#structural color

In the 17th Century two giants of science, Isaac Newton and Robert Hooke, were both trying to understand how the wings of butterflies and peacocks, which are made of the same material as our fingernails and hair, could colors of such brilliant quality. They both came to the same conclusion, the color was a result of tiny structures on the wing, structures so small that they could not observe it themselves but had deduced must exist.

Science and technology have progressed far in those 300 years and not only can we easily observe the structure of a butterfly’s wing that produces such brilliant color, but we can readily create them ourselves. Inspired by this kind of structural color, researchers at Kyoto University’s Institute for Integrated Cell-Material Science (iCeMS), led by Prof. Easan Sivaniah, in collaboration with researchers from Semmelweis University and Kyoto University Medical School, have produced a structural color device for measuring the beating of heart cells which they hope will help speed up the process of pharmaceutical testing.

Like the wing of a butterfly, this device produces structural color from micro-patterns developed on the surface of a polymer gel. Heart cells beating on the device cause the structural color to change which can be detected easily with low power microscopes.

In nature, colors can serve as a form of communication, but they can also hide animals and plants, camouflaging them from sight. Researchers now report in ACS Applied Materials & Interfaces that they have developed polymers that can better mimic nature’s color-changing abilities than existing polymers. They say the materials could enable smart decorations, camouflage textiles and improved anti-counterfeiting measures.

Most of the colors that people are familiar with, such as hues on a piece of paper, are made with pigments. But another type, called structural color, exists, in which the color is produced by periodically arranged microscopic structures that interfere with visible light. For example, peacock tail feathers are actually brown, but microscopic structures present in the feathers make them look blue and green to the naked eye. Scientists have used cholesteric liquid-crystalline (CLC) polymers to mimic the structural coloration found in nature because they can easily be made into responsive materials. But so far, researchers have only produced them in a limited range of colors. So Albertus P. H. J. Schenning and Monali Moirangthem wanted to make CLC polymers with the full visible spectrum of colors.