Bioinspired Design of a Superoleophobic and Low Adhesive Water/Solid Interface

Abstract

Biological organisms with super-hydrophobic properties, such as lotus leaves, [1] cicada's wings, [2] water strider's legs, [3] and desert beetle's backs [4] always give us inspiration to design and create novel interfacial materials. Learning from nature, fabrication of micro/nanohierarchical structures and chemically modification with low surface free-energy materials provide effective solutions in obtaining super-hydrophobic interfaces.[5-9] However, superoleophobic interfaces, which display apparent contact angles with oil greater than 1508 and low hysteresis, are highly dependent on modification of fluorinated materials, [10][11][12][13][14][15] resulting in a cumbersome situation when exploring new materials. As previously reported, nearly all efforts were focused on the design and preparation of materials, that is, the control of a single phase, although the interfacial properties usually involve the interactions of two or more phases.[16] Therefore, new strategies to fabricate superoleophobic interfaces remain a challenge.As far as we are aware, examples from nature in air rather than in water environments have attracted most attention from biomimetic research on self-cleaning effect. For example, seabirds, rather than fish, are endangered by pollution from oil during a shipwreck. Boats are contaminated by plankton, while fish can keep their body clean in water. The interesting phenomenon of fish keeping their surfaces clean in oil-polluted water, a new superoleophobic model, inspires us to a novel strategy in designing superoleophobic interfaces. This bioinspired superoleophobic interface with low affinity for oil drops is better than traditional approaches commonly used, which employ surfactant solutions to aid in the removal of oils from the surfaces. [17]

Recent developments in polymeric superoleophobic surfaces

“…Generally speaking, the template process includes three steps: preparing a featured template master, molding the replica, and removing the templates. The templates can be natural surfaces, 34,57,[97][98][99][100][101] nanoporous anodic aluminum oxide, 69,102,103 micropatterned Si surfaces, or other artificial structured surfaces.…”

Direct Imaging of Superwetting Behavior on Solid–Liquid–Vapor Triphase Interfaces

“…The design of optimal bioinspired materials should be carefully investigated using the TCL wetting behaviors on natural multiphase interfaces through advanced imaging microscopes. The design of optimal bioinspired materials commonly involves the special wettability of biological surfaces, such as rice leaves, [8a] fish scales, [53] and mosquito compound eyes. [54] Superhydrophobic phenomena of solid surfaces can be explained by the Cassie model theory.…”

Oil‐Water Separation: A Gift from the Desert

“…An alternative method of preparing a superoleophobic interface in an aqueous medium, inspired by fi sh scales, was recently described by Jiang and co-workers. [ 31 ] They found that water trapped in the rough-surface microstructures of fi sh scales forms a layer that repels oil. The trapped water layer makes the surfaces of the scales underwater superoleophobic, giving the fi sh an oil-repellent skin.…”

“…[ 31 ] The characteristics of fi sh scales suggest that surfaces that are superhydrophilic in air are generally superoleophobic in water. [31][32][33][34] Deserts, which are largely uninhabitable, cover a signifi cant area of the earth's surface. In addition, deserts are encroaching on cities where we live, and often cause air pollution when sandstorms occur.…”

“…[31][32][33][34] Sand is an intrinsically superhydrophilic material that will be fully wetted (that is, the spaces between the sand particles will be fi lled with water) when immersed in water. A water cushion will form below an oil droplet placed on a sand layer in water.…”