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measured mixing indices are depicted in Fig. 9(c). In order to
quantify the mixing as a function of the distance along the
curved channel and the interfacial line length, linear
regression is utilized to predict the interfacial line length at
different mixing index. From this linear equation the
R-Squared value is equal to 0.960549. It can be found that
the value is a high correlation and the value of mixing index
can be predicted by the value of the interfacial line length.
(a)
(b)
R-Squared=0.960549
(c)
Fig. 9. Experimental mixing indices for various interfacial line lengths changes
along the downchannel direction of the micromixer.
IV. CONCLUSION
A parallel laminar micromixer with two-dimensional
curved rectangular channels is designed and fabricated in our
study. The flow system is composed of several staggered
three quarters of ring-shaped channels. The centrifugal
forces in curved flow channels make fluids to produce
secondary flows. Two counter-rotating vortices, above and
11-13
May 2011, Aix-en-Provence, France
below the symmetry plane of the channel, coincide with its
plane of curvature. The bifurcation structures of the flow
channels result in the reduction of the diffusion distance of
two fluids. Furthermore, the impinging effects increase the
mixing strength whereas one fluid is injected into the other
fluid. The confocal fluorescence images demonstrate the
changes of the cross-sectional concentration distributions
along the downchannel direction. Phenolphthalein solution,
as a pH indicator, is used for examining the mixing
characteristics of three different curved channels. It can be
seen that the mixing performance of the staggered curved
channels with tapered structures shows superior. The shapes
of the interfaces for staggered curved channels with tapered
structures at different Re are investigated. Results reveal that
the interface configuration of two fluids is affected by the
secondary flows, and the value of mixing index can be
predicted by the value of the interfacial line length..
ACKNOWLEDGMENT
The authors would like to thank the National Science
Council of the Republic of China, Taiwan, for financially
supporting this research under Contract No.
99-2313-B-020-009-. And we are grateful to the National
Nano Device Laboratories for MEMS processes.
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