Skip to Content
MIT News: 77 Mass Ave

Paper-thin loudspeakers

Big sound from a thin film.

June 29, 2022
ultrathin loudspeaker
This lightweight, thin-film loudspeaker requires very little power to operate, making it well-suited for applications on smart devices with limited battery life.Felice Frankel

MIT engineers have developed a paper-thin, low-power loudspeaker that can turn any surface into an active audio source.

This thin-film loudspeaker produces sound with minimal distortion while using a fraction of the energy required by a traditional loudspeaker. A hand-size version weighs about as much as a dime and can generate high-quality sound no matter what surface the film is bonded to.

The researchers’ deceptively simple fabrication technique requires only three basic steps and can be scaled up to produce ultrathin loudspeakers large enough to cover the inside of an automobile or to wallpaper a room.

Such speakers could provide active noise cancellation in clamorous environments, such as an airplane cockpit, by generating sound of the same amplitude but opposite phase; the two sounds cancel each other out. The flexible device could also be used for immersive entertainment, perhaps by providing three-dimensional audio in a theater or theme park ride. It is well suited for applications in smart devices where battery life is limited.

“It feels remarkable to take what looks like a slender sheet of paper, attach two clips to it, plug it into the headphone port of your computer, and start hearing sounds emanating from it. It can be used anywhere. One just needs a smidgen of electrical power to run it,” says professor Vladimir Bulović, director of MIT.nano and senior author of the paper along with electrical engineering professor Jeffrey Lang. Postdoc Jinchi Han is lead author.

A typical loudspeaker uses electric current inputs that pass through a coil of wire, which generates a magnetic field. This moves a speaker membrane, which moves the air above it to make the sound we hear. By contrast, the new loudspeaker uses a thin film of a shaped piezoelectric material that expands and contracts when voltage is applied over it, which moves the air above it and generates sound.

Most thin-film loudspeakers are freestanding because the film must bend freely to produce sound, and mounting them onto a surface would impede the vibration. So rather than having the entire material vibrate, the new design relies on tiny domes on a thin layer of piezoelectric material, each of which vibrates. These domes, each only a few hair-widths across, are surrounded by spacer layers on the top and bottom of the film that protect them from the mounting surface while still enabling them to vibrate freely. The same spacer layers protect the domes from abrasion and impact during day-to-day handling, enhancing the loudspeaker’s durability. 

Because the tiny domes are vibrating, rather than the entire film, the loudspeaker has a high-enough resonance frequency to be used effectively for ultrasound applications like imaging, Han says. Ultrasound imaging uses very-high-­frequency sound waves to produce images, and higher frequencies yield better image resolution.

Keep Reading

Most Popular

Here’s how a Twitter engineer says it will break in the coming weeks

One insider says the company’s current staffing isn’t able to sustain the platform.

Technology that lets us “speak” to our dead relatives has arrived. Are we ready?

Digital clones of the people we love could forever change how we grieve.

How to befriend a crow

I watched a bunch of crows on TikTok and now I'm trying to connect with some local birds.

Starlink signals can be reverse-engineered to work like GPS—whether SpaceX likes it or not

Elon said no thanks to using his mega-constellation for navigation. Researchers went ahead anyway.

Stay connected

Illustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.