In the future, lifesaving pacemakers, defibrillators and other implantable
devices might be powered not by limited-lifespan batteries but by the limitless
energy generated by the movement of a patient's own bodily organs, new animal
The idea is to safely stitch electricity-converting materials directly onto
the surface of the heart, lungs and diaphragm to draw upon the endless power
that is naturally produced as each organ continuously contracts and relaxes.
The result would be a never-ending supply of juice that researchers say will
eliminate the current need for invasive, risky and expensive
Operations to replace batteries
"Once a pacemaker's battery is depleted, you have to perform an operation
to replace it," said study co-author John Rogers, a professor in the
departments of bioengineering and materials science and engineering at the
University of Illinois. "The same is true of many kinds of devices, and
it's obviously not ideal.
"Over the years, people have been thinking a lot about many different
possible ways we could harvest power from the body itself," Rogers added.
"Some have looked at glucose [breakdown], others at the exploitation of
tiny temperature changes in the body. We focused our effort on the energy
generated by motion. And now, by working with living cows, sheep and pigs, we
have been able to demonstrate that this can work."
Rogers and his colleagues discussed their findings in the issue of the
journal Proceedings of the National Academy of Sciences.
Power harvested from the body
To explore motion-produced electricity, the study authors relied on the
dynamics of "piezoelectricity". This refers to the ability of certain
materials to build up an electrical charge when exposed to pressure.
In this case, the material at hand was lead zirconate titanate, or PZT, a
so-called "nanoribbon" substance that is film-thin and completely
flexible and bendable.
The research team placed strips of PZT on thin, flexible plastic. The end
result, Rogers said, was plastic-wrap-like sheets with a total thickness
equivalent to about one-third of a piece of paper.
The energy-harvesting sheets were then sutured onto the surfaces of the
hearts, lungs and diaphragms of living cows, sheep and pigs, whose organs are
about the same size as human organs.
Such PZT attachments did not appear to interfere in any way with the normal
function of the targeted organs, Rogers and his colleagues said. And after
linking the PZT sheets to both AC/DC conversion devices and micro-batteries,
the researchers were able to capture and store enough electrical power to meet
or exceed the requirements of standard implantable devices.
More testing needed
"This won't be available for practical use anytime soon," Rogers
said. "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 anaesthetised."
Rogers said more research is needed before the device can clear regulatory
hurdles. One concern is how well the body reacts to a foreign material.
"I don't see any biocompatibility issues so far, and I am
optimistic," Rogers said. "But we have to show long-term viability in
animals before they ever go into humans. 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
Predicting the outcome
Although the findings of the new study appear promising, scientists note
that research involving animals often fails to produce similar results in
For his part, Daniel Inman, chairman of the department of aerospace
engineering at the University of Michigan, said his own work in the field has given
him a firm belief that body-generated energy will eventually be a reality with
broad practical applications.
"The technology is certainly viable," Inman said. "Yes, there
are risks. For instance, with the pacemaker example, we clearly have to know
for certain... the device won't fatigue and fail any faster than a
"And biocompatibility has to be a top priority," he said,
"because we all know the body can reject things, and we have to work to
address any such concerns."
"Having said that, there's no question that there's certainly a need
and demand," Inman said. "As anyone who has to undergo an operation
every seven or 10 years to have a dying battery replaced knows, surgery is a
big deal. If you tell them this method would mean they don't have to do that
anymore, that is something they definitely want."
Picture: Defibrillators from Shutterstock
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