Photomorphogenesis of Diverse Autonomous Traveling Waves in a Monolithic Soft Artificial Muscle.

Abstract

Biological organisms (e.g., batoid fish, etc.) possess the remarkable ability to morph their soft, sheet-like tissues into wavy morphologies and self-oscillate to make traveling waves, enabling myriad functionalities in propulsion, locomotion, and transportation. In contrast, current manmade soft robotic systems cannot adaptively make wavy morphologies and concurrently achieve wave propagation because the controllable actuation of desired 3D morphologies in entirely soft materials is a formidable challenge due to their continuously deformable bodies that own a large number of actuable degrees of freedom. Here, we report a bioinspired robotic system that not only allows photomorphogenesis of on-demand 3D wavy morphologies but also enables autonomous wave propagation in a monolithic soft artificial muscle (MSAM). This system employs a conceptually different design strategy based on a combination of two principles derived from plant morphogenesis and the undulatory motion of ray fish. The former offers a shaping principle based on differential growth that enables morphing MSAM into target wavy configurations, while the latter inspires a driving principle that induces autonomous propagation of shaped waves by rhythmic motor patterns. This waving system can be used as adaptive "soft engines/motors" that enable directional locomotion, intelligent transportation of cargo, and autonomous propulsion. It even produces programmable, complex artificial peristaltic waves. Our design allows controllable formation of 3D wavy morphologies and autonomous wave behaviors in the soft robotic system that would be useful for broad applications in adaptive, self-regulated mechanical systems for advanced robotics, soft machines, and energy harvest.