By David Cameron January 22, 2002
Researchers at Cambridge, MA-based E Ink
have completed the first working prototype of
an electronic ink display attached to a flexible,
silicon-based thin-film transistor backplane, the
sheet of electronics that controls display
pixels. The prototype is a functional display that
you can twist, bend or throw against the wall
without disturbing a single electron.
This proof-of-concept prototype confirms that it will soon be possible to
mass-produce reams of self-erasing electronic paper that combine
sheets of electronic ink with flexible silicon circuitry. Last year, Lucent
Technologies demonstrated an electronic-ink display driven by flexible
plastic transistors, but E Ink researchers believe that silicon-based
transistors have several big advantages over plastic.
The company's ultimate goal is to produce RadioPaper, sheets of
reusable e-paper containing radio frequency ID tags that download a new
edition of, for example, the Wall Street Journal each morning into the
same physical display.
On Display
Electronic ink is composed of tiny, translucent microcapsules no wider
than a human hair. Each capsule contains millions of particles, each of
which has either a positive or negative charge. The positive particles are
black and the negative ones white, and the type of electrical charge
applied to the microcapsule determines which particles will rise to its
surface and therefore which color will appear. The "ink"--a sheet of these
microcapsules--is integrated into a display, where the final product
presents an image that mimics the printed page: it's easy on the eye and
can even be read outside on the beach--and at an angle.
Until now, electronic ink has been used with standard, rigid backplanes
designed for liquid crystal displays. But after several years of research, E
Ink is now able to fabricate pliable, non-crystalline silicon transistors on
both stainless steel foil and plastic substrates, creating flexible
backplanes. Laying a sheet of electronic ink over these backplanes
creates the all-flexible prototype display.
"We have demonstrated the feasibility of a fully flexible electronic
paper-like display. We've proven that it works," says Michael McCreary, E
Ink's vice president of research and development. The company has also
developed a prototype similar to Lucent's, using plastic transistors on a
flexible backplane. However, according to McCreary, plastic transistors
have a shelf life of just a few months‹a technical obstacle which, in
addition to plastic's slow switching speed, currently stalls further
development.
Stretching into the Future
The completion of E Ink's prototype is "a significant milestone" for the
company, says Pat Dunn, director of technology at DisplaySearch, an
Austin, TX-based research and consulting firm. "This will bring their
technology closer to that paper-like feel. It evens the playing field for them
in terms of screen resolution, which is a very important criteria."
To reach its next milestone, E Ink will have to keep up with a number of
other players in the flexible display field. Palo Alto, CA-based Gyricon
Media is their only direct e-paper competitor, but other companies such as
Menlo Park, CA-based Rolltronics, Morgan Hill, CA-based Alien
Technologies and Cambridge, England-based Plastic Logic are all
developing novel production techniques for fabricating transistors on
flexible substrates.
Researchers at E Ink don't know exactly when their prototype will go into
full production, but they estimate that by sometime in 2005 they'll be
building fully-flexible displays for commercial use. For now, the company
is working with Philips Electronics to produce displays using electronic ink
against rigid, glass backplanes, to be built into mobile, handheld devices
starting next year.
David Cameron is a staff editor for technologyreview.com
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