ABSTRACT
I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
II. General Mobility Expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
III. Mobility Expression Correct to Order z (Henry’s Formula) . . . . . . . . . . . . . . . . . . . 28 IV. Mobility Expression Correct to Order 1/ka . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 V. Mobility Expression Correct to Order z 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
VI. Limiting Mobility of Highly Charged Particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
VII. Liquid Drops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
VIII. General Mobility Expression for Soft Particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
IX. Charged-Polymer-Coated Particle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
X. Uncharged-Polymer-Coated Particle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
XI. Electrophoretic Mobility in Salt-Free Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
In this chapter, we discuss electrokinetic behaviors of particles and drops. The motion of charged
colloidal particles in a liquid under a steady external electric field, which is called electrophoresis,
depends on the thickness of the electrical diffuse double layer formed around the charged particles
and the zeta potential z [1-9]. The zeta-potential z is defined as the potential at the plane where the liquid velocity relative to the particle is zero. We assume that this plane, which is called the slipping
plane or shear plane, is located at the particle surface so that the zeta-potential z is equal to the particle surface potential c0 . We also assume that the magnitude of the applied electric field E is not very large so that the velocity U of the particles, which is called electrophoretic velocity, is proportional to E in magnitude. The ratio of the magnitude of U to that of E is called electrophoretic mobility m, which is given by m ¼ U/E (where U ¼ jUj and E ¼ jEj). In this chapter, we derive equations relating m to z or electric charges of various types of colloidal particles.
