With new material, invisibility cloaks near reality

March 14th, 2009 - 3:11 pm ICT by IANS  

Washington, March 14 (IANS) Researchers have created a light-bending material that could be the key to high-powered optics, ultra-efficient solar cells and even invisibility cloaks, a la Harry Potter’s indispensable tool.
Nanophotonics scientist Naomi Halas and graduate student Nikolay Mirin at Rice University in Houston, Texas created a metamaterial that collects light from any direction and emits it in a single direction. It uses very tiny, cup-shaped particles called nanocups.

A metamaterial is a material that gains its properties from its structure rather than directly from its composition.

In earlier research, Mirin had been trying to make a thin gold film with nano-sized holes when it occurred to him that the knocked-out bits were worth investigating.

Previous work on gold nanocups gave researchers a sense of their properties, but until Mirin’s revelation, nobody had found a way to lock ensembles of isolated nanocups to preserve their matching orientation, said a Rice University release.

“The truth is a lot of exciting science actually does fall into your lap by accident,” said Halas.

“The big breakthrough here was being able to lift the nanocups off a structure and preserve their orientation. Then we could look specifically at the properties of these oriented nanostructures,” he added.

Mirin’s solution involved thin layers of gold deposited from various angles onto polystyrene or latex nanoparticles that had been distributed randomly on a glass substrate.

The cups that formed around the particles - and the dielectric particles themselves - were locked into an elastomer and lifted off of the substrate. “You end up with this transparent thing with structures all oriented the same way,” said Mirin.

In other words, he had a metamaterial, a substance that gets its properties from its structure and not its composition.

Halas and Mirin found their new material particularly adept at capturing light from any direction and focusing it in a single direction.

Redirecting scattered light means none of it bounces off the metamaterial back into the eye of an observer. That essentially makes the material invisible. “Ideally, one should see exactly what is behind an object,” said Mirin.

The study appeared in a recent edition of Nano Letters.

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