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.”
