Sonography is a well-established method of analysis, especially in medical technology. In the form of ultrasonic arrays, the use of ultrasonic transducers is crucial for imaging techniques. The majority of ultrasonic arrays produced in medical technology today use the piezoelectric ceramic-lead-zirconate-titanate (PZT) according to the utilization of the reverse piezoelectric effect to generate sound.
High-frequency, high-resolution arrays based on PZT are, however, difficult to produce and therefore expensive. Micromachined ultrasonic transducers (MUTs), especially capacitive micromachined ultrasonic transducers (CMUTs), are providing new opportunities. The micromachining manufacturing process now allows for the economical production of high-frequency, high-resolution ultrasonic arrays. In addition, the capability for high miniaturization makes it possible to use MUTs in invasive applications such as intravascular ultrasound (IVUS).
Results from current development demonstrate the beneficial features of MUTs for the production of high-frequency arrays. A high bandwidth and low coupling are fundamental for the compatibility of MUT-based imaging with conventional medical imaging standards. For the first time, highly-integrated MEMS technology enables the signal of an array to locally connect with read-out electronics to achieve simple and compact contact between the elements. The implementation of this connection technique allows for highly planar surfaces to be used as a contact to the medium.