon with possible applications in fields ranging from photonics to biology. Yet, the fundamental understanding of this purely photodriven mass transport remains inadequate, and existing literature fails to define a threshold chromophore content for mass transport to occur, if such a limit exists. This letter presents a systematic study of the relationship between chromophore concentration and mass transport using hydrogen-bonded polymer-azobenzene complexes, in which the chromophore concentration can be freely adjusted while keeping the polymer backbone unchanged. Essentially, we demonstrate that effective surface patterning can be induced even at an extremely low chromophore content of 1 mol \%, when only every tenth polymer chain carries a single azobenzene molecular motor. Importantly, the results highlight the extraordinary photomechanical power of azobenzene and contribute to the fundamental understanding of the light-induced motions.
@article{koskela_light-driven_2014, title = {Light-driven surface patterning of supramolecular polymers with extremely low concentration of photoactive molecules}, volume = {3}, doi = {10.1021/mz500616q}, abstract = {Light-induced surface patterning in azobenzene-containing polymers and other materials is a widely studied phenomenon with possible applications in fields ranging from photonics to biology. Yet, the fundamental understanding of this purely photodriven mass transport remains inadequate, and existing literature fails to define a threshold chromophore content for mass transport to occur, if such a limit exists. This letter presents a systematic study of the relationship between chromophore concentration and mass transport using hydrogen-bonded polymer-azobenzene complexes, in which the chromophore concentration can be freely adjusted while keeping the polymer backbone unchanged. Essentially, we demonstrate that effective surface patterning can be induced even at an extremely low chromophore content of 1 mol \%, when only every tenth polymer chain carries a single azobenzene molecular motor. Importantly, the results highlight the extraordinary photomechanical power of azobenzene and contribute to the fundamental understanding of the light-induced motions.}, journal = {ACS Macro Letters}, author = {Koskela, Jenni E. and Vapaavuori, Jaana and Ras, Robin H.A. and Priimagi, Arri}, month = nov, year = {2014}, pages = {1196--1200}, } - A. Sobolewska, S. Bartkiewicz, and A. Priimagi, “High-Modulation-Depth Surface Relief Gratings Using s–s Polarization Configuration in Supramolecular Polymer–Azobenzene Complexes,” The Journal of Physical Chemistry C, vol. 118, pp. 23279-23284, 2014. doi:10.1021/jp507486x
[BibTeX] [Abstract]
The formation of the surface relief gratings (SRG) in azo-polymers strongly depends on the polarization configuration of the writing beams. So far the s−s polarization configuration has been considered as ineffective in terms of SRG formation. Here, we report that very high-amplitude SRGs can be recorded when using the s−s inscription geometry in supramolecular polymer−azobenzene complexes and that the efficiency of the process strongly depends on the molecular weight of the polymer. Furthermore, a single holographic irradiation leads to the formation of the surface relief grating (primary grating) and, unexpectedly, to the formation of the secondary fine-structure grating with a considerable modulation depth in the direction perpendicular to the primary grating. The detailed analysis of holographic recording has been performed on the basis of the proposed phenomenological model. A new aspect of the phenomenon of the SRG formation has been indicated by demonstrating that the SRG can be inscribed for the s−s polarization configuration. Since the SRG formation is considered as an important new tool in micro/nanofabrication technologies, both the formation of the SRG for s−s geometry and the formation of the fine-structure grating open new possibilities in photonic applications.
