Research Of The Piezoelectricity Of Bone On Crack Tip

One of the important characteristics of bone tissues is that it can convert its mechanical deformations to electrical signals (SGP). It is known as the electromechanical properties which includes piezoelectricity and electrokinetic phenomena. Experiments have demonstrated that dry bone has piezoelectricity, while wet bone and living bone has electrokinetic phenomena, which is different from body bioelectricity (heart electricity, brain electricity, muscle electricity). The SGP is independent of body metabolism. It also means that SGP is merely related with chemical component, physical structure and geometrical structure of the bone. At the present time, it is thought that the reason for the bone reconstructed is that stress can produce electrical signals which can arouse the reaction of the cell and then induce the bone recreate in bone tissues. Moreover the electricity of the bone that was produced by the stress can accelerate the reconstruction of bone. Then only the voltage also can arouse the reaction of the cell and accelerate the reconstruction of bone. This has importance meanings in clinic medical treatment especially in fracture and the cure and prevent of disfigurement bone. The research of the piezoelectricity will expand to bone transplant too. So it is necessary to study the electromechanical properties of the bone substitutes. The piezoelectricity of the bone is proved by experiment in this paper.The signal of piezoelectricity is feebleness which is between 0 and±10mv. The feebleness signal was gathered by the high impedance amplifier BMA-931 (the inputting impedance > 1015?) which has preamplifier(SUPER-Z). Five cattle bones were tested, which was respectively before hatch, after hatch and have a crack already. The signal was different when the load was altered. The conclusion got from the test data is that bone possesses piezoelectricity.While the bone was loading, the signal of piezoelectricity shows an aiguille. While the accessory was uninstalling, it appears reversed signal. The arising load time is the same as the arising signal time. The piezoelectricity signal is symmetrical according to the symmetrical electrodes. All of the stresses are equal except the shear stresses which have opposite direction. The change of piezoelectricity signal is corresponding with the shear stresses. After the sample has been cracked, the shear stresses become lower. The piezoelectricity signal has the same rule too, and it is basically proportional to shear stresses. When the bone is loaded, the crack causes plasticity, or the crack is not symmetrical to the electrode. The piezoelectricity signal calculated under elasticity is not consistent with the results obtained through experiments. After the bone is loaded, piezoelectricity signal shows gradual attenuation. The laxation time is between 0.1s and 0.4s, and the piezoelectricity signal attenuates to zero finally.