Spray Deposition of Conjugated Polymer/Graphene Ink as an Electrode in Future Chemical Biosensing Devices

In this study, a solution of conjugated polymer PEDOT:PSS ink mixed with graphene was spray deposited on a flexible substrate at different deposition conditions. The film thickness, sheet resistance, surface roughness and transparency were measured for the samples produced at different temperatures of spraying and a different number of spraying cycles. The most favorable conditions for obtaining uniform, low resistive, and highly transparent film in a repeatable manner were determined. At a substrate temperature of 100 °C, the sheet resistance was 56.6 Ω/sq, the surface roughness was 5.95 nm and the average transparency in the visible range of wavelength was 91 %. The coating is intended for electrodes in a sweat sensor, which will be interfaced with transition metal chalcogenides and MXenes in different sensing architectures that can be electrical, or optical. As such, the obtained results for the PEDOT:PSS/graphene coatings are according to the state-of-the-art of the conventional metal-oxide transparent films. The parameters are satisfactory and the organic electrode can be incorporated into a device structure.