An ultra-stretchable fiber sensor with high linearity and durability via thermal drawing

With the fast-evolving landscape of flexible and wearable electronics, functional fibers for withstanding high strains in smart wearables, soft robotics, and health monitoring systems are under increasing demands. We report ultra-stretchable and conductive fibers with a thermal drawing process, controlled and engineered for precise motion sensing. This approach enables uniform fibers with microcavities, facilitating scalable production of elastic and functional fibers through a simple fabrication process. Integrating liquid metal (Eutectic Gallium-Indium-Tin alloys) into the elastic fiber yielded a device with a high gauge factor (GF) of 0.91, remarkable linearity (R2 = 0.999), rapid response time (100 ms), and low hysteresis (<3%) up to 1000% strain. The SFCSS could be readily integrated into textiles, such as gloves and clothing, enabling detection of a wide range of human motions, including static sensing of finger motion, knee posture and dynamic activities of standing, sitting, squatting, walking, and running. Additionally, the SFCSS demonstrated effectiveness in measuring boundary-lengths of irregular objects, supporting applications in soft robotics. The ultra-stretchable capacitive strain sensor developed in this work provides a new approach to enable wearable electronics and smart textiles for the upcoming era of interactive human-machine interfaces and digital healthcare.