Low operating voltage carbon-graphene hybrid e-textile for temperature sensing.

Graphene-coated polypropylene (PP) textile fibres are presented for their use as temperature sensors. These temperature sensors show negative thermal coefficient of resistance (TCR) in a range between 30 and 45°C with good sensitivity and reliability, and can operate at voltages as low as 1 V. The analysis of the transient response of temperature on resistance of different types of graphene produced by chemical vapour deposition (CVD) and shear exfoliation of graphite (SEG), shows that trilayer graphene (TLG) grown on copper by CVD displays better sensitivity due to the better thickness uniformity of the film, and that carbon paste provides good contact for the measurements. Along with high sensitivity, TLG on PP shows not only the best response, but also better transparency, mechanical stability and washability compared to SEG. Temperature dependent Raman analysis reveals that temperature has no significant effect on the peak frequency of PP and expected effect on graphene in the demostrated temperature range. The presented results demonstrate that these flexible, lightweight temperature sensors based on TLG with negative TCR can be easily integrated in fabrics.