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The triple-layered multimorph piezoelectric acoustic actuators were fabricated and studied to investigate the effects of the electrical configurations of the piezoelectric ceramics on the voltage-displacement and frequency response characteristics. The serial and parallel polarized piezoelectric multimorph ceramics were electrically connected in two different configurations of series and parallel, respectively: the serial multimorph in series connection (SMS), the serial multimorph in parallel connection (SMP), the parallel multimorph in series connection (PMS), and the parallel multimorph in parallel connection (PMP). Then, the vibrational displacement characteristics for each type of the triple layered multimorph ceramics were investigated by Finite Element Analysis (FEA) simulation and Laser Scanning Vibrometer (LSV) measurement. The maximum resonant displacements for SMS and PMP types were measured as 2.37 and 3.6 μm, respectively, which are at least 4.8 times higher than for SMP and PMS types. These LSV measured results were relatively in good agreement with the FEA simulated results. Moreover, due to these larger displacement characteristics, the piezoelectric acoustic actuators fabricated with the ceramics of SMS and PMP types had very high average SPLs of 83.1 dB and 85.7 dB at a distance of 10 cm away, respectively, which provide over 20 dB higher sound pressures than those for SMP and PMS types.

Piezoelectric bimorph bender actuators find application number of areas, ranging from automotive to health care. High voltage operation in harsh environments poses ever more stringent demands on functionality and lifetime. In these high performance benders, the trade-off between functionality and lifetime becomes of increasing importance, and a model-based understanding is imperative for further tailoring actuator performance. An important issue in this is the non-linear electromechanical coupling and mechanical poling/depoling processes. PZT materials are known to exhibit non-linear stiffness when strained. This effect is attributed to domain re-orientation and can result in mechanical depoling. In bimorph benders where only one of the PZT members is actuated, the non-linear stiffness effect results in higher deflections than are predicted by linear elastic models. This effect is larger for soft PZT materials than for hard PZT materials. In this work, the non-linear behaviour of piezoelectric bimorphs was characterized by dynamic mechanical thermal analysis (DMTA). Unimorph benders were characterized in different configurations. Two different PZT materials (one soft, one hard) were used. The non-linear stiffness behaviour is included in a model for piezoelectric multimorphs. The multimorph model predictions are compared to measured deflection and blocking force of bimorph benders made from soft PZT material. The model incorporating non-linear stiffness predicts deflection and blocking force values more accurately than the linear model for the situation studied. Attention is paid to the stresses induced during poling of the bimorphs and their effect on performance and lifetime. © 2008 Springer Science+Business Media, LLC.

Complex piezodrives are frequently used in mechanisms of optical systems. They can be bimorph, axial and complex combined stacks. This paper deals with axial piezostacks used in piezoconverters. They make it possible to develop unipolar or bipolar motion which ensures the displacement to be dependent on each piezoelement of the compound stack sections. The bifurcation problem of a piezodrive has been solved by evaluating physical properties of piezoelements in piezostacs and sealing the material. It has made it possible to prove that piezostacs have a lot of static operation possibilities. The original solution of the actuator enabled the choice of optimal initial stresses in piezostacs. The experimental investigation of piezodrives with combined piezostacs has revealed the possibilities to optimize the design and materials for obtaining maximum displacement. These piezodrives may be applied in various systems like gyroscopes and telescopies.

Crack free perovskite PbZr0.53Ti0.47O3 (PZT (53/47)) thick films up to 30 μm were prepared on flexible platinum-coated titanium foil substrates (Pt/Ti) by a metal organic decomposition (MOD) process. The dielectric, ferroelectric and piezoelectric properties of the films were examined and discussed. A well-saturated hysteresis loop of the thick film was present in almost rectangular shape (Pr = 35 μC/cm2; Ec = 32 kV/cm). The efficient piezoelectric coefficient d33, f of the thick film is about 448 (1 kHz). PZT piezoelectric vibrators were made in bimorph mode. The displacements of the vibrators were investigated as the functions of the applied electric field and the substrate thickness. Under the same condition, the vibrator made from the thinnest Pt/Ti substrate gives the largest displacement.

