Characterization of graphene-based inkjet printed samples on flexible substrate for wireless sensing applications

Inkjet printing is one of the emerging methods for fabrication of electronic devices. The important issue in this area is developing nanomaterial-based inks for different applications such as gas sensors for environmental monitoring. In particular, graphene-based materials have recently gained interest due to their extraordinary properties. However, graphene has hydrophobic nature resulting in poor solubility in the most of the solvents. In order to solve this problem, graphene oxide is mostly used instead of graphene. To retrieve the conductivity, the printed samples are reduced to remove the oxygen containing groups. The major contribution of this paper is focused on the production of conductive graphene-based patterns on the flexible kapton substrate utilizing thermal reduction process. Both printed samples and inks were characterized and analyzed to enhance the quality of printing. The effect of different parameters such as surface modification, annealing condition, thermal reduction atmosphere, setting of inkjet printer, and concentration of ink were investigated. The characterization part includes analysis of the morphology, sheet resistance, conductivity, and viscosity of ink. This work is an important step for future research on the development of wireless graphene-based gas sensors.