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电渗流通过改变流固界面的双电层效应，使流体在通道内产生高剪切率从而驱动界面处产生大的滑移速度。本文采用分子动力学模拟构建电渗流纳米通道模型，研究了石墨烯带电壁面纳米通道内流体流动特性与壁面滑移减阻特性。结果表明，电渗流改变了双电层结构增加其扩散层的可移动性；同时在电场作用下扩散层的离子定向迁移，通过粘性作用带动整体流动，增大了流体的流动性能。引入离子后，Na+在壁面处吸附削弱流体与壁面之间的吸附力，从而提升流体在限域空间的驱动力，增大离子溶液滑移长度和流速。最终提出了一种通过调控石墨烯非对称壁面电荷实现通道内溶液超快运输的方法，成功实现了石墨烯通道内溶液电渗流的滑移减阻效果。为纳米限域空间内微流体的快速节能输运提供了理论依据。Electroosmotic flow in a confined domain transport space in microfluidics by modifying the double electric layer effect at the fluid-solid interface. In order to increase the fluid to generate high shear rate in the channel, which drives the formation of large slip velocity at the interface to increase the fluid transportation in the channel. In this paper, molecular dynamics simulations are used to construct an electroosmotic flow nanochannel model, and the fluid flow characteristics and wall slip reduction properties within graphene charged-wall nanochannels are investigated. The results show that the electroosmotic flow changes the structure of the bilayer to increase the mobility of its diffusion layer; at the same time, the ions in the diffusion layer under the action of the applied electric field undergo directional migration and drive the overall fluid flow through the viscous effect, which enhances the mobility performance. After the introduction of ions, Na+ is adsorbed at the wall surface, which weakens the adsorption force between the fluid and the wall surface and enhances the driving force of the fluid in the confined domain space, thus increasing the slip length and flow rate.
Finally, by modulating the charge size of the upper and lower wall surfaces and thus forming asymmetric channel wall charges, the resulting electric field gradient superimposed on the applied electric field further enhances the driving force of the ions and alters the distribution of the adsorbed layer of Na⁺ and the migration behavior of Cl-, thus increasing the transport of the solution in the channel. Therefore, in this paper, by proposing a method to realize the ultrafast transport of solution in the channel by modulating the asymmetric wall charge of graphene, the slip reduction effect of the electroosmotic flow of solution in the graphene channel is successfully realized. A theoretical basis is provided for the fast and energy-saving transportation of microfluidics in the nano-limited space.-
Keywords:
- Electroosmotic flow /
- Wall charge /
- Slip rent reduction /
- Bilayer
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