Top orthogonal to bottom electrode (TOBE) capacitive micromachined ultrasound transducers (CMUTs) are a new transducer architecture that permits large 2-D arrays to be addressed using row-column addressing. Here, we demonstrate the feasibility of 3-D photoacoustic imaging using N laser pulses and N receive channels. We used a synthetic aperture approach to simulate a large 2 X 2 cm array using a smaller die. A hair phantom in an oil immersion medium was excited by a laser, and the received signal was dynamically focused to obtain high-resolution images. We found the TOBE CMUT to have a center frequency of 3.7 MHz with a bandwidth of 3.9 MHz. Lateral and axial resolutions were 866 ¿m and 296 μm, respectively.

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Recently we introduced Top Orthogonal to Bottom Electrode (TOBE) Capacitive Micromachined Ultrasound Transducers (CMUTs) as novel 2D arrays capable of 3D ultrasound imaging using only N transmit/receive and N bias channels for an NxN array. Here we adapt these devices for photoacoustic imaging by biasing one column and receiving across rows in parallel, then biasing another column and receiving along rows, and repeating this procedure until all columns have been biased in turn. Only elements in rows which are biased are dominantly sensitive to receive signals. Additionally, we propose a method to bias more than one column at a time using a biasing pattern sampled from rows or columns of a Hadamard S-matrix to improve signal-to-noise ratio, and demonstrate simulation results validating the proposed theory.