This ultra-thin speaker is only 0.12mm, can be mounted on many different surfaces easily
Usually loudspeakers work by vibrating a membrane, and this membrane manipulates the air above it to create sound waves. In the speakers of an audio system or headphones, that process is done using electric currents and magnetic fields.
But in recent years, scientists have developed several ways to achieve the same results while keeping the speaker slim. Ultra-thin loudspeakers work by using piezoelectric materials, which oscillate under the effect of voltage. They have been used in phones and TVs and even experimentally to create unusual speakers as thin as a flag.
The problem is that these thin speakers need to be placed freely or have some separation from another surface. Attaching them will reduce the possibility of vibration and sound generation. But in the new study, MIT researchers redesigned thin speakers so that they can be mounted on a variety of surfaces.
Instead of letting the entire surface of the membrane vibrate, the team formed the material into a network of raised domes. They vibrate independently of each other. This is done by sandwiching a thin layer of piezoelectric material, just 8 micrometers thick, between two layers of PET plastic. The PET layer has a network of small holes that help the piezoelectric material protrude. The underlying PET layer protects the membrane and allows the speaker to attach to the surface.
Jinchi Han, lead author of the study said: “It’s a very simple and straightforward process. It will allow us to manufacture these speakers in a high-throughput fashion if we integrate it with roll-to-roll in the future. which means it can be made in bulk as wallpaper to cover walls, cars or aircraft interiors”.
The speaker is only 120 microns (0.12 mm) thick and weighs only 2 grams with thousands of small domes 15 micrometers high. To test the device, the researchers attached it to a wall and measured its output with a microphone 30 centimeters away. The speaker can produce up to 66 decibels (dB) of sound with 25V at 1 kHz and 86 dB at 10 kHz. The unit is also energy efficient as the output is only about 100 milliwatts per square meter of loudspeaker.
Together with the thin, mountable diaphragm, the team says the device could be used as an ultrasonic wave detector or, if coated with a reflective material, could create unique displays of light.
The study was published in the journal IEEE Transaction of Industrial Electronics.
Scientists at MIT create an ultra-thin speaker model that can be glued to many surfaces
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