Pre-Twist-dependent Configurations of Hydrogel Rings and Their Distinct Modes of Self-sustained Locomotion
摘要
Self-sustained continuous motion is a central functional objective in soft actuators and robotics. One key challenge lies in establishing a persistent, self-regulated deformation feedback in soft materials under external stimulation, which is ultimately rooted in their geometry and configuration. Here, based on a cylindrical hydrogel with fast, reversible, and anisotropic photoresponsiveness, we construct a series of hydrogel rings by twisting one end of the gel string and closing it into a loop. By regulating the built-in twist (Tw) and the resulting internal prestress, the rings adopt distinct configurations that give rise to multiple motion modes under light irradiation. Gel rings with relatively small Tw remain in quasi-flat configurations and display coupled rolling and spinning motions. As Tw increases, the rings undergo Michell’s instability and rapidly snap into a figure-of-eight configuration upon light irradiation, subsequently exhibiting irregular tumbling motions. At even larger Tw, the rings adopt “dough twist” configurations, showing persistent rolling under constant irradiation. Distinct motion modes arise from different actuation-deformation feedback loops established in hydrogels with distinct configurations and stress distributions. These results demonstrate not only the role of the configuration in governing locomotion, but also the potential of a single hydrogel system to achieve diverse motion behaviors through programming internal stresses.