2012, Volume 7, Issue 4
Frontiers of Mechanical Engineering >> 2012, Volume 7, Issue 4 doi: 10.1007/s11465-012-0347-y
Investigations on color variations of
State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
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Abstract
Experiments and simulations are carried out to investigate the optical properties of butterfly wing scales. The upper surface of a male butterfly wing presents a single-layer of scales, the microstructures of which are responsible for the brilliant blue color. The color varies from cyan blue to yellow green and soon afterwards returns back to cyan blue when some ethanol is dropped on the upper surface. At the start of the ethanol volatilization process, the reflection spectrum remains stable. As the ethanol further volatilizes, the peak reflectance decreases slightly, then increases dramatically. Meanwhile, the peak wavelength keeps approximately constant, then decreases, and keeps almost stable at the end of the process. Therefore, the optical properties depend strongly on the varying ambient conditions, including the refractive index and the thickness of the packing medium. Moreover, the possible causes for the scales in dark green region after several dropping ethanol experiments are clarified. This research benefits our understanding of the color variation mechanisms of the wing scales, and provides inspiration for further studies and applications.
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