Electrophoretic mobility has been widely used to evaluate the zeta potential of individual colloidal particles, which governs the stability of colloidal dispersions. We demonstrated two experimental methods to measure the AC electrophoretic mobility μ of micron-sized single particles using holographic video microscopy. The three-dimensional position of the particle was estimated by reconstructing the light field from its two-dimensional holographic image, using the Rayleigh-Sommerfeld back-propagation method. In a planar electric field setup, the height dependence of the measured value of μ in the cell enables us to evaluate the actual value of μ, without interference from electroosmotic flow. In a vertical setup, the true value of μ can be directly evaluated by minimizing the influence of the electrode polarization, using a thick cell and a high-frequency electric field. The estimated values of μ obtained using both methods agree with that from conventional electrophoretic light scattering. We also evaluated the distribution of μ values within a colloidal dispersion.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)