中文摘要：

采用BMW-MARTINI粗粒化分子动力学模拟方法研究了表面的拓扑结构对疏水性表面润湿状态的影响.模拟结果表明,对于疏水性表面,增大表面的粗糙度对其疏水性影响不大,而主要是影响其润湿状态.在一定范围内（柱间距不超过4.7 nm）,水珠在微柱结构疏水表面的润湿行为受到柱间距（d）和柱高（h）的双重影响.柱间距一定时,存在一个临界的柱高,可以使得水珠在表面的润湿状态由Wenzel态向Cassie-Baxter态发生转变,并且该临界高度随着柱间距的增大而增大.进一步分析发现,本文研究范围内,润湿状态的转变和柱间距与柱高的比值d/h有关,当d/h不超过2时,水珠呈Wenzel态,超过2时则由Wenzel态向Cassie-Baxter态发生转变.通过能量分析,发现润湿状态的转变主要取决于水珠与表面之间的范德华作用.本文研究结果可以为开发具有特定功能的疏水性材料提供参考.

英文摘要：

Researches have showed that there are two factors that can affect the wettability of solid surface： the chemical composition and the surface roughness. In this communication, coarse-grained molecular dynamics simulations based on BMW-Martini force field were used to study the effect of surface topology of hydrophobic surfaces on their wetting states. Simulation results show that the increase of surface roughness has little effect on the hydrophobicity of a hydrophobic surface, but does have effect on its wetting state. For the studied pillar spacing ranges （d≤4.7 nm）, the wetting behavior of water droplets on hydrophobic surfaces with pillared structure is affected by two factors, i.e., pillar spacing and pillar height. For each pillar spacing, there exists a critical pillar height; a wetting transition from the Wenzel state to the Cassie-Baxter state on pillared hydrophobic surface can be observed, and the critical pillar height increases with the pillar spacing. Through a further analysis for the studied surfaces, we find that the wetting transition is related to the ratio of pillar spacing to pillar height, when the ratio is no more than 2, the Wenzel wetting state can be observed; while when the ratio exceeds 2, the Cassie-Baxter state can be observed. Through energy analysis, we find that the wetting transition is mainly dependent on the Van der Waals interaction. When the roughness of a surface is below the critical value, the interaction between the water droplet and surface is very strong, so that water droplet can easily enter into file space between pillars on the surface to form Wenzel state; however, when exceeding the critical value, the interaction between water droplets and surface is weakened, and water droplet is difficult to enter into the gaps, so a Cassie-Baxter state can be observed. This work could provide some guidance for the development of hydrophobic materials. Keywords coarse-graining; molecular dynamic simulation; hydrophobic surface; surface topology; wetting