Performance metrics for shape-morphing devices

Shape-morphing devices, with their capacity to undergo structural transformations, are on the verge of revolutionizing multiple domains, from human–machine interfaces to biomedical and aerospace applications. This Perspective classifies shape-morphing devices into two categories: pattern-to-pattern shape-morphing devices that deform from a starting shape to a predefined set of one or more deformed shapes, and programmable shape-morphing devices that can morph into different shapes on demand. We highlight the need for standardized assessment approaches to compare the performance of different shape-morphing devices and introduce an array of proposed metrics that are tailored to assess the functionality of these devices at the material, device and system levels. Notably, we propose a mathematical metric to quantify the complexity of a surface and a set of standard surfaces for evaluating programmable shape-morphing devices, providing objective benchmarks for this expanding field.