Researchers at MIT (Massachusetts Institute of Technology), one of the most prestigious science and technology laboratories in the world, announced an invention that can turn any surface into a speaker: a speaker the thickness of a sheet of paper. of paper.
The device is not only thin: its weight is the same as a coin, the sound quality (according to the inventors) is high and the power consumption level is low. This ultra-thin speaker can be used to upholster the interior of a vehicle or as wallpaper in a home.
“It can be used anywhere. It just takes a little bit of electrical energy to work,” says Vladimir Bulović, director of the MIT nanotechnology laboratory and author of the scientific paper describing the invention, published this week in the journal IEEE Transactions of Industrial Electronics.
In the video below, you see a demonstration of the technology: a paper-thin speaker playing “We Are The Champions” by the British band Queen.
To understand how the ultra-thin speaker works, we first need to understand how the models we use today in headphones, computers, cell phones, TVs and speakers work—a design that has worked well for over 150 years but needs a lot of energy and space to operate.
A normal speaker is made of a coil of wire that, when it receives an electric current, generates a magnetic field. This magnetic field moves a membrane which, in turn, moves the air above it at a rate and speed that our ear perceives as sound.
The new MIT loudspeaker cuts the way: instead of using a coil of wire to conduct the electric current to the membrane, the invention makes use of a piezoelectric material called PVDF (a kind of plastic) that vibrates when it receives a electrical charge, and by itself generates the sound we hear.
So far, nothing new: Scientists have used this technique before to create ultra-thin speakers. The problem is that prototypes made in the past were extremely delicate — any touch or pressure could stop the vibration and silence them.
Microscopic bubbles vibrate and make the leaf emit a sound
What’s new is that MIT found a way to make them firmer: instead of making the entire material vibrate, the researchers used a sheet of lightweight PET plastic with tiny laser-cut holes. A layer of PVDF was then laminated to the underside of the sheet and then both layers were vacuum sealed and subjected to a heat of 80 degrees Celsius.
The heat caused the PVDF layer to protrude through the holes, creating tiny bubbles smaller than the thickness of a human hair. Thousands of these microscopic bubbles vibrate and move air when they receive an electrical current, creating sound regardless of contact or pressure.
Because the vibration is so small (each bubble rises and falls in a space of less than 1 micrometer), just 100 milliwatts of electricity is enough to power one square meter of the speaker. As a comparison, an average speaker today needs at least 1 watt to produce similar sound.
“It’s amazing to be able to take what appears to be a thin sheet of paper, attach two paper clips to it, plug it into your computer’s headphone port, and start hearing sounds emanating from it,” says Bulović, in the announcement. on the MIT website.
“This is a very simple and straightforward process. We can produce these loudspeakers on a large scale if we use roll-to-roll processing,” says Jinchi Han, a postdoctoral fellow at MIT, who collaborated on the research, referring to the process of mass manufacturing of flexible electronics.
“This means that [este alto-falante] can be manufactured in large quantities, as wallpaper to cover walls, cars or aircraft interiors”, adds the researcher.
In addition to listening to music, MIT’s ultra-thin speaker can also be used as a noise-canceling system, emitting a sound frequency opposite to the sound outside an airplane, for example, making flights far less uncomfortable.
The researchers just don’t know when this technology will hit the market, but part of the study was funded by automaker Ford, which may be interested in coating its cars with the ultra-thin speaker in the future. “The options for how to use this technology are endless,” says Bulović.