Sub-second humidity sensing using surface acoustic waves in electrospray-deposited carbon nanofiber and reduced graphene oxide structures

Propagation of surface acoustic waves in lithium niobate crystals with carbon nanofibers or reduced graphene oxide layers deposited by electrospray has been investigated. We show that the ambient air humidity variations affect the phase of the wave noticeably stronger than its amplitude. The response of both phase and amplitude to fast humidity changes is in the sub-second range. The capability of surface acoustic waves of monitoring the fast changes in nano-layer properties for sensing applications has been demonstrated.