Commensurability Effects in Viscosity of Nanoconfined Water
Commensurability Effects in Viscosity of Nanoconfined Water
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DOI：
10.1021/acsnano.6b00187
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发表时间：
2016-03-01
期刊：
影响因子：
17.1
通讯作者：
Geim, Andre K.
中科院分区：
文献类型：
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作者：
Neek-Amal, Mehdi;Peeters, Francois M.;Geim, Andre K.
与宏观流体力学的预期相比，疏水纳米毛细管中的水流速度大大提高。这种现象通常用相对较大的滑移长度来描述，而滑移长度又由水与毛细管表面之间的摩擦和水的粘度等微观性质定义。结果表明，当毛细管直径小于2 nm时，承压水的层状结构对水的粘度和流速有很大的影响。为此，我们用平衡分子动力学模拟方法研究了两层平行石墨烯之间的水的结构和动力学。我们发现，对于亚纳米毛细管，剪切粘度不仅大大增加，而且由于毛细管大小和水分子大小之间的公度关系，还表现出很大的振荡。在设计和研究用于海水淡化和过滤的石墨烯和类似膜时，应该考虑粘度的这种振荡行为，因此应该考虑泥浆长度。
The rate of water flow through hydrophobic nanocapillaries is greatly enhanced as compared to that expected from macroscopic hydrodynamics. This phenomenon is usually described in terms of a relatively large slip length, which is in turn defined by such microscopic properties as the friction between water and capillary surfaces and the viscosity of water. We show that the viscosity of water and, therefore, its flow rate are profoundly affected by the layered structure of confined water if the capillary size becomes less than 2 nm. To this end, we study the structure and dynamics of water confined between two parallel graphene layers using equilibrium molecular dynamics simulations. We find that the shear viscosity is not only greatly enhanced for subnanometer capillaries, but also exhibits large oscillations that originate from commensurability between the capillary size and the size of water molecules. Such oscillating behavior of viscosity and, consequently, the slip length should be taken into account in designing and studying graphene-based and similar membranes for desalination and filtration.