Stress-generated electric potential in renal stones due to ultrasound [43.35.Cg, 43.80.Cs, 62.20.Dc].

The presence of renal calculi in the kidney causes discomfort and pain to the patients and so removal of such stones is thus important. These days, nonsurgical and noninvasive techniques are used for this purpose. In this laboratory, an ultrasonic kidney stone disintegrator is being developed. In order to know design parameters for such instrument, various physical and mechanical properties of renal calculi, have been studied. During the course of ultrasonic studies in kidney stones, "stress-generated electric potential" has been observed. The in vitro samples of the kidney stones were obtained from local hospitals in Delhi. The stones were sliced into a regular shape of 1 x 1 cm. An ultrasonic field at 2.5 and 5.5 MHz was applied to the samples normal incidence to one surface. On the two surfaces parallel to the ultrasonic beam, two electrodes were applied and an electric potential was measured across these electrodes. This stress-generated potential was measured with the help of an electrometer, and varied from 0.50 to 3.0 mV and 3.10 to 12.50 mV at the two frequencies, respectively. This investigation shows that the renal calculi exhibit a stress-generated electric voltage due to their piezoelectric property.