Philips Research has developed a color e-paper technology that opens up new design opportunities for personalizing electronic devices.
This means that the color and appearance, of the device's surface, for example an MP3 player or mobile phone can be changed to match your outfit, mood or environment simply at the touch of a button. The technology has the potential to be used in the future for larger area 'e-wallpapers' where you can adjust the color of your wall or smart windows to regulate the daylight coming through your window.
Electronic paper (e-paper) looks like conventional paper and the bright wash of color it generates uses the ambient light for rendition, just like conventional paint, so no backlight is needed. Which means that the vividness of the color is maintained, even in bright outdoor conditions. Philips' technology allows different colors of ink to be built into one layer with each color controlled separately. This means the layer can be transparent, the same color as any one of the inks or even a mixture of multiple colors. Moreover, the saturation of each individual color can be controlled accurately - so any shade can be produced. Recently, Philips successfully realized a simplified, yet advanced version of its e-paper technology: e-skin. Since it is less complicated and less expensive to realize, it enables new applications. And because e-skin makes use of the ambient light, it is an inherently energy-efficient system, making it particularly suitable for application in portable devices as well.
"The first applications using the technology could be e-skins for small devices such as MP3 players or cell phones. However, the technology is highly scalable," says Kars-Michiel Lenssen, Principal Scientist at Philips Research. "In the future it will be possible to use e-skins to bring new color and a new aura or 'vibe' to much larger equipment. Just as Philips' Ambient Experience uses light and color to make hospital diagnostic rooms far more welcoming, a large e-skin could make the concept fit for the MRI or CT scanner itself, potentially putting patients more at ease."
In ambience creation applications reflective e-skins are the perfect complement to the emissive ambience-creation technologies that use LEDs and OLEDs to create colorful light. "You could use LEDs or OLEDs when you want a theatrical look and e-skins when you want something more subtle and more natural-looking that uses less energy," Lenssen proposes.
Philips' e-skin technology is based on its previous work with e-paper. Since the particles in suspension carry a surface charge, their motion can be controlled using an electric field - a phenomenon known as electrophoresis. If you create a pixel with colored particles in a clear suspension, applying an electric field perpendicular to the surface makes the particles migrate to the top of the pixel, turning it dark. This is the basis of monochrome e-paper used in e-book readers.
To go from monochrome to polychrome, Philips turned the electrophoresis idea on its head - or rather on its side and it can be referred to as 'in-plane electrophoresis'. Instead of applying the field perpendicular to the surface, they apply it parallel to the surface. This causes the colored particles to spread across the pixel, again turning it dark. When the pixel is reset, the colored particles 'hide' behind a mask, so the pixel is completely transparent. Furthermore, Philips has built a 'gate' electrode into each pixel, which provides control over how many colored particles spread across the pixel and hence the saturation or shade of each color.
Philips Research will present its work at the International Display Workshops 2009 in Japan, which is held from December 9-11. Although Philips' focus is mainly in the e-skin from ambient scene creation and product personalization, Philips is open to licensing its technology to other parties in other applications areas such as e-paper displays.