Capacitive Micromachined Ultrasonic Transducers for Applications in Nondestructive Testing

Abstract:
Capacitive Micromachined Ultrasonic Transducers (CMUTs) are characterized by a high sensitivity in receiving and a wide bandwidth based by their physical properties. The development of these sensors was primarily driven by medical diagnostics in the last decades. CMUTs are best suited for the classical sonography because of their natural matching to water. The good adaptability to air additionally enables the application at diagnostic procedures, which do not allow the use of coupling liquids, for example on the eyeball or in the ear canal. The improvement in the optimization of the CMUT structures at the Fraunhofer IPMS enables the addressing of further fields of application such as the Nondestructive Testing (NDT). CMUTs are suitable especially for the implementation of small apertures and arrays with a large number of elements with up to 30 MHz working frequency. The advantages in comparison with piezoelectric transducers come into play particularly at imaging methods. We give an overview of the advantages of CMUT probes and show the opportunities in their application for NDT with examples. Further, we present the available ultrasonic transducers and demonstrator devices made by Fraunhofer IPMS.