RESUMO

A novel method of characterizing a micromixer is proposed. The method is based on two-dye, ratiometric laser-induced fluorescence measurements using a confocal microscope. A fluorescent tracer is added to one of the two inlet fluid streams of the micromixer while a second fluorescent dye is added to both inlet fluid streams to serve as a reference. The emission intensity of the fluorescence tracer was normalized by the reference fluorescent signal. Using this technique an accurate, spatially-resolved, quantitative measurement of the tracer concentration field can be obtained. This method was used successfully to quantify the mixing performance of three different micromixer designs: a straight channel, a curved, meandering channel, and a square-wave channel. Computational fluid dynamics (CFD) simulations were also conducted for the straight and curved, meandering micromixers. The CFD results were in good agreement with experimental data. At a Reynolds number of 22.5, the square-wave microchannels yield the best mixing performance with a higher mixing efficiency for a fixed channel length. Curved microchannels showed better mixing performance than straight microchannels at this same Reynolds number. The numerical and experimental results underscore the importance of spatially-resolved measurements in the depth-wise direction since even relatively simple, planar mixer designs can produce complex three-dimensional flow fields.