Steady-state stability improvement of reduced graphene oxide thermo behavior via polymer film encapsulation

Abstract

We report steady-state stability improvement of reduced graphene oxide (rGO) thermo behavior via polyimide (PI) film encapsulation. A temperature sensor was made of rGO produced by photo-thermal laser irradiation of graphene oxide (GO) and showed a negative thermal coefficient of resistance (TCR). However, when the rGO-based temperature sensor was exposed to air, the resistance increased owing to the attachment of an oxygen-containing molecule, particularly water molecules on the surface of the rGO. To solve this issue, the surface of rGO was encapsulated with a PI film, and the encapsulated temperature sensor showed significant stable resistance characteristics at 25 °C and 40% relative humidity for seven days compared to bare rGO while retaining the sensitivity of the sensor. Scanning electron microscopy images confirmed that most of the rGO surface was separated from the encapsulated PI layer, and the morphology of the rGO surface remained intact, thus maintaining the temperature variation properties without being affected by external humidity. In addition, the PI-encapsulated rGO produced a thermoacoustic sound of 78 dB at 5 kHz performance after 30 days.