Graphene Coating Inspired by Fish Scales

Graphene coating changes color when deformed.

Dresden, GERMANY –A coating inspired by the skin of the iridescent fish could highlight structural weakness in buildings, bridges, vehicles and aviation.

Most coatings are colored by adding pigments―materials known to absorb and reflect light at specific wavelengths. But other materials are given color by changes in their structure at a microscopic level, where the interference of reflected light becomes amplified at specific frequencies in the visible spectrum. Some of nature’s most brilliant, vibrant colors are made this way, such as wings of a butterfly, feathers of the peacock.

Inspired by these examples, a team led by Shanglin Gao at Leibniz Institute of Polymer Research has developed a coating that forms its colors, structurally, based on nanometer-sized flakes made of graphene. “The new material is a kind of traffic light to warn of hidden damage in buildings and vehicles,” says Gao, “as it changes color depending on deformation.”

Normally, the coating is red; however, when deformed, it appears yellow, and when cracked at the micrometer scale, green. This color-changing ability comes from a careful initial alignment of the graphene flakes in semi-transparent, parallel layers, coating a glass fiber. Under mechanical stress, the layers compress and flatten, changing the interference and color of reflected light.

"Structural failure usually starts with tiny cracks and deformations," Gao explains. "Generally, these micro-scale cracks are hard to detect. Accumulating unseen, they can eventually cause sudden, catastrophic fractures and serious accidents."

Coating buildings or even vehicles with Gao’s material, however, could give a clear visual warning of early damage. Real-world applications, however, will first require much more knowledge about the properties and behavior of the coating, notes Gao.

IPF-Dresden is a non-university research institute and a member of the Gottfried Wilhelm Leibniz Scientific Community carrying out fundamental as well as application-oriented research in all areas of polymer science and investigates polymer materials with new or improved characteristics.

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