Soft actuators using liquid crystal elastomers with encapsulated liquid metal joule heaters

Abstract

We present a soft actuator composed of fluidic channels of liquid metal alloy embedded in a liquid crystal elastomer (LCE). The LM channels function as stretchable Joule heating elements that deliver heat to the LCE to induce a shape memory phase transition. Because the heater is fluidic, it can deform with the surrounding LCE as the actuator extends and contracts during actuation. In addition to contractile actuation, the LCE can be programmed to perform in-plane or out-of-plane flexural actuation, which exhibit deformations predictable using a simple finite element analysis model. By combining a liquid metal heater with a shape memory polymer, we achieve a soft actuator that does not require an external heat source and can instead be directly activated with electrical current. Finally, we show that the liquid metal channels can also function as a sensor during the actuation cycle, allowing for closed-loop control of the soft actuator.