Whether it’s James Bond flicking a switch to turn his Aston Martin invisible in the middle of a car chase, Harry Potter ducking and diving out of harm’s way by donning a magical invisibility cloak, the Predator, Klingon Birds-of-Prey, or the endless reams of literature based on characters being able to go about their lives undetected, the dream of tech that grants us invisibility has long been an obsession.
But it has, for now, remained in the realm of science fiction. As recently as 2016, researchers had concluded that the fundamental laws of physics meant a true invisibility cloak wasn’t possible. Past methods of creating invisibility relied on blocking objects at specific electromagnetic wavelengths—something that fell apart when you needed to work on multiple wavelengths at once.
That may no longer be the case. A 2019 patent, filed by a Canadian company called Hyperstealth Technology, suggested that it’s possible to bend light around an object using a “quantum stealth” cloak to make it disappear—albeit not perfectly. And militaries around the world continue to try to make the technology work. In 2020, the Israeli Ministry of Defense and tech company Polaris Solutions announced a 500-gram thermal visual concealment sheet that uses polymers to conceal anyone or anything underneath it.
However, a new method, developed by an apparel company best known for a metal jacket made from bulletproof material, a copper-infused garment designed to kill viruses, and an algae-based T-shirt that composts in 12 weeks—in collaboration with a UK academic—suggests that what was once thought of as a closed-off direction in technology could once more be open. That company, UK-based Vollebak, has developed a prototype of a thermal camouflage jacket that it says signals a critical first step towards an invisibility cloak.
“We’ve been thinking about invisibility ever since we started the company,” says Steve Tidball, cofounder of Vollebak. “We came out with some bold claims when we first started that we’re going to make clothes for the future. And many, many customers have written to us and said, ‘How about an invisibility cloak?’” But it wasn’t until Tidball saw a photograph of a graphene-based material that can fool an infrared camera into thinking there wasn’t anything there that he first felt it could become reality. “I thought that’s got to be a first step towards invisibility,” says Tidball.
The material had been developed by Coskun Kocabas, a professor of 2D device materials at the University of Manchester and the National Graphene Center. In 2019, Vollebak approached Kocabas and proposed a collaboration to try and develop the technology further into something that could eventually resemble an invisibility cloak. “When we first started the project, we thought we might have it done in three months,” says Tidball.
It took a little longer than that to develop a first prototype. “I underestimated the material challenges,” says Kocabas, “and the challenges of working with textiles.” Three years on, Vollebak and Kocabas are finally ready to unveil their thermal camouflage jacket.
Unlike the physically impossible approach discounted in 2016, this technology is based on graphene layers. “That’s the unique material that enables us to create these tunable optical surfaces,” says Kocabas. The jacket—made up of 42 panels of graphene around 5 centimeters square that are attached to the outside of a jacket—is controlled by the electron density of the material.
“We have a multilayer graphene coating on the surface, and we intercollate ions between the graphene layers, similar to a lithium-ion battery,” says Kocabas. A voltage is passed through the layers by a computer program that charges the ions within a liquid that sits between more than 100 layers of graphene that accumulate electrons. “We basically control the electron on the graphene,” says Kocabas. That converts the graphene—an absorbing material—into a reflective material when it comes to infrared thermal radiation. Graphene’s near-unparalleled conductivity allows it to control the optics of any garment covered in it by applying voltage across it.
Each of those 42 panels can be thought of as a pixel on a display that can be controlled individually, suggests Tidball. “A simplistic way of thinking about it is, we can turn it on and off,” he says. “A slightly more complicated way is rather than on and off, we can control how much thermal radiation each one of those patches emits.” Doing that can enable the panels to fool an infrared camera into thinking hot panels look cold, or cold panels look hot.
Of course, each panel needs to be programmed and passed to a microcontroller set within the jacket. That microcontroller then controls the voltage passed through each panel on the jacket at a different rate, depending on the pattern the wearer is trying to attain. “The critical thing is it does it with no change of temperature on the jacket itself,” says Tidball. “It’s just the thermal radiation that changes.”
Andrea Alù, Einstein professor of physics at City University of New York, and one of the researchers who in 2016 said an invisibility cloak was theoretically impossible, declined to comment on Vollebak’s claims because it lacked a supporting scientific peer-reviewed paper, making it hard to understand what the scientific progress was. Mario Pelaez-Fernandez, a postdoctoral researcher at the University of Lille specializing in graphene-related materials, says that tuning ionic liquids electrically to inform graphene patches what temperature they should display is “ingenious, and probably very expensive for the time being.” The use of the technology, she adds, is “certainly feasible.”
However, Pelaez-Fernandez is skeptical of how possible it is for what’s currently being displayed to turn into an invisibility cloak in the future. The appearance of infrared and visible radiation are very different things, she says. “If what they're saying is true, and this material could, hypothetically, be tuned to any wavelength in the visible spectra—something about which I have not found any literature, but that seems plausible—what they would have is something similar to a chameleon jacket, not an invisibility cloak,” says Pelaez-Fernandez. Rather, the system would take a color input from a specific place or object behind it and put it in a specific patch, but those colors would be relatively blocky.
The cloak would also struggle with any backlighting. “If you were to stand in front of a light source, you would still look like a shadow,” she says. “They're trying to sell it as a plausible future invisibility cloak when they already have a really cool device: an invisibility cloak for thermal cameras.”
Despite the bold claims linking the jacket to invisibility cloaks, Tidball and Vollebak are up-front about the fact that this is little more than a proof of concept. Unlike some other innovations the clothing company has developed, the thermal camouflage jacket is not yet for sale—and may not be for some considerable time. Wearers of the jacket are, for the time being, umbilically connected to a computer with wires. “Even though it’s got wires sticking out of it, and even though it’s attached to a computer, it’s still really exciting for me,” says Tidball. “Because the first iterations of clothing and technology merging are going to look like the Delorean from Back to the Future. It’s going to have wires sticking out of it, and it’s going to look like it’s come out of a lab.”
Naturally, having thought that developing a working thermal invisibility cloak would take three months, only for it to take 12 times that, Tidball is more realistic about estimations of when the clunky-looking prototype jacket can become something fully wearable for all. “Ultimately, you’re still a good five or 10 years away from actual invisibility,” he says, and this is before even figuring out how to miniaturize it in a way that would enable it to be sold on the high street. “This is just a step on the journey, to trick infrared cameras,” he says.
Some of the steps that get Vollebak from the prototype to a finished invisibility cloak are more fine-tuning on the hardware. “This thing has 42 patches, and just like bricks in a house, you can effectively see the mortar in between them,” Tidball says. “It’s clear that one thing is a patch, and another thing is not.” Increasing the number of patches from 42 to thousands, while decreasing their size to make them more malleable and able to curve around a body, is vital. Then those patches need to do more than change thermal radiation, but also change color. “In simple terms, the graphene pixels we’re using, if supplied with enough energy, can change color. My gut is those first steps in changing color might be binary,” says Tidball. “It’s not going to be squid skin, yet.”
The key word there is “yet.” Selling invisibility cloaks to the wider public is still very much a dream for Tidball. But the scenario he envisages if he does succeed hints at just how much work is yet to be done to make that possible. “I can imagine retiring to a desert island and everyone walking around in invisibility cloaks. We might be a good couple of decades away from it.”
