Biomedical Engineering Reference
In-Depth Information
Figure 2.48
Inletchannelsofamicrofabricatedproteomicreactor.Thelowrateisdividedintwo
ateachstep.(CourtesyofN.Sarrut,LETI.)
The part of the microreactor where the proteins are “digested” by the enzymes
must be carefully designed in order to have a complete reaction. The proteins are
transported by the flow and the enzymes have been previously immobilized on the
walls of the reactor. In order to have a complete reaction, a maximum surface area
for the contact between proteins and enzymes must be available as shown in the
upper part of Figure 2.48 [49].
This is typically a microfluidic problem coupled with a technological challenge.
The microfluidic problem resembles, at another scale, to the problem of heat ex-
changer where obstacles are introduced to increase the contact surface. However,
the technological constraints much more demanding at the microscopic level, with
the fabrication of micropillars or the use of textured surface. Typical feasible pillars
are shown in Figures 2.49 and 2.50.
The use of computer simulation is essential to compare the efficiency of the dif-
ferent designs proposed by the etching technology. In Figures 2.51 and 2.52, a com-
parison of the flow in two different arrangements of micropillars has been made
(the size of the pillars is less than 10
m
m). The flow field has been computed with the
help of the finite element numerical software COMSOL. The differences between
the two arrangements are obvious. There are poorly irrigated channels in Figure
2.51, but not in the case of Figure 2.52. After computation of different motives, the
configuration of Figure 2.52 has been adopted for the reactor (Figure 2.48).
2.2.14 Recirculation Regions
Recirculation regions are a very useful feature in microfluidic systems. They may
be used to mix and homogenize a fluid [50], to promote biochemical reactions
