Development of a PVDF low-cost shock-wave hydrophone

During a few past years a series of shock-wave generators for lithotripsy and/or tissue destruction studies have been developed in our laboratory. Based on the experiences in shock wave measurements and the drawbacks in existing hydrophones, we have developed a very low-cost, wideband, reproducible shock-wave hydrophone. The key element of this device is the rapidly mounting, disposable PVDF membrane. This is a commercially available PVDF shock gauge which is poled by a patented cyclic poling technique. To obtain the widest possible bandwidth, we have adopted a special coplanar membrane design. The PVDF film is sandwiched between the surfaces of a P.V.C. and a metallic plate of brass which the latter is in contact with the surrounding medium. On the other hand, the active lead is isolated from medium and it is in contact with an isolating liquid (degassed petroleum) held in a cylindrical chamber over the membrane. By the incorporation of this design, the hydrophone can be used for shock wave measurements even in conductive media like different physiological liquids, with a negligible change of sensitivity.