Magneto-Mechanical Metamaterials with Widely Tunable Mechanical\n Properties and Acoustic Bandgaps

Mechanical metamaterials are architected manmade materials that allow for\nunique behaviors not observed in nature, making them promising candidates for a\nwide range of applications. Existing metamaterials lack tunability as their\nproperties can only be changed to a limited extent after the fabrication. In\nthis paper, we present a new magneto-mechanical metamaterial that allows great\ntunability through a novel concept of deformation mode branching. The\narchitecture of this new metamaterial employs an asymmetric joint design using\nhard-magnetic soft active materials that permits two distinct actuation modes\n(bending and folding) under opposite-direction magnetic fields. The subsequent\napplication of mechanical forces leads to the deformation mode branching where\nthe metamaterial architecture transforms into two distinctly different shapes,\nwhich exhibit very different deformations and enable great tunability in\nproperties such as mechanical stiffness and acoustic bandgaps. Furthermore,\nthis metamaterial design can be incorporated with magnetic shape memory\npolymers with global stiffness tunability, which further enables the global\nshift of the acoustic behaviors. The combination of magnetic and mechanical\nactuations, as well as shape memory effects, imbue unmatched tunable properties\nto a new paradigm of metamaterials.\n