A Capacitive ppmv Moisture Sensor with Hybrid Oxide-Polymer Sensing Film

In this work, the fabrication of a capacitive sensor for humidity sensing using graphene oxide and polyvinyl alcohol composite material is accomplished. The graphene oxide was synthesized using a modified Hummer's method and was subjected to materials characterization such as Field Emission Scanning Electron Microscopy (FESEM) and X-Ray Diffraction (XRD). A nanocomposite thin film was fabricated using a solution casting method. The sensor was fabricated by using silver conductive paint as one electrode and polymer nanocomposite as a dielectric separator of two metal plates. The moisture content is measured in ppm. The responses of the sensor were measured corresponding to the moisture content in dry nitrogen gas within the range of 38–10000 ppm using an impedance analyzer. The capacitance value increases from 352 pF to 390 pF as the moisture level increases from 38 ppm to 10000 ppm. The fabricated sensor even offers significant sensitivity at low moisture. Some appealing features of the sensor are cost-effective fabrication and linear characteristics. The experimental analysis shows that graphene oxide with PVA is having the potential for capacitive humidity sensing applications.