Fujifilm has developed an electroacoustic film, which could be used in next-generation flexible devices.
With this new film, sound distortion can be prevented even when the film is deformed, by making its elasticity depend on frequency. As a result, the film is both flexible and produces high quality sound.
“This film is normally soft, but it becomes hard in the audio frequency range. That’s because it’s designed so that, when the ceramic vibrates in the audio range, from 20 Hz to 20 kHz, the vibrational energy is transmitted to the entire film.”
“The performance of the diaphragm in a speaker is usually expressed in terms of acoustic velocity and internal loss. The higher those are, the better. Currently, the diaphragms used in speakers are often paper cones. In the audio range, compared with a paper cone, our film has the same acoustic velocity and 2-3 times the internal loss. So, the film itself isn’t prone to producing sound, which means it delivers very high audio quality.”
This “origami speaker” is a sample, to demonstrate how flexible the film is. Although it’s not a practical product, it can produce sound without breaking, even when it’s folded in such a complicated way.
“Previously, there’s been a 100% polymer material called polyvinylidene fluoride. This material combines a ceramic with a polymer. Until now, the conventional wisdom has been that such materials usually break when they’re bent. But this film is for use at low frequencies, where it’s very flexible, so it doesn’t break.”
polyvinylidene fluoride contains a 100% polymer material combined with a ceramic material.
“In the future, it might be possible to make a retractable, thin, flexible display, by using this film in combination with an OLED display.”
The film can also be used as a sensor that converts sound to electrical signals.
“The film converts minute vibrations to electrical signals, like this. The frequency range of the human voice can be picked up like this. If placed on the vocal cords, it can also be used as a throat microphone.”