Electrophoresis of soft particles in a non-Newtonian power-law fluidic microenvironment

The core-shell structured soft particles resemble various classes of bioparticles and environmental entities. The presence of the functional group within the peripheral soft layer may lead to volumetric charge distribution. Besides, depending on the Brinkmann screening length, the shell layer allows penetration of electrolyte ions, and thus, the classical ζ-potential loses its meaning for such composite particles and comprehensive study on the electrophoretic motion of such particles is required. Considering the importance, we made a systematic study on the electrophoresis of pH-regulated soft particles suspended in non-Newtonian background buffer solution. For such a case the coupling between electrostatics and non-Newtonian fluid rheological behavior complicates the particle motion. The widely used power-law model is adopted to consider the non-Newtonian behavior of background buffer solution. Going beyond the Debye–Hückel electrostatic framework, we have obtained numerical results for electrophoretic velocity of soft particles. We have further deduced analytical results for the electrophoretic velocity under various electrostatic and hydrodynamic limits. The impact of pertinent parameters on the particle motion in a non-Newtonian background solution is further illustrated. The magnitude in particle velocity is significantly high when the background fluidic medium is shear thinning in nature, however it reduces with the rise in flow behavior index due to enhanced viscous effect of the background medium. In addition, the impact of pertinent parameters is prominent on the electrophoretic velocity of the particle when the Brinkmann screening length of the peripheral shell layer is large, and their impact further decays with the reduction in Brinkmann screening length.