Dielectrophoresis - The Nanobiotechnology - page 406

particles.are.later.released.by.switching.off.the.electric.signal.and.lushing.with.additional.
fresh.liquid.if.necessary..When.appropriate.electrode.conigurations.are.used,.p-DEP.and.
n-DEP.may.be.applied.simultaneously.and.colloids.are.relocated.in.various.locations.by.
p-DEP.or.n-DEP,.depending.on.their.size.and.dielectric.properties..Besides.dielectric.par-
ticles,. biological. components,. including. viruses. (Muller. et. al.1996a;. Morgan. and. Green.
1997;.Green.et.al..1997;.Hughes.et.al..1998,.2001,.2002;.Morgan.et.al..1999),.proteins.(Washizu.
et.al..1994),.DNA,.and.cells.(Holmes.et.al..2003),.were.successfully.trapped.and.separated.
with.such.DEP-based.low.separation.
In. these. high-throughput. DEP. separation. applications,. the. interdigitated. castellated.
geometry. is. often. favored. among. all. electrode. conigurations. introduced. in. Section.
17.3.. It. attributes. to. their. several. advantages:. (1). providing. a. large.∇ E 2 . with. a. relatively.
low. electric. voltage,. (2). convenient. to. expand. the. same. electrode. layout. to. a. large. area.
to. increase. separation/sorting. throughput,. and. (3). lexible. on. the. electrode. dimensions.
to.satisfy.different.trapping.criteria..The.interdigitatal.castellated.coniguration.has.been.
successfully.used.to.separate.particles.based.on.their.size.or.permittivity.difference..As.
shown. in. Figure. 17.8a,. alive. and. dead. yeast. cells. were. successfully. separated. with. the.
viable. cells. collected. at. the.electrode. edges. while. the.dead. cells. were. collected. between.
the. electrodes. (Markx. et. al.. 1994b).. Such. pear. chain. (for. viable. cells). and. diamond. (for.
dead. cells). aggregation. patterns. are. typically. seen. when. trapping.colloids. with. a. signal.
frequency. below. 100.kHz. (Pethig. et. al.. 1992).. Their. formations. are. generally. believed. to.
be.associated.with.the.electrohydrodynamic.lows,.although.the.true.mechanism.is.still.
in.debate.(Green.and.Morgan.1998;.Ramos.et.al..1999)..With.a.slightly.modiied.castellated.

(a)

(b)

Figure 17.8
(See companion CD for color igure.) . The. interdigitated. castellated. electrode. systems. for. DEP. trap. and.
separation..(a).Separation.of.viable.and.nonviable.yeast.cells.with.the.viable.cells.collected.at.the.electrode.
edges. and. the. dead. ones. collected. in. the. electrode. gaps.. (Reproduced. from. J. Biotechnol., . 32,. Markx,. G.H.,.
Talary,. M.S.,. and. Pethig,. R.,. Separation. of. viable. and. non-viable. yeast. using. dielectrophoresis,. 29-37,.
Copyright.1994b,.with.permission.from.Elsevier.).(b).Separation.of.particles.of.two.different.sizes.by.direct-
ing.them.in.the.upstream.and.downstream.regions,.respectively,.with.a.DEP.signal.of.20.V peak-peak .at.2.MHz..
(Reproduced.with. Sens. Actuators B Chem., .142,.Yasukawa,.T.,.Suzuki,.M.,.Shiku,.H.,.and.Matsue,.T.,.Control.of.
the.microparticle.position.in.the.channel.based.on.dielectrophoresis,.400-403,.Copyright.2009,.with.permis-
sion.from.Elsevier.)