Performance of serpentine micromixers with non-rectangular cross-section

Serpentine microchannels have been popular choices for microfluidic mixers due to their relative easy fabrication and possibility for re-use. The technique used in these types of microchannels aims to utilize the cross-sectional transversal (Dean) flows experienced by the fluids as they round a curved channel geometry. However, because of the reliance on centrifugal forces the mixing quality is strongly Reynolds number-dependent, with high quality mixing being achievable only at Re > 100. In the current work we show that employing channels with non-rectangular cross-sections can be an effective strategy to increase the mixing efficiency in these designs and lower the Reynolds number at which they can be employed. To this end, we seek to optimize the cross-sectional geometrical parameters to maximize their overall mixing performance. The results of the optimization process, namely the fluid flow characteristics, are obtained numerically through computational solutions of the Navier-Stokes equations and the convection-diffusion equation. We also include experimental results comparing the mixing performance of our optimized channels using non-rectangular cross-sections, to those with standard rectangular topology.