PVDF hydrophone with liquid electrodes for shock wave measurements [in lithotripsy]

A novel hydrophone with nonmetallic electrodes is proposed. The polyvinylidene fluoride (PVDF) film hydrophone is polarized over a small area at its center. The electrical charges on this sensitive area are then driven electrically to the external leads through an electrolyte. With a thin 9-mm PVDF foil and an unmetallized sensitive area of 1 mm, the resulting hydrophone has a sensitivity of 12 mV/MPa over a bandwidth of about 20 MHz. More than 10⁵ focused shock pulses of 30 MPa have been measured without any significant decrease in hydrophone sensitivity