Core-Sheath Fiber-Based Wearable Strain Sensor with High Stretchability and Sensitivity for Detecting Human Motion

Fiber-based strain sensors are considered to be an important part of smart wearables due to their flexible performance, lightness, and easily processing into various structures. However, the low sensitivity of fiber-based strain sensors has limited their real-life applications for detecting human movements. In this work, a poly(styrene-butadiene-styrene) (SBS)/multi-walled carbon nanotube (MWCNTs) core-sheath fiber (SSCCSF) strain sensor is fabricated via a simple and facile coaxial wet-spinning method. The cross-sectional morphology, the mechanical properties, and the electromechanical performance of the SSCCSFs are investigated. Scanning electron microcopy results show that SSCCSFs have a bean-like cross-section with SBS as the core and SBS/MWCNTs as the sheath. Electromechanical performance evaluation confirms that the SSCCSF show a high sensitivity in a broad working range (gauge factor = 25832.77 at 41.5% strain) and excellent durability (5000 cycles at 10% strain). Furthermore, the SSCCSF displays outstanding sensing performance for detecting large motions in human movements including hand joint bending (such as knuckles and wrists) and subtle motions in physiological activities, involved in swallowing behavior, breathing, and pulse beat. This study demonstrates the potential application of SSCCSFs for wearable electronics with activity monitoring sensors.