The design of underwater superoleophobic Ni/NiO microstructures with tunable oil adhesion.

Controlling oil adhesion in water is a fundamental issue in many practical applications for surfaces. Currently, almost all studies on underwater oil adhesion control are concentrated on regulating surface chemistry on polymer surfaces, and structure-dependent underwater oil adhesion is still rare, especially on inorganic materials. Herein, we report a series of underwater superoleophobic Ni/NiO surfaces with controlled oil adhesions by combining electro-deposition and heating techniques. The adhesive forces between an oil droplet and the surfaces can be adjusted from an extremely low (less than 1 μN) to a very high value (about 60 μN), and the tunable effect can be attributed to different wetting states that result from different microstructures on the surfaces. Moreover, the oil-adhesion controllability for different types of oils was also analyzed and the applications of the surface including oil droplet transportation and self-cleaning were discussed. The results reported herein provide a new feasible method for fabrication of underwater superoleophobic surfaces with controlled adhesion, and improve the understanding of the relationship between surface microstructures, adhesion, and the fabrication principle of tunable oil adhesive surfaces.