Miniature invisibility cloak that can conceal 3-D objects by refracting light waves.

Scientists at the Berkeley Lab and UC Berkeley have created an invisibility cloak made from a thin material covered with millions of gold-plated antennae which wraps around an object and uses the antennae to divert light waves from its surface, rendering it undetectable to the human eye. Light reflects off the cloak as if it were reflecting off a flat mirror.

Unlike the fictional character, the ultrathin cloak is real, and it successfully concealed microscopic 3D objects from detection in visible light..

“This is the first time a 3D object of arbitrary shape has been cloaked from visible light,” said Xiang Zhang, a UC Berkeley professor of mechanical engineering and director of Berkeley Lab’s Materials Sciences Division. “Our ultra-thin cloak now looks like a coat. It is easy to design and implement, and is potentially scalable for hiding macroscopic objects.”

The scientists used gold nanoantennas to form the 80-nanometer-thick cloak, which conformed to the arbitrary bumps and dents in the 1,300-square-micrometer sample object. The cloak, a metamaterial engineered to bend light in ways not seen in nature, was able to reflect red light as if it were bouncing off a flat mirror.

The principles used to conceal the microscopic object should be possible to scale up to work with macroscopic items, said Zhang.

The prototype is about 80 nanometers wideor or one-thousandth the size of a single human hair. Tiny antennae act like a mirror to control the propagation of light to conceal the object underneath. The material itself is similar to a thin piece of cloth.

“This is probably closer to Harry Potter’s cloak,” Zhang said. “It’s like a T-shirt you can wear.”

What makes this latest invisibility cloak especially encouraging is its collection of mirrors and their ability to conform to object of arbitrary dimensions.

“A phase shift provided by each individual nanoantenna fully restores both the wavefront and the phase of the scattered light so that the object remains perfectly hidden,” explains study co-lead Zi Jing Wong

The cloak also has an On/Off switch, which is as simple as reversing the fabric’s polarity to create the illusion or to seemingly materialize in front of an unwitting person.

While the experiment was capable of concealing a particle that was microscopic in size, researchers said it may be able to cloak larger objects as soon as five years from now. Currently, the thickness of the cloak is ideal, so researchers plan to expand the surface area of future models.

According to Zhang, there are many potential future applications of the technology. It could eliminate blind spots by making metal frames of cars transparent. Alternatively, the military may be able to use the technology to hide planes or tanks. Wrinkles and blemishes could be concealed with a design that would mold to the wearer’s features.


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