Passive mixing in micro-channels with geometric variations through µPIV and µLIF measurements

Five passive micro-mixers were designed, fabricated and tested, and were compared to that of the conventional T-shaped channel in order to examine the mixing performance by increasing the lateral convection/or related mixing mechanisms. Electro-osmotic pumping was used to generate fluid velocities in the creeping flow regime (Re 1) in order to achieve the mixing enhancement by chaotic advection. Iodine dye (qualitative) and rhodamine B (quantitative) mixing experiments were visualized and measured through conventional microscopes and with µLIF techniques. µPIV measurements were used for 2D velocity vectors and stretching calculations. Steady-state results show that the alternating wavy-regime (chaotic mixers) micro-channels and inline aligned elements (which alter the flow direction laterally) in micro-channels can induce stirring and improve the mixing significantly even at extremely low Reynolds numbers.