Biomedical Engineering Reference
In-Depth Information
(a)
(b)
(c)
(d)
(e)
(f )
FIGURE 25.5
(a).
Ancyluris meliboeus
.has.highly.iridescent.blue.scales.that.“lash”.when.observed.at.a.shallow.angle.behind.the.
butterly..(b).SEM.image.of.a.scale.from.
A. meliboeus
.demonstrating.the.rows.of.plates.along.the.scale..(c).Side-
view.SEM.showing.the.separation.between.the.plates..(d).The.butterly.
Hypolimnas bolina
.has.a.region.around.
the.white.spots.where.there.are.iridescent.scales.that.display.a.low-angle.violet.relection..(e).SEM.images.again.
show.that.there.are.rows.of.plates.on.the.scales..(f).The.separations.between.these.create.a.shallow-angle.multi-
layer.effect.similar.to.that.of.
A. meliboeus
..Scale.bars:.20.mm.(a,.d),.3.μm.(b,.e),.700.nm.(c),.2.μm.(f).
an.angle.at.which.the.iridescence.is.not.observed..Single.scale.measurements.and.optical.
imagery.show.that.for.120°.in.the.axis.parallel.to.the.ridges,.there.is.a.strong.iridescence.
showing.a.wide.range.of.hues,.from.blue.to.orange.
19,20
This.form.of.scales.is.also.found.on.the.male.
Hypolimnas bolina
..The.butterly.is.predomi-
nantly. black. with. four. white. spots,. one. on. each. wing,. with. the. iridescent. scales. located.
around.the.edges.of.the.white.spots..The.scales.are.not.visible.from.normal.incidence.and.
display.a.purple.hue.at.lower.angles.in.one.direction..The.scales.responsible.for.this.color.
have. ridges. similar. to. those. observed. in.
Ancyluris meliboeus
,. with. a. periodicity. along. the.
scales.of.around.600.nm.
21
.The.periodicity.perpendicular.to.the.lamellae.is.around.120.nm,.
with.the.lamellae.themselves.averaging.around.50.nm.thick,.with.the.separation.being.main-
tained.by.interlamella.spacers.that.do.not.extend.across.the.entire.width.of.the.lamellae.
21
The.most.extreme.example.of.these.types.of.scales.is.found.on.the.yellow.and.black.but-
terly.
Troides magellanus
,.the.yellow.regions.of.which.lash.a.blue-green.color.when.viewed.
from. the. outermost. edge. at. near-grazing. incidence.. The. iridescent. scales. have. ridges.
around. 2.2. μm. high,. with. lamellae. running. from. the. base. to. the. top. at. an. angle. of. 36°.
from.normal.to.the.scale.base.layer..These.lamellae.form.a.multilayer.with.a.periodicity.of.
approximately.260.nm.when.viewed.at.near-grazing.incidence.
22
25.1.5
Papilio zalmoxis
and
Papilio nireus
—Nature's OLEDs
While.many.of.these.structures.have.intricate.designs.that.can.demonstrate.simple.prin-
ciples,.perhaps.the.most.amazing.is.when.the.structures.are.combined.to.great.effect..The.
butterly.
Papilio zalmoxis
.was.often.held.to.be.an.example.of.Tyndall.scattering,.a.system.by.
which.shorter.wavelengths.are.more.preferentially.coherently.scattered.than.lower.wave-
lengths.by.small.particles,.thereby.resulting.in.the.separation.of.different.wavelengths.of.
