The piezoelectricity of semicrystalline biopolymers was first discover
ed for wood and bone in the 1950's. piezoelectric properties have sinc
e been investigated for a number of biological substances, including p
olysaccharides, proteins and deoxyribonucleates. The shear piezoelectr
ic constants -d(14) = d(25) were determined for their oriented structu
res with a uniaxial symmetry D-infinity. From studies of synthetic pol
ypeptides and optically active polymers, it was concluded that the ori
gin of piezoelectricity lies in the internal rotation of dipoles such
as CONH, Values of d(14) = -10 pC/N were determined for highly elongat
ed films of poly-L-lactic acid, optically active and biodegradable, Th
e implantation of this polymer induced the growth of bone, possibly be
cause ionic current caused by piezoelectric polarization stimulated th
e activity of bone cells. Submicron-thick polyurea films were prepared
by evaporating diisocyanate and diamine monomers in vacuum, After pol
ing, the films exhibited pyro- and piezoelectric effects. The tensile
piezoelectric constant d(31) = 10 pC/N persisting up to 200 degrees C
was also observed for aliphatic polyurea films.