AC electrokinetics and dielectrophoretic spectroscopy of colloidal suspensions

The electromigration of these species is classified into two regimes, based on the ratio of the size of a particle a to the Debye length double 

EP of an ionic molecule with characteristic radius much smaller than the E)e-bye length, or conditions 1. The motion of these charged particles 

FIGURE 7-10 The two limits for the EP behavior of ions and particles A. EP of an ion (a/X g 1), with electric field lines not appreciably distorted by the presence of the ion B. EP of a micron-sized particle (a/X gy 1) with surface/charge- layer interaction similar to the flat-wall EO flow 

To define the zeta-potential it may be recalled that in the Debye-Huckel theory for the counterion cloud around a point charge, the potential profile around the central particle of charge q = is given by  

Now the zeta potential can be redefined as the electrostatic potential at the surface of an ionic sphere (x = a)  

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