06-04-2010
Pyramid take top spot |
 |
Following a great achievement last year where we gained the runner-up prize for the TARGETjobs 'The... |
|
 |
|
Electronic paper anyone? |
|
A curious combination of coloured oil and water may be the key to creating flexible sheets of 'electronic paper' that can display fast-changing, full-colour video images.
A simple yet ingenious idea may finally make 'electronic paper' a realistic prospect. If so, you could one day peruse an animated version of your daily newspaper on a flexible wireless display that unfurls like a roller-blind.
Until now, attempts to make e-paper have been dogged by sluggish pixels - the paper can't switch images fast enough to display video or animations. And the brightness of images has been disappointing, especially for colour. But now Robert Hayes and BJ Feenstra at Philips Research Laboratories in Eindhoven, the Netherlands, have unveiled an idea that they say overcomes both problems at a stroke.
Their new display is based on a phenomenon called electrowetting, in which applying a voltage to a normally water-repellent surface makes it attract water. Each pixel consists of a tiny chamber with a transparent water-repelling base, sitting atop a bright white substrate. A minuscule drop of a black or coloured oil is placed in the bottom and then the well is topped up with water. The oil spreads out and covers the base, obscuring the white background and creating a black or monochrome pixel.
But when a voltage is applied to an electrode beneath the water-repellent base, the water quickly wets it and pushes the oil to one side. "Water is very polar, so if you make the surface polar then the two want to come into contact," explains Hayes. "All of a sudden the water wants to wet it." This exposes the white background, creating a white pixel. The result is a high-contrast display that can be turned on and off at video speeds.
Other e-paper technologies have used pixels containing small particles suspended in liquid. One, developed by Xerox offshoot Gyricon, uses tiny spheres that are white on one side and black on the other, and can be flipped to create different monochrome images. Meanwhile E-Ink, a spin-off from the Massachusetts Institute of Technology, has used pixels containing negatively charged black particles and positively charged white ones. Electric fields control which colour of particle appears at the surface of the pixel. But neither technique can manipulate the pixels fast enough to cope with video images.
With electrowetting, however, pixels can switch states in around 10 milliseconds - fast enough to generate 100 new images a second. TV-quality video only requires 25 images per second. And the high reflectivity and contrast of the wetting displays make them much clearer: colour ones are four times as bright as liquid crystal displays (LCDs) and twice as bright as rival e-paper technologies.
To make a multicolour display, each pixel comprises three sub-pixels. Each of these contains two different primary-coloured oils, one covering a water-repelling surface at the top of the chamber, the second covering another at the bottom. On top of each sub-pixel is a filter for the third primary colour.
When both the oils are lying flat, they and the filter absorb the full spectrum, making the sub-pixel appear black. But when both oils in a cell are pushed to one side, the sub-pixel takes on the colour of the fixed filter on top. When the three sub-pixels are made to reflect red, green and blue light, the overall effect will be a white pixel.
The Philips team claims that the display reflects around 40 per cent of light - a "notable accomplishment", concedes an E-Ink spokesman. He adds that their switching rates are not fast enough yet for video, but says that "research prototypes are dramatically faster".
Philips predicts many other applications for its technology. In addition to flexible displays for a new generation of laptop PCs, tablet PCs and PDAs, they believe the flexibility of the simple water-filled cells may even lend itself to use in textiles. They suggest people may be able to wear garments into which the latest fashionable designs or animations have been downloaded. Anyone for a video vest? |
|
|
