Video‐rate tunable colour electronic paper with human resolution
Article Date: 22 October 2025
Article URL: https://www.nature.com/articles/s41586-025-09642-3
Article Image: Figure 1
Summary
This Nature paper introduces “retina E-paper”: a reflective, ultra‑high‑resolution electrochromic display built from WO3 nanodisk metapixels on a reflective Al/Pt substrate. The team demonstrates pixel sizes down to ~400–560 nm (yielding >25,000 PPI) and video‑rate switching by using a 500 nm lateral electrode gap and short voltage pulses. The devices combine structural (Mie and grating) colour generation with electrochemical tuning of WO3 to switch pixels between colourful (insulator) and dark (metallic) states.
The authors show full‑colour and CMY demonstrations (including an anaglyph 3D butterfly and a tiny reproduction of Klimt’s The Kiss), measure ~80% normalised reflectance with ~50% optical contrast, and report rapid switching (95% contrast in 40 ms) and low average power use (≈1.7 mW cm–2 for video, ≈0.5 mW cm–2 static) thanks to WO3’s colour memory effect.
Key Points
- Retina E‑paper reaches >25,000 PPI (pixel ≈ 560 nm) — approaching and exceeding the human retinal resolving benchmark used for ultimate VR displays.
- Colour is generated by patterned WO3 nanodisks (metapixels) via Mie scattering and grating modes; geometry (diameter, spacing, thickness) tunes RGB/CMY responses.
- Electrochromic WO3 switches between dielectric (colour) and metallic (dark) states through ion insertion (MxWO3), changing refractive index and absorption for reflectance modulation.
- Fast switching achieved by a lateral electrode design with a 500 nm gap and short pulses — 95% optical contrast in 40 ms (video‑rate, >25 Hz) and effective average 5 ms switching for typical video updates.
- High reflectance (~80%) and ~50% optical contrast are maintained even at sub‑micrometre pixels; reflective design avoids brightness loss seen in tiny emissive pixels.
- Colour memory (bistability) keeps pixels stable without constant power — greatly reduced energy for static or slowly changing content.
- Practical challenges remain: narrower colour gamut versus emissive displays, device lifetime, operating voltage/electrolytes, and the need for ultra‑fine TFT addressing for large‑area independent control.
Why should I read this?
Want retina‑level resolution without a huge power bill? This paper is basically a proof that tiny, reflective electrochromic pixels can be made to switch fast enough for video, keep their colours without constant power and pack resolutions that make smartphone screens look huge. If you care about AR/VR optics, low‑power displays or the next leap in microdisplays, skim this — then dive in if you like clever nanofabrication and electrochemistry.
Author note
Punchy take: this is a big step toward truly immersive, low‑power microdisplays. The team demonstrates credible video‑rate electrochromic pixels at human‑resolution scales — impressive engineering and a clear roadmap of what still needs work (gamut, drive electronics, longevity). For researchers and product teams in AR/VR or display materials, the methods and device metrics are worth a close read.