Biomedical Engineering Reference
In-Depth Information
E.Coli
(a)
(b)
(c)
(d)
(e)
(f )
Figure 17.11
(See companion CD for color igure.)
. EDEP. DNA. concentration. and. focusing.. (a).
E. coli
. cells,. (b). 1.kbp. single-
stranded.DNA.molecules.were.trapped.and.enriched.at.the.center.of.the.constriction.in.0.5×.TBE.buffer..(Panels.
(a.and.b):.Reproduced.with.permission.from.Chou,.C..and.Zenhausen,.F.,.Electrodeless.dielectrophoresis.for.micro.
total.analysis.systems,.
IEEE Eng. Med. Biol.,
.22,.62-67,.Copyright.2003,.IEEE.).(c).An.array.of.EDEP.concentration.
sites.with.T5.double-stranded.DNA.molecules.trapped.in.a.PCR.buffer.solution..(Reproduced.from.
Biophys. J.,
.83,.
Chou,.C.,.Tegenfelbt,.J.O.,.Bakajin,.O.,.Chan,.S.S.,.Cox,.E.C.,.Darnton,.N.,.Duke,.T.,.and.Austin,.R.H.,.Electrodeless.
dielectrophoresis.of.single-.and.double-stranded.DNA,.2170-2179,.Copyright.2002,.with.permission.from.Elsevier.).
Schematic.of.single.(d).and.multiple.(e).converging.tunnel.electrode.pair.for.particle.focusing..(f).An.image.of.a.unit.
with.multiple.DEP.focusing.structures.integrated.on.a.microluidic.particle.sorter.platform..(Reproduced.from.
Biosens. Bioelectron.,
.14,.Muller,.T.,.Gradl,.G.,.Howitz,.S.,.Shirley,.S.,.Schnell,.T.,.and.Fuhr,.G.,.A.3-D.microelectrode.
system.for.handling.and.caging.single.cells.and.particles,.247-256,.Copyright.1999,.with.permission.from.Elsevier.)
If. the. contraction. geometry. shown. in. Figure. 17.11a. changes. gradually. and. is. made. of.
metal,. it. creates. a. converging. DEP. tunnel. instead.. When. lowing. through,. particles. are.
levitated.slowly.by.n-DEP.into.a.thin.layer.along.the.channel.centerline,.as.shown.in.Figure.
17.11b.. When. necessary,. multiple. converging. tunnels. may. be. arranged. to. further. focus.
particles.into.the.low.centerline..This.helps.prevent.the.variation.of.the.DEP.force.on.the.
same.type.of.particles,.which.initially.stay.in.different.laminar.luid.layers..In.fact,.such.
tunnel. focusing. has. been. widely. adopted. in. DEP-based. ield. low. fraction. systems. and.
other.integrated.microluidic.platforms.for.the.sorting.of.particles,.cells,.DNA,.and.other.
biological.components.(Fiedler.et.al..1998;.Schnelle.et.al..1999;.Kralj.et.al..2006;.Cheng.et.al..
2007;.Demierre.et.al..2008;.Kim.et.al..2008)..Optically.induced.virtual.electrodes.were.also.
successfully.demonstrated.for.DEP.particle.centralization.(Lin.and.Lee.2008).
17.4.5 DeP-Based Field Flow Fractionation
Beyond.the.binary.separation,.more.heterogeneous.particles.can.be.sorted.based.on.their.
different. DEP-induced. particle. distribution. in. the. transverse. direction. of. low,. or. ield.
low. fractionation. (FFF).. In. DEP-FFF,. one. or. a. few. types. of. particles. are. pulled. toward.
the. electrode. surface. while. others. are. repelled. toward. the. middle. of. the. low. channel..
