Transparent Capacitive Micromachined Ultrasound Transducer (CMUT) Arrays for Photoacoustic Applications

Abstract

Photoacoustic imaging is a hybrid imaging modality that takes advantage of deep ultrasound penetration and optical contrast to provide both structural and functional information deep in the tissue. The opaque transducers used in the existing photoacoustic imaging systems impose limitations on efficient tissue illumination, leading to degraded signal-to-noise ratio. This thesis aims to overcome this issue by developing optically transparent ultrasound transducers with different form factors using capacitive micromachined ultrasound transducer (CMUT) technology. This includes introducing the first flexible transparent CMUT array with high bending reliability for photoacoustic tomography or applications requiring curved or shape-conformal arrays. In the next step towards improving the performance of these systems, a transparent CMUT array with dual-band operation is proposed for wide-band photoacoustic imaging, enhancing both resolution and imaging depth. Finally, this thesis pioneers the fabrication of a transparent row-column CMUT array for high-quality volumetric photoacoustic imaging. The introduced transparent CMUT arrays in this research allow through-illumination photoacoustic imaging, offering several benefits such as enhanced signal-to-noise ratio, elimination of blind spots, and system miniaturization. They also enable novel applications by combining photoacoustic imaging with other modalities, potentially enhancing the accuracy of imaging and diagnosis in various clinical settings. This work lays the foundation for transparent row-column CMUT arrays with large apertures, paving the way for next-generation multi-modal imaging systems with exceptional image quality and frame rate capabilities.