Biomedical Engineering Reference
In-Depth Information
5.2.5 Tunable Hydrophoretic Focusing
None of these approaches can be turned of or tuned in real time (except by changing the low
rate). Recently, Je-Kyun Park's group from KAIST (Korea) has reported a device that is remi-
niscent of Ligler's low cytometer (see
Figure 5.5
), but implemented in PDMS so that the roof
can be pushed up and down. Slanted obstacles in the roof of the microchannel induce rotational
low and (if the roof is at the right height) produce size-dependent ordering of the microparticles
(
Figure 5.14
). he efect has been put to use to demonstrate the separation of blood cells from
plasma (
Figure 5.14c
).
5.2.6 Cell Sorting Using Surface Acoustic Waves
Surface acoustic waves
(
SAWs
) are devices that contain interdigitated transducers that con-
vert electrical signals into acoustic waves using piezoelectric materials. Recently, David Weitz's
group at Harvard used a SAW device to produce acoustic streaming (see Section 3.4.2) orthogo-
nally to the cell-containing stream, which quickly displaced the stream within the channel;
switching speeds on the order of 1 kHz were achieved (
Figure 5.15
).
Flow
a
Obstacle
y
x
z
h
1
y
x
4 µm beads
z
50 µm
h
1
b
Flow
Obstacle
h
2
∆H
H
h
2
c
Inlet
Outlet
Blood plasma
Blood cells
200 µm
FIGURE 5.14
Tunable.hydrophoretic.focusing..(From.Sungyoung.Choi.and.Je-Kyun.Park,.“Tunable.
hydrophoretic.separation.using.elastic.deformation.of.poly(dimethylsiloxane),”.
Lab Chip
.9,.1962-
1965,.2009..Reproduced.with.permission.from.The.Royal.Society.of.Chemistry..Figure.contributed.
by.Je-Kyun.Park.)
