2. Introduction
Butterflies are one of the most
beautiful creatures of nature
spreading positive vibes by flipping
its colorful wings.
The butterfly flutters about in many
different colors.
They use their bright colors to ward
off predators by tricking them into
thinking they are poisonous (some
actually are) or by camouflaging
themselves into plants or bigger
insects.
3. Myth
Butterfly wings are all colorful due
to pigmentation.
Fact
The colorful wings are an attribute
of structural colors produced upon
interaction of complex
microstructures in scales of wings
with sunlight, sometimes in
combination with pigments.
4. What are structural
colors?
Structural colors, also
known as
schemochromes, are
the effect of
interaction of light
with microscopically
structured surfaces
fine enough to
interfere with visible
light, sometimes in
combination with
pigments.
6. Diffraction Grating Effect
A diffraction grating is any nano
scale array of parallel ridges or
slits that disperses white light
into its constituent wavelengths.
Required conditions :
Repeating surface pattern
Pattern size in range of
wavelength of incident light.
9. Thin – film Interference
As light strikes the surface of a film it is either transmitted or
reflected at the upper surface.
Light that is transmitted reaches the bottom surface and may
once again be transmitted or reflected.
The light reflected from the upper and lower surfaces will
interfere. The degree of constructive or destructive interferences
between the two light waves depends on the difference in their
phase.
n2
n1
{t
10. Thin film interference
Destructive Interference
Constructive Interference
If n2 < n1 and
2n2 t + λ1/2 = m λ1 , (m = 1, 2, 3, …)
Constructive Interference
2n2 t + λ1/2 = (m +1/2 )λ1 , (m = 1, 2, 3, …)
Destructive Interference
11. Multilayer Interference
It is an extension of single-layer
interference.
The color reflected by a multilayer
structure depends on the refractive index
of the component layers and their
periodicity.
The multilayer stack is composed of
alternate layers ridges and air spaces of
identical high index and low index
respectively.
Multiple reflections in the region of
observer increase the total reflected
intensity.
12. Multilayer interference -
Iridescence
Change in the angle of observation changes the path
length of reflected light through the multilayer medium,
which ultimately changes the wavelength for
constructive interference and hence the apparent color
of reflector varies. This effect is known as Iridescence.
Blue shift Red shift
ø
13. Photonic Crystals
If small identical particles are regularly
arranged like a crystal, light scattered from
each particle interferes and radiates emission in
regular directions.
Fig : SEM images of Photonic crystals found butterfly scales
of (a) Teinopalpus imperialis (b) Mitoura grynea
14. Light Scattering
Butterfly wings are layers
of wrinkled planes as in
Eumaeus minijas, or
planes with holes as in
Ancema blanka and so on.
These irregular structures
results in scattering of
light.
Scattered light after
getting enforced by
diffraction though holes or
wrinkles produces diffused
light pattern. Fig : SEM images of iridescent
scales of licaenid butterflies. a,b)
Narathura japonica and c,d)
elastrina argiolus ladonides
15. Functions of structural
colors in butterflies
Thermal regulation
Signaling
Creating camouflage
Butterflies also use such bright colors
to ward off the predators pretending
themselves to be poisonous.
16. Biomimetics
Such a wonderful color concept of
butterfly wings can be efficiently
used for industrial applications.
From the dawn of civilization
structural colors are being used
in ornamentation and decoration
of accessories.
‘Pearl pigment’, ‘optically
variable pigments’ are some of
the modified pigment based on
structural color principle having
growing market demand.
17. Structural colors in
Textiles
Structural colors possess a potential
to bring about a Green revolution in
textile industry.
Being able to develop wing like micro
and nanostructures on the textile
surface, we will be able to color it
without using dyeing agent, which
will result in no water, no effluent
and zero waste process.
18. Contd…
Till date, invention of
PET fiber (flat shape,
thickness – 15 – 17um)
in which 61 layers of
nylon 6 and polyester
with a thickness of 70–
90 nm are incorporated
has be great success.
A wedding dress has also
been woven with this
fibre. Figure : a) SEM image of the cross-
section of a flattened polyester fiber
mimicking Morpho butterfly. b) The
fiber
19. Conclusion
The bright colors of butterflies are
results of complex interaction of
micro and nano structure of butterfly
wings with light, sometimes in
combination with pigments.
This unique phenomena of nature
unlocks a better way of coloring
matter which can give 100% efficiency
with no waste.
20. References
Shuichi Kinoshita and Shinya Yoshioka, “Structural Colors in Nature: The Role
of Regularity and Irregularity in the Structure”, ChemPhysChem, 6, 1442 –
1459 (2005).
Z. Verstesy, Zs. Baliant, K. Kertesz, J.P.Vigneron, V. Lousse and L.P. Biro,
“Wing scale microstructures and nanostructures in butterflies − natural
photonic crystals”, Journal of Microscopy, Vol. 224, Pt 1, pp. 108–110 (2006).
Ainsley E Seago, Parrish Brady, Jean-Pol Vigneron and Tom D Schultz, “Gold
bugs and beyond: a review of iridescence and structural color mechanisms in
beetles (Coleoptera)”, Journal of the Royal Soceity Interface 6, S165–S184
(2009).
Filip Mika , Jiřina Matějková-Plšková , Suratwadee Jiwajinda, Punyavee
Dechkrong and Makoto Shiojiri, “Photonic Crystal Structure and Coloration of
Wing Scales of Butterflies Exhibiting Selective Wavelength Iridescence”,
Materials, 5, 754-771 (2012).
S Kinoshita, S Yoshioka and J Miyazaki, “Physics of structural colors”, Reports
on Progress of Physics 71 076401 (2008).
Mohan Srinivasarao, “Nano-Optics in the Biological World: Beetles, Butterflies,
Birds, and Moths”, Chem. Rev. 99, 1935-1961 (1999).
Boris Gralak, Gérard Tayeb and Stefan Enoch, “Morpho butterflies wings color
modeled with lamellar grating theory”, Optics Express Vol. 9, No. 11 567
(2001).