Highly conductive and anisotropic MXene hydrogels for bioinspired multi-directional self-sensing soft actuators

Inspired by the multi-directional environmental perception and adaptive morphological responses observed in biological systems, researchers have developed self-sensing soft actuators. However, current systems are restricted to unidirectional sensing capabilities and limited programmability, which hinders the realization of high-precision self-sensing and complex shape morphing. Herein, we develop a multi-directional self-sensing actuator with stretchability and conductivity that effectively addresses these limitations. Multi-directional self-sensing hydrogel actuator with elaborately aligned structure is successfully synthesized by aligning surface-functionalized MXene nanomonomers (m-MXene) under an alternating current (AC) electric field and in situ copolymerized with a thermoresponsive poly(N-isopropylacrylamide) hydrogel. The programmable shape-morphing hydrogel actuators with rapid response, light-actuation remote control, and self-sensing capability are fabricated by engineering the distribution of AC fields through the patterns and relative positions of the electrodes. Meanwhile, electrode-guided directional enrichment of m-MXene achieved anisotropic conductivity, forming the foundation for constructing logic gates. The hydrogel actuator exhibits strain-sensing performance, enabled by the engineered cross-aligned architecture of m-MXene that allows multi-directional strain detection. As a proof-of-concept, a photoresponsive hand-shape self-sensing actuator integrated with manipulator systems demonstrated intelligent closed-loop control of end-effectors through photoelectric-mechanical feedback. This work is expected to provide new insights for the development of next-generation soft robotics and artificial intelligence devices.