Biomedical Engineering Reference
In-Depth Information
better, faster, and cheaper drew many of us into this ield. he discovery that there were
unexpected features of the behavior of luids in microchannels was surprising, at least in
the engineering community. his ield became known as “
microluidics
.” In this chapter,
we will introduce the highlights of this new ield.
Biology began exploiting the principles of microluidics a few billion years before the 1990s.
For example, bacteria are so small that when they swim through low-viscosity luids like water,
they stop within microseconds when their lagellar motors reverse—they have so little momen-
tum that, to them, water appears as viscous as honey appears to us. Blood capillaries in higher
animals exploit the fact that difusion of small molecules over short distances is very eicient,
so turbulent low is not necessary to provide rapid transport of oxygen to tissues. It is worth
the efort for the BioMEMS student and researcher to ponder for a few minutes why one should
spend time and money to build a microluidic device—ater all, it may not be as advantageous as
one might think, and it is oten less straightforward than the all-too-abbreviated experimental
sections of scientiic articles would lead you to believe.
3.1 Why Go Small?
Microluidic devices generally confer six large classes of advantages, as graphically depicted in
Figure 3.1
:
(A) Flow in microchannels is
laminar
(nonturbulent) and thus the low patterns and
concentrations can be mathematically modeled, making quantitative predictions of
Microfluidics
Deterministic
flow
Deterministic
flow
Small channels
Laminar flow
Cellular
scales
Cellular
scales
Control and
automation
Control and
automation
Microvalves
Micropumps
High throughput
High throughput
Cheap fabrication
+ cheap operation
Small reagents/waste
Small reagents/waste
Small device footprint
Small device footprint
FIGURE 3.1
Advantageous.features.of.microluidic.devices.in.BioMEMS.applications.
