City Research Online

Abstract

The present thesis introduces a novel numerical framework for the study of bubble-tissue interactions, crucial for understanding the mechanics behind tissue-induced damage in medical therapies where cavitation is apparent, such as shock-wave lithotripsy, high-intensity focused ultrasound, and needle-free injections. To tackle these scenarions, we have developed solver employs the 6-equation required by the Diffuse Interface Method (DIM), with its extension
for isotropic elastic solids, accounting for the interaction across fluid-solid-gas interfaces, able to accurately resolve bubble dynamics, shock wave propagation, large solid deformations and dynamic appearance of cavitation regions. For the resolution of the extended variety of length scales, due to the dynamic and fine interfacial structures, an Adaptive Mesh Refinement (AMR) framework for unstructured grids was incorporated. This multi-material multi-scale approach aims to reduce numerical diffusion and preserve sharp interfaces, providing a novel computational approach for accurately capturing the complex dynamics of bubble collapse near biological tissues and the ensuing interactions. Due to the inertial nature of the bubble collapse dynamics surface tension, mass transfer, phase change, visco-elastic, and strain-stiffening effects are neglected.

The primary findings of this work include the elucidation of a previously undocumented tension-driven tissue injury mechanism during shock-wave lithotripsy, offering insights into the secondary collapse phase of gas bubbles near soft tissues and their potential for tissue damage. The gas bubble collapse dynamics near soft tissues are discussed in detail, including the shock wave emissions, liquid jet formation, and secondary collapses. Additionally, a comprehensive parametric study elucidates the influence of various factors on bubble behavior and tissue interaction, offering valuable insights into the various parameters affecting the bubble dynamics, during shock wave lithotripsy. Finally, the investigation into needle-free jet injectors demonstrates the framework’s capability to simulate liquid-jet and skin interactions, highlighting its potential use to investigate the penetration depth and drag delivery for various skin types.

This work significantly advances the computational modeling of bubble dynamics in medical applications, providing a robust tool for the development and optimization of ultrasound-based therapies and devices.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TJ Mechanical engineering and machinery T Technology > TL Motor vehicles. Aeronautics. Astronautics
Departments:	School of Science & Technology > Engineering > Mechanical Engineering & Aeronautics School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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