Dae-Hyeong Kim/University of Illinois

Scientists have been working for years on finding a way to harvest ambient energy continuously to power biomedical implants. The aim is to keep these vital implants running without the need for batteries, multiple invasive surgeries, and the like. From solar power to friction, to the energy produced when glucose breaks down or body temperature shifts, every rock is being turned over, looked under, and presumably considered for its potential as an energy source, too.

Now, bioengineers at the University of Illinois at Urbana-Champaign say they are closing in on this goal. Perhaps the holy grail of biomedical energy harvesting is using nearby organs; the energy generated by our own hearts and lungs is so, well, reliable. Our organs are our own little energizing bunnies, and they don't stop when it's dark, or we're not moving. Plus they have the distinct advantage of being in extreme proximity to the devices they would be powering -- pacemakers, defibrillators, and the like.

As reported Tuesday in the journal Proceedings of the National Academy of Sciences, a team of researchers have designed a kind of material and a type of technology that -- at least in the animals they tested, and for hours at a time -- appear to be both safe and effective.

Those are two big caveats, given that what works in other animals doesn't always translate to humans, and the approach needs to work for years if it's going to outperform current battery life.

Still, the team was able to stitch flexible and biocompatible electricity-converting material to the surfaces of the hearts, lungs, and diaphragms of living cows, sheep, and pigs without appearing to disrupt organ function.

For the experiments, they used strips of lead zirconate titanate (PZT), an ultrathin "nanoribbon" that -- thanks to the dynamics of piezoelectricity (using mechanical stress to generate power) -- is quite responsive to beating hearts, expanding and contracting lungs, and so on.

With these nanoribbons adhered to flexible plastic, the little energy sheets came out significantly thinner than the average piece of paper and ultimately captured and stored up to 8 volts of electricity -- enough to run most current implantable devices.

"This won't be available for practical use anytime soon," cautioned head researcher John Rogers in an interview with HealthDay. "We did show it works in the real world, but this was only in animal models. We have not yet operated any device for an extended period of time with the chest closed and the animals no longer anesthetized."

Rogers said, "So far we have shown it lasts for...half a day or so, but we will have to show that this method will generate sufficient electricity for at least a decade, because if not, there's no point."

Studying long-term biocompatibility in animals, Rogers writes in an e-mail, is his team's current focus. With human clinical trials likely years down the road, it's a bit early to uncork the champagne, but a future in which our organs power our devices is starting to look inevitable.