Fabrication of a Highly Stretchable, Wrinkle-Free Electrode with Switchable Transparency Using a Free-Standing Silver Nanofiber Network and Shape Memory Polymer Substrate

Abstract

Transparent and stretchable electrodes (TSEs) are a key technology for the next generation of stretchable electronics and optoelectronics. Metallic nanofibers are widely used because of their good optoelectrical properties, but they demonstrate low stretchability. To enhance stretchability, fabricating in-plane buckled nanofibers with the aid of a prestrained substrate has become crucial in this research field. Here, a composite comprising shape memory polymer-TSE (SMP-TSE) using crosslinked polycyclooctene as a substrate, which shows wrinkle-free deformation and switchable optical transparency, is fabricated. Because of its considerable elongation without residual strain and the shape memory behavior of polycyclooctene, in-plane buckled nanofibers are formed effectively. For fabrication of SMP-TSE, continuous and thin metallic nanofiber that can maintain its structural integrity is required; therefore, electrospinning and an ultraviolet reduction process to create a free-standing, conductive, nanofiber network are used. Because of its in-plane buckled nanofibers, the electrode maintained its resistance during 3000 cycles of a bending test and 900 cycles of a tensile test. Furthermore, SMP-TSE is able to electrically control its temperature, optical transparency, elastic modulus, and shape memory behavior. Finally, the use of SMP-TSE in a smart display that can control its optical and mechanical properties is demonstrated.

Keywords: shape memory polymers; silver nanofibers; stretchable electrodes; switchable transparency; wrinkle-free substrates.