Bioinspired multi-responsive soft actuators controlled by laser tailored graphene structures.

By exploiting aligned cellulose fibrils as geometrically constraining structures, plants can achieve a complex programmable shape change in response to environmental stimuli. Inspired by this natural prototype, a series of manmade materials with aligned structures have been developed and employed in self-morphing materials. However, in these cases, the constraining materials are fabricated and aligned in separate processes. In botanic systems, a more efficient way is adopted, in which the aligned microstructures are simultaneously synthesized and aligned in one bottom-up process. Herein, we report a bioinspired bottom-up approach to fabricate laser induced graphene (LIG) structures which resemble the aligned microstructures of the cellulose fibrils in plants. Such LIG structures serve as geometrically constraining materials to precisely control the shape changing behaviors of soft actuators made from polymer and LIG layers. Meanwhile, the LIG structures also serve as functional materials to absorb photo and electrical energy to stimulate motions of the soft actuators. Taking advantage of the geometrically constraining effect from the aligned LIG structures, a series of programmable actuations stimulated by electricity, light, organic vapor, and moisture were demonstrated. Furthermore, the soft actuators also act as soft grippers and walking robots upon different stimuli, indicating their potential applications in soft robotics, electronics, microelectromechanical systems, and others.