Cao Bing-Yang, Chen Min, Guo Zeng-Yuan
Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.
Phys Rev E Stat Nonlin Soft Matter Phys. 2006 Dec;74(6 Pt 2):066311. doi: 10.1103/PhysRevE.74.066311. Epub 2006 Dec 29.
Molecular dynamics simulations have been carried out to investigate the fluid wetting and flow in nanochannels whose surfaces are structured by an array of nanoscale triangular modules. We find that the surface nanostructures have a dual effect on the boundary slip and friction of the liquid nanoflow. On the one hand, the nanostructures can enhance the surface hydrophilicity for a hydrophilic liquid-solid interaction, and can increase the hydrophobicity for a hydrophobic interaction due to a nanoscale lotus effect. In particular, the nanostructured surface may show superhydrophobicity and lead to the large velocity slip of the liquid flow. On the other hand, simultaneously, the nanostructures distort the nanoscale streamlines of the liquid flow near the channel surfaces and block the nanoflow directly, which decreases the apparent slip length equivalently. The dual effect of the nanostructures on the surface wettability and the hydrodynamic disturbance results in a nonmonotonic dependence of the slip length on the nanostructure size. The simulations imply that the surface nanostructures can be applied to control the friction of liquid micro- and nanoflows.
已进行分子动力学模拟，以研究表面由一系列纳米级三角形模块构成的纳米通道中的流体润湿和流动情况。我们发现，表面纳米结构对液体纳米流的边界滑移和摩擦具有双重影响。一方面，对于亲水性液固相互作用，纳米结构可增强表面亲水性；对于疏水性相互作用，由于纳米尺度的荷叶效应，纳米结构可增加疏水性。特别是，纳米结构化表面可能表现出超疏水性，并导致液流的大速度滑移。另一方面，纳米结构同时会使通道表面附近的液体纳米流的纳米级流线发生扭曲，并直接阻碍纳米流，这等效于减小了表观滑移长度。纳米结构对表面润湿性和流体动力学扰动的双重影响导致滑移长度对纳米结构尺寸呈现非单调依赖性。模拟结果表明，表面纳米结构可用于控制液体微流和纳米流的摩擦。
