Development of Dual-Frequency PMUT Arrays Based on Thin Ceramic PZT for Endoscopic Photoacoustic Imaging

Wang, Haoran; Yang, Hao; Chen, Zhenfang; Zheng, Qincheng; Jiang, Huabei; Feng, Philip X.‐L.; Xie, Huikai

doi:10.1109/jmems.2021.3096733

Cited by 18 publications

(17 citation statements)

References 47 publications

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“…As the measured resonant frequency f r and the anti-resonant frequency f a are known by impedance measurement, the effective electromechanical coupling coefficient of the PMUT can be calculated by: 48 …”

Section: Resultsmentioning

confidence: 99%

Beyond fundamental resonance mode: high-order multi-band ALN PMUT for in vivo photoacoustic imaging

et al. 2022

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This paper reports on an aluminum nitride (AlN) piezoelectric micromachined ultrasound transducer (PMUT) array for photoacoustic (PA) imaging, where the high-order resonance modes of the PMUT are utilized to improve imaging resolution. A flexural vibration mode (FVM) PMUT is fabricated and applied in a photoacoustic imaging (PAI) system. Specifically, the microelectromechanical system (MEMS)-based PMUT is suitable for PA endoscopic imaging of blood vessels and bronchi due to its miniature size and high sensitivity. More importantly, AlN is a nontoxic material, which makes it harmless for biomedical applications. In the PAI system, the AlN PMUT array is used to detect PA signals, and the acousto–mechanical response is designed and optimized at the PMUT’s fundamental resonance. In this work, we focus on the high-order resonance performance of the PMUT PAI beyond the fundamental resonance. The acoustic and electrical responses of the PMUT’s high-order resonance modes are characterized and analyzed. The fundamental and three high-order resonance bandwidths are 2.2, 8.8, 18.5, and 48.2 kHz. Compared with the resolution at the fundamental resonance mode, the resolutions at third- and fourth-order resonance modes increase by 38.7% and 76.9% in a phantom experiment. The high-order resonance modes of the AlN PMUT sensor array provide higher central frequency and wider bandwidth for PA signal detection, which increase the resolution of PAI compared to the PMUT working at the fundamental resonance mode.

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Section: Resultsmentioning

confidence: 99%

Beyond fundamental resonance mode: high-order multi-band ALN PMUT for in vivo photoacoustic imaging

et al. 2022

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“…To match the electrical impedance of the pMUTs and amplify their output signals, a seven-channel preamplifier was designed and fabricated on a printed circuit board (PCB). The preamplifier was designed to have two stages for a 30 dB gain, which consisted of a first-stage charge amplifier and a second-stage voltage amplifier 35 . The fabricated pMUT array was first wire bonded on a dual in-line package, which was then soldered on the PCB, as shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…In previous works, we proposed a 16 × 16 square-shaped dual-frequency pMUT array based on a 4-µm-thick ceramic PZT film operating at 1.2 MHz and 3.4 MHz for endoscopic PAI applications 35 . To increase the SNR and to obtain photoacoustic images with higher resolution and higher contrast, the sensing aperture of pMUT elements and the frequency range of pMUT arrays need to be further increased.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the use of thin ceramic PZT can achieve a lower processing temperature and a wider range of film thicknesses than the use of deposited AlN or PZT thin films, yielding films with lower stresses and facilitating the design of larger pMUTs with high resonance frequencies 39 . Ceramic PZT has been thinned to thicknesses as small as 4–5 µm for fabricating pMUTs and MEMS loud speakers, with excellent performance demonstrated 35 , 40 . To fabricate pMUTs with higher resonant frequencies and larger sensing apertures, the thickness of ceramic PZT is increased to 9 µm in this work.…”

