Research On The Detection Of The Background Media Using Butterfly Wing Scales: Experiment And Modeling

The structural color as a special bio-physical phenomenon existing in the world hasbeen paid more attention by many researchers. The iridescent blue color of Morphobutterfly which is one of the most popular examples can be found from far away. It is atypical structural color. The optical property of the butterfly wings changed obviouslywhen the surrounding media was altered.In this thesis the response characteristic of the Morpho Didius butterfly to differentbackground media was investigated. First, the color of the butterfly wing scale in differentmedia was observed using the Keyence microscope. It can be found that the wing colorwould change obviously when dropping methanol or ethanol on it. Otherwise, thereflectance spectra of the butterfly wing scales in different media were measured. Theresults revealed that the reflectance spectra and the color corresponding to the spectra havethe significant differences when the sample was in different media. And through theprincipal components analysis the response was further differentiated. In addition, thereflectance spectra of the wing scale immerged in different organic vapor was detected.The reflectance spectra and the color corresponding to the spectra changed very little. So itcannot be used to distinguish individual media. A method to calculate the relative changesof the reflectance spectra was introduced here. It could amplify the discrepancy ofdifferent media and get rid of the influence of the carry gas. The results certificated thatthe butterfly wing can be used to distinguish different media.Furthermore, the Rigorous coupled wave analysis technique was employed to analyzeresponse property of the mimic models to different media. First, two more simplifiedmodels was designed to contrast. By comparing the modeling results with experiments, weidentified that the Model I has the best sensitivity. It mimicked the actual scale structurewell and can be used to further studying. The model looks like a grating structure in thetransverse direction, and in the vertical it’s like a Multi-layer film structure. The mainstructural parameters were access from the structure. Then the impact of these parameterson the reflection property of the wing scale was analyzed. At the same time, this thesisinvestigated the property of the wing scale while it was in different background media.When it was in homogeneous media, the media was represented by the index of refraction,and when it was in organic vapor, the media was characterized by the film with differentthickness. The reflectance property of the model was investigated. It can be found that themodel can distinguish the media and the organic vapor through the reflectance spectra andthe Data processing method.The experiments and simulations help us have a deep understanding of the mechanism of the structural color and its sensitivity. It can be used to steer the design,manufacture and applications of the bionic micro/nano structures/devices forenvironmental detection.