Currently, a wide range of materials are being used as barrier coatings for different applications. Among them, polymers and graphene have been the focus of many studies. Polymers are used in numerous industries due to their remarkable properties, including resistance to thermal degradation, resistance to chemical permeation, and good mechanical properties. On the other hand, graphene, a one-atom-thick and two-dimensional material, does not allow the permeation of gases or liquid molecules through its plane; thus, it has been considered one of the promising nanomaterials used in gas and liquid barrier applications and corrosion inhibition coatings.

Superhydrophobic coatings are gaining popularity because of their low maintenance requirements, high durability, and wide range of potential uses. Such coatings, for instance, may provide beneficial resistance to fouling, icing, smear, and corrosion, and can separate oil from water. Therefore, the creation of superhydrophobic materials is a topic of great interest to academics all around the world. In this paper, a spray-coating deposition technique is used to deposit silica nanoparticles on glass while using a sol–gel as a base. The applied coating increased the transmittance to 99% at 600 nm. Water contact angle (WCA) and scanning electron microscopy (SEM) observations of the coated layer’s grade index and induced porousness led to superhydrophobic behavior with a water contact angle that was higher than 158°.

The geometrical dependence of humidity sensors on sensing performance has not been quantitatively outlined. Furthermore, the etching effect on humidity sensors is still elusive due to the difficulty in separating the effects of the geometrical change and etching-induced porosity on the overall performance. Here, we use COMSOL Multiphysics to perform a numerical study of a capacitive graphene oxide (GO) humidity sensor, with emphasis on the dimensions and etching effect on their sensing performance. GO is a useful and promising material in detecting humidity because of its selective superpermeability to water molecules. The mechanism of improved sensing performance of the etched humidity sensors is discussed in terms of the morphological profile and the effective permittivity including the etching-induced porosity effect. Our study shows that as compared to the unetched sensors, isotropic etching achieves the lowest response time of 1.011 s at 15.75% porosity, while vertical etching achieves the highest capacitance sensitivity of 0.106 fF/RH %.

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