Formation of wrinkled film layer between symmetrically stretched substrates

Abstract

Due to the recent pursuit of human-friendly form factors for mobile devices and the advancement of IoT technology, the need for highly stretchable electrodes is on a rapid rise. Here we propose a new type of stretchable circuit containing a wrinkled electrode layer between symmetrical stretched substrates. Unlike the bilayer structure, where warpage easily occurs, the symmetric tri-layer maintains its structural stability in higher elongation. Thus, high encapsulation density can be achieved by minimizing the thickness of the substrates without requiring thick foundation layers to avoid warpage. The wrinkled layer is fabricated by sandwiching a thin conductive polymer between two substrates pre-stretched to the same elongation followed by releasing. The thin film layer is wrinkled due to compressive stress during the releasing process. Symmetry reduces global mechanical instabilities such as bending and curling even at an extreme elongation of 300% or more and produces a predictable sinusoidal wrinkle without folding. Using high-performance stretchable electrodes containing Ag-nanowires or graphene has the potential for applications in displays, soft robotics, and ergonomic devices.