Recent Progress in Shape-Transformable Materials and Their Applications

Abstract

© 2021, This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.Carefully designed geometries and materials can program desired shapes. In this review, we introduce shape-transformable materials and their recent applications in electronic devices and robots. Strain-guiding shape transformation can be achieved by geometry design or materials design, which can program the magnitude and direction of strain to develop desired shapes. For the geometry design, we discuss origami and kirigami, which transform 2D sheet materials into desired 3D shapes via local deformations caused by fold creases and cut openings. The desired shape can be programmed by controlling the length and alignment of folds or cuts. For the material design, heterogeneities in materials can develop strain driven shape transformation. Heterogeneities in materials include those in anisotropic materials, graded materials, or mixtures of different materials. Shape-transformable materials can be prepared by introducing heterogeneities into stimuli-responsive materials, including inflatable materials, shape memory polymers, liquid crystal elastomers, and hydrogels. The development of shape-transformable materials has led to innovations in energy storage devices, displays, sensors, epidermal electronics, actuators, and robots. Graphical abstract: [Figure not available: see fulltext.]