Study of mixing enhancement in microfluidic channels through extensional flows

A micromixer design is proposed that incorporates both shear and extensional flows to promote enhanced mixing in laminar flow systems. The shear flows result from the centripetal forces experienced by the fluid being forced to move along a serpentine channel. The elongational flows result from periodic hyperbolic constrictions placed in the path of the fluid, that subject the fluid to constant stress rates. The result of the overlapping two effects on the fluid dynamics is analyzed using computational fluid dynamics, for a broad range of constriction geometries in terms of width and length. The mixing performance of the designs is quantified both in terms of the absolute value of the mixing index, as well as in terms of the energetic cost of mixing associated with the needed pressure differential. This allows for optimal designs to be identified across Reynold numbers ranging from 10 to 100.