Engineers at MIT have created a paper-thin loudspeaker that can turn any surface into a sound source.
This thin-film loudspeaker generates low-distortion sound while consuming a fraction of the energy required by regular loudspeakers. The researchers presented a hand-sized loudspeaker that weighs about a dime and can produce high-quality sound no matter what surface the film is glued to.
The researchers developed a deceptively simple fabrication technology that involves only three basic steps and can be scaled up to manufacture ultrathin loudspeakers large enough to cover the interior of a car or wallpaper a room to attain these capabilities.
Electric current inputs run through a coil of wire to generate a magnetic field, which moves a speaker membrane, which moves the air above it, and creates the sound we hear in a standard loudspeaker found in headphones or an audio system. The new loudspeaker, on the other hand, simplifies speaker design by employing a thin layer of shaped piezoelectric material that moves when electricity is applied to it, moving the air above it and producing sound.
Because the film must flex freely to produce sound, most thin-film loudspeakers are intended to stand alone. The vibrations would be hampered and their ability to make sound would be hampered if these loudspeakers were mounted on a surface.
The researchers used a laser to cut small holes in a thin sheet of PET, a lightweight plastic, to create the loudspeaker. They bonded an extremely thin film of piezoelectric material called PVDF to the underside of the perforated PET sheet (as thin as 8 microns). They then applied vacuum above the joined sheets and an 80°C heat source beneath them. The researchers have published their findings in IEEE Transactions of Industrial Electronics. Watch their demonstration on YouTube by clicking here.
“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 smidgeon of electrical power to run it,” says Vladimir Bulović, the Fariborz Maseeh Chair in Emerging Technology, leader of the Organic and Nanostructured Electronics Laboratory (ONE Lab), director of MIT.nano, and senior author of the paper.