Ultrastretchable Electrochromic Hydrogel and Asymmetric Electrodes for Novel Flexible and Stretchable Passive-Matrix and Active-Matrix Dynamic Information Displays.

Displays are critical information-output components for wearable electronics, making their flexibility and stretchability a significant research focus. Electrochromic hydrogels have garnered considerable attention for flexible display applications due to their high flexibility, stretchability, and biocompatibility. Significant challenges are realizing diverse pattern display with hydrogel-based devices, and their operation under stretching. In this work, a highly stretchable electrochromic hydrogel based on polyacrylamide/ethyl viologen was synthesized by γ-radiation method. Subsequently, a conductive, electrical stable, and stretchable asymmetric Ag/Ag nanowire polyurethane electrode was developed. By assembling them with designed circuits and driving programs, we successfully fabricated a 5 × 5 passive-matrix display and a four-digit seven-segment active-matrix display. These flexible and stretchable devices clearly display various patterns like numbers, and can switch content freely under program control. They could work reliably under bending and stretching deformations, demonstrating their potential as intuitive human-machine output interfaces for wearable electronics. This work significantly advances the pattern diversity and dynamic information showing ability of hydrogel-based electrochromic displays, presenting a promising design for dynamic information showing components in next-generation wearable devices.