Inkjet printed capacitive transducers on flexible plastic substrates with increase stability

Inkjet printed interdigitated transducers have been produced on flexible substrates and optimized for gas sensing applications by improving the sintering conditions and employing additional passivation procedures, like electroplating with Ni or whole transducer passivation through Parylene-C coating. The results of the performed investigations showed that the transducers printed with Ag ink can be used, as prepared, in capacitive gas sensing structures up to 70% relative humidity only. Higher humidity levels resulted in irreversible shifts of the nominal capacitance and conductance of the transducers. This drawback could be eliminated by the already addressed passivation procedures or upgraded sintering. The gas sensor structures based on the passivated printed transducers displayed good stability and sensing performance, demonstrating that fully printed and flexible capacitive gas sensors are feasible