For devices having non-linear contact, load plays a fundamental role. Variations in the characteristics of the load cause change in eigenfrequency and amplitude of the vibration. In most technical applications, this unwanted behaviour is cancelled by the use of control algorithms. However, multiple applications, like bond quality monitoring or chemical and pressure sensors, have found that the load may be characterised by interpreting the change in characteristics of a resonant vibrating device used as a sensor. Surgical resection of tumours is a very difficult task. After localising the tumour by the use of imaging techniques, the resection demands the surgeon to decide where and what to resect based on visual and tactile differentiation of tumour and healthy tissue. Exactness of this process could be enhanced if we can provide the surgeon with a device capable of evaluating mechanical characteristics of the tissue much more accurately than the surgeon himself can do. As the mechanical characteristics of tumour and healthy tissue differ but slightly, the task is to design a system with high sensitivity. Therefore, we have developed a resonant actuator-sensor that allows the differentiation among distinct media that have similar mechanical characteristics to tumour and healthy tissue using a piezoelectric bimorph. The design is based on the detection and evaluation of frequency shift and amplitude variation of the fundamental and higher harmonics using one layer for the resonant excitation of vibration and the other one as the sensing element.

The performance improvement of the LIPCA (Lightweight Piezo-Composite curved Actuator) is investigated in this paper. The LIPCA is known as the best layered piezo-composite unimorph actuator because of not only high performance but also its flexible analytical design model and simple fabrication technique. Besides, originated from efforts to develop highly induced-strain piezoelectric ceramic, the IDEAL (Inter-Digitated Electrode Actuation Layer) have shown to be a potential candidate in unimorph or bimorph actuator designs. In a latest model of IDEAL designs, the inter-digitated electrodes (IDEs) had been proposed to be embedded directly into the piezoelectric ceramic wafer. Hence, the resulting stacked-type transducer is able to have full d33 actuation mechanism which can produce almost twice larger strain than that produced by the conventional d31 actuation mechanism. Therefore, by replacing the original actuation layer with IDEAL in the lay-up structure of the conventional LIPCA design, one can expect improvement to the performance of the actuator, e.g., gaining higher of out-of-plane actuation displacement. The modified design of LIPCA had been investigated considering mechanical properties of an inhomogeneous IDEAL. As the result, an IDEAL fabricated with low-elastic-modulus IDEs have shown to give considerably improvement on actuation performance of the LIPCA. Following that sense, a new homogenization model applied to the embedded IDEAL is proposed and able to convince the previously obtained result.

The pressure regulator which is used for controlling the reducing pressure in the piezoelectrically driven pneumatic valve has been studied. The pneumatic valve of this study is two-stage type and consists of a piezoelectric actuator, a controller, a poppet valve and a pressure regulator. Nominal flow of 50 lpm, maximum operating pressure of 0.9 MPa and frequency characteristic of 10 Hz or higher are required in this pneumatic valve. The pressure regulator is needed because piezoelectric actuator has no ability to control the pressure of 0.9 MPa directly. In this study, a bimorph type PZT actuator of 25.2 mm(L) × 7.2 mm(W) × 0.5 mm(H) with constant of −220 × 10−12 CN−1 was proposed and investigated. Maximum operating force of 0.052 N and maximum displacement of 63 μm were achieved from the fabricated PZT actuator. From the analysis results, an orifice diameter of 0.6 mm was selected for a piezoelectric actuator. The pressure regulator which can be operated under 0.15 MPa easily was designed and manufactured. Performance and effects of design parameters were simulated by the Simulink of Matlab software, and it was confirmed that the performance characteristics of manufactured pressure regulator are superior in the common use pressure range of 0.5 to 0.7 MPa. The results show that the proposed pressure regulator is suitable for the pneumatic valve with a PZT actuator.

