Mixing intensification of an electroosmotic micromixer with circular mixing units and constriction channels

This paper presents a numerical evaluation of the mixing enhancement mechanisms in a novel electroosmotic microfluidic device featuring circular mixing units connected by microchannels. Flow field and micromixing behavior are analyzed using three-dimensional simulations under a direct current (DC) electric field and two-dimensional simulations with an alternating current (AC) electric field. The results for the DC electric field indicate that when the inlet velocity (U_in) is below 0.1 m/s (Re = 10), increasing the voltage significantly improves the mixing index (MI); however, at an inlet velocity of 0.5 m/s (Re = 50), the MI remains largely unchanged. For the AC-driven micromixer, the MI improves as U_in rises from 0.05 × 10^–3 m/s to 10^–3 m/s. Additionally, the MI grows with increasing AC voltage; however, varying the frequency produces different trends in the MI. High values of the Figure-of-Merit (FoM), which is the ratio of MI to pressure drop (Δp), confirm that the proposed micromixer delivers excellent mixing performance, especially at low inflow velocities.