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12 pages, 5614 KB

Open AccessArticle

Fabrication and Underwater Testing of a Vector Hydrophone Comprising a Triaxial Piezoelectric Accelerometer and Spherical Hydrophone

by Taehoun Roh, Hong Goo Yeo, Cheeyoung Joh, Yongrae Roh, Kyungseop Kim, Hee-seon Seo and Hongsoo Choi

Sensors 2022, 22(24), 9796; https://doi.org/10.3390/s22249796 - 13 Dec 2022

Cited by 16 | Viewed by 8552

Abstract

A vector hydrophone is an underwater acoustic sensor that can detect the direction of a sound source. Wide-band characteristics and high sensitivity enhance the performance of underwater surveillance systems in complex environments. A vector hydrophone comprising a triaxial piezoelectric accelerometer and spherical hydrophone was fabricated and tested in the air and underwater. The vector hydrophone was designed to exceed the quantitative figures of merit (i.e., receiving voltage sensitivity and bandwidth) of commercially available hydrophones. Accelerometer performance was enhanced by placing a pair of piezoelectric single crystals on each axis and modifying the seismic mass material. The receiving voltage sensitivity of the omnidirectional hydrophone was approximately −160 dB relative to

1 V / μ Pa

with the amplifier in water; the sensitivity of the accelerometer exceeded 300 mV/g in air and −215 dB relative to

1 V / μ Pa

underwater over the frequency range of interest. The receiving directivity of the vector hydrophone was validated underwater, which confirmed that it could detect the direction of a sound source. Full article

(This article belongs to the Special Issue The Development of Piezoelectric Sensors and Actuators)

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11 pages, 4647 KB

Open AccessArticle

Research on a Micro-Processing Technology for Fabricating Complex Structures in Single-Crystal Quartz

by Chao Han, Cun Li, Yulong Zhao, Bo Li and Xueyong Wei

Micromachines 2020, 11(3), 337; https://doi.org/10.3390/mi11030337 - 24 Mar 2020

Cited by 11 | Viewed by 5019

Abstract

Single-crystal quartz material is widely applied in the manufacture of resonators and sensors, but it is difficult to process because of its high hardness. A novel way to fabricate single-crystal quartz structures is proposed in this paper; the method includes quartz-on-silicon (QoS) technology and inductively coupled plasma (ICP) etching, which makes it feasible to fabricate complex structures with crystal quartz. The QoS method encompasses the bonding of silicon and quartz, followed by the thinning and polishing of quartz, which can enable the fabrication of an ultra-thin quartz wafer on silicon. In this way, instead of the conventional wet etching with hydrofluoric acid, the quartz layer can be easily etched using the ICP dry-etching method. Then, the structure of the pure quartz material is obtained by removing the silicon wafer. In addition, the silicon layer can be processed into the appropriate structure. This aspect overcomes the difficulty of processing a complex structure of single-crystal quartz with different crystal orientations. Thin single-crystal quartz wafers of Z-cut with a thickness of less than 40 μm were obtained by using this method, and a complex three-dimensional structure with an 80 μm width was also acquired by the ICP etching of the quartz wafer. The method can be applied to make both crystal-oriented quartz-based sensors and actuators, such as quartz resonant accelerometers. Full article

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13 pages, 4256 KB

Open AccessArticle

The Design and Optimization of a Compressive-Type Vector Sensor Utilizing a PMN-28PT Piezoelectric Single-Crystal

by Hong Goo Yeo, Junhee Choi, Changzhu Jin, Seonghun Pyo, Yongrae Roh and Hongsoo Choi

Sensors 2019, 19(23), 5155; https://doi.org/10.3390/s19235155 - 25 Nov 2019

Cited by 8 | Viewed by 5919

Abstract

Underwater sensors that detect the distance and direction of acoustic sources are critical for surveillance monitoring and target detection in the water. Here, we propose an axial vector sensor that utilizes a small (~1 cm³) compressive-type piezoelectric accelerometer using piezoelectric single crystals. Initially, finite element analysis (FEA) was used to optimize the structure that comprised piezoelectric Pb(Mb_1/3Nb_2/3)O₃-28%PbTiO₃ single crystals on a tungsten seismic mass. The receiving voltage sensitivity (RVS) was enhanced through geometric optimization of the thickness and sensing area of the piezoelectric material and the seismic mass. The estimated maximum RVS of the optimized vector sensor was −212 dB. FEA simulations and practical measurements were used to verify the directivity of the vector sensor design, which exhibited a dipole pattern. The dipole beam pattern was used to obtain cardioid patterns using the simulated and measured results for comparison. The results clearly showed the feasibility of using the proposed piezoelectric single-crystal accelerometer for a compressive-type vector sensor. Full article

(This article belongs to the Special Issue Development of Piezoelectric Sensors and Actuators)

