Rapidly responsive liquid metal/polyimide photothermal actuators designed based on the bilayer structure difference in coefficient of thermal expansion

Abstract

Photothermal actuators have received more and more attention due to their high efficiency, easy fabrication, and various implementation methods. In this work, we prepared a photothermal actuator via structural design using liquid metal (LM) particles and polyimide. Due to the flexibility of liquid metals, which is different from those of other rigid fillers, the photothermal actuator responds rapidly with a bending speed of 21.89° s⁻¹, which exceeds those of most of the reported photothermal actuators. In addition, this work explored the photoactuation mechanism of the liquid metal/polyimide photothermal actuator and found that the difference in the thermal expansion coefficient was the main reason for the liquid metal content to be low. What's more, the photothermal actuator can mimic the creeping of caterpillars, the swimming of fish, and the lifting and falling of arms under a NIR laser. Besides, the photoactuators can be used as light-controlled switches to realize the remote and precise control of the circuit. Therefore, photoactuators are expected to be used in the fields of bionic systems and flexible robots, which enriches the research content of photoactuators and expands the application field of liquid metals.