Swirl mixing at microfluidic junctions due to low frequency side channel fluidic perturbations

Swirl mixing between the input arms of a microfluidic system using vibration (Lab Chip 9 (2009) 1435–1438 [20]) has been shown to provide rigorous blending within a very short length along the flow stream. Investigations here, both numerical and experimental, indicate that this is due to an asymmetry in the manner in which liquid enters and exits a channel into a confined space. Based on this understanding, we demonstrate an alternative approach that applies low frequency side channel fluidic perturbations. This approach permits versatility in having mixing occur selectively anywhere along the flow stream, isolates and ensures that mixing occurs only at these locations, as well as minimizes movement so that image blurring, which limits the ability to assess mixing effectiveness optically, is reduced.