From left: The diamond prior to the material being placed on it and, on the right, it being made invisible with the addition of the material. Image: R. Capanna/A Berlato/A Pinato
Scientists are heralding the creation of a material 10 times blacker than anything before it, but they think they it can go darker.
Groups of scientists are continually trying to tap into the ‘dark side’ with attempts to make the blackest material on Earth, and now a team from MIT has announced the creation of something so black it captures nearly all light that comes into contact with it. In a paper published to the journal ACS-Applied Materials and Interfaces, the researchers said their new material is 10 times blacker than anything that has come before.
Comprised of vertically aligned carbon nanotubes that look like a fuzzy forest of tiny trees, the material was grown on a surface of chlorine-etched aluminium foil. Capable of capturing more than 99.96pc of any incoming light, the cloak-like material has been exhibited as a piece of art entitled The Redemption of Vanity.
If you observe it in person, any bumps or ridges – seen at any angle – become invisible, obscured in a void of black. The artwork was a collaboration between MIT’s Brian Wardle and artist Diemut Strebe, and covers a 16.78-carat natural yellow diamond – worth $2m – in the incomprehensibly black material.
Aside from making an artistic statement, Wardle said it could be useful in optical blinders that reduce unwanted glare in order to help space telescopes spot orbiting exoplanets. However, he added that this latest material is not the endpoint of research.
But is it blacker than priests’ socks?
“I think the blackest black is a constantly moving target,” he said. “Someone will find a blacker material, and eventually we’ll understand all the underlying mechanisms and will be able to properly engineer the ultimate black.”
Explaining how the material came about, Wardle and co-author of the corresponding research paper, Kehang Cui, said that it actually came about by accident. Its discovery was part of research to find ways of growing carbon nanotubes on materials such as aluminium to boost their electrical and thermal properties.
By removing an oxide layer that was proving problematic to this process, they found they could grow carbon nanotubes at much lower temperatures than they normally could, by about 100 degrees Celsius. While surprising in itself, the colour came as quite a shock.
“I remember noticing how black it was before growing carbon nanotubes on it, and then after growth it looked even darker,” Cui recalled. “So I thought I should measure the optical reflectance of the sample.”
The pair of researchers are still not exactly sure of the mechanism contributing to the material’s opacity, but they suspect that it may have something to do with the combination of etched aluminum, which is somewhat blackened, with the carbon nanotubes.
