! Dernière minute ! Séminaire annulé / Cancelled Seminar

Structural colors and bioinspirations

Par Gonzague Agez, Centre d’Elaboration des Matériaux et d’Etudes Structurales (CEMES), Université de Toulouse

Mardi 9 juillet,  14h00, Salle des séminaires (215), 2ème étage, Bâtiment A4N

Abstract :

Nature is full of colors, some are due to specific pigments, others are the product of more complex interactions between ambient light and self-organized structures at the nanometer scale : they are called structural colors. These structures result from a long evolutionary process and their biological functions are not always elucidated: camouflage, deterrence, thermal regulation or simply aesthetic ? Many questions remain opened.
Advances in imaging, optical characterizations and nano-fabrications have allowed scientists to replicate these millennial structures. I will present an overview of the diversity of natural photonic structures observed in the plant and animal kingdoms and in what way they are sources of inspiration for the conception of advanced photonic materials.

Particular interest will be paid to the structure of beetle’s cuticle that show vivid reflections over a very large spectral range as a consequence of the cholesteric liquid crystal organization of chitin molecules. These kinds of three dimensional photonic band gap material have been artificially reproduced with soft matter like liquid crystals to design microlenses or micromirors arrays. Recently, a structural periodicity of 20 nm has been measured into the wax layer. This last thin layer in contact with the outside is the smallest twisted structure ever observed in nature and it could play a role in enantioselectivity of pheromone perception. At this macromolecular scale, the characterization of such a biological material is very challenging. This exotic nanoarchitecture has not yet revealed all its secrets.

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