Numerical simulation of electroosmotic mixing of non-Newtonian fluids in a micromixer with zeta potential heterogeneity

Reagent mixing for microchemical analysis is critical. Most biological fluids and polymer solutions used in the biomedical field belong to the category of non-Newtonian fluids. In this study, the mixing of polyacrylamide (PAA) solutions driven by an electric field in a micromixer is numerically investigated. The micromixer is equipped with wall-mounted obstacles and surface potential heterogeneity. The simulation is performed by solving the Laplace equation, Poisson-Boltzmann equation, Navier-Stokes equations, Oldroyd-B constitutive equation, and species transport equation. The mixing efficiency increases from 63.9% to 97.6% when the obstacle surface zeta potential is increased from 20mV to 80mV. However, when the obstacle surface zeta po-tential is increased from 80mV to 120mV, the mixing efficiency decreases. When the EDLs overlap in the channel (kappa = 0.5), the heterogeneous potential has little effect on the mixing efficiency, and the mixing efficiency can be close to 99%. When Wi increases from 0 to 0.3320, the mixing efficiency changes from stable to unstable, and the average mixing efficiency increases.