Macro energy harvester based on Aluminium Nitride thin films

This paper deals with the conception of simple designed macro piezoelectric cantilevers for energy harvesting to power low consumption sensors. Because some applications do not necessarily require micron-scale dimensions, it has been decided to prospect the potential of cantilevers of centimetre size made of piezoelectric material in order to convert low frequency vibrations into a sufficient electrical power for autonomous communicating sensors. This study has been made in three different parts: mechanical design of the macro cantilever, technological realization and characterization to prove the high potential for energy harvesting of these types of devices. Here we present piezoelectric vibrating macro cantilevers based on AlN thin films deposited on Silicon. Once released, these devices resonate near 100 - 200Hz and exhibit a voltage reaching several tenth of volt on an oscilloscope with 1 MΩ input resistance. This last associated with a quality factor reaching 71 as observed from experiment corresponds to a rather weak acceleration (0.3g). By using an impedance adaptation and a power management circuit we obtained a power of more of 100 μW for an acceleration of about 0.2 g at 155 Hz.