Conductive and Thermoresponsive Poly( N -isopropylacrylamide)-Based Hydrogels with Improved Deformation Characteristics for Self-Sensing Soft Actuators

Abstract

An intelligent multi-stimulus-responsive bilayer hydrogel actuator with self-sensing performance is desirable for advanced soft robotics, but integrating fast actuation, tunable bidirectional deformation, and real-time sensing remains challenging. Herein, an asymmetric bilayer hydrogel actuator is fabricated by a simple freezing strategy combined with interfacial infiltration, consisting of a sponge-like conductive PNIPAM/PVA/PANI active layer and a PAA/CMC passive layer. The ice-induced porous network greatly accelerates deformation and recovery under thermal-pH stimuli, delivering a bending rate of ∼7.1°/s and stable bidirectional motion, superior to the 5.4°/s unidirectional actuation of the nonporous counterpart. Polyaniline enables efficient photothermal heating above the LCST and 75% volume shrinkage under NIR light, supporting programmable underwater biomimetic movements such as tropistic bending and maze navigation. Interconnected pores also enable fast strain sensing with low hysteresis, converting mechanical deformation into real-time electrical signals. This hydrogel combines rapid reversible actuation and low-latency self-sensing for autonomous underwater soft robots.