Thermo-flow and temperature sensing behaviour of graphene based on surface heat convection

This letter studies the surface heat convection of thin graphene sheets and the application of graphene wires as nanoscale flow and temperature sensors. Graphene wires with relatively large length-to-width ratios were designed and fabricated using bi- and few-layer graphene sheets. Prior to testing, the devices were packaged in a microfluidic chamber with capillary tubes as upstream and downstream connections to minimise environmental interference. The thermal inertia of the graphene wire was studied at 70°C and the flow sensing behaviour of the device was characterised by monitoring normalised resistance changes at different flow rates. The authors experimental results demonstrated the negative temperature coefficients of the bi- and few-layer graphene films. Moreover, the flow sensing resolutions of ~ 0.07 l/min and 0.1 l/min were achieved from the bi- and few-layer graphene hot wires, respectively. The temperature sensing behaviour of the graphene thermistor was studied in a small temperature range from room temperature to 80°C. The larger negative temperature coefficient of the bi-layer graphene resulted in a higher sensing response than the few-layer one.