Enhanced efficiency of superhydrophobic coatings: A comparative analysis between dip and spray techniques using octadecyltrichlorosilane

Background

Superhydrophobic surfaces with water contact angles (WCAs) of 150° or higher have drawn significant attention due to their exceptional water-repellent properties. Despite their potential, the fabrication of such surfaces is often hindered by complex, multi-step processes. This study presents a facile, scalable approach for generating superhydrophobic coatings using an octadecyltrichlorosilane (OTS) and ethanol (EtOH) mixture, all under ambient conditions.

Methods

Glass substrates were coated using both spray and dip coating techniques, followed by a detailed comparative analysis of the resulting surface properties. The same coating solution was then applied to aluminium, copper, plastic, and paper substrates, using both spray and dip methods.

Significant Findings

Coatings produced via spraying exhibited significantly higher surface roughness and achieved superhydrophobicity after just 11 cycles, an outcome unattainable by the dipping method, even with additional cycles. The OTS concentration and the number of coating cycles were key factors influencing surface morphology and topography. Notably, the aging of the OTS coating solution was found to affect the hydrophobicity and transparency of the substrate adversely. After just 3 h of aging, WCAs dropped below the superhydrophobic threshold, and light transmittance decreased to about 4 %. Despite differences in substrate properties, the spray coating method successfully conferred surface superhydrophobicity to a variety of materials.