How Does E Ink Work on Your NOOK eReader?

By Corey Sandler

The concept behind E Ink, which creates the words on your NOOK screen (except for the NOOK Color), came out of the MIT Media Lab in Cambridge, Massachusetts, all the way back in 1997. The display consists of a thin film that contains millions of tiny microcapsules, each the diameter of a human hair. In the basic design, each microcapsule contains positively charged white particles and negatively charged black particles suspended in a clear fluid.

When a negative electric charge is applied, the white particles move to the top of the microcapsule, making the surface appear white at that location. At the same time, the black particles are pulled to the bottom of the microcapsules, where they are hidden. By reversing this process, the black particles appear at the top of the capsule, which now makes the surface appear dark at that location.

Put enough dots together and you can create a character or a number or a piece of an image. And then here’s the important part: once a dot has been formed, it stays there.

Metaphorically speaking: E Ink is the Etch A Sketch of the early 21st century.

Although the technology behind E Ink has almost nothing in common with Etch A Sketch, they do share two important attributes: Both can be used to convey a message, and both are non-volatile — once something has been drawn on the screen, that image will stay there without the a continuous flow of energy.

By comparison, an LCD requires electrical power to darken a spot on its screen plus more power to illuminate a backlight. And the image on an LCD is volatile: when the power is removed (or the battery runs out of juice) the screen goes blank.

The downside (to some users) of an E Ink display is that it takes a few fractions of a second to redraw a page. That’s no problem at all when it comes to flipping from one page of a book to another; there’s just a blink of black or white, not much different from turning a paper page in a printed book.

Bottom line: A NOOK E Ink eReader is more like a traditional book printed with black ink on white or near-white paper. It doesn’t glow from underneath the characters, the print won’t rub off on your fingers, and it can hold a thought for days, weeks, and months without fresh electrical power.

For more information about the NOOK eReader and its features, explore NOOK eReaders For Dummies, Portable Edition.