Is an E-Ink Display Right for Your Next Project?

2022-10-05 | By Maker.io Staff

Today, you can choose from a large variety of displays to employ in your projects. For example, classic seven-segment displays, and LCDs are a low-cost, beginner-friendly way of displaying data to the user, and more advanced TFT screens offer a way of displaying colorful graphics and animated media. However, e-ink displays are one type of screen often overlooked, even though they offer a few unique benefits we should be aware of.

This article investigates how e-ink displays function and summarizes a few key benefits and drawbacks of using these still relatively exotic displays in DIY projects.

What Makes E-Ink Displays Different from Others?

Most modern displays include a built-in backlight to offer users the best viewing experience. While this approach has many benefits (such as better readability in the dark, higher contrast, and brighter colors), the often-power-hungry backlight also means that mobile devices go through their battery faster than users might like. In addition, such emissive screens, as most backlit displays are referred to, don’t perform so well outdoors where it is bright. That is because the backlight is typically not powerful enough to outperform the sun on a bright day. The reflective glass surface common in modern handheld devices often exacerbates this problem, making it incredibly difficult to read the display outdoors.

Is an E-Ink Display Right for Your Next Project? E-Ink displays are very energy-efficient when displaying static content for prolonged periods, which makes them perfect for some battery-operated mobile devices, such as e-book readers.

In contrast, e-ink displays (also called electronic paper) use a reflective approach, similar to LCDs without a built-in backlight. Instead, such reflective screens rely on an external light source to make the contents of the screen visible. Instead of a backlight, e-ink displays have a reflective backing that allows light to bounce back from the inside of the display.

Internally, e-ink displays comprise an electronic ink layer that renders pixels - for example, text and graphics. The outside light passes through that ink layer before the reflective layer behind that ink layer sends the light back out to the viewer, making the contents on the screen visible.

Key Benefits of Using E-Ink Displays Over TFTs

By omitting the power-hungry backlight, e-ink displays offer prolonged battery life in mobile devices compared to a device that uses a regular backlit display. In addition, e-ink displays do not need any power to retain an image once it’s been drawn on the electronic ink layer. Therefore, electronic paper only uses energy when refreshing the screen (for example, when flipping pages in an ebook).

Omitting the backlight also has the added benefit of allowing manufacturers to reduce the thickness and weight of e-ink displays significantly. Therefore, electronic paper screens can be flexible, similar to some modern OLED displays. E-ink screens are typically more rugged than other displays, as they do not rely on a glass surface to protect the screen.

Is an E-Ink Display Right for Your Next Project? E-Ink displays can be incredibly thin and flexible, as they do not rely on a backlight. Image used courtesy of Adafruit.

As mentioned above, e-ink displays easily outperform other displays outdoors, as they rely on an external light source to make the contents on the screen readable. Finally, many people find looking at electronic paper over prolonged periods more comfortable than viewing backlit displays.

Drawbacks of E-Ink Displays

So far, it looks like electronic paper outperforms other displays in almost every aspect, so why don’t all mobile devices use e-ink displays? Unfortunately, e-ink displays are limited in terms of what they can display. The power-efficient reflective displays are mainly intended for applications that rarely refresh the screen, like e-book readers and clocks. That is because it can take quite a while to refresh the contents of an e-ink display, and they can’t offer the high refresh rates that modern OLED and TFT displays provide.

Next, e-ink displays offer a minimal number of colors, and most of them are only monochrome. However, you can get variants that display up to seven colors. Besides the limited color palette and low contrast, e-ink displays perform poorly in dark environments because of the lack of a backlight.

Summary

Don’t be afraid to investigate whether you could employ an e-ink display in your projects, as these screens offer a few unique benefits over other display technologies. Firstly, electronic paper performs exceptionally well outdoors and in applications that rarely redraw the contents on the screen. In addition, many people find looking at e-ink displays over prolonged periods more pleasant than looking at backlit displays. Finally, electronic paper is very energy efficient, as it only uses power when redrawing the screen. It can even retain data on the screen while entirely disconnected from a power source.

However, e-ink displays can only draw a minimal number of colors, and most displays are monochrome. In addition, it takes significantly longer to refresh the contents of an e-ink screen than other display technologies. Therefore, electronic paper is most suitable for displaying static content, such as text and simple graphics.