Symmetry-Breaking Actuation Mechanism for Soft Robotics and Active Metamaterials.

Magnetic-responsive composites that consist of a soft matrix embedded with hard-magnetic particles have recently been demonstrated as robust soft active materials for fast-transforming actuation. However, the deformation of the functional components commonly attains only a single actuation mode under external stimuli, which limits their capability of achieving tunable properties. To greatly enhance the versatility of soft active materials, we exploit a new class of programmable magnetic-responsive composites incorporated with a multifunctional joint design that allows asymmetric multimodal actuation under an external stimulation. We demonstrate that the proposed asymmetric multimodal actuation enables a plethora of novel applications ranging from the basic one-dimensional/two-dimensional (2D) active structures with asymmetric shape-shifting to biomimetic crawling robots, swimming robots with efficient dynamic performance, and 2D metamaterials with tunable properties. This new asymmetric multimodal actuation mechanism will open up new avenues for the design of next-generation multifunctional soft robots, biomedical devices, and acoustic metamaterials.