Piezoelectric Disk Research Articles

Programmable topological insulators based on a reconfigurable electroacoustic material platform

Topological insulators (TIs), exhibiting topologically protected edge and interface waves, have recently emerged in phononic systems. Reconfigurabilty is essential for enabling TI-based applications. One potential means for achieving reconfigurability employs shunted piezoelectric (PZT) disks in which a unit cell’s mechanical impedance is altered using negative capacitance circuits. Dynamic reconfigurability and programmability of such material platforms can then be obtained through simple on/off switching. In this vein, we propose and experimentally verify an electroacoustic TI which exhibits programmable topologically protected edge states useful for acoustic multiplexers, demultiplexers, and transistors. This reconfigurable structure is composed of an elastic hexagonal lattice whose unit cell contains two shunted PZT disks, each connected to a negative capacitance circuit by an on/off switch. Closing one or the other circuit results in the breaking of mirror symmetry and yields mechanical behavior analogous to the quantum valley Hall effect. By interfacing two topologically distinct materials, a domain wall is introduced exhibiting a localized interface state topologically protected from backscattering at defects and sharp edges. Through the use of programmable time-division, in which domain walls appear and disappear in time, we demonstrate multiplexing and demultiplexing. We also demonstrate an acoustic transistor using the same programmable platform, before closing with a discussion on future research directions.

Design, Testing, Evaluation, and Implementation of an Arduino-based Mosquito-Repellent System

Aims: The primary objective of this research drive is to design, develop, and evaluate an Arduino-based mosquito-repellent system. This work underscores the importance of developing sustainable and eco-friendly solutions for mosquito control.
 Study Design: An Arduino microcontroller board is used, and an assembly language program is developed to repel mosquitoes from the surroundings. This system uses piezoelectric disks, LED lights, LCD monitor along with the Arduino board and produces ultrasonic sound to protect humans and the environment from mosquitoes.
 Place and Duration of Study: The research effort was steered by the authors in a group under the supervisor of a faculty member as a part of the course capstone project work of the Bachelor of Science in Engineering degree in Computer Science and Engineering at the American International University Bangladesh (AIUB), Dhaka, Bangladesh. The authors performed their research tasks at AIUB from May 2023 to January 2024.
 Methodology: The innovative mosquito-repellent system uses an Arduino Mega 2560 microcontroller to generate a cutting-edge solution to tackle the problem of mosquito infestations. The system can produce an electric signal that can emit mechanical ultrasound signals to be harnessed using a series-connected eight piezo-electric discs. To power up the system, it uses four Li-ion rechargeable batteries charged by using solar energy from the home solar system. Besides, it uses LEDs to indicate the status of the repellent system.
 Results: The generated ultrasonic signal is observed on the oscilloscope screen and its’ value is exhibited on the LCD screen to evaluate the system performance. Testing confirms that the system can drive away mosquitoes within its 3 m surroundings in 2-3 minutes. Besides, the system parameter and cost comparison show that this scheme suggests a worthwhile and sustainable result for making a mosquito-free environment.
 Conclusion: The development of a mosquito-repellent system using ultrasonic sound waves based on an Arduino microcontroller offers a sustainable and effective alternative to traditional methods of mosquito control. Since the system is chemical and health-hazard-free, it is eco-friendly and makes human life more comfortable. The system is portable and cost-effective, making it suitable for use in various settings.

Flow analysis for lateral synthetic jets to remove contaminants from the outer surface of an automobile camera module

A test facility was constructed to investigate the flow characteristics of lateral synthetic jets generated by an actuator composed of a cavity, an orifice and a vibrating piezoelectric disc. Subsequently, 3D unsteady numerical simulations were conducted to analyze the formation of the synthetic jets and their dependence on the height of the orifice exit from the outer surface of the cavity. The time-averaged axial velocity was measured and used to validate the numerical results, and the maximum velocity reached approximately 8 m/s. In this work, it was found that the interaction of the vortex tube generated at the edge of the orifice exit and the outer surface of the cavity has a significant impact on the axial velocity distribution and characteristics of the lateral synthetic jets. Based on the experimental data and the numerical results, an attempt has been made to understand the formation of the synthetic jets and their interaction with the outer surface.

