Dynamic Electrophoretic Mobility in Electroacoustic Phenomenon: Concentrated Dispersions at Arbitrary Potentials

Abstract

Recent advancement in both fundamental theory and experimental technique makes electroacoustics devices powerful analytical tools in quantifying a dispersed system. Because properties of a concentrated sample can be measured directly without dilution, it is readily applicable to various applications of practical significance. The present work analyzes the dynamic electrophoresis of a concentrated dispersion for the case the applied electric field is weak. Available results in the literature are extended to a general condition of arbitrary electrical potential, double layer thickness, volume fraction of dispersed phase, and frequency of applied electric field, taking the effects of double layer polarization and interaction between neighboring double layers into account. The dynamic nonlinear problem leads to several unique features that are not observed in the corresponding linear (low surface potential) or static problems. For example, because of the effect of double layer polarization, the magnitude of the dynamic mobility may have a local maximum and the phase angle may have a negative (phase lead) local minimum as the frequency of the applied electric field varies.