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14 pages, 8086 KB

Open AccessArticle

Design of a Piezoelectric Accelerometer with High Sensitivity and Low Transverse Effect

by Bian Tian, Hanyue Liu, Ning Yang, Yulong Zhao and Zhuangde Jiang

Sensors 2016, 16(10), 1587; https://doi.org/10.3390/s16101587 - 26 Sep 2016

Cited by 66 | Viewed by 11572

Abstract

In order to meet the requirements of cable fault detection, a new structure of piezoelectric accelerometer was designed and analyzed in detail. The structure was composed of a seismic mass, two sensitive beams, and two added beams. Then, simulations including the maximum stress, natural frequency, and output voltage were carried out. Moreover, comparisons with traditional structures of piezoelectric accelerometer were made. To verify which vibration mode is the dominant one on the acceleration and the space between the mass and glass, mode analysis and deflection analysis were carried out. Fabricated on an n-type single crystal silicon wafer, the sensor chips were wire-bonged to printed circuit boards (PCBs) and simply packaged for experiments. Finally, a vibration test was conducted. The results show that the proposed piezoelectric accelerometer has high sensitivity, low resonance frequency, and low transverse effect. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2016)

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11 pages, 2222 KB

Open AccessArticle

A Wafer Level Vacuum Encapsulated Capacitive Accelerometer Fabricated in an Unmodified Commercial MEMS Process

by Adel Merdassi, Peng Yang and Vamsy P. Chodavarapu

Sensors 2015, 15(4), 7349-7359; https://doi.org/10.3390/s150407349 - 25 Mar 2015

Cited by 19 | Viewed by 9594

Abstract

We present the design and fabrication of a single axis low noise accelerometer in an unmodified commercial MicroElectroMechanical Systems (MEMS) process. The new microfabrication process, MEMS Integrated Design for Inertial Sensors (MIDIS), introduced by Teledyne DALSA Inc. allows wafer level vacuum encapsulation at 10 milliTorr which provides a high Quality factor and reduces noise interference on the MEMS sensor devices. The MIDIS process is based on high aspect ratio bulk micromachining of single-crystal silicon layer that is vacuum encapsulated between two other silicon handle wafers. The process includes sealed Through Silicon Vias (TSVs) for compact design and flip-chip integration with signal processing circuits. The proposed accelerometer design is sensitive to single-axis in-plane acceleration and uses a differential capacitance measurement. Over ±1 g measurement range, the measured sensitivity was 1fF/g. The accelerometer system was designed to provide a detection resolution of 33 milli-g over the operational range of ±100 g. Full article

(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering)

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26 pages, 2573 KB

Open AccessReview

High-Temperature Piezoelectric Sensing

by Xiaoning Jiang, Kyungrim Kim, Shujun Zhang, Joseph Johnson and Giovanni Salazar

Sensors 2014, 14(1), 144-169; https://doi.org/10.3390/s140100144 - 20 Dec 2013

Cited by 393 | Viewed by 29681

Abstract

Piezoelectric sensing is of increasing interest for high-temperature applications in aerospace, automotive, power plants and material processing due to its low cost, compact sensor size and simple signal conditioning, in comparison with other high-temperature sensing techniques. This paper presented an overview of high-temperature piezoelectric sensing techniques. Firstly, different types of high-temperature piezoelectric single crystals, electrode materials, and their pros and cons are discussed. Secondly, recent work on high-temperature piezoelectric sensors including accelerometer, surface acoustic wave sensor, ultrasound transducer, acoustic emission sensor, gas sensor, and pressure sensor for temperatures up to 1,250 °C were reviewed. Finally, discussions of existing challenges and future work for high-temperature piezoelectric sensing are presented. Full article

(This article belongs to the Special Issue Sensors for Harsh-Environment Applications)

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16 pages, 2032 KB

Open AccessArticle

A Low-Cost CMOS-MEMS Piezoresistive Accelerometer with Large Proof Mass

by Mohd Haris Md Khir, Peng Qu and Hongwei Qu

Sensors 2011, 11(8), 7892-7907; https://doi.org/10.3390/s110807892 - 11 Aug 2011

Cited by 44 | Viewed by 14403

Abstract

This paper reports a low-cost, high-sensitivity CMOS-MEMS piezoresistive accelerometer with large proof mass. In the device fabricated using ON Semiconductor 0.5 μm CMOS technology, an inherent CMOS polysilicon thin film is utilized as the piezoresistive sensing material. A full Wheatstone bridge was constructed through easy wiring allowed by the three metal layers in the 0.5 μm CMOS technology. The device fabrication process consisted of a standard CMOS process for sensor configuration, and a deep reactive ion etching (DRIE) based post-CMOS microfabrication for MEMS structure release. A bulk single-crystal silicon (SCS) substrate is included in the proof mass to increase sensor sensitivity. In device design and analysis, the self heating of the polysilicon piezoresistors and its effect to the sensor performance is also discussed. With a low operating power of 1.5 mW, the accelerometer demonstrates a sensitivity of 0.077 mV/g prior to any amplification. Dynamic tests have been conducted with a high-end commercial calibrating accelerometer as reference. Full article

(This article belongs to the Section Physical Sensors)

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