Flexible E-Paper: Plastic circuits drive paperlike displays
Alexandra Goho
In a major step toward electronic paper that works like a computer monitor
yet feels and behaves like a page of a book, researchers in the Netherlands have
made electronic-ink displays on flexible plastic sheets.
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ROLL WITH IT. Future electronic displays could look and feel
more like paper.
Polymer
Vision/Philips |
A U.S. company developed the electronic ink over the past several years.
"Just like your newspaper, you can see it in bright light, dim light, or from
all angles," says Michael McCreary of E Ink in Cambridge, Mass.
The ink consists of millions of microcapsules, each one containing white and
black pigments of opposite charge (SN: 6/20/98, p. 396: http://www.sciencenews.org/sn_arc98/6_20_98/bob2.htm).
When a certain voltage is applied, the white pigments rise to the surface and
the black ones descend out of sight. An opposite voltage leads to black pigments
on top. Each pixel in the display is controlled by its own silicon-based
transistor.
Until now, glass substrates that contain all the circuitry needed to drive
the pixels have made the displays seem like very thin monitors. However,
researchers at Philips Research Laboratories in Eindhoven, the Netherlands, have
figured out how to make the circuitry flexible and paper-thin. The result: a
display that a person can bend, roll, and even drop without fear of breaking it.
To achieve this, the Philips team made transistors out of electrically
conducting polymers instead of silicon. The researchers patterned all the
circuitry, including the transistors, onto sheets of plastic 25 microns thick.
In collaboration with E Ink, they laminated electronic ink to the plastic sheet,
aligning the display pixels with the transistors. The researchers describe their
work in the February Nature Materials.
"This is a significant step toward display systems on plastic," says
electrical engineer Ananth Dodabalapur of the University of Texas at Austin.
In a show of muscle, the Philips group has produced displays with close to
80,000 pixels, which the researchers claim are the largest and thinnest polymer
electronics-based displays fabricated to date.
The researchers have made displays from electronic inks that can switch to a
new frame of text or a new image only a few times each second. That's too slow
for video, which requires dozens of frames per second. Even so, says McCreary,
"there is no fundamental reason why electronic ink will not be able to switch at
video rates in the future."
Flexible electronic-paper products should be on the market in the next couple
of years, says Bas Van Rens, general manager of the group that will
commercialize the new display technology for Philips. One such product could be
a display that rolls into a pen and can be carried around in a shirt pocket.
"Then, if you want to read your e-mail or browse the Internet, you pull out the
pen and roll out the display," he says.
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References:
Gelinck, G.H. . . . B.J.E. Van Rens, et al. In press.
Flexible active-matrix displays and shift registers based on solution-processed
organic transistors. Nature Materials. Abstract available at http://dx.doi.org/10.1038/nmat1061.
Further Readings:
Gorman, J. 2001. New device opens next chapter on E-paper.
Science News 159(April 28):262. Available at http://www.sciencenews.org/20010428/fob5.asp.
Peterson, I. 1999. Electronic ink debuts in store signs.
Science News 155(May 29):347. References and sources available at http://www.sciencenews.org/sn_arc99/5_29_99/note8ref.htm.
______. 1998. Rethinking ink. Science News 153(June
20):396-397. Available at http://www.sciencenews.org/sn_arc98/6_20_98/bob2.htm.
Weiss, P. 2003. The daily flicks: Morphing ink may bring
video to newspapers. Science News 165(Sept. 27):195. Available at http://www.sciencenews.org/20030927/fob1.asp.
Sources:
Ananth Dodabalapur
Microelectronics Research
Center
University of Texas, Austin
JJ Pickle Research Campus
10100
Burnet Road
Austin, TX 78768
Michael D. McCreary
E Ink Corporation
733 Concord
Avenue
Cambridge, MA 02138
Bas J.E. Van Rens
Philips Research Laboratories
Prof.
Holstlaan 4
5656AA Eindhoven
The Netherlands
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