RESUMO
We studied the structural and optical properties of scales in the longhorn beetle Sphingnotus mirabilis. Structural characterizations revealed that the scale interior possesses a disordered bicontinuous macroporous structure, resembling a phase-separated structure obtained by spinodal decomposition. Its optical response was investigated both experimentally and theoretically. Our results show that this structure has interesting optical properties due to the existence of only short-range order and the lack of well-defined local structures.
Assuntos
Biofísica/métodos , Besouros/fisiologia , Animais , Cor , Análise de Fourier , Microscopia Eletrônica de Varredura/métodos , Microscopia Eletrônica de Transmissão/métodos , Modelos Biológicos , Óptica e Fotônica , Fótons , Porosidade , Refratometria , Propriedades de SuperfícieRESUMO
Scales on the elytra of longhorn beetle Anoplophora graafi display diverse non-iridescent colors ranging from blue, green, yellow, and red to purple. By structural characterizations, optical measurements, and theoretical calculations, we found that the scale colors stem from an amorphous photonic structure possessing only short-range order: random close-packing of chitin nanoparticles. Our results showed that direction-independent photonic pseudogaps found in the photon density of states of the random close-packing photonic structure are the ultimate physical origin for non-iridescent coloration of scales. The color steering strategy of scales is ingenious, simply by varying the size of chitin nanoparticles. Revealed natural random close-packing photonic structures and the color steering strategy of scales could render valuable inspiration for the artificial fabrication and design of photonic structures and devices as well.
