Cavitation is a common phenomenon encountered in many biological and medical applications including cataract laser surgery, lithotripsy and histotripsy. One of the biggest challenges in these settings is to minimize collateral tissue damage induced by the procedure, which requires a thorough understanding of how cavitation bubbles interact with their surroundings. To pave the foundation for a better understanding of inertial cavitation induced damage on the surrounding soft medium, we employ a spatially-focused pulsed laser to generate inertial cavitation bubbles inside a soft material of interest. The surrounding soft medium typically undergoes large deformations up to 1,000% strains at ultra-high strain-rates (10^3 s^-1~10^7 s^-1). Previously, we had demonstrated that the spatiotemporal dynamics of the single oscillation bubble can be used to determine the non-linear, high strain-rate viscoelastic properties of the surrounding material. Here, by using improved spatial imaging, we report direct experimental observation of strain localization and surface instabilities near the bubble wall during the bubble expansion-collapse cycles, and how these strain localizations can lead to various types of surface instabilities within a gel-like soft material giving rise to wrinkle and crease patterns. These type of dynamic rugae patterns and associated strain concentrations might be of significant interest in medical and engineering applications to predict the spatial extent of tissue damage during cavitation. 

Dynamic Rugae Strain Localizations and Instabilities in Soft Viscoelastic Materials During Violent Inertial Microcavitation

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