The encyclopedia · Engineering & Operations · Technical decision · 1998–2007
E Ink made a paper screen that holds an image with almost no power
E Ink microencapsulated charged pigment so a screen keeps a page up without power, giving e-readers their paper-like look and weeks of battery.
E Ink Corporation
the move
Almost every screen we use draws power continuously to hold an image, so a device has to keep the backlight and the pixels on. Researchers had long wanted an electronic analogue of paper — a cheap, flexible, reflective display — but the microparticle displays they had were short-lived and hard to make in volume.
In 1998 a team at the MIT Media Lab reported in Nature an 'electrophoretic ink': a dispersion of charged pigment sealed inside microscopic capsules. Applying a small d.c. field drifts the particles to one face of each capsule or the other, turning a pixel white or black, and the image stays because the material is bistable.
Because the display does not have to be driven to keep a static page, it draws power only when a pixel changes, and because it reflects rather than emits light it needs no backlight at all. The ink could even be printed, and it solved the lifetime problem that had killed earlier versions.
The result was a screen with an 'ink on paper' look that could sit on a shelf for weeks and still show the same page — a genuinely different power equation from a backlit LCD or OLED.
why it works
- Bistability means the material holds its own state, so no power is consumed just to keep a page visible.
- Reflecting ambient light removes the backlight, which is the largest battery drain in a normal screen.
- Microencapsulation made the fragile electrophoretic medium printable and reliable enough to manufacture.
- Pixels move only when content changes, so a static e-reader page costs almost no energy.
what transfers
The product is not the screen but the state-preserving material — save power in the physical layer instead of trying to optimize it in software.
what came after
E Ink Corporation was spun out of the MIT Media Lab in 1997 to commercialize the ink; in 2009 the Taiwanese panel maker Prime View acquired it and kept the E Ink name. The electrophoretic display became the screen behind Amazon's Kindle, letting e-readers run for weeks on a single charge, and later spread to smartwatches, e-signage and museum labels where a low-power, readable display matters.
references
spotted an error? The archive wants to know.