E-Paper
An e-paper (electrophoretic) display moves charged pigment particles between two substrates using an electric field. Once the particles settle, they stay there with no power applied — the image is held indefinitely. Only a refresh cycle (applying a voltage sequence) moves the particles to display a new image.
Microcapsules containing white titanium-dioxide particles and black carbon particles suspended in oil are sandwiched between electrodes. A positive voltage on a pixel electrode pushes black particles toward the viewer (dark pixel); reversed polarity pulls white particles to the front (light pixel). Partial addressing allows greyscale in multiple voltage steps.
In plain terms
An Etch-a-Sketch powered by physics: charged black and white particles arrange themselves under voltage and stay put when the voltage is removed, needing power only to change what's shown, not to hold it.
Why designers use it
- Display shelf-price labels in supermarkets with no ongoing power draw.
- Show e-reader text with zero battery drain between page turns.
- Build solar-powered IoT displays that update once a day with no charging infrastructure.
- Create signage that must hold its message during a power outage.
Best for
- E-readers
- Shelf labels
- Low-power signs
Key specifications
- Resolution: 200×200 – 1872×1404
- Refresh time: 0.3 s – 4 s (Full update)
- Colours: B/W, B/W/Red, 4-grayscale, ACeP 7-color
- Power (idle): 0 W (Bistable: needs no power to hold image)
- Operating temperature: 0 °C – +50 °C
When not to use it
- When the selected panel's refresh time, color capability or temperature range cannot meet the application.
- When illumination is required but the design provides neither adequate ambient light nor a suitable frontlight.
Common mistakes
- Using drive voltages, timing or waveform tables not specified for the exact panel and temperature.
- Assuming every panel supports the same partial-refresh sequence. Follow its controller and refresh instructions to manage ghosting.
Where you will find it
- A Kindle Paperwhite uses a 6-inch e-paper display from E Ink: the display draws zero current between page turns, and an entire novel's worth of reading can be done on a charge because the SoC and radio (not the screen) dominate power consumption — the exact opposite of an LCD where backlight dominates.
- A hospital medication drawer uses an e-paper label that an RFID writer updates when a nurse restocks it: the battery in the label lasts three years because the label only refreshes when a new drug lot is placed, and the tag is visible with no power source in the event of a ward power failure.
- A smart city's bus-stop display uses a large e-paper panel updated via 4G LTE every 5 minutes: the display runs on a small solar cell and a supercapacitor because the panel only draws power during the 2-second refresh cycle, holding the timetable image in between with zero watts.
A short history
In the electrophoretic e-paper technology described here, electrically charged pigment particles move inside a display layer to form an image. The image is bistable, so it can remain visible without continuously powering the display. Updating still needs energy, making this approach useful for content that changes occasionally, such as electronic shelf labels.
Good to know
- Holding an image without continued display-drive power is different from claiming the whole product consumes no power.
- The cited Pervasive Displays development kit includes temperature sensing and storage for waveforms and images, illustrating that the panel and controller must be designed together.