@article{sobolewska_high-modulation-depth_2014, title = {High-{Modulation}-{Depth} {Surface} {Relief} {Gratings} {Using} s–s {Polarization} {Configuration} in {Supramolecular} {Polymer}–{Azobenzene} {Complexes}}, volume = {118}, doi = {10.1021/jp507486x}, abstract = {The formation of the surface relief gratings (SRG) in azo-polymers strongly depends on the polarization configuration of the writing beams. So far the s−s polarization configuration has been considered as ineffective in terms of SRG formation. Here, we report that very high-amplitude SRGs can be recorded when using the s−s inscription geometry in supramolecular polymer−azobenzene complexes and that the efficiency of the process strongly depends on the molecular weight of the polymer. Furthermore, a single holographic irradiation leads to the formation of the surface relief grating (primary grating) and, unexpectedly, to the formation of the secondary fine-structure grating with a considerable modulation depth in the direction perpendicular to the primary grating. The detailed analysis of holographic recording has been performed on the basis of the proposed phenomenological model. A new aspect of the phenomenon of the SRG formation has been indicated by demonstrating that the SRG can be inscribed for the s−s polarization configuration. Since the SRG formation is considered as an important new tool in micro/nanofabrication technologies, both the formation of the SRG for s−s geometry and the formation of the fine-structure grating open new possibilities in photonic applications.}, journal = {The Journal of Physical Chemistry C}, author = {Sobolewska, A and Bartkiewicz, S and Priimagi, Arri}, month = sep, year = {2014}, pages = {23279--23284}, } - J. Vapaavuori, A. Goulet-Hanssens, I. T. S. Heikkinen, C. J. Barrett, and A. Priimagi, “Are Two Azo Groups Better than One? Investigating the Photoresponse of Polymer-Bisazobenzene Complexes,” Chemistry of Materials, vol. 26, pp. 5089-5096, 2014. doi:10.1021/cm5023129
[BibTeX] [Abstract]
Azobenzene chromophores are an ideal choice for material applications where functionality needs to be activated in a precise remote-controlled fashion. The azobenzene stimuli-response falls into two categories, either based on efficient trans-to-cis photoisomerization and a high cis yield enabling on−off type functions, or relying on a fast trans−cis−trans cycling creating motion in the material system. Herein, we show that using bisazochromophores instead of the more common monoazobenzene derivatives makes a difference in the performance of light-responsive azopolymers, more specifically in photo-orientation and all-optical surface patterning. Our findings point out that polymer-bisazobenzene complexes are an attractive alternative as high-performance photoreponsive materials and that although their properties are highly sensitive to the extent of conjugation in the system, they can be designed into relatively transparent films with high performance for all-optical patterning.
@article{vapaavuori_are_2014, title = {Are {Two} {Azo} {Groups} {Better} than {One}? {Investigating} the {Photoresponse} of {Polymer}-{Bisazobenzene} {Complexes}}, volume = {26}, doi = {10.1021/cm5023129}, abstract = {Azobenzene chromophores are an ideal choice for material applications where functionality needs to be activated in a precise remote-controlled fashion. The azobenzene stimuli-response falls into two categories, either based on efficient trans-to-cis photoisomerization and a high cis yield enabling on−off type functions, or relying on a fast trans−cis−trans cycling creating motion in the material system. Herein, we show that using bisazochromophores instead of the more common monoazobenzene derivatives makes a difference in the performance of light-responsive azopolymers, more specifically in photo-orientation and all-optical surface patterning. Our findings point out that polymer-bisazobenzene complexes are an attractive alternative as high-performance photoreponsive materials and that although their properties are highly sensitive to the extent of conjugation in the system, they can be designed into relatively transparent films with high performance for all-optical patterning.}, journal = {Chemistry of Materials}, author = {Vapaavuori, Jaana and Goulet-Hanssens, Alexis and Heikkinen, Ismo T S and Barrett, Christopher J and Priimagi, Arri}, month = aug, year = {2014}, pages = {5089--5096}, } - A. Goulet-Hanssens, C. T. Corkery, A. Priimagi, and C. J. Barrett, “Effect of head group size on the photoswitching applications of azobenzene Disperse Red 1 analogues,” Journal of Materials Chemistry C, vol. 2, pp. 7505-7512, 2014. doi:10.1039/C4TC00996G
[BibTeX] [Abstract]
We investigate the effect of the increased molecular bulk in the `head’ group for a class of newly synthesized azobenzene chromophores with a clickable ethynyl group para and a nitro group ortho to the azo bond on the distal benzene ring. This `variable-head’ functionalization provides a family of dyes with photophysical characteristics very similar to those of Disperse Red 1, one of the most commonly used azo dyes in materials science. Phenyl, naphthyl, and anthracyl derivatives were synthesized as small molecules, monomers, homopolymers, and copolymers in a rapid and facile manner using click chemistry, confirming the versatility of this parent chromophore. Photochemical and spectral studies indicate that this strategy is suitable to build a `bulkiness series’ of stimuli-responsive materials, as the various material derivatives retain the absorption and kinetic characteristics of the parent chromophore necessary for all optical patterning applications that DR1 dyes have been optimized for. In thin films, larger head group size was found to increase the stability of light-induced birefringence in copolymers. The homopolymers formed stable surface-relief gratings upon interference irradiation, whose grating depths correlate with head group size, demonstrating that this new class of polymers can also undergo tailored macroscopic photoinduced motions, which could have applications in all optical nano-patterning.
