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...

We observe a stringlike domain penetration from a ferroelectric surface deep into the crystal bulk induced by a high voltage atomic force microscope tip. The domains, which resemble channels of an electrical breakdown, nucleate under an electric field of around 10(7) V/cm at the ferroelectric surface, and grow throughout the crystal bulk where the external electric field is practically zero. A theory explaining the shape of the formed domains is presented. It shows that the driving force for the domain breakdown is the decrease of the total free energy of the system with increasing domain length.

We present a novel method for simultaneously phase matching several nonlinear optical interactions within a single crystal. Quasiperiodic modulation of the nonlinear coefficient enables one to achieve high frequency mixing efficiencies for interactions with arbitrary wave vector differences. Doubling of two different frequencies as well as direct frequency tripling is experimentally demonstrated. The temperature- and wavelength-dependent properties of these interactions are explored. We discover that periodic approximation to the quasiperiodic structure shifts the phase-matched wavelengths.

We have developed a high voltage atomic force microscope that allowed us to tailor submicrometer ferroelectric domains in bulk ferroelectrics. One- and two-dimensional domain configurations have been fabricated in LiNbO3, RbTiOPO4, and RbTiOAsO4 ferroelectric crystals. It is found that the application of superhigh electric fields (reaching 5×107 V/cm) by the atomic force microscope tip leads to a unique polarization reversal mechanism, and open the way to a technology for photonic and acoustic devices.