Look a little closer
An e-reader can keep a page visible without continuously producing light. Electronic ink uses electric fields to move pigment particles within tiny capsules, then lets them remain in position as a reflective display.
A classic black-and-white capsule contains clear fluid and black and white particles carrying different charges. Each capsule is roughly hair-sized, and millions cover a display film.
Voltage at electrodes below the screen pulls one pigment upward and pushes the other down. The particles at the top reflect ambient light, making that region look black or white. Like ink on paper, it relies on outside illumination rather than constant emission.
Bistability means the particles do not immediately return when the field disappears. Updating a page consumes energy, but preserving the same image requires almost none for the display itself.
A refresh may briefly flash black and white while voltage pulses place particles accurately. Switching is slower than on common LCDs and less suited to fast video, but sunlight readability and long battery life are major advantages.
Color e-paper may add filters or move several colored pigments independently. Designs differ, yet low power comes from changing physical particle arrangements only when needed and retaining them until the next update.
