Biomedical Engineering Reference
In-Depth Information
factor. to. allow. for. optimal. transfer. conditions.. Laser. spot. size. and. luence. are. critical.
factors.that.determine.the.amount.of.material.transferred.and.permit.selection.of.even.
speciic.cells.(Hosokawa.et.al..2004;.Barron.et.al..2005a)..Opinions.vary.over.which.strat-
egy.is.most.effective.when.printing.biomaterials..Some.suggest.that.minimum.luence.
for.transfer.will.optimize.viability.and.print.resolution,.while.others.suggest.a.shorter.
separation. between. print. ribbon. and. receiving. substrate. that. utilizes. a. subthreshold.
bubble.that.contacts.the.receiving.substrate..Further.investigation.will.be.required.to.test.
the. validity. of. both. schemes. for. different. materials.. Impressive. demonstrations. of. the.
possible. resolution. have. been. made.. Microarrays. of. DNA. derived. from. salmon. sperm.
were. printed. into. 55-65.μm. diameter. spots. (Fernandezpradas. 2004).. Later. studies. cre-
ated.DNA.microarrays.with.spot.diameters.as.small.as.40.μm.(Serra.et.al..2004)..Varying.
the.luence.affected.the.spot.size.with.rabbit.IgG.solutions..At.the.energy.threshold.for.
transfer,. the. spot. size. was. minimized. to. 25.μm. in. diameter. (Duocastella. et. al.. 2008)..
In. AFA-LIFT,. higher. luence. increased. droplet. size,. whereas. thicker. absorbing. ilms.
decreased. droplet. size.. As. well,. trials. with. AFA-LIFT. demonstrated. that. some. of. the.
sacriicial.target.absorption.layer.is.transferred.with.the.transfer.material..An.increase.in.
laser.luence.caused.a.decrease.in.ilm.particle.size,.while.thicker.layers.tended.to.yield.
larger. particles.. BioLP. has. the. capability. to. print. aliquots. with. 2.5. times. smaller. spot.
sizes.and.200.times.smaller.volumes.than.piezo-tip.printers,.which.are.the.current.best.
in. industry.. These. printing. methods. have. also. been. used. to. print. single. cells.. Further.
gains.in.resolution.are.expected.with.the.optimization.of.laser.spot.diameter.and.print.
ilm.thickness.(Table.13.1).
13.4 Selected Examples of Laser Direct-Written Patterns
Current.laser.direct-write.research.has.made.signiicant.strides.(Figure.13.3)..Metals.have.
been.printed.into.a.variety.of.conigurations.as.complex.as.circuit.elements.like.resistors.
and.capacitors.(Chrisey.et.al..2000)..DNA,.proteins,.and.cells.have.also.all.been.success-
fully.printed..There.have.also.been.initial.successes.with.assembling.biological.constructs.
with.long-range.structures.(Gaebel.et.al..2011)..This.is.a.promising.irst.step.toward.engi-
neering.functional.tissues.because.real.biological.systems.depend.on.structural.features.
as.well.as.chemical.functionality.
13.4.1 electronics/inorganic Materials
Laser.direct-writing.presents.a.unique.opportunity.for.printing.of.inorganic.materials..It.
has.demonstrated.the.creation.of.working.circuit.elements.with.resolution.below.10.μm,.
and.electrical.properties.similar.to.or.superior.to.common.industrial.processes.(Zergioti.
et.al..1998)..Additionally,.laser.direct-writing.is.highly.convenient,.as.it.can.be.done.under.
standard. atmosphere. and. temperature.. Cr. layers. with. thicknesses. of. 100,. 80,. and. 40.nm.
have. been. transferred,. and. the. thinner. layers. transferred. properly. with. lower. luences..
A.lower.luence.is.desirable.as.it.minimizes.thermal.effects,.material.damage,.and.trail-
ing.beam.melting.effects.on.the.receiving.substrate..Cu.deposition.studies.revealed.that.
thinner. ilms. enabled. lower. laser. power. and. gave. better. deposition.. Lengths. of. 50.μm.
wide. lines. were. produced. with. 0.41.μm. thick. ilms.. Cr. and. In
2
O
3
. deposition. have. been.
achieved. over. a. wide. range. of. energy. densities. (Esrom. et. al.. 1995;. Zergioti. et. al.. 2000)..
