A new level of black has been reached with a team of MIT scientists accidentally developing the blackest material ever recorded in the laboratory.
This new material captures at least 99.995 percent of incoming light, making it 10 times blacker than anything that's been previously recorded.
A Blacker-Than-Black Material
According to a news release from MIT, the material consists of vertically aligned carbon nanotubes or CNTs, which are microscopic filaments of carbon that scientists grew on a surface of chlorine-etched aluminum foil.
This blackest black material, which has yet to be named, is currently on display coating a 16.78-carat natural yellow diamond at the New York Stock Exchange with the title "The Redemption of Vanity." The $2 million artwork is a collaboration between Brian Wardle of MIT, his team, and Diemut Strebe of MIT Center for Art, Science, and Technology.
On this piece, the effect of the black is strikingly apparent. Instead of the diamond sparkling as it typically does, its completely enveloped in flat, all-encompassing black.
Wardle, co-author of the paper on the material published in the journal ACS Applied Materials and Interfaces, explained that the material isn't just for artistic purposes. He pointed out that there are optical and space science applications for extremely black materials, such as in optical blinders reducing glare, so space telescopes can easily spot exoplanets.
"Our material is 10 times blacker than anything that's ever been reported, but I think the blackest black is a constantly moving target," Wardle revealed. "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."
The Accidental Discovery
Wardle and co-author Kehang Cui of Shanghai Jiao Tong University weren't originally planning to create this specific black material. Instead, the duo was trying to find new ways to grow CNTs on electrically conducting materials to boost their electrical and thermal properties.
A roadblock on their experiments led the pair on a path towards the newly discovered material. While trying to grow CNT on aluminum, Cui found that a layer of oxide coats aluminum when it's exposed to air, which acts as an insulator instead of a conductor to electricity and heat.
A solution was eventually found: salt or sodium chloride that dissolves the oxide layer.
In further experiments that involved sodium chloride dissolving the oxide on aluminum and scientists growing CNTs on the aluminum, both Wardle and Cui were struck by the color of the material they produced.
Optical reflectance tests showed that the new material absorbed at least 99.995 percent of incoming light from every angle, which means it reflects 10 times less light than any other black, including the famed Vantablack. In fact, any imperfection or bump along the material's surface is effectively invisible, lost in the black void.
For now, the scientists are uncertain why they were able to produce the blackest black.
"CNT forests of different varieties are known to be extremely black, but there is a lack of mechanistic understanding as to why this material is the blackest. That needs further study," Wardle said.
