1,720,978 research outputs found
Design and fabrication of a novel MEMS thermoelectric generator
No full textAbstractA thermoelectric microgenerator based on a novel structure, in which the heat flowing in elements with different thermal resistances produces local temperature differences in the device, has been designed, fabricated in BESOI technology and experimentally characterized. The temperature differences in the microgenerator are converted into a voltage by means of the Seebeck effect exploiting planar thermocouples
Micromachined piezoresistive inclinometer with oscillator-based integrated interface circuit and temperature readout
No full textNonlinear Multi-Frequency Piezoelectric MEMS Converter Array for Vibration Energy Harvesting
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Triaxial ball-impact piezoelectric converter for autonomous sensors exploiting energy harvesting from vibrations and human motion
No full textBall-impact piezoelectric converter for multi-degree-of-freedom energy harvesting from broadband low-frequency vibrations in autonomous sensors
No full textThis work proposes a piezoelectric converter for energy harvesting composed of a rigid ball enclosed among piezoelectric diaphragms arranged in a three-dimensional geometry. When the structure is excited by mechanical vibrations, the ball repeatedly bounces and hits one or more diaphragms, implementing the impact technique in a multi-degree-of-freedom configuration. The converter was designed and built and a single-axis two-diaphragm version was characterized under sinusoidal and random vibrations from 10 Hz to 100 Hz at different amplitude values up to 1.8 gRMS. The experimental results show that the maximum RMS converted power provided by each diaphragm both with sinusoidal and random excitations is about 4 μW. The triaxial converter was tied to the ankle of a person and, in about one minute of walking at 4 km/h, 1 mJ of energy is extracted and stored by a custom rectifier circuit into a 470-μF capacitor
Multi-frequency array of nonlinear piezoelectric converters for vibration energy harvesting
No full textEnergy harvesting from wideband and random vibrations demands for techniques and solutions to overcome limitations of linear converters, which best operate when the frequency of vibrations matches the resonant frequency of the converter. Viable approaches comprise, among others, the use of array of linear harvesters with different resonant frequencies, the adoption of nonlinear techniques or the exploitation of mechanically coupled converters. This work proposes a piezoelectric energy harvester where the combination of such techniques is explored in a unique device. The harvester is composed of an array of four piezoelectric cantilevers fabricated by screen printing lead zirconate titanate (PZT) films on a stainless steel substrate. Nonlinear behavior of the cantilevers is achieved by exploiting the interaction between a magnet and their ferromagnetic steel substrate. Two configurations have been analyzed where the magnet is either fixed on the harvester base, or it is elastically suspended through a spring on the harvester base. The latter configuration introduces a mechanical coupling among the cantilevers. For the experimental characterization, the prototype has been excited by band-pass filtered white-noise mechanical vibrations in the range 10-100 Hz with amplitude in the range 0.1-2.2 g. The obtained experimental results show that the rms values of the open-circuit output voltage for each cantilever increase in the nonlinear configuration and it can be up to 215% higher for the case with the elastically suspended magnet compared to the case of the same array operated in linear regime
Pyroelectric effect in PZT thick films for thermal energy harvesting in low-power sensors
No full textPiezoelectric actuators for microfluidic acoustic-wave manipulation of in-liquid particles
No full textThe possibility to generate acoustic modes based on FPWs (Flexural Plate Waves) in a generic non-piezoelectric substrate for microfludic applications by means of piezoelectric actuators has been explored and described in this paper. The FPW acoustic modes are generated by means of actuators made of Lead Zirconate Titanate (PZT) layers with InterDigital Transducers (IDTs) screen-printed on alumina (Al2O3) substrate. The experimental results show that, by exciting the resonances of the actuators, circular vortex rotations are obtained in a fluid drop placed on the substrate between the IDTs. Micrometric particles dispersed in the drop allow to demonstrate that standing waves can be generated in the liquid obtaining particle accumulation along circular lines. These results suggest the possibility to employ the proposed actuators for fluid mixing and controlled positioning of dispersed particles
Portable energy-logger circuit for the experimental evaluation of energy harvesting solutions from motion for wearable autonomous sensors
No full textAbstractIn this paper, a portable battery-powered energy-logger circuit to monitor the energy harvested by different piezoelectric converters mounted on selected positions of the human body under typical daily activity is proposed. The circuit logs on an SD memory card both the rms value of the acceleration imparted to the Energy Harvesting (EH) converter under test and the time intervals needed to achieve a predefined amount of energy stored on capacitors. The energy-logger circuit was tested with three different types of piezoelectric EH converters under different excitation conditions allowing to measure an effectiveness index given by the time necessary to accumulate the energy required to power one operating cycle of the autonomous sensor module representing the load
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