Biomedical Engineering Reference
In-Depth Information
Polymer solution
Fiber formation
Capillary tip
High voltage
Fiber mat
Counter electrode
Figure 14.1
(See companion CD for color igure.)
.Schematic.of.the.electrospinning.setup.
supply,. and. a. grounded. collector,. as. shown. in. Figure. 14.1.. The. polymer. solution. is.
contained.within.a.syringe,.which.is.then.loaded.into.a.syringe.pump.and.attached.to.
a. millimeter-sized. needle. tip.. By. using. a. syringe. pump,. the. solution. can. be. controlled.
to.low.at.a.certain.rate.(depending.upon.the.solution)..Initially,.there.is.a.drop.at.the.tip.
when.the.solution.is.fed,.due.to.surface.tension.forces..However,.as.the.voltage.is.applied,.
the.suspension.will.experience.electrostatic.repulsion.between.the.surface.charges.and.
a.Coulombic.force.from.the.applied.electric.ield.(Theron.et.al..2005,.Reneker.and.Yasin.
2008)..It.is.these.forces.that.cause.the.drop.to.disigure.and.form.the.Taylor.cone.(Taylor.
1969,.Bognitzki.et.al..2001,.Theron.et.al..2004,.Subbiah.et.al..2005)..One.can.image.this.as.
the. drop. being. stretched. into. a. conical. shape.. As. the. electrostatic. forces. overcome. the.
surface.tension.of.the.polymer.solution,.the.liquid.jet.is.discharged.and.electrospinning.
has. begun. (Dzenis. 2004,. McKee. et. al.. 2006).. Thin. ibers. are. formed. as. a. result. of. a.
continuous. stretching. and. whipping. process,. during. which. the. solvent. is. evaporated.
(Demir. et. al.. 2002,. Shenoy. et. al.. 2005,. Szuromi. 2010).. It. is. this. elongation. that. allows.
for.diameters.down.to.tens.of.nanometers..Another.interesting.aspect.of.this.protracted.
stream.is.the.potential.to.simultaneously.stretch.molecules.within.the.solution,.such.as.
DNA.(Bellan.et.al..2006)..Fridrikh.et.al..have.predicted.that.the.inal.diameter.of.the.luid.
jet.resulted.from.a.force.balance.between.surface.tension.and.surface.charge.repulsion,.
which. could. be. determined. by. the. surface. tension. of. the. luid,. low. rate,. and. electric.
current.(Fridrikh.et.al..2003).
The.mechanism.of.action.for.electrospinning.is.slightly.more.complex.than.the.simple.
apparatus. discussed. previously.. It. is. often. explained. in. terms. of. electrohydrodynamics.
(the.interactions.of.luid.low.and.electric.ield).(Angammana.and.Jayaram.2011)..Basically,.
