Boffins promise large-scale nano-material manufacture

Scientists have demonstrated that a new 'soft lithography' technique can be used to manufacture complex nano-materials inexpensively on an industrial scale.

Research led by Northwestern University chemist Teri Odom has resulted in novel forms of advanced materials with "exceptional and unexpected" optical properties.

The new 'plasmonic metamaterials' are unique in that their physical properties originate from shape and structure rather than just material composition.

Two examples of meta-materials in the natural world are peacock feathers and butterfly wings.

Their brightly coloured patterns are due to structural variations at the level of just hundreds of nanometres which cause them to absorb or reflect light.

The new nano-manufacturing technique has allowed Odom and her colleagues to make gold film with virtually infinite arrays of circular perforations as small as 100 nanometres in diameter, or 500 to 1,000 times thinner than a human hair.

On a magnified scale, the perforated gold film looks like Swiss cheese except that the perforations are well ordered and can spread over macroscale distances.

The researchers' ability to make these optical meta-materials inexpensively and on large wafers or sheets is what sets this work apart from other techniques.

"One of the biggest problems with nano-materials has always been their scalability," said Odom, who is associate professor of chemistry in the Weinberg College of Arts and Sciences.

"It has been very difficult or prohibitively expensive to pattern them over areas larger than about one square millimetre.

"This research is exciting because it demonstrates a new type of patterning technique that is cheap, but can also produce very high quality optical materials with interesting properties."

The research appears in the September 2007 issue of Nature Nanotechnology.

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