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7BUTTERFLIES- COLOR AND CONCEPT

Presented by :

Shanti Kumari

Entry no. : 2013TTF2771

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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.

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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.

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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.

Optical phenomena of structural colors

Diffraction grating effect

Thin film interference

Multilayer interference

Photonic crystals

Light scattering

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.

Incident ray

Diff

racted

spectru

m

Structure of wings showing diffraction grating effect

Scales

Ridges

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Basic structure and parts of butterfly wings

100

micro

met

res

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.

Incident rayRe

flect

ed

rays

n2

n1

{t

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

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.

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

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

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.

Incide

nt li

ght

Scat

tere

dlig

ht

Fig : SEM images of iridescent scales of licaenid butterflies. a,b) Narathura japonica and c,d) elastrina argiolus ladonides

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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.

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.

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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.

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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

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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.

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 butterfl ies − 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 Butterfl ies 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, Butterfl ies, Birds, and Moths”, Chem. Rev. 99, 1935-1961 (1999).

Boris Gralak, Gérard Tayeb and Stefan Enoch, “Morpho butterfl ies wings color modeled with lamellar grating theory”, Optics Express Vol. 9, No. 11 567 (2001).

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