A Scalable Durable and Seamlessly Integrated Knitted Fabric Strain Sensor for Human Motion Tracking

Abstract

AbstractTextile strain sensors capable of monitoring human physiological signals and activities have great potential in health monitoring and sports. Integrating them into apparel to be wearable, repeatable, and sensitive remains a great challenge, impeding their practical applications. This paper reports a fabric strain sensor that can be seamlessly integrated into various apparel under precise tension through industrial‐scale production. A conductive core‐sheath polyester/carbon black multifilament (CSPCF) produced on a melt spinning machine is wrapped onto a spandex yarn via a yarn covering machine to manufacture a stretchable double‐covered conductive yarn (DCCY). The fabric strain sensor is specially designed and automatically produced on an industrial knitting machine by precisely integrating the DCCY into an elastic fabric. The sensing principle is contact and separation between neighboring spiral CSPCFs by stretching an arched “rainbow spring” like DCCY embedded in the fabric. The sensor has a high sensitivity of 2% strain detection limit, excellent durability and repeatability for 10 000 cycles, and a wide sensing range of 60% strain, even in a wet state or after repeatedly washing, bending, or rubbing. Three wearable products, by seamlessly integrating the sensor, are demonstrated to effectively and quantitatively detect bending motions of finger, elbow, and knee.