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Carbon nanotubes promise stronger touchscreens

Posted: 02 Aug 2007 ?? ?Print Version ?Bookmark and Share

Keywords:carbon nanotubes? stronger touchscreens? thin films?

Arrowhead Research Corp. subsidiary Unidym Inc. claims its transparent nanotube-based thin films will enable CE devices like Nintendo's handheld video games to use a more durable touchscreen that combines the stronger-than-steel properties of carbon nanotubes with the transparency of exotic indium-based films. With its carbon-nanotube-based thin films, Unidym is trying to claim a segment of the over-$1-billion market for transparent electronics today.

Nobel worthy
Earlier this year, Unidym Inc. merged with Carbon Nanotechnologies Inc., the company founded by the late Rice University professor Richard Smalley, who received the Nobel Prize for his pioneering work in carbon nanotubes. Now Unidym, with its combined portfolio of hundreds of nanotube patents, reports progress toward making tough nanotube thin films that can replace transparent indium-based films with cheaper more durable carbon-based materials.

"With our combined facilities in Houston [Texas] and Menlo Park [California], we are developing a variety of carbon nanotube-based films for the electronics industry," said Jon Miller, VP of business development at Unidym.

The company's first product is a transparent film produced at room temperature using inexpensive roll-to-roll manufacturing techniques to replace the vacuum chamber sputtering process required for the transparent indium tin oxide (ITO) electrodes used today in flat-panel displays, touchscreens, solar cells and solid-state lighting.

Unidym recently announced a joint-development agreement with Japan-based Touch Panel Laboratories, under which the two companies will perfect tough carbon-nanotube-based films that can function as well as the ITO-based panels made today, but be much more durable. Nanotubes are stronger than steel and yet extremely lightweight, making their films an almost ideal combination of strength and light weight.

"We are working toward a more durable touch panel for Nintendo with Touch Panel Laboratories," said Miller.

How it works
Unidym manufactures its own nanotubes at a facility in Houston, creating a black powder composed of a mixture of semiconducting and metallic nanotubes. To make its films, then, all it has to do is make a solution of the black powder in water and use room-temperature deposition to spray the mixture on the substrate.

"We can deposit films on almost any substrate, but we usually put them on glass or plastic," said Miller.

Unidym is working on methods to select just the metallic or just the semiconducting nanotubes when making its powders, but today it tunes its films' semiconducting or metallic properties by adjusting the density of the nanotubes. Currently, they are making films not only for touchscreens, but also for LCDs and solar panels.

"We can make films that are either conducting or semiconducting by changing the density of the nanotubes," said Miller. "For instance, for our work on LCD displays and solar panels, we need a highly conductive film, but for touch panels they don't need to be quite as conductive."

Lower cost, better yields
Miller claims that these films also offer a lower cost for the manufacturers of LCD displays and solar panels. In addition, nanotube films outperform ITO films, in addition to offering better yields.

Unidym's second product will be a carbon nanotube-based TFT that will enable room-temperature spray-on electronics to be manufactured on inexpensive flexible substrates using printing technologies instead of the vacuum deposition required for silicon-based electronics.

Unidym is also developing carbon-based electrodes for fuel cells, as well as researching graphene films, which use a similar carbon-based chemical structure, but instead of rolling up the material into tubes, lays it out in planes.

- R. Colin Johnson
EE Times

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