A wavefront track approach to defect detection in composites by scanning laser Doppler vibrometry

Composite laminates are becoming increasingly popular in a large variety of applications due to their favourable mechanical properties. However, laminates production processes can lead to various defects in the final material. The most common type is related to thickness variations, e.g. delaminations between layers, which can compromise the mechanical strength of the structure. Therefore, there is a great interest in developing non-destructive and non-contact quality control techniques for composite material assessment to minimize process costs. An interesting approach is the use of laser Doppler vibrometry combined with signal analysis based on Lamb waves propagation. In this work, we used an impulsive force given by a piezoelectric disk to the specimen and a laser Doppler vibrometer acquiring the points velocity over time along a scanning grid on the surface. The specimen is a fiberglass reinforced flat panel with seven different orientated layers which presents a delamination of about 22 mm. The maximum thickness-frequency product achieved in this analysis has been 0.2 MHz∙mm. In contrast to state-of-the-art methods for identifying thickness variation based on local estimation of the principal wave number, the proposed algorithm makes use of a tracking filter of the wave front of the propagating A0 mode waves, returning a final image in polar coordinates. The final information given by the algorithm provides the position of the delamination and, hence, can be used as a pass/failure test. State-of-the-art methods are also able to identify the shape of the defect but pay the price of a higher computational cost by using at least 4D matrix processing unlike our method which only uses 3D matrices.

Performance study of an energy harvester with multiple piezoelectric disks in parallel connection for water pressure pulsation

Water hydraulic pump is a crucial component of the water hydraulic system, and it generates periodic pressure pulsation due to its inherent characteristics. To harvest the vibration energy from the pressure pulsation, an energy harvester with multiple piezoelectric disks in parallel connection is proposed. Two prototypes are fabricated to analyze the effect of the number of piezoelectric disks on the energy harvesting characteristics under different pressures and resistances. Parameter matching is also carried out to obtain high root mean square (RMS) voltage and average power. For both prototypes, the cyclical change of deformation is caused by the pressure pulsation, leading to transient variation of voltage. Moderate thickness of piezoelectric ceramic and small thickness of copper substrate are advantageous for generating higher electrical energy output. Pressure pulsation significantly affects the harvested voltage and power, with the main influencing factor being the pulsation amplitude rather than static pressure. Additionally, transient voltage and RMS voltage increase with increasing resistance, while average power first rises and then falls. Comparing the two prototypes, both voltage and optimal resistance decrease when the number of piezoelectric disks in parallel connection increases. The average power and power density with two piezoelectric disks can reach 447 μW and 4.56 mW cm−3 under 3 MPa and at a resistance of 20 KΩ. This research provides guidance for the design, optimization and application of piezoelectric energy harvesters in water hydraulic system.

Higher-order shear deformation theory for accurate prediction of vibration behavior of thick piezoelectric disks and design of efficient surface electrodes

A modified higher-order shear deformation plate theory (MHSDT) is proposed to predict the resonance frequencies and related mode shapes of piezoelectric disks of various thicknesses. The theory explicitly accounts for the effects of the electrical potential on the displacement of the disk. The equations of motion for the disk are derived using Hamilton's principle in conjunction with a variational approach. It is shown analytically that the distribution of the electrical field on the surface of the disk is quantitatively similar to the distribution of the sum of the total stresses within the disk. Thus, the deformation of the disk can be approximated directly from the stress distribution on the disk, thereby greatly simplifying the solution process. The validity of the proposed MHSDT is confirmed by comparing the solutions for the natural frequencies, displacement fields, and electric field distributions of the disk for various radius-to-thickness ratios and boundary conditions with those obtained using Reddy’s third-order plate theory and COMSOL finite element simulations, respectively. The results show that the solutions obtained from the MHSDT method are consistently closer to the exact solutions than those determined using Reddy’s third-order method. Finally, the linear relationship between the electric field and the flexural displacement of the disk is leveraged to design surface electrodes capable of exciting specific flexural mode shapes of the disk under a free boundary condition. The efficiency of the designed electrodes is experimentally demonstrated using an amplitude-fluctuation electronic speckle pattern interferometer (AF-ESPI).

