Biomedical Engineering Reference
In-Depth Information
Tilted light exposure
Sample injection nozzle
Left-side slope
a
d
Left-side inlet
for sheath flow
Center
slope
Sloped sidewall
Cover glass
Center inlet
for sample flow
Cross-section view
Top view
Right-side inlet
for sheath flow
Tilted light exposure
Outlet
Substrate
Sidewall
Substrate
Right-side slope
Side view
Cross-section view
Top view
Substrate
Sheath flow
Sheath flow
b
e
Sample injection
nozzle
Core sample stream
Sheath flow
Sheath flow
Top view
Cover glass
Cross-section
Exposed light
Sheath flow
Sample injection
nozzle
Exposed
light
Core sample stream
Diluted sample
Substrate
Sheath flow
c
f
Side view
Cross-section view
Cored SU-8
Substrate
Cover glass
Top view
Top view
Epoxy glue used for bonding
g
Sheath flow
Sidewall
Sheath flow
Sample flow
Focused sample flow
Sidewall
Epoxy glue used for bonding glass
cover
Sheath flow
FIGURE 5.2
Microluidic.low.cytometer.integrated.in.SU-8..(From.Ren.Yang,.Daniel.L..Feeback,.
and.Wanjun.Wang,.“Microfabrication.and.test.of.a.three-dimensional.polymer.hydro-focusing.unit.
for.low.cytometry.applications,”.
Sens. Actuators A
.118,.259-267,.2005..Adapted.with.permission.
of.Elsevier.)
meters per second), generates “driting” that can be used to focus cells in 3-D at rates greater
than 1700 cells/s.
To create Dean low, this device requires low velocities that are extremely high by microlu-
idic scales, which raises concerns of shear stress acting on the cells. Is there another way to create
Dean low, perhaps one that would be gentler to cells? Je-Kyun Park's group at Korea's Advanced
Institute of Science and Technology (KAIST) has elegantly demonstrated that Dean low can
be induced by a series of contraction-expansion structures in the microchannel (
Figure 5.7
).
Every time the luid enters an expansion of the microchannel, it is forced to follow rotational
lines (to conserve the momentum) that end up concentrating the sample low in the 3-D center
of the channel.
