LCST-phase-separated porous liquid metal-filled hydrogel actuators with fast electro-response, enhanced strength, and low electric field.

Abstract

Electro-responsive hydrogel actuators (ERHAs) are promising candidates for soft robotics due to their capability for exhibiting large, reversible deformations. However, their application potential is constrained by the requirement for high driving electric field strength (E), insufficient mechanical robustness, and slow actuation response. Here, to simultaneously address these limitations, we design an ionic hydrogel with integrated liquid metal (LM) and thermoresponsive LCST behavior. The porous architecture is readily constructed by the LCST-induced phase separation process. LM inclusion not only enables sensitivity to low E but also reinforces mechanical properties of the otherwise weakened porous hydrogel. The resulting actuator achieves a large bending angle of 88.1° within 32 seconds under a low electric field of 0.25 V mm^-1. This represents the fastest electro-response reported to date among ERHAs operating below 1 V mm^-1, a threshold widely recognized as safe for human exposure. Furthermore, we demonstrate its versatility in executing diverse underwater tasks, including object manipulation, encapsulation, and directional locomotion. This facile yet effective strategy for constructing mechanically robust, fast-response hydrogel composites offers new avenues for the development of next-generation soft robotic systems.