AbstractNatural photonic structures found in living organisms consist in very sophisticated materials, developed during millions of years through natural evolution. When they interact with light, they give rise to astonishing visual effects. Beetles' elytra as well as butterflies' wings are among the most striking examples. The structures found on these insects are porous and composed of one single biopolymer, i.e. chitin and air.
In the framework of this Ph.D. thesis, two remarkable properties of these photonic structures were investigated: additive colours due to optical multi-scale effects of a photonic polycrystal and changes of optical properties induced by fluids.
Firstly, the dull colour created by a photonic polycrystal found on the elytra of the Brazilian Entimus imperialis beetle was studied. This polycrystal is composed of iridescent domains characterised by different orientations of one single three-dimensional photonic crystal. The disorder in the juxtaposed domain orientations leads to a dull non iridescent colour.
Secondly, colour and fluorescence emission changes induced in the male Hoplia coerulea beetle by contact with different liquids were analysed. Inside the scales covering the insect's elytra, a porous multilayer is enclosed by a thin envelope preventing direct contact with the liquids. Various dynamics were observed and explained by different permeabilities of chitin to the liquids and the presence of salts inside chitin.
Finally, colour modifications in the open structures of butterflies' wings induced by gases and vapours were studied and modelled analytically as well as numerically. These modifications were experimentally highlighted in the case of H. coerulea and numerically explained thanks to different combined effects.
The observation and understanding of phenomena found in nature such as additive and induced colours that were investigated in the framework of this Ph.D. thesis can lead to the development of novel materials through biomimetics and bioinspiration.
|Date of Award||29 Sep 2015|
|Sponsors||Fonds de la Recherche Scientifique F.R.S.-FNRS|
|Supervisor||Olivier DEPARIS (Supervisor), BAO LIAN SU (Jury), Muriel Lepere (President), Peter Vukusic (Jury), Serge Berthier (Jury) & Michel Voué (Jury)|
- Photonic crystals
- Natural photonic crystal
- Interferential color
- Structural colours
- Numerical method
- Additive colours
- Induced colours