Bilayer Self‐Folding Method with High Folding Force and Angle by Suppressing Delamination of Shrink Layer

Abstract

Heat‐shrinkable films commonly serve as active materials for self‐folding owing to their capability to fold all hinges upon heating. For origami‐based electronic devices, the self‐folding of the metal layer is necessary. Nevertheless, the self‐folding angle is low owing to the high bending stiffness of metal layers and the low adhesion of heat‐shrinkable films. Here, we introduce a bilayer self‐folding technique that effectively suppresses delamination of the shrink layer, thereby achieving a high folding force and angle. A polyolefin film mechanically fixed on the metal substrate serves to inhibit delamination, regardless of the adhesive properties of the shrink layer. This is achieved by applying adhesives within holes fabricated on the shrink layer. Conventional methods using an adhesive layer to fix the shrink layer lead to delamination at temperatures above 100°C, resulting in a decrease in self‐folding angles. In contrast, our novel fixing method yields a folding angle of 161° at 140°C, with a shrinkage rate of 69%. To demonstrate the versatility of our proposed technique, we self‐fold various origami structures, including Miura‐ori, scissors, cranes, and tessellation with chip LEDs. The introduced method broadens the range of substrate materials suitable for self‐folding and offers new possibilities for the development of origami devices. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.