NanoDay 2020 Poster 17- Haoran Wang

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A High-density and Dual-frequency pMUT Array based on Thin Ceramic PZT for Endoscopic Photoacoustic Imaging

Haoran Wang (LinkedIn)

Authors: Haoran Wang, Philip X.-L. Feng, Huikai Xie

Faculty Mentor: Philip Feng, PhD

College: College of Engineering

Department: Electrical and Computer Engineering


Ultrasonic transducer, as a key component in photoacoustic imaging (PAI) systems, detects the broadband ultrasound waves generated in tissues due to photoacoustic effect induced by short-pulsed laser excitation. Its sensitivity, frequency and bandwidth largely determine the signal-to-noise ratio (SNR), spatial resolution, and imaging depth of PAI. High-frequency transducer will improve the spatial resolution, but the cost is larger acoustic attenuation and thus lower SNR and smaller imaging depth. Here, we present the design, fabrication, and characterization of a high-density and dual-frequency piezoelectric micromachined ultrasonic transducer (pMUT) array based on thin ceramic PZT, which consists of 128 low-frequency pMUTs and 128 high-frequency pMUTs operating at 1.2 MHz and 3.4 MHz, respectively. By using wafer bonding and chemical mechanical polishing techniques, ceramic PZT with high piezoelectric coefficients was thinned down to only 4 μm and employed as the piezoelectric layer of the designed pMUT array. The dual-frequency performance of the fabricated pMUT array was characterized with electrical impedance, mechanical vibration, and acoustic sensing measurements. With a chip size of 7 mm × 7 mm and integration of 256 pMUTs with both high-frequency and low-frequency into one array, the developed pMUT array shows a great potential for endoscopic photoacoustic imaging to achieve high-resolution and large imaging depth simultaneously.