A generalizable geometry-driven approach for programmable locomotion in stimuli-responsive materials

Stimuli-responsive hydrogels offer considerable potential for soft robotics; however, achieving controllable locomotion remains challenging, as it requires the integration of shape transformation and effective environmental interaction. Conventional strategies often rely on heterogeneous materials, such as multimaterials or gradient structures, to induce motion, but these approaches substantially complicate fabrication and compromise material reliability. Here, we demonstrate that stimuli-responsive hydrogels can achieve programmable locomotion solely through geometric design, enabled by single-vat photopolymerization-based three-dimensional (3D) printing. By geometrically designing the hydrogel to generate asymmetric stress and relaxation under repeated stimuli, the system moves along programmable trajectories, such as forward, lateral, and diagonal motion. Experiments with pH- and temperature-responsive hydrogels validate tunable locomotion direction in one- and two-dimensional trajectories, and speed, while finite element analysis (FEA) simulations provide mechanistic insight and predictive guidance for design. • Geometry-driven design enables hydrogel locomotion with uniform material properties. • Programmable locomotion is achieved with tunable directions and speeds. • FEA simulations elucidate and guide the geometry-driven design of hydrogel motion.