@article{goulet-hanssens_effect_2014, title = {Effect of head group size on the photoswitching applications of azobenzene {Disperse} {Red} 1 analogues}, volume = {2}, doi = {10.1039/C4TC00996G}, abstract = {We investigate the effect of the increased molecular bulk in the `head' group for a class of newly synthesized azobenzene chromophores with a clickable ethynyl group para and a nitro group ortho to the azo bond on the distal benzene ring. This `variable-head' functionalization provides a family of dyes with photophysical characteristics very similar to those of Disperse Red 1, one of the most commonly used azo dyes in materials science. Phenyl, naphthyl, and anthracyl derivatives were synthesized as small molecules, monomers, homopolymers, and copolymers in a rapid and facile manner using click chemistry, confirming the versatility of this parent chromophore. Photochemical and spectral studies indicate that this strategy is suitable to build a `bulkiness series' of stimuli-responsive materials, as the various material derivatives retain the absorption and kinetic characteristics of the parent chromophore necessary for all optical patterning applications that DR1 dyes have been optimized for. In thin films, larger head group size was found to increase the stability of light-induced birefringence in copolymers. The homopolymers formed stable surface-relief gratings upon interference irradiation, whose grating depths correlate with head group size, demonstrating that this new class of polymers can also undergo tailored macroscopic photoinduced motions, which could have applications in all optical nano-patterning.}, journal = {Journal of Materials Chemistry C}, author = {Goulet-Hanssens, Alexis and Corkery, T Christopher and Priimagi, Arri and Barrett, Christopher J}, month = aug, year = {2014}, pages = {7505--7512}, } - A. Priimagi, C. J. Barrett, and A. Shishido, “Recent twists in photoactuation and photoalignment control,” Journal of Materials Chemistry C, vol. 2, pp. 7155-7162, 2014. doi:10.1039/C4TC01236D
[BibTeX] [Abstract]
The design of functional and stimuli-responsive materials is among the key goals of modern materials science. The structure and properties of such materials can be controlled via various stimuli, among which light is often times the most attractive choice. Light is ubiquitous and a gentle energy source and its properties can be optimized for a specific target remotely, with high spatial and temporal resolution. Light-control over molecular alignment has in recent years attracted particular interest, for potential applications such as reconfigurable photonic elements and optical-to-mechanical energy conversion. Herein, we bring forward some recent examples and emerging trends in this exciting field of research, focusing on liquid crystals, liquid-crystalline polymers and photochromic organic crystals, which we believe serve to highlight the immense potential of light-responsive materials to a wide variety of current and future high-tech applications in photonics, energy harvesting and conversion.
@article{priimagi_recent_2014, title = {Recent twists in photoactuation and photoalignment control}, volume = {2}, doi = {10.1039/C4TC01236D}, abstract = {The design of functional and stimuli-responsive materials is among the key goals of modern materials science. The structure and properties of such materials can be controlled via various stimuli, among which light is often times the most attractive choice. Light is ubiquitous and a gentle energy source and its properties can be optimized for a specific target remotely, with high spatial and temporal resolution. Light-control over molecular alignment has in recent years attracted particular interest, for potential applications such as reconfigurable photonic elements and optical-to-mechanical energy conversion. Herein, we bring forward some recent examples and emerging trends in this exciting field of research, focusing on liquid crystals, liquid-crystalline polymers and photochromic organic crystals, which we believe serve to highlight the immense potential of light-responsive materials to a wide variety of current and future high-tech applications in photonics, energy harvesting and conversion.}, journal = {Journal of Materials Chemistry C}, author = {Priimagi, Arri and Barrett, Christopher J and Shishido, Atsushi}, month = jun, year = {2014}, pages = {7155--7162}, } - N. Akamatsu, W. Tashiro, K. Saito, J. Mamiya, M. Kinoshita, T. Ikeda, J. Takeya, S. Fujikawa, A. Priimagi, and A. Shishido, “Facile strain analysis of largely bending films by a surface-labelled grating method,” Scientific Reports, vol. 4, p. 5377, 2014. doi:10.1038/srep05377
[BibTeX] [Abstract]
Mechanical properties of flexible films, for example surface strain of largely bending films, are key to design of stretchable electronic devices, wearable biointegrated devices, and soft microactuators/robots. However, existing methods are mainly based on strain-gauge measurements that require miniaturized array sensors, lead wires, and complicated calibrations. Here we introduce a facile method, based on surface-labelled gratings, for two-dimensional evaluation of surface strains in largely bending films. With this technique, we demonstrate that soft-matter mechanics can be distinct from the mechanics of hard materials. In particular, liquid-crystalline elastomers may undergo unconventional bending in three dimensions, in which both the inner and outer surfaces of the bending film are compressed. We also show that this method can be applied to amorphous elastomeric films, which highlights the general importance of this new mechanical evaluation tool in designing soft-matter-based electronic/photonic as well as biointegrated materials.
