Department of Mechanical & Aerospace Engineering, University of Strathclyde, Glasgow, UK.
Langmuir. 2013 Jun 11;29(23):6936-43. doi: 10.1021/la401131x. Epub 2013 May 28.
We use molecular dynamics (MD) simulations to investigate the dynamic wetting of nanoscale water droplets on moving surfaces. The density and hydrogen bonding profiles along the direction normal to the surface are reported, and the width of the water depletion layer is evaluated first for droplets on three different static surfaces: silicon, graphite, and a fictitious superhydrophobic surface. The advancing and receding contact angles, and contact angle hysteresis, are then measured as a function of capillary number on smooth moving silicon and graphite surfaces. Our results for the silicon surface show that molecular displacements at the contact line are influenced greatly by interactions with the solid surface and partly by viscous dissipation effects induced through the movement of the surface. For the graphite surface, however, both the advancing and receding contact angles values are close to the static contact angle value and are independent of the capillary number; i.e., viscous dissipation effects are negligible. This finding is in contrast with the wetting dynamics of macroscale water droplets, which show significant dependence on the capillary number.
我们使用分子动力学（MD）模拟来研究纳米尺度水滴在运动表面上的动态润湿。报告了沿垂直于表面方向的密度和氢键分布，并首先评估了三种不同静态表面（硅、石墨和虚构的超疏水表面）上液滴的水耗尽层的宽度。然后，作为毛细数的函数，测量了在光滑运动的硅和石墨表面上的前进和后退接触角以及接触角滞后。我们在硅表面上的结果表明，接触线处的分子位移受与固体表面相互作用的影响很大，部分受表面运动引起的粘性耗散效应的影响。然而，对于石墨表面，前进和后退接触角值都接近静态接触角值，并且不依赖于毛细数；即，粘性耗散效应可以忽略不计。这一发现与宏观尺度水滴的润湿动力学形成对比，后者显示出对毛细数的显著依赖性。
