Sole-Long To Dead Batteries, Shoe Insert Charges Electronics While You Walk

Apr 5, 2016

The Sole Power shoe insert can provide 30 minutes of talk time on an iPhone 6 via 60 minutes of walking.
Credit Melinda Roeder / 90.5 WESA

Anyone attached to their phone knows how frustrating a dead battery can be. But if you need a quick charge, look no further than your shoe.

Pittsburgh-based tech startup Sole Power has created a shoe insert with a battery pack that can charge small electronics such as flashlights, radios and cell phones. Sole Power was founded by Carnegie Mellon University graduate Matthew Stanton, who said it all started with a simple idea for a class project.

“We were walking around campus all the time, back at Carnegie Mellon, and everyone had a cell phone and by the time it would be 6 p.m. and you were looking to meet up with people, you couldn’t reach anybody because everyone’s cell phone was dead,” Stanton said.

And that sparked an idea. 

He said he wondered if it was possible to convert all the energy created from walking into pedestrian power. So Stanton and his classmate Hahna Alexander began designing a prototype. A couple weeks and a couple hundred dollars later, they came up with a shoe insert.

“So they’re actually insoles, which means they work in a variety of types of shoes and boots,” Alexander said. “And every time you step down, it converts that linear motion in your steps rotational and it spins a tiny generator embedded inside the insole.”

Sole Power was founded by a Carnegie Mellon University graduate who wanted an easy way to charge a cell phone.
Credit Melinda Roeder / 90.5 WESA

The first goal was to create a self-charging shoe that could light up, making it safer to walk around campus at night; but they quickly realized greater potential.  After some adjustments to increase power, they attached a small battery pack with USB outports suitable for charging.

“A dead battery sign is pretty much the most universally hated symbol and it means something different to lots of different people,” Alexander said. “So, if you’re a hiker, maybe you’re in trouble and you get one more phone call before your phone dies. Or maybe it means something much less serious like you can take a picture at the top of a mountain.”

But there was another problem to resolve: size. The first couple of prototypes were bulky and uncomfortable, so mechanical engineer David Matten got to work shrinking them. 

“Yeah, size is a really big constraint for us,” Matten said. “We’ve had issues where five-thousandth of an inch will make a different between something working well and not working at all.”

So just how much energy do we generate by simply walking?

“It depends on how much you weigh, how fast you’re walking, how your gait is,” Alexander said. “So some people walk mostly on their heels, others on their toes. Right now our average is about 30 minutes of talk time on an iPhone 6 for an hour of walking.”

The team is already working on ways to make the insoles even more powerful, more durable, and last longer. Its research got a big boost when they signed a contract with the United States Army.

“So a typical soldier will carry about 20 pounds of backup batteries on a single day mission and that’s multiplied by how many days they’re on the mission,” Alexander said. “So, the Army is actively looking at solutions – energy harvesting solutions – to reduce the amount backup weight that soldiers have to carry every day.”

Sole Power will begin taking preorders online this month. Each pair is customized by shoe size and cost about $200.

In this week's tech headlines: 

  • Some video gamers are going to have to wait longer than expected for their Oculus Rift virtual reality headsets. Oculus rushed their new product to market months ahead of competitors and began taking preorders in January. But now the company said there’s been an unexpected component shortage.  So customers who were supposed to receive the headsets last week, will have to wait until at least mid-April. The headsets retail for around $600 and Oculus said it will reimburse shipping costs.
  • Carnegie Mellon University is teaming up with the U.S. Department of Defense to design new fibers and fabrics that can be integrated into products like protective armor and even workout gear. It’s a $75 million project aimed to boost the country's textile manufacturers. One of the goals of the project is to create ways to embed sensors and other electronics in clothing.