Graphene-based textile fibre sensors

Abstract

The challenges of conventional wearable technology have been overcome to a vast extent by the rapid strides in flexible technology. However, the integration of flexible devices in the textile industry still includes challenges like the heaviness and rigidity of electronic components, lack of washability, and high operating power. In this thesis, these challenges have been addressed with the fabrication of textile-based devices consisting of lightweight, flexible, washable, and bendable materials. Here, graphene-coated monofilament polypropylene (PP) textile fibres have been presented for their use as textile-based temperature and humidity sensors. A detailed analysis of the transient response of temperature and humidity on the resistance of different types of graphene-coated fibres is presented. These include chemical vapour deposition (CVD) of graphene and graphene produced from the shear exfoliation of graphite (SEG). Trilayer graphene (TLG) grown on copper by CVD along with carbon paste as contacts display better sensitivity and reliability in response to temperature. These TLGsensors show a negative thermal coefficient of resistance (TCR) in the human body temperature range of 30-45 °C. The TLG-coated PP fibres also show better mechanical stability, washability, and transparency as compared with SEG-coated PP fibres. The TLG and SEG-based sensors show an increase and decrease in conductivity with the increase in humidity levels, respectively, with TLG exhibiting faster response and recovery than a commercial humidity sensor. The demonstrated textile-based sensors can function in operating voltages as low as 0.5 V, suggesting low operating power applications. The presented results demonstrate flexible and lightweight temperature and humidity sensors which can be used to continuous monitoring of temperature and humidity levels and can be seamlessly integrated into most of the textile-based applications especially clothing or upholstery with no heavy, fragile, or toxic materials and components involved in the fabrication process.