Programming Multiphase Media Superwetting States in the Oil–Water–Air System: Evolutions in Hydrophobic–Hydrophilic Surface Heterogeneous Chemistry

Abstract

Studies toward tailoring macroscopic extreme wetting behaviors on a certain well‐defined surface in multiphase media are significant but still at an infant stage. Herein, superantiwetting evolutions in the oil–water–air system can be programmed from single to quadruple superrepellence by controlling the surface hydrophobic–hydrophilic heterogeneous chemistry. Ammonia vapor exposure makes the realization of challenging superhydrophilicity–superoleophobicity possible in air medium, causing the transition from quadruple to triple superantiwetting states in the oil–water–air system. Upon UV illumination, only single superrepellence–underwater superoleophobicity is maintained on titanium dioxide (TiO2, P25)‐based coatings. A reversible transition between underoil superhydrophilicity and superhydrophobicity via an alternating UV irradiation and heating process leads to a switching between “water‐absorbing” and “size‐sieving” effects in water‐in‐oil emulsion separation. A comparative study for investigating two such effects in emulsion separation is further investigated. The current conceptual insights not only extend superwetting states to multiphase media, but can also deepen the understanding of the relationship between macroscopic extreme wetting behaviors and surface chemistry.

Robust and durable liquid-repellent surfaces

“…Recently, by controlling the surface hydrophobic-hydrophilic heterogeneous chemistry, programmable super-antiwetting evolutions in oil-water-air system from single to quadruple super repellence have also been reported. 389 Alterations in the chemistry of superhydrophobic surfaces is a strategy to stabilize lubricants in porous structures of SLIS. Hydrophobically modified substrates show high chemical affinity towards oils, and therefore lubricants are able to wet surfaces completely and also could be stably locked into porous structures.…”

A Review on Applications of Superhydrophobic Materials in Civil Engineering

“…Recently, researchers have been working on improving the mechanical and chemical durability of SHPB materials. [185][186][187][188][189][190][191] It can be improved by increasing the interfacial bonding force. For example, Li et al [185] obtained SHPB surfaces by spraying coating on substrates.…”

Formulating Multiphase Medium Anti-wetting States in an Air–Water–Oil System: Engineering Defects for Interface Chemical Evolutions

“…9,10 Thus, the anti-wetting interface is only confined to the two-phase medium, hence dexterously manipulating anti-wetting evolution from double to triple liquid repellency of particular significance in air−water−oil systems. 8,11 Defect engineering, which indicates adjusting the interface properties by regulating the defect content, size, and spatial location, emerges as an exciting concept for wetting control. 12,13 Defects lower the coordination number of the surrounding atoms; thus, more active sites are exposed at the interface.…”

“…Wetting control plays a crucial part in macroscopic interfaces, which directly acts on the solid–liquid interface effect in various media and provides a basis for the penetrating problems in many fields, such as droplet manipulation, microfluidics, biochemical microsystems, aquatic microbots, oil–water separation, and fog harvesting . Current studies have created a wealth of macroscopic anti-wetting interfaces, but the defined interfaces only maintain the dual anti-wetting state in air–water–oil systems, which greatly limit the application of wetting interfaces in multiphase media . The interface transition from superhydrophilic to superhydrophobic in air is usually accompanied by lost underwater superoleophobicity. , Thus, the anti-wetting interface is only confined to the two-phase medium, hence dexterously manipulating anti-wetting evolution from double to triple liquid repellency of particular significance in air–water–oil systems. , …”

“…Current studies have created a wealth of macroscopic anti-wetting interfaces, but the defined interfaces only maintain the dual anti-wetting state in air–water–oil systems, which greatly limit the application of wetting interfaces in multiphase media . The interface transition from superhydrophilic to superhydrophobic in air is usually accompanied by lost underwater superoleophobicity. , Thus, the anti-wetting interface is only confined to the two-phase medium, hence dexterously manipulating anti-wetting evolution from double to triple liquid repellency of particular significance in air–water–oil systems. , …”