IMEC, together with its sister company IMEC-NL at the Holst Centre, has fabricated an energy harvester to generate energy from mechanical vibrations by using micromachining technology. Output power as high as 40 micro-Watts was obtained, thereby achieving 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 and IMEC-NL developed, modeled and characterized a miniaturized vibration harvester based on a piezoelectric transducer.
For an input vibration with a resonance frequency of 1.8kHz and an amplitude of 180nm, a maximum experimental output power of 40 micro-Watts was measured. This comes well in range of the amounts of power needed by wireless sensor applications, such as the pulse-oxymeter developed earlier by IMEC and IMEC-NL, operating from the Holst Centre in Eindhoven, The Netherlands.
“After demonstrating a battery-less pulse-oxymeter fully powered by a thermal scavenger, this is another encouraging result that brings us closer to seeing miniaturized scavengers in real-life applications,” said Bert Gyselinckx, program director IMEC-NL at the Holst Centre. “We believe that first of such devices will see market introduction about 5 years from now and will become mainstream by the end of next decade.”
The device consists of a piezoelectric capacitor formed by a Pt electrode, a PZT layer and a top Al electrode. This 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).
IMEC is seeking industrial partners for further joint research on the development and application of energy harvesters for wireless sensor nodes.
IMEC is a world-leading independent research center in nanoelectronics and nanotechnology. Its research focuses on the next generations of chips and systems, and on the enabling technologies for ambient intelligence. IMEC’s research bridges the gap between fundamental research at universities and technology development in industry. Its unique balance of processing and system know-how, intellectual property portfolio, state-of-the-art infrastructure and its strong network of companies, universities and research institutes worldwide position IMEC as a key partner for shaping technologies for future systems. IMEC is headquartered in Leuven, Belgium, has a sister company in the Netherlands, IMEC Nederland, concentrating on wireless autonomous transducer solutions, and has representatives in the US, China and Japan. Its staff of more than 1500 people includes more than 500 industrial residents and guest researchers. In 2006, its estimated revenue (P&L) was EUR 227 million.
About the Holst Centre
The Holst Centre was set up in 2005 with support from Economic Affairs of the Netherlands and the Flemish Government and is located on the High Tech Campus in Eindhoven. The center is the creation of IMEC (Flanders, Belgium) and TNO (The Netherlands) and will grow into an international recognized open R&D institute that develops generic technologies and technology platforms for autonomous wireless transducer solutions and systems-on-foil. The activities on wireless autonomous transducer solutions in the Holst Centre are run by IMEC-NL, the sister company of the Belgian research center IMEC. Interaction and cooperation with both academia and industry, including small- and medium-sized enterprises, enables the Holst Centre to tune its scientific strategy to the long-term corporate strategies of its partners. A beneficial transfer of technology to the industry is guaranteed and market requirements can be anticipated.