This study demonstrates the fabrication of hierarchical surfaces with super -repellency even for low-surface-tension liquids, including octane (surface tension of 21.7 mN m −1 ). Dual-pore surfaces were prepared by a combination of practical wet processes on an alumin ium substrate: chemical etching, anodizing, and organic monolayer coating. Th e size of the larger pores formed by the chemical etching of aluminium is controlled by the concentration of HCl in the CuCl 2 /HCl etching solution. The etched aluminium is then anodized to introduce nanopores, followed by a pore-widening treatment that controls the nanopore size and porosity. The repellency for low-surface-tension liquids is enhanced by increasing the size of the larger pores as well as the porosity of the walls of the larger pores in this dual-pore morphology. Under optimized morphology with a fluoroalkyl-phosphate monolayer coating, an advancing contact angle close to 160º, a contact angle hysteresis of less than 5º and a sliding angle of 10º is achieved even for octane.

This paper reports the formation of hierarchically structured aluminum mesh by a combination of simple chemical etching and anodizing. The former introduced micrometer-sized etch pits, and the latter produced nanopores of the order of 10 nm on the mesh with 150 μm mesh openings. Coating the mesh with a monolayer of fluoroalkyl phosphate made the surface superoleophobic to practically any liquid, including hexane with a surface tension as low as 18.4 mN m −1 . The hierarchical triple ∼100 μm/∼1 μm/∼10 nm pore surface morphology improved the superoleophobicity compared to the dual ∼100 μm/∼10 nm and ∼1 μm/∼10 nm pore structures. When the aluminum mesh was coated with a fluorine-free alkylphosphate monolayer, the surface was superhydrophobic, but superoleophilic. The noncoated aluminum mesh was superhydrophilic and superoleophilic with a liquid contact angle close to 0°. Using the aluminum mesh with an alkylphosphate coating, a water/ oil mixture was successfully separated by allowing only the oil to pass through the mesh. In addition, the mixture was separated using noncoated mesh wetted with water, since oil was not able to pass through the mesh in this case.

Highlights ・The CeO-coating is formed on Type 304 stainless steel by anodic deposition. ・The hydrophilic CeO 2 surface is transformed to hydrophobic during air exposure. ・Superhydrophobic CeO 2 surface is obtained on hierarchically rough substrate. ・Superhydrophobic CeO 2 surface shows self-healing property.

This paper reports rapid self‐healing on superoleophobic hierarchically porous aluminum surfaces within 1 h even at room temperature. This self‐healing surface is prepared by infiltration of a liquid fluoroalkylsilane (FAS) coating into the substrate pores. The FAS‐infiltrated dual‐pore superoleophobic surface becomes superoleophilic after oxygen plasma treatment due to the damage done to the organic coating. However, the superoleophobicity is completely recovered by exposure to normal atmosphere at room temperature, and this rapid self‐healing is repeatable. The FAS liquid appears to coat the nanopore walls, rather than filling the nanopores. The high wettability of FAS on surfaces induces the rapid recoating of the plasma‐damaged surface, contributing to the self‐healing of the superoleophobicity.

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