High performance wearable strain sensor based on graphene/cotton fabric with high durability and low detection limit.

Electronic textiles featuring controllable strain sensing capability and comfortable wearability have attracted huge interests with the rapid development of wearable strain sensor systems. It is still a great challenge to simultaneously achieve strain sensor with low cost, biocompatibility, large-area compatibility and excellent sensing performances. Here, two kinds of cotton fabric based strain sensors (CFSS) with different conductive network structures are prepared, i.e., CFSS-90º and CFSS-45º (90º and 45º represent the angles between intertwined direction in cotton yarns and the stretching direction in tension). After multiple dipping process, graphene nanosheets are deposited onto cotton fabrics and then the fabrics are encapsulated by polydimethylsiloxane (PDMS). Morphology analyses reveal that an interpenetrating structure is generated between cotton fabric and PDMS. The strength and elongation at break of CFSS-45º are about 4.5 MPa and 75 % strain, which are higher than the counterparts of CFSS-90º (1.75 MPa and 30 % strain, respectively). In uniaxial stretching test, the two strain sensors exhibit excellent linear current-voltage behavior and fast response time (~90 ms). During the cyclic stretching-releasing test, CFSSs present remarkable reproducibility, durability (10000 cycles at 30 % strain for CFSS-45º) and a sensing capability for detecting very low strain (~0.4 % strain).