Generation of time-independent torque by ultrasonic guided waves

The excitation of acoustic waves by a unidirectional transducer, integrated in a piezoelectric cylindrical tube or disk, can lead to a time-independent torque. This phenomenon, demonstrated earlier in experiments and analyzed with coupling-of mode theory, is explained in detail, starting on the level of lattice dynamics of a piezoelectric crystal. Expressions are derived for the stationary torque in the form of integrals over the volume or surface of the piezoelectric, involving the electric potential and displacement field associated with the acoustic waves generated by the transducer.Simulations have been carried out with the help of the finite element method for a tube made of PZT for two cases: A pre-defined potential on the surface of the tube and metal electrodes buried in the piezoelectric. The displacement field and electric potential of the high-frequency acoustic waves (between 200 and 300 kHz) were computed and used in the evaluation of the integrals. The attenuation due to various loss channels of the acoustic waves in the system has been analyzed in detail, as this plays a crucial role for the efficiency of torque generation. It is conjectured that time-reversal symmetry, present in the absence of attenuation, prohibits the generation of a static torque at least in the linear limit.A qualitative comparison is made between the simulations and earlier experiments. Discrepancies are attributed to lack of knowledge of the relevant material constants of the piezoelectric and to a simplified modeling of the electrode geometry in the cylindrical tube, which was necessary for reasons of numerical accuracy.

A 3D-Printed Piezoelectric Microdevice for Human Energy Harvesting for Wearable Biosensors.

The human body is a source of multiple types of energy, such as mechanical, thermal and biochemical, which can be scavenged through appropriate technological means. Mechanical vibrations originating from contraction and expansion of the radial artery represent a reliable source of displacement to be picked up and exploited by a harvester. The continuous monitoring of physiological biomarkers is an essential part of the timely and accurate diagnosis of a disease with subsequent medical treatment, and wearable biosensors are increasingly utilized for biomedical data acquisition of important biomarkers. However, they rely on batteries and their replacement introduces a discontinuity in measured signals, which could be critical for the patients and also causes discomfort. In the present work, the research into a novel 3D-printed wearable energy harvesting platform for scavenging energy from arterial pulsations via a piezoelectric material is described. An elastic thermoplastic polyurethane (TPU) film, which forms an air chamber between the skin and the piezoelectric disc electrode, was introduced to provide better adsorption to the skin, prevent damage to the piezoelectric disc and electrically isolate components in the platform from the human body. Computational fluid dynamics in the framework of COMSOL Multiphysics 6.1 software was employed to perform a series of coupled time-varying simulations of the interaction among a number of associated physical phenomena. The mathematical model of the harvester was investigated computationally, and quantification of the output energy and power parameters was used for comparisons. A prototype wearable platform enclosure was designed and manufactured using fused filament fabrication (FFF). The influence of the piezoelectric disc material and its diameter on the electrical output were studied and various geometrical parameters of the enclosure and the TPU film were optimized based on theoretical and empirical data. Physiological data, such as interdependency between the harvester skin fit and voltage output, were obtained.

Scrap-Based Smoke Detection Bulb Powered by Energy-Harvesting Mat (SSDPEM): An Arduino Uno Based Back-Up Led Bulb With M-Q2 Smoke Sensor and Piezoelectric Discs

Scrap-Based Smoke Detection Bulb Powered by Energy-Harvesting Mat (SSDPEM): An Arduino Uno Based Back-Up Led Bulb With M-Q2 Smoke Sensor and Piezoelectric Discs

Thin-film sensors for data-driven concentricity prediction in cup backward extrusion

The manufacture of precise metal components by cold forging poses serious challenges to the process reliability under unstable process conditions. The detection of geometrical imperfections, such as concentricity deviations, is necessary for the operator to adjust the forging tool rack properly. In this paper, a novel piezoelectric thin-film sensor disc is introduced to detect such concentricity deviations based on the measurement of eccentric load, that is arising from elastic punch deformation. Experimental results showed, that the concentricity deviation of the produced parts efficiently can be predicted by processing measured force data using a support vector regression algorithm.

