A4.2 - A Continuous Flow Multi-Laminar Micromixer with Improved Flow Profile for Infrared Analysis of Chemical Reaction Kinetics

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings SENSOR 2011
A4 - Flow Sensors I
W. Buchegger, M. Vellekoop, C. Wagner, B. Lendl - Vienna University of Technology (Austria), M. Kraft - Carinthian Tech Research AG, Villach (Austria)
95 - 99


The use of micromixers in infrared (IR) spectroscopy is promising e.g. for the study of biomolecular kinetics. To prevent excessive IR absorption by the medium, a maximum channel height of 8 μm was applied in this mixer. An new design generates four laminated fluid layers out of two fluid feeds by a distribution network. Using a 2D simulation the fluid layers are optimized in their thickness to reduce the mixing time by a factor of 9 (tmix~dDiff 2) compared to a two layer system. Further, simulation results for an optimum fluid inlet design are discussed. The shape of the fluid layers with rectangular channel inlets indicates inhibited mixing because of the nonuniform fluid layers. This limitation can be overcome by widening the inlet channel to a wedge form and hence reducing the pressure drop to the far end of the feeding. With this improvement uniform fluid layers are formed and mixing is enhanced significantly. Optical laser scanning confocal measurements were carried out to visualize the horizontal fluid layers proving simulated results. The two liquids, deionized (DI)- water and a 5 μM fluorescein-DI-water solution were pumped through the micromixer using pressure driven syringe pumps. The result of a cross section measurement of the mixing channel with 200μm width shows the four fluid layers as predicted by simulations. The reduced mixing time enables investigating faster chemical reactions by time resolved Fourier transform infrared spectroscopy (FTIR). In a second experiment setup time resolved measurements of sodium sulfite Na2SO3 and formaldehyde solution HCHO were carried out on an FTIR microscope. A total of 86 spectra were recorded within a time of 80 ms and a flow rate of 10 μl/min. Compared to an earlier mixer generation, the mixing time could be improved by a factor of ~25.