Highly transparent and highly hydrophobic coating for outdoor camera window glass: Fabrication, transparency, and hydrophobicity

•Highly transparent and nearly superhydrophobic surface can be achieved.•The relationship between optical transmittance and etching depth was studied.•Surface roughness-dependent water contact angle and sliding angle were studied. Highly transparent, superhydrophobic coatings are highly desirable for maintaining long-lasting clarity for outdoor camera windows. In this study, the authors present a simple approach to create a wide–range anti-reflective and highly hydrophobic layer on a glass surface. This is accomplished through a hydrothermal alkali etching process combined with a dip-coating process using 1 H, 1 H, 2 H, 2 H-Perfluorooctyltrimethoxysilane (POTS). The sample, etched for 20 h and modified by POTS, exhibiting an average transmittance of 96.5 %, a water contact angle (WCA) of 140° and a sliding angle (SA) of 40°. The results of the water spray experiment indicate this surface exhibits excellent water repellent performance, preventing water droplets larger than 0.01 mm in size. The relationship between optical transmittance and etching depth was thoroughly studied, revealing that an etched depth ranging from 200 nm to 600 nm yields optimal wide-spectrum anti-reflective properties. Furthermore, the influence of surface roughness on apparent WCA and SA was investigated. It was found that root mean square (RMS) roughness can be an effective factor to predict the apparent WCA of a surface, while both the RMS roughness and morphological structure affect the SA.