Submicron-thick films of graphene oxide and polyvinyl alcohol (PVA) were deposited onto the surface of 160 MHz quartz surface acoustic wave (SAW) delay lines, and manufactured devices were used as humidity sensors. Films were obtained by consecutive atomization of 0.35 μl droplets of 0.33 mg/ml graphene oxide water suspension or 5.00 mg/ml PVA water solution using 25 MHz SAW atomizers. During measurements authors did not observe additional attenuation of the surface acoustic wave propagating along the surface of the sensors, which confirms that deposited films have low thickness and good uniformity. It was shown that SAW quartz humidity sensors with graphene oxide films, PVA thin films and uncoated surface have sensitivity of 1.54 kHz/%RH, 0.47 kHz/%RH and 0.13 kHz/%RH respectively. Sensors with graphene oxide thin films showed the best sensitivity and dynamic response. It was concluded that they can be used as sensitive coatings in humidity sensors for industrial environment.

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a b s t r a c tSymmetric surface acoustic wave (SAW) atomizer was used to deposit graphene oxide (GO) nanofilms from microdroplets of the aqueous GO dispersion onto the surface of the SAW humidity sensors. The sensors with the deposited GO films were tested in a wide range of relative humidity and showed the amplitude of the response in the range of 1-40 kHz sufficient for the majority of applications. The kinetics of the adsorption of water molecules was modeled using the assumption that two independent first order adsorption processes take place. Saturation amplitudes and rate coefficients for both processes were experimentally evaluated using LSQ fitting of the sensor response in the time domain for the films obtained by different number of depositions. The mechanism of the adsorption of water molecules to the GO flakes is proposed and discussed.

A method for the rapid detection of coronaviruses is presented on the example of the transmissible gastroenteritis virus (TGEV) directly in aqueous solutions with different conductivity. An acoustic sensor based on a slot wave in an acoustic delay line was used for the research. The addition of anti-TGEV antibodies (Abs) diluted in an aqueous solution led to a change in the depth and frequency of resonant peaks on the frequency dependence of the insertion loss of the sensor. The difference in the output parameters of the sensor before and after the biological interaction of the TGE virus in solutions with the specific antibodies allows drawing a conclusion about the presence/absence of the studied viruses in the analyzed solution. The possibility for virus detection in aqueous solutions with the conductivity of 1.9–900 μs/cm, as well as in the presence of the foreign viral particles, has been demonstrated. The analysis time did not exceed 10 min.

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