Mechanical Metamaterial-Based Structure with Magnetically Controlled Nonreversibility and Nonreciprocity for Programmable Locomotion.

Programmable mechanical metamaterials hold the key to critical innovations in materials science research, by harnessing relatively unexplored nonlinearities that change effective responses. Effective properties of a metamaterial strongly depend on the reversibility of the deformation process. While most elastic materials show reciprocity and reversibility, the possibility of concurrently observing nonreciprocity, defined as a deformation that is not mirrored when a body is loaded equally from opposite sides, as well as a nonreversible deformation process, opens doors to addressing complex mechanical problems that are crucial from the perspective of soft body dynamics. In this work, a magneto-mechanical metamaterial-based structure is proposed that simultaneously exhibits both of these phenomena by utilizing elastic and magnetically induced nonlinearities. It is shown that such a system can undergo a transition in its static mechanical properties, such as Poisson's ratio and stiffness, leading to stark changes in energy absorption. It is also demonstrated that, thanks to the asymmetric distribution of magnetic inclusions, the entire structure can exhibit an efficient locomotion mechanism suitable for applications in robotics.