In this paper, design, technology and properties of multi cantilever transducer for energy harvesting application were described. The piezoelectric transducer was made in LTCC (Low Temperature Cofired Ceramics) technology using PZT (Lead Zirconate-Titanate) based tape. In such devices the highest power can be reached at resonance frequencies of the cantilevers. Eight bimorph transducers with lengths corresponding to 33, 50, 58, 66, 75, 82, 91 and 100 Hz resonant frequency, were designed. The transducers were polarized in serial or parallel configuration. To avoid voltage reduction in the system of a few piezoelectric bimorphs, rectifiers were applied for each cantilever.
Transducers had optimum resistance in ranges of 60–140 kΩ and 300–600 kΩ for bimorphs poled in parallel and serial configuration, respectively. The mean output power under sinusoidal excitation with 20 μm vibration amplitude calculated from all maxima at resonant frequencies for optimum load, were equal to 10.3 μW and 12.4μW for parallel and serial configurations with rectifier. Without rectifier the values were equal to 18.2 μW for both the transducers. In case of mean output power, the difference between both the transducers was not really significant, however at higher frequency the maximum power was higher for serial configuration. Besides, the output voltage obtained in serial bimorph was higher than in parallel one. The mean power density for all the resonant peaks measured at 0.41 g was equal to 210 μW/cm3/g and 360 μW/cm3/g with and without rectifier, respectively.
A sandwiched piezoelectric transducer with flex end-caps for energy harvesting in large force environments