2022 publications

First-cycle oscillation excursions of Pickering-stabilised microbubbles subjected to a high-amplitude ultrasound pulse by Nicole Anderton, Craig S. Carlson, Ryunosuke Matsumoto, Ri-ichiro Shimizu, Albert T. Poortinga, Nobuki Kudo, and Michiel Postema was published in the 8th volume of Current Directions in Biomedical Engineering in 2022.
Pickering stabilisation is a manufacturing process involving the adsorption of colloidal particles at gas–liquid interfaces. The purpose of the present study is to determine whether high-amplitude sonication influences the integrity of Pickering-stabilised shells. The results indicate that optically identical microbubbles may undergo shell disruption of different severity.
This study was a collaborative work of Tampere University, the University of the Witwatersrand, Johannesburg, Hokkaido University, and Eindhoven University of Technology.

Radius measured as a function of time for a Pickering-stabilised microbuble (o), simulated R(t) curves of a free (—) and a shell-stabilised () microbubble, and inlays extracted from high-speed video footage.

Monitoring the gelation of gellan gum with torsion rheometry and brightness-mode ultrasound by Michiel Postema, Christine Gering, Nicole Anderton, Craig S. Carlson, and Minna Kellomäki was published in the 8th volume of Current Directions in Biomedical Engineering in 2022.
Gellan gum is a hydrogel with several applications in ultrasonic imaging, novel drug delivery, and tissue regeneration. As hydrogels are dynamic entities, their viscocelastic and therefore their acoustic properties change over time, which is of interest to monitor. To determine the speed of sound from brightness-mode images, however, rather large quantities of hydrogel are needed. In this study, we investigated torsion rheometry as a means to determine acoustic properties.
This study was a collaborative work of Tampere University, and the University of the Witwatersrand, Johannesburg.

Perceived speed of sound of gellan gum as a function of time.

Micro-computed tomography and brightness-mode ultrasound show air entrapments inside tablets by Craig S. Carlson, Markus Hannula, and Michiel Postema was published in the 8th volume of Current Directions in Biomedical Engineering in 2022.
Controlled disintegration of pharmaceutical tablets has been of interest for consistency checks and drug delivery. Under sonication, tablet disintegration is accelerated. This acceleration has been attributed to the existence of microscopic air pockets inside compacted tablets. In this study, we investigated the existence of such pockets by subjecting tablets to micro-computed tomography.
This study was a collaborative work of Tampere University, and the University of the Witwatersrand, Johannesburg.

Tomographic micro-computed tomography image showing a three-dimensional representation of a tablet cross-section.

Fragmentation thresholds simulated for antibubbles with various infinitesimal elastic shells by Nicole Anderton, and Michiel Postema was published in the 8th volume of Current Directions in Biomedical Engineering in 2022.
Antibubbles are small gas bubbles comprising one or multiple liquid or solid cores, typically surrounded by stabilising shells. Acoustically active microscopic antibubbles have been proposed for use as theranostic agents. For clinical applications such as ultrasound-guided drug delivery and flash-echo, it is relevant to know the fragmentation threshold of antibubbles and the influence of the stabilising shells thereon.
This study was a collaborative work of Tampere University, and the University of the Witwatersrand, Johannesburg.

Fragmentation threshold in MI as a function of driving frequency, simulated for a 3-μm radius antibubble with a 90% core radius.

“Are you breathing?” – Design, build and testing of a low-cost, portable respiratory rate monitor by Junaid Dawood, Matthew Muller, and Craig S. Carlson was published in the 8th volume of Current Directions in Biomedical Engineering in 2022.
A patient’s respiratory rate is one of the critical vital signs that is a determinant of patient well-being. However, it is all too often neglected or misreported by health care professionals. This study presents the design, build and testing of a low-cost, portable monitor to facilitate accurate reporting of respiratory rate.
This study was a collaborative work of Tampere University, and the University of the Witwatersrand, Johannesburg.

