Highly Conductive, Flexible, and Robust Silver Nanowire-Embedded Carboxymethyl Cellulose/Poly(3,4-Ethylenedioxythiophene):Poly(Styrenesulfonate) Composite Films for Wearable Heaters and On-Skin Sensors

Highly conductive, flexible, and durable silver nanowire (AgNW)-embedded carboxymethyl cellulose (CMC)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) (s-CMC/PEDOT:PSS) composite films were investigated for application in wearable heaters and on-skin sensors. The electrical conductivities of the CMC/PEDOT:PSS composites were optimized by controlling the PEDOT:PSS weight ratio in CMC, and the sheet resistance decreased significantly from 6828 (CMC:PEDOT:PSS = 1:5) to 83 Ω/sq (CMC:PEDOT:PSS = 1:17). Furthermore, AgNW networks were embedded onto the surface of the CMC/PEDOT:PSS films to further enhance their conductivity. The introduction of AgNW networks resulted in a significant decrease in the sheet resistance of the composites from 81 to 7 Ω/sq. In addition, the s-CMC/PEDOT:PSS composite film exhibited high mechanical stability in repeated bending tests. The uniformly distributed AgNWs inside the composites enhanced the electrical contact between the conducting PEDOT:PSS domains in the CMC matrix. Based on the highly conductive, flexible, and robust s-CMC/PEDOT:PSS composite films, high-performance wearable heating devices and on-skin sensors were fabricated. The wearable heater achieves a high temperature of 159.5 ℃ with uniform temperature distribution. Furthermore, on-skin sensors with s-CMC/PEDOT:PSS composites were conformably integrated on human skin which successfully detected various human motions, including finger bending, wrist bending, skin touch, ankle motions, and walking in real-time. The sensors exhibit high sensing performance with high sensitivity, conformability, superior mechanical robustness, and low power consumption. The high-performance s-CMC/PEDOT:PSS composite film could be a promising flexible and conductive composite material with new opportunities in next-generation electronics.