Highly sensitive textile-based strain sensors using poly(3,4-ethylenedioxythiophene):polystyrene sulfonate/silver nanowire-coated nylon threads with poly-L-lysine surface modification

Here, we demonstrate highly sensitive textile-based strain sensors using poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS)/silver nanowire (Ag NW)-coated nylon threads for electronic textile applications. For the coating of Ag NW and PEDOT:PSS layers, we employed a simple and cost-efficient 'dip and dry' method which facilitated conformal coating of Ag NWs and PEDOT:PSS on cylindrical-shaped nylon filaments. In this study, to improve the stability of the strain sensor, we employed poly-L-lysine (PLL) surface modification of nylon threads prior to the Ag NW coating process. By stability tests, it was found that the PLL surface modification significantly improved the operational stability of the strain sensor, attributed to the enhanced adhesion between Ag NWs and nylon thread. By mechanically sewing the PEDOT:PSS/Ag NW/nylon thread onto a fabric, a textile-based strain sensor was fabricated, exhibiting strain gauge factors of 1.69-3.31 (strain range of 5-20%) and stable operation up to ca. 1000 stretch-release cycles. Furthermore, as a possible extensive use of the PEDOT:PSS/Ag NW/nylon threads, a capacitive-type touch/pressure sensor was also demonstrated on a textile platform.