Scientists are now one step closer to being able to harvest energy from everyday environmental vibrations, such as those made from household appliances, trains, helicopters flying overhead, or human movement, to power electronic devices like MP3 players, cell phones or even heart monitors.

While some such commercial energy-harvesting devices already exist, they are limited in that they can only exploit vibrations that have a narrow range of frequencies. For instance, there are devices which use vibrations from industrial pumps to power sensors monitoring the pumps' condition, but they work only because the vibrations are predictable and controlled.

But now researchers at the University of Bristol are working to develop new technology which can harvest energy from the small, fluctuating vibrations which occur haphazardly all around us everyday. If they succeed, it could mean that our portable electronic devices could charge naturally as we wander about.

"Vibration energy-harvesting devices use a spring with a mass on the end," explains Dr. Stephen Burrow, who is leading the team at Bristol. "The mass and spring exploit a phenomenon called resonance to amplify small vibrations, enabling useful energy to be extracted. Even just a few milliwatts can power small electronic devices like a heart rate monitor or an engine temperature sensor, but it can also be used to recharge power-hungry devices like MP3 players or mobile phones."

The team believes new technology can exploit a wider range of frequencies by harnessing the properties of non-linear springs, which are better suited to capture unpredictable vibrations as they occur naturally. 

Even better, devices which generate power from energy-harvesters will eliminate the need for batteries and reduce the potentially harmful pollution that comes from improper battery disposal. "Wider-frequency energy harvesters could make a valuable contribution to meeting energy needs more efficiently and sustainably," said Burrow.

The work is funded by the Engineering and Physical Sciences Research Council (EPSRC), and the researchers are hopeful that they can make their vibration-harnessing devices available for real-world use within five years.

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