Effect of water on piezoelectric, dielectric, and elastic properties of bone

The complex piezoelectric constant (d = d′ − id″), elastic constant (c = c′ + ic″), and dielectric constant (ε = ε′ − iε″) were measured at a frequency of 10 Hz over the temperature range from −150 to 50°C and for a range of hydration up to 0.26 g/g for decalcified bone and up to 0.084 g/g for bone. For decalcified bone, ε′ and ε″ increased with increasing hydration with a deflection at the critical hydration hc = 0.08 g/g;d′ at −150°C increased below hc but decreased above hc with increasing hydration; c′ increased below −60°C but decreased above −60°C with increasing hydration; and the peak temperatures of ε″, d″, and c″ below −50°C agree with each other and decreased with increasing hydration with a deflection at hc. For bone, similar hydration and temperature dependences were observed for ε and c. However, the dependence of d on hydration and temperature was different from that of decalcified bone, reflecting a two‐phase structure consisting of collagen fibers and mineral hydroxyapatite. The critical hydration for bone was 0.04 g/g.