Biomedical Engineering Reference
In-Depth Information
and.experimented.with.ways.of.mimicking.butterly.wings.to.generate.structural.colors.
(Saito.2011)..As.described.in.Section.9.3,.scientists.can.replicate.the.photonic.effect.of.the.
Morpho
. wings. using. various. nanofabrication. approaches. to. the. replication. of. their. hier-
archical. structures.. One. such. method. is. to. use. electron. beam. lithography. and. various.
etchings.to.create.a.ridge.structure.and.tree-like.cross.section..The.angle.of.these.artiicial.
“scales”. could. be. controlled,. changing. the. color. that. is. seen. by. an. observer,. and. caus-
ing. the. “scales”. to. act. like. “pixels”. of. color. (Coath. 2007,. Saito. et. al.. 2009).. Using. nano-
casting.lithography,.colloidal.spheres.in.an.elastomer.can.stretch.or.compress.to.change.
the.distance.between.the.spheres,.allowing.a.multitude.of.colors.to.be.relected,.which.is.
extremely.useful.for.developing.display.technology.(Song.et.al..2011)..Another.technique.
is.to.change.the.index.of.refraction.of.the.incident.medium,.in.a.way.similar.to.putting.a.
drop.of.alcohol.on.the.wing.of.a.
Morpho
.butterly.that.results.in.alcohol.replacing.the.air.
pockets.in.the.wings.and.changing.the.color.of.the.wings.(Liu.et.al..2011)..One.application.
of.this.technology.is.a.color.display.(such.as.for.laptops,.phones,.TVs,.and.other.devices)..A.
major.beneit.of.using.this.technology.is.that.little.power.is.required.to.operate.it..A.light.
source. is. only. required. in. dark. conditions. because. the. scales. relect. outside. light. rather.
than.emitting.their.own.light.
As.biology.has.constructed.an.elaborate.nanostructure.that.can.produce.beautiful.opti-
cal.phenomena,.researchers.at.Qualcomm.have.implemented.this.technology.to.develop.
low-energy.displays.for.consumer's.e-readers,.so-called.Mirasol.displays..The.Mirasol.dis-
plays.are.based.on.interferometric.modulation.(IMOD).technology.that.consists.of.mirrors.
and.an.optical.resonant.cavity.to.use.relected.light.as.displays.in.e-readers.(Qualcomm.
2011)..The.device.is.a.deformable.relective.membrane,.which.serves.as.an.optical.resonant.
cavity. and. has. a. thin-ilm. stack. that. uses. multilayer. interference. to. mirror. the. ambient.
light..The.thickness.of.the.optical.cavity.can.be.changed.by.applying.a.small.voltage..The.
thickness,.depending.on.the.phase.difference,.can.cause.certain.wavelengths.to.undergo.
constructive. interference. while. causing. others. to. undergo. destructive. interference.. An.
IMOD.structure,.which.causes.red.wavelengths.to.constructively.interfere.and.green.and.
blue.wavelengths.to.destructively.interfere,.will.cause.the.viewer.to.see.a.red.pixel..This.
design. produces. a. new. palette. of. colors. compared. to. light. emitting. diodes. (LEDs). and.
consumes.little.power.to.change.only.the.membrane.structure.instead.of.color.ilters.and.
polarizers.
Currently,. the. most. used. technology. for. e-readers. is. liquid. crystal. displays. (LCDs),.
which.consume.a.signiicant.amount.of.power.continuously.and.have.poor.outdoor.view.
ability..The.other.popular.design.common.with.Amazon.e-readers.is.the.electrophoretic.
displays,.which.are.more.eficient,.but.lack.color.and.have.a.slow.refresh.rates..Compared.
to. these. display. technologies,. IMOD-based. Mirasol. displays. consume. less. power,. show.
more.vibrant.colors.with.greater.contrast.ratios,.and.have.a.faster.refresh.rate..For.example,.
the.drive.voltages.of.IMOD.is.less.than.5.V.compared.to.Kycoera's.LCD.displays.in.phone.
that.requires.about.27-30.V.to.drive.their.subpixel.(http://americas.kyocera.com/kicc/lcd/
notes/lcdvoltage.html),. and. the. refresh. rate. of. IMOD. is. about. 10.μs. compared. to. whole.
seconds.of.electrophoretic.technology.(Qualcomm.2011).
Similar.to.the.Qualcommb's.electronic.displays,.nanostructures.and.optical.features.of.
the.
Morpho
.butterly.wing.are.being.studied.for.developing.anticounterfeiting.technology.
in.security.applications..Currency.makers.use.plasmonics.to.create.iridescent.markings.to.
curb.counterfeiting..The.structures.are.nanoscale.holes.that.resonate.with.light,.similar.to.
the.veins.of.the.butterly.wing..Since.the.nanostructure.creates.unique.optical.features,.the.
structures.can.be.slightly.modiied.so.they.can.be.used.as.identiication.tags..These.tags.
can.be.descriptive.and.prevent.counterfeiting.
