Biomedical Engineering Reference
In-Depth Information
to.fabricate.wrinkles.for.forming.aligned.patterns.of.buckles.on.planar.surfaces.that.were.
patterned.by.a.photolithography.process.
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.Watanabe.and.Hirai.improved.this.approach.
by.simply.prestretching.the.PDMS.sheet.to.improve.their.feature.sizes.to.6-20.µm.striped.
patterns.
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.Eimenko.et.al..utilized.wrinkled.substrates.for.separating.particles.based.on.
size.by.fabricating.uniaxial.wrinkles.by.stretching.PDMS.
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.Utilizing.the.wrinkles,.two.
different.size.silica.particles.(3.and.10.µm).and.67.nm.PS.latex.in.water.lowed.over.the.
buckled. surfaces. in. a. microluidic. cell.. After. the. particles. lowed,. they. began. to. seg-
regate.. The. biggest. silica. particles,. 10. µm,. were. entrapped. between. the. grooves. of. the.
buckles,. while. the. smaller. silica. particles,. 3. µm,. rested. on. top. of. the. smaller. buckles..
The.smallest.PS.latex.particles.aligned.themselves.in.the.smaller.wrinkle.wavelengths,.
1-5.µm..Yoo.et.al..was.able.to.achieve.higher-resolution.wrinkles.approximately.2.µm.in.
periodicity.
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.Our.lab.has.demonstrated.that.we.could.fabricate.nanowrinkles.by.using.
a. two-step. approach. and. tailor. the. scale. range. for. the. nanometer. metal. wrinkles. by.
adjusting.the.thickness.of.the.metal.deposited.on.PS.sheets.
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.Furthermore,.we.were.able.
to.easily.orient.the.metallic.nanowrinkles.in.a.uniaxial.or.biaxial.fashion.
The. overall. fabrication. procedure,. shown. in. Figure 13.2,. consisted. of. two. main. steps..
First,.a.10.nm.thick.gold.ilm.was.deposited.on.PS.sheets.via.sputtering..In.order.to.prevent.
the.sample.from.shrinking.or.inducing.any.preheating,.the.sputtering.was.divided.into.
four. cycles,. where. 2.5. nm. of. gold. is. deposited. per. cycle.. After. deposition,. the. substrate.
was.heated.at.160°C.for.6.minutes.in.order.to.induce.60%.shrinkage.and.force.the.metal.
ilm.to.collapse,.forming.bimetallic.wrinkles..In.order.to.form.uniaxial.wrinkles,.two.clips.
were.placed.on.the.edges.of.each.of.the.sides.of.the.gold.ilm.and.heated.at.160°C.for.6.
minutes.
The. wrinkles. can. be. further. integrated. into. shrink-induced. polymer. microluidic.
devices.. First,. a. microchannel. was. patterned. by. manual. scribing. on. the. PS. sheet.. Then.
clips.were.attached.on.the.ends.of.the.PS.sheet.and.the.substrate.was.shrunk.by.heating.it.
to.150°C..Once.the.substrate.was.cool,.a.diamond.saw.was.used.to.cut.out.the.center.of.the.
sample..Chips.were.masked.by.placing.adhesive.tape.on.the.surface.of.the.sample.adjacent.
to.the.channel.previously.scribed.into.the.surface..Using.a.dissection.microscope,.tape.was.
10 nm-thick gold
Pre-stressed
polystyrene
Heating
Biaxial wrinkles
Uniaxial wrinkles
FIGURE 13.2
Schematic.of.the.fabrication.of.biaxial.and.uniaxial.metal.wrinkles..Ten.nanometers.of.gold.is.sputtered.on.a.PS.
sheet.and.then.heated.at.160°C.in.an.oven.to.induce.the.buckling.of.the.metal.
