Structural damage can be really difficult to monitor especially after earthquakes. But now there is a solution, which is rather unusual, to make them visible: through ‘fish scale’ coating.
German researchers have created a graphene-based coating that changes its color when deformed or damaged, like when fishes move. Nanometer-scale graphene flakes were made in semitransparent, parallel layers and tested in glass fibers.
It works just the same with the iridescent fish: they derive color from their structure instead of containing pigment. That means that the coating, which has a periodically-arranged microscopic structure, interfere with light as it strikes and is reflected on them, which amplifies some visible wavelengths and suppressing others.
The same mechanism is true with colored cells in butterfly wings, peacock feathers, and skins of squid, among others.
Source: Wikipedia Commons
Source: Smithsonian Mag
“Structural failure usually starts with tiny cracks and deformations,” said Shang-Lin Gao, the leader of the research and specialist in composite materials at the Leibniz Institute of Polymer Research. He added, “Generally, these microscale cracks are hard to detect.”
To identify the structural damage, the graphene-based coating should be applied before the cracks happen. After earthquakes, for example, the coating will be deformed which will have its layers compress and flatten, hence changing the way light reflects from them and affects the color.
The new material is a kind of traffic light to warn of hidden damage in buildings and vehicles, said Gao, as it changes colour depending on deformation.
When no change or damage has occurred, the coating should be in red. When deformed, it should turn to yellow; and when cracked on the microscale, it should turn to green.
Its makers hope that this “fish scale” coating could change drastically how structural damage – even at the microscale – are being detected and monitored not only building and structures but also in vehicles. But Gao recognizes the need to explore more about the properties and behavior of this coating before it gets used as a structural damage measure in the real world.
Source: Chemistry World