Numerical and Experimental Analysis of Mixing Efficiency in Passive Micromixers Under Laminar Flow

Passive micromixers play a critical role in microfluidic applications, particularly in lab-on-a-chip devices, since they do not require external energy input, being simpler, cheaper and portable. This paper reports the mixing efficiency by numerical simulation (using COMSOL Multiphysics) and by experimental validation of two 2D polydimethylsiloxane micromixer geometries. The tested flow rate ratios, $1: 1,1: 4$ and $1: 10(5: 5 \mu ~\mathrm{L}/\min$, $5: 20 \mu ~\mathrm{L}/\min$ and $2: 20 \mu ~\mathrm{L}/\min$, respectively), produced numerical simulations with an excellent agreement according to experimental results allowing to predict the mixing efficiency of the microchannels' fluids. Both geometries achieved mixing indexes above 80 % in a short mixing path and with small transit times and, for that reason, this work might represent an important breakthrough in this field, considering their future integration in point-of-care diagnostic platforms, where reliable mixing is crucial.