Developing a highly-conductive and strength cotton yarn through dual shell architecture of graphene for smart wearable devices

The development of textile-based flexible wearable electronics has received increased attention owing to its potential application in personalized thermotherapy, human health monitoring, and human-interactive sensing. Cotton yarn is an inexpensive, extensively used material suitable for the above applications. However, the use of commercial cotton yarn presents issues regarding electrical insulation and tensile properties. Functionalizing pristine cotton yarn and simultaneously improving its electrical conductivity and mechanical properties remains a challenge. In this study, a graphene-cotton yarn with a dual shell interfacial structure was designed by the interface modulation strategy. Cationic waterborne polyurethane was introduced into the functionalization interface and played an interfacial linking molecule role. The inner shell (reduced graphene oxide, rGO) exhibits electrostatic attraction to the modified cotton yarn substrate, while the outer shell (graphene) generates a continuous and effective conductive network. The resultant graphene-cotton yarn exhibits a high electrical conductivity of 5.50 × 103 S·m−1. The conductive yarn exhibits an extraordinary tensile strength of 194.36 ± 19.82 MPa and a toughness of 32.66 ± 1.13 MJ m−3, which are 2.1 and 3.6 times higher than that of pristine cotton yarn, respectively. Additionally, we have demonstrated the capabilities of the designed graphene-cotton yarn in prototype textile-based applications, such as personalized thermotherapy, human health monitoring, and braille identification. This research expands the prospects of electronic textiles in the field of flexible wearable applications.