Multistimulus-Responsive Graphene Oxide/Fe₃O₄/Starch Soft Actuators

Soft actuators that respond to external stimuli like moisture, magnetism, light, and temperature have received tremendous attention owing to their promising potential in many frontier applications, including smart switches, soft robots, sensors, and artificial muscles. However, most of the conventional actuators can only be triggered by a solo stimulus and demand advanced manufacturing techniques that utilize expensive, hazardous, and synthetic raw materials. Herein, we design and fabricate a multiple stimuli-responsive actuator using graphene oxide, Fe₃O₄ nanoparticles, and tapioca starch via a water evaporation-induced self-assembly method. The resultant hybrid actuator exhibits a bending speed of ∼72° s^-1 upon moisture exposure. Moreover, it can perform clockwise and counterclockwise rotations, linear motion, and magnetic object capture by regulating a magnetic field. As representative examples, the actuator is used to fabricate various smart devices such as smart curtains, biomimetic structures, and a smart gripper that undergo complex and consecutive motion under the influence of multiple stimuli.