Piezoelectric generator creates power from shoes

Could walking or running generate enough energy to power your cell phone or GPS device? Dr. Ville Kaajakari has developed an innovative piezoelectric generator prototype small enough to be embedded in the sole of a shoe that's designed to produce enough power to operate GPS receivers, location tags and eventually, even a cell phone.

Harnessing kinetic energy is not without its challenges because it’s difficult to generate enough energy to power today’s applications. That’s where Kaajakari's invention - which has recently been featured in the MEMS Investor Journal - comes in.

The shoe generator uses a low-cost polymer transducer with metalized surfaces for electrical contact. Traditionally, ceramic transducers are hard and therefore unsuitable to use in shoes but Kaajakari's generator is soft as well as strong so it could replace a normal heel shock absorber without loss to the user experience.

According to Kaajakari, the new voltage regulation circuits can convert the piezoelectric charge into a usable voltage and combined with the polymer transducer give a time-averaged power of two milliwatts per shoe on an average walk - that’s comparable to lithium coin/button cells and enough to power running sensors, RF transponders and GPS receivers.

"This technology could benefit, for example, hikers that need emergency location devices or beacons," said Kaajakari. "For more general use, you can use it to power portable devices without wasteful batteries. Ultimately, we want to bring up the power levels up to a point where we could, in addition to sensors, charge or power other portable devices such as cell phones."

It will be interesting to see if Kaajakari’s inventiveness pays off – will shoes of the future be capable of charging mobile devices, and at the same time will our footsteps power the buildings we walk through?