When the world's darkest material made headlines in 2014, pundits predicted it would be used to turn military jets invisible, revolutionise our telescopes, and enable new trends in blacker-than-black haute couture.
Vantablack, invented by UK technology company Surrey NanoSystems, is a deep black material that absorbs 99.96 per cent of the light that hits it.
It can be used to coat 3D objects, turning them into visually flat, black 'holes' without any sense of shape.
But from much-hyped beginnings, is Vantablack actually out there in the real world three years after it was first revealed?
According to Surrey NanoSystems chief technical officer, Ben Jensen, the answer is yes.
He says the company is involved in a range of applications right now and more are on the horizon — though none involve painting stealth jets black.
"Future applications are opening up constantly — literally we get new applications in on a daily basis, some of which are absolutely huge," he said.
"The market for it is expanding and expanding, and for us the challenge is scale — building bigger and faster to meet that demand."
A forest of nanotubes
Creating the Vantablack coating starts with "catalyst particles" no bigger than a nanometre or two in diameter, which, after being saturated with gas, grow into carbon nanotubes.
For each square centimetre of coating, there's about a billion of these nanotubes.
The structure of evenly spaced nanotubes — not too far apart and not too dense, either — allows particles of light to get into the spaces between the tubes and be absorbed by them like light falling between the trunks of a vast forest of trees. The fraction of light the coating does reflect comes from light particles that hit the very tops of the nanotubes.
By itself, Mr Jensen says the coating looks rather unremarkable.
"If you see it on a flat surface on its own, with no other black material to reference it against, it just looks like a black velvet surface," he said.
But when other black surfaces sit side-by-side with it, they look grey. And when it's applied to 3D objects, they almost vanish into a shapeless, two-dimensional silhouette.
"If you see it on a 3D object, like crinkled foil, the coated side still looks like a black two-dimensional flat surface. It's only when you turn it around and you realise that it's got a lot of dimensionality, that you grasp how different it is," Mr Jensen said.
Because it's made of delicate carbon nanotubes that are more than 99 per cent empty space, Vantablack can't be touched without damaging the effect of the coating.
But if it's placed where it can't be disturbed — like the inside of an instrument used in space — it'll act as if it's a black hole, absorbing any light that hits it.
Vantablack in space
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Because of its light-absorption qualities, Vantablack can improve upon existing technologies used in space to prevent unwanted, reflected light from interfering with instruments like star trackers and telescopes.
The super black coating made its debut in space on a European microsatellite launched in December 2015.
Mr Jensen said the coating, used in the satellite's star tracker, improves the satellite's ability to monitor its position relative to the stars by absorbing stray light that enters its sensors and would otherwise affect the instrument's accuracy.
"You can imagine up in space people think of it as being really black and dark, but actually it's incredibly bright up there because the Sun's like a huge arc lamp and you've got light reflecting off the Earth and moon. So the stars are really quite faint," he said.
"This material's helping those star tracker cameras to improve performance and reduce the mass on the satellite, which is really important."
Another space application currently being trialled by Surrey NanoSystems involves coating the baseplates of Earth observation satellites, where it can be used to calibrate a satellite's cameras before they snap a picture.
Vantablack is also set to be used in infared sensors, after it was acquired by a US infrared instrumentation manufacturer.
Mr Jensen said the coating would help improve the signal-to-noise ratio in infrared imaging systems, like those used by firefighters to detect the thermal signatures of fires or people in a blaze.
"Where they're looking for body heat and want the best possible signal, this material helps improve the performance of those imaging systems," he said.
Of course, Vantablack's applications aren't all so science-focused.
It's also attracted interest for its aesthetic properties, and is controversially available to British-Indian artist Anish Kapoor for his exclusive use, a move criticised by other artists who also want to use the peculiar properties of Vantablack in their art.
Kapoor has used the material to collaborate with luxury watchmaker MCT for a limited edition watch that uses Vantablack on its back dial and minute hand.
NASA working on its own super black materials
NASA has also been developing super black materials for about ten years.
In 2014, it launched its own carbon nanotube coating — which absorbs about 99.9 per cent of light — into space for testing on the International Space Station.
John Hagopian, an optics engineer involved in NASA's super-black research since its inception, said the space flight showed their material could survive if it were enclosed in an instrument.
"So you could use it in baffles, satellite controls, absorbers for super-conducting detectors. There's a ton of applications," he said.
Mr Hagopian thinks super black materials have a bright, or indeed extremely dark, future in coronagraphs. These are devices that attach to a telescope and block out the light of a star so things nearby, like exoplanets, can be seen better.
"If you're looking at a very dim object like a planet around a distant star and you use a coronagraph and it blocks out the glare of the star, you can look at the atmospheric signature of the planet nearby," he said.
"So far no one's really done this sort of thing with a coronagraph, but we're in the process of building implementation to do that. This has really got a lot of potential."
But while he said the material has a future in space, Mr Hagopian thinks it's unlikely the coating will make it to many everyday products because of the delicate nature of carbon nanotubes.
"To make these materials robust enough to be used on things that are exposed to dirt and the environment, to touching — I really don't see that as being practical," he said.
Mr Jensen predicts a big growth area for Vantablack will be in the automotive industry, where the coating could be used to prevent light from interfering with the sensors of self-driving cars.
"If you're driving in low sunlight and it blinds the vision system you come into an unsafe situation. Anything you can do with these technologies where you can protect and improve stray light suppression within the vision system is a real benefit," he said.
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