The cloak would also struggle with any backlighting. 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. “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. The appearance of infrared and visible radiation are very different things, she says. 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. 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.” “It’s just the thermal radiation that changes.”Īndrea 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. “The critical thing is it does it with no change of temperature on the jacket itself,” says Tidball. 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. Of course, each panel needs to be programmed and passed to a microcontroller set within the jacket. Graphene’s near-unparalleled conductivity allows it to control the optics of any garment covered in it by applying voltage across it. That converts the graphene-an absorbing material-into a reflective material when it comes to infrared thermal radiation. “We basically control the electron on the graphene,” 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 have a multilayer graphene coating on the surface, and we intercollate ions between the graphene layers, similar to a lithium-ion battery,” 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.
“That’s the unique material that enables us to create these tunable optical surfaces,” says Kocabas. Unlike the physically impossible approach discounted in 2016, this technology is based on graphene layers. “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. It took a little longer than that to develop a first prototype.
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