Acoustic microbubble dynamics with viscous effectsNumerical modeling of the 3D dynamics of ultrasound contrast agent microbubbles using the boundary integral method

This paper presents a numerical model for studying the 3D dynamics of ultrasound contrast agent (UCA) microbubbles using the boundary integral method.

UCAs are encapsulated gas-filled bubbles a few micrometers in diameter that are increasingly used in therapeutic applications like drug delivery, gene therapy, and tissue ablation.

While previous research has largely focused on spherical oscillations of UCAs, this paper addresses the less-studied but clinically important nonspherical behavior. The authors develop a model that adapts Hoff’s approach for thin-shell, spherical contrast agents to nonspherical cases, maintaining high-quality mesh of the bubble surface through a hybrid approach of Lagrangian method and elastic mesh technique.

The model successfully validates against a modified Rayleigh-Plesset equation for encapsulated spherical bubbles and provides insights into UCA dynamics in both infinite fluids and near rigid boundaries. Key findings show that the encapsulating shell absorbs energy during deformation, making bubble dynamics less violent compared to uncoated bubbles. The coating reduces maximum volume and oscillation period while making jets sharper but decreasing jet velocity.

When UCAs are near a wall and subject to ultrasound, jet direction depends primarily on the dimensionless standoff distance, with jets directed toward the wall at close distances and rotating toward the acoustic wave direction as distance increases. The research also demonstrates that jet velocity, maximum volume, and centroid movement decrease with shell thickness, while increased shell viscosity primarily affects jet velocity rather than global bubble dynamics.

These findings have important implications for understanding how UCAs can be optimized for therapeutic applications, particularly where controlled bubble jetting may enhance drug delivery or tissue disruption.