A two-port piezoelectric micromachined ultrasonic transducer

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133

In recent decades, micromachined ultrasonic transducers (MUTs) have been investigated as an alternative to conventional piezocomposite ultrasonic transducers, primarily due to the advantages that microelectromechanical systems provide. Miniaturized ultrasonic systems require ultrasonic transducers integrated with complementary metal-oxide-semiconductor circuits. Hence, piezoelectric MUTs (pMUTs) and capacitive MUTs (cMUTs) have been developed as the most favorable solutions. This paper reviews the basic equations to understand the characteristics of thin-film-based piezoelectric devices and presents recent research on pMUTs, including current approaches and limitations. Methods to improve the coupling coefficient of pMUTs are also investigated, such as device structure, materials, and fabrication techniques. The device structure improvements include multielectrode pMUTs, partially clamped boundary conditions, and 3D pMUTs (curved and domed types), where the latter can provide an electromechanical coupling coefficient of up to 45%. The piezoelectric coefficient (e31) can be increased by controlling the crystal texture (seed layer of γ-Al2O3), using single-crystal (PMN-PT) materials, or control of residual stresses (using SiO2 layer). Arrays of pMUTs can be implemented for various applications including intravascular ultrasound, fingerprint sensors, rangefinders in air, and wireless power supply systems. pMUTs are expected to be an ideal solution for applications such as mobile biometric security (fingerprint sensors) and rangefinders due to their superior power efficiency and compact size.

Section: Multi-electrode Pmutmentioning

confidence: 99%

Review of piezoelectric micromachined ultrasonic transducers and their applications

Jung

Lee

Kang

et al. 2017

238

133

“…Currently, most clinical ultrasonic probes are based on traditional ultrasonic transducers (UTs) that usually consist of Lead zirconate titanate (PZT) strips poled in the thickness direction [9]. Although it is the most mature form in the market, there are some drawbacks such as complex manufacturing process [9][10][11], large mismatch of impedance [12,13], poor thermal stability, and difficulty in realizing highdensity arrays [14], thus cannot meet the demand for portable/wearable medical devices [15,16]. Benefiting from the development of microelectromechanical systems, micromachined UTs (MUTs) are proposed to address this issue due to their good acoustic impedance matching, broad bandwidth, low cost and easy integration with supporting electronics compared with traditional bulky ultrasound transducer [17].…”

Section: Introductionmentioning

confidence: 99%

Imaging of simulated muscle based on single chip of AlN piezoelectric micromachined ultrasonic transducer

Qu¹,

Ding²,

Li³

et al. 2022

Most of current portable B-mode medical imaging is based on traditional ultrasonic transducers (UTs) or capacitive micromachined ultrasonic transducers (cMUTs), both of them have defects that impede satisfying performance. Piezoelectric micromachined ultrasonic transducers (pMUTs) is a promising solution for portable/wearable B-mode imaging as alternative. This work demonstrates B-mode imaging of simulated muscle with an aluminum nitride (AlN) pMUT array for application of muscle disorder diagnosis. A 23×26 pMUT array with resonant frequency of 5 MHz (in oil) is fabricated based on cavity silicon on- -insulator (SOI) process. It has transmitting sensitivity of 3.6 kPa/V at 10 mm, receiving sensitivity of 1.1 μV/Pa and -6 dB bandwidth of 40% (in oil). Feasibility of muscle imaging based on pMUT is demonstrated by using muscle-like phantoms. Imaging results shows clear interfaces among layers, the axial and lateral resolution is 0.25 mm and 1.23 mm respectively. Furthermore, ex-vivo Bmode scans towards porcine tissues based on pMUT are firstly demonstrated. Different tissues including muscle, subcutaneous fat, fascia and hematoma is distinguished. The maximum imaging depth inside the porcine tissue is above 40 mm. These results demonstrate great potential of the pMUT array in muscle imaging.

“…The sensitivity and electromechanical coupling factor can be largely enhanced for PMUTs with multi-electrodes using a differential scheme [21]. A two-port PMUTs device consisting of inner and outer electrodes has been disclosed [22]. It is driven differentially, which roughly provides twice the electromechanical coupling factor and shows enhanced acoustic power output.…”

Section: Introductionmentioning

confidence: 99%

Performance of aluminum nitride-based piezoelectric micromachined ultrasonic transducers under different readout configurations

Shi

Jia

Liu

et al. 2021

In this paper, a low noise amplification circuit is designed for aluminum nitride-based piezoelectric micromachined ultrasonic transducers (PMUTs) with three different sensing configurations. The acoustic pressure sensitivity and noise resolution of PMUTs corresponding to different readout configurations are analyzed and characterized. With the differential readout configuration, the acoustic pressure sensitivity of the PMUTs is improved by 5.76 dB (re: 1 V µPa−1) on average, and the noise resolution is reduced by about 8 dB at 500 Hz (re: 1 µPa (Hz 1 / 2 )−1). Compared to the conventional readout configuration, both theoretical analysis and measurement results show that the output voltage of PMUTs is doubled with the differential readout configuration and thus the acoustic pressure sensitivity is improved. Moreover, the noise resolution of PMUTs is reduced and thus the signal-to-noise is improved. This work offers new insight on improving the receiving performance of PMUTs.