Coaxial carbon nanotube/polymer fibers as wearable piezoresistive sensors

Abstract

Stretchable sensors that can be incorporated into clothing are currently attracting tremendous interest for use as smart textiles and in flexible electronics. Herein, we report a facile, coaxial wet-spinning technique for the fabrication of high-performance, stretchable, fiber-shaped piezoresistive sensors using elastic silicone and multi-walled carbon nanotubes (MWCNTs). The coaxial fibers exhibited a variety of desirable parameters for strain sensing applications, including large workable strain range (>300%), high sensitivity (gauge factor up to 1378), and long-term stability. Most interestingly, the coaxial fiber-shaped strain sensor exhibited a negative piezoresistive effect below a critical strain value, which was independent of the loading speed. The resistance relaxation behavior of the strain sensor was also investigated. The relaxation time decreased as the strain amplitude was increased. In addition, the coaxial fibers showed excellent tactile sensing performance when subjected to compressive forces. The tactile sensor typically demonstrated a high force sensitivity of 66.7% mN−1 within a range of 160–300 mN, a low detection limit of 10 mN, a fast response time (<200 ms), and high stability. These outstanding properties demonstrated that these materials have great potential for a range of electronics and robotic applications, including monitoring human motions, tactile sensing arrays, and human–machine interfaces.