Electroosmotic Micromixing of Non-Newtonian Fluids: A Numerical Study

This paper presents a novel electroosmotic micromixer designed for high-performance mixing of non-Newtonian fluids, leveraging DC-driven electroosmotic flow within a strategically electrode-patterned microchannel. The study's primary novelty lies in its comprehensive parametric investigation of the synergistic effects of fluid rate-dependent viscosity (via the Carreau–Yasuda model) and electrokinetic forcing on mixing performance, an aspect less explored compared to studies focusing solely on shear-dependent viscosity. The mixer’s performance is analyzed using the finite-element solution of the coupled flow, electric field, and concentration equations, with a special focus on the effects of inlet velocity, power-law index (n), applied voltage, and, crucially, the fluid relaxation time (λ). Results demonstrate that the Degree of Mixing (DOM) increases from ~۳۷% to ~۷۰% as the applied DC voltage rises from ۰ to ۶۰ V for a shear-thinning fluid (n = ۰.۶). Furthermore, DOM exhibits a strong non-monotonic dependence on relaxation time, peaking at ۸۵% for λ = ۰.۵, a ۳۸% increase from the case with minimal rate-dependent viscosity (λ = ۰.۰۰۵). This reveals the optimal role of shear-thinning effects, contrasting with recent designs that utilize complex geometries or active elements. Conversely, DOM sharply declines from ~۱۰۰% to ~۴۰% as the inlet velocity increases from ۵×۱۰⁻⁵ to ۵×۱۰⁻² m/s, and decreases from ۴۷% to ۲۷% as the fluid behavior shifts from shear-thinning (n = ۰.۶) to shear-thickening (n = ۱.۴). Grid independence and simulation validation studies confirm the reliability of the proposed numerical approach. These insights facilitate the rational design of micromixers for complex fluids, promising improved integration in lab-on-a-chip and biomedical applications.

کلیدواژه ها:

Electroosmotic micromixer ، Carreau&ndash ، Yasuda model ، Non-Newtonian fluids ، Degree of mixing