Synthesis and inkjet printing of sol–gel derived tin oxide ink for flexible gas sensing application

The fabrication of printed electronic devices based on metal oxide inks requires the formulation of stable suspensions with specific fluidic properties. In our work, a tin oxide based solution was synthesized by aqueous sol–gel method and transformed into an ink with appropriate viscosity and surface tension to be inkjet-printed on polyimide foil and sintered at relatively low temperature. Thermal analysis by TGA/DSC and microstructural analysis by XRD of synthesized sol show that a crystallized structure of SnO₂ could be obtained at 350 °C, which is lower than crystallization temperatures of SnO₂ previously reported in the literature, and entirely consistent with the use of polyimide foil. The stability and the rheological properties of the ink were studied to ensure the jettability criteria of the inkjet printer. Electrical measurements of the printed sensing films were performed to characterize the response to CO gas in different concentrations, at working temperature of 300 °C.