Magnetic field assisted fabrication of asymmetric hydrogels for complex shape deformable actuators

Hydrogel actuators exhibit various motions such as contraction, expansion, bending, and rotation in response to external stimuli, and have potential applications in artificial muscles, photonic displays, and soft manipulators. However, the fabrication of hydrogel actuators with complex deformation through a facile pathway remains a challenge. Herein, we report that hydrogel actuators with an asymmetric structure can be rapidly fabricated by magnetic induction and subsequent in situ polymerization. The asymmetric hydrogel actuators could deform in acidic solutions and reversibly recover in alkaline solutions. Importantly, a programmable deformation of hydrogel actuators could be achieved by introducing complex patterns into hydrogel networks through prearranged magnets, so as to enable a desired application such as switching on/off an electric circuit. This work provided a facile, fast, and universal strategy to fabricate programmable hydrogel actuators with asymmetric structures.