MAE Department - PG Seminar - Transformable Extremal Metamaterials: Origami-inspired Design & Broadband Elastic Wave Control

Unlike classic elastic materials which generally exhibit six orthogonal eigenmodes of deformation, extremal metamaterials can be engineered to have a number of “zero modes”, deformation modes that cost little to no elastic energy. In fact, the number of zero modes can alter the ordinary elasticity tensor from the state of null-mode (solid-state) to the states of uni-mode, bi-mode, tri-mode, quadra-mode, penta-mode and the state of hexa-mode (near-gaseous state), which brings peculiar wave control abilities, such as perfect underwater acoustic cloak and negative reflection. Here, we show an origami-inspired 3D extremal metamaterial design with reconfigurable number of zero modes, and experimentally demonstrate its transformability ranging from all seven types of extremal metamaterials. Reprogrammable elastic wave controls are further investigated in 1D-, 2D and3D-systems. Our work sheds lights on the design of flexible mechanical metamaterials, which can be potentially extended from the mechanical to the electro-magnetite, the thermal or other types.