Designing two-dimensional film speakers using piezoelectric materials

A speaker is an acoustic device which produces sound through electromechanical operations. Most speakers are comprised of three-dimensional devices such as a voice coil, a permanent magnet, and an enclosure. An ac voltage applied to the voice coil generates displacement of the cone due to the magnetic interaction between the magnet and the voice coil. The displacement produces audio sound waves. Recently, many mobile electronic devices such as mobile phones have become smaller, lighter, and thinner for the sake of convenience and due to advanced technologies. A problem with this miniaturization, however, is that the volume of the produced output sounds has also decreased. In contrast to conventional three-dimensional speakers, we have designed a new type of two-dimensional flexible speaker based on the use of reverse piezoelectric effect on certain piezoelectric materials. This would be very useful in today's increasingly thinner consumer electronics devices such as mobile phones. There are other applications such as clothes, wearable computers, raincoats, etc.