An all superantiwetting surface in water–oil–air systems†
Superantiwetting surfaces with contact angles above 150° and sliding angles below 10° for one wetting phase under another medium phase among water, oil, and air have been designed. However, all superantiwetting surfaces that show super-repellence in any two-phase system including six extreme wetting states such as superhydrophobicity, superoleophobicity, underoil superhydrophobicity, underwater superoleophobicity, and underoil and underwater superaerophobicity are extremely rare. Here, we prepare all superantiwetting surfaces by simply spraying a suspension containing titanium dioxide, aluminum phosphate, and perfluorosilane on substrates. In a broad sense, the all superantiwetting state can be extended to polar liquid–nonpolar liquid–air systems. Thus, the prepared surfaces realize high-efficiency on-demand separation of immiscible organic liquids. This discovery opens up the possibility of multiple extreme wetting surfaces even involving a wide range of organic liquids.