Photograph of the respiratory rate monitor that was designed, built, and tested.

Experimental setup for the ultrasonic fractionation of flowing whole blood in a capillary by Charl Smalberger, Malavika Nathan, David M. Rubin, Marietha Nel, Spiros Kotopoulis, Craig S. Carlson, and Michiel Postema was published in the 8th volume of Current Directions in Biomedical Engineering in 2022.
If a long ultrasound driving pulse is chosen such, that its frequency is greater than the resonance frequency of one cell type and less than the resonance frequency of another cell type, the cells are separated in different nodes and antinodes of the standing sound field. The purpose of this study was to build an experimental setup for the ultrasonic fractionation of whole blood in flow conditions.
This study was a collaborative work of Tampere University, the University of the Witwatersrand, Johannesburg, and the University of Bergen.

Schematic top-view representation of ultrasonic cell separation in a capillary before (a) and after (b) sonication with a single-element transducer.

Determining the influence of endoskeleton friction on the damping of pulsating antibubbles by Nicole Anderton, Craig S. Carlson, Vered Aharonson, and Michiel Postema was published in the 8th volume of Current Directions in Biomedical Engineering in 2022.
Recent in-vivo work showed the suitability of Pickering-stabilized antibubbles in harmonic imaging and ultrasound-guided drug delivery. To date, however, theoretical considerations of antibubble core properties and their effects on antibubble dynamics have been rather sparse. The purpose of this study was to investigate the influence of skeletal friction on the damping of a pulsating antibubble and the pulsation phase of an antibubble relative to the incident sound wave.
This study was a collaborative work of Tampere University, the University of the Witwatersrand, Johannesburg, the University of Central Lancashire — Cyprus, and Afeka Tel Aviv Academic College of Engineering.

Dimensionless damping coefficent and its contributing components as a function of antibubble resting radius.

On the rigidity of four hundred Pickering-stabilised microbubbles by Nicole Anderton, Craig S. Carlson, Ryunosuke Matsumoto, Ri-ichiro Shimizu, Albert T. Poortinga, Nobuki Kudo, and Michiel Postema was published in the 61st volume of the Japanese Journal of Applied Physics in 2022.
This study explores the rigidity of Pickering-stabilised microbubbles subjected to low-amplitude ultrasound. Such microbubbles might be suitable ultrasound contrast agents.
This study was a collaborative work of Tampere University, the University of the Witwatersrand, Johannesburg, Hokkaido University, and Eindhoven University of Technology.

Maximum microbubble expansion measured as a function of initial radius.
Maximum microbubble expansion measured as a function of initial radius.

Rapid tablet swelling and disintegration during exposure to brightness-mode ultrasound by Craig S. Carlson, Nicole Anderton, Antje Pohl, Andrew J. Smith, Nobuki Kudo, and Michiel Postema was published in the 61st volume of the Japanese Journal of Applied Physics in 2022.
Controlled tablet disintegration is useful for chemical consistency checks. This study monitored the swelling of 54 analgesia tablets from two different batches, during 13–6-MHz brightness-mode sonication and simultaneous video recording. Diagnostic ultrasound significantly decreased tablet disintegration times, supporting the ultrasound–microbubble interaction hypothesis.
This study was a collaborative work of the University of the Witwatersrand, Johannesburg, Tampere University, Ruhr-University Bochum, the University of Hull, and Hokkaido University.

Tablet swelling experimental setup.
Tablet swelling experimental setup.

A brief note on experimental setups for in-vitro optical observations of HeLa cells and phospholipid-shelled microbubbles subjected to ultrasound by Michiel Postema was published in Physics in Medicine in 2022.
The purpose of this paper is to briefly underscore previous works with similar setups, highlighting the many agreements between early and recent work.

List of publications

2021

The full list of publications can be found on HAL.
A pre-2018 repository has been created at IPPT-PAN.