Sekhon Amandeep, Ajith V J, Patil Shivprasad
Nanomechanics Laboratory, Physics Division and Centre for Energy Science, h-cross, Indian Institute of Science Education and Research, Pune 411008, Maharashtra, India.
J Phys Condens Matter. 2017 May 24;29(20):205101. doi: 10.1088/1361-648X/aa682c. Epub 2017 Mar 21.
The flow of water confined to nanometer-sized pores is central to a wide range of subjects from biology to nanofluidic devices. Despite its importance, a clear picture about nanoscale fluid dynamics is yet to emerge. Here we measured dissipation in less than 25 nm thick water films and it was found to decrease for both wetting and non-wetting confining surfaces. The fitting of Carreau-Yasuda model of shear thinning to our measurements implies that flow is non-Newtonian and for wetting surfaces the no-slip boundary condition is largely valid. In contrast, for non-wetting surfaces boundary slippage occurs with slip lengths of the order of 10 nm. The findings suggest that both, the wettability of the confining surfaces and nonlinear rheological response of water molecules under nano-confinement play a dominant role in transport properties.
局限于纳米级孔隙中的水流对于从生物学到纳米流体装置等广泛领域至关重要。尽管其很重要，但关于纳米级流体动力学的清晰图景尚未出现。在这里，我们测量了厚度小于25纳米的水膜中的耗散，发现对于润湿和非润湿的限制表面，耗散都有所降低。将剪切变稀的Carreau-Yasuda模型拟合到我们的测量结果表明，流动是非牛顿的，对于润湿表面，无滑移边界条件在很大程度上是有效的。相比之下，对于非润湿表面，会出现边界滑移，滑移长度约为10纳米。研究结果表明，限制表面的润湿性和纳米限制下水分子的非线性流变响应在传输特性中都起着主导作用。
