Golden moth-inspired structures with a synergistic effect of interference, absorption and scattering

Abstract

We describe a new type of photonic material inspired by a Diachrysia chrysitis moth, whose nano-structured wings exhibit a prominent golden color. This is a layered photonic structure with a large refractive index contrast, whose alternating layers are rough at the nanoscale level. Theoretical analysis shows that the scattering and interference interact to enhance the local field within the layers and increase the absorption of the material, particularly in the UV-blue part of the spectrum. Theory is experimentally verified using holographically manufactured Bragg gratings in the dichromated-pullulan (DCP). Alternating air-pullulan layers are produced and held in place by sparsely separated nano-pillars. Air voids are filled with 20-100 nm diameter spherical nanoparticles which act as scatterers. Such materials, with a high refractive index contrast and nano-scale scatterers, are important for achieving large reflectance and a broad spectrum, with scattering as an additional mechanism for spectral control.

Reflectance spectroscopy and machine learning as a tool for the categorization of twin species based on the example of the Diachrysia genus

“…Previous studies on the spectral features of wings in moths of the genus Diachrysia focused on explaining the phenomenon of golden iridescence in D. chrysitis [43,44]. This arises as a result of interference, scattering and absorption in the structures of the glass scales.…”

How Spectral Properties and Machine Learning Can Categorize Twin Species - Based on Diachrysia Genus

“…Previous studies on the spectral features of wings in moths of the genus Diachrysia focused on explaining the phenomenon of golden iridescence in D. chrysitis 54,55 . This arises as a result of interference, scattering and absorption in the structures of the glass scales.…”

The genome sequence of the Burnished Brass, Diachrysia chrysitis (Linnaeus, 1758)

“…The iridescent gold sheen on the forewings is a structural colour generated by light scattering and interference rather than a chemical pigment. Indeed, wing scales in the gold regions are devoid of melanin pigment and form a nanoscale multilayer structure enclosing a sandwich of irregular spheres ( Savić-Šević et al , 2018 ). The spectrum of reflected light from golden regions of the wing is a close match to that generated by true metallic gold ( Pantelić et al , 2017 ).…”

“…The spectrum of reflected light from golden regions of the wing is a close match to that generated by true metallic gold ( Pantelić et al , 2017 ). These remarkable optical properties have stimulated efforts to mimic the structure in a laboratory setting, and a successful proof of concept has been achieved using layers of polysaccharide sandwiching spherical nanoparticles of variable size ( Savić-Šević et al , 2018 ). Similar multilayer structures may ultimately prove useful in solar energy collection and other applications.…”