All-silicone prestrain-locked interpenetrating polymer network elastomers: free-standing silicone artificial muscles with improved performance and robustness

We present a novel all-silicone prestrain-locked interpenetrating polymer network (all-S-IPN) elastomer for use as a muscle-like actuator. The elastomer is fabricated using a combination of two silicones: a soft room temperature vulcanizing (RTV) silicone that serves as the host elastomer matrix, and a more rigid high temperature vulcanizing (HTV) silicone that acts to preserve the prestrain in the host network. In our novel S-IPN fabrication procedure we co-dissolve the RTV and HTV silicones in a common solvent, cast thin films, and allow the RTV silicone to cure before applying prestrain and finally curing the HTV silicone to lock in the prestrain. The free-standing prestrain-locked silicones show a performance improvement over standard free-standing silicone films, with a linear strain of 25% and an area strain of 45% when tested in a diaphragm configuration. We show that the process can also be used to improve electrode adhesion and stability as well as improve the interlayer adhesion in multilayer actuators. We demonstrate that, when coupled with carbon nanotube electrodes, fault-tolerance through self-clearing can be observed. We use the fault-tolerance and improved interlayer adhesion to demonstrate stable long-life (>30 000 cycles at >20% strain) actuation and repeated high-performance actuation (>500 cycles at similar to 40% strain) of prestrained free-standing multilayer actuators driving a load.