Biomedical Engineering Reference
In-Depth Information
Figure 6.25
Experimental principle for the measurement of the diffusion coefficient.
6.2.12 Mixing of Fluids
6.2.12.1 Introduction
Mixing of liquid constituents is a major problem in biochips and bioMEMS. The
high degree of laminarity of microflows delays the mixing of constituents. Two
different liquids can flow side by side for a rather long distance before complete
mixing occurs. This is a real difficulty for the miniaturization and compactness ex-
pected from a biochip. It is always possible to design a fluidic system with zigzags
to have more capillary length in a compact surface as sketched in Figure 6.27 and
according to the photograph of the microsystem of Figure 6.28.
However, there is another difficulty linked to poor mixing in biochips. The time
required to execute the different biological processes may be important. Besides
miniaturization, another advantage expected from microsystems is the reduction
of reaction time. It is then often necessary to accelerate the mixing process. Many
different micromixers have been developed. They fall into two categories: active
Figure 6.26
Concentration profile of diffusing species marked with fluorescent markers at three
different locations in the channel.
