Zhiyuan Shen

Flexible and Surface-Mountable Piezoelectric Sensor Arrays for Underwater Sensing in Marine Vehicles

In an effort to improve the situational awareness and obstacle avoidance of marine vehicles, we fabricate, package and characterize Pb (Zr0.52Ti0.48)O3 thin-film piezoelectric pressure sensor arrays for passive fish-like underwater sensing. We use floating bottom electrode in designing the sensor which made the sensor able to detect very low frequency range (down to 0.1 Hz) in water. The proposed array of sensors is capable of locating underwater objects by transducing the pressure variations generated by the stimulus. The sensors are packaged into an array of 2 × 5 on a flexible liquid crystal polymer substrate patterned with gold interconnects. Experiments in this paper are divided into three main categories. First, in order to evaluate the effect of water on the sensor performance, resonant frequency, and quality factor changes in air and water are investigated theoretically and experimentally. Second, the ability of the array in locating a vibrating sphere (dipole) in water is illustrated through experiments. The sensors demonstrate a high resolution of 3 mms-1 in detecting in detecting oscillatory flow velocity in water. Third, “real-time” experiments are conducted in a swimming pool environment by surface mounting two arrays of sensors on the curved hull of a kayak vehicle. The arrays are self-powered and do not need any external power supply, to operate, which greatly benefits in eliminating the need of bulky power supplies on underwater vehicles.

Medium damping influences on the resonant frequency and quality factor of piezoelectric circular microdiaphragm sensors

Medium damping influences on the resonant frequency and quality factor of piezoelectric circular microdiaphragm sensors (PCMSs) are investigated theoretically and experimentally in this paper. The acoustic radiation and viscosity damping as the two main sources of energy dissipation in a medium virtually added the mass of the diaphragm and therefore decrease the frequency and Q-factor of the diaphragm. The magnitude of medium damping inversely depends on the radius-to-thickness ratio. An increase in this ratio is the trend in the fabrication of thin microdiaphragms by MEMS fabrication processes, which implies the higher influence of medium damping on the dynamic behavior of microdiaphragms. The fabricated PCMSs were tested in vacuum, air, and ethanol. The Q-factor and the resonant frequency of the device increase by almost seven times, 4.7% from air to 0.05 atmpressure, respectively. The Q-value drops from 111.195 in air to 23.908 in ethanol. Throughout this work, theoretical and experimental values were compared and a fairly good correlation was observed.

Flexible, zero powered, piezoelectric MEMS pressure sensor arrays for fish-like passive underwater sensing in marine vehicles

In an effort to improve the situational awareness of maritime vehicles, flexible MEMS pressure sensor arrays are developed for underwater sensing applications. This paper outlines the development of piezoelectric microdiaphragm pressure sensor arrays that can perform a passive fish-like underwater sensing. Individual sensors have a low footprint of 1.8 × 1.8 mm2 and do not require any power for their operation. An array of 2 by 5 sensors is fabricated, packaged and tested for use on marine vehicle. The proposed array is capable of locating underwater objects by transducing the pressure variations generated by the stimulus.

Displacement and resonance behaviors of a piezoelectric diaphragm driven by a double-sided spiral electrode

This paper presents the design of a lead zirconate titanate (PZT) diaphragm actuated by double-sided patterned electrodes. Au/Cr electrodes were deposited on bulk PZT wafers by sputtering while patterned by a lift-off process. SU-8 thick film was used to form the structural layer. Double-spiral electrode induced in-plane poling and piezoelectric elongation are converted to an out-of-plane displacement due to the confined boundary condition. The influence of different drive configurations and electrode parameters on deflection has been calculated by finite element methods (FEM) using a uniform field model. Impedance and quasi-static displacement spectra of the diaphragm were measured after poling. A double-sided patterned electrode diaphragm can be actuated by more drive configurations than a single-sided one. Compared with a single-sided electrode drive, a double-sided out-of-phase drive configuration increases the coupling coefficient of the fundamental resonance from 7.6% to 11.8%. The displacement response of the diaphragm increases from 2.6 to 8.6 nm V 1 . Configurations including the electric field component perpendicular to the poling direction can stimulate shear modes of the diaphragm. (Some figures may appear in colour only in the online journal)

Spiral electrode d33 mode piezoelectric diaphragm combined with proof mass as energy harvester

The paper demonstrates an energy harvester using a freestanding piezoelectric diaphragm combined with a proof mass. The diaphragm bearing double-sided spiral electrodes makes use of the d33 piezoelectric effect to realize energy scavenging. The harvester was fabricated by using a MEMS technique. The energy converting performance of the diaphragm was characterized by a shaker system. Proof masses were combined at the center of the diaphragm to tune the resonance of the harvester for the sake of scavenging low frequency vibrational energy. A receptance model was built to explain the vibrational behavior of the combined system. The resonance tuning and energy harvesting performance of the combination system was experimentally verified.

Proof mass effects on spiral electrode d 33 mode piezoelectric diaphragm-based energy harvester

This paper presents the characterization of an energy harvester using a piezoelectric diaphragm as the vibration energy conversion microstructure. The diaphragm containing the spiral electrode operates in the d33 mode. The energy harvesting performance of the diaphragm was characterized. The optimal resistance load and the working frequency were characterized. The resonance tuning and the energy harvesting enhancement due to a proof mass were verified.

Direct-Write Piezoelectric Ultrasonic Transducers for Non-Destructive Testing of Metal Plates

Current real time structural health monitoring is implemented by assembling multiple discrete sensors on a structure with each sensor providing only point measurement. The installation of the multiple sensors results in high global cost and low reliability. This paper reports the design, direct-write fabrication, and testing of ultrasonic transducers on a plate structure and a non-destructive testing method for detecting defects using the sensor array comprising the direct-write ultrasonic transducers. The transducers are made of piezoelectric poly(vinylidenefluoride/trifluoroethylene) (P(VDF/TrFE)) polymer coatings that are aerosol-spray deposited and patterned directly on the plate structure to be monitored. The ultrasonic transducers bearing annular array comb electrodes are designed for generating and selectively detecting fundamental antisymmetric Lamb-mode ultrasonic waves in the plate structure. The ultrasonic transducers can serve as both the actuators to generate ultrasonic waves and the sensors to detect ultrasonic waves. The ultrasonic waves propagating through the plate structure contain the information about the structural integrity. With copper bars of different thicknesses introduced at the plate center as mock defects of different severity, the correlation between the transducer response and the defect thickness and hence, the severity is verified. It is also demonstrated that four ultrasonic transducers located at the square plate (100 mm

Piezoelectric sensor array for passive fish-like underwater sensing

\times 100

Polymer MEMS sensor for flow monitoring in biomedical device applications

mm

Biomimetic flow sensors for biomedical flow sensing in intravenous tubes

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