Imaging optical scattering of butterfly wing scales with a microscope

A new optical method is proposed to investigate the reflectance of structurally coloured objects, such as Morpho butterfly wing scales and cholesteric liquid crystals. Using a reflected-light microscope and a digital single-lens reflex (DSLR) camera, we have successfully measured the two-dimensional reflection pattern of individual wing scales of Morpho butterflies. We demonstrate that this method enables us to measure the bidirectional reflectance distribution function (BRDF). The scattering image observed in the back focal plane of the objective is projected onto the camera sensor by inserting a Bertrand lens in the optical path of the microscope. With monochromatic light illumination, we quantify the angle-dependent reflectance spectra from the wing scales of Morpho rhetenor by retrieving the raw signal from the digital camera sensor. We also demonstrate that the polarization-dependent reflection of individual wing scales is readily observed using this method, using the individual wing scales of Morpho cypris . In an effort to show the generality of the method, we used a chiral nematic fluid to illustrate the angle-dependent reflectance as seen by this method.

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Orientation-Dependent Reflection of Structurally Coloured Butterflies

Biomimetics ◽

10.3390/biomimetics5010005 ◽

2020 ◽

Vol 5 (1) ◽

pp. 5

Author(s):

Sigrid Zobl ◽

Bodo D. Wilts ◽

Willi Salvenmoser ◽

Peter Pölt ◽

Ille C. Gebeshuber ◽

...

Keyword(s):

Orientation Dependence ◽

Butterfly Species ◽

Butterfly Wing ◽

Step Size ◽

Photonic Structures ◽

Light Interference ◽

Important Input ◽

Individual Scale ◽

The Individual ◽

Wing Scales

The photonic structures of butterfly wing scales are widely known to cause angle-dependent colours by light interference with nanostructures present in the wing scales. Here, we quantify the relevance of the horizontal alignment of the butterfly wing scales on the wing. The orientation-dependent reflection was measured at four different azimuth angles, with a step size of 90°, for ten samples—two of different areas of the same species—of eight butterfly species of three subfamilies at constant angles of illumination and observation. For the observed species with varying optical structures, the wing typically exhibits higher orientation-dependent reflections than the individual scale. We find that the measured anisotropy is caused by the commonly observed grating structures that can be found on all butterfly wing scales, rather than the local photonic structures. Our results show that the technique employed here can be used to quickly evaluate the orientation-dependence of the reflection and hence provide important input for bio-inspired applications, e.g., to identify whether the respective structure is suitable as a template for nano-imprinting techniques.

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Selective Optical Gas Sensors Using Butterfly Wing Scales Nanostructures

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.543.97 ◽

2013 ◽

Vol 543 ◽

pp. 97-100 ◽

Cited By ~ 3

Author(s):

Krisztián Kertész ◽

Gábor Piszter ◽

Emma Jakab ◽

Zsolt Bálint ◽

Zofia Vértesy ◽

...

Keyword(s):

Gas Sensors ◽

Living Organism ◽

Ambient Atmosphere ◽

Butterfly Wing ◽

Propagation Of Light ◽

Reflected Light ◽

Species Specific ◽

Photonic Band ◽

Blue Coloration ◽

Wing Scales

Photonic crystals are periodic dielectric nanocomposites, which have photonic band gaps that forbid the propagation of light within certain frequency ranges. This property enables one to manipulate light with amazing facility. Such nanoarchitectures frequently occur in living organism like butterflies and beetles. Butterfly scales are particularly well suited to be used as optical gas sensors as their nanoarchitecture is an open sponge-like type, composed of chitin and air. The open nanoarchitecure allows fast gas exchange. The spectral change of the reflected light depends on the composition of the ambient atmosphere and also on the wing nanostructure. In this work we show the results of recent measurements on nine Polyommatine species with dorsal blue coloration. Their color is generated by similar pepper-pot type nanoarchitectures which exhibit species specific characteristics, associated with species specific color. Experiments were carried out changing the concentration and nature of test vapors while monitoring the spectral variations in time. Proper data processing results gas-selective and concentration dependent signals. Our work shows a way to a prospective integrated biological - optical sensor combining light-weight and low power consuming with environmental friendly production.

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