How do e-ink screens work?

E-ink screens are becoming more and more common. But how do they work and why are they better than other screens?
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How do e-ink screens work?
The FES Watch changes its design at the touch of a button thanks to electronic paper.
The FES Watch changes its design at the touch of a button thanks to electronic paper.Enlarge Enlarge

E-ink screens, or to give them their proper name electronic paper displays, are becoming more and more common. They’re used in eReaders like the Amazon Kindle, in smartwatches like the Sony FES (pictured right) and even in the Yotaphone 2 smartphone. But how do they work and why are they better than other screens?

SO WHAT’S E INK?

E Ink is a company that makes the key part of an electronic paper display. It creates the optical component of the screens, the bit that creates images. But the rest of the screen, like the bit you touch, could have been created by Amazon, Yota Devices or whoever else made the gadget.

SO HOW DOES IT WORK?

Electronic paper displays work by reflecting light, just like a sheet of paper. In normal LCD screens, a backlight shines through the pixels towards your eyes to show images. But in an electronic paper display, ambient light is reflected off the surface of the screen back towards your eyes, which means the screen looks brighter when there’s more light around. No more straining to read a screen while lying on the beach.

Most people who use an electronic paper display say that their eyes don’t get as tired reading from one compared to reading an LCD because it’s almost identical to paper.

Not having a backlight also has big benefits for battery life. The backlights used in traditional LCDs are responsible for about 40% of the screen’s power consumption. That’s why the battery life of the Yotaphone 2 can be so good despite having two screens.

So you can see why these are called paper displays, but what about the electronic bit? Well, that’s how the screen changes what’s on it.

The Yotaphone 2 has an ultra-efficient electronic paper display on its back.
The Yotaphone 2 has an ultra-efficient electronic paper display on its back.Enlarge Enlarge

The part of the screen built by E Ink is made up of millions of tiny capsules, about the width of a human hair. Each capsule has positively charged white particles and negatively charged black particles floating in a clear fluid. Your gadget can then move the particles around using electric fields, making each capsule look white or black.

The great thing about this is that the particles stay where they are until a new electric field is applied. That means you can cut the power to the screen but the image will keep showing. So when you’re reading a book on an electronic paper display, you only use power when you turn the page. It’s also how the Yotaphone 2 can show cool pictures all the time without draining your battery.

If you want to see a smartphone that makes the most of an electronic paper display, check out our review of the Yotaphone 2. Or if you’ve got any more questions about this cool tech, just ask us in the comments below.

What are your thoughts? Join the conversation here…

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