Facile preparation of super-oleophobic TiO2/SiO2 composite coatings by spraying method

Re-entrant geometries can effectively trap air pockets, increase air/liquid interface fraction, prevent the penetration of low surface tension organic liquids, and achieve super-oleophobic performance. However, the creation of re-entrant geometries usually involving expensive lithographic tools, or complicated chemical procedures, and cannot be applied on a large scale, such super-oleophobic surfaces are unsuitable for practical application. Constructing hierarchical micro/nanostructure on substrates is a feasible solution to achieve super-oleophobicity through facile spraying method. Herein, we report a super-oleophobic TiO 2 /SiO 2 composite coatings by taking advantage of an exceedingly simple spraying method. The dendritic structures produced by spraying the TiO 2 /SiO 2 mixture play the critical role in obtaining the re-entrant geometry required for oleophobic surface, and the introduction of micron-scale TiO 2 particles and nano-scale SiO 2 particles provide an enough dual-scale rough structure for the coating. The TiO 2 /SiO 2 composite coatings exhibit superior repellence to high and low surface tension liquids as well long-term durability. This design strategy may provide useful guidelines for the fabrication of particle-based spray-coated super-oleophobic surfaces.