The use of cantilevered piezoelectric bimorphs under transversal excitations is an area of research well reported in literature. These devices may be tapered into triangular geometries in order to enhance axial strain over the surfaces of the device for more reliable operation. This study reports the comparison of rectangular and triangular cantilevered bimorphs of equal volume and matching resonance frequency, where it is seen that tapering geometry enhances the electromechanical coupling coefficient, which may not necessarily be the only parameter involved in enhancing power output. This is indicated in the case of a triangular cantilevered device without a proof mass, which with increased coupling is unable to outperform a rectangular device. The addition of a nominal proof mass on a rectangular and triangular device increases not only the electromechanical coupling coefficient, but also increases the damping ratio in the devices. This effect is more pronounced in the case of triangular bimorphs, and a 40% improvement in power output is seen. Therefore, these studies provides insights into the changing parameters with changing shapes, which may provide better optimization parameters for improving piezoelectric energy harvesting from cantilevered devices.
Flexural plate wave (FPW) device is one of promising devices for biological sensor application, because its electronic
circuit can be isolated from the medium being detected, and it shows low acoustic energy loss in liquid medium.
Moreover, FPW device arrays on the silicon based substrate can be possible at low cost fabrication by micromachining
technology, so that it offers batch processing for economic sensor fabrication. In this study, piezoelectric ZnO film was
chosen as a material for a biological sensor platform, due to non-toxicity, and chemical and thermal stability. RF
magnetron sputtering and chemical solution deposition (CSD) were investigated as film fabrication method. To launch
and receive the acoustic wave through the piezoelectric material, it is required that the piezoelectric ZnO film have
strong c-axis orientation in the device. For the magnetron RF sputtering, process parameters such as gas ratio, substrate
types, and temperature, were varied, and heat treatment and substrate types for CSD. Results indicated that the preferred
orientation and microstructure of ZnO films can be controlled by the variation of the process parameter, and that uniform
and dense microstructures of ZnO films were obtained by both fabrication methods. CSD method showed, however,
stronger dependence of the preferred orientation on substrate types while less dependence on the substrates for sputtering
due to energetic sputtered species. Mechanism for ZnO thin film growth will be discussed. FPW devices have been
successfully integrated onto 4 inch Si-wafer with 22 different interdigitated electrodes designs, and the device
demonstrated the capability to detect biological quantity of 446.13 cm2/gram of sensitivity.
Piezoelectric materials (PZT) have shown the ability to convert mechanical forces into an electric field in response to the
application of mechanical stresses or vice versus. This property of the materials has found extensive applications in a
vast array of areas including sensors and actuators. The study presented in this paper targets the modeling of PZT bender
for voltage and power generation by transforming ambient vibrations into electrical energy. This device can potentially
replace the battery that supplies the power in a micro watt range necessary for operating sensors and data transmission.
One of advantages is the maintenance free over a long time span. This paper focuses on the analytical approach based on
Euler-Bernoulli beam theory and Timoshenko beam equations for the voltage and power generation, which is then
compared with two previously described models in literature; Electrical equivalent circuit and Energy method. The three
models are then implemented in Matlab/Simulink/Simpower environment and simulated with an AC/DC power
conversion circuit. The results of the simulation and the experiment have been compared and discussed.
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