Funny things that science comes up with. One of those exciting things is Vantablack, a coating created by a company in Surrey, which basically swallows all the light that hits it. Just like a low-budget version of a black hole, right? Let’s get deeper into the problem because it is more interesting than it may sound at first.
What exactly does it do, and how?
I admit I wasn’t that interested in nanophysics until now, but the principle of this coating is fascinating. But first, what exactly is a “black” material? Some of you might have guessed it; it absorbs light. Obviously, a material or a coating, or however you want to call it, can be “more black” or “less black,” depending on its absorption percentage. For example, let’s say some surface has a 70% absorption percentage, which means it absorbs 70% of the light that hits it. Now this Vantablack thing absorbs 99.965% of the light that hits it. That’s something, right?
Yes, it is just something very, very black. It’s hard for me to explain what very, very black means, so I’ll just show you some pictures that seem to make things clearer.
The statue on the left is normal, as you can see, while the one on the right is coated with Vantablack. One interesting visual aspect of the Vantablack coating is that it makes things look 2D, so any spatial, three-dimensional sense is lost. Let’s try something else: how about this man having a black hole in his stomach?
The fun thing is how it was created by a company called Surrey NanoSystems. You can figure out yourself that the company has something to do with nanoscience, and so it is. One thing to know is that the scientists there weren’t particularly looking to make the “blackest” surface on Earth, but they discovered this accidentally. And what a cool discovery!
You can imagine the coating as a forest of nanotubes, all arranged vertically, just like trees. Nanotubes are really tubes on a nanosize. But why would we need that?
Imagine the light hitting the surface as a ray, just one ray. You can think of only one nanotube too. So one ray, one tube. What happens when the light hits the tube for the first time? Basic optics tells us that it ricochets; it bounces, say, on the opposite side of the tube. The same thing happens again with our ray, now in the tube. And again, and again, and again. When does the whole bouncing end? When it reaches the bottom of the tube, of course. Now the fun thing is that each time the ray hits the wall of the tube, a fraction of the light’s energy turns into heat. Obviously, if we have many bounces, the light will eventually lose all its energy.
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This is exactly how this coating works: it is a forest of nanotubes, which “traps” light inside so that only 0.035% manages to get out!
It really looks like a forest too! The image is exactly a “forest” of carbon nanotubes.
At first, the number of applications can seem small. Although, it is not really so. Of course, the visual aspect of this coating made it very appealing commercially, and currently, there is a great variety of Vantablack clothes on the market. Also, Surrey NanoSystems collaborated with the huge car company BMW to coat BMWs with Vantablack. They had an interesting result:
A super-black car! However, this is, obviously, not its most useful application. Vantablack was a perfect solution to the improvement of telescope mirrors, and even more to space telescope mirrors (and other optical instruments, sure), as the material is very resistant to “harsh” conditions, and the road to space is definitely “harsh.”