Scientists develop new organic digital storage devices

Princeton researchers have proven that inorganic storage devices are so dead.

In a paper published last week in the journal Nature, a group of scientists, including two Princeton researchers, described a new technology that could lead to a new inexpensive and effective way of storing digital data.

"The field it would play would be digital cameras, like flash [cards]," said Sven Moller, coauthor of the paper and a former postdoctoral researcher at Princeton.

The technology is based on a newly discovered property of PEDOT, a common polymer plastic that has long been used as a coating on photographic film, according to the University press release on the research.

The researchers found that although PEDOT is normally conductive, when subjected to large currents the polymer blows like a fuse and loses its conductivity.

At the lowest level, all digital information is stored as a series of ones and zeros. In layers of grids of small PEDOT cells, broken "fuses" represent one state, while working ones represent the other.

A pattern is imprinted on a PEDOT device by exposing certain fuses to high voltages, making them unable to conduct current. When a lower voltage is then applied to the device, those fuses that could not conduct current are read as zeros, while working fuses act as ones.

Burning out the fuses is an irreversible process, so the device functions as ROM — read only memory. Like most CDs, it can only be written to once. After that, the data is locked into place and a new medium must be used to record more information.

A one cubic centimeter grid of PEDOT could store more than one gigabyte of information. CDs hold less than one gigabyte of information.

Because PEDOT devices have no moving parts, they are very small and require no power to maintain the data that they hold. These features make them ideal for use in digital cameras and other appliances where power consumption and breakability are primary concerns.

But don't expect to see devices employing this technology in Radioshack anytime soon. Though the discovery is promising, commercial applications are years away, said Moller, who now works for Hewlett-Packard.

"The research stage is at a point that does not touch any of the issues that are important for commercialization for such a product," Moller said.

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Moller predicts that PEDOT storage devices could not appear on the market in under five years. "On the technical side, a lot has to be done."

After the remaining technological difficulties are overcome, PEDOT devices must be economically competitive before they hit the marketplace. Though the technology is new, it will be competing against existing storage devices. Its success will depend on how expensive and easy it is to manufacture.

"If it's going to be a viable technology the advantage has to be cost. If it's cheaper, then there is a chance," he said.

Most storage devices today are entirely inorganic. Although some research has been done in molecular computing, the PEDOT-based storage device is one of the first important products that combines the two. It should help pave the way for research about such hybrid devices, said Moller.

"It is a functional device that has both inorganic and organic materials in it, silicon and a polymer. That is something that is fairly new, and I think it is a field that will grow in the next years," he said.

Companies are also researching hybrid storage devices, he said, including major chip manufacturers Intel and AMD. This new technology can be used as a model for other combinations of silicon and polymers.

While at Princeton, Moller worked on the new technology in the lab of electrical engineering professor Steven Forrest, also a coauthor of the paper.

Forrest has been researching other technologies which are likely to hit the commercial market possibly within the decade.

He developed organic light emitting diodes — paper thin, bendable sandwiches of organic materials that can be used to make tiny, flexible computer displays.

Universal Display Corporation, based in Ewing, N.J., is now developing the technology with plans to commercialize it.

OLEDs, like PEDOT, make use of organic molecules for digital applications that have until now relied on inorganic materials.

"It's a very fundamental advance — it's an advance based on fundamental science that has very obvious and important industrial applications," said electrical engineering professor James Strum, the director of the new Princeton Institute for Science and Technology of Materials. "There are many groups around the world who are looking at electrical switching applications of organic materials and that's what makes this an important invention."