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.
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.
With their newer processes for nano-based electro-static assembly, Lalli says her team of material chemists can “make something much thicker, in much less time” – a few millimeters per hour, instead of a few nanometers over the course of days. So, for example, you have a material that can actually be used to build an antenna or the joint of an airplane wing, not just a coating that can easily be worn off.
Out of that development, and after many variations using gold and silver, the most recent version of Metal Rubber came to fruition in mid-2004. And since then, the corporate and research world has come a-calling.
Aside from its relationship with Lockheed Martin, NanoSonic has worked with several government agencies, and has received funding from DARPA, NASA, the Ballistic Missile Defense Organization, and the Air Force. The company has been showing its latest invention around to several Fortune 500 companies, but Claus denied naming any specific ones.
Beyond its potential applications in aerospace and defense, Lalli sees opportunities for the material to be used in biomedical devices, artificial muscles, and electronic displays. Claus envisions the material being used for handheld electronics, prostheses, toys, or in any product or device where “you would need a flexible interconnect that has good electrical conductivity.”
“As far as I know, this is the first truly conductive stretchable plastic,” says Dr. Roy Kornbluh, a senior research engineer at SRI International, who specializes in the creation of artificial muscles. “The stretch-ability is of greatest interest to me.”
Kornbluh hopes to begin experimenting with the material in the near future, and sees two immediate uses for Metal Rubber in his work: it could be used as the conductive sheets needed to make one kind of artificial muscle; and it is an ideal material for making the large mirrors used in space for astronomy and other purposes.
Since these mirrors have to be large and as light as possible, Kornbluh believes a flexible and reflective material like Metal Rubber would be a good alternative.
NanoSonic still has some scale-up issues to deal with, especially if the company expects to garner more would-be customers for Metal Rubber. Even Claus admits that the “fabrication can be a challenge” since the company still takes a day and a half to make the 12-inch squares it shows as samples.
NanoSonic is looking into venture funding in the near-term, and may consider going public to raise capital to further develop its process. In the meantime, Claus believes that Metal Rubber may be used in products – be it toys or medical devices – that could hit the market as early as 2006.
But don’t count on buying that Metal Rubber MP3 player anytime soon.
Matthew Nordan, vice president of research for Lux Research, says he’s “not surprised NanoSonic is getting entreaties from the Lockheed Martins of the world.” But between costs for development and the conservative pace of many large manufacturers, it usually takes in upwards of 15 to 20 years to translate that interest into real-world products.
“It’s not about the ability to get meetings with…or requests for samples from big companies,” says Nordan. “It’s about getting commitments to ship and signed invoices.”
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