Determination of high strain-rate, viscoelastic material properties of soft gels and tissues using inertial microcavitation in a thin layer

Determination of high strain-rate properties of soft gels and biological tissues is crucial for various biological and engineering applications but remains challenging. Inertial microcavitation rheometry (IMR) is a novel technique that addresses this need, relying on optical resolution of cavitation bubble kinematics via high-speed videography. Established for optically transparent samples, IMR faces challenges in light-scattering media like opaque tissues. One solution is to prepare thinner samples, facilitating the measurement of bubble dynamics. However, confinement between rigid, transparent boundaries violates the assumed infinite domain of the IMR theoretical framework used to determine material properties. To overcome this, we developed a modified, thin-layer IMR approach, utilizing axisymmetric finite-element simulations of bubble dynamics in thin layers for accurate high strain-rate viscoelastic property determination. The method is applied to 6% and 14% gelatin gels and validated against experimental data for isolated bubbles. We then estimate viscoelastic properties of fresh porcine brain tissue in different anatomical regions, such as cortex and thalamus.