Sunday, July 26, 2009

COLOR WITHOUT PIGMENTS



Pictures taaken from BBC Front Page.



Mohan Srinivasarao (Chemist/Georgia Institute of Technology in Atlanta), expert in liquid crystals, confocal microscopy and nano-optic biology has discovered the causes by which jeweled beetle (Glorious chrysina), exhibits splendid metallic green color, without need of pigments. The techno-breaktrough that will revolutionize the colors of our dressing , commercial propaganda and TV, needs of helical structures (similar to liquid crystals), located in beetle’s exoesqueleton, settled down in layers of hexagonal and pentagonal cells (~10 µm), that match wavelength of green light.

With confocal microscopy, Srinivasarao built 3-D images of exoesqueleton’s cells, discovering that these reflected selectively left circularly polarized light. The cells consisted of nests of concentric arches (helicoid structures), located in cone’surfaces of scarce depth. Srinivasarao, inferred that these patterns were structural and optically similar to the conical domains formed spontaneously in the surface of liquid cholesterol crystals. Green color depend on the size of helical structures, that in this case were comparable with the wavelenght of green light.



COLOR SIN PIGMENTOS

Mohan Srinivasarao (Quimico/Georgia Institute of Technology in Atlanta), experto en cristales líquidos, microscopia confocal y nano-óptica biológica, ha descubierto las causas por las que el escarabajo-diamante (Chrysina gloriosa), exhibe un espléndido color verde metálico, sin necesidad de pigmentos. El breaktrough tecnológico que revolucionará los colores de nuestras vestimentas, la propaganda comercial, la TV, etc, necesita de estructuras helicoidales, semejantes a cristal liquido presentes en el exoesqueleto del escarabajo, establecidas en capas de células hexagonales (~10 µm) y pentagonales.

Con microscopia confocal, Srinivasarao construyó imágenes tridimensionales de las células del exoesqueleto, descubriendo que éstas reflejaban selectivamente luz circular izquierda polarizada. Las células contenían nidos de arcos concéntricos (estructuras helicoidales), ubicados en superficies de conos de escasa profundidad. Srinivasarao, infirió que estos patrones eran estructural y ópticamente análogos a los dominios cónicos formados espontáneamente en la superficie de cristales de colesterol liquido. El color verde depende del tamaño de las estructuras helicoidales, que en este caso, eran comparables a la longitud de onda del color verde.

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