A Free-Standing, Thick-Film Piezoelectric Energy Harvester

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Description/Abstract

In this paper, free-standing structures in the form of cantilevers, fabricated by using a combination of conventional thick-film technology and sacrificial layer techniques, is proposed. These structures were designed to operate as energy harvesters at low-levels of ambient vibration and were characterised using a shaker table over a range of frequencies and acceleration levels. A cantilever with dimensions of 13.5 mm long by 9 mm wide and total thickness of 192 micron was found to have Young’s modulus of 3.8 x 10 N/m2, effective mass of 0.035g and spring constant of 362 N/m. Samples of length 18 mm and functional elements (Lead Zirconate Titanate, PZT) of thickness 80 m were found to produce an output voltage of up to 130 mV at their resonant frequency of 229 Hz, for an acceleration level of 0.981 ms-2 when driving into a resistive load of 60 kOhm. The addition of a proof mass was shown to improve the electrical output power generation. In a series of experiments, the electric power generated by a beam having a proof mass of 2.2 g, resulted in a nine-fold improvement of output power compared to a device with no proof mass. The size of the proof mass is also an important factor in determining the output power of the device.