Condensation and Wetting Behavior on Surfaces With Micro-Structures: Super-Hydrophobic and Super-Hydrophilic

Recently it has become possible to achieve radical manipulation of surface wettability, and wettability is known to play a key role in the retention of condensate and frost melt on heat exchanger surfaces. In this paper we present a review of methods to produce such surfaces, and we describe a super-hydrophobic surface, with a contact angle of 148°, created in our lab. We describe surfaces with micro-posts and micro-grooves, and the wetting behavior of these surfaces and early growth of condensate is studied experimentally. The rapid spreading of droplets is observed for surfaces with silicon grooves and posts while an anisotropic wetting is observed for the droplets on the surface with SU8 grooves. The results of our microscopic observations show that condensate drops group around the posts on the super-hydrophobic surface, but condensate forms a thin film on the surface with silicon posts. Condesnate is drawn into the grooves mainly by surface tension.on the anisotropic surface.