Fabrication of inverse-tapered structure remains as a problem in the fabrication of oleophobic surface mostly due to the complications and the high cost of processes. In this paper, we propose a simple and low-cost fabrication method of inverse-tapered structured oleophobic surface using micromolding in capillaries (MIMIC) and microtransfer molding followed by MEMS processes. Silicon wafer molds for the formation of inverse-tapered structure were made using MEMS processes such as photolithography and anisotropic KOH etching of silicon wafer. The geometry of structure could be changed by controlling the etching depth of the silicon wafer mold. After covering the surface of the mold using flat UV tape, the formed space between mold and UV tape was filled with pre-cured PDMS by capillary force and then cured in oven. The tapered structure on UV tape was transferred and bonded to glass wafer by O₂ plasma treatment. The fabricated inverse-tapered structure was coated with a fluoroalkylsilane monolayer to reduce its surface energy. The wetting behaviors were investigated by the contact angle (CA) measurement of hexadecane droplets. This study demonstrates that an inversetapered structure can be fabricated on a substrate using micromolding in capillaries and microtransfer molding, whose surface shows the superoleophobicity.

In this study, we developed a convenient method to achieve superoleophobic surfaces on zinc substrates by using anodization and self-assembled monolayer coating, and to facilitate the fabrication of superoleophobic surfaces having reentrant structures, even for lower surface tension liquids than 30 mN/m- including hexadecane (γ = 27.5 mN/m). The liquid repellency of the structured surface was validated through observable experimental results; contact angle measurement. The optimal anodizing condition was determined as a critical parameter in building the superoleophobicity. The re-entrant had nanowire/microball structures formed by anodization with a high voltage. Under an optimized morphology by re-entrant structures with fluorination treatment, the contact angle over 150o is achieved, even for hexadecane.