Phase-Change Silicone Elastomers for Tough, Soft Actuators

Soft materials capable of controlled shape changes near ambient temperature are of interest for active devices that interact with living organisms. In this study, we achieve such functionalities by synthesizing responsive elastomers based on polydiethylsiloxane (PDES). Unlike conventional silicones, PDES elastomers are mesomorphic. Without any reinforcing additives, the mesophase improves the toughness of PDES to 8 times that of neat polydimethylsiloxane (PDMS) elastomers and 4 times that of Sylgard 184. Uniaxially stretched mesomorphic PDES elastomers undergo reversible shape changes under a bias load in response to temperature, generating 14% contractile strain on heating from 0 to 40 °C. The utility of PDES elastomers as actuators is enhanced by fabricating them into twisting actuators and describing strategies to minimize hysteresis during shape change cycles. The combination of toughness, actuation near ambient temperature, and environmental stability suggests that PDES could be attractive for biomedical devices where soft actuators interface with living organisms.