Just like traditional paper can be made into everything from origami to paper-mâché, e-paper is proving to be a means on which incredible and all-round projects can be realized. E-paper’s amazing characteristics such as excellent visibility even with sunlight shining on it, paper-like readability and extremely low energy consumption make it perfect for all sorts of amazing products, from phones, accessories, shelf display, thermostats to digital signs.
But just what exactly is electronic paper and how does it work?
WHAT EXACTLY IS ELECTRONIC PAPER?
Electronic paper goes by many names: e-paper, sometimes spelled as ePaper, electronic ink and also e ink (the company that manufactures it). All of these names describe the same thing: a technology that mimics the appearance of normal ink on paper.
Simply put, imagine you take a pen and jotted down something in a notebook. The clear, well defined lines of your text will have the same crispness and high-readability as images shown on an electronic paper display.
But why is that, and how does an electronic paper display actually display an image? And what makes it so different from all the other high-definition screens out there?
MILLIONS OF TINY INK CAPSULES
To answer these questions we should start at the very core of e ink technology: small capsules filled with a clear fluid containing teeny-tiny particles, each about the width of a human hair.
Each electronic paper display is made up of millions of these capsules in a thin film, with the particles inside the capsules of different colors and different electric charges. Electrodes are placed above and below the capsule film. When a positive or negative electric field is applied to an individual electrode, the color particles with the corresponding charge will move either to the top or bottom of a capsule, making the surface of the e-paper display appear a certain color.
Capsules filled with negatively and positively charged particles color the surface of an EPD when an electric charge is applied.
In the most basic embodiment of an e-paper screen, the particles inside an e ink capsule will be either black or white. The white particles carry a positive charge and the black particles a negative one. If the electric charge applied is negative, then the negative black ink particles will be repelled to the top of the capsule and color the surface of the display black in that spot.
This is why an electronic paper display will sometimes also be called an electrophoretic display, or EPD for short: it simply means that it functions on the basis of the motion of dispersed particles in a fluid under the influence of an electric field.
TWO KEY POINTS THAT MAKE A WORLD OF DIFFERENCE
The way e ink works means that it differs from other displays in two key points: it is both bistable and reflective.
WHAT’S ON THE SCREEN IS HERE TO STAY
Just like the sketch in your notebook will remain there until you erase it, the content displayed on an EPD will hold a static image, even without electricity.
The way e ink works means that it differs from other displays in two key points:
An electronic paper screen reflects light from the environment so it doesn’t use its own but it can be applied and only consumes power when you change the content on the display.
This is possible because electronic paper technology is bistable, bistable is an electronic circuit which has two stable states. The tiny particles of an EPD will either be reflective or non-reflective (that is, black or white). In more advanced e-paper screens these bistable particles will also be provided in many levels of grayscale; energy is needed to put the color particles in their place, but once they are there, they stay there.
In practice this means that an EPD will be consuming power only when the content on it is changing – for example when you change the price of a product, or when the content of an e-paper parking sign changes from ‘Reserved’ to ‘Vacant’.
The rest of the time the display will simply show the image you want it to, with or without a power source and without having to constantly refresh the content shown (an LCD screen, for example, will have to refreshed about 30 times per second). This makes electronic paper extremely energy efficient, meaning that it can run for weeks on a single battery or even on alternative power sources.