The vast reduction in the size and power consumption of sensors and CMOS circuitry has led to a focused research effort on the on-board power sources which can replace the batteries. The concern with batteries has been that they must always be charged before use. Similarly, the sensors and data acquisition components in distributed networks require centralized energy sources for their operation. In some applications such as sensors for structural health monitoring in remote locations, geographically inaccessible temperature or humidity sensors, the battery charging or replacement operations can be tedious and expensive. Logically, the emphasis in such cases has been on developing the on-site generators that can transform any available form of energy at the location into electrical energy. Piezoelectric energy harvesting has emerged as one of the prime methods for transforming mechanical energy into electric energy. This review article provides a comprehensive coverage of the recent developments in the area of piezoelectric energy harvesting using low profile transducers and provides the results for various energy harvesting prototype devices. A brief discussion is also presented on the selection of the piezoelectric materials for on and off resonance applications. Analytical models reported in literature to describe the efficiency and power magnitude of the energy harvesting process are analyzed.

A thin film lead zirconate titanate Pb(Zr,Ti)O3 (PZT), energy harvesting MEMS device is developed to enable self-supportive sensors for in-service integrity monitoring of large social and environmental infrastructures at remote locations. It is designed to resonate at specific frequencies of an external vibrational energy source, thereby creating electrical energy via the piezoelectric effect. Our cantilever device has a PZT/SiNx bimorph structure with a proof mass added to the end. The Pt/Ti top electrode is patterned into an interdigitated shape on top of the sol-gel-spin coated PZT thin film in order to employ the d 33 mode. The base-shaking experiment at the first resonant frequency of the cantilever (170 × 260 μm) generates 1 μW of continuous electrical power to a 5.2 MΩ resistive load at 2.4 V DC. The effect of proof mass, beam shape and damping on the power generating performance are modeled to provide a design guideline for maximum power harvesting from environmentally available low frequency vibrations. A spiral cantilever is designed to achieve compactness, low resonant frequency and minimum damping coefficient, simultaneously.

Recently, a tiny piezoelectric linear motor using a vibration mode of the transducer has been invented. The motor consists of a shaft, mobile element, and piezoelectric transducer using a piezoelectric radial mode bimorph disk. The fringe of the bimorph disk is fixed firmly which means this area has no degree of freedom. Therefore, the radial mode of the transducer transfers to the flexure mode. The mobile elements move along the Pyrex shaft by the impact force generated by the flexure mode of the piezoelectric transducer. The motors are operated at their resonant frequencies. The dynamic properties of the motor have been intensively measured and analyzed according to the applied voltage waveforms at the resonant frequencies. As the sawtooth and rectangular voltage waveforms are applied, the velocity, the thrust force, and the velocity dependence of the mobile position are measured. The dynamic characteristics are also analyzed within a period of each wave using laser vibrometer. The velocity of the mobile is moderately constant along the shaft. The better dynamic characteristics are obtained in the case of applying the rectangular waveform.

Bimorph type piezoelectric vibrator with generating function is designed using Finite Element Method (FEM) and fabricated. Design of piezoelectric vibrator by FEM is focused at its length and the weight of added mass. Also, the vibration and charging properties of the fabricated piezoelectric vibrator are investigated. As the FEM analysis results, when the piezoelectric vibrator is the length of 18 mm and the additive weight of 0.3 g, its resonance frequency decrease to 150 Hz. Also, when input voltage of 20 V is applied, output voltage is 10.285 V in generating element. As the properties of piezoelectric vibrator fabricated, when input voltage is 20 Vrms, the acceleration of piezoelectric vibrator and output voltage are about 1.1 G and 10.18 Vrms, respectively. When gold capacitor of 0.0066 [F] is used as the load, the output voltage is about 3 [VDC] after 3600 [sec] driving time.

This paper presents piezoelectric ring-morph actuators designed to produce a large flexural displacement for valve actuation application. The ring-shaped piezoelectric plate in the actuator produces a radial contraction or expansion and causes the center part of the metal disc to generate a large flexural displacement. The PZT ring creates a space under the metal disc which permits it to bend with a curvature larger than that of the conventional bimorph in the axis direction of the ring-morph when the PZT ring under the metal disc contracts. A prototype with diameter of 25.4 mm and thickness of 0.55 mm could produce a total stroke (static displacement) of over 130 μm under a driving voltage of ±300 V and a load of 2 N. The maximum generative force of ring-morph actuator was about 30 N.