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Light Emitting Fibers for Crazy Clothes

The fibers can be woven into textiles could be used in so-called smart fabrics.

2 min read
Fiber-shaped polymer light-emitting electrochemical cells with tunable colors are twisted together to generate colorful lights.
Illustration: Zhitao Zhang

Thin light-emitting fibers that can be woven into textiles could be made into glowing clothes and other wearable electronics, researchers at Fudan University in Shanghai say.

Organic light-emitting diodes (OLEDs) are increasingly finding use in smartphones screens and televisions, offering a bright source of light with a wide range of colors that can be applied to rigid, curved, and even flexible surfaces. However, incorporating OLEDs into fabrics is difficult because they depend on cathodes that need relatively low amounts of energy to withdraw electrons completely from their surfaces. Such "low work function" materials—including calcium or magnesium—are sensitive to air, making them a problem for use in anything that can see as much use as fabric.

Instead, Zhitao Zhang at Fudan University in Shanghai and his colleagues explored devices known as polymer light-emitting electrochemical cells (PLECs). Like OLEDs, PLECs are usually made up of two metal electrodes connected to an electroluminescent organic semiconductor, but PLECs also incorporate salts into the light-emitting layer. This not only presents advantages such as high electron-to-photon conversion efficiency and high power efficiency compared to OLEDs, but PLECs also do not require low work function cathodes.

Now the scientists have developed a roughly one-millimeter-thick fiber-shaped PLEC consisting of a thin steel wire coated with a layer of zinc oxide nanoparticles, an electroluminescent polymer and an outer highly transparent layer of carbon nanotubes. These fibers can be twisted together and woven into patterns in lightweight, flexible, wearable textiles. Zhang, along with Huisheng Peng and their colleagues, detailed their findings online 18 March in the journal Nature Photonics.

The fibers can emit blue or yellow light from their entire surface when a few volts or more are applied between the inner metal wire and the outer carbon nanotube layer, and other colors might be possible in the future. The zinc oxide nanoparticles and the electroluminescent polymer are manufactured from simple solution-based processes that the scientists suggest could be scaled up for practical applications. The fibers "can be woven into light-emitting clothes for the creation of smart fabrics," Zhang said.

One challenge PLECs face is that their performance degrades over time: The brightness of these fibers decreases by half after only four hours of operation. However, electronics researchers Enrique Ortí and Henk Bolink at the University of Valencia in Spain, who did not take part in this study, noted in a review in Nature Photonics that PLECs now exist that can last for several thousand hours, suggesting that PLECs might one day be usable in long-lasting glowing fibers.

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Deep Learning Could Bring the Concert Experience Home

The century-old quest for truly realistic sound production is finally paying off

12 min read
Image containing multiple aspects such as instruments and left and right open hands.
Stuart Bradford

Now that recorded sound has become ubiquitous, we hardly think about it. From our smartphones, smart speakers, TVs, radios, disc players, and car sound systems, it’s an enduring and enjoyable presence in our lives. In 2017, a survey by the polling firm Nielsen suggested that some 90 percent of the U.S. population listens to music regularly and that, on average, they do so 32 hours per week.

Behind this free-flowing pleasure are enormous industries applying technology to the long-standing goal of reproducing sound with the greatest possible realism. From Edison’s phonograph and the horn speakers of the 1880s, successive generations of engineers in pursuit of this ideal invented and exploited countless technologies: triode vacuum tubes, dynamic loudspeakers, magnetic phonograph cartridges, solid-state amplifier circuits in scores of different topologies, electrostatic speakers, optical discs, stereo, and surround sound. And over the past five decades, digital technologies, like audio compression and streaming, have transformed the music industry.

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