Orejon Daniel, Oh Junho, Preston Daniel J, Yan Xiao, Sett Soumyadip, Takata Yasuyuki, Miljkovic Nenad, Sefiane Khellil
School of Engineering, Institute for Multiscale Thermofluids, The University of Edinburgh, Edinburgh EH9 3FD, Scotland, UK; International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
Department of Mechanical Engineering, BK21 FOUR ERICA-ACE Center, Hanyang University, Ansan, Gyeonggi 15588, Republic of Korea.
Adv Colloid Interface Sci. 2024 Feb;324:103075. doi: 10.1016/j.cis.2023.103075. Epub 2023 Dec 28.
A consensus was built in the first half of the 20th century, which was further debated more than 3 decades ago, that the wettability and condensation mechanisms on smooth solid surfaces are modified by the adsorption of organic contaminants present in the environment. Recently, disagreement has formed about this topic once again, as many researchers have overlooked contamination due to its difficulty to eliminate. For example, the intrinsic wettability of rare earth oxides has been reported to be hydrophobic and non-wetting to water. These materials were subsequently shown to display dropwise condensation with steam. Nonetheless, follow on research has demonstrated that the intrinsic wettability of rare earth oxides is hydrophilic and wetting to water, and that a transition to hydrophobicity occurs in a matter of hours-to-days as a consequence of the adsorption of volatile organic compounds from the ambient environment. The adsorption mechanisms, kinetics, and selectivity, of these volatile organic compounds are empirically known to be functions of the substrate material and structure. However, these mechanisms, which govern the surface wettability, remain poorly understood. In this contribution, we introduce current research demonstrating the different intrinsic wettability of metals, rare earth oxides, and other smooth materials, showing that they are intrinsically hydrophilic. Then we provide details on research focusing on the transition from wetting (hydrophilicity) to non-wetting (hydrophobicity) on somooth surfaces due to adsorption of volatile organic compounds. A state-of-the-art figure of merit mapping the wettability of different smooth solid surfaces to ambient exposure as a function of the surface carbon content has also been developed. In addition, we analyse recent works that address these wetting transitions so to shed light on how such processes affect droplet pinning and lateral adhesion. We then conclude with objective perspectives about research on wetting to non-wetting transitions on smooth solid surfaces in an attempt to raise awareness regarding this surface contamination phenomenon within the engineering, interfacial science, and physical chemistry domains.
20世纪上半叶形成了一种共识，这种共识在30多年前又得到了进一步讨论，即光滑固体表面的润湿性和冷凝机制会因环境中存在的有机污染物的吸附而发生改变。最近，关于这个话题再次出现了分歧，因为许多研究人员由于难以消除污染而忽略了它。例如，据报道稀土氧化物的固有润湿性是疏水的，对水不润湿。这些材料随后被证明对蒸汽表现出滴状冷凝。然而，后续研究表明，稀土氧化物的固有润湿性是亲水的，对水是润湿的，并且由于从周围环境中吸附挥发性有机化合物，在数小时到数天内会发生向疏水性的转变。据经验所知，这些挥发性有机化合物的吸附机制、动力学和选择性是基底材料和结构的函数。然而，这些控制表面润湿性的机制仍然知之甚少。在本论文中，我们介绍了当前的研究，这些研究表明金属、稀土氧化物和其他光滑材料具有不同的固有润湿性，表明它们本质上是亲水的。然后，我们详细介绍了关于光滑表面由于挥发性有机化合物的吸附而从润湿（亲水性）转变为不润湿（疏水性）的研究。还开发了一个最新的品质因数，它将不同光滑固体表面对环境暴露的润湿性映射为表面碳含量的函数。此外，我们分析了最近关于这些润湿转变的研究，以便阐明这些过程如何影响液滴钉扎和横向附着力。然后，我们以客观的视角总结了关于光滑固体表面从润湿到不润湿转变的研究，试图提高工程、界面科学和物理化学领域对这种表面污染现象的认识。
