High-Speed, Full-Field Deformation Measurements Near Inertial Microcavitation Bubbles Inside Viscoelastic Hydrogels

Background Inertial microcavitation is a well-known phenomenon that generates large stresses and deformations at extremely high loading rates in various soft materials, ranging from commercial polymer coatings to biological tissues. Recent advances in soft material characterization have taken advantage of inertial cavitation as a means towards a high-rate, minimally invasive soft material rheology approach. Yet, most of these studies rely on idealizations to infer the full deformation fields around the bubble based only on the experimentally measured temporal evolution of the bubble radius (akin to relying on crosshead strain data in a traditional materials test). Objective Here, we develop an experimental method to quantitatively measure full-field deformation and associated strains due to laser-induced inertial cavitation (LIC) in gelatin hydrogels, where the surrounding material is subjected to ultra-high strain rates ( 10 3 ∼ 10 6 s - 1 ). Methods Our method combines two broad experimental techniques: the embedded speckle plane patterning (ESP) method and spatiotemporally adaptive quadtree mesh digital image correlation (STAQ-DIC). Results We illustrate the powerful capability of our approach by testing three concentrations of gelatin hydrogels 6%, 10%, and 14% as benchmark cases and quantitatively capture their kinematics during LIC. Conclusions These full-field, quantitative investigations are of significant interest in many cavitation-related applications including high strain-rate material characterization, guided advanced laser & ultrasound therapies, tissue engineering, and advanced manufacturing.