Research on low-frequency bender disk transducer driven by multiple relaxor ferroelectric single crystal disks

In this paper, we investigate the low-frequency bender disk transducer designed by the relaxor ferroelectric single crystal. First, we introduce the principle of the bender disk transducer, and use multiple single crystal disks as driving materials to excite the bending vibration mode of the metal plate, which reduces the operating frequency of the transducer. Then we establish the three-dimensional finite element model of the bender disk transducer driven by multiple single crystal disks, analyze the influence of the number and position distribution of single crystal disks on the transducer performance, and compare with that of the piezoelectric ceramic transducer with the same structure. Finally, we manufacture the proposed relaxor ferroelectric single crystal, piezoelectric ceramic transducers and the conventional piezoelectric ceramic bender disk transducer respectively, and carry out the experimental measurement in an anechoic water tank. The experimental results show that for the proposed single crystal transducer, its measured maximum transmitting voltage response (TVR) is 126.2 dB at 1.1 kHz, which is 13.4 dB higher than that of the proposed piezoelectric ceramic transducer, and its frequency corresponding to the maximum TVR is reduced by 700 Hz compared with the conventional piezoelectric ceramic bender disk transducer.

Influence of input voltage on the structural and fluid flow characteristics and proposed working condition of a micro-blower

Several methods are explored for the thermal management of highly packed electronic systems. A forced convection setup called micro-blower is an effective solution for the application of heat removal and it consists of a piezoelectric disc (PED), diaphragm, ring and a top plate. A numerical model is developed to study the influence of input voltage on the micro-blower using COMSOL Multiphysics. The size of the micro-blower selected is 20 × 20 × 3 mm3. Structural characteristics such as Eigen frequency, diaphragm displacement and von Mises stress and output characteristic such as velocity at the nozzle exit, the volumetric flow rate of air, density variation in the fluid domain and pressure gradient of air at the nozzle for various voltage inputs (peak-to-peak voltage, Vp-p) from 5 to 20 V were estimated. The diaphragm displacement of the blower was estimated with various input voltages. An average nozzle velocity of 21.21 m/s was achieved with an average volumetric flow rate of 10.66 × 10−6 m3/s for the voltage input of 20 Vp-p. The von Mises stresses of PED, diaphragm, ring and top plate were 3.38, 6.38, 15.72 and 88.97 MPa and these were within the maximum yield strength of respective components at 20 V and hence the micro-blower design is safe. The proposed Eigen frequency in the ultrasonic range was 21.298 kHz and the proposed input voltage as per the breakdown voltage was 20 V. The results were compared with existing literature data and found promising agreement.

Design and experiment of a double-sided staggered conical teeth traveling wave ultrasonic motor

This paper proposed a double-sided staggered conical teeth traveling wave rotating ultrasonic motor based on in-plane bending mode, which reduces the difficulty of rotor preload application and improves the output characteristics of in-plane bending mode traveling wave rotating ultrasonic motor. The motor has four sets of drive teeth alternately distributed on both the inner and outer sides of the vibrator, with the drive teeth gap dedicated to accommodate the piezoelectric ceramic piece, and the staggered drive teeth on both sides of the vibrator are used to drive the rotor rotation. The motor operates in two in-plane third-order bending modes with the same frequency and orthogonal to each other, and is excited by four sets of piezoelectric ceramic disks spaced 90 degrees apart from the inner and outer sides. After the prototype was completed, its vibration characteristics and output performance were experimentally tested, and the actual effects of the three excitation schemes were compared. The experimental results show that the motor can provide a maximum output torque of 1.82 N·mm and a maximum no-load speed of 96.4 rpm when the excitation voltage is 300 V and the excitation frequency is 20.60 kHz.

Finite element-based diffraction correction for piezoelectric transducers accounting for diffraction at transmission, propagation, and reception.

