Leaf Vein-Inspired Programmable Superstructure Liquid Metal Photothermal Actuator for Soft Robots

Asymmetric-expansion photothermal actuators have attracted the attention of researchers owing to their simple structure, superior stability, rapid response, and precise controllability. However, their response speed, deformation capacity, and load-carrying capacity are mutually constrained by their thickness. Inspired by the veins and pulp in plant leaves, this study uses laser etching to apply a superstructure of ordered grooves to liquid metal (LM) photothermal actuators. The resulting LM@low-expansion polyimide (4.52 ppm K^-1)/polydimethylsiloxane (LM@PI/PDMS) programmable photothermal actuators demonstrate exceptional performance, including a load-carrying capacity of 190 times their weight, a rapid oscillation frequency of 19 Hz, a response speed of 60.96 ± 3.08°/ s, and a bending angle of 159.05 ± 2.52°. Hence, the proposed design resolves the inherent conflict between the load-carrying capacity and response speed. Furthermore, incorporating LM microspheres into actuators increases their stability and allows them to endure more than 20 800 cycles without damage. The actuators are used to create versatile smart devices and robots, such as photothermally actuated robotic dogs that can function across various terrains. This study provides a novel strategy for the design and fabrication of programmable photothermal actuators and highlights their potential for applications in advanced robotics, which paves the way for their integration into complex environments.