Color e-paper displays look to pigmented past

May 11th, 2009

One of the constant refrains in discussions of the various e-book readers now (or soon to be) on the market is the request for color. For a large population of users, the current greyscale screens that provide the extremely low-power displays for devices like the Kindle simply aren’t good enough, and there are some markets—science textbooks spring to mind—where color would really add value to the product. It’s not clear what technology will power the first generation of color devices, but researchers are looking to steal a page from traditional print media by making colored pigments part of the future of e-books.

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.

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