Humidity sensor based on multi-layer graphene (MLG) integrated onto a micro-hotplate (MHP)

This work demonstrates a humidity sensor based on two multi-layered graphene (MLG) strips monolithically integrated onto a micro-hotplate (MHP). A transfer-free approach was adopted to release the graphene from the catalyst to reduce device variations and ensure scalability. The sensing performance of the device was tested by exposing the device to humidity levels in the range of 10% to 84% of relative humidity (RH). Both MLG strips present a linear response over this range. The micro-heater implementation is vital to fully desorb water molecules from the MLG surface. The micro-heater was powered with 31 mW to reach 140°C in the MHP zone. The sensitivity of the devices is of the order of 1000 pp/RH[%]. The developed device aims at providing a robust and reliable gas sensors platform based on MLG.