@article{akamatsu_facile_2014, title = {Facile strain analysis of largely bending films by a surface-labelled grating method}, volume = {4}, doi = {10.1038/srep05377}, abstract = {Mechanical properties of flexible films, for example surface strain of largely bending films, are key to design of stretchable electronic devices, wearable biointegrated devices, and soft microactuators/robots. However, existing methods are mainly based on strain-gauge measurements that require miniaturized array sensors, lead wires, and complicated calibrations. Here we introduce a facile method, based on surface-labelled gratings, for two-dimensional evaluation of surface strains in largely bending films. With this technique, we demonstrate that soft-matter mechanics can be distinct from the mechanics of hard materials. In particular, liquid-crystalline elastomers may undergo unconventional bending in three dimensions, in which both the inner and outer surfaces of the bending film are compressed. We also show that this method can be applied to amorphous elastomeric films, which highlights the general importance of this new mechanical evaluation tool in designing soft-matter-based electronic/photonic as well as biointegrated materials.}, journal = {Scientific Reports}, author = {Akamatsu, Norihisa and Tashiro, Wataru and Saito, Keisuke and Mamiya, Jun-ichi and Kinoshita, Motoi and Ikeda, Tomiki and Takeya, Jun and Fujikawa, Shigenori and Priimagi, Arri and Shishido, Atsushi}, month = jun, year = {2014}, pages = {5377}, } - J. E. Koskela, V. Liljeström, J. Lim, E. E. Simanek, R. H. A. Ras, A. Priimagi, and M. A. Kostiainen, “Light-Fuelled Transport of Large Dendrimers and Proteins,” Journal of the American Chemical Society, vol. 136, pp. 6850-6853, 2014. doi:10.1021/ja502623m
[BibTeX] [Abstract]
This work presents a facile water-based supramolecular approach for light-induced surface patterning. The method is based upon azobenzene-functionalized high-molecular weight triazine dendrimers up to generation 9, demonstrating that even very large globular supramolecular complexes can be made to move in response to light. We also demonstrate light-fuelled macroscopic movements in native biomolecules, showing that complexes of apoferritin protein and azobenzene can effectively form light-induced surface patterns. Fundamentally, the results establish that thin films comprising both flexible and rigid globular particles of large diameter can be moved with light, whereas the presented material concepts offer new possibilities for the yet marginally explored biological applications of azobenzene surface patterning.
