Wang Shao-Yu, Wang Zi-Jie, Wang Dan-Qi, Wang Yi-Bo, Wang Yi-Feng, Zhang Ben-Xi, Yang Yan-Ru, Wang Xiao-Dong, Lee Duu-Jong
State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China.
Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China.
Langmuir. 2024 Nov 12;40(45):24162-24173. doi: 10.1021/acs.langmuir.4c03649. Epub 2024 Oct 30.
Hybrid-wetting surfaces with hydrophilic spots reduced from the micrometer to nanometer scale have been confirmed to enhance vapor nucleation while simultaneously minimizing droplet pinning. Given that surface topography also plays a critical role in influencing nucleation characteristics, the effect of competition between intrinsic wettability and topography on nucleation remains unclear when both surface topography and hydrophilic regions approach the critical nucleation size. This work investigated vapor nucleation on two types of hybrid-wetting nanoconvex surfaces. On random hybrid-wetting convex surfaces, the most negative potential energy sites were located at the sides of the convex structures, leading vapor to preferentially nucleate at these locations, consistent with observations on homogeneous surfaces. Despite similar average potential energy values across the surface, wettability variations in hydrophilic and hydrophobic atoms significantly alter the surface energy distribution. As the wettability difference between hydrophilic and hydrophobic atoms increases, stronger hydrophilic atoms generate relatively higher local energy regions, promoting vapor rapid nucleation. The edge effect still exists at a hydrophilic atom ratio of 10%, and competition among hydrophilic spots impedes vapor nucleation and growth. However, when the ratio increases to 40%, the increased surface average potential energy promotes the probability of vapor contacting the surface, leading to rapid vapor nucleation on the sides of the convex structures. In addition, surface potential energy analysis and the Monte Carlo method revealed that nucleation locations on nanoconvex surfaces are governed by the competition between intrinsic wettability and topography. When the magnitude of the potential energy generated by the hydrophilic atoms exceeds that from the topography, stronger solid-liquid interactions at the top of the convex structure increase the likelihood of vapor contacting the surface, resulting in nucleation at the top. Conversely, when the magnitude of the potential energy generated by hydrophilic atoms is lower than that from topography, nucleation preferentially still occurs on the sides.
具有从微米尺度减小到纳米尺度的亲水性斑点的混合润湿表面已被证实可增强蒸汽成核，同时将液滴钉扎效应降至最低。鉴于表面形貌在影响成核特性方面也起着关键作用，当表面形貌和亲水区域都接近临界成核尺寸时，本征润湿性与形貌之间的竞争对成核的影响仍不清楚。这项工作研究了两种类型的混合润湿纳米凸面表面上的蒸汽成核。在随机混合润湿凸面上，最负势能位点位于凸结构的侧面，导致蒸汽优先在这些位置成核，这与在均匀表面上的观察结果一致。尽管整个表面的平均势能值相似，但亲水和疏水原子的润湿性变化会显著改变表面能分布。随着亲水和疏水原子之间的润湿性差异增加，更强的亲水原子会产生相对较高的局部能量区域，促进蒸汽快速成核。当亲水原子比例为10%时，边缘效应仍然存在，亲水斑点之间的竞争会阻碍蒸汽的成核和生长。然而，当比例增加到40%时，增加的表面平均势能会提高蒸汽与表面接触的概率，导致在凸结构的侧面快速发生蒸汽成核。此外，表面势能分析和蒙特卡罗方法表明，纳米凸面表面上的成核位置由本征润湿性与形貌之间的竞争决定。当亲水原子产生的势能大小超过形貌产生的势能大小时，凸结构顶部更强的固液相互作用会增加蒸汽与表面接触的可能性，从而导致在顶部成核。相反，当亲水原子产生的势能大小低于形貌产生的势能大小时，成核仍优先发生在侧面。
