Study: engineers 3D-print working 'invisibility cloak'

Study: engineers 3D-print working 'invisibility cloak'

Now that we can 3D-print guns, cartilage and a human face, a Duke University engineering professor says we can begin 3D-printing invisibility cloaks on the cheap.


Yaroslav Urzhumov, assistant research professor in electrical and computer engineering at Duke, hails from the same institution that first gave us the invisibility cloak theory back in 2006. By 2009 David Smith, another Duke professor, was promising an invisibility cloak by Christmas, and by November 2012 the team had tweaked its microwave-deflecting cloak to tame light a little, with the hope of edging nearer to the ultimate goal: deflecting visible light.

Thus far, what we've managed to create is a metamaterial -- a type of manmade material composite -- that uses microscopic modulations in its surface to refract microwaves (and one day waves from visible light) around an object. Current incarnations of the cloak have been made from fiberglass and copper, but Urzhumov and his team decided to experiment with a 3D-printed polymer-based cloak. 

The result was a polymer disk dotted with holes. The holes' locations were assigned by an algorithm, located according to the optimum position for deflecting beams. An opaque object was then placed in the centre of the disk, and when the team directed microwaves at it, the object appeared to no longer be there.

"The design of the cloak eliminates the 'shadow' that would be cast, and suppresses the scattering from the object that would be expected," said Urzhumov. "In effect, the bright, highly reflective object, like a metal cylinder, is made invisible. The microwaves are carefully guided by a thin dielectric shell and then re-radiated back into free space on the shadow side of the cloak."

"The device is a relatively thin (about one wavelength thick) shell of an air-dielectric composite," the team explains in a paper published in the journalOptics Letters. "In a finite band (9.7-10.1 GHz), the shell eliminates the shadow and strongly suppresses scattering from a conducting cylinder of six-wavelength." The authors go on to suggest that the technique could be suitable for higher frequency radiation -- including visible light.

Meanwhile Urzhumov, who has run a bunch of simulations to see what other cloaks could be devised, believes the technique will be appropriate for building cloaks that are several metres in diameter, but still fairly thin at 2.5cm.

With competitors already trying to outdo Makerbot's $2,199 (£1,416) offering, we could very well be seeing DIY invisibility cloaks popping up all over the place. And though they'll probably not have a great deal of use for the time being -- the current cloaks being more suited to shielding aircraft from radar - 3D printing enthusiasts will be holding their breath for the moment the visibile light cloak CAD instructions go live. 

Urzhumov predicts: "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."

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