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The direct and converse piezoelectric effects have been observed in the Achilles tendon of ox and horse, which consists of collagen fibers in which the collagen molecules are highly orientated and crystallized. The matrix of piezoelectric constant is concordant with that derived for and unidirectionally oriented system of crystallites of collagen with a hexagonal symmetry. The magnitude of piezoelectric constant is: - d 14 = d 25 =8.0×10 -8 , d 15 = d 24 =4.2×10 -8 , d 31 = d 32 =0.26×10 -8 , d 33 =0.2×10 -8 c.g.s.e.s.u. respectively, which are the largest values observed in the crystalline polymers. The origin of the effect is supposed due to the polarization or displacement of hydrogen bonds being formed in the polypeptide chains of collagen crystals. The gramophone pick-up can be made by using the thin sheet of tendon as an electromechanical transducer.
Fukada et al. (Sat,) studied this question.