Relationship and Interconversion Between Superhydrophilicity, Underwater Superoleophilicity, Underwater Superaerophilicity, Superhydrophobicity, Underwater Superoleophobicity, and Underwater Superaerophobicity: A Mini-Review

Abstract

Superwetting surfaces have received increasing attention because of their rich practical applications. Although various superwettabilities are independently achieved, the relationship between those superwettabilities is still not well-clarified. In this mini-review, we show that superhydrophilicity, underwater superoleophilicity, underwater superaerophilicity, superhydrophobicity, underwater superoleophobicity, and underwater superaerophobicity can be obtained on a same structured surface by the combination of hierarchical surface microstructures and proper chemistry. The relationship and interconversion between the above-mentioned different superwettabilities are also well-discussed. We believe that the current discussion and clarification of the relationship and interconversion between different superwettabilities has important significance in the design, fabrication, and applications of various superwetting materials.

Nature-Inspired Superwettability Achieved by Femtosecond Lasers

“…A layer of air is formed between the water medium and the surface microstructure of the lotus leaf (Figure 23(i)). If a gas bubble rises and touches the lotus leaf in the water, the gas in the bubble is easily pushed by the water pressure into the air layer around the lotus leaf (Figure 23(j)) [26,121]. Finally, the gases in the bubble and in the trapped air layer merge (Figure 23(k)).…”

“…Underwater Antibubbles and Bubble Absorption. The behavior of a bubble on a solid surface depends on the wettability of the solid surface to bubbles [26,89,121]. The underwater superaerophobic surface has the function of resisting bubbles in the water.…”

“…It was not until the late twentieth and early twenty-first century that the causes of these extreme wettabilities were understood with the development of microscopy and microanalysis techniques. The study shows that the wettability of the material surface mainly depends on the chemical composition and the microstructure of the solid surface [24][25][26][27][28]. Due to its key role in solving the problems related to energy, environment, resources, and health, superwettability has become one of the hot research directions in materials and micro/nanomanufacturing [29][30][31][32][33].…”

“…Underwater Wettability. The underwater wettability is closely related to the wettability of the structured substrate in the air [26,89]. Yong et al experimentally and theoretically discussed the relationship and interconversion between six different superwetting states [89,122,123].…”

Emerging Separation Applications of Surface Superwettability

“…The synergistic effect of the hierarchical microstructure and the hydrophobic waxy crystals with low surface energy results in the superhydrophobicity for lotus leaf [41][42][43][44][45][46][47]. Inspired by the lotus leaves, a variety of superhydrophobic materials can be prepared by combining hierarchical microstructure and low-surface-energy chemical components [124][125][126][127][128][129][130][131][132][133][134][135][136][137][138][139][140]. Superhydrophobicity is the synergistic effect between surface microstructures and low-surface-energy chemical composition.…”