MEMS AE Hydrophone

Most single element hydrophones depend on a piezoelectric material that converts pressure changes to electricity. These devices, however, can be expensive, susceptible to damage at high pressure, and/or have limited bandwidth and sensitivity. We have previously described the acoustoelectric (AE) hydrophone as an inexpensive alternative for mapping an ultrasound beam and monitoring acoustic exposure. The device exploits the AE effect, an interaction between electrical current flowing through a material and a propagating pressure wave. Previous designs required imprecise fabrication methods using common laboratory supplies, making it difficult to control basic features, such as shape and size. This study describes a different approach based on MEMS processing that allows for much finer control of several design features. In an effort to improve the performance of the AE hydrophone, we combine simulations with bench top testing to evaluate key design features, such as thickness, shape, and conductivity of the active and passive elements. The devices were evaluated in terms of sensitivity, frequency response and accuracy for reproducing the beam pattern. AE ultrasound detectors may also be useful for monitoring acoustic exposure during therapy or as receivers for photoacoustic imaging.

1. Zhaohui Wang, Pier Ingram, Ragnar Olafsson, Charles L. Greenlee, Robert A. Norwood, Russell S. Witte. “Design considerations and performance of MEMS acoustoelectric ultrasound detector,” IEEE Trans. on Ultrasonics, Ferroelectrics and Frequency Control, vol. 60, no. 9, pp. 1906-1916, 2013.

2. Zhaohui Wang, Pier Ingram, Ragnar Olafsson, Charles L. Greenlee, Robert A. Norwood, R.S. Witte. ''Simulation-based optimization of the acoustoelectric hydrophone for mapping an ultrasound beam,'' Proceedings of SPIE 7629, 76290Q (2010).