Anisotropic Hydrogels with Aligned Porous Structures for Light-steerable Autonomous Rolling

Hydrogel actuators with intrinsic softness, biocompatibility and large deformability hold great promise for extensive applications in intelligent autonomous soft robotics. However, achieving directionally controllable autonomous motion under constant stimulation remains a key challenge, primarily due to the isotropic and densely crosslinked nature of conventional hydrogel networks, which limits both directional driving forces and efficient mass transport pathways. Here, we report a simple method for the fabrication of curved cylindrical hydrogels with aligned porous channels that enable autonomous rolling under constant light irradiation via directional freezing assembly-assisted in situ photopolymerization. Benefiting from the oriented open-cell network, the hydrogel exhibited fast light-responsive deformation with bending and recovery speeds of 16.5 (°)·s −1 and 24 (°)·s −1 , respectively. Notably, the hydrogel achieved self-sustained rolling under constant light irradiation at a speed of 0.77 mm·s −1 , arising from the synergy of structural anisotropy and geometric curvature. By spatially modulating the irradiation region, the photo-guided direction-steerable rolling could be realized. Additionally, the hydrogel implemented multiple tasks including obstacle crossing, stair climbing and cargo transport, highlighting its potential in biomimetic soft robotic systems.