This letter presents a biomimetic humidity sensor inspired by the humidity-dependent color change observed in the cuticle of the Hercules beetle. A thin-film-type humidity sensor with nanoporous structures (three-dimensional photonic crystals) mimicking the spongy multilayer in the beetles was designed and fabricated using the colloidal templating method and a hydrophilic surface treatment. The visible color of the fabricated humidity sensor changes from blue-green to red as the environmental humidity increases. The wavelength of reflected light that is predicted by Bragg’s equation considering the effect of water absorption shows a good agreement with experimental results.
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See supplementary material at http://dx.doi.org/10.1063/1.3486115 for description of another experimental case and the movie showing the color change from wet to dry state.
© 2010 American Institute of Physics.
2010
American Institute of Physics
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