Probing local nonlinear viscoelastic properties in soft materials

Minimally invasive experimental methods that can measure local rate dependent mechanical properties are essential in understanding the behaviour of soft and biological materials a wide range applications. Needle based measurement techniques such as Cavitation Rheology Volume Controlled Cavity Expansion (VCCE), allow for minimally testing, but have been limited to measuring elastic material properties. Here, we propose several enhancements VCCE technique adapt it characterization viscoelastic response at low medium stretch rates ($10^{-2}$ - $1$ s${}^{-1}$). The proposed performs cycles expansion-relaxation controlled cavity expansion setting then employs large deformation model capture measured response. Application PDMS rubber reveals significant with high precision repeatability, while isolating equilibrated states used directly infer quasistatic modulus. is further established by demonstrating its ability changes tuneable system. explain earlier reports insensitive needle methods: demonstrated conventional use constant volumetric induce lead stiffening an illusion We thus conclude cautionary note on possible overestimation modulus previous studies suggest protocol, this work, accurate estimation both dynamic parameters.