不同方向石墨烯片构筑纳米孔隙浸润特征

Infiltration characteristics of nanochannels composed of graphene sheets in different directions

以石墨烯为基质构筑的纳米孔隙存在两种壁面结构,水滴浸润纳米孔隙在微流动方面至关重要.本文鉴于实验报道的石墨烯结构,构建了两种石墨烯纳米孔隙,利用全原子分子动力学模拟方法研究了纳米水滴浸润两种纳米孔隙.发现两种不同排列石墨烯构筑相同尺度的纳米孔隙展现出完全不同的浸润特点,一种是放置在纳米孔隙入口处的水滴会自发浸润孔隙,另一种是水滴完全不会浸润孔隙.通过分析两种纳米孔隙结构,总结出了产生上述现象主要归因于纳米孔隙内外表面的润湿性差异.建立了纳米孔隙内外表面完全一样的结构,构建了水滴浸润纳米孔隙的润湿性相图,给出了水滴浸润纳米孔隙的一般性规律.

The infiltration of water droplets in nanochannels is of great importance in microfluidics.In this paper,two types of graphene nano channels with different wall structures are constructed based on the experimentally reported graphene structure,and the infiltrations of water nanodroplet in the two nanochannels are investigated by performing all-atom molecular dynamics simulation.It is found that the two nano channels with the same size,composed of different graphene arrays,exhibit completely different infiltration properties:water droplets cannot infiltrate into the multilayer stacked channels,but can wet the vertical array channels spontaneously and completely.By analyzing the structures of the two nanochannels,the novel phenomenon is mainly attributed to the difference in wettability between the inner surface and the outer surface of the nanochannel.From the perspective of energy,the potential energy of water droplets in the multilayer stacked channels is higher than that outside the channels,while the potential energy of water droplets in the vertical array channels is lower than that outside the channels.Therefore,water droplets can spontaneously infiltrate into the latter ones.The van der Waals interaction between the droplet and the channels and the Coulomb interaction inside the droplet play a dominant role in spontaneously infiltrating the water droplets,while the van der Waals interaction inside the droplet has little effect on the infiltration behavior.In addition,through a series of simulations of water droplets wetting the nanochannels with identical inner surface and outer surface,the wettability phase diagram of water droplets infiltration into nanochannels is established,which represents the general law of water droplet infiltration into nanochannels.