If good things come in small packages, then an energy harvesting device smaller than a penny must be really great.

Electrical engineers at the University of Michigan think so -- they've built a device that can harness energy from vibrations and convert it to electricity with five to ten times the efficiency and power of similar devices in its class. And it can fit on the end of your thumb.

One of the system's developers and chair of Electrical and Computer Engineering, Khalil Najafi said in a university press release, "In a tiny amount of space, we've been able to make a device that generates more power for a given input than anything else out there on the market."

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Specifically designed to covert the cyclical motions of factory machines into energy, this new vibration energy harvester will be used to power wireless sensor networks that will, in turn, monitor machines' performance and alert operators about any malfunctions.

Sensors currently used to do this job, although they are considered "wireless" because they transmit information over a wireless network, are still tethered to a power source plug or battery, drastically increasing their installation and maintenance costs.

Researchers say the device's self-contained, truly wireless power system will help cut those costs and increase its longevity.

"To be able to use the energy you harvest you have to store it in a capacitor or battery. We've developed an integrated system with an ultracapacitor that does not need to start out charged," said Najafi.

The packaged system operates at a vibration frequency to that which you might feel if you placed your hand on top of microwave oven while warming-up leftovers. When exposed to those kinds of vibration, the new harvester can generate more than 200 microwatts of power.

These devices, in theory, could be left in place for 10 or 20 years without regular maintenance. "They have a limitless shelf time, since they do not require a pre-charged battery or an external power source," said Erkan Aktakka, one of the system's developers.