image: Time evolution of the bubble shape for shell thicknesses of 1 nm and 10 nm under the same ultrasound conditions. A thin shell allows large deformations and can lead to the formation of a jet toward the wall, whereas a thick shell effectively suppresses bubble deformation.
Credit: Haruki Furukawa from Nagoya Institute of Technology, Japan
Encapsulated microbubbles (EMBs), tiny gas-filled bubbles coated in lipid or protein shells, play a central role in biomedical ultrasound. When exposed to ultrasound waves, EMBs contract, resulting in oscillations that enhance image contrast or deliver drugs directly by creating pores in cell membranes via sonoporation. However, while promising for biomedical applications, their behavior is far more complex.
Most existing theories on EMBs assume spherically symmetrical oscillations and only study them in simple Newtonian fluids. However, most biological fluids, such as blood, are viscoelastic (non-Newtonian) fluids. When inside the body, these fluid forces, pressure from vessel walls, and changing ultrasound pulses can influence the behavior of EMBs, affecting both imaging accuracy and treatment safety.
To better understand these effects, Assistant Professor Haruki Furukawa and Professor Shuichi Iwata from Nagoya Institute of Technology (NITech), Japan, in collaboration with Emeritus Professor Tim N. Phillips, Dr. Michael J. Walters, and Reader Steven J. Lind from Cardiff University, Wales, developed a comprehensive computational model that simulates the behavior of EMBs under real biological conditions. Their study was made available online on November 10, 2025, and will be published in Volume 347 of the Journal of Non-Newtonian Fluid Mechanics on January 01, 2026.
“Most microbubble models assume perfect spheres and Newtonian liquids,” explains Dr. Furukawa. “However, real biological fluids are viscoelastic, so we aimed to develop a model that simulates actual physiological conditions for a more realistic assessment of safety and efficacy.”
Accordingly, the researchers incorporated a non-singular boundary element method that focuses on calculations of the object’s boundaries, combined with the Oldroyd B model that describes rheological behavior in viscoelastic fluids. Using this approach, they simulated a fully non-spherical, time-dependent behavior of a coated microbubble when exposed to pulsed ultrasound near a rigid wall. The coupled approach allowed them to capture key features such as asymmetric deformation, translational motion, and liquid-jet formation, which are usually missed in simple spherical models.
They found that the EMB shell thickness strongly affects bubble stability. Thick shells experienced limited deformation, lowered jet velocity, and produced smaller pressure peaks at the vessel wall. In contrast, thin shells underwent stronger motion and jetting, potentially increasing the risk of tissue damage. The results also revealed how fluid viscoelasticity competes with inertia and shell elasticity and clarified how ultrasound frequency and pressure interact with microbubble design.
“Our framework offers a cost-effective tool to assess microbubble safety,” highlights Dr. Furukawa. “By understanding how shell properties, fluid viscoelasticity, and ultrasound settings influence EMBs, we can better guide design standards for safer diagnostics and more effective targeted treatments.”
About Nagoya Institute of Technology, Japan
Nagoya Institute of Technology (NITech) is a respected engineering institute located in Nagoya, Japan. Established in 1949, the university aims to create a better society by providing global education and conducting cutting-edge research in various fields of science and technology. To this end, NITech provides a nurturing environment for students, teachers, and academicians to help them convert scientific skills into practical applications. Having recently established new departments and the “Creative Engineering Program,” a 6-year integrated undergraduate and graduate course, NITech strives to continually grow as a university. With a mission to “conduct education and research with pride and sincerity, in order to contribute to society,” NITech actively undertakes a wide range of research from basic to applied science.
Website: https://www.nitech.ac.jp/eng/index.html
About Assistant Professor Haruki Furukawa from Nagoya Institute of Technology, Japan
Haruki Furukawa is an Assistant Professor in the Department of Life Science and Applied Chemistry at the Nagoya Institute of Technology (NITech), Japan. He holds a Doctor of Engineering degree from Yokohama National University (2016) and earned his Master’s (2013) and Bachelor’s (2011) degrees from NITech. Over the past decade, he has published more than 78 research papers, focusing on computational fluid dynamics, fluid mixing, impeller design, and flows in viscous and viscoelastic fluids. His contributions have earned him several honors, including the 2024 “Best Reviewer Award” from The Society of Chemical Engineers, Japan.
Journal
Journal of Non-Newtonian Fluid Mechanics
Method of Research
Computational simulation/modeling
Subject of Research
Not applicable
Article Title
The influence of viscoelasticity on the dynamics of encapsulated microbubbles near a rigid surface forced by ultrasound
Article Publication Date
10-Nov-2025
COI Statement
Shuichi Iwata, a member of the Editorial Board of TNP, reports that financial support was provided by the Japanese Society for the Promotion of Science. Other authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.