Ultrasound Transducers Based on Ferroelectret Materials

Ferroelectret materials can be utilized to set up electroacoustic transducers. The materials offer both, a rather large bandwidth and a high piezoelectric strain constant. Due to its cellular structure, the material is flexible and exhibits an excellent matching to air. Therefore, this polymer is appropriate for many sound as well as ultrasound transducer applications. Our research is concentrated on the simulation based design and characterization of ultrasound transducers. In this contribution, we present a finite element based modeling of the cellular structured ferroelectret materials. In particular, a microscopic as well as a macroscopic model is discussed. We fabricate single element and array transducers based on ferroelectret materials, namely the so-called EMFi (Electro-Mechanical-Film) material. To show the applicability of ferroelectret materials for ultrasound transducers, different applications in air and water are presented. An emitter-receiver-unit is introduced which is utilized in an artificial bat head and allows the functional reproduction of the biosonar system found in bats. Moreover, a robust sensor array consisting of 16 single elements (4x4) is studied. With the aid of this sensor array, cavitation effects in ultrasonic cleaning systems can be investigated on the specimen's surface, which is not possible with common ultrasound sensors, e.g., hydrophones.