A Comparative Study on Performance of Drop Casted and Inkjet Printed Humidity Sensor

In this study, flexible inkjet-printed capacitive humidity sensors were developed using Fujifilm Dimatix 2850 printer. The interdigitated electrodes (IDE) of the sensors were printed with the commercial silver nano-particles ink (AgNPs ink) on the polyethylene terephthalate (PET). To develop the sensing material on the humidity sensors, two methodologies were investigated. The former was a drop-cast method while the latter was an inkjet-printing method. Both utilized graphene oxide (GO) as the sensing material mixed with polyacrylic acid (PAA). The results in capacitance were obtained from experiments conducted in the humidity range from 30 % RH to 80 % RH. It was found that the former to be more suitable working in humidity range of 30 % RH up to 70% RH while the latter more suitable working in humidity range of 30 % RH up to 60% RH. The methodology using the drop-casted method presented higher sensitivity 9.766 pF/% RH compared to the inkjet printing method which was 0.441 pF/% RH. The sensors also exhibited good stabilities during short-term and long-term stability tests under predefined humidity and temperature.