AT LAST, the world鈥檚 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. 鈥淚t鈥檚 moderately portable, but you certainly can鈥檛 put it in your pocket,鈥� 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. 鈥淚 think the new display is a great idea,鈥� Chang says.
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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鈥� 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.
鈥淭he device could go beyond Braille and recreate whole scenes, allowing people to feel images as well鈥�
The devices could also go beyond Braille and recreate whole scenes on their surface, allowing the blind to feel images as well as words. 鈥淭he idea is to create an array of tiny pixels,鈥� says Yoseph Bar-Cohen, an expert in Electro-active polymers at NASA鈥檚 Jet Propulsion Laboratory in Pasadena, California.
But he is concerned the force of the paddles in Someya鈥檚 device may be too weak. 鈥淚f a blind person cannot feel the movement of the dots, the device will not be practical.鈥�
