![]() Various companies and institutions have developed their own versions of ultra-black materials using carbon nanotubes over the past few years. The tubes are very thin compared to the size of a photon - around 400 to 700 nanometers, just thin enough to trap photons rather than allowing them to immediately bounce away. Lehman and his colleagues at NIST grow low-density forests that contain about one billion nanotubes per square centimeter. When arranged in a properly spaced “forest,” the carbon nanotubes become even blacker. So we really feel like this is more of a science than an art.” “It's really hard to do, to get the ‘sidewalk’ temperature right and all those sort of things. “In the past, gold black - pun intended - was kind of a black art,” Lehman says. They can also be grown lithographically, meaning researchers can place them exactly where they are needed and stop their growth when they reach a desired height. Illustration of carbon nanotubes (Credit: nobeastsofierce/Shutterstock)Ĭarbon nanotubes are one of the strongest and stiffest materials discovered to date, but that’s not the only reason Lehman and other researchers turned to them in the search for the blackest black. As the graphite heats up, it settles into the ring-like template provided by the metal before building upward. To make them, scientists cook graphite with a metal, such as iron, in an oxygen-free furnace. “If a nanotube were a telephone pole, it would be a telephone pole a foot in diameter and three miles long,” Lehman says. These tubes, at most 100 nanometers in diameter, are more than 1,000 times thinner than a human hair. Growing Nanotube ForestsĪround 2004, Lehman began investigating a new replacement for metal blacks: carbon nanotubes, cylinders of carbon atoms, or graphite. ![]() Photons rattle around the microstructures of metal blacks in much the same way, before ultimately being absorbed. But when snow finds itself on a cold sidewalk, it accumulates more easily - creating a “fluffy” structure akin to the super black feathers of birds-of-paradise. ![]() When snow falls on a warm sidewalk, it turns into a wet mess. “It’s gold that you boil off in a low-pressure nitrogen environment and it's very analogous to snow falling on a sidewalk if you get the conditions just right.” “ is fluffy, for lack of a more sophisticated way to put it,” says John Lehman, a physicist at the National Institute of Standards and Technology (NIST) who began making detectors with gold black in the ‘80s. Metal blacks, derived from gold, silver and nickel, came later on and are still used by scientists today. And American astronomer Samuel Pierpont Langley crafted the first bolometer (an instrument that measures radiation from the sun via the rise in temperature of a blackened metal strip) in the 1870s using soot from a gas lamp. Artists Rembrandt and Johannes Vermeer, among others, used carbon blacks in many famous paintings. Humans have used carbon blacks, pigments traditionally created by charring ivory, bones or grape vines and stems, since prehistoric times. (Credit: Natasha Baucas/CC BY-SA 2.0/Flickr) The Gold Standard But just how black can these materials get? They’ve also been used in space, preventing stray light from entering telescopes and improving infrared sensors focused on Earth’s radiation budget. Materials capable of absorbing upwards of 99.9 percent of light could increase the absorption of heat in solar power technology, or find use in military applications such as thermal camouflage. Indeed, scientists have been on the hunt for their own, improved, version of an ultra-black material for over a decade - but not for courtship rituals. For example, the spider is being researched for fabricating new solar panel coatings.” “We can look to these birds and these spiders and try to get inspiration for resilient, weather-resistant materials that can absorb light really well. “Engineers are very smart and they've made great devices, but nature has some cool tricks,” McCoy says. Some snake and deep-sea fish species evolved these ultra-black scales to camouflage their movement in dark environments, while peacock spiders and certain birds-of-paradise display the color in combination with more vibrant hues for eye-catching courtship rituals.ĭakota McCoy, a postdoctoral researcher in biophotonics at Stanford University, says that these biological adaptations - like how some birds-of-paradise use their light-absorbing feathers to convert particles called photons into thermal energy - can serve as inspiration for new technologies. There’s black, and then there’s ultra-black: a blacker-than-black color that absorbs up to 99.9 percent of light.
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