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

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 mu m 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. In applications sensitive to ice formation, surfaces delaying frosting passively are crucial. The innovative approach involves self-ejection of individual condensation droplets from hydrophobic microcones, frustrating ice-bridging and achieving a frost velocity below the current limits. This design ensures a controlled droplet size distribution, slow frost propagation and minimal frost coverage, ideal for aeronautics and thermal machines.image