Inertial interface cavitation creates complex, flow-like structures within a soft solid

Inertial interface cavitation is a well-appreciated phenomenon in many natural, biological, and physical processes. The existence of impedance changes across an interface can generate complex fluid motion within a fluid but whether such motion persists, or is similar, within the adjacent solid has yet to be determined. Here, by leveraging recent technological advances in quantitative full-field imaging, deformation/motion characterization, and laser-based cavitation, we document the complex deformation fields that arise in a model soft solid of gelatin during interfacial cavitation. Specifically, we identify stagnation points, vortex pairs, and vortex ring-like structures as a function of the cavitation bubble standoff distance within the solid, for which we identify four distinct regimes. While two of the regimes have been previously studied, we show that the additional two regimes close to the interface generate most of the complex, fluid-like deformations within the gel. Finally, we quantify the associated material stresses and residual, permanent strains that can occur during such events providing both length and time scale estimates of the destructive power of cavitation. Significance StatementThe study of interfacial cavitation dynamics has historically focused on resolving cavitation bubble morphology and surface deformations due to an inability to measure subsurface behavior. However, understanding the intricate dynamics of cavitation at these interfaces and below holds significant implications for engineering, medical, and life science applications. Leveraging recent technological advances, we provide the first, full-field sub-surface measurements during interfacial cavitation revealing complex, flow-like structures such as dynamically-evolving stagnation points and vortex pairs. Our results also provide insight into the unusual stresses and strains generated by the violent collapse of interfacial cavitation bubbles within the soft solid. These measurements provide an important first step in understanding how certain species in nature harness this power whereas others aim to mitigate it.