The piezoelectric effect has been studied in wet and dry human bones using a piezoresponse force microscope (PFM). It allowed to measure piezoelectric response with nanometer scale resolution directly in a collagen matrix and to obtain a piezoresponse image near the Haversian channel. Dielectric response and dc conductivity have been measured. Theoretical calculations taking into account the inhomogeneity of the electric field under the PFM tip apex and its screening in highly conductive bone samples were performed for obtaining the piezoelectric coefficient in the bone collagen.Ferroelectric phenomena have been observed in many biological materials. The origin of these fundamental physical properties is ascribed to high structural ordering of biological systems at any level that is a low symmetry configuration of elementary cells based of their helical or chiralic dissymmetry. Linear electrooptic effect has been found in nerve fibers. 1 Dielectric spectroscopy studies of oriented purple membranes showed that bacteriorhodopsin, which is an integral membrane protein, possesses a significant electrical dipole moment and demonstrates a liquid crystal-like ferroelectric behavior. 2 This experiment was a direct confirmation of the theoretical model of ion channels in a biological membrane 3,4 acting as electric switches between ferroelectric (closed, insulating) and paraelectric (open, ion-conducting) states. Plants and animal and human tissues (protein amino acids, pineal gland of brain, bones, skin, tendon, etc.) reveal pronounced piezoelectric 5,6 and pyroelectric properties. 7-9 Reports on the observation of pyroelectric effect 7-9 was a first evidence of the existence of macroscopic spontaneous electrical polarization in bones. Application of an ac electric field to the cortical human bone allowed to observe reversal of the spontaneous polarization by recording dielectric hysteresis loop. 10 Both piezoelectric and pyroelectric phenomena were related to collagen, which is an organic crystalline matrix of the bone composed from strongly aligned polar organic protein molecules. 11 It was proposed that the piezoelectric effect plays an important physiological role in bone growth, remodeling, and fracture healing. 12In this paper we report on studies of piezoelectric effect in moist and dry human bones by the use of a piezoresponse force microscope (PFM). It allowed both to measure piezoelectric response with nanometer scale resolution directly in a collagen matrix and to obtain a piezoresponse image near the Haversian channel. Theoretical calculations, taking into account the inhomogeneity of the electric field under the PFM tip apex and screening of the applied electric field, were performed for obtaining the piezoelectric coefficient in bone collagen.Human adult humerus and tibia diaphysial fragments were used for sample preparation. Bones were supplied by The Israeli National Bone Bank at the Chaim Sheba Medical Center. All the bones were obtained from young (<45 years of age) individuals during organ harvesting a...

In this work the piezoresponse mode of the atomic force microscope has been applied for piezoelectric coefficient measurements in nanometer scale in high conductive RbTiOPO4 and KTiOPO4 ferroelectric crystals with specifically tailored domain configurations. A strong dependence of the amplitude and phase contrast between oppositely polarized domains on the frequency of the measuring alternate voltage was observed, and allowed the finding of the optimal conditions for piezoelectric coefficient measurements. A theoretical method, taking into account the inhomogeneity of the electric field under the atomic force microscope tip apex, the screening of the applied electric field, and the elastic clamping of the piezoelectrically excited region by the surrounding matrix has been developed for obtaining d33 in ferroelectrics with high ionic conductivity.