This paper reviews capacitor micromachined ultrasonic
transducers (cMUTs). Transducers for air-borne and immersion
applications are made from parallel-plate capacitors whose
dimensions are controlled through traditional integrated circuit
manufacturing methods. Transducers for airborne ultrasound
applications have been operated in the frequency range of
0.1–11 MHz, while immersion transducers have been operated in the
frequency range of 1–20 MHz. The Mason model is used to represent
the cMUT and highlight the important parameters in the design of
both airborne and immersion transducers. Theory is used to compare
the dynamic range and the bandwidth of the cMUTs to piezoelectric
transducers. It is seen that cMUTs perform at least as well if not
better than piezoelectric transducers. Examples of single-element
transducers, linear-array transducers, and two-dimensional arrays of
transducers will be presented.
Among the biomedical imaging modalities, photoacoustic computed tomography (PACT) was one of the emerging hybrid techniques in recent years. In designing the PACT imaging system, a finite-bandwidth transducer is one of the limited factors for the overall performance. As the target size is inversely proportional to the dominant frequency components of the generated photoacoustic (PA) signal, a broad bandwidth transducer is desired for different scales' imaging. In this paper, a monolithic multiband capacitive micromachined ultrasonic transducer (CMUT) array was designed and fabricated for the reception of the wideband PA signals so as to provide high-resolution images with high-frequency CMUT arrays and present the high signal-to-noise-ratio major structure with low-frequency CMUT arrays. To demonstrate its performance, a phantom experiment was conducted to show and evaluate the various qualities of multiresolution images. In addition, an in vivo mouse model experiment was also carried out for revealing the multiscale PA imaging capability with the multiband CMUTs on biological tissues. From the obtained results, the images from different CMUT arrays could show the structures of the mouse brain in different scales. In addition, the images from the high-frequency CMUT arrays were able to reveal the major blood vasculatures, whereas the images from low-frequency CMUT arrays showed the gross macroscopic anatomy of the brain with higher contrast.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.