A new display technology could make electronic paper look more like the real thing. Conventional ink on paper has a much higher brightness and black-and-white color contrast than electronic paper. The new display, made by researchers at the University of Cincinnati, in Ohio, is designed to match the brilliance and contrast of paper. "We've demonstrated a technology where you have the brightness of paper, and color has the same saturation that you expect from printed media," says electrical- and computer-engineering professor Jason Heikenfeld, who led the work, which was published in Nature Photonics.

The pixels also switch between black and white within one millisecond, making the technology suitable for video (LCDs currently switch in a few milliseconds). A slower refresh speed of tens to hundreds of milliseconds is one of the main issues plaguing current e-paper.

The researchers use aluminum layers that reflect light and carbon black ink for a deep black color. First, a polymer layer is patterned with wells that contain the black ink. An aluminum film is deposited on the polymer and topped with an indium tin oxide (ITO) transparent electrode layer. A voltage applied across the aluminum and the ITO electrode pulls the ink out of the well and spreads it over the entire pixel area.

The pixels are as small as 100 micrometers wide, giving the display a resolution of 300 dots per inch. This is higher than many e-readers on the market, Heikenfeld says. Putting red, green, and blue color filters on top of each pixel would create color displays.

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