A Knittable, Muscle-Fiber-Inspired Fiber with Ultra-Stretchability, Waterproof Property and High Conductivity for Wireless Power and Wide-Range Sensing
Conductive fibers face a fundamental trade-off between high electrical conductivity and substantial mechanical stretchability, which critically undermines their reliability under extreme or dynamic mechanical conditions. To overcome this challenge, we report a bio-inspired, hierarchically structured conductive fiber engineered by mimicking the parallel-fibril architecture and integrated matrix of skeletal muscle. This fiber is constructed from multiple parallel spandex yarns as the elastic core, a continuous liquid metal (LM) layer as the conductive pathway, and a composite waterborne polyurethane (WPU)/fluoropolymer (FP) sheath as the protective matrix. This unique architecture concurrently delivers exceptional stretchability (>3500%), high electrical conductivity (3.76 × 10^5 S m−1), and outstanding stability against water and mechanical abrasion. Leveraging its excellent conductivity and mechanical compliance, the fiber can be woven into textiles and function as a receiving coil for efficient wireless power transfer. Additionally, a twisted-pair capacitive strain sensor fabricated from this fiber demonstrates a broad, linear response up to 1000% strain. When integrated into garments, the sensor effectively monitors a wide range of physiological activities, from gross joint movements to subtle biological signals, including wrist pulse, vocal vibration, ballistocardiogram, and respiration. This work presents a conductive fiber that integrates high conductivity, ultra-stretchability, waterproofness, and long-term durability, offering a robust material platform and a scalable fabrication strategy for advancing all-weather health-monitoring systems, smart textiles, and next-generation wearable electronics.