Facile Fabrication of Graphene Oxide-based Flexible Temperature Sensor and Improving its Humidity Stability

Graphene derivatives and their composites have attracted significant research interest for the development of novel sensors. Optimizing the formulation of graphene-based composites plays a significant role in developing sensors with improved features, such as high sensitivity and humidity stability. In this work, graphene oxide (GO)-based temperature sensors with high sensitivity were developed on a flexible substrate, using a facile fabrication method, and the humidity stability of the sensors was improved by ~58% while maintaining a high sensitivity towards the temperature. GO ink was used as the sensing layer of one temperature sensor (TS1), and a composite of GO and poly(3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS) was used as the sensing layer of another temperature sensor (TS2). The resistive responses of sensors towards varying temperatures ranging from 10 °C to 80 °C were investigated. The temperature sensors showed linear responses, with slopes of -0.98 and -0.69, and correlation coefficients of 0.9994 and 0.998 for TS1 and TS2 temperature sensors, respectively. The temperature coefficient of resistance (TCR) of temperature sensors were calculated as -1.00 and -0.68 %/°C for TS1 and TS2 sensors, respectively. The sensitivity of temperature sensors towards humidity was calculated as 0.107 and 0.045 %/%RH for TS1 and TS2 temperature sensors, respectively. It was observed that adding PEDOT:PSS to GO improves the humidity stability of the temperature sensors by ~58% while maintaining a high TCR.