Blackest Black Ever Created by MIT Scientists, Captures Over 99.99 Percent of Light

Scientists from Massachusetts Institute of Technology (MIT) have unveiled the blackest black ever produced at an art exhibition in New York. The material, which is 10 times blacker than anything ever before reported, is made from carbon nanotubes (CNTs) and cuts out over 99.99 percent of light.

This feat was achieved by accident—the team of engineers had been experimenting with different ways to create CNTs. These are extremely thin tubes of carbon that are strong and excellent conductors of heat and electricity—properties that make them of great interest to scientists.

Brian Wardle's team at MIT had been trying to grow CNTs on aluminium when they reached a hurdle. They found that a layer of oxide would coat the aluminium as soon as it was exposed to air—and this layer stopped it from conducting heat and electricity. To remove the oxide layer, Wardle and colleagues used salt to dissolve the layer.

After removing it, the aluminium was transferred to an oxygen-free environment and then placed in an oven to grow the nanotubes. Initial results showed the material's thermal and electrical properties were significantly enhanced. They also noticed something unexpected, however—the color of the material.

At this point, they noticed how dark the material was. "I remember noticing how black it was before growing carbon nanotubes on it, and then after growth, it looked even darker. So I thought I should measure the optical reflectance of the sample," Kehang Cui, who is now at Shanghai Jiao Tong University, China, said in a statement.

Measurements showed the material absorbed over 99.995 percent of incoming light from every angle. "Any object covered with this CNT material loses all its plasticity and appears entirely flat, abbreviated/reduced to a black silhouette," Diemut Strebe, the artist who collaborated with the MIT scientists, said in a statement.

blackest black
When the diamond was coated in the foil, it vanished. Analysis showed the newly created material was 10 times blacker than anything reported before. R. Capanna, A. Berlato, and A. Pinato

Strebe and the MIT team unveiled the material at an exhibition called The Redemption of Vanity at the New York Stock Exchange. In it, the team cloaked a 16.78-carat natural yellow diamond in the material to show how it disappeared into darkness. Diamonds, which are also made of carbon, is one of the best reflectors of light found on Earth. "Because of the extremely high light absorbtive qualities of the CNTs, any object, in this case a large diamond coated with CNT's, becomes a kind of black hole absent of shadows," Strebe said.

The scientists are not sure why the material is so black but believe there may be a connection between the CNTs and the way the aluminium is etched. "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 says.

Wardle and Cui's findings are published in the journal ACS-Applied Materials.

Along with hiding diamonds for art, the MIT engineers say the ultra-dark material could have practical applications in telescopes, helping to reduce glare while looking out into space.

"There are optical and space science applications for very black materials, and of course, artists have been interested in black, going back well before the Renaissance," Wardle said. "Our material is 10 times blacker than anything that's ever been reported, but I think the blackest black is a constantly moving target. 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."