Technology

The FENG Is A Microphone and Loudspeaker In One Paper-Thin Device

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Home speakers have gotten smaller over the years—think of your smartphone, earphones, and other listening devices compared to your parents' giant stereo system—but the science behind them has largely remained the same. That is, until now. Researchers at Michigan State University have revolutionized audio technology with the development of the ferroelectret nanogenerator, or FENG device. It's a paper-thin, foldable technology that can be used as a speaker or microphone, and can generate its own power as a user moves around.

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MSU engineering researchers Nelson Sepulveda, right, and Wei Li, and the flag that became a loudspeaker.

Amazing Tech Made Even More Amazing

Led by associate professor of electrical and computer engineering Nelson Sepúlveda, a team of researchers at Michigan State University sought to create an environmentally friendly technology that could harvest electricity produced by human activity, such as walking or running, and convert that energy into power for personal electronics. In 2016, they revealed their ultra-thin device, which proved to be capable of converting enough mechanical energy into electrical energy to power common home electronics, including a keyboard, an LED touchscreen, and other devices with a simple touch or swipe of a finger. Their invention was undeniably impressive, and had the researchers already setting their sights towards the future. They believed these early innovations were only the start of what was possible using FENG technology.

They were right. What they discovered was that not only could the FENG be used for power, but it could be used as an audio device as well. The device originally turned mechanical energy (walking, for instance) into electrical energy to charge devices, but they found that it could also turn the device into a microphone by converting the mechanical energy of sound vibrations to electrical energy. It also went the opposite direction: when electrical energy is turned into mechanical energy, it creates a loudspeaker.

The FENG is a flexible device that can transmit sound. One day, it could lead to foldable loudspeakers or an audio newspaper.
MSU engineering researchers Nelson Sepulveda, left, and Wei Li.
Nelson Sepulveda, associate professor of engineering at MSU, and his ultra-thin, foldable keyboard that can harvest energy from human motion.

Hoist A Flag To FENG

The size and flexibility of the FENG device is just one of its impressive elements. It's also incredibly sensitive. The researchers demonstrated its microphone abilities by using it to install a voice-recognition security patch on a computer, which worked flawlessly. "The device is so sensitive to the vibrations that it catches the frequency components of your voice," Sepúlveda said in a press release.

To demonstrate its speaker capabilities, the researchers embedded the flexible device into the fabric of a flag. That way, the flag became its own loudspeaker. The applications of this are almost hard to fathom—imagine a speaker you could stick between the pages of a book or an article of clothing that plays music as you walked. "Or imagine a newspaper," Sepúlveda said, "where the sheets are microphones and loudspeakers. You could essentially have a voice-activated newspaper that talks back to you."

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