Existing diffraction correction models for ultrasonic transmit-receive measurement systems rely on simplifying assumptions with respect to the boundary conditions at the transmitter or receiver. Common simplifications include approximating the sound field radiated by a piezoelectric transducer using a baffled piston model and assuming that the receiver's electrical response is proportional to the spatially averaged free-field pressure over its front surface. In many applications, such simplifications may be adequate, but their validity and accuracy need to be evaluated and quantified. Here, a diffraction correction model utilizing the full set of electrical and mechanical boundary conditions at the transmitter and receiver is presented, avoiding these simplifications. The model is based on finite element modeling of coaxially aligned piezoelectric transducers in a fluid medium. Comparison is made with existing models for an example case of cylindrical piezoelectric ceramic disk transducers operating in air at 50-300 kHz and 0.03-2 m apart, relevant for, e.g., sound velocity and absorption measurements in fluids and ultrasonic gas flow metering. In the near-field, errors introduced by the simplifications are up to 3 dB and 47° for the first radial resonance. Generally, such errors are application-specific and depend on distance, frequency, transducer construction, vibration pattern, and medium properties.

Piezoelectric Energy Harvester for Harnessing Rotational Kinetic Energy through Linear Energy Conversion

Real-time condition monitoring of various types of machinery using sensor technology has gained significant importance in recent years. However, relying on batteries to power these sensors proves to be sub-optimal, as it necessitates regular charging or replacement. To address this, harvesting waste energy from ambient sources emerges as a more efficient alternative. Everyday applications like vehicle wheels, fans, and turbines present ambient sources of waste rotational energy. In this study, we propose a novel rotational energy harvester design that converts rotational energy into linear energy. This linear energy impacts a piezoelectric disk, generating an electric potential. Through simulations, the expected electric potential at varying frequencies was evaluated. Subsequently, experimental tests were conducted by connecting the harvester to a rectifier for AC-to-DC signal conversion and an oscilloscope for voltage measurement. A DC motor replicated the rotational motion at the frequencies from the simulation, and the power output was measured. Using the power transfer theorem, simulation and experimental power outputs were calculated, resulting in values of 188, 513, and 1293 μW and 88.89, 336, and 923 μW, respectively. These results reveal that the designed harvester is competitive with those of existing rotational energy harvester designs, demonstrating the promising potential of this novel harvester.

A New Isolated Topology of DC–DC Converter Based on Piezoelectric Resonators

This paper presents a new isolated topology of DC-DC converter based on piezoelectric resonators. Contrary to most existing topologies, the proposed one uses the natural isolation of piezoelectric resonators to isolate the converter's output from the input and vice-versa. Considering the resonators' constraints, our study focuses on the most efficient isolated conversion cycle with zero-voltage switching (ZVS) operations. The case studied is a highly efficient step-down isolated DC-DC converter with a gain ranging from 0 to 1 and an input voltage up to 360 V. The converter uses two piezoelectric resonators working in series. The conversion principle is validated thanks to a prototype operating at a frequency around 95 kHz. Experimental measurements are made on a wide range of input voltage from 12 V to 360 V with a conversion ratio of 0.0165 to 0.95. The output power reaches either 179.1 W with an 89% efficiency at 360 V input voltage and 346 V output voltage, or 4.5 W with a 97.2% peak efficiency for a 48 V to 45.8 V conversion, using a 25 mm piezoelectric disc with a thickness of 2 mm and 1 mm respectively. An efficiency higher than 80% is measured over a wide range of operating points.

Detection of Anomalies in Additively Manufactured Metal Parts Using CNN and LSTM Networks

The process of metal additive manufacturing (AM) involves creating strong, complex components by using fine metal powders. Extensive use of AM methods is expected in near future for the production of small and medium-sized batches of end-use products and tools. The ability to detect loads and defects would enable AM components to be used in critical applications and improve their value. In this study, the Surface Response to Excitation (SuRE) method was used to investigate wave propagation characteristics and load detection on AM metallic specimens. With completely solid infills and the same geometry, three stainless steel test bars are produced: one conventionally and two additively. To investigate the effect of infills, four bars with the same geometries are 3D printed with triangular and gyroid infills with either 0.5 mm or 1 mm skin thickness. Two piezoelectric disks are attached to each end of the test specimens to excite the parts with guided waves from one end and monitor the dynamic response to excitation at the other end. The response to excitation was recorded when bars were in a relaxed condition and when compressive loads were applied at five levels in the middle of them. For converting time-domain signals into 2D time-frequency images, the Short-Time Fourier Transform (STFT) and Continuous Wavelet Transform (CWT) were implemented. To distinguish the data based on fabrication characteristics and level of loading, two deep learning models (Long Short-term Memory algorithm (LSTM) and Convolutional Neural Networks (2D CNN)) were utilized. Time-frequency images were used to train 2D CNN, while raw signal data was used to train LSTM. It was found that both LSTM and 2D CNN could estimate solid parts' loading level with an accuracy of more than 90%. In parts with infills, CNN outperformed LSTM for the classification of over five classes (internal geometry and loading level simultaneously).

