They have developed a device made from a piezoelectric material, a material that releases an electrical voltage when under stress.
Previous attempts to source energy in this way have resulted in linear devices that can only harvest energy from one source. "The ideal device would be one that could convert a range of vibrations instead of just a narrow band," said Samuel Stanton, graduate student in Duke University's Pratt School of Engineering, in the US.
"Nature doesn't work in a single frequency, so we wanted to come up with a device that would work over a broad range of frequencies," Stanton said. "By using magnets to 'tune' the bandwidth of the experimental device, we were able verify in the lab that this new non-linear approach can outperform conventional linear devices."
The team placed moveable magnets of opposing poles on either side of another magnet on the device. By changing the distance of the moveable magnets, the researchers were able to "tune" the interactions of the system with its environment, and thus produce electricity over a broader spectrum of frequencies.
"The results suggest to us that this non-linear approach could harvest more of the frequencies from the same ambient vibrations," said Brian Mann, assistant professor of mechanical engineering and materials sciences.
"More importantly, being able to capture more of the bandwidth makes it more likely that these types of devices could someday rival batteries as a portable power source."
The resulting device could capture enough energy from the motion of walking to provide sufficient electricity to power an implanted device, such as a pacemaker or cardiac defibrillator. On a larger scale, sensors in the environment or spacecraft could be powered by the everyday natural vibrations around them, Mann added.
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Date Published: November 10, 2009
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