Most inertial energy harvesters can only operate at a single vibrational axis. Harvesting electrical energy from vibrations applied along any spatial direction can both improve their power output and extend the practical applications. In this study, we developed for the first time a piezoelectric inertial harvester for scavenging vibrational energy in all three dimensions. The harvester is formed of optimized suspensions and partitioned electrodes with different phase outputs according to the vibration axis. In a packaged volume of 6.5 cm3, the harvester has generated 5-53 μW from 50 mg acceleration applied in in-plane and out-of-plane directions at the respective resonance frequencies (387-398 Hz) with a half-power bandwidth of 8-16 Hz. The normalized power density (0.3-3.2 mW/cm3/g2) compares very favorably with respect to previously reported multi-axis energy harvesters (3/g2).
E. E. Aktakka, K. Najafi, “Multi-axis inertial energy harvester based on piezoelectric crab-legs with partitioned electrodes,” 16th Int. Conf. on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS’16), Paris, France, Dec. 2016.
E. E. Aktakka, K. Najafi, “Three-Axis Piezoelectric Vibration Energy Harvester,” 28th IEEE International Conference on Micro Electro Mechanical Systems (MEMS’15), Estoril, Portugal, Jan. 2015.