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Print yourself a roll of semiconductors?

Xerox researchers use advanced printing techniques to create sheets of plastic transistors that could be used to build flexible LCDs.

Xerox's Palo Alto Research Center has developed a way to use inkjet printing techniques to create cheap, flexible sheets of transistors--a process that could radically change the way flat-panel screens are created.

The fabled technology lab is one of several facilities around the world that have been working to recreate the functions of traditional silicon semiconductor chips with tiny transistors printed on plastic sheets. Using electricity-conducting ink that bonds to a flexible plastic sheet, PARC researchers said Tuesday that they have been able to create arrays of bendable semiconductors that work much like their rigid counterparts.

The new printable chips aren't nearly as efficient as their silicon counterparts, but they work well enough to serve as the core of liquid crystal display (LCD) screens and futuristic displays such as electronic paper, the researchers said.

Instead of hugely expensive "clean room" manufacturing facilities, the products could be created in printing facilities that might more resemble a newspaper's printing press, with sheets of transistors scrolling off the high-tech printers, the scientists speculated.

"Instead of smocked people carrying individual (silicon) wafers around a clean room or robot arms carrying stacks of wafers, imagine a person carrying a roll that looks like a 35-millimeter camera cassette, with a roll of film a meter wide and a hundred feet long," said Raj Apte, a PARC research scientist working on the project. "The clean room might even be a dirty room, since the film is going to be on cassettes."

The drive for plastics that conduct electricity has gone on for years, as scientists look for ways to replace the capital-intensive process of traditional chip and display manufacturing. Several other companies' labs, including those of Lucent Technologies' Bell Labs and Philips Semiconductors, are also pursuing the concept.

As traditional chips get faster and smaller, the facilities that are eeded to produce them have become increasingly expensive. In the case of LCD screens, handling the large sheets of glass that are attached to semiconductors has sharply boosted the cost of the latest generation of manufacturing plants. A China-based facility for manufacturing LCD screens, jointly created by NEC and SVA, will cost more than $700 million to set up, for example.

By contrast, the new jet-printing process could mean that these manufacturing techniques can be substantially streamlined, particularly for display technologies, for which the most efficient, powerful chips aren't necessary.

The material for Xerox's version of semiconducting plastic-based ink was primarily developed by a team Canadian Xerox researcher Beng Ong leads. Previous generations of ink proved unstable and difficult to use in a production process.

For the last six months, the PARC team has been experimenting with ways of printing the ink onto a flexible plastic film. Because the transistors that are created are tiny, the printing process has to be extraordinarily precise. Researchers took advantage of some of Xerox's ordinary printing technology.

The work allowed the researchers to print sheets of functioning transistors with the ink. The next stage is to create a working display with the semiconductors, they said.

"Getting to a point where all the transistors in the array are functioning is going to take some development. Right now, we're at most, instead of all," Apte said. "Proving it by putting it on a display and showing a pretty picture is the next milestone."

The process is several years away from finding its way into production facilities, however. Xerox has not yet announced any plans to commercialize the process. Because PARC is now a partially independent subsidiary of Xerox, it could also work with outside companies or create a venture-funded spinoff to work on commercializing the procedure.