UV ENERGY CURING OF DIELECTRIC LAYER FOR SCREEN PRINTED CAPACITIVE CHEMICAL SENSORS

Functional printing is becoming a new standard in the printing industry and new materials are being developed for use with conventional printing methods. The purpose of our research was to successfully print and measure the change in capacitance of a multi-layered interdigitated capacitor, when exposed to water vapour in air. Commercially available printing inks were applied, including one silver-based conductive ink and one dielectric ink. Conductive structures with resolution of up to 300 microns were printed with a screen density of 120 lines/cm. Two-layered elements of dielectric printing ink and an additional layer of conductive ink were successfully applied onto a printing substrate coated with a conductive indium tin oxide layer. Capacitance of a parallel-plate and interdigitated capacitor was determined by implementing variation in the position of electrodes for measurements. The results confirm that the change of UV energy applied for curing of the dielectric ink has no significant influence on the capacitance of printed sensors, as opposed by the factor of capacitor function and surface area. Capacitance was greater when measured as a parallel-plate capacitor with dielectric layer between two electrodes and a larger surface area than interdigitated in-plane capacitor printed on the same sample. Dissipation factor diminishes with higher UV energy applied for curing of the dielectric ink. Sensor response to changes in relative humidity is even and can be reproduced. Change of capacitance of sensor is higher with increase in relative humidity, thus the prepared sensors are properly responsive.