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Featured researches published by Bodo D. Wilts.


Optics Express | 2011

Refractive index and dispersion of butterfly chitin and bird keratin measured by polarizing interference microscopy.

Hein L. Leertouwer; Bodo D. Wilts; Doekele G. Stavenga

Using Jamin-Lebedeff interference microscopy, we measured the wavelength dependence of the refractive index of butterfly wing scales and bird feathers. The refractive index values of the glass scales of the butterfly Graphium sarpedon are, at wavelengths 400, 500 and 600 nm, 1.572, 1.552 and 1.541, and those of the feather barbules of the white goose Anas anas domestica are 1.569, 1.556 and 1.548, respectively. The dispersion spectra of the chitin in the butterfly scales and the keratin in the bird barbules are well described by the Cauchy equation n(λ) = A + B/λ(2), with A = 1.517 and B = 8.80·10(3) nm(2) for the butterfly chitin and A = 1.532 and B = 5.89·10(3) nm(2) for the bird keratin.


Philosophical Transactions of the Royal Society B | 2011

Polarized iridescence of the multilayered elytra of the Japanese jewel beetle, Chrysochroa fulgidissima

Doekele G. Stavenga; Bodo D. Wilts; Hein L. Leertouwer; Takahiko Hariyama

The elytra of the Japanese jewel beetle Chrysochroa fulgidissima are metallic green with purple stripes. Scanning electron microscopy and atomic force microscopy demonstrated that the elytral surface is approximately flat. The accordingly specular green and purple areas have, with normal illumination, 100–150 nm broad reflectance bands, peaking at about 530 and 700 nm. The bands shift progressively towards shorter wavelengths with increasing oblique illumination, and the reflection then becomes highly polarized. Transmission electron microscopy revealed that the epicuticle of the green and purple areas consists of stacks of 16 and 12 layers, respectively. Assuming gradient refractive index values of the layers between 1.6 and 1.7 and applying the classical multilayer theory allowed modelling of the measured polarization- and angle-dependent reflectance spectra. The extreme polarized iridescence exhibited by the elytra of the jewel beetle may have a function in intraspecific recognition.


Journal of the Royal Society Interface | 2009

Imaging scatterometry and microspectrophotometry of lycaenid butterfly wing scales with perforated multilayers.

Bodo D. Wilts; Hein L. Leertouwer; Doekele G. Stavenga

We studied the structural as well as spatial and spectral reflectance characteristics of the wing scales of lycaenid butterfly species, where the scale bodies consist of perforated multilayers. The extent of the spatial scattering profiles was measured with a newly built scatterometer. The width of the reflectance spectra, measured with a microspectrophotometer, decreased with the degree of perforation, in agreement with the calculations based on multilayer theory.


PLOS ONE | 2012

Sexual dichromatism of the damselfly Calopteryx japonica caused by a melanin-chitin multilayer in the male wing veins.

Doekele G. Stavenga; Hein L. Leertouwer; Takahiko Hariyama; Hans De Raedt; Bodo D. Wilts

Mature male Calopteryx japonica damselflies have dark-blue wings, due to darkly coloured wing membranes and blue reflecting veins. The membranes contain a high melanin concentration and the veins have a multilayer of melanin and chitin. Female and immature C. japonica damselflies have brown wings. We have determined the refractive index of melanin by comparing the differently pigmented wing membranes and applying Jamin-Lebedeff interference microscopy. Together with the previously measured refractive index of chitin the blue, structural colour of the male wing veins could be quantitatively explained by an optical multilayer model. The obtained melanin refractive index data will be useful in optical studies on melanized tissues, especially where melanin is concentrated in layers, thus causing iridescence.


Proceedings of the National Academy of Sciences of the United States of America | 2014

Sparkling feather reflections of a bird-of-paradise explained by finite-difference time-domain modeling

Bodo D. Wilts; K. Michielsen; Hans De Raedt; Doekele G. Stavenga

Significance Birds-of-paradise are brilliant examples of colorful displays in nature. The dazzling colors of the display, used in ritualized dances to attract the attention of mates, arise from the interference and diffraction of light within photonic nanostructures on their feathers. This study reports a quantitative investigation of the complex photonic structures by connecting experimental photonics with a state of the art computational model. The methods used in this study may be applied to numerous applications, e.g., for optimized photonic crystal designs. Here it has allowed us to unveil the coloration mechanisms in the feathers of a bird-of-paradise and investigate the connection of feather colors to the avian visual system. Birds-of-paradise are nature’s prime examples of the evolution of color by sexual selection. Their brilliant, structurally colored feathers play a principal role in mating displays. The structural coloration of both the occipital and breast feathers of the bird-of-paradise Lawes’ parotia is produced by melanin rodlets arranged in layers, together acting as interference reflectors. Light reflection by the silvery colored occipital feathers is unidirectional as in a classical multilayer, but the reflection by the richly colored breast feathers is three-directional and extraordinarily complex. Here we show that the reflection properties of both feather types can be quantitatively explained by finite-difference time-domain modeling using realistic feather anatomies and experimentally determined refractive index dispersion values of keratin and melanin. The results elucidate the interplay between avian coloration and vision and indicate tuning of the mating displays to the spectral properties of the avian visual system.


