Before paper-a Chinese invention, sent to Europe by the Arabs-Europeans wrote manuscripts on vellum and parchment, which were made from, respectively, lambskin and sheepskin. (The terms are inexact; sometimes goats or calves provided the raw material.) Although animal hides could be shaved into sheets of amazing thinness, they were expensive, did not take ink well and were generally too brittle to pass through a press. Even if skins could be printed on, large editions would necessitate mass slaughter: the historian Aloys Ruppel once calculated that stamping out a hundred copies of the Gutenberg Bible on vellum would have consumed 15,000 lambs. Only when paper became widespread on the Continent did printed books become technically and economically feasible.The history of electronic paper is shorter and less colorful, but as a historian might say, it is not devoid of incident. Perhaps the first researcher to consider electronic paper seriously was Nick Sheridon, a physicist at Xerox’s Palo Alto Research Center (PARC), birthplace of the mouse-and-windows computer interface. In 1975, when Sheridon joined PARC, he noticed a paradox. His colleagues at PARC were excitedly imagining a future world in which printed books and magazines would be supplanted by computer displays. But the monitors actually used at PARC-bulky devices with green-and-white displays-had such poor contrast that researchers often had to draw their blinds to see what they were doing. “A Newsweek or Time that was replaced by a flat version of one of those computer monitors would have been almost unreadable,” Sheridon says. “I thought, I guess, that instead of replacing paper with the monitor, it might be smarter to replace the monitor with paper.”
Quickly he came up with a possible means, which he called Gyricon, from the Greek for “rotating image.” In its present incarnation, Gyricon is a transparent silicone-rubber sheet in which are embedded thousands of tiny plastic spheres, each smaller in diameter than a human hair. Each sphere has a black half, which carries a very small static electricity charge, and a white half, which is electrically neutral. If an electric field comes near the spheres, it attracts or repels their black halves, causing the spheres to rotate. If the white halves end up tilting toward the upper side of the rubber sheet, the viewer sees white dots; if the black halves face the viewer, the dots are black. Placing a Gyricon sheet between the same types of circuit that control the pixels on a laptop screen will arrange the spheres in much the same way, creating a black-and-white image.
Soon Sheridon had a crude working model. Resembling a country cousin of the Etch A Sketch, it could produce an X for Xerox. He thought it would be ready for the market around 1985, if he could just lick a few practical problems. Foremost among them was a manufacturing question: while Sheridon had devised a means of fabricating the little balls, it did not yield uniform spheres; he found himself poking through the tiny globes, looking for good ones.
Another, more daunting, problem lay ahead. The rubber sheet had to be controlled, or addressed, by the electrodes on a circuit board, and all known flat-circuit display boards were stiff and inflexible-totally unlike paper. Worse, they were expensive. Indeed, such circuitry was (and is) the reason laptops cost more than regular computers. As a result, the Gyricon prototype was more like a rigid, expensive electronic clipboard than a bendable, cheap sheet of paper. Unable to see much value in research that seemed to be producing a pricey black-and-white-only substitute for laptop screens, Xerox pulled Sheridon away from e-paper in 1977.
Years later, in the mid-1990s, a young physicist named Joseph Jacobson joined the Media Lab at MIT (see “Print Your Next PC,” TR November/December 2000). He, too, had been thinking about electronic paper. With two students, he set about duplicating Sheridon’s work. But the MIT group, too, couldn’t make the black-and-white balls come out right. Instead, they came up with a variant of the idea. Like Sheridon, the MIT group uses a thin sheet of rubbery plastic crammed full of tiny spheres. But these spheres are not solid; they are hollow capsules filled with colored oil and small, electrically charged chips of titanium dioxide paint. When a current passes near the sheet, it pushes or pulls the chips up or down, coloring the top of the capsules, which thus act like pixels on a monitor. In 1997 Jacobson and his two students co-founded E Ink, which has attracted more than $50 million in venture capital.