The optimized SAW humidity sensor with nanofilms of graphene oxide

Characterization of graphene oxide nanofilms obtained by the SAW atomization

“…The atomization process took 1-2 s and water evaporation took about a minute. More detailed description of the SAW atomization technique can be found elsewhere [4,7].…”

“…We monitored the kinetics of evaporation of water molecules from the surface of the liquid sample of saturated salt into the enclosed chamber with initially zero relative humidity. The details of these experiments can be found elsewhere [4,9]. Typical experimental differential frequency response of the sensor ) (t f , shown in the figure 8, was approximated by the multi-exponent equation, which corresponds to N adsorption processes…”

“…All these methods use large volumes of suspensions and have their limitations: spin coating, for example, cannot be applied for rectangular substrates, or very small substrates, or for the patterned film deposition. The drawback of dip coating 4 To whom any correspondence should be addressed and spray coating is that the obtained films are relatively thick. Also, evaporation of thick water layers can cause a significant non-uniformity of the final thickness of a film ("coffee-ring" effect).…”

“…For that reason some types of the SAW sensors-gas, biological, or humidity sensors-must have special coatings deposited onto the SAW propagation path between the interdigital transducers (IDTs) of the device. For example, thin films of polyvinyl alcohol (PVA) [2,3] and graphene oxide (GO) [4] find use as sensitive coatings for humidity sensors.…”

“…To obtain thin GO films, we used the SAW atomization technique [4,8]. The idea of this method is to produce a very fine spray/aerosol from a single micro or submicroliter droplet of GO aqueous suspension and deposit it onto the surface of a substrate, where it will form a very thin wet layer.…”