Electroviscous effects on the squeezing flow of thin electrolyte solution films
Electroviscous effects on the squeezing flow of thin electrolyte solution films
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电粘性对电解质溶液薄膜挤压流动的影响
DOI：
10.1017/jfm.2020.68
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发表时间：
2020
影响因子：
3.7
通讯作者：
F. Mugele
中科院分区：
文献类型：
--
作者：
Cunlu Zhao;Wenyao Zhang;D. van den Ende;F. Mugele
我们详细地分析了限制在两个带电表面之间的薄电解液薄膜挤压过程中的电粘性效应。这两个带电表面由一个曲面和一个平面组成，模拟了动态原子力显微镜测量电解液溶液作用力时针尖-衬底的构型。在润滑极限条件下，通过求解Nernst-Planck-Poisson/Navier-Stokes方程，得到了电粘性修正挤压流场在尖端和衬底之间的解析解。我们还推导了针尖-衬底相互作用的解，它包括一个保守的双电层(EDL)力和一个电粘性效应增强的耗散流体动力力。目前的工作主要集中在耗散水动力，因为保守的EDL力已经被著名的Derjaguin-Landau-Verwey-Overbeek理论很好地描述。我们引入了针尖表面的幂指数($n)，这使得对针尖轮廓对电粘性效应的影响进行了前所未有的定量表征。我们观察到一种似乎与直觉相反的效应，对于给定的针尖-基板分离，电粘性效应在Zeta($\Unicode[STIX]{x1D701}$)电势的某个特定值处最强，并随着$\Unicode[STIX]{x1D701}$电势偏离此值而减弱。在给定的电粘性电势下，EDL的反离子电导率是决定电粘性效应的主要因素。除了增强耗散的流体动力相互作用力外，电粘性效应还改变了薄电解质溶液薄膜中的速度分布，使其更加尖锐。
We present a detailed analysis of the electroviscous effect in the squeeze out of thin electrolyte films confined between two charged surfaces. The two charged surfaces consist of a curved surface and a flat surface, which closely simulate the tip–substrate configuration in the force measurement of electrolyte solutions with dynamic atomic force microscopy. In the lubrication limit, we find the analytical solution of the electroviscous-effect-modified squeezing flow field in the thin electrolyte film confined between the tip and substrate by solving the Nernst–Planck–Poisson/Navier–Stokes equation under the justified condition of pseudo-steadiness. We also derive the solution of the tip–substrate interaction, which comprises of a conservative electric double layer (EDL) force and an electroviscous-effect-enhanced dissipative hydrodynamic force. The current work focuses on the dissipative hydrodynamic force since the conservative EDL force has been well described by the well-known Derjaguin–Landau–Verwey–Overbeek theory. We introduce a power-law index ($n$) for the tip surface, which enables an unprecedented quantitative characterization of the tip profile effect on the electroviscous effect. We observe a seemingly counter-intuitive effect that, for a given tip–substrate separation, the electroviscous effect is the strongest at one particular value of the zeta ($\unicode[STIX]{x1D701}$) potential and diminishes as the $\unicode[STIX]{x1D701}$ potential departs from this value. We reveal the counterion conductivity of the EDL to be the governing factor for the electroviscous effect under a given $\unicode[STIX]{x1D701}$ potential. In addition to enhancing the dissipative hydrodynamic interaction force, the electroviscous effect modifies the velocity profiles in the thin electrolyte solution films such that they are much sharper.
影响因子：
8.6
作者：
Bazant, Martin Z.;Storey, Brian D.;Kornyshev, Alexei A.
通讯作者：
Kornyshev, Alexei A.