A High-Performance\nSurface Acoustic Wave Humidity\nSensor with Uniform Multiwrinkled Graphene Oxide Film

Humidity sensors were widely used in Internet of Things\n(IoT) applications.\nAccording to medical respiration monitoring, noncontact sensing, and\nhuman–computer interface requirements, fast response and high\nrepeatability are important for efficient and precise signal acquisition.\nPrevious research works mainly focus on sensitivity improvement with\nthe scarification of response time, stability, and repeatability.\nIn this paper, we proposed the surface acoustic wave (SAW) humidity\nsensors with comprehensive performance using the uniform multiwrinkled\ngraphene oxide (GO) films as the sensing material obtained by vacuum\nfiltration and liquid phase transfer method. The multiwrinkled GO\nfilms offered controllable thickness (thin to 29 nm), uniform wafer-level\nfabrication (2 in.), and abundant wrinkle, making them become effective\nsensitive films for SAW humidity sensors due to numerous adsorption\nsites and transfer channels for water molecules. The experimental\nresults showed that the sensors can obtain high sensitivity (10.5\nkHz/RH%@60 nm thick film), ultrafast response (∼45 ms), good\nstability (variation amplitude ∼0.1%), repeatability (variation\namplitude ∼1%), and wafer-level fabrication capability demonstrating\ntheir practical applications for medical respiration monitoring, noncontact\nsensing, and human–computer interface.