چكيده به لاتين
In the recent years, a considerable number of studies have been devoted to the electrokinetic phenomena, such as electroosmosis, by assuming the internal surface of the microchannels covered by polyelectrolyte layers (PELs). In contrast to most of the theoretical studies considering similar physical properties for the bulk of electrolyte and the PEL, in this study we have investigated the hydrodynamic dispersion caused by the electroosmotic flow inside the soft microchannels assuming different dielectric permitivities, diffusion coefficients and viscosities for the electrolyte and the PEL. First, uising Debye-Huckle approximation, two analytical expressions was introduced for describing both the electrical potential distribution and the velocity distribution. Then, by adopting the Taylor dispersion theory and using the corresponding equations, analytical solutions for the solute concentration field and the effective dispersion coefficient were obtained. The comparison between the results of the above mentioned analytical expressions and their corresponding numerical results revealed that using Debye-Huckle approximation may lead to up to 2% error. Afterwards, by employing a completely different physical-based model we have investigated the broadening of an analyte band from time of injection. It was found that the difference between the permittivities of the electrolyte and the PEL, i.e. ion partitioning effect, can increase the effective dispersion coefficient. Besides, it was concluded that, the more the viscosity of fluid in the PEL, the smaller the hydrodynamic dispersion. On the other hand, it was revealed that the effective dispersion coefficient increases with the reduction of diffusion coefficient of analyte in the PEL. The last but not the least, the ion partitioning effect was found to be more determinative in the effective dispersion coefficient.