The jumping droplet condensation phenomenon on the superhydrophobic surface can significantly enhance the energy efficiency of heat exchange devices. However, such a preferred regime (Cassie) easily collapses under high heat flux conditions owing to its transiting to unwanted pinning mode (Wenzel) due to the relatively large feature size of nanostructures compared to the critical nucleation radius (typically &lt; 10 nm). Despite rapid progress, it remains an elusive goal to suppress the nucleation-induced droplet-wetting transition on superhydrophobic surfaces.<br/>Herein, we report the rational design of nano-hierarchical topological surfaces based on branched nanorods (b-NR) to preserve jumping droplet condensation and inhibit its transition from the Cassie state. Systematic experimental investigations and careful modeling demonstrated that this nano-hierarchical structure could spontaneously generate an outward Laplace capillary pressure gradient, pushing condensate nuclei away from the surface. As a result, a stable Cassie state of droplets was sustained on the b-NR surface even under high heat flux, resulting in more than 60% higher heat transfer coefficient than the conventional one-tier nanorods (NR) surface. These findings broaden the horizon of designing surfaces to fundamentally mitigate the nucleation-induced wetting transition on superhydrophobic surfaces, which provides new opportunities for wide applications, including water harvesting, anti-icing, and thermal management system.

Minimizing condensate adhesion for heat transfer enhancement via nano-hierarchical structure

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