Preparation of graphene by circulating supercritical CO2 jet cavitation and its application in flexible sensor films

In this paper, a simple operation, mild condition and no chemical intercalation method for graphene nanosheets (GNs) exfoliating was proposed. By utilizing the zero surface tension of supercritical carbon dioxide (scCO2) and the stable cavitation field generated by cavitation devices, the growth and rupture of cavitation bubbles between graphene layers were induced. The highest concentration of graphene dispersion was 0.723 mg/mL, with about 90% of GNs within 5 layers and about 36.6% of GNs having lateral dimensions greater than 1 mu m, at an intensity ratio of ID/IG of 0.26. The tensile strength of the graphene-TPU composite film reaches 105.9 MPa, and the thermal conductivity can be adjusted by centrifugation speed to meet different requirements, with a maximum value of 20.8 W/(m center dot K) at room temperature. In addition, the test results in cyclic stretching and temperature cycling experiments showed good repeatability, with a maximum sensitivity coefficient (GF) of 17.5. It has been proven that flexible graphene film can respond stably and quickly to input information, and convert it into strong signals for processing, making it an ideal material for pressure and temperature sensors.