Decreasing the size of printed comb electrodes by the introduction of a dielectric interlayer for capacitive gas sensors on polymeric foil: Modeling and fabrication

In this work we present a novel strategy to fabricate printed comb electrodes devices with decreased size by the introduction of a thin dielectric layer between the two combs. The electrical insulation of the two polarities prevents short-cuts occurring because of printing defects. In this way, the yield of the process increases as well as its resolution by decreasing significantly the gap between the electrodes. An analytical model is proposed and evaluated, confirming the capability of the method to enhance the nominal capacitance value of comb electrodes capacitors with reduced area. The validation of the proposed method has been performed by fabricating transducers made of inkjet printed silver combed electrodes with a parylene-C dielectric interlayer. The whole process takes place at low temperature, being compatible with the utilized PET substrate. Finally, the potential of such devices for sensing applications with improved performances was demonstrated by inkjet coating the transducers with a humidity sensing layer and characterizing their response for the capacitive detection of relative humidity.