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 user 2005-02-05 at 10:46:00 am Views: 116
  • #10067
    One Word: Plastics
    It’s not just for Tupperware anymore — it can be used to make microchips too.

    Back in 1958, when Jack Kilby and Robert Noyce invented the integrated circuit, its transistors were made from metal and silicon. Today’s integrated circuits are forged from the same materials, even though they contain many more millions of transistors and have to be painstakingly fabricated in billion-dollar manufacturing plants. But that might soon change. There’s a growing scientific movement afoot to build circuits made entirely from new materials. Forget about the rigid metals of old. Now — to borrow a line from The Graduate — it’s all about one word: Plastics.

    There’s a lot to be said for plastic circuits, which could be used to create flexible, lightweight, and dirt-cheap computer displays and electronics. For years, the plastic printable circuit has been one of those gee-whiz ideas that scientists like to bat around. There has been just one problem: Plastic has not, by and large, been thought to be conductive — in fact, it has usually been used as an insulator. But a breakthrough on that front came in the late 1970s, when three scientists separately demonstrated that plastic could indeed be made to conduct electricity by manipulating its molecular structure. (Those scientists — Alan Heeger, Alan MacDiarmid, and Hideki Shirakawa — shared the Nobel Prize in chemistry last year for their groundbreaking work.) Building on their findings, researchers continued to make advances at other institutions, such as Cambridge, IBM, Kodak, Lucent’s Bell Labs, Princeton, and Xerox PARC. Engineers imbued certain polymers with either conducting or semiconducting properties.

    From there, it was a short step to the notion of a plastic circuit — which would be much easier to build than a traditional microchip. Consider this: The way you make a standard chip is to layer thin sheets of silicon (a semiconductor) and aluminum (a conductor) on top of one another. Then you etch into this wafer, scraping away microscopic bits of metal until only the desired circuits remain. But if your semiconductor and conductor are both plastic, there’s no need for expensive lithography or etching. Instead of multimillion-dollar semiconductor manufacturing equipment, all you would need is a device not much different from an ink-jet printer. Raj Apte, who heads up the printed organic electronics project at Xerox PARC, explains that “the toner in a laser printer is basically a plastic.” Thus, in order to create a plastic microchip, all you would need to do is fill a printer’s toner cartridge with conducting or semiconducting plastics, then spray them out in layers on top of one another. “The ink jet can squirt the semiconducting plastic exactly where you want it,” Apte reasons. “Then the conducting plastic will go exactly where you want it, and then you are done.”

    This is all theory, but Apte is working with Dow Chemical and Motorola to come up with ways to put his ideas into practice; he is also working with other organic semiconductors made from nonplastic molecules. Apte believes that printable transistors will soon be good enough for commercial use in light-emitting diode and active-matrix displays, which are actually very simple forms of electronic circuits. Right now, those displays have to be made of glass, since it is extremely difficult to print conventional silicon-and-metal circuits onto plastic without melting it. But if the circuits aren’t made of silicon and metal, there’s no need to use glass — the whole display could be made out of plastic. Alan Heeger, one of those three chemistry Nobel laureates, has been working toward that goal; his company, Uniax, has already produced a prototype of a light-emitting diode display made of plastic. (The company was bought last year by DuPont.) Within the next three years, Apte thinks, we could see many more plastic displays on the market.

    It’s an appealing notion: If computer displays could be made from plastic instead of glass, they would be lighter, cheaper, and more rugged. They also would be flexible. Imagine a large sheet of plastic that could download your favorite newspapers and that you could roll up and carry underneath your arm. Of course, such a display would still have to be connected somehow to a power source. But reading articles in digital form might no longer be such an eye-straining, back-hunching task. And even if the rollable digital newspaper never comes to pass, there are plenty of other products in which a plastic display would come in handy. Cell-phone manufacturers are seriously looking into using plastic displays, a vast improvement over their current screens.

    And plastic screens would just be the start — these circuits could have all sorts of other uses. For instance, more complicated circuits could be configured to emit radio frequencies, which would allow them to replace bar codes. UPS, for one, would love to use such technology. In February, UPS vice chairman Mike Eskew mentioned to me that UPS’s venture fund had invested in a private company called Savi Technology in order to keep an eye on this emerging field. “We scan everything,” he said, referring to the bar codes on every UPS package. “It is expensive to scan, and time-consuming.” Currently it is too expensive to put a radio-transmitting chip on every one of the more than 13 million packages UPS ships each day. “If it costs $1 to produce a [radio-frequency] tag, then we can’t afford it,” Eskew said. “But when it gets down to one penny and it is produced by the ink from a printer_” He didn’t have to spell it out. Packages that call out their location are easier to keep track of than packages that don’t.

    These are just two possible applications of this new technology; who knows what other ones we could come up with, once plastic circuitry becomes more commonplace? Assuming that scientists can work out all the kinks, as the transistors on these chips get smaller, their uses will blossom. They may never be as powerful as the most up-to-date Pentiums, but one day, plastic chips may become far, far more ubiquitous.