A method to characterize the cavitation pressure of soft matter under superimposed azimuthal shear

One failure mode experienced by biological materials is cavitation. Synthetic gels can serve as biological tissue analogs for studying this phenomenon. Currently, gel cavitation is typically investigated in initially stress-free materials via cavitation rheology. The lack of cavitation experiments on pre-stressed gel samples, however, prevents generalized-cavitation theory development/validation. This study introduces a needle-based, superimposed-shear-cavitation (SSC) apparatus to examine the role of shear stress in cavity nucleation, expansion, and collapse in soft matter. The sample-containing beaker in the needle-induced cavitation (NIC) approach is replaced with a Taylor-Couette cell to subject samples to torsion before needle insertion. To demonstrate, SSC was used to probe cavitation in tri-block copolymer (PMMA-PnBA-PMMA) gel samples. Critical cavitation pressure and the time until it was reached increased and decreased, respectively, with added sample torsion. SSC and NIC data agreed for no sample torsion. SSC results were found to be valuable for generalized cavitation model validation.