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MEMS-Based AlScN Resonating Energy Harvester with Solidified Powder Magnet

: Yarar, E.; Fichtner, S.; Hayes, P.; Piorra, A.; Reimer, T.; Lisec, T.; Frank, P.; Wagner, B.; Lofink, F.; Meyners, D.; Quandt, E.


Journal of Microelectromechanical Systems 28 (2019), No.6, pp.1019-1031
ISSN: 1057-7157
ISSN: 1941-0158
Journal Article
Fraunhofer ISIT ()

Energy harvesters offer an attractive power source alternative in particular for the next generation of mobile sensor applications. The current work investigates the power output of bulk micromachined 3 mm × 2 mm × 50 μm sized cantilever-type piezoelectric (2 μm AlScN) energy harvesting device that is magnetically driven by miniaturized NdFeB permanent magnets attached to the free-end of the cantilevers. A novel energy harvester and one potential application is introduced. Properties and relevant figures-of-merit for AlScN in comparison to AlN are discussed on device level. Magnetic properties of the permanent magnet are summarized. The influences of the electrode area coverage, applied external magnetic field as well as fatigue properties of the harvesters are investigated. FEA results of the harvester's magnetic interactions are presented. Finally the suitability of a coil in comparison to a piezoelectric energy harvester is evaluated. A maximum peak power of 15.6 μW is obtained from a 2 mm wide cantilever with 2 mm long top electrode when driven under an homogeneous external field of magnitude BAC = 1 G at resonance f res = 3240 Hz. The maximum power density is calculated as 15.8 mW/cm 3 (2.6 W/m 2 ) when applying the optimal load impedance approximately 117 kΩ.