podcast transcript
For centuries, the printed page has been one of the most efficient ways to preserve and share information.
In the digital age, engineers have tried to reproduce the best paper quality without sacrificing the many benefits of screens.
The result is a technology that uses very little power, is readable even in bright sunlight, and can retain images even when the electricity is turned off.
Learn more about the history and technology of e-ink and electronic paper in this episode of Everything Everywhere Daily.
Before you begin, you should take notes on the terminology. The terms e-ink and e-paper are used interchangeably. However, while E Ink is a company and a trademark, electronic paper or e-paper is a broader category of display technology.
E Ink Holdings has become so dominant in the market that its brand name is often used generically, just as “Kleenex” is sometimes used for facial tissue.
To put e-paper in context, I’ll also briefly explain how the LCD displays used in most devices today work.
LCD, or liquid crystal displays, use a backlight that shines through a layer of liquid crystal. Each pixel contains red, green, and blue subpixels. Electrical signals change the arrangement of the liquid crystals, controlling the amount of light that passes through each color subpixel. By combining different amounts of red, green, and blue light, screens produce millions of colors.
There are other similar technologies and variations of LCDs, but for the purposes of this episode, they all have one thing in common: they actively emit light and require continuous power to produce an image. The screen turns off when the battery discharges or the power is turned off.
Researchers wondered whether it would be possible to create a display that had some of the best features of a screen, in that it could be updated and refreshed, yet still shared some of the best features of good old-fashioned paper.
The basic idea of electronic paper emerged from display research in the 1960s and 1970s, when cathode ray tubes (CRTs) were still the dominant form of display technology. Engineers were trying to create a screen that was thin, portable, readable under normal lighting, and could maintain an image without constantly consuming power.
One of the first important technologies in this field was developed at the Xerox Palo Alto Research Center, better known as Xerox PARC. In the 1970s, researcher Nicholas Sheridon created a system called Gyricon, a name derived from a Greek word related to rotation and image.
Gyricon consists of millions of tiny plastic spheres embedded in a flexible transparent sheet. Each sphere was black on one side and white on the other. The two sides carried different charges, either positive or negative. When an electric field is applied, the sphere rotates so that either the black or white side faces the observer.
The genius thing about this system is that once the sphere rotates, it stays in place without the need for any sustained force. In principle, a Gyricon sheet can display text or images, retain them indefinitely, and then rewrite them.
Sheridon built an initial prototype in 1975 and patented the twisted ball display concept in 1978. Xerox eventually created a subsidiary to commercialize Gyricon, specifically its reusable signs, but the company had trouble producing the displays cheaply enough. Xerox closed the subsidiary in 2005, but its work established many of the principles later associated with electronic paper.
The direct ancestor of modern E Ink was developed at the MIT Media Lab in the 1990s.
Physicist Joseph Jacobson imagined an e-book that could store many titles while retaining the physical properties of paper. Working with several MIT students, Jacobson’s group developed a new type of microencapsulated electrophoretic ink.
It may sound like a lot, but conceptually this technology is very simple to understand.
Instead of attempting to manufacture perfectly segmented black-and-white spheres, the researchers suspended electrically charged pigment particles in a fluid. They then placed the liquid into microscopic capsules.
Instead of half the sphere having a charge and a different color, the entire sphere had its own charge and color. As the charge changes, the sphere rises or falls in the microcapsule. The movement of fluid due to electric charge is called electrophoresis.
This innovation was important because microencapsulation makes electrophoretic displays more durable and easier to manufacture. Each capsule acts as a small, controlled container, preventing particles from spreading across the screen and reducing leakage and uneven movement.
The team published their findings in the journal Science. nature July 1998. This paper describes an electrophoretic ink that combines low power consumption, high reflectivity, wide viewing angles, and the ability to manufacture displays through printing and coating processes.
The research team established E Ink Corporation in 1997 to commercialize this technology. The company got its start at the MIT Media Lab, initially experimenting with billboards and other large displays before focusing on high-resolution panels for portable devices.
Modern black-and-white electrophoresis displays contain multiple layers.
The front has a transparent protective surface. Beneath it is an electrophoretic material made of millions of microscopic capsules, or tiny compartments. Behind this is an array of electrodes controlled by thin film transistors.
Each microscopic capsule contains a clear liquid and two types of pigment particles. In the typical arrangement, the white particles have one charge and the black particles have the opposite charge.
When a voltage is applied to the capsule, the electric field pulls one group of particles forward and pushes the other group back. When white particles move to the viewing surface, the area appears white. When black particles move to the surface, they appear black. Particle position, pulse sequence, and spatial dithering can be combined to create intermediate grayscale.
