Transparent superhydrophobic surfaces using a spray coating process

One significant maintenance problem and cost associated with solar energy conversion systems is the soiling due to the accumulation of dust and other pollutants. In this work, we describe a scalable approach for applying antisoiling coatings based on superhydrophobic (SH) silica particles using a spray coating process. A large water contact angle (WCA) is one of the characteristics of excellent SH surfaces and because of the low surface energy and low adhesion forces the soiling rate is reduced. Our findings indicate that the WCA depends strongly on the ratio of the polymer binder and the nanoparticles. The nanoparticle surface coverage of the spray coated samples was substantially improved after rinsing with solvent. This process tended to remove large aggregates and excess polymer binder and further increased the WCA by allowing exposure of the functionalized nanoparticles. The durability of the SH coatings was enhanced when the substrate was pretreated with polymer binder and an optimal curing time between 30 and 60 min. The abrasion tests of the SH coatings we report in this study showed that the WCA decreased from similar to 166 degrees to similar to 157 degrees after exposure to 2.6 g of sand. Such coatings will help reduce costs of periodic cleaning of solar energy conversion systems (photovoltaic panels and concentrated solar mirrors).