Electronic ink is the technology used in all e-book displays: it imitates the appearance of ink on a sheet of paper by exploiting sunlight
Electronic ink is a special technology invented in 1996 by Joe Jacobson that imitates the appearance of "real" ink on a sheet of paper. Electronic paper has been very successful and is used by all e-book manufacturers: it does not need much electricity to work and ensures a high autonomy.
In contrast to classic LCD screens that are backlit, e-ink technology reflects sunlight, as if it were a normal sheet of paper. This feature, not only saves a lot of battery, but also does not strain your eyes. In fact, e-ink displays produce a minimal amount of blue light, the one that usually creates the most problems for people. E-paper has a very simple operation to which it owes much of its success.
How e-ink technology works
Displays made using e-paper are not like LCD screens that use a back light to illuminate pixels and show images to the human eye. E-ink technology uses a physical process called electrophoresis. Basically, e-paper is made up of two thin layers of transparent paper, divided only by 0.3-millimeter-sized spheres. These capsules are electrically charged: one hemisphere is positively charged and is black in color, while the other half is negatively charged and is white in color. Depending on the electrical impulse that reaches the screen, the human eye is shown the black half or the white half. By placing all the spheres in the right position, the words of the book are formed: each time you change the page, the capsules change position and adapt to the input from the user.
Thanks to the special characteristics of electronic ink, it is not necessary to continuously power the screen: just provide energy when it is necessary to change the electrical charge of the spheres. This saves energy and the battery can last even more than a month. Some companies, instead of expressing autonomy in hours or days, use the amount of pages you can "turn" as a metric.
Damaging to the eyes?
Compared to normal screens mounted on smartphones and tablets, electronic paper is less harmful to people's eyes. Even after intensive use of an e-book, you will hardly suffer from eye strain.