How does electronic paper work?

Electronic paper, also known as e-paper or Electronic Paper Display (EPD) is a display which imitates the appearance of ordinary paper. Electronic paper is portable and reusable – it can be refreshed (electronically) and written upon millions of times.

Many different technologies are used for making e-paper. The most commonly used e-paper consists of millions of tiny plastic capsules which are sandwiched between two sheets of flexible plastic. Each capsule, which is as narrow as a human hair, contains several positively charged white beads and negatively charged black beads floating in a clear fluid.

When an electric voltage is applied to each of the capsules through the circuitry embedded underneath, the beads, due to their unlike charges, get separated and move to the opposite faces of the capsule. When white beads are on top, the upper face of the capsule appears white, thus making the display appear white at the point where the capsule is located. Similarly, when black beads are on top, the display appears black at the point. Thus, each capsule functions as a separate pixel allowing the black text or picture to be visible on the display.