Self-Propelled Morphing Matter for Small-Scale Swimming Soft Robots

Aquatic insects have developed versatile locomotion mechanisms that have served as a source of inspiration for decades in the development of small-scale swimming robots. However, despite recent advances in the field, efficient, untethered, and integrated powering, actuation, and control of small-scale robots remains a challenge due to the out-of-equilibrium and dissipative nature of the driving physical and chemical phenomena. Here, we propose the design of small-scale bioinspired aquatic locomotors with programmable deterministic trajectories that integrate self-propelled chemical motors and photoresponsive shape-morphing structures. We have developed a Marangoni motor system based on structural protein networks that self-regulate the release of chemical fuel and integrated it with photochemical liquid crystal network (LCN) actuators that change their shape and deform in and out of the surface of water. While the diffusion of fuels from the motor system regulates the Marangoni propulsion, the dissipative photochemical deformation of LCNs provides locomotors with control over the directionality of motion at the air-water interface. This approach gives access to five different but interchangeable modes of locomotion within a single swimming robot via morphing of the soft structure. The proposed design, which mimics the mechanisms of surface gliding and posture change of semiaquatic insects such as water treaders, offers solutions for autonomous swimming soft robots via untethered and orthogonal power and control.