Nanotechnology researchers at Michigan State University have created a flexible, paper-thin device that can act as both a loudspeaker and microphone, potentially leading the way to consumer products such as a foldable loudspeaker… a voice-activated security patch for computers… even a talking newspaper.
The device, known as a ferroelectret nanogenerator, or FENG, is based on a silicone wafer fabricated with several thin sheets of substances such as silver, polyimide and polypropylene ferroelectret. Ions are added to create charged particles in each layer; electrical energy is created when the device is compressed by mechanical energy. A demonstration in late 2016 showed that the device was capable of generating energy from human motion, such as by powering a device in response to a finger swipe or light pressing motion. The discovery of audio capabilities extends the FENG’s usability.
"This is the first transducer that is ultrathin, flexible, scalable and bidirectional, meaning it can convert mechanical energy to electrical energy and electrical energy to mechanical energy,” said Nelson Sepulveda, MSU associate professor of electrical and computer engineering and primary investigator of the federally funded project.
Researchers developed a FENG security patch to demonstrate the microphone effect; sensitive to the vibrations of an individual voice, it successfully protected a computer from access by outside users. For the loudspeaker effect, the researchers embedded FENG fabric into an MSU Spartan flag, flawlessly piping in music. "The flag itself became the loudspeaker," Sepulveda said. "We could use it in the future by taking traditional speakers, which are big, bulky and use a lot of power, and replacing them with this very flexible, thin, small device."
“Imagine a newspaper," he continued, "where the sheets are microphones and loudspeakers. You could essentially have a voice-activated newspaper that talks back to you."
"Many people are focusing on the sight and touch aspects of flexible electronics," added Wei Li, MSU engineering researcher and lead author of the team's paper in Nature Communications. "We're also focusing on the speaking and listening aspects of the technology."
Additional applications of the FENG could include noise-cancelling sheeting, and a health-monitoring, voice-protected wristband.