At its core, an eReader is a tablet. It has a touchscreen, a graphical user interface (GUI), Wi-Fi, a processor and memory. However, unlike a standard tablet, eReaders present content via an electrophoretic display commonly known as E Ink. This unique screen technology, first introduced by Xerox in 1970, requires very little power and produces no light. As a result, it feels more like reading a printed page than a lighted screen.
The screen of an eReader is constructed of two or more conductive plates separated by a 10 to 100-micrometer gap. Between the plates is a layer of dark-colored oil; floating in that oil is a mass of titanium dioxide particles, each about 1 micrometer in diameter.
Positive and negative charges are applied across the plates to produce text and images. A positive charge brings negatively charged particles to the surface and vice versa. The particles drawn to the top plate appear white, and those drawn to the bottom plate appear black. The shapes created by these electrophoretic migrations appear on the screen as text and pictures.
By comparison, the image on an iPad is produced by millions of light-emitting diodes (LEDs). Each LED is given an electrical charge, which creates a brief flash of light. In aggregate, millions of flashes produce a continuous glow whose position and color are defined by onboard graphics software and hardware.
eReaders vs. tablets
What are the virtues of a good eReader? First, E Ink doesn’t produce any light. That reduces the eye strain many people experience when watching a screen for long periods. Also, E Ink creates sharp, easy-to-read text in bright rooms or in direct sunlight. An iPad screen, on the other hand, is much harder to see in broad daylight.
Speaking of eye strain, LED screens bombard your eyes with potentially harmful blue light. Studies show this can lead to a variety of issues, from simple fatigue to far more severe macular degeneration.
eReaders also boast an incredibly long battery life—up to 6 weeks on a single charge. Thanks to its limited functionality, an Amazon Kindle doesn’t need the latest power-hungry M3 or Snapdragon processor, nor does it require much RAM or a high-performance GPU. In fact, an E Ink screen only requires power to change states. When a new page is loaded, the “ink” stays on the screen without the device’s help.