ou are surrounded by display surfaces. The wallpaper on your walls, the calendar blotter on your desktop, this page are all conveying visual information. The problem is that once you have printed your wallpaper, calendar, or magazine that's it, you can't change it. Computer screens allow you to infinitely change what is displayed, but PC monitors are small and definitely not portable, and laptop screens are hard to read. The obvious solution to these problems is to combine the convenience and portability of paper with the flexibility of electronic displays. This is easier said than done, however. Since the 1970s, researchers have been searching for a solution.

The pattern on your wallpaper and the text on a piece of paper or monitor can be created by aligning thousands of tiny ink dots or pixels into the required pattern. The letters you are reading right now contain 2,400 ink dots per inch. If you could manufacture paper-thin, flexible electronic displays containing thousands of particles--the ink--and devise a method to get the particles to align, hold that alignment, and then realign themselves for the next page, you will have combined the best of both the paper and electronic worlds. But the trick is to get the electronic paper, like the proverbial leopard, to change its spots. Today, a Xerox researcher believes he has created such a beast.


Get Ready for Gyricon

Gyricon (the Greek gyro, meaning rotate, combined with icon, meaning an image) is the name of the display technology that Nicholas Sheridon--a senior research fellow at the Xerox Palo Alto Advanced Research Center, Palo Alto, CA--believes will revolutionize how information is displayed. The technology, says Sheridon, is so flexible that it could be used to create electronic books, electronic newspapers, even electronic wallpaper.

"We can make a very large display--say, 4 feet by 20 feet, or larger--so you can paper a wall, then several months later change it. Actually, it's incredible the number of uses for this display."

The Gyricon display consists of thousands of tiny half black, half white (bichromal) balls inside a clear thin elastomer sheet. To create the sheet, 100-micron-diameter [about the thickness of a human hair] balls are dispersed throughout an uncured elastomer. With the balls in place, the sheet is cured and subsequently soaked in a low-viscosity oil, which causes the elastomer to swell and form oil-filled cavities around each ball. Once each ball is floating in its own pocket of oil, it is able to rotate in response to an electrical field.

The swollen sheets are next placed between substrates (glass or plastic) carrying addressing electrodes like those used in liquid crystal displays. The electrodes act as a kind of switching circuit that tells the Gyricon balls when to rotate.

"One polarity of field will cause the white hemispheres to face a viewing window while the other polarity will allow the black hemispheres to be seen," says Sheridon.

To create letters or an image, tiny electric charges are sent to each capsule, which responds independently. As each particle flips to its assigned color, the larger picture emerges--much like how individuals at a stadium flip over small pieces of cardboard to create enormous images. Researchers are aiming for a resolution of from 400 to 600 dots per inch--laser printer quality--but they haven't achieved this resolution yet.

How did Sheridon, who holds a master's degree in physics from Wayne State University, Detroit, MI, get the idea for the Gyricon? "In the seventies, I worked on a display for a year and a half and published a paper in IEEE Transactions on Electronic Devices Journal. When I first did the work, I actually got white glass balls from a glass company and evaporated a black coating on those using a vacuum system. The display's balls didn't rotate too well, so it wasn't very practical.

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