Biomedical Engineering Reference
In-Depth Information
biological.molecules.for.tissue.engineering.(Pique.et.al..1999;.Chrisey.et.al..2000;.Schiele.
et. al.. 2010).. They. all. share. similar. experimental. setups,. utilizing. a. laser,. beam. delivery.
optics,.stages.holding.the.transfer.material.on.the.print.ribbon,.and.the.receiving.substrate.
on.which.it.will.be.deposited..The.laser.excites.a.matrix.material.or.a.dynamic.release.layer.
(DRL).and.the.solute.material.is.deposited.as.a.ilm.on.the.print.ribbon..This.excitation.of.the.
matrix.or.DRL.leads.to.the.desorption.and.transfer.of.material.onto.the.receiving.substrate..
Note.that.the.target.and.transfer.materials.may.be.one.and.the.same,.or.they.need.not.be..
The.target.material.is.that.with.which.the.laser.interacts,.and.the.transfer.material.is.that.
which.is.desorbed.from.the.ribbon.to.the.substrate..The.high.power.and.short.penetration.
depth. of. the. laser. exposure. limits. heating. of. transfer. to. a. local. volume,. thus. reducing.
possible.thermal.damage..Beam.delivery.optics.is.not.only.used.to.manipulate.and.deliver.
the.laser.beam.to.the.ribbon,.but.also.to.control.spot.size.and.luence..The.beam.delivery.
optics.consists.of.apertures,.mirrors,.and.series.of.attenuators.and.masks.for.controlling.
the.intensity.and.energy.proile.of.the.pulse..Combined.with.a.partially.relective.mirror,.
an.energy.meter.is.used.to.measure.the.laser.pulse.energy..The.energy.meter.is.used.to.
better.understand.each.individual.transfer.in.terms.of.precision.and.accuracy..Ideally,.the.
spot. size. and. luence. remains. consistent. throughout. the. laser. direct-write. patterning. to.
ensure.that.the.transfer.remains.consistent..The.stages.for.the.print.ribbon.and.substrate.
can. be. automated. and. motorized. to. allow. for. maximum. repeatability. and. for. precise.
BDO
Laser
Transfer
Material
Print ribbon
Receiving substrate
Automated stage
Figure 13.1
General.schematic.of.the.laser.direct-write.experimental.setup..Laser—generates.a.pulse.of.coherent.light.that.
will.excite.the.target.material..Beam.delivery.optics—used.to.direct.the.laser.beam.to.the.ribbon..It.also.is.used.
to.measure.and.control.the.laser.beam.energy,.proile,.spot.size,.and.focus..The.components.typically.include.
an.attenuator,.focus.control,.screen,.as.well.as.a.beam.splitter.and.energy.meter.used.to.measure.beam.energy..
Objective.lens—the.inal.focusing.optic.for.the.pulsed-laser.beam..Ribbon.stage—used.to.allow.for.the.selection.
of.target.material,.especially.important.with.heterogeneous.target.materials,.such.as.cells.and.microbeads,.may.
be.automated..Ribbon—a.laser.transparent.support.for.the.target.material..Substrate.stage—when.used.with.an.
automated.translation,.the.stage.allows.the.computer-controlled.placement.of.transfer.material..Substrate—the.
substrate.receives.the.transferred.material.
