This energy harvesting device is mounted on the outside of a sneaker, but such devices can also be e...

1. 'Smart shoe' devices could charge up as you walk
This energy harvesting device is mounted on the outside of a sneaker, but such devices can also be
embedded in the heel of a shoe to harvest energy as a person walks or runs. (Kelvis Ylli/IOP
Publishing)
The next generation of wearables could be powered by an unlikely energy source: you. Two new
devices that fit inside the sole of your shoe can harvest energy from your movements as you walk or
run, and then use that energy to power sensors and other electronics.
These devices could one day be used to create wearables that never need to be plugged into a
http://tanacre8741.webgarden.com/section-1/blog/selecting-uncomplicated-advice charger,
according to the researchers in Germany who developed them.

2. One of the devices, the "shock harvester," generates power when the heel of your shoe hits the
ground. The other device, dubbed the "swing harvester," generates power when your foot swings
forward as you walk or run. The harvesters can be connected to electronics inside your shoe that
track things like speed, movement and temperature.
"Both [devices] are based on the same principle -- electromagnetic induction," said Klevis Ylli, a
doctoral student at the Hahn-Schickard-Gesellschaft Institute of Micromachining and Information
Technology in Germany, and lead author of the paper outlining the new energy harvesting devices.
[10 Technologies That Will Transform Your Life]
Each device contains coils of wire and stacks of magnets. As the person wearing the device walks or
runs, the magnets move past the coils, causing the magnetic field within the coils to change. This
changing magnetic field creates a voltage, or charge, within the wire, which can then be used to
power whatever electronics are embedded in the shoe, Ylli told Live Science.
The swing harvester -- which is about 3 inches long, less than an inch wide and half an inch tall --
was originally developed to power a pair of self-lacing shoes. The device fits into the sole at the heel
of a shoe and weighs just under an ounce, which means that users hardly notice it when their legs
are swinging, Ylli said. The shock harvester is slightly bigger, and weighs about a third of a pound
and was developed for a different application -- providing power for an indoor navigation system.
Indoor navigation systems are an alternative to satellite-enabled GPS navigation systems, which
don't always work inside of buildings or in crowded urban areas. Used by firefighters and military
personnel, these indoor systems often utilize sensors to collect information about a person's location
and then transmit this data wirelessly to a central computer.
"For the indoor navigation system, there are sensors [accelerometers] within the shoe that
determine how fast you're moving, acceleration and the angles that your foot has traveled. And from
this data, the system can calculate the path that you have walked," Ylli said. A battery, also located
inside the shoe, is powered by the shock harvester, and keeps these sensors running.
In recent tests, Ylli and his colleagues connected the harvesters to a temperature sensor embedded
within the shoe of a study participant who was walking on a treadmill. The researchers found that
the person's walking generated enough electricity to power the temperature sensor as well as a
wireless transmitter inside the shoe that sent the temperature data from the sensor to a smartphone.
In the future, a similar setup could be used to transmit data from accelerometers embedded in a
shoe to a smartphone or tablet, Ylli said. Such a self-charging "smart shoe" would function much like
a fitness tracker, monitoring steps taken, as well as distance and speed.
"If you take a close look at the scientific http://www.newschool.edu/parsons/fashion-school/
environment, there are plenty of people working on these types of [harvesters] for shoes. I think
there is some interest there, and people have high hopes that harvesters will get better over time
and will be feasible for powering devices," Ylli said.
Going forward, Ylli said, he and his colleagues plan to optimize their harvesters to capture even
more energy from the human gait. A paper outlining their research so far was published Jan.14 in
the journal Smart Materials and Structures.

3. Editor's Note: This article was updated to include the proper weight of the swing harvester, which is
just under an ounce.
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