Abstract
This study investigates the impact of combined texturing by micromachining and chemical functionalization on the wetting behavior and water condensation of a metallic surface. The transition from the Wenzel to Cassie-Baxter or impregnated Cassie-Baxter regimes was unveiled. Initially, grooved stainless steel 304 specimens displayed hydrophobic wetting in the Wenzel mode. The chemical functionalization with silane triggered a remarkable shift that was not observed in non-textured by micromachining samples. Thus contact angles surged, facilitating a transition to the Cassie-Baxter state for directional canal specimens and the impregnated Cassie-Baxter state for those with pyramidal patterns. Roll-off angle experiments showcased distinct behavior among specimens featuring canals or pyramidal structures. Specimens with canals exhibited notably lower roll-off angles compared to both flat surfaces and those with pyramidal patterns. Notably, the orientation of canals influenced these angles, with vertically aligned canals demonstrating reduced roll-off angles. In humid environments, micro-machined surfaces exhibited superior water condensation capabilities compared to untreated flat SS304 surfaces. Remarkably, chemically functionalized grooved specimens presented larger condensate droplet diameters than flat surfaces. Consequently a remarkable enhancement in water condensation and a 7 fold higher latent heat transfer coefficient is reported.