0

Engineers develop paper-thin, flexible speaker

Imagine covering your walls with squares of thin metallic speaker instead of floral wallpaper; you could pop your favorite Queen song in full surround sound, or cancel out the noise of your argumentative neighbors.

This fantasy is closer than you might think, with electrical engineers at the Massachusetts Institute of Technology (MIT) in the US developing a paper-thin speaker that can generate high-quality sound, no matter what surface it’s attached to. the movie.

Weighing just 2 grams and 120 nanometers thick, this thin-film speaker produces sound with minimal distortion and uses a fraction of the power required by a traditional speaker.

Engineers have pioneered a simple manufacturing technique of just three basic steps that can be scaled up to produce speakers large enough to line the interior of a vehicle or wallpaper a room, according to a new study published in IEEE Transactions on Industrial Electronics.

“It feels extraordinary to take what looks like a thin sheet of paper, put two clips on it, plug it into your computer’s headphone port, and start listening to sounds emanating from it,” says lead author Vladimir Bulović, a professor of electrical engineering. at MIT.

“It can be used anywhere. You just need a pinch of electrical power to make it work.”

The speaker works by vibrating thousands of tiny domes

A typical loudspeaker uses electrical current inputs that pass through a coil of wire that generates a magnetic field. This moves a speaker membrane which moves air over it, producing the sound we hear.

This new paper-thin speaker simplifies this design by using a thin film of a piezoelectric material (polyvinylidene fluoride, PVDF) formed into thousands of tiny domes, just a few hairs wide, that individually vibrate when voltage is applied to them. a phenomenon called the reverse piezoelectric effect.

Engineers used a laser to cut tiny holes in a thin sheet of PET, a type of lightweight plastic, the bottom of which they laminated with a thin PVDF film. By applying a vacuum above the sheets and a heat source (80°C) below, the pressure difference causes the thin PVDF layer to protrude through the tiny holes, forming domes.

They are surrounded by spacer layers of PET on the top and bottom of the film that protect them from the mounting surface and allow them to vibrate freely, thus preventing abrasion and impact during daily handling and improving the speaker’s durability. .

“This is a very simple and straightforward process. It would allow us to produce these speakers with high performance if we integrate it with a roll-to-roll process in the future,” says lead author Jinchi Han, a postdoctoral researcher at MIT’s ONE Lab.

“That means it could be made in large quantities, such as wallpaper to cover walls, cars or airplane interiors.”

Each dome is a single sound-generating unit, so it takes thousands of these tiny domes vibrating together to produce audible sound.

Potential applications in aircraft and immersive entertainment.

Engineers found that when 25 volts of electricity were passed through the device at 1 kilohertz, the speaker produced high-quality sound at conversation levels of 66 decibels at 30 cm away. At 10 kilohertz, the sound pressure level increased to 86 decibels, about the same volume level as city traffic.

It’s also incredibly energy efficient, requiring only around 100 milliwatts of power per square meter of speaker, compared to an average home speaker that might draw more than 1 watt of power to generate similar sound pressure. at a comparable distance.

So while wallpapering your bedroom may not be the most useful application of this remarkable technology, the authors say it could be used for noise cancellation, in an airplane cabin, for example, by generating sound of the same amplitude. but opposite phase so that the two sounds cancel each other out.

It could also be used for immersive entertainment by providing three-dimensional audio, and because it is lightweight and requires such a small amount of power to run, the device is ideal for applications on smart devices where battery life is limited.