Smart clothing experiments have been focused largely on weaving conductive threads and yarns into fabric that can then be used to connect digital sensors and other devices. Researchers at the University of Bath have taken a different approach. Rather than make the entire fabric “smart,” they used conductive threads sewn into garment seams as sensors that accurately track the wearer’s motions. The English study suggests that conductive seams could track more subtle movements than today’s smartwatches or wristbands.

The research team sewed conductive yarn at strategic locations within smart garments. The yarn, made of resistive hybrid metal-polymer, becomes a sensor when activated by a low-voltage current. As the wearer of the garment moves, the amount of tension in the seams continually shifts, and the voltage-current changes as the yarn stretches during tension resistance. 

To test the conductive seams, the team designed bodice garments that cover the torso. They recorded the yarn’s sensor outputs during repetitions of three movements inspired by yoga. The study recorded voltage changes in different seam placements and stitching patterns, including straight, zigzag, and double zigzag stitches. Those investigations demonstrated that stitch type affected sensor stability and that a greater number of seams as well as strategic seam placements allowed for better discrimination between movements. 

Having established that seam-based movement tracking can record subtle movement changes, the researchers hope to see further optimization of garments with conductive seams. Certainly, such garments would improve fitness tracking, but seam-based tracking could have much broader applications. Examples might include clothing that lets physical therapists detect accuracy during rehabilitation exercises, tracks gait changes for diagnosis of neurological conditions, or provides remote monitoring for fall-risk patients.