Biomedical Engineering Reference
In-Depth Information
and.magnetic.properties.
69
.Yoo.et.al..demonstrated.that.the.bifrustum.nanocrystals.made.
of.a.gold.core.and.a.silver.shell.showed.stronger.SPR.than.pure.gold.nanoprisms..In.addi-
tion.to.extremely.strong.SPR.effects,.Au/Ag.alloy.nanostructures.hold.a.number.of.advan-
tages.over.a.single.pure.metal,.including.better.plasmon.tenability.and.a.broader.surface.
plasmon.band.for.multiple-probe.enhancement.
68
Since.the.luorescent.signal.intensity.of.MEF.is.partly.based.on.the.surface.irregularity,.
it.is.conceivable.that.the.enhancement.could.be.ampliied.by.using.biaxial.and.bimetallic.
wrinkles..Our.lab.has.recently.demonstrated.methods.to.create.sharp.bimetallic.wrinkles.
for.molecular.detection.using.luorescein..During.the.biaxial.shrinkage.of.the.PS.sheet,.the.
metal.buckled.and.formed.nanogaps..The.edges.of.these.nanogaps.created.hot.spots,.and.
bursts.of.intensity.are.emitted.when.a.luorescein.molecule.diffuses.into.a.hot.spot,.and.
then.the.intensity.drops.right.back.to.background..The.luorescent.signal.enhancement.of.
such.a.mechanism.was.in.the.range.of.several.thousand-fold.over.glass.substrate.(data.not.
shown).
13.4 BetterShrinkageThanPolystyreneSheet
With. advances. in. polymer. science,. novel. polymeric. blends. have. become. available. for.
potential.application.in.POC.technology..Polyolein.(PO),.a.thermoplastic.commonly.used.
for. the. manufacturing. of. shrink-wrap. ilms,. possesses. excellent. shape. memory. proper-
ties. that. can. be. recovered. through. the. application. of. heat.. Based. upon. the. blend. of. the.
polymer.and.processing.condition,.this.elastomeric.property.can.be.tuned..Furthermore,.
PO.ilms.exhibit.attractive.optical.properties,.such.as.transmission.over.a.large.range.of.
wavelengths,.in.addition.to.low.autoluorescence.
70
.Combined,.these.features.make.PO.an.
attractive.polymer.for.applications.in.microluidics.
By.leveraging.the.shrinkage.property.of.the.PO.sheets,.it.was.demonstrated.that.high-
resolution.microstructures.can.be.generated,.obviating.the.need.for.photolithography.
and. advanced. tooling.. In. addition,. unlike. PS. sheets,. which. yielded. a. modest. 40-60%.
increase.in.resolution.postshrinkage,.PO.sheets.achieved.95%.reduction.in.surface.area.
(Figure 13.9).. By. simple. printing. on. the. polymer. sheets,. deined. ink. patterns. can. be.
heated. to. generate. high-aspect. micromolds.. In. addition. to. the. physical. contraction. of.
the. polymer. sheet,. the. patterned. features. are. induced. to. form. well-rounded. features,.
which. are. dificult. to. achieve. with. standard. photolithography.. This. process,. which. is.
analogous. to. the. relow. of. photoresist. in. standard. photolithography,. allows. for. the.
relow. of. toner. ink,. creating. well-rounded. features.. Further,. the. improvement. in. sur-
face.area.reduction.facilitated.the.formation.of.better.aspect.ratios.for.the.microstruc-
tures.(Figure 13.10).
The.ability.to.integrate.microarray.technology.and.luorescent.protein.analysis.in.micro-
luidic. devices. can. greatly. contribute. to. the. µTAS. for. POC. diagnostics.. Recently,. it. has.
been.shown.that.by.printing.protein.patterns.onto.thermoplastics,.it.is.possible.to.increase.
array.density.as.well.as.protein.concentration.through.the.heat-induced.shrinking.of.ther-
moplastics.
71
.This.method.can.be.demonstrated.through.micro.contact.printing.(µCP).of.
primary.luorescently.labeled.antibodies.onto.the.polymer.sheets,.or.through.the.sequen-
tial.attachment.of.the.primary.antibody.and.secondary.luorophore-conjugated.antibody..
