Wide range and stable ink-jet printed humidity sensor based on graphene and zinc oxide nanocomposite

Nanocomposite materials are being used for different applications due to their hybrid and unique properties. In this paper, we propose a humidity sensor based on Graphene and zinc oxide nanocomposite thin film. The composite combines the advantages of both the individual materials and improves sensor performance. Addition of conductive graphene to the insulator ZnO results in fall of intrinsic impedance and also in improvement of sensitivity at low relative humidity levels. The sensor consists of silver inter-digital electrodes (IDEs) that are printed on a low cost transparent polyethyleneterephthalate (PET) substrate by DMP-3000 with dimension of 100 µm finger width, 50 µm spacing, and 500 nm thickness. To achieve a high sensitivity and wide sensing range, the active layer of composite thin film was deposited over the IDEs through spin coating to achieve a thickness of ~ 300 nm. The sensor can effective detect relative humidity in range of 0–85% RH with fast response and recovery times of 1 and 2 s respectively that are comparable to high end commercial sensors.