Superhydrophobic-Like Complete Rebound of Impacting Water Droplets on a Smooth Oleic- Acid-Coated Phenyl-Silica Surface
Year: 2026
Type: preprint
Abstract: We report impact-induced water-droplet rebound on a nanoscopically smooth phenyl-silica surface bearing an oleic-acid liquid layer with a nominal cast-equivalent thickness of ≈1 µm, retained on the substrate through interactions previously attributed to COOH–π association. High-speed imaging (5000 fps) of 10 µL water droplets resolves complete rebound at all sampled conditions from Weber number (𝑊𝑒) = 0.69 to 3.99 and partial rebound with satellite ejection at 𝑊𝑒 = 6.03 and 7.14; a near-zero-impact reference showed no liftoff during the recorded interval. The apex-based rebound proxy (𝑒apex) varied nonmonotonically, reaching 0.72 ± 0.02, whereas the apparent residence time of 16–21 ms showed no systematic dependence on 𝑊𝑒 and remained close to the inertial-capillary timescale. These kinematics are comparable to rebound regimes reported for smooth solids and liquid interfaces. Entrained-gas-film dynamics and the response of the oleic-acid layer are discussed as mechanistic hypotheses, while neither gas-film continuity nor lubricant redistribution was directly resolved. The results establish rapid impact-induced water shedding on a smooth, texture-free oleic-acid-coated interface and motivate future tests of lubricant retention under repeated water impact.
Source: ChemRxiv
Language: English
Subfield: Surfaces, Coatings and Films
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7211961272