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Old 05-20-2009, 10:52 PM   #1
Gem began at the beginning.
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Join Date: May 2009
Device: Still not sure
ars technica: Color e-paper displays look to pigmented past

Interesting article talking about current demo technologies for color e-paper. Didn't find it in the news area so I figured I'de share.


One of these techniques was the subject of a recent publication in Nature Photonics, written by researchers at the University of Cincinnati and Sun Chemicals. Their technique, which they termed an electrofluidic display, relies on a combination of a small reservoir hooked up to a narrow space that sits above a reflective surface. Under normal circumstances, an aqueous solution will retract into the reservoir, driven by what's called Young-Laplace pressure. Creating a voltage difference across the narrow space, however, will create an electromechanical force that draws the liquid out from the reservoir and into the space. Simply put a pigment in the aqueous solution, and you've got a stable, voltage-switched color pixel.

The key feature of these devices is that the reservoir takes up only five to 10 percent of the dimensions of the pixel it can fill with its contents. Combined with the current reflective capabilities of the materials used in the device, this allows a contrast difference between the on and off states of about 55 percent, but the authors say that there's nothing in theory that should prevent improvements from reaching over 80 percent. Switching between on and off states can also be accomplished in a matter of milliseconds, and the authors suggest a number of optimizations, any of which could drop the refresh rates down to the point where video displays would be possible, provided the battery had the power to handle the frequent refreshes.

... (they go on to talk about theoretical optimizations)

If the above optimizations pan out, the authors claim that the resulting device "can hide the pigment or reveal the pigment with a visual brilliance that is similar to pigment printed on paper."

Meanwhile, researchers at Philips are looking at a system that would allow manufacturers to avoid using a composite pixel of this sort. In this device, a single reservoir holds two different pigments (the researchers are targeting a CMYK display) with different charge properties. By carefully manipulating the voltage on the device, different amounts of each pigment will flow out of the reservoir, providing careful control over the color of the pixel. Philips hasn't been very generous with the details on how that control is provided, however.


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