Innovative materials boost stretchable digital displays’ performance

Organic light-emitting diodes (OLEDs) power the high-end screens of our digital world, from TVs and phones to laptops and game consoles. 

If those displays could stretch to cover any 3D or irregular surfaces, the doors would be open for technologies like wearable electronics, medical implants and humanoid robots that integrate better with or mimic the soft human body.

“Displays are the intuitive application, but a stretchable OLED can also be used as the light source for monitoring, detection and diagnosis devices for diabetes, cancers, heart conditions and other major health problems,” said Wei Liu, a former postdoctoral researcher in the lab of University of Chicago Pritzker School of Molecular Engineering (UChicago PME) Assoc. Prof. Sihong Wang.

Liu, now a professor at Soochow University, is the first author of a paper published today in Nature Materials that represents the next generation of OLED screens. 

Wang’s group at UChicago PME previously created a high-efficiency electroluminescent material that could stretch to more than twice its original length while still emitting a fluorescent pattern. But two layers—the cathode layer and the electron transport layer—had to remain rigid for the screen to work.

“Our ultimate goal is to realize a high-performance, fully stretchable, light-emitting device” said co-author Cheng Zhang, PhD’25, now a display engineer at Apple. “This paper targets the cathode layer and the electron transport layer, which were previously unsolved, major challenges for stretchable OLED screens.”

In the new work, an innovative aluminum gel and a novel family of conductive polymers overcame those two last rigid hurdles.

A new strategy turns reactive aluminum into stretchable cathodes 

Electrons flow into an OLED device through an electrode called the cathode, usually made of aluminum. Unfortunately, making stretchable aluminum is a formidable challenge.

After testing several disappointing alternatives and poring over the academic literature, the team had a counterintuitive breakthrough: To make aluminum stretchable, they had to make it brittle.

Metals that are liquid at room temperature are severely corrosive to most other types of metals. This is called “liquid-metal embrittlement,” a built-in flaw that engineers have been trained since undergrad to avoid. 

“If you place a droplet of this liquid metal onto aluminum foil, in just in a short amount of time, the aluminum foil will shatter into pieces,” Wang said. “This is seen as a negative thing because it causes damage. You try to prevent this from happening.”

Instead of preventing embrittlement, the UChicago PME team wanted to create it, protecting a thin film of aluminum in an elastic substrate.

“Then, when this embrittlement effect happens, although it breaks the aluminum into separate pieces, it won't leave it completely structurally destroyed,” Wang said.

The aluminum no longer shatters. It crackles. The cracks, tiny disconnection points, open up when the material is stretched and re-close when it’s straightened, like cut and folded paper. The surrounding liquid metal will flow into any larger disconnections, filling the void and keeping the overall device working.

The team made an alloy of gallium and indium, pre-mixing aluminum particles so it would bond better to the aluminum film. 

“Gallium-indium alloy is a liquid metal that can flow like water,” said co-author UChicago PME PhD student Zhiming Zhang. “Our aluminum liquid metal behaves more like a gel.”

During one month of aging tests, the electrical properties of the aluminum liquid metal remained unchanged.

Polymer family helps move electrons to the emissive layer 

For an OLED to shine brightly, electrons must travel smoothly from the cathode into the light-emitting layer. This journey requires a series of “energy steps” that line up just right—if any step is too high, electrons can get stuck, and the brightness drops. 

The electron transport layers lower these energy barriers and help electrons flow efficiently. To build a stretchable version of this important but brittle layer, the team designed a new family of polymers with a backbone of ring-shaped electron-deficient triazine-based conjugated groups linked together by alkyl chains. The rings are conductive; the chains, stretchy. 

“That creates a balance between the stretchability and the electron mobility,” Wang said. “Basically, the more alkyl chains you add, it will become more stretchable, but less conductive. The fewer chains you have, it's more conductive, but less stretchable.”

By changing the ratio of stretchy chains and conductive rings, the team was able to fine-tune an ideal ETL. Coupled with the new stretchable aluminum cathode, these two innovations form the next step in digital screens’ flexible future.

Moving forward, Wang and his team aspire to advance stretchable OLEDs into a commercially viable technology with performance on par with today’s rigid OLEDs, enabling their use across a wide range of smart, human-integrated electronics and humanoid systems.

Citation: “Enabling efficient electron injection in stretchable OLED,” Liu et al, Nature Materials, November 26, 2025. DOI: 10.1038/s41563-025-02419-z

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