Resonant vibration harvesters can efficiently scavenge periodic high-frequency mechanical oscillations (20-500 Hz) that are commonly found in industrial monitoring and vehicle instrumentation fields, and provide maintenance-free power source for wireless sensor networks. Previously reported micro-scale implementations have shown low efficiency due to arbitrary design dimensions, limited electromechanical coupling with conventional fabrication techniques, and impractically narrow operation bandwidths (1-2 Hz). In this project, we analytically optimized the structure and electrode dimensions, material thicknesses, and stress-balancing in a piezoelectric cantilever harvester. Three generations of devices are microfabricated using bulk-PZT for its high piezoelectric coupling, and tungsten for its large mass density. A competitive performance is demonstrated with 205-μW generation in a 27-mm3 device volume at 1.5 g, 154 Hz excitation. These prototypes are among the best performing vibration harvesters in the literature with power density of 3-10 mW/cm3/g2 and bandwidth of 14-33 Hz.
E. E. Aktakka, R. L. Peterson, K. Najafi, “Multi-layer PZT stacking process for piezoelectric bimorph energy harvesters” 11th Int. Conf. on Micro and Nanotechnology for Power Generation and Energy Conversion App. (PowerMEMS’11), Seoul, Rep. of Korea, pp. 139-142, Nov. 2011. [PDF]
E. E. Aktakka, R. L. Peterson, K. Najafi, “Thinned PZT on SOI process and design optimization for piezoelectric inertial energy harvesting”, 16th International Conference on Solid-State Sensors, Actuators, and Microsystems (Transducers’11), Beijing, China, pp. 1649-1652, Jun. 2011. [PDF]
E. E. Aktakka, R.L. Peterson, K. Najafi, “A CMOS-compatible piezoelectric vibration energy scavenger based on the integration of bulk PZT films on silicon”, IEEE International Electron Devices Meeting (IEDM’10), San Francisco, USA, pp. 31.5.1-31.5.4, Dec. 2010. [PDF]