Self‐Oscillating Helix Showing Amplified Winding and Unwinding Motions

Abstract

ABSTRACT Helical architectures in nature amplify motion via winding–unwinding. We report a simple, universal photopolymerization strategy to fabricate hydrogel helices with precisely controlled radial polymer gradients inside glass capillaries. A helically wrapped photomask and a chemical UV absorber (Ru(bpy) 3 ) jointly encode longitudinal and radial asymmetry. Their geometry is readily programmed by adjusting the photomask width and spacing, and our approach is polymer‐general, including thermoresponsive gels and organogels. As a representative example, lower critical solution temperature (LCST)‐type poly(NIPAAm) helices convert small, isotropic volume change into amplified uniaxial deformation, showing 1.6‐fold larger axial shrinkage than their total length shrinkage under heating. They respond to various stimuli, including temperature, acid, and near‐infrared (NIR) light. As a proof‐of‐concept soft robotic actuator, we fabricated a helix with a gradual axial variation in diameter and demonstrated stepwise, unidirectional locomotion along a string under cyclic heating and cooling. Integrating vinyl‑functionalized Ru(bpy) 3 as a covalent catalyst yields self‑oscillating helices driven by the Belousov–Zhabotinsky reaction, which autonomously repeat winding–unwinding accompanied by peristaltic waves. Compared with conventional rods, helices exhibit four‐fold larger amplitude and 3.4‐times faster deswelling kinetics. Our platform establishes a geometry‑driven design rule that harnesses helical coupling to amplify displacement in programmable and autonomous soft actuators.