Buffering by buckling as a route for elastic deformation

Buckling is the familiar response of thin objects to compression. Less familiar is that small-scale buckles can act as a buffer, enabling objects to access new modes of deformation. This Review illustrates examples of this phenomenon and discusses the physical conditions that make it possible. Thin objects are deformed in a range of applications and at a range of scales, from graphene and the actuators used in soft robots to the light sails of spacecraft. Such deformations are constrained, as it is much easier to bend than to stretch a thin object - this constraint is often used to determine the deformations that are allowed and those that are prohibited. Recently, however, a series of applications has emerged in which apparently prohibited deformations are observed. In many of these examples, the apparent ability to stretch and compress (as well as bend) is facilitated by excess material that is stored in microscopic buckled structures: the changes in length that are required to enable particular deformations are 'buffered by buckling'. In this Review, I discuss buffering by buckling as a means of enabling elastic deformations without significant changes of material length (thereby distinguishing this mechanism from material swelling and growth). I discuss a range of examples from technology and nature and consider the conditions under which buffering by buckling operates.