Akira Saito, Shin-ya Yoshioka and Shuichi Kinoshita (Osaka University) Keiichiro Watanabe, Takayuki Hoshino and Shinji Matsui (University of Hyogo)
A Morpho butterfly, which is called a moving jewel, etches unforgettable marks in the mind of anyone who has ever seen one of South America's Morpho butterflies. It is only in recent years that its glittering blue has been proven to be a physical color (structural color) derived from microstructure instead of a chemical color. The Morpho butterfly has two amazing features. The first is its glaringly vivid reflected light. The second is a denial of rainbow colors. In general, the structural color changes its hues according to the angle of view. A typical example can be seen in the rainbow colors on the surface of a CD. The color of the Morpho butterfly, on the other hand, has little angle-dependence. This mystery has stimulated scientists into producing a number of hypotheses. This work is an anthology of struggles and also a report of successes.
The group from Osaka University proposed the hypothesis that the blue color is derived from a single nano-structural unit on phosphate powder, thereby negating the conventional principle of grating analogous to colors on CDs. The group then conducted a model experiment with semiconductor lithography and reproduced the blue color. The group from University of Hyogo processed and reproduced one nano-structural unit with an accuracy of 10 nm through nano-fabrication based upon the hypothesis proposed by the group from Osaka University (Kinoshita). Then, it verified the Morpho butterfly's blue with a micro-spectrograph. One of the greatest secrets in art of the natural world has been unraveled by three requisite conditions - theory, processing experiment and a verification test - through concerted efforts.

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Pete Vukusic This piece of work forms a complementary pair with the work that won the Gold Prize. That is, the author takes an optical approach to expound the ways in which diverse structural colors are formed on butterflies. He closely investigated the details of principles on the endlessly beautiful colors of various butterflies as well as the blue of the Morpho butterfly with an optical microscope, electron microscope and spectroscopic analysis. As for the swallowtail butterfly, he claims that the combination of micro-frame structure and the polarization property of light derived from three-dimensional structure have resolved this perpetual dilemma in the realm of nature. That is, he has discovered that the green that functions as a camouflage color to protect against enemies in the woods is seen as a dazzling blue signal by other butterflies due to the polarization property of light. He then proposes that such a mechanism be used as a new method of color presentation in art which goes beyond pointillism.

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Nicholas Eastaugh, Valentine Walsh, Tracey Chaplin and Ruth Siddall This piece of work functions in harmony with the work that won the Bronze Prize last year. In last year's work, a scientific approach was taken to illuminate plant dyes which had been used in paintings and sheets of cloth. This year's work focuses on pigments derived from minerals that have been used in paintings. The team created an exhaustive database on the chemical structure, physical properties and optical properties of each pigment. The database will be useful as a lexicon when a study is conducted on the origins of pigments concerning ancient paintings.

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