Biological & Soft Matter Seminar: Topology and Hysteresis in a Mechanical “Spin-Ice” Metamaterial

Zoom: https://us02web.zoom.us/j/88904888353?pwd=dDIwaXRxSjlsVElkR0dXdTNPTGhnZz09

Abstract: 

In the field of ``Artificial Spin Ice”, (ASI) a great degree of sophistication has been reached in the design and manipulation of frustration, geometric incompatibility between interacting degrees of freedom, which can generate exotic phases, rich topological effects, and glassy dynamics. Very close parallels exist between ASI and certain mechanical metamaterials, and mappings to spin models can yield many insights. However, the continuous degrees of freedom present in elastic metamaterials allows for the possibility of accommodating frustration in surprising ways, and thus the investigation of mechanical ``spin-ice” systems promises to reveal exciting new physics not seen in magnetic systems. I will present our recent work on a mechanical metamaterial composed of prestressed, bistable square mechanical cells that act as coupled hysterons. These unit cells deform spontaneously, so that the overall metamaterial contains competing local ground-state orientations, which are separated by locally-stressed domain walls. Under textured, cyclic driving from the boundaries, the system exhibits dynamic hysteresis. Moreover, when driving the system from its boundary we can also observe multiple distinct steady states. This mechanical metamaterial exhibits a novel memory of the topology of its initial condition, and can thus have potential application in the development of a mechanical memory storage in materials.