On the Piezoelectric Effect of Bone

TLDR

The piezoelectric effect in bone, analogous to that in wood or ramie, arises from the crystalline micelle of collagen fibers, whose symmetric configuration yields two equal‑magnitude but opposite‑sign constants d₁₄ and d₂₅. The authors measured piezoelectric constants in dried femoral specimens from humans and oxen using static direct, dynamic direct, and dynamic converse experiments, finding that the effect occurs only under shearing forces on collagen fibers and varies with the angle between applied pressure and the bone axis. The maximum piezoelectric constant measured was 6×10⁻⁹ cgs e.s.u., roughly one‑tenth of quartz’s d₁₁, and boiling the specimens had little effect, confirming the phenomenon is not biologically derived.

Abstract

The piezoelectric effect of bone has been observed similarly to the case of wood or ramie. The specimens were cut out from the femur of man and ox, and dried completely by heating. The piezoelectric constants were measured by three different experiments, that is, measurements of the static direct effect, the dynamic direct effect and the dynamic converse effect. The piezoelectric effect appears only when the shearing force is applied to the collagen fibres to make them slip past erch other. The magnitude of piezoelectric constant depends on the angle between the applied pressure and the axis of the bone. The maximum value of piezoelectric constant amounts to 6×10 -9 c.g.s. e.s.u., which is about one-tenth of a piezoelectric constant d 11 of quarts crystal. The specimens which were boiled in hot water and afterwards dried completely showed little change in the piezoelectric effect, the fact ascertaining that the effect is not of biological origin. The origin to piezoelectricity in bone may be ascribed to the piezoelectric effect of the crystalline micelle of collagen molecules. The consideration of the symmetry of the configulation of collagen fibres in the bone texture shows the existence of effects which are represented by only two piezoelectric constants d 14 and d 25 , which are the same in magnitude but opposite in sign.