倒三角形纳米粗糙表面液滴润湿性分子动力学模拟

固体表面纳米结构可以有效地调控界面润湿特性，在材料能源等领域具有重要应用前景。改变纳米结构的几何尺寸能够在一定范围内调节润湿特性，但存在一定的局限性，调节固液间能量系数能够进一步改变界面的润湿特性。然而，纳米粗糙表面液滴在更大区间内的固液相互作用系数下的润湿特性研究甚少。本文采用分子动力学模拟的方法，研究了倒三角形纳米粗糙表面液滴在不同区间能量系数下呈现的润湿行为，并采用渗透率进行表征。结果发现：四个不同的区间内固液间能量系数对渗透率的作用规律不同，呈现出先增后减的趋势，液滴也依次呈现出显著的润湿态，对应润湿状态图中疏水的Cassie态到亲水的Wenzel态，而能量系数越过临界值(~7)，Wenzel态再反转回显著的Cassie态；同时，液滴分子空间分布呈现明显的规律性，其底层原子在晶格线或晶面均衡分布，形似壁面原子的外延生长。本文的研究获得了能量系数对润湿性影响规律的全貌性认识，对纳米结构表面润湿性的设计和调控具有一定的指导意义。

A Molecular Dynamics Simulation on Wettability of a Liquid Droplet on Solid Surface with Nanoscale Inverted Triangular Grooves

Solid surface with nanostructures can effectively regulate interfacial wettability, which has important application prospect in material energy and other fields. Changing the geometric dimension of nanostructures can adjust the wetting property in a certain range, but it has some limitations. Adjusting the solid-liquid energy parameter can further regulate and control interfacial wetting property. However, the effect of energy parameter during greater interval on wettability of droplets on nanostructured surface is rarely reported. Using the molecular dynamics simulations, wettability of a liquid droplet on solid surface with nanoscale inverted triangular grooves was studied with several energy parameters in different intervals. Such wettability can be characterized by penetrating rate. Increasing energy parameter in the four different intervals makes penetrating rate grow within varied ways, which increases firstly and then decreases. The droplet also in turn exhibits a significant wetting state, corresponding to the hydrophobic Cassie state to the hydrophilic Wenzel state in the wetting state map, and then reversed to the hydrophobic Cassie state if the energy parameter exceeds the critical value (~7). At the same time, the spatial distribution of droplet molecules shows obvious regularity, in which underlying atoms evenly distribute in the lattice line or crystal surface, shaped like the epitaxial growth of the solid atoms. The overall understanding of the effect of energy parameter on wettability is obtained, which provides direction to design or regulates wettability in nanostructure surface.