Conductive photo-thermal responsive bifunctional hydrogel system with self-actuating and self-monitoring abilities

Despite enormous efforts in actuators, most researches are only limited to various actuation behaviors and demonstrations of soft materials. It has not yet been reported to capture and monitor its movement status in an invisible environment. Therefore, it is of great significance to develop a self-sensing and self-actuating dual-function hydrogel actuator system to realize real-time monitoring. Here, we report a bifunctional hydrogel system with self-actuating and self-monitoring abilities, which combines the functions of photothermal actuation and electrical resistance sensing into a single material. The bilayer tough conductive hydrogel synthesized by unconventional complementary concentration recombination and cryogenic freezing technique presents a dense conductive network and high-porosity structure, achieving high toughness at 190.3 kPa of tensile strength, high stretchability (164.3% strain), and the toughness dramatically (1,471.4 kJ·m−3). The working mechanism of the monitoring and self-sensing system is accomplished through the integrated monitoring device of surface temperature-bending angle-electron current, to solve the problem of not apperceiving actuator motion state when encountering obstacles in an invisible environment. We demonstrated for the first time a photothermal actuator's motion of a football player and goalkeeper to finish the penalty and a soft actuator hand, which can achieve the action of sticking to grab and release under photo-thermal actuation. When connected to the control closed circuit, the actuator realized closed-loop monitoring and sensing feedback. The development of bifunctional hydrogel systems may bring new opportunities and ideas in the fields of material science, circuit technology, sensors, and mechanical engineering.