Biomedical Engineering Reference
In-Depth Information
coniguration.shown.in.Figure.17.13a.and.b,.particles.are.suspended.above.the.electrode.
plan.(if.Re[
K
*].<.0).and.rotate.along.the.electrode.rail..As.particles.rotate,.the.traveling.wave.
adds.additional.translational.force.on.the.suspended.particles.and.transports.them.from.
one.side.to.the.other.in.a.stationary.luid..The.direction.of.such.linear.motions.depends.on.
the.rotation.direction.of.the.particles:.if.the.particles.rotate.counterclockwise,.they.move.
from.right.to.left;.if.clockwise,.they.transport.from.left.to.right.
The. early. TWD. was. used. to. regulate. the. translational. and. circular. motions. of. blood.
cells. (Masuda. et. al.. 1987,. 1988). with. polyphase. electric. signals. of. frequencies. between.
0.1.and.10.Hz..However,.scientists.found.that.either.static.DEP.or.EP.dominated.in.their.
experiments.due.to.the.use.of.low.frequency.electric.signals..High.frequency.(i.e.,.10.kHz-
30.MHz).TWD.was.later.incorporated.to.manipulate.the.motions.of.pollen.and.cellulose.
components. with. quadrature-phase. electric. ields. (Hagedorn. et. al.. 1992;. Fuhr. et. al..
1994a,b)..Similar.manipulations.were.also.demonstrated.with.latex.spheres,.breast.cancer.
cells,. yeasts,. and. parasites. (Fuhr. et. al.. 1991;. Huang. et. al.. 1993;. Talary. et. al.. 1996;. Goater.
et.al..1997;.Wang.et.al..1997;.Burt.et.al..1998;.Pethig.et.al..1998).
The. linear. motion. of. particles. in. TWD. can. also. be. used. in. particle. separation. or.
fractionation..In.these.applications,.a.mixture.of.particles.of.various.dielectric.properties.is.
placed.at.one.end.of.the.electrode.array..As.the.linear.motions.of.particles.exerted.by.TWD.
depends.on.their.permittivity,.some.of.these.particles.transport.faster.than.others..Particles.
of.various.populations.can.then.be.sequentially.collected.when.arriving.at.the.other.end.of.
DEP
0°
180°
0°
180°
0°
180°
0°
180°
Traveling wave
F
DEP
F
TWD
0°
90°
180°
270°
0°
90°
180°
d d
(a)
TWD
Substrate with embedded electrodes
y
x
Polyphase voltage drive
(b)
Figure 17.13
(See companion CD for color igure.)
.Traveling-wave.dielectrophroesis.applications..(a.and.b).Schematic.of.a.
top.view.(a).and.a.cross.section.view.(b).of.a.traveling-wave.electrode.array.setup.
