Simple, beautiful, classic: MIT creates blackest black material

A team at MIT developed the coating, which consists of carbon nanotube “forests” grown on chlorine-etched aluminium foil. The material is 10 times blacker than any previously reported material, capturing at least 99.995% of incoming light.

Professor Brian Wardle at MIT’s Necstlab said: “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.”

The none-more-black material is made from vertically aligned carbon nanotubes – microscopic filaments of carbon – grown on a surface of chlorine-etched aluminium foil. The researchers had originally been attempting to remove the oxide layer from aluminium.

After measuring the amount of light reflected from every possible angle, they deduced that it reflected 10 times less light than any other super-black material, including Vantablack, developed by Surrey NanoSystems, which absorbs up to 99.96% of visible light.

Researchers believe it may have something to do with the combination of etched aluminium with the carbon nanotubes, which can trap and convert incoming light to heat, reflecting very little of it as light.

Any jagged or curved object covered with this new CNT material appears entirely flat, reduced to a black silhouette, regardless of the angle at which it is viewed. Because of this unusual trait, it is being presented at the New York Stock Exchange until November 25 as part of an exhibition that appears to make a 16.78 carat natural yellow diamond disappear.

Diemut Strebe, resident artist at the MIT Center for Art, Science & Technology, said: “Because of the extremely high light absorbtive qualities of the CNTs, any object – in this case a large diamond coated with CNTs – becomes a kind of black hole absent of shadows.

“In outright contradiction to this we see that a diamond, while made of the very same element – carbon – performs the most intense reflection of light on Earth.”

The CNT material could have practical uses in optical blinders that reduce glare to help space telescopes spot orbiting exoplanets. MIT said Nobel laureate John Mather is also interested in using it to develop a large star shade to shield a space telescope from stray light.

But how much more black could this be?

“The blackest black is a constantly moving target,” Professor Wardle 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.”

The MIT team has applied for a patent for their material, which is described further in ACS-Applied Materials and Interfaces.