MEMS-BASED PIEZOELECTRIC ENERGY HARVESTER FOR POWERING WIRELESS SENSOR NODES

Microelectromechanical systems (MEMS) embody, an advanced semiconductor technology, which encompasses moving components as well as electronics on a single chip. Over the years, MEMS-based devices, such as sensors, accelerometers have become pervasive appearing in all types of applications ranging from consumer electronics to automotive to the medical devices sector. One other area that is also proliferating is the energy harvesting application using MEMS-fabricated piezoactuators. Energy harvesting (EH) is the process of converting energy from ambient sources into electricity to make devices or systems more self-sufficient. Energy harvesting technologies use energy generated from the environment or from humans to enable devices or systems to be powered directly without having to rely on batteries. MicroGen Systems LLC, based in Ithaca, NY, has introduced a MEMS-fabricated piezoelectric energy harvester called BOLT micropower generator that includes a piezoelectric layer that generates electric charge in response to an external stimuli mainly vibration.

MicroGen Systems used Infinite Power Solutions’ (Littleton, Colorado) new IPS-EVAL-EVH-01 energy harvesting evaluation kit to power a wireless temperature sensor supplied by Texas Instruments at the recently held Sensors Expo and Tradeshow 2011 in Rosemont, Illinois. The energy harvesting kit by Infinite Power Solution comes with a complete microelectronic circuit system that enables harvesting the energy from BOLT transducer and stores it in the EH kit’s THINERGY MEC 101 microenergy cell. MicroGen’s BOLT060 energy harvesting device has a resonant frequency of 60 hertz (Hz), while BOLT120 has a fundamental resonant frequency of 120 Hz. In the demo, the BOLT060 was vibrated at 60 Hz frequency and with an acceleration amplitude of 0.7 g (g = 9.8 meter per second square [m/s²]). The generated energy was stored in the thin-film battery ‘THINERGY’ solid-state micropower cell. BOLT devices are approximately 1.0 cm² in area and can generate up to 200 milliwatt (mW). Due to the advantage of using MEMS fabrication technique, BOLT micropower generator can be scaled further. The advantage of using the IPS-EVAL-EVH-01 energy harvesting kit apart from the award winning thin film battery is the presence of an energy harvesting power management integrated circuit supplied by Maxim Integrated Products. The power management circuit can help boost the voltage when required and can also be programmed to regulate the output voltage that goes from the circuit to power the wireless temperature sensor.

According to MicroGen Systems, BOLT micropower generator is the first commercially available piezoelectric-based energy harvesting solution. Further according to Robert Andosca, CEO of MicroGen, BOLT is well positioned to power wireless sensor nodes and systems and will help eliminate the need to replace dead batteries in these systems or help extend the life of lithium batteries 6-fold in WSN applications. MicroGen projects that its device could be useful in a number of applications ranging from automotive to civil infrastructure and military applications. In addition to BOLT060 and BOLT120, MicroGen also provides BOLT050 and BOLT100 with a vibrational resonant frequency of 50 Hz and 100 Hz, respectively. MicroGen has the ability to custom build BOLT micropower generators for vibrational resonant frequencies ranging from 30 Hz to 1.5 kHz. MicroGen is partly funded by New York State Energy Research and Development Authority. MicroGen carries out its product development at Cornell Nanoscale Science and Technology Facility.