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Electrophoretic Ink (E Ink) is a proprietary technology developed by the E Ink Corporation that mimics the appearance of ink on paper. Because E Ink makes use of reflected light to show a page, it works well with an external light source, like a light bulb or direct sunlight. E Ink consumes minimal energy, so devices that implement it in their displays can run for weeks after a single full charge. E Ink is commonly used in e-readers.
E Ink technology makes use of tiny capsules called microcapsules, which contain a clear fluid as well as tinier black and white particles. When an electric field is applied to a microcapsule, the negatively charged black particles go one way, while the positively charged white particles go the other. Once the particles are in place, they lay suspended even when the electric field is removed. When the electric field is reversed, the particles exchange places. They stay suspended there on either side of each other even when the electric field is removed. This characteristic allows the microcapsule to use almost no energy while the particles are suspended. Because the microcapsules don’t consume much energy when they are in a suspended state, the page can save energy until the reader moves to a new page.
A vast collection of these microcapsules make up the entire surface of a typical E Ink-driven display. Because each microcapsule can be exposed to a different electric field direction or polarity, it is possible to come up with a combination of electric field directions to show correspondingly different combinations of black and white on the exposed side of the display. This is how text is produced.
Initially, E Ink technology could only show images and text in grayscale. Today, E Ink is able to produce color images and text by using color filters on top of the E Ink display.