Invisibility cloak in the works at UT

Barak Bullock

Invisibility cloaks continue to move out of science fiction and closer to reality thanks to new research by UT scientists.

Though researchers still have a long way to go before making 3-D objects invisible to the naked eye, the group has successfully masked objects from microwave detection,  

The new development is the work of electrical and computer engineering assistant professor Andrea Alù, Dave Rainwater and Aaron Kerkhoff, research associates at Applied Research Laboratories, electrical and computer engineering graduate students Jason Soric and Pai-Yu Chen and physics graduate student Kevin Melin. 

Their research, published Monday in the New Journal of Physics, marks a step forward from previously bulky cloaks to an ultra-thin, flexible “mantle” cloak. The new cloak can conform to the shape of a cylindrical tube, hiding it from microwave detection.

According to Alù, the group began working on cloaking technology in 2005, though this week’s research stemmed from a paper he wrote in 2009.

“We have worked on invisibility since 2005, when we theoretically proposed the first concept to achieve transparency and invisibility using metamaterials,” Alù said. “The mantle cloaking idea was originally published in a theory paper by myself in 2009.”

Alù said the cloak works by keeping microwaves from reflecting, or “scattering,” after hitting an object. 

“We see an object by collecting with our eyes the waves that is scattered around by the object,” Alù said. “By designing a cover that scatters a wave with opposite phase compared to the object, we can cancel out the total scattered wave and suppress the detectability of the object.”

The cloak’s innovative design uses “metascreens” thinner than one millimeter. These metascreens consist of copper tape layered on a polycarbonate cover, which is essentially a transparency sheet, Melin said.

Rainwater said the mantle cloak effectiveness is still somewhat dependent on the viewing angle.

“Our cloak works better in some directions than others,” Rainwater said. “But roughly speaking, it’s about 90 percent dimmer with the cloak at the microwave frequency we designed it for.” 

Melin said he worked on cloaking with Alù and Rainwater while studying as an undergraduate. Melin clarified that the mantle cloak does not actually hide objects from light waves, only microwaves.

“This is not visible cloaking, this is not something like ‘there’s the object and now it’s gone.’ It’s a different part of the spectrum,” Melin said. “So if you’re talking about a Harry Potter cloak, yes that’s misleading.”

Going forward, Alù said invisibility research will focus on cloaking antennas, which could mitigate problems like radio interference.