Exploring Anomalous Fluid Behavior at the Nanoscale: Direct Visualization and Quantification via Nanofluidic Devices
Exploring Anomalous Fluid Behavior at the Nanoscale: Direct Visualization and Quantification via Nanofluidic Devices
复制标题
探索纳米尺度的异常流体行为：通过纳米流体设备直接可视化和量化
DOI：
10.1021/acs.accounts.9b00411
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发表时间：
2020
影响因子：
18.3
通讯作者：
Sinton, David
中科院分区：
文献类型：
--
作者：
Zhong, Junjie;Alibakhshi, Mohammad Amin;Xie, Quan;Riordon, Jason;Xu, Yi;Duan, Chuanhua;Sinton, David
纳米流体学是对纳米尺度下流体的研究，其中的小尺度效应决定了流体物理，连续介质假设不再完全有效。在这个尺度上，由于大的表面积体积比，流体与边界的相互作用变得更加明显，短期的空间/水合力和远程的范德华力和静电力都决定了流体的行为。这些作用力导致了一系列的异常输运和热力学现象，如超快的水流、增强的离子输运、极端的相变温度和缓慢的生物分子扩散，这些都是广泛计算研究的主题。纳米流体技术的出现也使这些现象的实验量化成为可能，该技术将具有挑战性的纳米流体测量转变为方便的光学和电子记录。我们小组的重点是通过开发新的纳米流体工具，在流体力学和热力学的背景下研究纳米尺度(2到103 nm)的流体行为，检查经典方程在纳米尺度上的适用性，确定偏差的来源，并探索在这种尺度上出现的新物理。在这篇文章中，我们总结了我们关于纳米受限液体的液体传输、汽化和冷凝的最新发现。我们对纳米水传输的研究发现，亲水纳米通道中存在一个额外的阻力，这归因于表面形成的固定水化层导致的横截面积减少。相反，由于水在石墨烯表面的滑移，在石墨烯包覆的疏水纳米通道中发现流动阻力降低。在汽化的背景下，测量了动力学极限蒸发通量，发现由于薄膜蒸发在孔外，亲水性纳米通道/纳米孔中的蒸发通量超过经典理论预测的一个数量级。通过改变小孔外表面的疏水性，消除了这一因素，从而能够识别纳米限制内的真实动力学极限和关键的限制蒸发系数。实验结果证实了单根纳米管和纳米孔系统中的平行扩散-对流阻力模型具有较高的精度。此外，我们还将我们的研究扩展到纳米尺度受限空间中凝结的不同方面。单组份碳氢化合物的凝聚起始符合开尔文方程，而混合碳氢化合物由于表面选择性吸附而偏离了经典理论，并得到了模拟的证实。此外，冷凝动力学与本体不同，根据约束尺度的不同，冷凝动力学由蒸汽传输或液体传输所支配。总之，通过使用新颖的纳米流体器件和测量策略，我们的工作探索并进一步验证了经典流体力学和热力学方程在纳米尺度上的适用性，例如Navier-Stokes方程、Kelvin方程和Hertz-Knudsen方程。这些结果不仅加深了我们对纳米流体基本物理现象的理解，而且对水淡化、石油开采和热管理等各种工业应用也具有重要的意义。展望未来，我们看到了纳米流体设备在探测和量化纳米尺度流体热物理…方面的巨大机遇
ConspectusNanofluidics is the study of fluids under nanoscale confinement, where small-scale effects dictate fluid physics and continuum assumptions are no longer fully valid. At this scale, because of large surface-area-to-volume ratios, the fluid interaction with boundaries becomes more pronounced, and both short-range steric/hydration forces and long-range van der Waals forces and electrostatic forces dictate fluid behavior. These forces lead to a spectrum of anomalous transport and thermodynamic phenomena such as ultrafast water flow, enhanced ion transport, extreme phase transition temperatures, and slow biomolecule diffusion, which have been the subject of extensive computational studies. Experimental quantification of these phenomena was also enabled by the advent of nanofluidic technology, which has transformed challenging nanoscale fluid measurements into facile optical and electrical recordings. Our groups’ focus is to investigate nanoscale (2 to 103nm) fluid behaviors in the context of fluid mechanics and thermodynamics through the development of novel nanofluidic tools, to examine the applicability of classical equations at the nanoscale, to identify the source of deviations, and to explore new physics emerging at this scale. In this Account, we summarize our recent findings regarding liquid transport, vaporization, and condensation of nanoscale-confined liquids.Our study of nanoscale water transport identified an additional resistance in hydrophilic nanochannels, attributed to the reduced cross-sectional area caused by the formation of an immobile hydration layer on the surfaces. In contrast, a reduction in flow resistance was discovered in graphene-coated hydrophobic nanochannels, due to water slippage on the graphene surface. In the context of vaporization, the kinetic-limited evaporation flux was measured and found to exceed the classical theoretical prediction by an order of magnitude in hydrophilic nanochannels/nanopores as a result of the thin film evaporation outside of the apertures. This factor was eliminated by modifying the hydrophobicity of the aperture’s exterior surface, enabling the identification of the true kinetic limits inside nanoconfinements and a crucial confinement-dependent evaporation coefficient. The transport-limited evaporation dynamics was also quantified, where experimental results confirmed the parallel diffusion–convection resistance model in both single nanoconduits and nanoporous systems at high accuracy. Furthermore, we have extended our studies to different aspects of condensation in nanoscale-confined spaces. The initiation of condensation for a single-component hydrocarbon was observed to follow the Kelvin equation, whereas for hydrocarbon mixtures it deviated from classical theory because of surface-selective adsorption, which has been corroborated by simulations. Moreover, the condensation dynamics deviates from the bulk and is governed by either vapor transport or liquid transport depending on the confinement scale. Overall, by using novel nanofluidic devices and measurement strategies, our work explores and further verifies the applicability of classical fluid mechanics and thermodynamic equations such as the Navier–Stokes, Kelvin, and Hertz–Knudsen equations at the nanoscale. The results not only deepen our understanding of the fundamental physical phenomena of nanoscale fluids but also have important implications for various industrial applications such as water desalination, oil extraction/recovery, and thermal management. Looking forward, we see tremendous opportunities for nanofluidic devices in probing and quantifying nanoscale fluid thermophysical …