纳米尺度下毛细流动的分子动力学模拟

采用分子动力学模拟研究纳米尺度下壁面润湿性对毛细流动的影响，主要考虑纳米通道两侧壁面润湿性相同与不同两种情况。研究表明：两侧壁面润湿性相同条件下，毛细流动随着壁面润湿性增强而加快, 毛细高度随时间的变化早期偏离Lucas-Washburn理论，但后期与其预测符合。在纳米通道两侧壁面润湿性不同的情况下，液面会发生振荡，两侧壁面毛细高度也不相等，且液面振荡的幅度和两侧壁面毛细高度差都随着两侧壁面润湿性差异的增大而增大。基于能量转化分析，提出两侧壁面湿润性不同情况下纳米通道中毛细流动发生的条件以及毛细流动快慢的判别依据。研究结果加深了对纳米尺度下毛细流动机理的认识，并为相关工程应用提供理论参考。

Molecular Dynamics Simulations of Capillary Dynamics at the Nanoscale

Molecular dynamics simulations are utilized to systematically investigate the effects of wettability on capillary imbibition process at the nanoscale. We consider two sets of scenarios. In the first set, the two sidewalls of a nanochannel have the same wettability. We find that the capillary imbibition rate increases with the hydrophilicity of capillary and that the imbibition dynamics deviates from the Lucas-Washburn theory at the early stage but agrees with it at the late stage. In the second set where the two sidewalls have different wetting conditions, the liquid-vapor interface oscillates, and there exists a difference between the capillary height of the two sidewalls. The amplitude of the liquid-vapor interface oscillation and the capillary height difference increase with the wettability contrast between the two sidewalls. We determine the critical condition for the occurrence of capillary imbibition in the nanochannel with inhomogeneous wettability, and propose a method to estimate the evolution of the capillary height. Our findings deepen the understanding of capillary dynamics at the nanoscale and could be useful for relevant engineering applications.