Flexible printed humidity sensor based on poly(3,4-ethylenedioxythiophene)/reduced graphene oxide/Au nanoparticles with high performance

Wearable and flexible humidity-sensing devices are essential for the real-time monitoring of air humidity in health and environmental applications. We propose a flexible sensor based on a conductive polymer comprising poly(3,4-ethylenedioxythiophene) (PEDOT) and reduced graphene oxide(rGO) to monitor changes in humidity. GO was used as a hard template for the in situ polymerization of EDOT to obtain PEDOT:rGO. Then, PEDOT:rGO-PEI/Au nanoparticles (NPs) ink was prepared through the in situ reduction of Au NPs modified with polyethylenimine (PEI). The ink was printed on the surface of a hydrophilic modified polyethylene terephthalate (PET) substrate using an ink-jet printer to form a specific pattern. After assembly, a PET-based PEDOT:rGO-PEI/Au NPs (PrGANPs) sensor device with high electrical performance, transparency, and sensitivity was obtained for testing at a variety of RH levels. The prepared PET-based PrGANPs sensor printed with 50 layers had a transmittance up to 61% at 500 nm. And the response and recovery times were approximately 20 and 35 s at 98% RH, respectively. Stability was maintained even after bending 200 times, and the sensor could respond within the humidity range of 11%–98% RH, while in response to a wide resistance range of 7.41%–51.60%.