Wang Fei, Nestler Britta
Institute of Applied Materials - Computational Materials Science, Karlsruhe Institute of Technology (KIT), Straße am Forum 7, 76131 Karlsruhe, Germany.
J Chem Phys. 2021 Mar 7;154(9):094704. doi: 10.1063/5.0044914.
In contrast to the wetting phenomenon of pure substance phase, we here concentrate on the wetting behavior of immiscible fluids with two components via numerical simulations. We investigate the energetic contribution, the wall energy and the surface excess energy, to the wetting behavior of liquid solutions varying with temperature. This investigation is in accordance with Cahn's wetting transition theory, where the surface composition plays a vital role. By analyzing the energetic contributions, we reveal two different physical mechanisms of complete wetting: (i) surface tension driven complete wetting, where the wetting microstructure is achieved via the outward spreading of the triple junction, and (ii) diffusion induced complete wetting, where the wetting film is achieved through a direct deposition of the solute on the substrate. The former one is consistent with the classic theory of Young's law, and the latter one is an alternative mechanism. To indicate the broad multiplicity of the microstructural arrangements, we take porous structures to exemplarily elucidate the formation of alternative perfect wetting structures. Differing from the wetting on a flat substrate, we show that the surface composition varying with temperature leads to a distinct wetting phenomenon in porous structures. The present findings provide an alternative interpretation for complete wetting and are expected to be exploited for designing more effectively and efficiently superhydrophilic structures.
与纯物质相的润湿现象不同，我们在此通过数值模拟专注于两种组分的不混溶流体的润湿行为。我们研究了能量贡献、壁能和表面过剩能对随温度变化的液体溶液润湿行为的影响。这项研究符合卡恩的润湿转变理论，其中表面组成起着至关重要的作用。通过分析能量贡献，我们揭示了完全润湿的两种不同物理机制：（i）表面张力驱动的完全润湿，其中通过三相交界处的向外扩展实现润湿微观结构；（ii）扩散诱导的完全润湿，其中通过溶质直接沉积在基底上形成润湿膜。前者与经典的杨氏定律理论一致，后者是一种替代机制。为了表明微观结构排列的广泛多样性，我们以多孔结构为例阐明替代完美润湿结构的形成。与在平坦基底上的润湿不同，我们表明随温度变化的表面组成在多孔结构中导致明显的润湿现象。本研究结果为完全润湿提供了另一种解释，并有望用于更有效和高效地设计超亲水结构。
