Soft Untethered Robots and Grippers Based on Humidity-Gated Magnetic-Responsive Film Actuators

Soft untethered robots and grippers are emerging smart structures for multiple applications in remote or confined environments. However, developing high-performance actuators with the excellent integration of simple forms, complex locomotion, fast response, and robust actuation remains challenging. Herein, we demonstrate that the challenge can be addressed by the powerful nacre-like film actuators comprising graphene oxide, sodium alginate, and magnetic nanoparticles. The resultant film actuators showed excellent humidity/magnetic dual-responsive properties and water-assisted self-healing ability. Benefiting from these features, soft untethered humanoid robots were designed to rapidly implement complex fitness locomotion consisting of sit-ups, push-ups, sit-and-reach, and high leg kicks within 1 s. More importantly, the synergistic action of humidity/magnetic dual actuation enabled the untethered robots with directional locomotion such as horizontal movements, skipping obstacles, and uphill climbing. Furthermore, the humidity-gated magnetic actuation imparted the film actuators with faster vertical upward motions and higher responsive height than the single magnetic response. It is incredible to observe that the dual-responsive synergistic action endows the gripper-like actuator with the ability to vertically transport cargo 28 times its weight. Thus, this work may broaden the potential applications of the humidity/magnetic dual-responsive composite films in soft robots and actuators.