Two years ago, University of Wisconsin–Madison engineering researchers Tom Krupenkin and J. Ashley Taylor developed a device designed to harness the power of walking to charge an internal battery. Now, a new product called SolePower is looking to do the same thing, and its designers are turning to Kickstarter to bring it to the masses. The difference between this and other devices is that it comes in the form of a removable insole, so it can be used in different kinds of shoes.

SolePower comes in two parts: the power-generating insole and the battery. The user places the insole in their shoe and snakes the wire through the laces. The battery is then fastened around the ankle or to the top of the shoe. The wire is plugged into the battery, which then receives its charge simply from the user walking around as they would normally.

In testing, the company found that the battery would receive enough energy to fully charge an iPhone in anywhere from 2.5 to 5 miles (4–8km). The ultimate goal is locking down that two-and-a-half mile target, which will require further development.

The insole is waterproof and weather-resistant, which is obviously important, as no one would want to ruin their device if they were stranded in a rain storm. It's also rated to last for 100 million steps in simulated tests.

The company took its device to several podiatrists, as it is crucial that the insole not be so thick as to affect the way people walk.

The device can only accommodate users up to 350 lb (159 kg). Additionally, the smallest shoe size it can fit inside of is US women's size 8 (38.5 European).

It's early days for SolePower's Kickstarter campaign. The minimum pledge to secure a unit is US$100 for US residents and $120 for international backers.

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