Effect of surface pattern morphology on inducing superhydrophobicity

Microstructures present on surfaces can change the surface properties of a material. In this study, various patterns – and arrangements of those patterns in different shapes – were designed in order to analyze the associated differences in surface properties related to superhydrophobicity. We categorized these surface microstructures into three different groups of patterns: (1) pillar, (2) wall, and (3) wall–pillar; and four shapes of pattern arrangement: (1) triangular, (2) square, (3) hexagonal, and (4) octagonal. Pillar-pattern microstructures exhibit a small water-contact area and the wall-pattern structures contain interconnected pillars, and as a result, an air layer is trapped when the structure comes into contact with water. Wall–pillar pattern microstructures exhibit characteristics of both walls and pillars. For the different patterns, Si master molds were used to fabricate structures from a UV-curable polyurethane acrylate resin. Measured contact angles for 5 μl water droplets on the patterned surfaces were compared according to shape, pattern, and pitch, and the pattern exhibiting the highest contact angle was further investigated.