Condensation-induced roughness controls non-contact bouncing of hot drops

Guillaume Deschasaux; Sakura Torii; Jiaxing Shen; Yuki Serata; Pritam Kumar Roy; Mizuki Tenjimbayashi; Timothée Mouterde

doi:10.1016/j.newton.2026.100587

Journal article Condensation-induced roughness controls non-contact bouncing of hot drops

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Guillaume Deschasaux, Sakura Torii, Jiaxing Shen, Yuki Serata, Pritam Kumar Roy, Mizuki Tenjimbayashi, Timothée Mouterde. Condensation-induced roughness controls non-contact bouncing of hot drops. Newton. 2026, (), 100587. https://doi.org/10.1016/j.newton.2026.100587

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Droplets readily bounce on hydrophobic microtextures as they trap an air layer between liquid and solid, limiting contact to the structure tops and thereby reducing adhesion and pinning. For hot droplets condensation can fill the texture, forming liquid bridges that limit or prevent bouncing. Remarkably, bouncing can also occur on hydrophilic or wet surfaces when a thin gas layer dynamically cushions the droplet impact without any contact with the substrate. In this non-contact regime, the interplay between hot-droplet impacts, condensation, and the transient gas cushion remains to be clarified. Here, we investigate the impact of hot water droplets on lubricant-infused surfaces initially at room temperature. Using high-speed imaging and interferometry, we discover that the maximum contactless bouncing velocity decreases with increasing temperature difference ∆T between the drop and the surface. High-speed interferometry reveals that the transition is governed by rapid condensation growth (~ 1 ms) on the lubricant layer, which generates a liquid roughness that triggers the contact between the droplet and the substrate. This phenomenon vanishes for hot silicone oil droplets due to their low volatility. We develop a minimal model coupling condensation dynamics and thermal transfer, leading to a scaling law that quantitatively predicts both the critical bouncing velocity and the condensation bridging time. The model shows that the transition depends on ΔT and the substrate thermal properties, providing a predictive framework for hot-drop impacts in the non-contact bouncing regime.

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