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Eiichi Fukada - Piezoelectricity from Wood

See Quarterly Reviews of Biophysics: Piezoelectric properties of biological polymers. Eiichi Fukada:

Piezoelectricity and pyroelectricity in wool and hair were observed by Martin early in 1941. The piezoelectric effect in wood was investigated in detail by Bazhenov (1961). Both converse and direct effect of shear piezoelectricity in wood was demonstrated by Fukada (1955). Bending piezoelectricity in bone was first discovered by Yasuda (1953). Shear and longitudinal piezoelectricity in bone and tendon was quantitatively investigatged by Fukada & Yasuda (1957, 1964).

See ETH Zurich Oral-History:Eiichi Fukada:

In this interview, Dr. Fukada describes his childhood, his undergraduate research at the University of Tokyo in the final days of World War II, the founding of the Kobayasi Institute of Physical Research, and his early research on the elastic properties and piezoelectricity of wood. He discusses his meeting with Dr. Iwao Yasuda and their discovery of piezoelectricity in bone in 1957 and its long-term importance.

... My first work in the Kobayasi Institute was the vibrational property of wood. So first I measured the dynamic elasticity and damping of wood plates including interestingly the very old timbers taken from the temples of Japan. We have many temples, 300 to 1300 years old in Japan. The oldest is Horyuji in Nara that is 1300 years old. Professor Kohara of Saikyo University in Kyoto gathered these old timbers for the study and I was fortunate to get me some parts. And I measured the elastic properties of these woods, and I was aware of the piezoelectricity of wood later. So at that time I investigated both elastic constants and piezoelectric constants for the old timbers. Both constants increased with the passage of time until 300 years, and then decreased until 1300 years. The values for 1300 years were almost same as those for wood recently cut in the mountain.

...

As a matter of fact, I will come back to the piezoelectricity of wood. So, but at that time, most people didn’t believe that wood had crystals and such material have piezoelectricity. Not many people believed it.

[Laughter]

But, I have curiosity so I wanted to write an article on piezoelectricity in wood. So I cut samples in many directions, and first I pressed using a lever and I put the foils on the sample of wood and the clamp with a galvanometer, and then I pressed the lever with a galvanometer, move it or not. I tried, but no such a success. It is a very small effect. So at that time Dr. Kawai gave me one suggestion: how about to use the dynamic measurement. So I originally worked on Rochelle Salt. [Potassium sodium tartrate] Rochelle Salt is very sensitive piezoelectric crystal. So I made about one centimeter cubic wood and pressed it with Rochelle Salt crystals together by metal, metal frame. And then I gave an AC field to the wood. Then the wood vibrates, so that vibration could be detected by Rochelle Salt. It is really converse piezoelectric effect. And so, by this combination of wood and ceramics, if you use the AC field on Rochelle Salt, Rochelle salt vibrates, and that is transmitted to the wood, then the wood shows AC voltage due to the direct piezoelectric effect.

That sounds like a musical instrument to me: