Fabrication of superoleophobic surfaces by mask-assisted electrospray

Electrospraying technique has been demonstrated to fabricate superhydrophobic surfaces with random hierarchical roughness. Yet, it has never been employed to generate superoleophobic surfaces with patterned multiscale roughness. Here, we report a versatile approach to fabricate superoleophobic surfaces with patterned multiscale roughness using a mask-assisted electrospray technique. Superoleophobic surfaces with random hierarchical roughness by conventional electrospray without mask were also investigated for comparison purposes. Surfaces with patterned multiscale roughness were obtained by focusing the electrosprayed deposition through a mesh mask, followed by overlaying a random hierarchical roughness of electrosprayed SiO2. All the textured surfaces were treated with a low surface energy fluoropolymer to render superhydrophobicity and superoleophobicity. Superior repellency against water and hexadecane ( 27.5 mN/m) has been demonstrated on the surfaces with random hierarchical roughness and patterned multiscale roughness ( contact angles of similar to 170 degrees and sliding angles of less than 1 degrees). On the random hierarchical surfaces, the intrinsic re-entrant and multi-tier overhang structures in the SiO2 agglomerates enable non-wetting of low surface tension liquids. While on the surfaces with patterned roughness, the dome shape of micropillars plays a critical role in enabling superoleophobicity. The electric field focusing effect exerted by the mask is verified by COMSOL Multiphysics simulation. (C) 2016 Elsevier B. V. All rights reserved.