Vapor sensing on bare and modified blue butterfly wing scales

TL;DRAbstract

In butterflies possessing structural color, the scales covering the wing contain a photonic nanocomposite material constituted from chitin (high refractive index) and air (low refractive index). The reflected color is defined by the periodicity and refractive index contrast of the structure. The structural color is altered measurably when its low refractive index component is replaced by an (air + vapor) mixture, resulting in a concentration and vapor species dependent optical reflectivity variation. It is shown that the reflectivity of the nanoarchitecture, its surface chemistry and characteristic pore size can be modified with a high degree of precision by Atomic Layer Deposition (ALD) of Al2O3. If the thickness of the deposited layer is kept under control with nanometer precision, the spectral position of the reflectance maximum can be finely tuned. The response signal of pristine and ALD modified butterfly wings is compared.

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