What alchemy makes images on paper move? The secret, Jerome Rubin explains, is in the ink: "an ink that will enable you to turn any surface you coat it on--paper, plastic, fabric--into the equivalent of a computer screen.
"Imagine a huge number of microcapsules," he says, "maybe 40 microns in diameter, each half-filled with tiny particles of titanium dioxide, which are white, and half-filled with dye--black, blue, whatever. Then you have an electric charge on the surface, provided, typically, by a thin film transistor. The electric charge rotates the capsules, depending on whether it is positive or negative. Normally the white sides are up and you have what looks like a piece of white paper. When a new charge draws the black sides to the surface, you get an image, a pattern of letters and drawings.
"The tricky thing about developing true electronic paper is developing a flexible back-plane--which would probably sit on a piece of plastic about the thickness of a sheet of plastic wrap. Some coating might be necessary to protect the ink, but the whole thing probably wouldn't be much thicker than a piece of coated paper in a magazine.
"An electronic book with electronic paper would have multiple sheets, 40 or 50, so you could read multiple pages and flip around. Inside the spine, you'd have a tiny microprocessor that would deliver instructions to the separate pages. You could receive the texts either over the Net or by wireless--of course, the Net will probably be wireless in 10 years, anyway--or you might have some flash memory to slip into the spine of the book. That way you can go on a holiday with 50 books loaded onto your card."
