Analysis on Chaotic Mixing Inside a Plug and Determination of Lagrangian Velocity

Mixing multiple fluids based on plugs flow is a better approach in microfluidic system. In order to understand the mixing mechanism based on plug flow, theoretical analysis based on chaotic mixing was carried out, and a micro-resolution particle image velocimetry (Micro-PIV) is used to measure the flow field in liquid plug involving liquid species to be mixed. Two recirculation flows forming in plugs can enhance the mixing efficiency because folding and stretching of the liquids occured deterministically in plugs. In addition, the Lagrangian velocity were determinated on the basis of Eulerian velocity by subtracting this droplet velocity vector from the measured Eulerian velocity field of the tracing particles results inside the moving droplet. These results are helpful to optimize the structure of micromixer and develop droplet based microfluidic system.