Droplet-based mixing characteristics in bumpy serpentine microchannel

In the present study, a three-dimensional unsteady model is developed via coupling volume-of-fluid (VOF) method with component transport model to investigate the droplet-based mixing in the bumpy serpentine microchannel with different bumps structures. The hydrodynamics underlying the droplet-based mixing in bumpy serpentine microchannel is revealed and the influences of layout and number of bumps on comprehensive mixing performance inside the droplets with different size are clarified. The results indicate that, centrifugal component immersion and component entrainment by the nonuniform vortices in droplet are two main factors for promoting droplet-based mixing in serpentine microchannel. The centrifugal component immersion can be enhanced by the outside bumps of bumpy serpentine microchannel but suppressed by the inside bumps. Owing to lower viscous friction, the pressure drop in the serpentine microchannel with outside bumps is less than that with inside bumps, causing higher mixing efficiency. There is an optimal bump number for the best absolute mixing performance for a fixed flow condition in the serpentine microchannel with outside bumps, when the interval between the adjacent bumps is nearly as same as the squeezed droplet length. The absolute mixing performance of the larger droplet is smaller and less sensitive to the variation of the bump number.

Automated summary

In this study, a three-dimensional unsteady model was developed to investigate droplet-based mixing in bumpy serpentine microchannels with different bump structures. The results revealed that centrifugal component immersion and component entrainment by nonuniform vortices are the main factors promoting mixing in these microchannels. Additionally, the outside bumps enhance mixing efficiency by increasing centrifugal component immersion and reducing pressure drop.