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

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.