Ice‐Bridging Frustration by Self‐Ejection of Single Droplets Results in Superior Anti‐Frosting Surfaces

Abstract

Abstract Surfaces capable of delaying the frosting passively and facilitating its removal are highly desirable in fields where ice introduces inefficiencies and risks. Coalescence‐induced condensation droplets jumping (CICDJ), enabled on highly hydrophobic surfaces, is already exploited to slow down the frosting but it is insufficient to completely eliminate the propagation by ice‐bridging. The study shows here how the self‐ejection of single condensation droplets can fully frustrate all the ice bridges, resulting in a frost velocity lower than 0.5 µm s−1 and thus falling below the current limits of passive surfaces. Arrays of truncated microcones, covered by uniformly hydrophobic nanostructures, enable individual condensation droplets to grow and self‐propel toward the top of the microstructures and then to self‐eject once a precise volume is reached. The independency of self‐ejection on the neighbor droplets allows a fine control of the droplets size and distance distributions and thus the ice‐bridging frustration. The truncated microcones with the smallest heads area fraction maximize the percentage of self‐ejecting droplets and minimize the frost velocity. The ice bridges frustration also implies a small frost area coverage, highly desirable in aeronautics and thermal machines.

Keywords

• anti‐frosting
• condensation frosting
• droplet jumping
• micro and nano fabrication
• self‐ejection