Mechanical memories in solids, from disorder to design

TL;DR

This paper reviews recent advances in understanding how solids, including amorphous and glassy materials, can form and utilize mechanical memories, with implications for material design and physical computing.

Contribution

It synthesizes recent research on mechanical memory formation in solids and explores their applications in material design and mechanical metamaterials.

Findings

Memories of deformation in amorphous solids are linked to particle rearrangements.

Mechanical memories can be applied to a wider range of solids and glassy matter.

Understanding memory in solids aids in designing materials with embedded functionalities.

Abstract

Solids are rigid, which means that when left undisturbed, their structures are nearly static. It follows that these structures depend on history -- but it is surprising that they hold readable memories of past events. Here we review the research that has recently flourished around mechanical memory formation, beginning with amorphous solids' various memories of deformation and mesoscopic models based on particle rearrangements. We describe how these concepts apply to a much wider range of solids and glassy matter -- and how they are a bridge to memory and physical computing in mechanical metamaterials. An understanding of memory in all these solids can potentially be the basis for designing or training functionality into materials. Just as important is memory's value for understanding matter whenever it is complex, frustrated, and out of equilibrium.