MEMS ultrasonic transducers for the testing of solids

Arrays of capacitive diaphragm ultrasonic transducers could potentially be used for non-destructive ultrasonic testing and structural monitoring. In this paper, we consider the efficiency of coupling of these transducers to solid media. We show that efficient coupling can be realized by using a silicone coating as a coupling medium. We present the results of experimental characterization of ultrasonic transducers coupled to solids in this way. We show that these transducers can be used with piezoelectric emitting transducers within the range from 1 to 5 MHz, and we demonstrate the use of several transducers as a phased array to determine the direction and distance of an ultrasonic source.