Particle Shape-Dependent Electrophoresis in Viscoelastic Fluids

The electrophoretic velocity of a charged dielectric particle is independent of its size and shape in a Newtonian fluid under the thin Debye layer limit in the weak-field regime. Our previous paper (Bentor and Xuan, Analytical Chemistry 2024, 96, 3186-3191) reported particle size-dependent electrophoresis in viscoelastic poly(ethylene oxide) (PEO) solutions. We demonstrate herein that the fluid elasticity also induces the particle shape dependence of electrophoretic velocity likely because the polymer stress around a particle varies with its shape. Specifically, altering the shape of a particle from sphere to pear and peanut enhances the electrophoretic velocity in a viscoelastic fluid as the particle becomes slenderer. This phenomenon, which is found absent from a Newtonian fluid, becomes stronger in higher-concentration PEO solutions because of the enhanced fluid elasticity effect. It may be utilized for the label-free electrophoretic separation of particles and cells in non-Newtonian microfluidic devices.