Shape-morphing metamaterials

Mechanical metamaterials use geometric design to achieve unconventional properties, such as high strength at low density, efficient waveguiding and complex shape morphing. The ability to control changes in shape builds on the complex relationship between geometry and nonlinear mechanics, and opens new possibilities for disruptive technologies across diverse fields, including wearable devices, medical technology, robotics and beyond. In this Review, we examine the current state of the field of shape-morphing metamaterials and propose a unified classification system for the mechanisms involved, as well as the design principles underlying them. Specifically, we explore two main categories of unit cells — those that exploit structural anisotropy and those that exploit internal rotations — and two potential approaches to tessellating these cells, based on kinematic compatibility or geometric frustration. We conclude by discussing the available design tools and highlighting emerging challenges in the development of shape-morphing metamaterials.