Proceedings of the Royal Society of London. Series B, Biological Sciences | 2012

Brilliant camouflage: photonic crystals in the diamond weevil, Entimus imperialis

Bodo D. Wilts; K. Michielsen; Jeroen Kuipers; Hans De Raedt; Doekele G. Stavenga

The neotropical diamond weevil, Entimus imperialis, is marked by rows of brilliant spots on the overall black elytra. The spots are concave pits with intricate patterns of structural-coloured scales, consisting of large domains of three-dimensional photonic crystals that have a diamond-type structure. Reflectance spectra measured from individual scale domains perfectly match model spectra, calculated with anatomical data and finite-difference time-domain methods. The reflections of single domains are extremely directional (observed with a point source less than 5°), but the special arrangement of the scales in the concave pits significantly broadens the angular distribution of the reflections. The resulting virtually angle-independent green coloration of the weevil closely approximates the colour of a foliaceous background. While the close-distance colourful shininess of E. imperialis may facilitate intersexual recognition, the diffuse green reflectance of the elytra when seen at long-distance provides cryptic camouflage.


Interface Focus | 2012

Iridescence and spectral filtering of the gyroid-type photonic crystals in Parides sesostris wing scales

Bodo D. Wilts; K. Michielsen; Hans De Raedt; Doekele G. Stavenga

The cover scales on the wing of the Emerald-patched Cattleheart butterfly, Parides sesostris, contain gyroid-type biological photonic crystals that brightly reflect green light. A pigment, which absorbs maximally at approximately 395 nm, is immersed predominantly throughout the elaborate upper lamina. This pigment acts as a long-pass filter shaping the reflectance spectrum of the underlying photonic crystals. The additional effect of the filtering is that the spatial distribution of the scale reflectance is approximately angle-independent, leading to a stable wing pattern contrast. The spectral tuning of the original reflectance is verified by photonic band structure modelling.


The Journal of Experimental Biology | 2011

Kingfisher feathers - colouration by pigments, spongy nanostructures and thin films

Doekele G. Stavenga; Jan Tinbergen; Hein L. Leertouwer; Bodo D. Wilts

SUMMARY The colours of the common kingfisher, Alcedo atthis, reside in the barbs of the three main types of feather: the orange breast feathers, the cyan back feathers and the blue tail feathers. Scanning electron microscopy showed that the orange barbs contain small pigment granules. The cyan and blue barbs contain spongy nanostructures with slightly different dimensions, causing different reflectance spectra. Imaging scatterometry showed that the pigmented barbs create a diffuse orange scattering and the spongy barb structures create iridescence. The extent of the angle-dependent light scattering increases with decreasing wavelength. All barbs have a cortical envelope with a thickness of a few micrometres. The reflectance spectra of the cortex of the barbs show oscillations when measured from small areas, but when measured from larger areas the spectra become wavelength independent. This can be directly understood with thin film modelling, assuming a somewhat variable cortex thickness. The cortex reflectance appears to be small but not negligible with respect to the pigmentary and structural barb reflectance.


Journal of the Royal Society Interface | 2012

Hemispherical Brillouin zone imaging of a diamond-type biological photonic crystal

Bodo D. Wilts; K. Michielsen; Hans De Raedt; Doekele G. Stavenga

The brilliant structural body colours of many animals are created by three-dimensional biological photonic crystals that act as wavelength-specific reflectors. Here, we report a study on the vividly coloured scales of the diamond weevil, Entimus imperialis. Electron microscopy identified the chitin and air assemblies inside the scales as domains of a single-network diamond (Fd3m) photonic crystal. We visualized the topology of the first Brillouin zone (FBZ) by imaging scatterometry, and we reconstructed the complete photonic band structure diagram (PBSD) of the chitinous photonic crystal from reflectance spectra. Comparison with calculated PBSDs indeed showed a perfect overlap. The unique method of non-invasive hemispherical imaging of the FBZ provides key insights for the investigation of photonic crystals in the visible wavelength range. The characterized extremely large biophotonic nanostructures of E. imperialis are structurally optimized for high reflectance and may thus be well suited for use as a template for producing novel photonic devices, e.g. through biomimicry or direct infiltration from dielectric material.


Methods | 2014

Gold nanoparticles explore cells : cellular uptake and their use as intracellular probes

Anna Huefner; Dedy Septiadi; Bodo D. Wilts; Imran I. Patel; Wei-Li Kuan; Alexandra Fragniere; Roger A. Barker; Sumeet Mahajan

Understanding uptake of nanomaterials by cells and their use for intracellular sensing is important for studying their interaction and toxicology as well as for obtaining new biological insight. Here, we investigate cellular uptake and intracellular dynamics of gold nanoparticles and demonstrate their use in reporting chemical information from the endocytotic pathway and cytoplasm. The intracellular gold nanoparticles serve as probes for surface-enhanced Raman spectroscopy (SERS) allowing for biochemical characterisation of their local environment. In particular, in this work we compare intracellular SERS using non-functionalised and functionalised nanoparticles in their ability to segregate different but closely related cell phenotypes. The results indicate that functionalised gold nanoparticles are more efficient in distinguishing between different types of cells. Our studies pave the way for understanding the uptake of gold nanoparticles and their utilisation for SERS to give rise to a greater biochemical understanding in cell-based therapies.

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Ilja Gunkel

Lawrence Berkeley National Laboratory

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Ulrich Wiesner

University of South Carolina

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