Controlling interfacial mixing zone for microfluidic flow of liquid streams

Controlling the position and dimension of interfacial mixing width within microchannels helps in variety of applications ranging from anti-solvent crystallization to precisely locating the chemical reaction in microchannels, selective separation by convective transport, synthesis of mono-dispersed nanoparticles, reducing the transport resistance in microfluidic fuel cells, optofluidic lenses, etc. This is a big challenge especially while dealing with the miscible liquid streams. Here, we show the variation of the interfacial mixing width for two miscible liquid streams flowing in microchannels. Dynamics of mixing of the liquid streams has been studied in the near vicinity of the junction in the microchannels of different aspect ratios. We found that the convective mixing inside the microchannel is very much dependent on the relative flow rates of the streams and their Reynolds numbers. Interdiffusion mixing width decreased with increasing Reynolds number at any specific point in the direction downstream to the junction. The relative flow rates and Reynolds number of the streams have been found as influencing factors controlling the position of the interface in the microfluidic flow of liquid streams in co-laminar flow.