Nonlinear bifurcation dynamics of laser-induced encapsulated microbubbles under acoustic cavitation: Influence of thermal and viscoelastic parameters

This study investigates the nonlinear dynamics of laser-induced encapsulated microbubbles under acoustic cavitation, focusing on the bifurcation behavior of the bubble expansion ratio. A high-precision laser radiation technique is employed to heat the surrounding fluid locally to a critical temperature, triggering controlled bubble nucleation and subsequent oscillatory dynamics. By analyzing the bifurcation diagrams of the radial expansion ratio against key control parameters, such as laser intensity, fluid viscosity, and encapsulation properties, we characterize the transition between stable oscillations, period-doubling bifurcation, and chaotic regimes. The results reveal how viscoelastic encapsulation influences damping mechanisms and stability thresholds, offering insights into optimizing microbubble performance in biomedical and industrial applications, including ultrasound contrast imaging and targeted drug delivery. In particular, increased shell viscosity and acoustic frequency were found to suppress chaotic oscillations, while elevated temperature and low-frequency driving promote bifurcation and instability. These findings provide practical design guidelines for tuning acoustic and thermal parameters to ensure controlled cavitation and enhance the efficacy and safety of microbubble-assisted therapies.