Biomedical Engineering Reference
In-Depth Information
Polymer solution
Needle
Syringe pump
+
High voltage
Collector
screen
Ground
FIGURE 23.1
Schematic.drawing.of.electrospinning.apparatus.
23.2.1 Process Parameters
Despite.the.electrospinning.technique's.relative.ease.of.use,.there.are.a.number.of.process.
parameters.that.can.greatly.affect.iber.formation.and.structure..Grouped.in.order.of.rela-
tive.impact.to.the.electrospinning.process,.they.are.the.applied.voltage,.polymer.low.rate,.
and.capillary-collector.distance..All.three.parameters.can.inluence.the.formation.of.bead.
defect.nanoibers.
23.2.1.1 Applied Voltage
The.iber.diameters.can.be.controlled.by.the.applied.voltage,.of.which.the.achieved.results.
vary.strongly.with.the.polymer.system..The.strength.of.the.applied.electric.ield.controls.
formation.of.ibers.from.several.microns.in.diameter.to.tens.of.nanometers..Suboptimal.
ield.strength.could.lead.to.bead.defects.in.the.electrospun.ibers,.or.even.failure.in.jet.
formation..Based.on.previous.work,
34,35
.it.is.evident.that.there.is.an.optimal.range.of.elec-
tric.ield.strengths.for.a.certain.polymer-solvent.system,.as.either.too.weak.or.too.strong.a.
ield.will.lead.to.the.formation.of.beaded.ibers.
23.2.1.2 Polymer Flow Rate
Polymer. low. rate. also. has. an. impact. on. iber. size,. and. additionally. can. inluence. iber.
porosity. as. well. as. iber. shape.
36-38
. Also,. at. high. low. rates,. signiicant. amounts. of. bead.
defects.are.noticeable,.due.to.the.inability.of.ibers.to.dry.completely.before.reaching.the.
collector..Incomplete.iber.drying.also.leads.to.the.formation.of.ribbon-like.(or.lattened).
ibers,.compared.to.ibers.with.a.circular.cross.section.
36,39
23.2.1.3 Capillary-Collector Distance
While.playing.a.much.smaller.role,.the.distance.between.capillary.tip.and.collector.can.
also. inluence. iber. size.. The. iber. diameter. decreased. with. increasing. distances. from.
