Laser-induced graphene on a quartz crystal microbalance for humidity sensing

In this study, a simple method for synthesizing graphene layer directly on a quartz crystal microbalance (QCM) using a laser was developed. This laser-induced graphene (LIG) was used for sensing surface to simultaneously measure changes in the adsorbed mass, film stiffness, and electrical resistance during water adsorption. The developed LIG-QCM is convenient because its fabrication process is free of any tedious masking and vacuuming steps. A thin layer of polyimide (PI) film was spin-coated on one side of a quartz crystal microresonator, and interdigitated electrodes (IDE) were patterned on the PI surface using a laser engraver. The adsorption of water molecules on the sensing surface induced changes in mass, stiffness, and electrical conductivity, which were measured from the changes in resonance frequency, Q factor of the quartz crystal, and electrical resistance, respectively. The results indicated that the developed sensor could be a humidity sensing platform using LIG.