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Race for Color Video E-readers

December 21, 2009
The e-reader is a killer application involving printed electronics. Despite costing more than an i-Pod, the Amazon Kindle achieved 500,000 unit sales in its first year of trading last year and now we are talking of millions. The i-Pod, an iconic success, only achieved 300,000 unit sales in its first year of trading.
 
It is easy to predict that the next major advances in e-readers will be color and video — preferably together. After all, we now have gorgeous color and video on our mobile phones thanks to Active Matrix Organic Light Emitting Diode AMOLED displays.
 
What is more difficult to predict is the e-reader technologies that will achieve such things because e-readers are perused for a very long time as people access books and business reports. Power is best conserved by using a bistable display such as the e-Ink displays currently favoured for almost all of them.
 
These are superb in bright sunshine unlike the displays on most mobile phones and laptops. To get color, companies such as Fujitsu have experimented with filters over such electrophoretic displays but they give a washed out appearance. E-Ink is also working on white electrophoretic pixels colored by filters. By contrast, electrophoretic competitor SiPix may be working on color electrophoretic microcapsules. Electrophoretics are not light emitting either. Reading in dim or dark surroundings calls for some form of lighting.
 
Edwin Thomas has developed promising tunable photonic crystals at Massachusetts Institute of Technology and the University of Toronto has spun off a photonics company Opalux. Opalux P-Ink gives rapidly tunable crystals of high color intensity. However, that tuning is not yet fast enough for video. No need for traditional red, green and blue pixels -here each pixel tunes to the required color giving a much more coherent and appealing image compared to color LCDs. It is called "field sequential" color display. Man-made photonic crystals are biomimetic in imitating the periodic structures of opals and butterfly wings. To be more precise, if the particles are about 200 nanometers in diameter, they provide Bragg interference at visible wavelengths, the precise wavelength i.e. color being controlled by the spacing between particles.
 
Opalux achieves this by embedding silica beads in an electroactive polymer substrate so this is yet another use of electroactive polymers in printed and partly printed electronics beyond the electronic shutters, reprogrammable Braille and electronic texture changing we have mentioned elsewhere in Printed Electronics World. Basically, when an electronic field is applied, the polymer swells or contracts, changing the color.
 

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