Biomedical Engineering Reference
In-Depth Information
C h a p t e r 1 1
Conclusion
At the end of this topic, let us recall the different steps that we have made towards
the comprehension and prediction of the mechanical behavior of micro- and
nanoparticles, macromolecules, and cells.
Because these biologic objects are immerged in a buffer liquid, we have focused
first on the carrier fluid behavior, by studying microfluidic flows in microsystems.
Microfluidics may be considered as a new science by itself. On many points it de-
parts from the classic view of macroscopic fluid dynamics. We have presented and
analyzed the different forms of microflows that can be found in microsystems for
biology: continuous microflows (when a single phase liquid flows continuously in
microchannels), digital microfluidics (when separated microdrops are displaced step
by step on a solid surface), and two-phase flows (when droplets are transported by
an immiscible carrier fluid flowing continuously in microchannels).
Observing that the biologic objects of interest—macromolecules, DNA strands,
proteins, cells, and so fourth—behave differently in the carrier fluid due to their size
and weight, we have investigated the different transport mechanisms from molecu-
lar diffusion to isolated trajectories. Because our approach aims for in vitro prob-
lems and in vivo situations, we have given attention to the behavior of particles in
confined volumes.
Next, since the main purpose of biochips is the study of biological targets such
DNA, proteins, and cells, the principle of key-lock recognition has been presented,
showing that biochemical reactions are used to perform bioanalysis and biorecogni-
tion. Kinetics of the main reactions like DNA hybridization and protein enzymatic
digestion have been carefully detailed from a theoretical standpoint and also in the
different forms they take in a biochip environment.
Because it has been observed that transport of particles by a buffer fluid is not
always specific enough (i.e., the particles of interest cannot be all transported to the
reactive surface), we have presented additional tools to transport and manipulate
biological objects, for example, the use of magnetic particles as transport vectors
and the specific effects of electric fields on these biological objects.
Through this entire book, we have shown that precise handling and manipulation
of micro- and nanoparticles, macromolecules, and cells are at the heart of biotech-
nology. The theoretical background and the modeling approach presented here are
and will likely remain the basis for the comprehension of the phenomena involved
in biochips and bioMEMS, even if biotechnology is rapidly evolving and new devel-
opments emerge constantly. Since the irst edition of this topic, digital and droplet
microfluidics have seen a considerable development. Some other developments are
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