Cellulose‐Reinforced Bilayer Hydrogel Actuator With Solvent‐Responsiveness

Functional hydrogels, with their stimulus‐responsive three‐dimensional networks, have emerged as promising candidates for flexible actuators. However, integrating reversible solvent response with robust mechanical strength remains limited and requires further investigation. In this study, we develop a series of mechanically strong, solvent‐responsive bilayer actuators by fabricating polyacrylamide (PAM) hydrogels with different cellulose nanocrystal (CNC) concentrations via in situ layer‐by‐layer polymerization. A higher CNC concentration in the hydrogel network reduces average pore size, increases crosslinking density, and enhances tensile strength. The difference in CNC content between the two layers creates an anisotropic network, enabling controllable and reversible bending actuation upon solvent exchange. A maximum bending angle of 450° is achieved for the C 6 A/C 0.5 A bilayer hydrogel, without delamination after 10 swelling–deswelling cycles between water and ethanol. Leveraging this stable and strong actuation, a cross‐shaped hydrogel gripper is demonstrated, capable of grasping and transporting objects up to 2400 times its own weight, outperforming most existing soft grippers. This application can be extended to most polar solvents, validating the practical potential of the bilayer hydrogels as solvent–responsive actuators and highlighting their promising applications in intelligent grippers and soft robotics.