A free-standing, thick-film piezoelectric energy harvester

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 mum was found to have Youngpsilas modulus of 3.8times10 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 mum 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 kOmega. 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.