anisotropic wettability, surface tension gradient, water droplet, contact angle, condensate carryover
This paper presents a novel method for patterning metal fin surfaces used in HVAC&R applications to mitigate problems associated with condensate retention. In this work, metallic surfaces are patterned to promote water droplet migration towards a specified region acting as a central drainage conduit. The surfaces were fabricated using photolithography, physical vapor deposition, and a surface-specific chemical coating and then characterized using spray (fine mist) testing and small droplet (2-10 μL) injection via microsyringe. In this study, we have also analyzed the effect of the chemical treatment on the observed wettability change (i.e. the degree of transformation of our surfaces from hydrophilic to hydrophobic). The impact of surface tension gradients was also explored by analyzing the deformation and asymmetry of droplets on such surfaces. Results from these tests have shown a significant (30o - 40o) increase in the static contact angle and severe deformation of droplets due to these surface gradient patterns on the surface. These preliminary results suggest that micro-structural patterning could be used to help reduce condensate retention on metallic fins.