Micromixers based on molecular diffusion - Micromixers Fundamentals Design and Fabrication - page 189

Campbell and Groisman [33] improved the above split-and-recombine concept with a premixing
network. The device starts with two inlets, but the splitting junction has three outlets. The split-and-
recombine network produces N outlets with different concentrations. The outlets then joined to form
the desired concentration distribution. Unlike the previous designs of Jeon et al. [31] and Dertinger
et al. [32] , the vertical branches have different lengths, thus different resistance and different flow rates
( Fig. 5.21 (a)). The different flow rates allow tailoring the amount of different concentrations, leading
to a tunable concentration distribution.
Amarie et al. [34] used splitting junction with both two and three outlets. The gradient-generating
mixing channels can be designed to be shorter and the overall split-and-recombine section is shorter
than the previous designs which used serpentine design for the vertical mixing channels ( Fig. 5.21 (b)).
The shorter channel length and the shorter residence time allow faster switching between different
concentration distributions. Since switching was mostly realized with external pumps, faster switching
of the concentration distribution can be achieved with integrated microvalves [35] .
FIGURE 5.21
Parallel lamination gradient generator: (a) premixing with different channel lengths and (b) shorter channel
network.
(Reprinted with permission from [33] and [34] .)