SICK of your old wallpaper? Why not just flip a switch and create a new pattern? Or download the latest designs from the Internet, try them for a few days, and then pick one you like?

Science fiction, of course. But it may not be so for much longer. A dozen companies around the world are developing a material that is supposed to have all the advantages of traditional paper without its biggest drawback—that you cannot easily reuse it.

Though the underlying concept of “electronic paper”—or, perhaps more accurately, “electronic ink”, is 20 years old, it is only now that firms have started to move from researching the idea to developing it into a marketable product. Earlier this month, E Ink, a small company based in Cambridge, Massachusetts, and Lucent Technologies, a rather larger company based in New Jersey, announced plans to develop electronic paper into something that people could actually buy. They were following in the wake of Xerox and 3M, which agreed in June to bring to market “a digital document display with the portability of a plain sheet of paper”.
 An awful lot of ballsContests between standards are often sources of irritation for outsiders, but for the participants they are deadly serious. The prize here will be a share of both the computer-display market (currently $18 billion a year) and the paper market (another $18 billion for newsprint alone). Even a small percentage of those sums will be big money. And, since the two consortia are using incompatible approaches, it is likely that only one will prevail.There are some similarities, however. Both E Ink and Xerox have worked out ways to make tiny balls, embed them into or apply them on to a thin supporting material, and then turn them black or white at the touch of a button, thereby forming text or graphics. And critically, in contrast to existing electronic displays, the images thus created do not disappear if the power is turned off.

The two consortia, however, achieve the effect in rather different ways. Xerox’s technology, developed by Nicholas Sheridon, a researcher at Xerox PARC, the firm’s research laboratory in Silicon Valley, is known as Gyricon—an adaptation of the Greek root “gyro”, to rotate. It uses beads that are a tenth of a millimetre in diameter. Each bead is black on one side and white on the other. Each is also “dipolar”, meaning one hemisphere can carry a slightly stronger electric charge (in this case, positive) than the other. That means that the beads will turn and turn about if an electrical field is applied to them.

E Ink, by contrast, uses tiny plastic capsules. These were invented by Joseph Jacobson, a researcher at the Massachusetts Institute of Technology’s well-known Media Lab, who is one of the company’s founders. The capsules, also a tenth of a millimetre across, are filled with dark ink and particles of white paint. In this case it is the paint that carries the positive charge. Electrodes located behind the capsules can therefore attract or repel the particles. If those particles have been pushed to the top of a capsule, it appears white. If they have been pulled down to the bottom, it appears black.

Both technologies seem to work well, and can sustain millions of rewritings. But they do not yet match the quality of paper. Dr Sheridon and his colleagues have created prototype displays with more than 200 dots per inch (80 dots per centimetre)—about twice as fine a resolution as most laptop screens, but only half as clear as a decent laser printer. In the not-too-distant future, however, they hope to achieve the brightness and contrast of traditional newsprint.

E Ink seems to be further along. The company has already embarked on a commercial demonstration of its technology. In May, it installed an experimental display, called Immedia, in a store belonging to J.C. Penney, a large American retail chain. The sign, which is about 1.8 metres high and 1.2 metres across, is less than three millimetres thick and weighs only four kilograms. Its message can be altered instantly via a wireless connection similar to that of a pager.

As important as the technology itself, both Xerox and E Ink have come up with ways to mass-produce digital paper cheaply. Dr Sheridon has invented an apparatus that can produce several litres of plastic beads a day. It is a palm-sized steel disk set on a spindle. The disk is set spinning at about 3,000 revolutions a minute. White molten plastic is then pumped on to the top of the disk, and black plastic on to the bottom. Centrifugal force causes both materials to move to the edge of the disk. Here they join up and are hurled away, forming tiny two-coloured balls.

The “paper” in which the beads are embedded is actually silicon rubber. Once the beads have been mixed into the liquid rubber, it is rolled out into a thin film and cut into sheets. The sheets are then soaked in oil, which penetrates the rubber and creates oil-filled cavities around each of the balls, allowing them to rotate freely.

E Ink’s task was somewhat easier. It was able to adapt the microencapsulation techniques used to make, for example, scratch-and-sniff perfume advertisements and carbonless copy paper. And because the company uses capsules rather than beads, it can mix them with a binding agent and print its electronic ink on to almost any surface, just as though it were real ink.

E Ink also intends to print the circuitry that runs the display on to its electronic paper. That is why the company has teamed up with Lucent. Bell Labs, Lucent’s research division, has recently developed flexible computer circuits and transistors that can be printed on to thin sheets of plastic using a method similar to silk-screening T-shirts.

It is too early to say which of these approaches will prevail. Indeed, other technologies, many of them still pretty outlandish, could eventually triumph over both.

One being investigated at Bell Labs, for example, relies on a protein called bacteriorhodopsin—which, as its name suggests, originates from certain species of bacteria. Bacteriorhodopsin has the habit of changing from blue to pale yellow in an electric field, which might be useful in colour displays. At this stage, however, using the protein that way could turn reading into a truly electrifying experience: a charge of about 4,000 volts is needed to trigger the colour change.

In any case, it will take at least five years before people will be able to read The Economist on electronic paper. E Ink expects its products to appear first in retail stores where they might, for example, replace traditional price tags with ones that keep up with inflation or down with deflation.

Next on the company’s list are displays for handheld computers and other electronic devices. Electronic paper could make these even lighter—and changing or recharging batteries could become a thing of the past. That is because electronic paper does not need backlighting in the way that liquid-crystal displays do and making beads or capsules change colour does not take much energy. Tomorrow’s handheld devices could therefore be powered by solar cells in much the same way that many of today’s calculators are.

Gutenberg’s successors are already working on more paperlike applications. Dr Sheridon has come up with a so-called wand—an electronic stick that can hold ten full-size books and also transfer text on to a sheet of Gyricon if a user runs the wand over the surface like a handheld scanner. He estimates that the wand will cost about $100 and a Gyricon sheet about $1, which would make the combination cheap enough to be used even in developing countries.

Dr Jacobson, for his part, is working on the modestly titled “Last Book”. This is several hundred pages of electronic paper bound together, with a computer concealed in the spine. It could, in principle, store entire libraries. A reader of this device would scroll through the list of works available. When he selected one, the text would instantly appear on the book’s pages. Dr Jacobson expects these ultimate tomes to retail for between $500 and $1,000.

If the technology doesn’t flop, human inventiveness will doubtless come up with even more creative applications. Digital wallpaper could be one of them; electronic billboards covering entire skyscrapers another. Even clothing might be dyed with digital ink, allowing it to adapt its design to the mood of the wearer. That would give an entirely new meaning to the expression “I can read you like a book.”

See E Ink’s and Xerox’s websites for details about the two technologies. More information about electronic paper and books is available from IBM; the Massachusetts Institute of Technology; Bell Labs; and ScienceNewsOnline.