Strain-Insensitive Supercapacitors for Self-Powered Sensing Textiles

Yarn-based supercapacitors and sensors can be easily integrated into textiles to form flexible and lightweight self-powered wearable electronic devices, which enable stable and continuous signal detection without an external power source. However, most current supercapacitors for self-powered systems lack the stretchability to adapt to complex human body deformations, which restricts their application as a stable wearable power source. This study presents a high-performance strain-insensitive yarn supercapacitor via prestretching <i>in situ</i> polymerization strategy, which can be integrated into self-powered wearable sensing textiles. The supercapacitor delivers a high specific capacitance of 20.79 mF cm^-1 (116.94 F g^-1), a power density of 37.54 μW cm^-1 (211.22 W kg^-1), and an energy density of 1.85 μWh cm^-1 (10.39 Wh kg^-1). The strain-insensitive ability is demonstrated with nearly unchanged performance at a high static strain of 200%, dynamic strain rates of 10% s^-1, and retains 96.46% of its capacitance after 3500 cycles under 50% strain. The pressure sensor, featuring a striped coating structure, shows a high sensitivity of 0.67 kPa^-1 and a short response time of 100 ms. The strain-insensitive yarn supercapacitors with superior reliability serve as an energy source to power pressure sensors that efficiently recognize Morse code, showing great potential in truly wearable health monitoring and rehabilitation training applications.