Luo Yongsheng, Pang Ai-Ping, Lu Xiaolin
The State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, Jiangsu, P. R. China.
Langmuir. 2022 Apr 19;38(15):4473-4482. doi: 10.1021/acs.langmuir.2c00037. Epub 2022 Apr 4.
The development of micro/nanofluidic techniques has recently revived interest in dynamic shear flow at liquid-solid interfaces. When the nature of the liquid-solid boundaries was revisited, the slip of the fluids relative to the solid wall was predicted theoretically and confirmed experimentally. This indicates that the molecular-level structures of the liquid-solid interfaces will be influenced by the liquid flow over certain temporal and spatial criteria. However, the fluid flow at the boundary layer still cannot be precisely predicted and effectively controlled, somehow limiting its practical applications. Here, we summarize the recent advances for the microscopic structures at the liquid-solid interfaces upon shear flow. Special attention was given to a second-order nonlinear optical technique, sum frequency generation vibrational spectroscopy, which is a powerful tool for exploring the molecular-level structures and structural dynamics at the liquid-solid interfaces and offering new insights into the molecular mechanisms of the fluid slip at the interfaces. Moreover, we discuss the possible approaches for controlling the interfacial slip at the molecular level and highlight the current challenges and opportunities. Although the theoretical framework of the slip at the liquid-solid interfaces is still incomplete, we hope that this Perspective will complement and enhance our understanding of various interfacial properties and phenomena with respect to practical non-equilibrium dynamic processes happening at the interfaces.
微纳流体技术的发展近来重新唤起了人们对液固界面处动态剪切流的兴趣。当重新审视液固边界的性质时，流体相对于固体壁面的滑移在理论上得到了预测，并在实验中得到了证实。这表明，在特定的时间和空间尺度下，液固界面的分子水平结构会受到液体流动的影响。然而，边界层处的流体流动仍然无法被精确预测和有效控制，这在一定程度上限制了其实际应用。在此，我们总结了剪切流作用下液固界面微观结构的最新进展。特别关注了一种二阶非线性光学技术——和频振动光谱，它是探索液固界面分子水平结构和结构动力学的有力工具，为界面处流体滑移的分子机制提供了新的见解。此外，我们讨论了在分子水平上控制界面滑移的可能方法，并强调了当前面临的挑战和机遇。尽管液固界面滑移的理论框架仍不完整，但我们希望这篇综述能补充并加深我们对界面处实际非平衡动态过程中各种界面性质和现象的理解。
