Effect of Surface Energy and Confinement on Cavitation in Soft Gels

The sudden expansion of a cavity in soft solids subjected to an internal pressure is a commonly observed phenomenon. Such phenomenon has been harnessed in developing cavitation rheology (CR) technique for probing the local mechanical properties of various soft materials. In this experiment, a small defect within a soft material is pressurized and the critical pressure corresponding to the sudden expansion of the defect is recorded. The critical pressure is dictated by the elasticity of the material, surface energy, and geometric factors. We have developed a finite element based framework to capture the critical pressure for a spherical cavity growth in an infinite media and for the CR geometry. Presence of a needle in the CR geometry increases the critical pressure, in comparison to the growth of spherical cavity in an infinite media. The effect of confinement on the critical pressure is captured by varying the distance between the needle tip and the sample boundaries. The simulation results are compared with that obtained experimentally for triblock gels consisting of poly(styrene)-poly(isoprene)-poly(styrene) in mineral oil.