AC electrophoretic mobility of individual microscale colloidal particles measured using holographic video microscopy

摘要

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 mu 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 mu in the cell enables us to evaluate the actual value of mu, without interference from electroosmotic flow. In a vertical setup, the true value of mu 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 mu obtained using both methods agree with that from conventional electrophoretic light scattering. We also evaluated the distribution of mu values within a colloidal dispersion. Published under license by AIP Publishing.