| Communications

Paper-Thin Device Acts as a Loudspeaker and Microphone

This technology has applications as a foldable loudspeaker, a voice-activated security patch for computers, or talking newspapers.

A paper-thin, flexible device was created that can generate energy from human motion, and can act as a loudspeaker and microphone. The transducer is ultrathin, flexible, scalable, and bidirectional, meaning it can convert mechanical energy to electrical energy, and vice-versa.

Like a traditional loudspeaker, this sheet-like, flexible device can transmit sound. The FENG device can be embedded into a flag or other fabric. (Photo by G.L. Kohuth)

In late 2016, the sheet-like device — a ferroelectret nanogenerator (FENG) — was used to power a keyboard, LED lights, and an LCD touchscreen. That process worked with a finger swipe or a light pressing motion to activate the devices, converting mechanical energy to electrical energy. The current technology extends the FENG’s usability. The high-tech material can act as a microphone (by capturing the vibrations from sound, or mechanical energy, and converting it to electrical energy) as well as a loudspeaker (by operating the opposite way — converting electrical energy to mechanical energy).

To demonstrate the microphone effect, a FENG security patch was developed that uses voice recognition to access a computer. The patch was successful in protecting an individual’s computer from outside users. The device’s sensitivity to vibration enables it to catch the frequency components of the human voice. To demonstrate the loudspeaker effect, the FENG fabric was embedded into a flag. Music was piped from an iPad through an amplifier and into the flag, which then exactly reproduced the sound — the flag itself became the loudspeaker. The technology could be used in the future to replace traditional speakers — which are big, bulky, and use a lot of power — with the flexible, thin, small device.

The process of creating the FENG starts with a silicone wafer, which is then fabricated with several layers, or thin sheets, of environmentally friendly substances including silver, polyimide, and polypropylene ferroelectret. Ions are added so that each layer in the device contains charged particles. Electrical energy is created when the device is compressed by human motion, or by mechanical energy.

Other potential applications of the FENG include noise-canceling sheeting and a health-monitoring wristband that is voice-protected.

Watch a demo of the device on Tech Briefs TV here. For more information, contact Nelson Sepulveda at This email address is being protected from spambots. You need JavaScript enabled to view it.; 517-432-2130.