Surface Defects of Electron Irradiation Engineering for Graphene/Polymer Composite-Based Flexible Humidity Sensors

A facile approach for surface defect engineering based on high-energy electron irradiation is proposed here to produce a graphene/polymer composite flexible humidity sensor with high humidity resistance and responsiveness. The responsiveness of the graphene/polymer composite humidity sensor following electron irradiation was ∼22.4-fold greater than the unirradiated humidity sensor. When the relative humidity was 97.3%, the responsiveness of the sensor was 1.2 × 10⁵. In addition, the irradiated humidity sensor maintained an excellent response after 10 water resistance tests. Furthermore, material characterization techniques demonstrated that graphene/polymer composite materials with low crosslinking density could be produced by electron irradiation at the appropriate fluence. Concurrently, the specific surface area of the graphene/polymer composite material was increased, and several oxygen-containing functional groups were generated, providing more active sites for water molecules to enhance the stability and responsiveness of the sensor. Thus, the irradiated graphene/polymer composite humidity sensor has potential applications in human respiratory monitoring and noncontact switching. Moreover, the surface defect engineering of electron irradiation provides a facile strategy for obtaining graphene/polymer composite flexible humidity sensors with high comprehensive properties.