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Invisibility cloaks made of plastic can now be created at home using 3D printers, researchers show.
The first clues that cloaking devices might one day become more than science fiction, a la "Star Trek" began emerging seven or so years ago. Since then researchers have made such cloaks a reality by smoothly guiding rays of electromagnetic radiation such as microwave beams completely around objects so they proceed along their original trajectory as if nothing were there.
The first working invisibility cloaks were demonstrated using complex lab experiments. They can now, in principle, get made at home using 3D printers.
"I would argue that essentially anyone who can spend a couple thousand dollars on a non-industry-grade 3D printer can literally make a plastic cloak overnight," said researcher Yaroslav Urzhumov, an electrical engineer at Duke University.
A 3D printer lays down thin layers of material much like ordinary printers, except it deposits layers on top of layers to create 3D objects. Increasingly, they are being used to make items out of plastic, metal, glass, ceramic, and even sugar and mashed potatoes.
Urzhumov said creating an invisibility cloak using a 3D printer was easy and relatively inexpensive. For instance, printers can make ones about 1 inch thick and 8 inches wide resembling Frisbees made of Swiss cheese.
Previous invisibility cloaks all included a fair amount of metal, "but with these new cloaks, no metal is involved," Urzhumov told TechNewsDaily. "This makes them easier to fabricate and lighter. Also, when a light wave hits a structure containing a lot of metal, it is attenuated, and the only way to have a cloak without attenuation is to get rid of these metals. Now we know it is possible to make microwave cloaks entirely out of nonmetallic materials, which is very exciting."
The cloaks have open spots in their centers in which to place items up to 5.5 inches wide. When microwaves are beamed at those objects from the side, the cloaks make it look as if the items are not there.
"A metal cylinder that would normally reflect a lot of microwave radiation can, once placed in the cloak, become transparent to microwaves," Urzhumov said.
Cloaks that make objects invisible to microwaves could have military and civilian applications.
"If you want to eliminate obstacles such as pillars or small buildings to microwave antennas, you could use these cloaks, which could be helpful for communications and for radar," Urzhumov said.
The fact that invisibility cloaks now can be made with pushes of a few buttons also makes it much easier to experiment with them. "We can try many different variations and optimize them, look for the most efficient versions," Urzhumov said.
So far, these cloaks hide objects only when viewed from the side. "We would like to make cloaks that render objects invisible to beams coming from any direction, fully 3D cloaks," Urzhumov said. "This would involve gluing together several cloaks to form a larger structure that completely encloses an object."
Much larger cloaks are possible in theory.
"Computer simulations make me believe that it is possible to create a similar polymer-based cloaking layer as thin as one inch wrapped around a massive object several meters in diameter," Urzhumov said. "You can imagine cloaking something as large as a pillar of stone or metallic masts on a ship."
Cloaks made of transparent plastics or glass are also possible, Urzhumov added.
"We believe this approach is a way towards optical cloaking, including visible and infrared," Urzhumov said.
The scientists detailed their findings May 15 in the journal Optics Letters.
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