Multifunctional hierarchically braided yarns for advanced wearable human motion monitoring

Helical braided yarn was fabricated via PANI-assisted copper nanoparticle deposition and industrial braiding techniques. • The braided yarn exhibits high stretchability (up to 220% strain) and a broad sensing range. • The braided yarn demonstrates strain sensing, Joule heating, and antibacterial activity (87.2% against E. coli). • The braided conductive yarn enables motion detection, Morse code transmission, and real-time machine interaction. Fiber-based electronics with excellent stretchability and functionality have gained attention in wearable devices, but achieving both exceptional conductivity and stretchability at an industrial scale remains extremely difficult. Herein, we develop a continuous manufacturing process using an industrial braiding machine for stretchable braided composite yarns (SBCYs) with a hierarchically wrapped core structure. While a copper coated polyamide filament wrap layer offers multifunctional properties, the spandex core gives the SBCY exceptional stretchability and resilience. Waterborne polyurethane's outermost layer enables environmental stability. PPI and braiding angle are the key processing parameters investigated for tunable stretchability, while the core draw ratio optimized and kept constant. The SBCY demonstrates exceptional stretchability up to 220% strain, GF max  = 32.1, excellent cyclic durability of 18,000 cycles, and high electrical conductivity of 7.88 S/cm at zero strain under optimal conditions, which is attributed to a discontinuous copper nanoparticle network on a polyaniline conductive polymer layer. Furthermore, the WPU-coated SBCY exhibits 87.2% antibacterial efficacy against E. coli and programmable electrothermal behavior, stable 36 °C heating at 3.3 V. In order to enable advanced wearable electronics with seamless integration into textiles, particularly for continuous rehabilitation monitoring of joint movements in post-stroke or post-injury patients, this work proposes a scalable manufacturing method for stretch-tunable conductive yarns. This study presents a multifunctional braided yarn integrating copper-plated polyamide with spandex for enhanced stretchability. The yarn enables real-time motion detection, efficient Joule heating, and antibacterial activity via controlled copper ion release, which effectively eliminates bacteria. This design offers a promising e-textile platform for smart health monitoring and infection prevention. Download: Download high-res image (131KB) Download: Download full-size image