Dielectrophoretic Phenomena of a Liquid Droplet in an Electrolyte Solution
Date Issued
2015
Date
2015
Author(s)
Lin, Chih-Lun
Abstract
Dielectrophoresis (DEP), the migration of a dielectric in a non-uniform electric field, has grabbed a great deal of interest in micro/nano-technologies such as microfluidic devices, biomaterial and lab-on-a-chip. However, relevant theoretical researches are still limited. In addition, there exist various kinds of particles other than traditional rigid one, including liquid droplets and biological cells, which cannot be modeled as rigid particles. In present study, the effective polarization, characterized by the dipole coefficient, of a charged liquid droplet in an electrolyte solution and subjected to an alternating electric field, is studied theoretically with the electrokinetic model. Dipole coefficient is calculated as a function of the double-layer thickness, the droplet’s surface charge, viscosity, permittivity and the electric-field frequency. The electrophoretic motion seriously influences the electric double layer and thus polarizability. First, Positive correlation between dipole coefficient and the particle’s surface charge is found. Second, the dipole coefficient of the highly-charged droplet reaches local maximum when plotted versus frequency. Oppositely, the dipole coefficient and the droplet’s viscosity are in negative correlation. Dipole coefficient of the low-viscosity droplet is two or more times greater than that of the high-viscosity one. The permittivity alters the dipole coefficient in a limited range at high frequencies. In the last part, our theoretical predictions are compared with experimental data. The good agreement between them leads to a conclusion that our model is able to adequately predict the experimental results.
Subjects
dielectric
dielectrophoresis
AC electric field
electrokinetics
liquid droplet
effective dipole moment
double layer polarization
Type
thesis
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ntu-104-R02524065-1.pdf
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