Sewing machine stitching of polyvinylidene fluoride fibers: programmable textile patterns for wearable triboelectric sensors

Textile-based sensors can perceive and respond to environmental stimuli in daily life, and hence are critical components of wearable devices. Herein, self-powered triboelectric wearable sensors are fabricated using polyvinylidene fluoride (PVDF) fibers stitched by using a sewing machine. The excellent mechanical properties of dry-jet wet spun PVDF fibers allow the use of a sewing machine to stitch them into diverse programmable textile patterns on various fabric substrates. Such stitches can provide remarkable triboelectric signals when in contact with the opposing surfaces of commercial fabrics, since PVDF has higher electron affinity than other polymers. In addition, PVDF stitch-based triboelectric sensors are flexible, lightweight, wearable, washable, and comfortable. Furthermore, they can detect a broad pressure range (326 Pa to 326 kPa), which is unachievable with conventional textile force sensors, enabling diverse pressure-sensor applications. To demonstrate their use in wearable devices, a smart glove and joint pads are fabricated based on PVDF stitch-based triboelectric sensors. These wearable sensors enable the detection of and distinguishing diverse hand gestures and body motions by generating intrinsic signal patterns for the specific gesture and motions. These sensors also enable real-time self-powered pulse signal monitoring. This work demonstrates a feasible fabrication approach to realize stitched textile sensors using a sewing machine, with many possible e-textile applications.