Biomedical Engineering Reference
In-Depth Information
the electrodes and ended up in the lower outlet C. The device was operated at a
flow rate of 0.087
l/min with a throughput of 480 cells/min for both samples.
The separation efficiency was more than 97%. For these experiments, the time
window defined by the velocity of the fluid flow (181
m
m
m/s) and the separation
channel length (1,400
m
m) was about 7.7 s, thus leading to an nDEP drift velocity of
about 6.5
m
m/s.
11.4.4 Continuous-Flow Separation of Samples by Size
As elaborated in Sect. 11.3 and illustrated in Fig.
11.2c
, samples of different sizes
but having the same polarizability (e.g., nDEP) can be separated by size. The DEP
force expressed in (
11.1
) clearly shows that the magnitude of DEP force is propor-
tional to the cubic power of particle radius. Thus, the larger particles attain a
stronger nDEP force and can be diverted to the upper branch B, whereas the smaller
ones, experiencing a weaker nDEP force, move to the lower branch A. Figure
11.6a
shows continuous separation of 5
m particles from 10
m particles under 55 Vac at
m
m
1 MHz. The separation efficiency for 5
m particles is 88% at the lower branch A
m
and that for 10
m particles is 100% at the upper branch B. Moreover, separation of
m
10 and 15
m particles was also successfully achieved with a separation efficiency
of 100% for both particle sizes as shown in Fig.
11.6b
. Both separation experiments
were operated at a flow rate of 0.68
m
l/min. By assessing the voltages required to
achieve the separation of these two cases, the voltage for the second case (with
larger particles) is anticipated to be lower than that for the first, since the larger
particles attain a stronger DEP force under the same applied voltage.
m
11.5 Conclusions
This chapter presents manipulation of cells using DEP forces via sidewall PDMS
composite electrodes in a complete polymer DEP device. Three main functions of
the device are demonstrated, including (1) characterization of cell DEP behavior,
(2) separations of cells from latex particles and live and dead cells by polarizability,
and (3) separation of microparticles by size. The DEP characterization results
reveal the excellent capability of conducting PDMS composite electrodes accu-
rately to provide the desired DEP behavior regimes for both yeast and bacterial
cells. Furthermore, the very high separation efficiency of ~97% for all cases (either
by polarizability or by size) demonstrates that conducting PDMS composite
electrodes have promising performance and versatility to deal with a variety of
cells in biofluids.
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