Hollow Polypyrrole Sleeve Based Coaxial Fiber Supercapacitors for Wearable Integrated Photosensing System

Fiber supercapacitors (SCs) are robust power supply for wearable electronics due to their feasibility of weaving into textiles that breathe freely or integration into different functional materials that fit the curved surface of the human body. However, traditional twisted fiber SCs suffer from the low-energy density while coaxial fiber SCs undergo the complicated fabrication process of shell-like electrode. Here, a facile electrodeposition and etch approach to prepare shell-like micrometer hollow polypyrrole sleeve electrode is proposed and then a new type of coaxial fiber SC is assembled. The designed device using solid electrolytes shows a large volume capacitance of 2.44 F cm⁻³, which is 5.95 times higher than that of twisted fiber SCs (0.41 F cm⁻³), fitting well with the theoretical results simulated by ANSYS Maxwell software. An integrated system consisting of the fabricated SCs as power source and CuInS₂ film photodetector as functional units is then presented and weave into a form of smart ring. As-designed self-driven smart ring exhibits stable photocurrent response to white light and excellent flexibility, demonstrating the feasibility of the 1D wearable integrated system.