Hydration Friction in Nanoconfinement: From Bulk via Interfacial to Dry Friction.
Hydration Friction in Nanoconfinement: From Bulk via Interfacial to Dry Friction.
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DOI：
10.1021/acs.nanolett.7b02000
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发表时间：
2017-09
期刊：
影响因子：
10.8
通讯作者：
Alexander Schlaich;Julian Kappler;R. Netz
中科院分区：
文献类型：
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作者：
Alexander Schlaich;Julian Kappler;R. Netz
当紧密接触的水合表面彼此剪切时，纳米级受限水的粘性特性是重要的。大量的实验已经探讨了在亚纳米分离制度的原子级平坦的水合表面之间的摩擦，并建议增加水的粘度，但超限制水的有效粘度的值，水合层摩擦的机制，和交叉的干摩擦极限是不清楚的。我们研究了极性表面之间的剪切摩擦，广泛的非平衡分子动力学模拟在线性响应制度在低剪切速度，这是典型的生物学应用的相关制度。随着水膜厚度的减小，我们发现三个连续的摩擦制度：厚膜摩擦是由散装水粘度。在约一纳米的分离的高粘度的界面水层占主导地位，并增加表面摩擦，而在过渡到干摩擦限制界面滑移集。基于我们的模拟结果，我们构建了一个约束相关的摩擦模型，该模型考虑了来自bulklike水，界面水层和界面滑移的附加摩擦贡献，并且对于任意水膜厚度都是有效的。
The viscous properties of nanoscopically confined water are important when hydrated surfaces in close contact are sheared against each other. Numerous experiments have probed the friction between atomically flat hydrated surfaces in the subnanometer separation regime and suggested an increased water viscosity, but the value of the effective viscosity of ultraconfined water, the mechanism of hydration layer friction, and the crossover to the dry friction limit are unclear. We study the shear friction between polar surfaces by extensive nonequilibrium molecular dynamics simulations in the linear-response regime at low shearing velocity, which is the relevant regime for typical biological applications. With decreasing water film thickness we find three consecutive friction regimes: For thick films friction is governed by bulk water viscosity. At separations of about a nanometer the highly viscous interfacial water layers dominate and increase the surface friction, while at the transition to the dry friction limit interfacial slip sets in. Based on our simulation results, we construct a confinement-dependent friction model which accounts for the additive friction contributions from bulklike water, interfacial water layers, and interfacial slip and which is valid for arbitrary water film thickness.