A Highly Transparent and Durable Superhydrophobic Coating for Long-Term Underwater Optical Applications

Highly transparent, long-term durable superhydrophobic coatings are expected to solve the signal attenuation issue of optical monitoring sensors in harsh water environments. However, achieving both excellent underwater environmental durability and superior optical transparency remains a challenge for artificial superhydrophobic coatings. Here, this study reports an underwater application-oriented epoxy resin/perfluorooctyltriethoxysilane-candle soot (oxidized) (EP/F-CS(O)) coating with all of these merits, prepared by thermally depositing candle soot and removing carbon black under high-temperature annealing. The coating shows excellent static and dynamic superhydrophobicity (ultrahigh water contact angle (CA) = 160.1° and ultralow sliding angle (SA) = 0.67°), outstanding transparency (89.41%), and mechanochemical stability. Most importantly, this coating can maintain exceptional durability in various harsh water environments for 30 days. Furthermore, the coating is successfully applied to underwater optical sensors, effectively mitigating pollutant accumulation and signal attenuation. After continuous monitoring of the lake water for 30 days, the attenuation of the monitoring signals of the coated sensor is only 0.018 times that of the blank sensor. The coating can successfully reduce the signal attenuation of the sensor by 98.2%. This indicates that the EP/F-CS(O) coating can significantly improve the monitoring accuracy and extend the service life of the optical sensors. With these advantages, the superhydrophobic coating shows great application potential and market prospects in real-water optical monitoring fields.