Brussels, 26 Sep 2003
Scientists in the Netherlands believe they have found a way to overcome the problems of low brightness and slow pixels in electronic paper (e-paper), a breakthrough that could lead to the development of wireless, animated newspapers and books.
Other prototype e-paper displays have been let down by disappointing levels of brightness, and pixels that cannot switch from one image to the next quickly enough to cope with video or animation.
These challenges led Robert Hayes and BJ Feenstra from the Philips research lab in Eindhoven to experiment with a technique called electro wetting, in which electricity is used to make a naturally water-repelling surface attract water.
Each of the team's pixels consists of a tiny chamber with a transparent water-repelling base above a bright white background. A small drop of black or coloured oil sits on this, which spreads across the base to give a black or coloured pixel, and the rest of the chamber is topped up with water.
When a voltage is applied to the base, however, the water in the chamber is attracted to it, quickly pushing the oil to one side and exposing the bright white background. 'Water is very polar, so if you make the surface polar then the two want to come into contact,' explains Mr Hayes. 'All of a sudden the water wants to wet it.'
The overall result is a high contrast display with pixels that can be switched in around ten milliseconds, equivalent to 100 new images per second. Furthermore, the high reflectivity and contrast of the electro wetting chambers gives a display that is around four times as bright as an ordinary LCD display, and twice as bright as rival e-paper technologies.
Effective colour displays are created by combining several sub pixels, each with a layer of different coloured oil, in a single chamber. The team claims that the display can reflect around 40 per cent of light in this way, 'a notable accomplishment' according to a spokesperson from a rival e-paper developer.