Gao Yurui, Liu Yuan, Jiang Jian, Zhu Chongqin, Zuhlke Craig, Alexander Dennis, Francisco Joseph S, Zeng Xiao Cheng
Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States.
Laboratory of Theoretical and Computational Nanoscience, National Center for Nanoscience and Technology, Chinese Academy of Sciences, Beijing 100190, P. R. China.
JACS Au. 2021 Jun 24;1(7):955-966. doi: 10.1021/jacsau.1c00183. eCollection 2021 Jul 26.
Surfaces with microscale roughness can entail dual-scale hierarchical structures such as the recently reported nano/microstructured surfaces produced in the laboratory (Wang et al. Nature2020, 582, 55-57). However, how the dual-scale hierarchical structured surface affects the apparent wetting/dewetting states of a water droplet, and the transitions between the states are still largely unexplored. Here, we report a systematic large-scale molecular dynamics (MD) simulation study on the wetting/dewetting states of water droplets on various dual-scale nano/near-submicrometer structured surfaces. To this end, we devise slab-water/slab-substrate model systems with a variety of dual-scale surface structures and with different degrees of intrinsic wettability (as measured based on the counterpart smooth surface). The dual-scale hierarchical structure can be described as "nanotexture-on-near-submicrometer-hill". Depending on three prototypical nanotextures, our MD simulations reveal five possible wetting/dewetting states for a water droplet: (i) Cassie state; (ii) infiltrated upper-valley state; (iii) immersed nanotexture-on-hill state; (iv) infiltrated valley state; and (v) Wenzel state. The transitions between these wetting/dewetting states are strongly dependent on the intrinsic wettability ( ), the initial location of the water droplet, the height of the nanotextures ( ), and the spacing between nanotextures ( ). Notably, - and - diagrams show that regions of rich wetting/dewetting states can be identified, including regions where between one to five states can coexist.
具有微观粗糙度的表面可能具有双尺度层次结构，例如最近在实验室中制备的纳米/微结构表面（Wang等人，《自然》，2020年，582卷，55 - 57页）。然而，双尺度层次结构表面如何影响水滴的表观润湿/去湿状态以及这些状态之间的转变在很大程度上仍未得到充分探索。在此，我们报告了一项关于水滴在各种双尺度纳米/近亚微米结构表面上的润湿/去湿状态的系统大规模分子动力学（MD）模拟研究。为此，我们设计了具有各种双尺度表面结构以及不同程度固有润湿性（基于对应的光滑表面测量）的平板 - 水/平板 - 基底模型系统。双尺度层次结构可描述为“近亚微米山丘上的纳米纹理”。根据三种典型的纳米纹理，我们的MD模拟揭示了水滴的五种可能的润湿/去湿状态：（i）卡西状态；（ii）渗入上谷状态；（iii）纳米纹理在山丘上的浸没状态；（iv）渗入山谷状态；以及（v）文策尔状态。这些润湿/去湿状态之间的转变强烈依赖于固有润湿性（ ）、水滴的初始位置、纳米纹理的高度（ ）以及纳米纹理之间的间距（ ）。值得注意的是， - 和 - 图表明可以识别出丰富的润湿/去湿状态区域，包括一到五种状态可以共存的区域。
