Testing Their Metal

Using nanotechnology, scientists at a small Virginia start-up have created a new polymer that incorporates the best that both metal and rubber have to offer -- opening the door to a more flexible future.

It's a material chemist's version of the riddle of the Sphinx: What substance can conduct electricity like a metal, yet also stretch like a rubber band?

Earlier this year, a team of researchers at a Blacksburg, Virginia company called NanoSonic found the answer in Metal Rubber, a filmy brown material that can extend to three times its original length and conduct electricity as well as a bar of steel, says NanoSonic founder Dr. Rick Claus.

Few major companies have yet stepped up to announce any official plans for the novel new polymer, but SRI International may experiment with Metal Rubber to construct artificial muscles and astronomical mirrors, and reports say that Lockheed Martin is using it to create aircraft wings with more give.

Yet, there are huge potential ramifications for everything from jet liners to medical devices. Think flexible circuits and displays that take your laptop and cell phone to the next level of shock resistance. Or artificial limbs that can bend like their real counterparts.

Indeed, there is a rising interest and support for this new-wave of materials as President Bush last December authorized $3.7 billion in funding for nanotechnology research.

NanoSonic hopes to capture their piece of that market by underscoring Metal Rubber's various benefits. Besides its conductivity and flexibility, it's much lighter than metal, weighing less than one percent of its steel equivalent. And when produced in large quantities, Claus expects Metal Rubber will be about one-thousandth the price of a comparable all-metal conductor.

Like many inventions, NanoSonic's team didn't so much set out to create this new material explicitly, but more stumbled across their big find while working on other projects for the U.S. Air Force.

"No one would actually fund you to make Metal Rubber," Claus says.

Since its inception in 1998, NanoSonic has focused on creating new materials through molecular self-assembly. By alternately depositing molecules with a positive or negative electric charge on a substrate such as glass or plastic, these tiny building machines can layer together a new material that draws from different substances on a molecular level.

Metal Rubber is a plastic polymer with metal ions, and one of the "nano-advantages," as Claus says, is that it only needs around one percent of metal content to make it conductive -- allowing the material to maintain elasticity, and keeping the costly metal component low.

Originally, this molecular layering process, known as electro-static assembly, would take days to produce super-thin films that were perhaps one-thousandth as thick as a hair.

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What makes Metal Rubber unique is not only that it combines such diverse properties, but also that it puts them together in a thicker, more usable real-world material -- not just a thin coating.

While the key to that breakthrough remains the veritable secret sauce of NanoSonic's Metal Rubber, Jennifer Lalli, the company's director of nanocomposites, says her team had been testing for two years to build a better polymer process.