shows electronic paper potential
Technology Research News
Computers, someone said, will never replace
newspapers because you can’t use a computer to swat a fly. This wry observation
may not hold true for long, however.
Researchers at Lucent Technologies’ Bell Labs and E Ink have created electronic
displays comparable to what the computer monitor was originally intended
to replace: paper. So, in a few years, your electronic newspaper may be
able to swat that fly and do everything a computer monitor can.
Real paper has all the characteristics electronic paper would like to
emulate: low cost, flexibility, mobility, good image resolution, and contrast
that doesn’t change with the viewing angle. Perhaps most importantly,
paper does not require power in order to display text or images.
Researchers at Bell Labs have used plastic to create an electronic paper
that is bendable, unbreakable, lightweight, low cost, and very low power.
In short, it’s a reasonable stand-in for paper.
The researchers’ brand of electronic ink has been around since 1999, but
the display itself has taken longer to evolve because the researchers
chose to make it out of plastic. Because plastic cannot tolerate the high
temperatures of silicon photolithography techniques, different processing
and manufacturing techniques had to be employed, said John A. Rogers,
director of Condensed Matter Physics Research at Bell Laboratories at
The most common displays are the cathode ray tubes (CRT) found in boxy
TV and computer monitors, and the liquid crystal displays (LCD) found
in cell phones, wrist watches, laptops and personal digital assistants
While silicon circuits
are made using photolithography,
the gold film used for the electronic paper circuits is patterned using
microcontact printing, an ultrahigh resolution form of rubber stamping,
which is fast, continuous and efficient, according to Rogers. It is also
cheaper than photolithography, he said.
“From a scientific standpoint there’s nothing particularly new” about
the approach, said Vivek Subramanian, assistant professor of electronic
engineering and computer science at University of California at Berkeley.
“But what is interesting is how they’ve brought everything together, including
E Ink’s system, to try to make a full system,” he said.
Two layers of plastic make up the display. One layer provides the optical
contrast and the second layer houses the circuitry that controls images.
Microcapsules of ink -- each one containing chips of white particles suspended
in a black dye -- are sandwiched between the layers. The white particles
congregate at the front or the back end of the microcapsule depending
on the electric field generated by transistors in the plastic circuits.
Each transistor acts “as a voltage controlled switch [that] controls the
color of the electronic ink pixels,” said Rogers. “When the particles
are at the front of the display, the pixel appears white; when they are
at the back, the pixel takes on the color of the dyed fluid in which the
pigments are suspended -- black in this case,” said Rogers.
The black-on-white display can be made any size. The current model measures
6 square inches, is just under a millimeter thick, and weighs about five
grams, or one tenth the weight of a thin film transistor (TFT) LCD of
the same size, said Rogers. “For a backlit [liquid crystal] display with
6- by 6-inch viewing area, the power consumption is about seven watts,”
he said. Electronic paper consumes about one thousandth as much power
because it does not require backlighting and because the system is bistable,
meaning no power is needed to display a pixel’s color, only to switch
it, according to Rogers.
It is, however, low resolution, containing just 256 pixels compared to
about 1.3 million in a standard 17-inch LCD.
In addition, although the transistors allow a switching speed of about
2.5 milliseconds, the total time for an image to change smoothly is about
one second; typical LCD’s pixels are refreshed 70 times a second. “Currently
the electronic ink, and not the transistors, limit the speed,” Rogers
said. “The first applications of this technology might not require high
speed operation,” he added. Devices such as PDAs and cell phones could
work well even if refresh rates are as low as half a second, he said.
The electronic paper could also be used in everyday paper products such
as newspapers, magazines and books. “An electronic newspaper…will consist
of only one or a small number of sheets of electronic paper, onto which
daily, or hourly, information content will be downloaded via a wireless
connection to the Internet,” said Rogers. By the same token, cereal boxes,
wall paper, and flyers could eventually be made from electronic paper.
“I don’t know if it will change electronic displays a whole lot because
the pixels are too slow,” said Subramanian. Meanwhile, we continue to
demand more from our electronics, he said. “I'd be surprised if they could
do PDA displays without substantially improving their refresh rates. You
need a refresh rate of about [17 milliseconds] to prevent flicker,” Subramanian
said. “However, it would probably be adequate as a note-taking device
or electronic book, since…the pixels hold their state once addressed,”
Electronic paper displays could be in use within five years, Rogers said.
The researchers are currently working on developing new transistor geometries
and semiconductors that will improve the switching time. They also aim
to speed up the refresh rate and to use the technology in non-display
applications such as radio frequency ID tags that can replace bar codes,
Full motion video could also be possible with newer inks that change color
more rapidly. “I think that this … will be possible within one to two
years. The circuit part is, more or less, done already,” he said.
The printing methods for the circuits and the use of organic semiconductors
make this research important, said Sigurd Wagner, a professor of electrical
engineering at Princeton University.
Rogers’ colleagues were Zhenan Bao, Kirk Baldwin, Brian Crone, Anant Dodabalapur,
Howard Katz, Valerie Kuck, and V.K. Raju at Bell Labs, and Karl Amundson,
Jay Ewing, and Paul Drzaic at E Ink, Corporation. They published their
findings in the proceedings of the National Academy of Sciences, April
24, 2001. The research was internally funded by Lucent Technologies and
E Ink, Corporation.
Timeline: 3 to 5 years
TRN Categories: Human-Computer Interaction; Integrated
Circuits; Materials Science and Engineering
Story Type: News
Related Elements: Technical paper, "Paper-like electronic
displays: Large-area rubber-stamped plastic sheets of electronics and
microencapsulated electrophorectic inks," proceedings of the National
Academy of Sciences, April 24,2001.
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