Bio‐Inspired Hierarchical Macromolecule–Nanoclay Hydrogels for Robust Underwater Superoleophobicity

Abstract

Robust underwater superoleophobicity – oil repellence that is stable under loading – is achieved by constructing hierarchical macromolecule‐nanoclay hydrogels (see images), inspired by the oil‐repellent nature of the composite surface of fish. The synergetic effect of micro‐/nanostructures and the mechanical strength of hybrid hydrogels in general supports the stability of trapped water on the hydrogel surface, endowing hybid hydrogels with robust superoleophobicity (upper right inset) even under loading forces.

Smart surfaces with switchable superoleophilicity and superoleophobicity in aqueous media: toward controllable oil/water separation

“…[1][2][3] Inspired by fish scales, artificial superoleophobic surfaces in aqueous media have been realized in recent years, and the study of surface oil wettability in aqueous media is emerging as a new research focus. [4][5][6][7] The wettability of oil on a material surface, when submerged in an aqueous environment, has a critical role in many practical applications, such as droplet manipulation in microfluidics, [8][9][10] cell and protein adhesion control on surfaces, [11][12][13][14] preparation of electrowetting-based displays 15 and oil/water separation. 16,17 It is anticipated that a surface with controlled oil wettability, or more desirably a smart surface that switches its oil wettability in response to external stimuli in aqueous media, would offer great promise in the design and fabrication of intelligent materials for advanced applications.…”

“…1,[4][5][6] Although the hydrophilic surface chemistry works well for obtaining underwater oleophobicity, it by itself is not possible to switch to oleophilic when immersed in aqueous media, as the hydrophilic surface traps water, and the water-trapped surface repels oil due to the repellency between polar (trapped water in the surface) and non-polar (oil) molecules. To realize oleophilicity in aqueous media, a surface chemistry that is both oleophilic and hydrophobic is generally required.…”

Hygro-responsive membranes for effective oil–water separation

“…To effect the gravity-driven separation of all types of oil-water mixtures in a single step, the ideal membrane is expected to be hydrophilic (or superhydrophilic 14 ) and oleophobic (or superoleophobic 15 ), both in air and when submerged in water. However, a membrane that is oleophobic in air typically loses its oleophobicity under water, and vice versa 16,17 .…”

Recent developments in polymeric superoleophobic surfaces

“…We have successfully fabricated hydrogel films with underwater superoleophilicity, extremely low oil adhesion and high mechanical strength. 1,34,35,109 In the next step, we will try to use these materials in practical applications. This work is now in progress.…”