New technique for spot-poling piezopolymer membrane hydrophones

Abstract

One characteristic that poses a lower limit to the size of existing spot-poled membrane hydrophones is that the active region is always larger than the electroded region. The difference is due in part to the fringe poling fields that surround the electrodes and proximal portions of the leads. This effect makes it difficult to construct hydrophones having dimensions less than ≃0.5 mm. A potential way around this problem is to reverse the standard poling and plating process. That is, the film is first poled and then the metal electrodes and leads are added. This approach has been applied using small (< 0.1-mm tip diameter) needles as poling electrodes. Piezopolymer film was mounted on support rings and a central spot was poled at room temperature. Electrodes and leads were vacuum deposited, and sensitivity and directional response measurements were made. In this presentation, details of the poling process will be described and measurement results will be discussed.