A barrier embedded chaotic micromixer

Abstract

Mixing enhancement has drawn a great attention to designing of micromixers, since the flow in a microchannel is usually characterized by a low Reynolds number (Re) which makes mixing quite a difficult task to complete. In this regard, we present a new chaotic passive micromixer, called a barrier embedded micromixer (BEM). In the BEM, chaotic flow is induced by periodic perturbation of the velocity field due to periodically inserted barriers along the top surface of the channel while a helical type of flow is obtained by slanted grooves on the bottom surface in the pressure driven flow. A T-channel and a microchannel with only slanted grooves were fabricated for the purpose of experimental comparison. Mixing performance has been experimentally characterized in two ways: (i) change of average mixing intensity by means of phenolphthalein and (ii) mixing patterns via a confocal microscope. Experimental results showed that BEM has better mixing performance than the other two. A characteristic required mixing length, defined in view of intensity change, increases logarithmically with Re in BEM. The confocal microscope images indicated that BEM could achieve almost complete mixing. The chaotic mixing mechanism, proposed in this study can be easily applied to integrated microfluidic systems, such as micro-total-analysis-systems, lab-on-a-chip and so on.

Evaluation of Floor-grooved Micromixers using Concentration-channel Length Profiles

“…Two counter-rotating vortices were found in the channels of SHM in a study by Aubin et al [12], in which a computational fluid dynamics (CFD) was also used for simulation. Kim et al [13] presented a chaotic micromixer, in which chaotic mixing was achieved by periodic perturbation of a helical type of flow obtained by slanted grooves. Periodically inserted barriers along the channel wall in the micromixer imposed alternating velocity fields with periodic existence of a hyperbolic point, resulting in a chaotic mixing.…”

Geometrical optimization of helical flow in grooved micromixers

“…Owing to its simple planar design, the SHM is readily fabricated using standard soft lithographic methods, 19 thus making a convenient choice for lab-on-a-chip applications requiring rapid mixing of two or more liquids, such as the lysis of whole blood using de-ionized water. 20 Several passive mixer designs have evolved from the original SGM design: Kim et al placed alternating barriers above the slanted grooves to achieve enhanced mixing effects with the barrier embedded mixer (BEM), 21 and Sato et al fabricated PDMS micro-channels with slanted grooves on the sidewalls as well as the channel floor to achieve increases in bulk helical flow. 22,23 To date, there have been a number of theoretical, experimental, and numerical studies aimed at the optimization of SHM-and SGM-type devices.…”

Multivortex micromixing

“…Passive designs are often desirable in applications involving sensitive species (e.g., biological samples) because they do not impose strong mechanical, electrical, or thermal agitation. Examples of passive micromixing approaches that have been widely investigated include the following: (i) ''split-and-recombine'' strategies where the streams to be mixed are divided or split into multiple channels and redirected along trajectories that allow them to be subsequently reassembled as alternating lamellae yielding exponential reductions in interspecies diffusion length and time scales (4,(10)(11)(12); and (ii) ''chaotic'' strategies where transverse flows are passively generated that continuously expand interfacial area between species through stretching, folding, and breakup processes (13)(14)(15)(16)(17)(18)(19)(20). The microchannel structures associated with these mixing elements range from relatively simple topological features on one or more channel walls (ridges, grooves, or other protrusions that can, for example, be constructed by means of multiple soft lithography, alignment, and bonding steps) to intricate 3D flow networks requiring timescales on the order of days to fabricate.…”