Self-Folding Metal Origami

Origami-based techniques for creating 3D shapes from 2D patterns via folding have moved from the domain of art to practical engineering. Flat sheets are an appealing starting material for the creation of 3D objects because of 1) the ability to efficiently store and ship stacks of sheets, 2) the compatibility of flat surfaces with a variety of patterning processes such as lithography, and 3) the ability to make sheets via high-throughput manufacturing. Self-folding is the ability of flat sheets of materials to respond to external stimuli (light, heat, magnetic fields, etc.) and rapidly change shape without human intervention. Herein, the self-folding of metals is reviewed, which is particularly important for opening up new applications in robotics, medicine, and reconfigurable electronics. These applications rely on the superior thermal, mechanical, and electrical properties of metals compared with polymer alternatives. The field is reviewed from actuation mechanisms and materials to design approaches and common applications of technologies.