Vapor sensing with a natural photonic cell

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Photonic structures encased by a permeable envelope give rise to iridescent blue color in the scales covering the male Hoplia coerulea beetle. This structure comprises a periodic porous multilayer. The color of these scales is known for changing from blue to green upon contact with water despite the presence of the envelope. This optical system has been referred to as a photonic cell due to the role of the envelope that mediates fluid exchanges with the surrounding environment. Following from previously studied liquid-induced changes in the color appearance of H. coerulea, we measured vapor-induced color changes in its appearance. This response to vapor exposure was marked by reflectance redshift and an increase in peak reflectance intensity. Different physico-chemical processes were investigated to explain the increase in reflectance intensity, a property not usually associated with vapor-induced optical signature changes. These simulations indicated the optical response arose from physisorption of a liquid film on the beetle scales followed by liquid penetration through the envelope and the filling of micropores within the body of the photonic structure.

Original languageEnglish
Pages (from-to)12267-80
Number of pages14
JournalOptics Express
Issue number11
Publication statusPublished - May 2016


  • Photonic crystals
  • Photonic bandgap materials
  • Color
  • Biomaterials
  • Optical sensing and sensors
  • Vision
  • Spectra


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