Memory, directed aging and Nature’s greed
In a crystal with only one atom per unit cell, all atoms play the same role in producing the solid's global response to external perturbations. Disordered materials are not similarly constrained and a new principle emerges: independence of bond-level response. This allows one to drive the system to different regimes of behavior by successively removing individual bonds. We can thus exploit disorder to achieve unique, varied, textured and tunable global response or long-range interactions inspired by allosteric behavior in proteins. While this approach is successful for systems with only a few degrees of freedom, it is difficult to scale up the number of elements to be controlled or scale down the size of the individual components. However, because a material has a memory of under what conditions it has been aged, we can direct the aging using Nature’s greedy algorithms to achieve a variety of mechanical functionalities.