Biomedical Engineering Reference
In-Depth Information
14.3.1.1 Scanning Electron Microscopy
SEM. is. the. most. common. way. to. document. the. electrospun. nanoiber. morphology. and.
determine. iber. diameter.. In. order. to. use. SEM. to. determine. nanoiber. morphology. and.
diameter,. there. are. a. few. simple. preparation. steps.. A. section. of. the. iber. mat. must. be.
secured.to.a.metal.sample.stub.and.sputter-coated.with.gold.(Veleirinho.et.al..2008)..The.
purpose.of.sputter.coating.is.to.create.a.conductive.surface.on.the.ibers..SEM.images.can.
be. taken. at. various. magniications. using. an. accelerating. voltage. at. 5-10.kV.. The. average.
iber.diameter.and.size.distribution.can.be.measured.by.Image.J.1.37c.software.
14.3.1.2 Transmission Electron Microscopy
TEM.is.another.useful.technique.for.observing.nanoiber.morphology.with.great.detail..
Typically,.TEM.requires.extensive.sample.preparation.for.a.biological.specimen..However,.
nanoibers.do.not.need.to.undergo.complex.preparations,.as.they.are.thin.enough.already..
The. only. obligation. is. that. the. nanoibers. need. to. be. collected. onto. carbon-coated. Cu.
grids.(Ma.et.al..2012)..Core-shell.nanoibers.are.observable.using.TEM..For.example,.the.
instrument. was. set. to. 100.kV. for. accelerating. voltage. and. the. core-shell. structure. and.
cross-sections.of.electrospun.alginate/PEO.nanoibers.were.revealed.by.TEM.(Ma.et.al..
2012)..Another.example.is.the.characteristic.D-repeat.banding.pattern.on.electrospun.col-
lagen.nanoibers,.conirming.the.feasibility.of.faithfully.mimicking.the.native.collagenous.
structure.using.electrospun.collagen.nanoibers.(Matthews.et.al..2002).
14.3.1.3 Atomic Force Microscopy
AFM.is.the.third.way.to.characterize.the.morphology.of.nanoibers,.which.is.able.to.pro-
vide.information.of.nanoiber.morphology,.topography,.and.roughness.as.well.as.mechan-
ical. properties,. which. will. be. described. in. Section. 14.3.3.. Jaeger. et. al.. (1996). used. AFM.
to.examine.PEO.nanoibers.and.generated.the.nanograph.of.the.nanoiber.surface.using.
height.mode.or.friction.mode,.showing.PEO.macromolecular.helices.on.the.angstrom.scale..
Zussman.et.al..(2003).were.able.to.measure.the.maximum.height.at.each.cross-section.and.
therefore,.ind.the.failure-associated.necking.of.electrospun.PEO.nanoibers.
Surface.topography.can.be.imaged.using.the.phase.imaging.mode.on.the.AFM.(Lim.et.al..
2008)..We.have.successfully.observed.the.surface.topography.of.alginate/PEO.nanoibers.
as. shown. in. Figure. 14.5.. To. be. more. speciic,. Chen. and. Su. (2011). used. AFM. in. order. to.
image.the.surface.topography.of.electrospun.PLLA.nanoibers.with.surface.modiications..
They.chose.a.scan.size.of.10.×.10.μm
2
,.a.scan.rate.of.0.8.Hz,.and.a.sampling.number.of.256..
From. this,. they. were. able. to. determine. the. relative. roughness. of. the. PLLA. nanoibers.
before.and.after.surface.modiications.(Chen.and.Su.2011).
14.3.2 Porosity
14.3.2.1 Based on Apparent Density by Weight Measurement
Porosity. is. one. of. the. important. characteristics. of. electrospun. nanoibers,. which. can. be.
determined.by.the.following.equation:
×
100%
.
−
Apparent density of the mat
Bulk density of polymer
Porosity
=
1
(14.1)
.
