1] School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, Georgia 30332-0430, USA [2] School of Chemistry, Georgia Institute of Technology, 901 Atlantic Avenue, Atlanta, Georgia 30332-0430, USA [3].
Nat Commun. 2013;4:2482. doi: 10.1038/ncomms3482.
Understanding and manipulating fluids at the nanoscale is a matter of growing scientific and technological interest. Here we show that the viscous shear forces in nanoconfined water can be orders of magnitudes larger than in bulk water if the confining surfaces are hydrophilic, whereas they greatly decrease when the surfaces are increasingly hydrophobic. This decrease of viscous forces is quantitatively explained with a simple model that includes the slip velocity at the water surface interface. The same effect is observed in the energy dissipated by a tip vibrating in water perpendicularly to a surface. Comparison of the experimental data with the model shows that interfacial viscous forces and compressive dissipation in nanoconfined water can decrease up to two orders of magnitude due to slippage. These results offer a new understanding of interfacial fluids, which can be used to control flow at the nanoscale.
在纳米尺度上理解和操控流体是一个日益受到科学和技术关注的问题。在这里，我们表明，如果约束表面是亲水的，那么纳米受限水中的粘性剪切力可以比在体相水中大几个数量级，而当表面越来越疏水时，粘性力则大大减小。这种粘性力的减小可以用一个简单的模型来定量解释，该模型包括水表面界面的滑移速度。在一个尖端垂直于表面在水中振动时消耗的能量中也观察到了相同的效果。将实验数据与模型进行比较表明，由于滑移，纳米受限水中的界面粘性力和压缩耗散可以减小两个数量级。这些结果提供了对界面流体的新理解，可用于控制纳米尺度的流动。
