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Fig. 7.16 (continued) ( b ) Natural photonic structure, Papilio blumei butterfly. ( i ) The bright green
wings of the P. blumei butterfly resulted from the mixing of the different colors of light from
different regions of the wing scales. ( ii , iii ), Optical micrographs (scale bar: 20
m) showing that
the concavities reflect yellow and blue colors under normal incident light. ( vi ) Scanning electron
micrograph showing that the surface of a wing scale is covered with concavities (diameter
5-
10
m). ( v ) The transverse cross section of concavities consists of 21 alternative cuticle and
air layers with a thickness of 120 nm. Reflectance spectra under normally incident light and
45 ı incident light, and the overlapping of the spectra confirm the non-iridescent property of the
green wing scales of P. blumei (From [ 148 ]). ( c ) Mimicking by surface structural engineering. ( i )
Deposition of polystyrene colloids on a gold-coated silicon substrate. ( ii ) Growth of platinum or
gold in the interstices of the colloidal array by electroplating. The metal deposition is terminated
when the thickness of the deposited film equals the microsphere radius. ( iii ) Removal of the
polystyrene spheres from the substrate by ultrasonication in acetone. ( iv ) Sputtering of a thin
carbon film and ALD of a stack of 11 alternating TiO 2 and Al 2 O 3 layers ( arrows indicate the
precursor gas flow). ( e , f ) In a second route, the colloids are molten to cover the cavities with a
homogeneous film, ( v ) which is covered by a TiO 2 -Al 2 O 3 multilayer [ 141 ]( vi ). ( a , b ) Reprinted
with permission from [ 30 ] © 2012 Wiley-VCH Verlag GmbH & Co. ( c ) Reprinted with permission
from [ 172 ] ©2010, Nature publishing group
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