Needle- and Laser-Induced Cavitation Techniques to Study Extreme Deformation and Strain-Sensitivity of Intact Brain Tissue*

Despite growing support that cavitation damage contributes to traumatic brain injury (TBI), current diagnostic testing is incapable of detecting cavitation-related tissue damage. One limitation is that the mechanism of damage, be it formation/expansion of a cavitation bubble, collapse of that bubble, or strain propagation through heterogeneous material, is unknown. Cavitation rheology is a powerful technique to characterize and understand the mechanical properties of soft materials, such as biological tissues. This method introduces a defect within a material at the tip of a needle, initiating an unstable void expansion followed by collapse. This technique can be used to quantify the deformation of brain tissue in low strain regimes. A complementary method, laser-induced cavitation (LIC), applies high strain deformations with a focused laser light to vaporize a particle resulting in rapid expansion of a void at extremely short timescales. I will present data on brain deformation at low and high strain rates using these methods as well as how boundary conditions impact deformation at an interface. This data is pertinent to understanding the interface dynamics and strain sensitivity of brain tissue during cavitation and how that damage manifests in TBI patients.