Effects of stitch classes on the electrical properties of conductive threads

Abstract

Bio-physical signal measurement tools embedded in clothing are becoming a viable alternative in mobile health monitoring systems, particularly Wearable Electronic Textile-based Systems (WETS). To assure clinical viability, utilizing flexible and inconspicuous conductive media that can acquire and transmit reliable signals while assuring signal durability and biocompatibility are particularly important when developing WETS for medical applications. To accomplish this task, conductive threads are emerging as an appropriate electrical medium for health monitoring garments. However, little has been studied on the behavior of these conductive threads under various conditions. We report here the electrical conductive properties of specific conductive threads under two conditions: (i) as sewn configurations onto a textile substrate with different stitch types and (ii) as independent strands under controlled extension independent from a sewing machine. Statistical results showed that the stitch class and thread location significantly influenced the electrical resistance of the conductive thread, revealing the chain stitch to provide resistance even lower than the un-stitched conductive thread. In addition, under controlled extension all three of the conductive threads exhibited both a hysteresis and a stress-relaxation effect. These are important phenomena to examine when conductive threads are incorporated into WETS because the choice of stitch type will influence the strength of the signals received and transmitted, while the wearers’ body movements will cause the threads to encounter multi-axial stretch. Knowing the influence of stitch type, stretch, and relaxation on conductive thread resistance will inform objective design and manufacturing decisions for developing clinical-grade textile-based electrical circuits for medical applications.