A Non-Volatile Surface Tension-Driven Electrochemical Liquid Metal Actuator

We present a surface-tension driven electrochemical liquid metal (LM) actuator without the gas-producing side-reaction and capable of fabrication/operation in ambient air for practical applications. A hybrid supercapacitor is introduced to inhibit the common counter electrode side reactions, and the use of quasi-solid-state ionic hydrogel instead of liquid electrolyte further enables non-volatile operations. A 2×4 LM droplet array is demonstrated to actuate by a low driving voltage of 3.5 V for a maximum force of ~8.5 mN and a displacement of 0.56 mm in only 1.75 s. With the favorable scaling law of surface tension, further miniaturization could provide new opportunities in applications such as micro-robots, microfluidics, soft robots, and so on.