Transparent transducers and fast electronics for next-generation ultrasound and photoacoustic imaging

Abstract

Most ultrasound transducers are opaque. Transparent transducers could lead to novel applications, including combined optical and ultrasound imaging, photoacoustic imaging and other multi-modality systems. This thesis introduces transparent capacitive micromachined ultrasound transducers and demonstrates their use for some of these novel applications. Our long-term objective is to develop 2D row-column arrays for 3D ultrasound, photoacoustic, and optical imaging. The achievement of this long-term objective requires stepwise innovation. We first demonstrate 1D array transparent CMUTs, then overcome optical and electrical material property challenges to fabricate the first-ever transparent linear arrays. We demonstrate these arrays for photoacoustic imaging and combined ultrasound and optical imaging. We additionally take steps toward mitigation of dielectric charging problems in these CMUTs using novel thin-film processes. As a step towards 3D \& 4D imaging with row-column arrays, we first design and fabricate needed fast bias-switching electronics and demonstrate their use with non-transparent row-column arrays. Finally, we outline a roadmap for achieving transparent 2D arrays and postulate their future utility for next-generation 3D multi-modal imaging.