Flexible Capacitive Humidity Sensor based on Fluorinated Graphene

Abstract

A novel and flexible capacitive humidity sensor was successfully fabricated using additive screen printing process. A silver (Ag) ink was deposited on the polyimide substrate in interdigitated finger pattern using screen printing process. A humidity sensitive fluorinated graphene ink was drop casted on the Ag-based interdigitated electrodes. The capacitive response of the fabricated humidity sensor towards varying relative humidity (RH) levels ranging from 20% RH to 70% RH was investigated. An overall capacitance change of 311.5% was observed for the fabricated humidity sensor at an operating frequency and voltage of 1 kHz and 1 V, respectively. The effect of operating frequency on the sensor's performance was also investigated. A decrease in the relative capacitance change was observed as the frequency of the applied electric field increases. A sensitivity of 311.5 %/%RH, 87.9 %/%RH, 61.7 %/%RH, 45.8 %/%RH, and 35.5 %/%RH was calculated for humidity sensor at frequencies of 1 kHz, 10 kHz, 20 kHz, 30 kHz, and 40 kHz, respectively. The fabrication details of the humidity sensor as well as its capacitive responses for varying humidity levels were analysed and reported in this paper.