Gas sensing using hierarchical micro/nanostructures of Morpho butterfly scales

• We set up a reflective optical system for detecting the reflectance spectra.
• The reflectance spectra of ethanol/methanol vapor are higher than that of nitrogen.
• The three PCs capture 97.93% of the total variance in the reflectance spectra.
• The higher the concentration is, the thicker the liquid films are.
• As the concentration increases, there appears red shifting.

We have demonstrated the application of the hierarchical micro/nanostructures of Morpho didius butterfly scales for gas sensing. A reflective optical system was set up to detect the reflectance spectra of butterfly wing samples in a specific gas environment. Principle component analysis method was employed to discriminate and identify nitrogen, methanol and ethanol vapors according to the distribution of the projection points. Meanwhile, we constructed an appropriate 2D optical model of the butterfly scales with Rsoft software and theoretically simulated the gas sensing performance by rigorous coupled wave analysis technique. In the theoretical study, exposing the structures to vapors was modeled as vapor adsorption, resulting in the formation of nanometre-thick liquid films onto the structures, where the thickness of the film increased with the vapor concentration increasing. The experimental and simulation results match well, confirming that the butterfly scales indeed have the sensitivity and selectivity for vapors sensing. As such, we believe an optimized artificial structure mimicking Morpho butterfly scales can be used as gas sensors for sensitive and selective detection of closely related vapors.