Biomedical Engineering Reference
In-Depth Information
(A)
(B)
(C)
(D)
FIGURE 13.3
Schematic. of. the. fabrication. of. uniaxial. wrinkles. inside. the. polystyrene-based. microchannel.. (A). A. channel.
was.patterned.on.the.polystyrene.sheet..The.sheet.was.shrunk.unidirectionally..(B).The.edges.of.the.chip.were.
cut.off..(C).A.piece.of.tape.was.used.to.cover.the.surface.on.the.chip.except.for.the.channel..Silver.was.deposited.
into.the.channel.by.sputter.coating..(D).The.tape.was.removed.and.the.chip.was.then.shrunk.to.form.uniaxial.
wrinkles.inside.the.channel.
aligned.until.everything.except.for.the.channel.was.covered..The.chip.was.then.sputter.
coated.with.45.nm.of.silver..After.deposition,.the.tape.was.removed.from.the.surface.and.
the. chip. was. then. shrunk. without. any. constraints. to. form. uniaxial. wrinkles. inside. the.
channel.(Figure 13.3).
The. characterization. of. the. wrinkles. was. done. using. a. scanning. electron. microscope.
(SEM)..SEM.images.were.taken.for.the.biaxial.and.uniaxial.samples.to.conirm.the.wrinkle.
features.(Figure 13.4).
Two-dimensional. fast. Fourier. transform. (FFT). of. the. SEM. images. was. conducted. to.
determine.the.distribution.of.the.wrinkle.wavelengths.as.a.probability.function..The.insets.
of.Figure 13.5A.and.B.indicate.the.2D.FFT.patterns..The.wrinkle.wavelengths.ranged.from.
200.nm.to.1.µm,.with.a.majority.of.the.nanowrinkles.peaking.around.400.nm..To.better.
understand.the.tuning.of.the.wavelength.of.the.wrinkles,.it.was.important.to.irst.under-
stand. how. the. length. scale. of. the. wrinkles. depends. on. the. thickness. of. the. metal. ilm,.
along.with.material.properties..The.thickness.of.deposited.gold.was.varied.from.10.to.50.
nm,.and.Figure 13.6.illustrates.how.the.wrinkles'.wavelength.shifted.in.hundreds.of.nano-
meters,.with.increasing.thickness.for.the.biaxial.samples..For.uniaxial.samples,.a.similar.
trend.was.observed,.except.two.peaks.were.observed.for.the.wrinkle.wavelengths.300.and.
800.nm.(Figure 13.7).
A
B
20 µm
20 µm
FIGURE 13.4
SEM.images.of.gold.(A).biaxial.and.(B).uniaxial.nanowrinkles.on.shrunk.polystyrene.sheets.