Section: Introductionmentioning

confidence: 99%

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Thin ceramic PZT dual- and multi-frequency pMUT arrays for photoacoustic imaging

et al. 2022

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Miniaturized ultrasonic transducer arrays with multiple frequencies are key components in endoscopic photoacoustic imaging (PAI) systems to achieve high spatial resolution and large imaging depth for biomedical applications. In this article, we report on the development of ceramic thin-film PZT-based dual- and multi-frequency piezoelectric micromachined ultrasonic transducer (pMUT) arrays and the demonstration of their PAI applications. With chips sized 3.5 mm in length or 10 mm in diameter, square and ring-shaped pMUT arrays incorporating as many as 2520 pMUT elements and multiple frequencies ranging from 1 MHz to 8 MHz were developed for endoscopic PAI applications. Thin ceramic PZT with a thickness of 9 μm was obtained by wafer bonding and chemical mechanical polishing (CMP) techniques and employed as the piezoelectric layer of the pMUT arrays, whose piezoelectric constant d31 was measured to be as high as 140 pm/V. Benefiting from this high piezoelectric constant, the fabricated pMUT arrays exhibited high electromechanical coupling coefficients and large vibration displacements. In addition to electrical, mechanical, and acoustic characterization, PAI experiments with pencil leads embedded into an agar phantom were conducted with the fabricated dual- and multi-frequency pMUT arrays. Photoacoustic signals were successfully detected by pMUT elements with different frequencies and used to reconstruct single and fused photoacoustic images, which clearly demonstrated the advantages of using dual- and multi-frequency pMUT arrays to provide comprehensive photoacoustic images with high spatial resolution and large signal-to-noise ratio simultaneously.

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“…PZT-based PMUTs, including niobium-doped PZT (PZNT) PMUTs with high piezoelectric coefficients (−23 C/m 2 ), are used in applications utilizing a low input voltage while attaining high sensitivity [ 28 , 29 ]. Thin PZT ceramic films have also been reported to be used in PMUTs for photoacoustic applications due to their high piezoelectric coefficients [ 30 , 31 ]. Monocrystalline PZT has a high piezoelectric coefficient (14 C/m 2 ) and smaller dielectric constant compared to polycrystalline PZT films and has a higher curie temperature [ 32 ].…”

Section: Piezoelectric Materials and Fabrication Techniques For Pmutmentioning

confidence: 99%

Piezoelectric Micromachined Ultrasonic Transducers (PMUTs): Performance Metrics, Advancements, and Applications

Birjis

Swaminathan

Nazemi

et al. 2022

Sensors

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With the development of technology, systems gravitate towards increasing in their complexity, miniaturization, and level of automation. Amongst these systems, ultrasonic devices have adhered to this trend of advancement. Ultrasonic systems require transducers to generate and sense ultrasonic signals. These transducers heavily impact the system’s performance. Advancements in microelectromechanical systems have led to the development of micromachined ultrasonic transducers (MUTs), which are utilized in miniaturized ultrasound systems. Piezoelectric micromachined ultrasonic transducers (PMUTs) exhibit higher capacitance and lower electrical impedance, which enhances the transducer’s sensitivity by minimizing the effect of parasitic capacitance and facilitating their integration with low-voltage electronics. PMUTs utilize high-yield batch microfabrication with the use of thin piezoelectric films. The deposition of thin piezoelectric material compatible with complementary metal-oxide semiconductors (CMOS) has opened novel avenues for the development of miniaturized compact systems with the same substrate for application and control electronics. PMUTs offer a wide variety of applications, including medical imaging, fingerprint sensing, range-finding, energy harvesting, and intrabody and underwater communication links. This paper reviews the current research and recent advancements on PMUTs and their applications. This paper investigates in detail the important transduction metrics and critical design parameters for high-performance PMUTs. Piezoelectric materials and microfabrication processes utilized to manufacture PMUTs are discussed. Promising PMUT applications and outlook on future advancements are presented.

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Development of Dual-Frequency PMUT Arrays Based on Thin Ceramic PZT for Endoscopic Photoacoustic Imaging

Cited by 18 publications

References 47 publications

Beyond fundamental resonance mode: high-order multi-band ALN PMUT for in vivo photoacoustic imaging

Beyond fundamental resonance mode: high-order multi-band ALN PMUT for in vivo photoacoustic imaging

Thin ceramic PZT dual- and multi-frequency pMUT arrays for photoacoustic imaging

Piezoelectric Micromachined Ultrasonic Transducers (PMUTs): Performance Metrics, Advancements, and Applications

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