Alibakhshi Mohammad Amin, Xie Quan, Li Yinxiao, Duan Chuanhua
Department of Mechanical Engineering, Boston University, 110 Cummington Mall, Boston, MA, 02215, USA.
Sci Rep. 2016 Apr 26;6:24936. doi: 10.1038/srep24936.
Nanoscale liquid transport governs the behaviour of a wide range of nanofluidic systems, yet remains poorly characterized and understood due to the enormous hydraulic resistance associated with the nanoconfinement and the resulting minuscule flow rates in such systems. To overcome this problem, here we present a new measurement technique based on capillary flow and a novel hybrid nanochannel design and use it to measure water transport through single 2-D hydrophilic silica nanochannels with heights down to 7 nm. Our results show that silica nanochannels exhibit increased mass flow resistance compared to the classical hydrodynamics prediction. This difference increases with decreasing channel height and reaches 45% in the case of 7 nm nanochannels. This resistance increase is attributed to the formation of a 7-angstrom-thick stagnant hydration layer on the hydrophilic surfaces. By avoiding use of any pressure and flow sensors or any theoretical estimations the hybrid nanochannel scheme enables facile and precise flow measurement through single nanochannels, nanotubes, or nanoporous media and opens the prospect for accurate characterization of both hydrophilic and hydrophobic nanofluidic systems.
纳米尺度的液体传输控制着各种纳米流体系统的行为，但由于与纳米限域相关的巨大水力阻力以及此类系统中产生的极小流速，其特征和理解仍然很差。为了克服这个问题，我们在此提出一种基于毛细流动的新测量技术和一种新颖的混合纳米通道设计，并使用它来测量水通过高度低至7纳米的单个二维亲水性二氧化硅纳米通道的传输。我们的结果表明，与经典流体动力学预测相比，二氧化硅纳米通道表现出增加的质量流阻力。这种差异随着通道高度的降低而增加，在7纳米纳米通道的情况下达到45%。这种阻力增加归因于在亲水性表面上形成了一个7埃厚的停滞水合层。通过避免使用任何压力和流量传感器或任何理论估计，混合纳米通道方案能够通过单个纳米通道、纳米管或纳米多孔介质进行简便而精确的流量测量，并为准确表征亲水性和疏水性纳米流体系统开辟了前景。
