(Nanowerk Spotlight) Electronic displays surround us in rigid forms – from phone screens to televisions – but creating displays that can stretch and conform while maintaining brightness and functionality has remained an unsolved challenge. Standard display materials crack under strain, and previous flexible alternatives suffered from either dim output or limited stretchability. The few displays that could stretch typically lost significant brightness when deformed. Adding sound generation capabilities to these displays introduced even more technical barriers, as traditional speakers require rigid components to produce clear audio.
A team of materials scientists from Korea University of Technology and Education and the University of California San Diego has created a new type of electronic fabric that produces both bright light and clear sound while stretching to double its original size. The material maintains consistent performance even when repeatedly stretched, bent, and twisted.
The researchers developed a composite material that combines three key components: a soft silicone polymer (Ecoflex), an additive called Triton X, and light-emitting phosphor particles. The Triton X serves two critical functions: it helps the material store electrical energy more effectively and makes it more stretchable. When electricity passes through this composite, it causes the phosphor particles to emit light while simultaneously creating tiny vibrations that produce sound waves.
High-performance stretchable sound display. a) A conceptual illustration of a stretchable sound display. b) Schematic showing the device geometry, a photograph (University symbol mark and abbreviation KOREATECH, used with permission), and a cross-sectional microscopic image of the stretchable sound display. The scale bar is 200 µm. c) Schematic of the operation mechanism of the stretchable sound display. d) Operation of the sound display with sound-synchronized EL in the pristine state and under stretching (100% strain), bending (R = 0.8 cm), and twisting (180°) under dark and bright (inserted) conditions. e) Photographs of the wearable stretchable sound display in the straightened state of the finger (left) and in the bent state of the finger (right) under dark and bright (inserted) conditions. (Image: Reprinted with permission by Wiley-VCH Verlag)
The display achieves a brightness of 319 candelas per square meter – brighter than many smartphone screens – and generates sound at 73.7 decibels. This is within the range of normal conversation volume, though perceived loudness can vary depending on distance and environment. These capabilities remain stable even when the material is stretched to 200% of its original length.
The researchers constructed the display by sandwiching their light-emitting composite between two layers of transparent, stretchable electrodes made from an ionic gel. This gel maintains electrical conductivity even when stretched while allowing light to pass through clearly.
To demonstrate practical applications, the team created a textile display by weaving fibers coated with different colored phosphors. This woven structure can display multicolored patterns and letters while generating synchronized sound. The display changes color based on the frequency of the applied electrical signal – shifting from green at lower frequencies to blue at higher frequencies.
The material responds differently to various electrical frequencies, allowing precise control over both light and sound output. At lower frequencies, the phosphors emit green light, while higher frequencies produce blue light. This same electrical signal controls the mechanical vibrations that generate sound, enabling synchronized audio-visual effects.
The system outperforms previous stretchable displays in key areas, including stable brightness under strain, sound clarity during deformation, and durability over repeated stretching cycles. It maintains consistent brightness even after 5 000 cycles of stretching to double its length. The sound output remains clear and stable during deformation, with minimal distortion of the audio signal.
The researchers addressed a common problem in stretchable electronics by optimizing the ratio of materials in their composite. Too much Triton X would cause electrical leakage, while too little would limit stretchability. Through systematic testing, they identified the precise composition that balances these competing properties.
The current version requires operating voltages of 400-500 volts to achieve optimal performance. The research team continues working to reduce these voltage requirements while maintaining brightness and sound quality. They are also developing more sophisticated control systems for complex visual patterns and audio output.
This technology demonstrates that flexible, stretchable displays can match the performance of rigid displays while adding new capabilities like sound generation. By combining light emission and sound production in a single stretchable material, this work establishes a foundation for electronic fabrics that can provide synchronized visual and audio information.
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