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Aluminum Nitride Energy Harvesters for High Temperature Wireless Sensor Systems
Keywords: energy harvester, aluminum nitride, high temperature
The growing interest in autonomous wireless sensor networks (WSNs) for structural health monitoring, where wireless sensor systems are distributed to target sites without considering replacing their power supplies, spurs an obvious need of sustainable energy-harvesting based power sources to substitute conventional lifespan-limited batteries. Particularly, such power solutions become more essential for wireless sensors in harsh industrial environments such as automotive engines, gas turbines, and geothermal/oil wells, where elevated temperatures (250°C-600°C) largely limit battery usage and maintenance for these sensor systems becomes much more difficult and cost-ineffective. To address this issue, a high-temperature MEMS piezoelectric energy harvester consisting of aluminum nitride (AlN)/silicon carbide (SiC) composite diaphragm has been developed, aiming at harvesting power from periodic pressure pulses. Specifically, the AlN/SiC diaphragm energy harvester with elastic support design [1], compared to the device with clamped boundary previously reported in [2], has been shown to provide higher output power at both room and elevate temperatures up to 320°C. By introducing concentric rows of annular slots near diaphragm edge, similar to that in [3], but modified for remaining the majority deflection within the inner diaphragm section instead of supporting springs, the elastically-supported diaphragm structure with partially-relieved intrinsic stress enables higher sensitivity and better electromechanical coupling. The presented device represents the first energy-harvesting power source with experimentally verified stable operation at elevated temperatures >300°, showing great potentials for a sustainable power source that can be easily integrated with high temperature SiC-based circuitry and MEMS sensors, and therefore allow autonomous wireless sensor systems for a true long-lived, set-and-forget WSN for harsh environment applications.
Yun-Ju Lai,
University of California, Berkeley
Berkeley, CA

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