MEMS Piezoelectric Energy Harvesters for Harsh Environment Sensing

A microelectromechanical systems (MEMS) energy harvesting device aiming at powering wireless sensor nodes for structural health monitoring (SHM) in harsh environments is presented. For these types of wireless sensor networks (WSNs), the sensor modules are required to operate at elevated temperatures (>250 degrees C) with capabilities to resist harsh chemical conditions, where the use of battery-based power sources becomes challenging and in turn enormously increases their cost to a point no longer economically efficient. To address this issue, energy harvesting technology is adopted here to replace batteries and provide a sustainable power supply for sensor nodes towards maintenance-free harsh environment WSNs. In particular, the micromachined device presented in this work utilizes piezoelectric energy harvesting via a composite diaphragm structure composing of piezoelectric aluminum nitride (AlN) and silicon carbide (SiC), both exhibiting superior material properties against hostile conditions, to harvest energy from periodic pressure pulses. The fabricated AlN/SiC diaphragm energy harvester is characterized at elevated temperatures and shows reliable power generation at >300 degrees C. A dc output power up to 1.8 mu W is demonstrated when connecting the harvester to a power conditioning circuit under 1.61-psi (rms) pressure pulses. The generated power level together with verified high temperature performance of AlN/SiC energy harvester, identifies its great potential in serving as energy sources for harsh environment sensors.