Chapter 10 - Dynamic Electrophoresis of Porous Spherical Particles

Abstract

Abstract Due to the large amount of fixed charges carried and its hydrodynamic permeability, the dynamic electrophoresis for a porous particle is much larger than the corresponding rigid particle situation in general. Much larger electric driving force coupled with much weaker hydrodynamic drag force leads accordingly to sharp peaks order-of-magnitude larger in the corresponding electroacoustic spectrometry for a porous particle. Moreover, the counterion condensation effect due to the strong Coulomb attraction force from the large amount of fixed charges within the particle as well as the particle permeability results in a phenomenon that most of the counterions reside within it; hence, not much outside. Hence, the effect of κa, or the double layer suppression effect, is much weaker as well in comparison with the rigid particle situation. An astonishing phenomenon is observed in suspension systems: The higher the particle concentration is, the faster the particle moves! This is because it is the double layer polarization within the particle that generates the electric driving force. Higher particle concentration provides more sources of counterions that can be possibly driven into the interior of whichever nearby porous particles to enhance its mobility. Hence, collectively, the overall particle mobility in a suspension system increases accordingly. As charged porous particles are often used to model polyelectrolytes like proteins and DNAs, the dynamic mobility analyzed here has direct applications in biomedical or biochemical applications involving them.