Liquid metals as soft electromechanical actuators

Leveraging the unique properties of liquids, such as surface tension, capillary action, reconfigurability, nearly unlimited stretchability, and viscosity has enabled the development of a wide range of soft actuators, presenting vast potential to revolutionise wearable healthcare devices, manufacturing, reconfigurable electronics, and robotics. Gallium (Ga) based liquid metals (GaLMs) are a remarkable family of functional fluidic materials that can actuate electrically for realising electromechanical functions. Such actuators are simple, highly responsive, highly controllable, and reversible, which has led to the creation of useful devices such as reconfigurable antennas, artificial muscles, electrical switches, and soft robots, just to name a few. Herein, this review succinctly and critically summarises recent advances in research on using GaLMs as electromechanical actuators. First, the properties of GaLMs are introduced, and then the methods for their electrical actuation and the applications thereof are discussed. Finally, an outlook is offered, highlighting the research challenges faced by liquid metal electromechanical actuators in order to develop into commercial devices.