Transparent and Robust Superhydrophobic Coatings for High-Fidelity Signal Transmission in Atmospheric Light Detection and Ranging Windows.

Abstract

Atmospheric light detection and ranging (LiDAR) systems are crucial for environmental monitoring, especially in air quality assessment. However, water droplets or contaminants on LiDAR protective windows could severely degrade signal transmission and undermine the monitoring precision. Superhydrophobic coatings with excellent transparency, mechanochemical robustness, and weather resistance are expected to solve this issue. Here, we report the design of such an application-oriented superhydrophobic coating to ensure high-fidelity signal transmission. We used tetraethylorthosilicate (TEOS) and carbon soot (CS) to construct a composite rough structure on polydimethylsiloxane (PDMS) resin-loaded glass while restoring transparency through high-temperature annealing. High temperature removed CS, thus inducing the rearrangement of the rough structure and forming a dense, robust, three-dimensional, cross-linked dendritic structure. 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane (PTES) then imparted low surface energy to the coating and reinforced the dendritic structure. Therefore, the resultant PDMS-TEOS/F-CS(O) coating shows excellent superhydrophobicity (water contact angle (WCA) = 165.04° and sliding angle (SA) = 0.47°), outstanding light transmittance (92.4%), mechanochemical robustness, and weather resistance. The coating can retain its surface properties after sandpaper abrasion (2400 cm), sand impact (1200 g), knife scratch test, and acid/alkali immersion for 120 h. Even after enduring various weatherability tests, including water flow impact (3 h), shower impact (24 h), -20 °C/50 °C exposure (40 days), intense UV radiation (60 days), and real outdoor exposure (90 days), the coating remains excellently superhydrophobic. Remarkably, when integrated into an atmospheric particulate matter LiDAR window, the coating successfully ensures high-fidelity signal transmission by preventing the window from being contaminated. Overall, this study provides new insights into the fabrication of LiDAR windows with a durable superhydrophobicity.