Photothermal-Responsive Lightweight Hydrogel Actuator Loaded with Polydopamine-Modified Hollow Glass Microspheres.

Aquatic actuators based on the light-to-work conversion are of paramount significance for the development of cutting-edge fields including robots, micromachines, and intelligent systems. Herein, we report the design and synthesis of near-infrared light-driven hydrogel actuators through loading with lightweight polydopamine-modified hollow glass microspheres (PDA-HGMPs) into responsive poly( N -isopropylacrylamide) (PNIPAM) hydrogels. These PDA-HGMPs can not only function as an excellent photothermal agent but also accelerate the swelling/desewlling of hydrogels due to their reconstruction for polymer gel skeleton, which speeds up the response rate of hydrogel actuators. The resulting hydrogel actuator shows controlled movements under light illumination, including complex self-propellant and floating/sinking motions. As the proof-of-concept demonstrations, a self-sensing robot is conceptualized by integrating the PDA-HGMP-containing hydrogel actuator with an ultrathin and miniature pressure sensor. Hopefully, this work can offer some important insights into the research of smart aquatic soft actuators, paving the way to the potential applications in emerging fields including micromachines and intelligent systems.