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Electrophoretic Phenomenon of a Dielectric Droplet: Constant Surface Charge Density

李幸芸、呂羽涵

Abstract

In this study, computer simulations were used to investigate the electrophoretic Phenomenon of a single dielectric droplet in an electrolyte solution under a constant surface charge density. Our experimental results can be applied to real physical systems such as nanoemulsion.

Research Purpose

  1. The effect of surface charge density on critical point
    1. The effect of surface charge density on the amount of critical point
    2. Compare the trend of the relation between electrophoretic velocity and the viscous ratio before and after reaching boundary condition
  2. The effect of surface charge density on internal and external eddy of the droplet
    1. The internal and external eddy condition under low surface charge density
    2. The internal and external eddy condition under high surface charge density
  3. The effect of viscous ratio on electrophoretic velocity
  4. The effect of surface charge density on electrodynamics
    1. The effect of electric double layer thickness on disturbing charge distribution
    2. The effect of surface charge density on disturbing charge distribution
  5. Compare the effect of constant surface charge density and constant surface potential on electrodynamics

Methodology

We use general program of electrokinetic, which is established with Python as a calculation tool, and use high-performance computer to improve calculation speed and accuracy.

Conclusions and Future Work

  1. Critical point exists under high surface charge density, while the electrophoretic velocity remains constant within droplets of different viscosity.

    1. The directions of internal and external eddy are opposite while both directions would reverse after reaching boundary condition.
    2. External eddy wouldn’t exist if the direction of internal eddy is the same as the direction of the electroosmotic flow.
  3. The higher the viscosity of the droplet is, the more similar its behavior is to rigid condition. Therefore, the interior eddy generated from the electroosmotic flow is slower, and this leads to less energy consumption while this results in higher electrophoretic velocity.

    1. The polarization effect is relatively not obvious when κa is extremely high or low. When κa reaches 1, the polarization effect is the most obvious.
    2. While the surface charge density is higher, the coulomb electrostatic force is more significant, thus polarization effect is more obvious.