@article{koskela_light-fuelled_2014, title = {Light-{Fuelled} {Transport} of {Large} {Dendrimers} and {Proteins}}, volume = {136}, doi = {10.1021/ja502623m}, abstract = {This work presents a facile water-based supramolecular approach for light-induced surface patterning. The method is based upon azobenzene-functionalized high-molecular weight triazine dendrimers up to generation 9, demonstrating that even very large globular supramolecular complexes can be made to move in response to light. We also demonstrate light-fuelled macroscopic movements in native biomolecules, showing that complexes of apoferritin protein and azobenzene can effectively form light-induced surface patterns. Fundamentally, the results establish that thin films comprising both flexible and rigid globular particles of large diameter can be moved with light, whereas the presented material concepts offer new possibilities for the yet marginally explored biological applications of azobenzene surface patterning.}, journal = {Journal of the American Chemical Society}, author = {Koskela, Jenni E and Liljeström, Ville and Lim, Jongdoo and Simanek, Eric E and Ras, Robin H A and Priimagi, Arri and Kostiainen, Mauri A}, month = may, year = {2014}, pages = {6850--6853}, } - M. Saccone, G. Terraneo, T. Pilati, G. Cavallo, A. Priimagi, P. Metrangolo, and G. Resnati, “Azobenzene-based difunctional halogen-bond donor: towards the engineering of photoresponsive co-crystals,” Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials, vol. 70, pp. 149-156, 2014. doi:10.1107/S205252061302622X
[BibTeX] [Abstract]
Halogen bonding is emerging as a powerful non-covalent interaction in the context of supramolecular photoresponsive materials design, particularly due to its high directionality. In order to obtain further insight into the solid-state features of halogen-bonded photoactive molecules, three halogen- bonded co-crystals containing an azobenzene-based difunctional halogen-bond donor molecule, (E)-bis(4-iodo-2,3,5,6- tetrafluorophenyl)diazene, C12F8I2N2, have been synthesized and structurally characterized by single-crystal X-ray diffraction. The crystal structure of the non-iodinated homologue (E)-bis(2,3,5,6-tetrafluorophenyl)diazene, C12H2F8N2, is also reported. It is demonstrated that the studied halogen-bond donor molecule is a reliable tecton for assembling halogen- bonded co-crystals with potential photoresponsive behaviour. The azo group is not involved in any specific intermolecular interactions in any of the co-crystals studied, which is an interesting feature in the context of enhanced photoisomerization behaviour and photoactive properties of the material systems.
@article{saccone_azobenzene-based_2014, title = {Azobenzene-based difunctional halogen-bond donor: towards the engineering of photoresponsive co-crystals}, volume = {70}, doi = {10.1107/S205252061302622X}, abstract = {Halogen bonding is emerging as a powerful non-covalent interaction in the context of supramolecular photoresponsive materials design, particularly due to its high directionality. In order to obtain further insight into the solid-state features of halogen-bonded photoactive molecules, three halogen- bonded co-crystals containing an azobenzene-based difunctional halogen-bond donor molecule, (E)-bis(4-iodo-2,3,5,6- tetrafluorophenyl)diazene, C12F8I2N2, have been synthesized and structurally characterized by single-crystal X-ray diffraction. The crystal structure of the non-iodinated homologue (E)-bis(2,3,5,6-tetrafluorophenyl)diazene, C12H2F8N2, is also reported. It is demonstrated that the studied halogen-bond donor molecule is a reliable tecton for assembling halogen- bonded co-crystals with potential photoresponsive behaviour. The azo group is not involved in any specific intermolecular interactions in any of the co-crystals studied, which is an interesting feature in the context of enhanced photoisomerization behaviour and photoactive properties of the material systems.}, journal = {Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials}, author = {Saccone, Marco and Terraneo, Giancarlo and Pilati, Tullio and Cavallo, Gabriella and Priimagi, Arri and Metrangolo, Pierangelo and Resnati, Giuseppe}, month = mar, year = {2014}, pages = {149--156}, } - A. Priimagi and A. Shevchenko, “Azopolymer-based micro- and nanopatterning for photonic applications,” Journal of Polymer Science Part B: Polymer Physics, vol. 52, pp. 163-182, 2014. doi:10.1002/polb.23390
[BibTeX] [Abstract]
Azopolymers comprise a unique materials platform, in which the photoisomerization reaction of azobenzene mole- cules can induce substantial material motions at molecular, mesoscopic, and even macroscopic length scales. In particular, amorphous azopolymer films can form stable surface relief patterns upon exposure to interfering light. This allows obtaining large-area periodic micro- and nanostructures in a remarkably simple way. Herein, recent progress in the development of azopolymer-based surface-patterning techniques for photonic applications is reviewed. Starting with a thin azopolymer layer, one can create a variety of photonic elements, such as diffraction gratings, microlens arrays, plasmonic sensors, antireflection coatings, and nanostructured light-polarization converters, either by using the azopolymer surface patterns themselves as optical elements or by utilizing them to microstructure or nanostructure other materials. Both of these domains are cov- ered, with the aim of triggering further research in this fascinating field of science and technology that is far from being harnessed.