E Ink explains that the capsule is similar to the diameter of a human hair.
One of the characteristics of electrophoretic displays is bistability.
As mentioned earlier, traditional displays require power to maintain or illuminate an image. In e-ink displays, pigment particles tend to remain in their original positions even after the electric field is removed.
As a result, e-ink screens typically use most of their display-related power only when the image changes. Once a page, price, or symbol is drawn, it can remain on the screen for days, months, or longer without consuming power to keep the image displayed.
Electronic ink is only part of the display. A physical screen also requires a backplane that can control individual pixels.
Each pixel is connected to a thin film transistor. The transistor applies carefully timed positive and negative voltage pulses that move the pigment. These sequences are called waveforms.
Changing a pixel isn’t always as simple as applying a single voltage. Particles have inertia, interact with fluids, and can retain some memory of their previous positions. The controller may move through several intermediate states before deciding on the intended color.
E Ink’s first commercial demonstration included large signs rather than books. The first prototype signs, introduced in 1999, could be updated electronically, retaining information without the need for constant power. The company also collaborated with Lucent Technologies on a flexible display prototype around 2000.
The first widely recognized consumer e-reader to use E Ink technology was Sony’s LIBRIé, launched in Japan in 2004. This demonstrated that electrophoretic displays can support viable consumer devices.
The e-ink product that many of you are most familiar with is probably the Amazon Kindle.
Amazon launched the first Kindle on November 19, 2007. It combines an E Ink screen with wireless book purchasing and delivery.
Previous e-readers often required users to connect the device to a computer and transfer files manually. Kindle allowed readers to browse, purchase, and download books directly.
The Kindle did not invent electronic reading, nor was it the first e-reader. Its significance comes from integrating the screen, bookstore, wireless network, and publishing ecosystem into one product.
The Kindle’s success led to a significant increase in production of electrophoresis panels. Competitive products from Sony, Barnes & Noble, Kobo, PocketBook, and other manufacturers have expanded the market.
Here I would like to insert my personal experience with Kindle. Kindle came out about six months after I started traveling around the world.
When you travel, you have a lot of time to rest. I will always carry a book with me. The problem is that books are heavy, and finding English books in non-English speaking countries is often difficult and expensive. They were too heavy to put away, so I ended up carrying several books.
A few years later, I bought a Kindle, and it was literally a game changer. Now I have something lightweight that gives me access to the world’s largest bookstore at my fingertips.
The power of the Kindle was clearly demonstrated to me in 2014 when I boarded a ship from Cape Town to the island of St. Helena. I was on a ship and realized I had nothing to read for almost a month without internet access.
I rushed to the top deck of the ship, downloaded the entire Game of Thrones series over 3G in just a few minutes, and was ready to set sail.
Black and white e-ink displays have been appearing in stores recently because they allow prices to be displayed and updated automatically.
One of the biggest advancements in e-ink has been the development of color e-ink displays. One of the most widely used technologies is developed by eInk Corporation as Advanced Color ePaper (ACeP).
In multi-pigment systems, different colored particles exhibit distinct electrical properties. A carefully designed voltage sequence separates the desired pigments and places them on the viewing surface.
Full color systems can use cyan, magenta, yellow and white particles. A variety of colors can be reproduced by placing different combinations near the surface.
The colors aren’t as vivid or bright as a regular LCD monitor, but the quality is surprisingly good. There are now color eInk displays on the market that can be framed or hung on a poster-sized wall.
What’s great about this product is that it uses very little electricity and allows you to change the image whenever you want.
Another advantage of e-paper over LCD monitors is that it can be used even in full sunlight. If you’ve ever tried to view the screen on your smartphone on a sunny day, you’ve probably experienced the problem. It works better if there is no direct light on the screen.
E-paper doesn’t have a backlight, so it works well in sunlight. There are e-paper signs installed outdoors, which require a low-power solution that is easy to read even in sunlight.
One of the biggest weaknesses of e-paper is the screen refresh rate. On some first-generation devices, it took a noticeably long time for the screen to refresh with new content.
Some of the latest generations of e-paper screens have improved significantly. I saw a YouTube video of someone who hacked his e-paper to achieve a 60Hz refresh rate. This allowed him to get it to function as a reasonably good laptop monitor, albeit in black and white.
I can guarantee that there will probably never be a television made from e-paper. The image quality cannot compare to what a high-end LCD monitor can produce. In other words, there are e-paper smartphones on the market.
But that was never the purpose. E-paper offers a very clear niche market. Signs or devices that don’t need to be constantly refreshed are perfect candidates for e-paper screens.
If you’ve never seen them in the wild, you’ll likely see more of them in the coming years.
