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Curved Cantilever Actuated ScAlN PMUT for Enhanced Linearity and Transmit Sensitivity
... Most importantly, since both of the signal transmission and reception are conducted by the same PMUT, there is no need to consider the frequency consistency between the transmitting and receiving units, thus largely simplifying the fabrication process control 10 . According to the electromechanical transduction structure design, the PMUT can be roughly categorized into three types, namely fully-closed PMUT 2,11,12 , quasi-closed PMUT [13][14][15][16] and cantilever beam-based PMUT [17][18][19] . Traditional fully-closed PMUT consists of a fully-closed diaphragm anchored to the substrate on all sides, offering advantages such as simple structure, relatively simple fabrication processes, and excellent acoustic sealing. ...
... In contrast, the cantilever structure can effectively release stress through its deformation, making its performance insensitive to fabrication-induced residual stress and thereby easily achieving high fabrication consistency. Moreover, due to the mechanical characteristic of the structure, the cantilever beam-based PMUT exhibits larger linear operation range and higher operation sensitivity 18,19 . As a result, it is highly suitable for high SNR and long distance detection scenario. ...
This paper presents a fully integrated pitch-matched PMUTs-on-CMOS array with high potential in catheter-based ultrasound imaging systems and capabilities to obtain resolutions under 100 μm. The system-on-chip consists of 7x7 AlScN PMUTs connected in a 1-D configuration where the six external rows are used to generate the acoustic pressure through three HV-pulser CMOS circuits, and the central row is used to sense the incoming ultrasound wave which will be amplified by a LNA CMOS amplifier. The experimental verification in a liquid environment gave, as a first result, a peak frequency of 7.7 MHz with a normalized pressure (ST) of 1.98 kPa
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and receiving sensitivity (SR) of 3.3 V/MPa, respectively, competitive sensitivities in comparison with the state-of-the-art. In the second part, ultrasonic imaging for different wires with a minimum diameter of 25 μm was demonstrated as expected from numerical simulations. The system’s performance for ultrasound images was evaluated considering the product of the area and the resolution at 1 mm, giving competitive values compared to other reported ultrasound systems for catheter-based medical ultrasound imaging and the only one providing monolithically integration with the CMOS front-end circuitry.
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.
This paper deals with the design, simulation and characterization of polymer-based piezoelectric micromachined ultrasound transducers (PMUT) (arrays) intended for short-range gesture recognition applications. The presented process flow is fully compatible with existing flat-panel display fabrication. Finite element models were developed for the evaluation of the frequency response, deflection and acoustic pressure output of single PMUT as a function of the membrane diameter. A laser Doppler vibrometer was used to measure the frequency response, membrane velocity and displacement, as well as mode shapes of the microfabricated PMUT in air. An optical microphone was used to measure the pressure emitted by a single PMUT at various distances along the normal axis of the oscillating membrane. A strong correlation between simulations and measurement results is shown. The device geometries most suitable for short-range gesture recognition purposes are selected and the radiation pattern of square arrays is analyzed using simulations. The resonance properties of single PMUT in an array are determined using measurements. An optimized array is used to demonstrate pulse-echo measurements, and the requirements for a simple gesture recognition platform are elucidated.
In this work, a waterproof tent-plate piezoelectric micromachined ultrasonic transducer (PMUT) with enhanced performance as actuator and sensor in comparison with standard clamped PMUT is presented. The squared AlN PMUT has four linear holes that are sealed by the passive layer allowing to increase the movement and giving the capability to work in liquid environment. The dimension of the holes was optimized to increase the PMUT displacement at least twice in relation with the regular clamped device. The acoustic performance of the PMUT was simulated in COMSOL Multiphysics and the results were experimentally verified under liquid operation. The experimental transmitting sensitivity, 3.9 kPa/V, as well as the sensor sensitivity, 13.4 V/MPa, provide a 2x factor improvement in contrast with the clamped PMUT with competitive values. Additionally, the presented tent-plate PMUT provides advantages in relation with the area, cost, power consumption and imaging quality thanks to the capability to be monolithically integrated over CMOS substrates.
An ultrasonic 3D rangefinder uses an array of AlN MEMS transducers and custom readout electronics to localize targets over a ±45° field of view up to 1 m away. The rms position error at 0.5 m range is 0.4 mm, 0.2 °, and 0.8 ° for the range, x-angle, and y-angle axes, respectively. The 0.18 μm CMOS ASIC comprises 10 independent channels with separate high voltage transmitters, readout amplifiers, and switched-capacitor bandpass ΣΔ ADCs with built-in continuous time anti-alias filtering. For a 1 m maximum range, power dissipation is 400 μW at 30 fps. For a 0.3 m maximum range, the power dissipation scales to 5 μW/ch at 10 fps.
Tiltable cantilever-plate based piezoelectric micromachined ultrasonic transducers (pmut) with large linear vibration range and high output power
- Xu
Characterization of polymer-based piezoelectric micromachined ultrasound transducers for short-range gesture recognition applications
- A Gijsenbergh
- Y Halbach
- G B Jeong
- M Torri
- L Billen
- Demi
Tiltable cantilever-plate based piezoelectric micromachined ultrasonic transducers (pmut) with large linear vibration range and high output power
- T Xu
- J Abbaszadeh
- C Bourquard
- A Darie
- M Moridi