Smallest Light-Emitting Diode in the World LED Screen as Small as a Human Cell

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ETH Eidgenössische Technische Hochschule Zürich

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The period at the end of this sentence is tiny. Within it, the following ETH Zurich article could be housed 2,000 times, with each word razor-sharp— provided the right microscope is available. Now, extreme miniaturization has been achieved.

Miniaturization is the driving force of the semiconductor industry. The enormous performance increase of computers since the 1950s is largely based on the ability to fabricate ever smaller structures on silicon chips. Chemical engineers at ETH Zurich have now succeeded in reducing the size of organic light-emitting diodes (OLED), which are primarily used today in premium smartphones and TV screens, by several orders of magnitude.

Micro Screen With A Thousand Times Better Resolution

Light-emitting diodes are electronic chips made of semiconductor materials that convert electrical current into light. "The diameter of the smallest OLED pixels we have developed so far reaches the range of 100 nanometers. This makes them about 50 times smaller than the current state of the art," says Jiwoo Oh, a doctoral student in the Nanomaterial Engineering research group of ETH Professor Chih-Jen Shih.

Oh developed the process for fabricating the new nano-OLED together with Tommaso Marcato. "The maximum pixel density is thus around 2,500 times greater than before in a single step," adds Marcato, who works as a postdoc in Shih's group.

For comparison: The miniaturization pace of computer processors followed the so-called Moore's Law until the 2000s, which stated that the density of electronic elements doubled every two years.

Ceramic Membrane Makes the Difference

In the fabrication of OLEDs, the light-emitting molecules have so far been deposited onto silicon chips afterward. This is done using relatively thick metal masks, which create correspondingly larger pixels.

The boost in miniaturization is now made possible by a special ceramic material, as Oh explains: "Silicon nitride can form very thin yet robust membranes that do not sag on areas in the square millimeter range."

This allowed the researchers to create templates for placing the nano-OLED pixels that are around 3,000 times thinner. "Our method also has the advantage that it can be directly integrated into standard lithography processes for computer chip production," emphasizes Oh.

Application for Screens, Microscopes, And Sensors

The miniaturized OLEDs open up new application areas. Pixels in the range of 100 to 200 nanometers provide the foundation for ultra-high-definition displays that could, for example, show razor-sharp images in glasses worn close to the eyes. To illustrate this, the researchers created the ETH Zurich logo using 2,800 nano-OLEDs. It is about the size of a human cell, with each of its pixels measuring around 200 nanometers. The smallest pixels developed by the ETH researchers even reach the 100-nanometer range.

The tiny light sources could assist in focusing into the sub-micrometer range using high-resolution microscopes. "A nano-pixel array as a light source could illuminate the smallest areas of a sample—the individual images could then be combined into an extremely detailed picture in the computer," explains Shih. Furthermore, the professor of technical chemistry also envisions nano-pixels potentially as tiny sensors, for example, to detect signals from individual nerve cells.

Nano Pixels Create Optical Wave Effects

The small dimensions also open up entirely new possibilities for research and technology, as Marcato emphasizes: "When two light waves of the same color come closer together than half their wavelength—the so-called diffraction limit—they no longer oscillate independently but begin to interact with each other." For visible light, this limit lies between approximately 200 and 400 nanometers, depending on the color—and the nano-OLEDs developed by the ETH researchers can be placed just as close together.

The basic principle of interacting waves can be illustrated by throwing two stones close to each other into a mirror-smooth lake. Where the circular water waves meet, a geometric pattern of wave crests and troughs is created. Similarly, cleverly arranged nano-OLEDs can generate optical wave effects, where the light from neighboring pixels either amplifies or cancels each other out.

Design Powerful Mini Lasers

Shih's team has already selectively manipulated the direction of emitted light in initial experiments using such interactions. Instead of radiating light in all directions above the chip, the OLEDs then emit their light only at very specific angles. "In the future, it will also be possible to focus the light of a nano-OLED matrix in one direction and use it to construct powerful mini lasers," anticipates Marcato.

Polarized light—that is, light that oscillates in only one plane—can also be generated through interactions, as the researchers have already demonstrated. This type of light is used today, for example, in medicine to distinguish healthy tissue from cancerous tissue.

An idea of the potential of these interactions can be drawn from modern radio and radar technologies. They use wavelengths ranging from millimeters to kilometers and have been utilizing interactions for some time. So-called phased-array configurations allow antennas or transmitter signals to be specifically directed and focused. In the optical spectrum, such technologies could help further accelerate information transmission in data networks and computers.

Basis for Meta-Pixels And New 3D Imaging?

The new nano light-emitting diodes were developed as part of a Consolidator Grant that Shih received in 2024 from the Swiss National Science Foundation (SNSF). The researchers are currently working on optimizing their method. Alongside further miniaturization of the pixels, the focus is also on their control.

"Our goal is to wire the OLEDs so that we can control them individually," Shih explains. This is necessary to fully exploit the potential of the interactions between the light pixels. Precisely controllable nano-pixels could, among other things, open the door to new applications of phased-array optics, enabling electronic steering and focusing of light waves.

In the 1990s, it was postulated that phased-array optics would enable holographic projections from two-dimensional screens. Shih is already thinking one step ahead: one day, groups of interacting OLEDs could be combined into meta-pixels and precisely positioned in space. "This approach could make it possible to create 3D images all around the viewers," the chemist envisions for the future.

Original publication: Marcato T, Oh J, Lin ZH, Tian T, Gogoi A, Shivarudraiah SB, Kumar S, Rajan AG, Zeng S, Shih CJ: Scalable nanopatterning of organic light-emitting diodes beyond the diffraction limit, Nature Photonics, October 31, 2025; DOI: 10.1038/s41566-025-01785-z

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