A reprogrammable metamaterial with memory

Metamaterial properties are usually fixed at fabrication. We built one that can be rewritten like a hard drive: each cell is a mechanical bit with two stable states it holds with no power. A magnetic pulse snaps an embedded bistable shell to its other equilibrium to write a cell, loading reads it nondestructively, and the two states differ in stiffness, strength, and stored energy by about an order of magnitude. A single pair of coils addresses any cell in an array, so the binary pattern of ON and OFF cells programs the bulk response of one identical lattice, carrying addressable, nonvolatile memory into the mechanical domain. The work was published in Nature.