New device opens next chapter on E-paper

Imagine folding up today’s newspaper only to unroll it tomorrow and find

tomorrow’s news. Now, researchers have made a plastic electronic material that

could make such fantasies come true.

With the debut of electronic ink a few years ago, researchers took a step toward

meshing the data-handling power of electronics with the flexibility and

convenience of paper. Such inks, developed independently by teams at the

Massachusetts Institute of Technology (MIT) in Cambridge and Xerox’s Palo Alto

Research Center in California, contain particles that change a pixel’s color–say,

from black to white–when exposed to an electric current (SN: 6/20/98, p. 396).

Among the early uses of electronic ink were large, low-resolution store signs for

promoting sales. But creating paper-thin, high-resolution displays for electronic

newspapers, books, and even cereal boxes requires circuitry much more

sophisticated than that needed for store displays, says John A. Rogers of Lucent

Technologies in Murray Hill, N.J.

In the April 24 Proceedings of the National Academy of Sciences, Rogers’ team from

Lucent and E Ink Corp. of Cambridge, Mass., reports its use of simple, inexpensive

printing techniques to make the most capable E-paper yet.

“I think this is extraordinarily significant,” comments Joseph Jacobson, who led

the development of MIT’s electronic ink. “The real dream has been to have

electronic newspapers or electronic books that are manufactured in the way that

you would manufacture a regular book. . . . This is the first time that anybody

has manufactured all of the elements–meaning both the electronics and the display

itself–by printing.”

Conventional methods for patterning circuitry onto silicon wafers don’t work well

for creating complex circuits on flexible plastic. Instead, Rogers’ group used a

technique called microcontact printing to create arrays of transistors that

control the E-paper’s pixels.

The first step is to etch a desired circuitry pattern into a master stamp, which

the scientists then use to make the several reusable plastic stamps required for

production of the E-paper. Next, these stamps are “inked” with a sulfur-containing

organic compound, Rogers explains.

The researchers then press a stamp onto a plastic sheet coated in gold. The

transferred organic ink shields part of the gold film from an etching process that

removes the exposed gold. The researchers then remove the organic ink and add a

carbon-based semiconductor to the remaining gold. The semiconductor thus creates

an array of transistors in the pattern that was originally etched onto the master

stamp.

To Rogers, E-paper’s most powerful impact could be to supplant paper newspapers

and books. “You could imagine making an electronic version of a newspaper that

would consist of a single sheet of this electronic paper connected to the wireless

Internet,” says Rogers. “You could download information content, view it, interact

with it, and roll it up or fold it in the same way you can a conventional

newspaper, but you don’t have all the waste associated with a newspaper.”