Pocket Braille for people on the move
* 15 October 2005
* NewScientist.com news service
* Celeste Biever
Web Links
* National Federation for the Blind <http://www.nfb.org/>
* Takao Someya, University of Tokyo
<http://www.ntech.t.u-tokyo.ac.jp/index.en.htm>
* International Electron Devices <http://www.his.com/%7Eiedm/>
AT LAST, the world's first portable electronic Braille display. It is
small enough to fit in a pocket and can even be rolled up like a newspaper.
The display consists of a sheet of tiny plastic paddles that bend in
response to a voltage. It is designed to connect to a cellphone or
laptop, and could also replace the liquid crystal screen of an ordinary PDA.
Existing dynamic displays for blind people use an array of pins that pop
up when stimulated by piezoelectric actuators. But the smallest versions
are the size of a phone book and weigh about 500 grams, mainly because
of the rigid fibreglass board the actuators are mounted on. "It's
moderately portable, but you certainly can't put it in your pocket,"
says Curtis Chang of the National Federation for the Blind in Des
Moines, Iowa. At $3800 each, they are also too expensive for most
people. "I think the new display is a great idea," Chang says.
It will almost certainly be cheaper. Created by Takao Someya and his
team at the University of Tokyo, the display is made entirely of a
flexible polymer and thin metal films. These layers can be printed using
low-cost deposition techniques, making a price tag of as little as $100
a distinct possibility, says Someya.
The 16-centimetre-square prototype is just 1 millimetre thick and weighs
5 grams. A grid of organic transistors sits on a polymer membrane, with
144 plastic paddles on top. The entire device is coated with thin rubber.
The paddles are made of a negatively charged polymer seeded with
positively charged lithium ions and sandwiched between two metal
electrodes (see Diagram). When a voltage is applied across the
electrodes, the lithium ions migrate to the negative electrode on the
lower side of the paddle. The result is a crowd of ions at the bottom,
which expands the polymer and makes it bend upwards. On the tip of each
paddle is a sphere under a millimetre across, which rises when the
paddle bends, causing a bump in the rubber surface. When the current is
switched off, the ions disperse back into the polymer, the paddle
straightens and the bump disappears.
The paddles take just under a second to move up or down, which is
acceptable for reading a book or a short message, but not for someone
working, says Chang. To make them move faster the transistors need to be
made smaller, so the electrons have less distance to travel between the
transistors' on and off state. This might be possible using
nanofabrication techniques, says Someya.
Someya will present the device at the International Electron Devices
meeting in Washington DC in December.
“The device could go beyond Braille and recreate whole scenes, allowing
people to feel images as well”
The devices could also go beyond Braille and recreate whole scenes on
their surface, allowing the blind to feel images as well as words. "The
idea is to create an array of tiny pixels," says Yoseph Bar-Cohen, an
expert in Electro-active polymers at NASA's Jet Propulsion Laboratory in
Pasadena, California.
But he is concerned the force of the paddles in Someya's device may be
too weak. "If a blind person cannot feel the movement of the dots, the
device will not be practical."
From issue 2521 of New Scientist magazine, 15 October 2005, page 28
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