We've always known women can wield their breasts as a weapon, but did you know they're actually so powerful they can generate enough energy to keep an iPod playing?

Inspired by human-powered gadgetry, San Francisco-based freelance writer Adrienne So approached scientists on a whim to determine whether specially-created bras could harness and channel the energy of breast movement. And it turns out they can! (Read So's article from the UK's Indepedent here).

Moreover, this is not the first time such a novel idea has been explored -- back in May, lingerie giant Triumph International Japan [Images] launched a solar-powered bra in Tokyo, one powerful enough to keep an iPod running. However, So and her tech-minded friends back in the United States were looking to conceptualise a gadget that is not weather-dependent. Here's the scientific reasoning behind breast-powered gadgetry.

First on So's list was LaJean Lawson, a former professor of exercise science at Oregon State University and an expert on the subject of breast motion. Lawson works as a consultant for several prominent companies, helping them develop better sports bra designs. She explains that breast movement while walking, running etc takes place along three different axes -- from side to side, from front to back and up and down. Of the three, the most pronounced movements take place along the vertical axis, ie up and down. Naturally, the bigger the breasts, the more the momentum.

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The trick then, is to create a bra that provides both support and comfort while simultaneously allowing optimum movement of the breasts -- towards this purpose, it has to be elastic, non-cleavage boosting and low-necked.

Moving to the more technical side of things, So had a meeting with Professor Zhong Lin Wang of Georgia Tech. Professor Wang has developed a fabric created from tiny nanowires, which upon friction against each other convert mechanical energy into an electric charge. Each nanowire is 1/1000th the width of a strand of human hair and together they are woven into a fabric, one square metre of which can effectively produce 80 milliwatts of power, enough to run a small device. Surprisingly enough, the fabric is cheap to produce and most efficient.

So also examined another theory to power the bra, speaking with Larry Rome, biology professor at the University of Pennsylvania and the creator of the Lightning Pack. The Lightning Pack is a gadget that generates kinetic energy from the vertical displacement of a heavy backpack -- it is meant for mountain hikes and military exercise. As it turns out, with a few minor alterations this theory can also be applied to create an energy-generating bra.

Says So, "Maybe it's not very sexy to see breasts as a pair of batteries, but oil prices are so high, people are jogging to work. It may be time for breasts to start pulling their own weight."

In this photograph: A mobile phone is charged using Triumph International's solar powered bra.
Photograph: Junko Kimura/Getty Images