Biomedical Engineering Reference
In-Depth Information
9.1 Introduction
Nature.is.the.best.template.for.nanostructures.and.nanotechnologies,.which.manipulates.
hierarchical.structures.at.the.nanoscale.and.assembles.them.into.elaborate.and.complex.
systems.. These. versatile. hierarchical. structures. possess. unique. properties. that. enable.
diverse. functions. in. living. systems.. We. can. create. biomimetic. structures. and. products.
from.what.we.have.observed.in.nature..For.example,.hierarchical.structures.of.lotus.leaves.
have.inspired.researchers.to.create.superhydrophobic.structures.and.self-cleaning.prod-
ucts;. gecko. feet. have. inspired. scientists. to. create. nonstick. bioadhesives,. and. butterly.
wings.have.inspired.engineers.to.create.photonic.structures.for.displays.and.biosensors.
(Liu.and.Jiang.2011).
Butterly. wings. are. lightweight,. mechanically. strong,. hydrophobic,. thermally. respon-
sive,.and,.in.particular,.exhibit.structural.color.due.to.the.elaborated.photonic.nanostruc-
tures.in.their.scales..Butterlies.possess.some.of.the.most.striking.color.displays.found.in.
nature..With.advancement.in.nanotechnology,.the.ield.of.biomimetics.has.recently.begun.
to. implement. the.
Morpho
. structural. color. to. develop. photonic. sensors,. energy. eficient.
electronic.display.screens,.solar.panels,.and.other.photonic.crystal-based.devices.
This.chapter.will.use.butterly-inspired.nanotechnology.as.a.good.example.to.demon-
strate.how.the.hierarchical.architecture.of.a.butterly.wing.affects.the.photonic.function.
at.nanoscale,.how.natural.nanostructures.inspire.the.design.and.fabrication.of.biomimetic.
photonic.structures,.and.what.the.current.and.future.applications.of.the.butterly.wing-
inspired.nanotechnology.are.
9.2 Natural Butterfly Wings
9.2.1 Hierarchical Architectures of Butterfly Wings
The.striking.blue.wings.of.the.blue.
Morpho
.butterly.(as.shown.in.Figure.9.1).are.adored.
by.artists.and.collectors.worldwide.for.their.beautiful.appearance..Scientists,.however,.are.
interested.in.the.butterly.wings.for.a.less.apparent.reason.(Huang.et.al..2006)..The.blue.
color.of.the.butterly's.wings.is.not.caused.by.the.pigmentation.commonly.encountered.in.
nature.but.because.of.the.result.of.physical.phenomena,.which.is.called.structural.color.or.
iridescence.(Vukusic.et.al..2000,.Kinoshita.and.Yoshioka.2005)..Although.the.nanostruc-
ture. varies. among. different. butterly. species,. there. are. some. general. characteristics.. All.
butterly.wings.are.made.of.nearly.transparent.cuticle.proteins.and.chitin,.and.exhibit.a.
hierarchical.structure,.in.which.overlapping.microscale.butterly.wing.scales.are.covered.
with.nanoscale.veins..This.architecture.gives.butterly.wings.a.superhydrophobic.surface..
This.surface.is.essential.since.the.
Morpho
.butterly.lives.in.the.rainforest,.but.more.impor-
tantly.it.gives.rise.to.the.butterly's.iridescent.property.(Watanabe.et.al..2005b).
Huang. et. al.. have. reported. the. typical. structure. of. a. natural.
Morpho Peleides
. butterly.
wing.(Huang.et.al..2006)..In.general,.the.wing.scale.is.∼150.μm.in.length.and.∼60.μm.in.
width..It.consists.of.two.layers,.which.are.linked.by.pillars..The.undersurface.of.each.scale.
is.smooth.and.lacks.structure..The.upper.surface.is.formed.by.a.large.number.of.elongated,.
parallel.ridges/lamellae.(Figure.9.1b)..On.the.surface.of.the.scale.there.are.35-40.rows.of.
lamellas.aligned.with.a.nearly.identical.interspacing.(roughly.1-2.μm.from.each.other)..As.
shown.in.Figure.9.1d,.the.lamellae.are.supported.by.cylindrical.veins,.which.are.∼1.6.μm.in.
