Tunable mechanical behavior of synthetic organogels as biofidelic tissue simulants

Solvent-swollen polymer gels can be utilized as mechanical simulants of biological tissues to evaluate protective systems and assess injury mechanisms. However, a key challenge in this application of synthetic materials is mimicking the rate-dependent mechanical response of complex biological tissues. Here, we characterize the mechanical behavior of tissue simulant gel candidates comprising a chemically crosslinked polydimethylsiloxane (PDMS) network loaded with a non-reactive PDMS solvent, and compare this response with that of tissue from murine heart and liver under comparable loading conditions. We first survey the rheological properties of a library of tissue simulant candidates to investigate the effects of solvent loading percentage, reactive functional group stoichiometry, and solvent molecular weight. We then quantify the impact resistance, energy dissipation capacities, and energy dissipation rates via impact indentation for the tissue simulant candidates, as well as for the murine heart and liver. We demonstrate that by tuning these variables the silicone gels can be engineered to match the impact response of biological tissues. These experiments inform the design principles required for synthetic polymer gels that are optimized to predict the response of specific biological tissues to impact loading, providing insight for further tuning of this gel system to match the impact response of other "soft tissues".