Molecular Dynamics Simulation and Experimental Validation of Nanoscale Droplet Wetting and Anti-Icing Performance on OTS Self-Assembled Monolayers

This study explores the performance of octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) coatings on SiO₂ substrates through molecular dynamics (MD) simulations and experimental validations. MD simulations at 300 K investigated the molecular packing, wettability, and droplet dynamics of OTS SAMs across varying coverage densities (0.18 to 3.48 molecules nm^-2). Results indicate that monolayer thickness increases from 0.3 to 2.4 nm with coverage density, while contact angles rise from 0° to 132.7°, with a peak at 125.2° due to surface roughness of 0.262 nm at 1.80 molecules nm^-2. Rolling friction decreases as droplet velocity rises from 4.894 to 41.291 m/s, and self-driven droplet jumping at medium and high coverage enhances self-cleaning. Experimentally, OTS-coated wind turbine blade composite samples delayed icing to 649 s and complete icing to 725 s at -10 °C, compared to 12 and 17 s for SiO₂ hydrophilic coatings, and 92 and 121 s for uncoated surfaces, attributed to reduced contact area and low surface energy. Deicing tests showed OTS coatings achieve ice detachment in 58 s on tilted surfaces via a lubricating water layer, despite longer melting times of 215 s on horizontal surfaces. These findings highlight OTS SAMs' superior hydrophobicity, low friction, and anti-icing/deicing performance, offering potential for high-altitude engineering applications.