Piezoelectric Materials Applications for Cardiovascular Devices

Website designed by: Luis Alonzo



Piezoelectricity is defined as the ability of certain materials to develop a dielectric displacement due to an applied stress and, conversely, develop a strain in response to an electric field [1]. Normally, the charges within a piezoelectric material are well balanced regardless of their distribution. This balance results in no net charge on the material faces. The piezoelectric effect relies on the asymmetric charge distribution within individual crystalline units. Upon application of a mechanical force on the material, the positive and negative charges are displaced with respect to one another. The displacement results in a change in polarization of the material, which yields a measurable electrical potential. This effect can be represented graphically in the animation below [2]:

Similarly, when a piezoelectric material is exposed to an electric field, it experiences a lengthening or shortening according to the polarity of the field, and in proportion to the strength of the field [1].

The physical basis of piezoelectricity (i.e.  electrical and mechanical behavior) is best described by combined relations of Gauss’ Law and Hooke’s Law. The relationship between the electrical and mechanical properties of piezoelectric materials is governed by the following equations [3]:

where i, j, m = 1, . . ., 6 and k, l, n = 1, 2, 3. Also, S, D, E, and T are the strain, dielectric displacement, electric field, and stress, respectively. And sijE, dkl, and elnT are the elastic compliances, the piezoelectric constants, and dielectric permittivities.

Materials exhibiting the piezoelectric effect include a variety of naturally occurring crystals, natural materials, manufactured crystals, manufactured ceramics, and special man-made polymers. The ideal material may be selected based on the application, since certain materials are more efficient than others. The table below describes the properties of some commonly used piezoelectric materials [4]:

Since their discovery in the 19th century, piezoelectric materials have been used for a variety of applications, from power sources to actuators. In medicine, one of their main uses is in the field of imaging, such as in piezoelectric ultrasound imaging. This technology relies in the change of shape of piezoelectric materials due to an applied electrical current or sound/pressure waves hitting the material. Recently, new and potential applications have emerged for piezoelectric materials within the field of cardiology. This website will focus on two of these recent developments within cardiovascular devices, among which are: ventricular assist devices, and artificial heart valve sensors.