Scalable Hierarchical Structuring Enables Robust Non-Wetting Condensation and Anti-Frosting on Stainless Steel.

Scalable fabrication of surface morphologies with sufficiently high energy barriers remains a key limitation in achieving stable non-wetting condensation on stainless steel, as its chemical resilience makes controlled surface structuring challenging. Here, we leverage the intrinsic microstructural features of additively manufactured 316L stainless steel to generate dense microneedle arrays, further decorated with nanostructures to enhance wetting resistance and enable sustained coalescence-induced droplet jumping. The engineered surface maintains stable droplet removal under pure vapor conditions, achieving a 2.5-3.7 X enhancement in heat transfer coefficient compared to filmwise condensation, across a subcooling range of 4.1 to 11.3 K. Notably, strong resistance to wetting transitions is observed across a wide range of supersaturation conditions during a continuous 20 h test. In addition, frosting is significantly delayed by suppressing ice nucleation and propagation, retaining approximately 60% frost-free area after 180 min at -10 °C and 50% frost-free area after 100 min at -13 °C whereas the untreated surface is fully covered by frost within the first 10 to 30 min. This work establishes a scalable strategy for stabilizing non-wetting condensation on stainless steel, enabling improved thermal performance and expanding the application space of additively manufactured metals.