In a world dominated by glowing LCDs and OLED displays, there’s a quiet contender that works differently: electronic paper or eink. If you’ve ever used an ebook reader or seen a digital price tag in a store, you’ve experienced the magic of epaper technology. Its appeal lies in being readable like real paper, consuming ultra-low power, and remaining visible even under direct sunlight. But how does it actually work?

What is epaper?

Epaper is a display technology that mimics the appearance of ink on regular paper. Unlike backlit screens, which do always emit light, epaper reflects ambient light, just like a physical - printed -  book. The most popular form of epaper is an electrophoretic display (EPD), commonly branded as eink.

The science behind eink / epaper

At its heart, epaper uses microcapsules filled with electrically charged black and white particles suspended in a clear fluid. Here’s how it works:

1. Charged Particles:
   
   
• Black particles carry a negative charge.
  
  
• White particles carry a positive charge.
  
  
  
  
2. Electric Fields in Action:
   When a voltage is applied, the electric field moves the particles:
   
   
• White particles move to the top (visible to the reader).
  
  
• Black particles move to the bottom (hidden).
  
  
3. Stable - and readable - without power:
   Once the particles settle into position, they stay put without additional energy (so even when power is disconnected). This is why your ereader can display a static page for days, without draining the battery.
   
   

Why is epaper so power efficient?

Unlike LCDs or OLEDs, which displays continuously refresh pixels and emit light, epaper only uses power when changing content. For example:

• Turning a page on an ereader consumes only a small burst of energy.
  
  
• Keeping the page displayed requires virtually zero power.
  
  

This makes epaper ideal for devices that don’t need constant animation - like e-readers, digital shelf labels, and digital signage.

Strengths of epaper

Epaper has several strengths that make it an attractive display technology. One of its key advantages is sunlight readability, as it has no glare and reflects natural light just like paper. It also offers exceptional battery life, with devices often able to run for weeks or even months on a single charge. In addition, epaper is easier on the eyes, reducing strain compared to glowing screens.

Limitations of epaper

Epaper also comes with certain limitations. Its slow refresh rate makes it unsuitable for video playback or fast animations. Whilst eink is as readable as normal paper in similar light conditions, it might require a front-light or another external light source to be read comfortably in the dark (like when used for realtime passenger information).

The future of epaper

The future of epaper is expanding into exciting new areas as researchers continue to develop the technology. Advances in color epaper are making it possible to deliver richer reading experiences and more dynamic signage. Flexible epaper is also being explored, opening the door to innovative new form factors. In addition, sustainable epaper retail labels are being developed to help reduce waste from traditional printed signage.

Epaper is proof that sometimes less is more. By focusing on efficiency and readability rather than animations, it has created markets where it excels. Whether in your ereader, a smart watch, or the price tags at your local supermarket, epaper shows how clever physics can make digital displays feel almost magical. And how about outdoor advertising, use of large sizes of color eink displays now makes this possible as well.