A large variety of natural photonic structures, which are found mainly in insects, is known to produce so-called structural colours and, for most of them, to exhibit iridescence, i.e. colour changes with viewing angle. These structures and effects, optimized for thousands of years of evolution, allow us to elaborate new concepts and devices through a biomimetic approach. Natural photonic crystals in butterflies, beetles and other insects consist of ordered porous chitin structures. Colour changes can be induced by variations in the composition of the ambient atmosphere. Based on this effect, it has been possible to identify specific vapours/gas and to give at least a qualitative indication of their concentrations. In spite of increasing interests and investments for such bio-inspired gas sensors, the fundamental mechanisms at the origin of their selective optical response are still not well understood.
This project consists in an interdisciplinary and fundamental research on the selective gas sensing capability of naturally grown photonic architectures, available in various morphologies in butterfly scales. The main objective of the project is to get a deeper understanding of these mechanisms which could lead to a better optimization and to the emergence of novel bio-inspired optical sensors. Therefore, we will develop an experimental method in order to establish correlations between the optical response and the atmosphere composition. We will then identify the physico-chemical origins of the optical response of the photonic nanostructures, elaborate photonic models for predicting colour changes and propose new designs of gas sensors inspired by natural photonic structures.