Vapor sensing using a bio-inspired porous silicon photonic crystal

Naturally occurring photonic crystals present on the wing scales of Papilio butterflies are known to exhibit vivid iridescent coloration as well as various optical properties, including vapor sensing properties. This work reports the fabrication of a periodic array of concave multilayers in porous silicon mimicking the Papilio blumei nanostructure and its application as an optical vapor sensor. We compared the variations in the reflectance spectrum due to ethanol vapor adsorption and condensation inside the bio-inspired concave porous silicon multilayer structure to the variations of a standard flat porous silicon Bragg mirror. This results in an enhanced response time in the case of the bio-inspired concave structure.