Characterizing the elastic shear modulus of a soft medium via a thermally induced elastic shear wave in thermodynamic equilibrium

A novel method to characterize the elastic shear modulus of an isotropic, homogeneous and extremely soft material based on a thermally induced elastic shear wave (TIESW) under thermodynamic equilibrium at room temperature is proposed. The temporal evolution of the TIESW on the surface of a squared polyvinyl acetate (PVA) specimen is observed, while the oscillation frequency of the TIESW is measured by using a two-frequency polarized heterodyne interferometer. In experiments, the oscillation frequency of the TIESW in PVA specimens is in the range of 10^-3 Hz, which is equivalent to μ Pa on the elastic shear modulus. The features and advantages of the TIESW-based method in comparison to conventional methods are discussed.