Micromixers passive mixer

Microfiuidic mixer Micromixing chip Micromixer Passive mixer... 

Microfluidic-based mixers allow ultrafast reactions to take place in the kinetically limited regime by achieving faster mixing, which is usually obtained by a complex coupling of increases in the advective flux and interfacial area. The micromixers that have been developed can be categorized into active and passive mixers. 

One of the passive mixers was developed using capillary forces to insert and hold the liquids in separate chambers, which are connected via a small gap [45]. It is a self-filling micromixer device and does not require micropumps referring it as an automixing device. This device was developed on a chip with two channels with variable volumes that are separated by a thick porous plate through which mixing takes place by diffusion. The idea was to use the capillary forces to fill one capillary with two liquids. 

In contrast to the presented passive mixers, active micromixers rely on external power input to introduce perturbations within the laminar flow to accelerate mixing. A selection of different external perturbation sources are summarized in Table 4.1 and are discussed briefed here. 

Figure 8a illustrates typical fluorescent images of a micromixer, indicating the mixing behavior at increasing distance downstream at Re = 0.1. The obstruction micromixer is a planar passive microfluidic mixer with diamond-shaped obstructions within the mixing channel to break up and recombine (i.e., laminate)... 

Passive Micromixers, Fig. 1 A generic two-input two-output mixer including lamination and splitting shown in free three-dimensional space, (a) Horizontal lamination and (b) vertical lamination [2]... 

Passive Micromixers, Fig. 3 (a) The front face of the micro T-mixer test chip, (b) The back face of the micro T-mixer [5]... 

One of the promising designs is the modified Tesla structures [46]. It uses the Coanda effect to split part of the fluid stream and direct it so that it recombines with the opposing flow of the other part of the stream. Coanda effect micromixer relies on the redirection of a flow by a special guiding structure that creates new interfaces within the flow [47]. This special passive structure provides good mixing at low flow rates. In this way the Coanda mixer can also be seen as a special realization of the SAR approach using recycle flows [32]. 

Passive Micromixers, Figure 4 Photomicrograph of a microfabricated mixer. The smaii image in the iower ieft corner is the SEM of the mixer. This mixer is about 100 by 200 ixm wide and 10 jcm in depth. Effect of mixing is evaiuated by bringing in two fluids from channeis A and B, and flowing to D. Channei C is not used in this work [6]... 

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