Thermo-Spun Reaction Encapsulation Fabrication of Environment-Stable and Knittable Fibrous Ionic Conductors with Large Elasticity and High Fatigue Resistance

The development of knittable fibrous ionic conductors with a wide temperature tolerance, high fatigue resistance and wearing comfort is crucial yet challenging for the emerging wearable skin sensors. Herein, a thermo-spun reaction encapsulation strategy is presented for fabricating a low-temperature tolerant and high fatigue-resistant fibrous ionic conductor. The fibrous ionic conductor demonstrates a core-sheath structure that con-sists of hydrogen-bonded poly(ionic liquid)-backboned ionogel (HB-PILI) and thermoplastic elastomer (TPE) as the core and sheath, respectively. Due to the combination of the ionic conductive core and highly elastic sheath, the resultant HB-PILI@TPE fiber exhibits high stretchability (> 100%), wide temperature resistance (-50 - 50 degrees C), and excellent fatigue resistance (maximum stress retention of 74.3% after 5000 stretching-releasing cycles). As a result, fibrous strain sensors based on the resultant HB-PILI@TPE fiber demonstrate fast response time (less than100 ms), high-yet-linear sensitivity (gauge factor of 1.05), and excellent cyclic stability (> 3000 cycles). Importantly, the fibrous sensor also shows stable responses to various strains (0 - 100% strain) and frequencies (0.01 - 0.2 Hz). Moreover, the HB-PILI@TPE fiber is capable of being easily weaved into a fabric that could maintain high mechanical elasticity in a wide temperature range. As a proof of concept, the as-assembled fibrous ionic sensor is capable of being attached to human skin and monitoring the movements of large and facet joints in real-time, showing high wearing comfort, large sensitivity and wide detecting range. Therefore, the developed fibrous ionic conductors that are fabricated by the thermo-spun reaction encapsulation method are promising for fabricating high-performance wearable skin sensors with excellent wearing comfort and high environmental tolerance.