Physik Department, Technische Universität München, 85748 Garching, Germany.
Langmuir. 2010 Aug 3;26(15):12614-25. doi: 10.1021/la9034535.
We theoretically consider the possibility of using electric fields in aqueous channels of cylindrical and planar geometry to induce transport in the absence of mobile ionic charges. Using the Navier-Stokes equation, generalized to include the effects of water spinning, dipole orientation and relaxation, we show analytically that pumping of a dipolar liquid through an uncharged hydrophobic channel can be achieved by injecting torque into the liquid, based on the coupling between molecular spinning and fluid vorticity. This is possible using rotating electric fields and suitably chosen interfacial boundary conditions or transiently by suddenly switching on a homogeneous electric field. A static electric field, however, does not induce a steady state flow in channels, irrespective of the geometry. Using molecular dynamics (MD) simulations, we confirm that static fields do not lead to any pumping, in contrast to earlier publications. The pumping observed in MD simulations of carbon nanotubes and oil droplets in a static electric field is tracked down to an imprudent implementation of Lennard-Jones interaction truncation schemes.
我们从理论上考虑了在没有可移动离子电荷的情况下，利用圆柱形和平板状水溶液通道中的电场来诱导物质传输的可能性。通过将纳维-斯托克斯方程推广到包含水旋转、偶极定向和弛豫的影响，我们分析表明，通过向液体注入扭矩，可以在不荷电的疏水通道中泵送偶极液体，这是基于分子旋转和流体涡度之间的耦合。这可以通过旋转电场和适当选择的界面边界条件来实现，或者通过突然打开均匀电场来实现。然而，无论几何形状如何，静态电场都不会在通道中引起稳定状态的流动。通过分子动力学（MD）模拟，我们证实与早期出版物相反，静态场不会导致任何泵送。在静态电场中碳纳米管和油滴的 MD 模拟中观察到的泵送作用可以追溯到对 Lennard-Jones 相互作用截断方案的不当实现。
