A truly-programmable mechanical metamaterial using magnetic actuation

Mechanical metamaterials are engineered systems with a sub-structure that, when tiled, exhibits physical properties that may not exist in conventional bulk materials. While disrupting the definition of a ‘material’, the periodicity or the internal unit structure of a metamaterial is often optimized to target a specific (set of) function(s) or mechanical behavior. As such, upon fabrication, standard metamaterials are effectively “programmed”, once and for all, and their functionality cannot be altered a posteriori. Here, we show a truly-programmable metamaterial where both the periodicity and the internal structure are preserved during fabrication but each unit cell can be independently programmed and reprogrammed, reversely and on-demand. Programming of individual cells is achieved by switching between the equilibrium states of a multi-stable elastic shell using magnetic actuation. When tiled into sheets or columns, we are able to tune the effective mechanical properties of our system including its stiffness, strength, and localization strain. Through a combination of quasi-static compression of experimental fabricated prototypes and finite element simulations, we demonstrate both the programming and the range of the exhibited mechanical response of our designs.