IMEC has fabricated an energy harvester to generate energy from mechanical vibrations by using micromachining technology. Output power was as high as 40 micro-Watts, which is the range of required power for wireless sensor applications. The harvester comes with a model that can be used to optimize the device during design.
Energy harvesters, which transform ambient energy into electrical energy, are of great value for situations where batteries cannot be easily replaced. A typical example is autonomous sensor networks that are spread over large areas or placed in locations that are difficult to access. Vibration harvesters in general make use of electromagnetic, electrostatic or piezoelectric conversion to generate electrical power.
IMEC developed, modeled and characterized a miniaturized vibration harvester based on a piezoelectric transducer. The device consists of a piezoelectric capacitor formed by a Pt electrode, a PZT layer and a top Al electrode. The capacitor is fabricated on a cantilever that supports a mass on its tip. As the harvester is subjected to oscillations, the mass causes the piezoelectric layer to be stretched. By doing so, it induces an electrical power when an electrical load is connected to the device.
To optimize the proposed device concept, a model was generated to estimate the output power for a given design. The output power of the fabricated devices can be maximized by maximizing the quality factor Q (through a low parasitic dissipation) and the coupling between the electrical and mechanical part (GEMC. generalized electromechanical coupling factor).
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