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Forces acting on a particle in a concentration gradient under an externally applied oscillating electric field

机译:在外部施加的振荡电场下以浓度梯度作用于粒子上的力

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摘要

We report a force field on a particle in a concentration (conductivity) gradient under an externally applied oscillating electric field. The conductivity gradient was established through integrated microcapillaries bridging high- and low-conductivity streams in dedicated microchannels. Particles in low-conductivity electrolyte were observed to experience a strong force with the application of an oscillating field and pulled to the microcapillary openings where they were held against the flow. Particle trapping was accompanied by a concurrent electrolyte injection from high- to low-conductivity channel, triggered with the externally applied field and further contributed to the conductivity gradient near the trapping sites. We experimentally evaluated the force dependence on the magnitude and frequency of the excitation field for 10 μm polystyrene particles immersed at various conductivity levels. The experiments suggest that the observed force cannot be simply explained by dielectrophoresis or diffusiophoresis alone and further requires the consideration of a so-called concentration polarization force. This force has been rather recently postulated based on a theoretical treatment and yet to be experimentally validated. Using the theoretical treatment of this force, together with fluidic drag and diffusiophoresis, we correctly predicted trapping trajectories of particles based on a simultaneous solution of Poisson-Nernst-Planck and Stokes equations. The predicted and measured trapping velocities were found in reasonable agreement (within a factor of <1.6), suggesting that the consideration of the concentration polarization force is necessary for describing the observed particle behavior.
机译:我们在外部施加的振荡电场下以浓度(电导率)梯度报告了粒子上的力场。通过在专用微通道中桥接高和低电导率流的集成微毛细管建立电导率梯度。观察到低电导率电解质中的颗粒在施加振荡场时会受到很大的力,并被拉到微毛细管开口处,使它们逆流流动。颗粒的捕集伴随着电解质从高电导率通道向低电导率通道的注入,这是由外部施加的电场触发的,并进一步促进了捕集位点附近的电导率梯度。我们通过实验评估了浸入各种电导率水平的10μm聚苯乙烯颗粒对激励场的大小和频率的依赖关系。实验表明,所观察到的力不能仅通过介电泳或扩散电泳简单地解释,并且还需要考虑所谓的浓度极化力。最近已经根据理论方法推测了该力,尚待实验验证。使用对该力的理论处理,以及流体阻力和扩散电泳,我们基于Poisson-Nernst-Planck方程和Stokes方程的同时解,正确预测了粒子的俘获轨迹。预测和测得的捕集速度在合理的范围内找到(小于1.6的因子),这表明考虑到浓差极化力对于描述观察到的粒子行为是必要的。

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  • 来源
    《Applied Physics Letters》 |2014年第9期|094105.1-094105.5|共5页
  • 作者

    Yuan Luo; Levent Yobas;

  • 作者单位

    Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Hong Kong, People's Republic of China;

    Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Hong Kong, People's Republic of China;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
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