Prediction of Contact Angle for Oriented Hydrophobic Surface and Experimental Verification by Micro-Milling

The rectangular microgroove surfaces have obvious anisotropy, which can control the movement of water droplets in parallel and vertical directions. Based on such a property, anisotropic functional surfaces are expected to have potential applications in the fields of droplet-oriented delivery and microfluidics. Micro-milling can accurately adjust the dimension of microstructures, which is convenient to explore the optimal micro-structural parameters. In this study, the non-composite and composite state prediction models of contact angle on the oriented hydrophobic surface were established based on minimum Gibbs free energy, and the effect of micro-structural dimension parameters on contact angle was investigated. Then, the rectangular microgroove structure on 316 L stainless steel was prepared using micro-milling. The composite state prediction model of contact angle was found to be more consistent with the actual situation, and reducing the width of the convex platform was beneficial to increasing the contact angle. In particular, the contact angle in the parallel direction reached 146.5° when the width of the convex platform was 60 μm, and the accuracy of the prediction model was 98.4%. The proposed prediction models of contact angle provide a theoretical basis for designing and preparing oriented hydrophobic surfaces.