Modeling the Retention of Water Droplets on Topographically-Modified, Micro-Grooved Aluminum

In this research, a method for fabricating controlled micro-scale, anisotropic topographical features on aluminum is described for the purpose of exploiting those features to affect the surface wettability. Experimental data have shown that droplets placed on these micro-grooved aluminum surfaces using a micro-syringe exhibit an increased apparent contact angle, and for droplets condensed on these etched surfaces, up to a 50% reduction in the volume needed for the onset of droplet sliding is manifest. No chemical surface treatment is necessary to achieve this water repellency; it is accomplished solely by the anisotropic surface morphology that manipulates droplet geometry and creates and exploits discontinuities in the three-phase contact line. In an effort to provide guidance for the development of these surfaces, a mechanistic model for droplet retention on micro-grooved aluminum surfaces will also be presented. This work will show that current models, tacitly based on an assumption of isotropic wetting, do not provide reliable prediction of water retention on these new surfaces.