Research On The Wettability Of Two Dimensional Microstructured Surfaces

Wettability is an important characteristic of solid surface. Wettability phenomenon not onlyaffects various life activities of animals and plants in the nature, but also plays an important role tothe human life and production. Because the surface microstructure has great influence to thematerial’s wettability, this paper makes a study on the influencing mechanism of the surfacemicrostructure to the wettability of solid surface.This paper use hexagonal close packed hemi-spheres structure as the research model, analyzesthe effect of surface microstructure to the wettability of solid surface from the intrinsic hydrophilicand intrinsic hydrophobic aspects. For intrinsic hydrophilic material, the principle of minimizationof Gibbs free energy is employed to make a analysis on contact status between solid and liquid onthe material with hexagonal close packed hemi-spheres structure. Analysis shows that the droplet isfull access to the materials’ surface. The apparent contact angle can approach0°when the intrinsiccontact angle smaller than58°.Because of the misfit between the experimental results and theconclusion, Further analysis shows that the droplet will have happened to spread when thematerials’ intrinsic contact angle is smaller than74°.The Wenzel model will not be fit and ananalytical expression of contact angle between solid and liquid In the diffusion condition weregiven. For intrinsic hydrophobic material, the relationship between the wettability and parameters ofhemisphere surface has been researched from the solid-liquid contact angle in Wenzel model andCassie model of rough surface. The result indicates that the apparent contact angle increased withthe interior angle of rhombic unit and the ratio of the diameter of the hemisphere to the distancebetween the adjacent hemispheres. The stable condition of hemisphere surface has been given basedon the principle that the bigger the difference of potential energy between Cassie model and Wenzelmodel is the more stable the Cassie model is, that is the ratio of the diameter of the hemisphere tothe distance between the adjacent hemispheres equals1and interior angle of rhombic unit is60°.Finally, an bowl microstructure surface has been researched in this thesis. Research shows that thebowl structure is better for Weak hydrophobic material than the hemisphere structure with samestructural parameters.