Piezoelectric response of bone and tendon subjected to inhomogeneous stress
Bone and tendon are piezoelectric materials. When they are homogeneously stressed, they obey the classical or standard theory of piezoelectricity. However, this thesis shows that when bone and tendon are subjected to in-homogeneous stress, as in cantilever bending, they do not obey the classical piezoelectric theory, although the piezoelectric minerals quartz and tourmaline do. This thesis shows that an adequate, extended theory of piezoelectricity can be developed by including in addition to the usual independent variable, stress, a new independent variable, the gradient of stress. The extended theory includes the classical, piezoelectric theory as a special case. To test the predictions of the extended theory in cantilever bending, a new, null-balancing circuit was developed. This circuit detects piezoelectric voltages directly by obviating the difficulties caused by shunt capacitance between lead wires to the piezoelectric sample. Using this circuit, the magnitude of the piezoelectric voltage from the convex to the concave surface of a cantilever-bent bar (approximately 2 mm thick and 1 cm wide) of tendon or bone was measured to be in the order of 1 volt when the free end of the sample is depressed by the weight of 100 gms. This voltage is about 100 times larger than previously reported values. Our measurements also confirm the predictions of the extended theory of piezoelectricity for samples in cantilever bending. In addition, this thesis develops the predictions of the extended theory of piezoelectricity for samples subjected to pure bending.
Piezoelectric responce, bone, tendon, inhomogeneous stress, piezoelectricity
University of Illinois - Urbana-Champaign
Networked Digital Library of Theses and Dissertations