Complex piezoelectric material parameters of hard PZT determined from a single disc transducer

A poled piezoelectric ceramic such as lead zirconate titanate (PZT) belongs to a C crystal class, with ten independent material constants. If we consider losses, all the material parameters can be represented in complex form as all the ten material parameters also have ten loss components associated with them. Therefore, a total of 20 independent material constants are required to obtain the entire model. In this work, we present a procedure for determining the complete reduced matrix of a piezoelectric ultrasonic disc transducer using one-dimensional resonance analysis in thickness and radial modes and parametric sweep using finite element analysis to numerically calculate the impedance while comparing it with the measured impedance. The objective is to obtain the material parameters that minimize the error between the measured impedance data and the numerical impedance curve without using any optimization techniques. We can follow the standard procedure of resonance analysis for radial and thickness modes and then conduct a sensitivity analysis using parametric sweeps in COMSOL to evaluate the unknown material values. In addition, we present the transform equations in reduced matrix form to evaluate the critically sensitive parameters concerning other consistent evaluated material constant sets. To validate the procedure, we used the impedance responses of two piezoelectric discs with diameter-to-thickness ratios of 25 and 22.5. The comparison between the numerical and experimental results shows an excellent agreement for electrical impedance curves.

Experimental and simulation study of a hydraulic piezoelectric energy harvester under different connection modes

Pressure pulsation from water hydraulic system exhibits great potential in vibration energy harvesting. Herein a novel hydraulic piezoelectric energy harvester is proposed, which exhibits excellent insulation and sealing performance. The effect of connection modes such as single output, series and parallel connection, on the energy harvesting performance is investigated at different parameters by the experiment. The theoretical analysis and simulation study are employed to explain the energy harvesting process. The results show that the transient voltage exhibits alternating characteristics, and it has the same period with the transient pressure. The piezoelectric disk closer to the liquid inlet has greater energy harvesting ability. The voltage increases as the static pressure rises and the main influence factor is pulsation amplitude rather than static pressure. Moreover, the root mean square voltage of series connection is highest, and it increases with the increasing resistance, but the average power first increases and then decreases. The parallel connection mode has higher average power and lower optimal resistance. The average power and power density can respectively reach 394 μW and 1.34 mW/cm3 under 3 MPa and 20 KΩ. This paper can provide methods for the sustainable power supply of sensors in water hydraulic system.

Solid-liquid coupling of in-phase and out-of-phase vibrations for two piezoelectric disks

Theoretical analysis is used to solve the solid–liquid coupled vibration characteristics for two piezoelectric disks in a limited space and verified with experimental measurements. Based on the Navier–Stoke equation and equilibrium of motion, the Rayleigh-Ritz and energy methods were developed to analyze the solid–liquid coupled system. Following an entire systematic procedure, two piezoelectric disks immersed in hydrostatic compressible fluids were analyzed using the piezoelectric constitutive equation to perform the in-phase and out-of-phase vibration. The full-field, non-contact, optical technique, called amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI), was applied to experimentally measure the vibration properties in a solid–liquid coupling system, including the mode shapes and resonant frequencies. The experimental results are presented in good agreement with the theoretical solutions and finite element calculations. Under the solid–liquid coupled system, the distributions of pressure fields and velocity vectors of fluids were also determined in the correspondent vibrating modes. Finally, it is interesting to show the tendency to close the same resonant frequency both on the in-phase and out-of-phase vibrations when the fluid depth increases. The research outcomes can provide a guide in the design of hydrostatic components.