@article{priimagi_azopolymer-based_2014, title = {Azopolymer-based micro- and nanopatterning for photonic applications}, volume = {52}, doi = {10.1002/polb.23390}, abstract = {Azopolymers comprise a unique materials platform, in which the photoisomerization reaction of azobenzene mole- cules can induce substantial material motions at molecular, mesoscopic, and even macroscopic length scales. In particular, amorphous azopolymer films can form stable surface relief patterns upon exposure to interfering light. This allows obtaining large-area periodic micro- and nanostructures in a remarkably simple way. Herein, recent progress in the development of azopolymer-based surface-patterning techniques for photonic applications is reviewed. Starting with a thin azopolymer layer, one can create a variety of photonic elements, such as diffraction gratings, microlens arrays, plasmonic sensors, antireflection coatings, and nanostructured light-polarization converters, either by using the azopolymer surface patterns themselves as optical elements or by utilizing them to microstructure or nanostructure other materials. Both of these domains are cov- ered, with the aim of triggering further research in this fascinating field of science and technology that is far from being harnessed.}, journal = {Journal of Polymer Science Part B: Polymer Physics}, author = {Priimagi, Arri and Shevchenko, Andriy}, month = feb, year = {2014}, pages = {163--182}, } - R. J. Moerland, J. E. Koskela, A. Kravchenko, M. Simberg, S. van der Vegte, M. Kaivola, A. Priimagi, and R. H. A. Ras, “Large-area arrays of three-dimensional plasmonic subwavelength-sized structures from azopolymer surface-relief gratings,” Materials Horizons, vol. 1, pp. 74-80, 2014. doi:10.1039/c3mh00008g
[BibTeX] [Abstract]
The field of plasmonics allows for confinement and control of light on the nanoscale. Due to potentially strong resonant interactions that light can have with metal nanoscale structures, metals are a good candidate to tailor interactions with light, e.g., periodic arrays of subwavelength metal structures can support extremely narrow reso- nances and show enhanced transmission. The field of plasmonics has evolved from using simple geometries to the desire to create complex nanostructures for improved control. The availability of fabrication techniques that provide for complex structures, however, is paired with the seemingly inevitable increase in complexity of fabrication techniques themselves. We present a facile and scalable method for the fabrication of periodic arrays of unique three-dimensional sub- wavelength-sized structures such as tapered holes and pyramidically shaped subwavelength-sized particles. The procedure consists of holographic inscription of a two-dimensional surface-relief grating in an azobenzene-containing polymer film, evaporative gold deposition and broad-beam ion milling of the relief structure. The method allows the fabrication of highly uniform arrays with tunable lattice parameters and dimensions over large sample areas. The optical response of the fabricated structures is determined experimentally and through simulation, which confirm the unique plasmonic response of the structures. While the proposed fabrication method has clear benefits for plasmonics, it could easily be applied also in other fields, for example by using other coating materials.
@article{moerland_large-area_2014, title = {Large-area arrays of three-dimensional plasmonic subwavelength-sized structures from azopolymer surface-relief gratings}, volume = {1}, doi = {10.1039/c3mh00008g}, abstract = {The field of plasmonics allows for confinement and control of light on the nanoscale. Due to potentially strong resonant interactions that light can have with metal nanoscale structures, metals are a good candidate to tailor interactions with light, e.g., periodic arrays of subwavelength metal structures can support extremely narrow reso- nances and show enhanced transmission. The field of plasmonics has evolved from using simple geometries to the desire to create complex nanostructures for improved control. The availability of fabrication techniques that provide for complex structures, however, is paired with the seemingly inevitable increase in complexity of fabrication techniques themselves. We present a facile and scalable method for the fabrication of periodic arrays of unique three-dimensional sub- wavelength-sized structures such as tapered holes and pyramidically shaped subwavelength-sized particles. The procedure consists of holographic inscription of a two-dimensional surface-relief grating in an azobenzene-containing polymer film, evaporative gold deposition and broad-beam ion milling of the relief structure. The method allows the fabrication of highly uniform arrays with tunable lattice parameters and dimensions over large sample areas. The optical response of the fabricated structures is determined experimentally and through simulation, which confirm the unique plasmonic response of the structures. While the proposed fabrication method has clear benefits for plasmonics, it could easily be applied also in other fields, for example by using other coating materials.}, journal = {Materials Horizons}, author = {Moerland, Robert J and Koskela, Jenni E and Kravchenko, Aleksandr and Simberg, Mikael and van der Vegte, Stefan and Kaivola, Matti and Priimagi, Arri and Ras, Robin H A}, month = jan, year = {2014}, pages = {74--80}, }