"Current devices rely on batteries and therefore have to be taken out when the batteries need replacement," Marvin J. Slepian says. "Wouldn't it be nice to have a recharge and trickle system that can charge the batteries all the time? That is where we are coming from." (Credit: iStockphoto)

Pacemakers of the future: No batteries required?

Tiny power generators that convert the motion of a beating heart into electrical energy could eliminate the need for batteries in pacemakers and other medical devices.

As reported in Proceedings of the National Academy of Sciences, researchers successfully implanted polymer-based “nanogenerators” that convert mechanical energy from a beating heart into an electric current that can be used to power medical devices.

“This is the first time we were able to successfully and safely harness energy from mechanical biological motion and convert it into electricity with a realistic system that may in the future be used clinically,” says Marvin J. Slepian, professor of medicine and of biomedical engineering at the University of Arizona.

“The generated electricity could be used to power, recharge, or augment the battery capabilities of present battery-powered devices.”

The miniature devices consist of piezoelectric nanoribbons sandwiched between two thin layers that serve as electrodes, one made of titanium and platinum and the other made of chromium and gold. Piezoelectric elements are crystals that generate an electrical current when deformed under mechanical pressure and are used in many applications, such as disposable lighters and mini speakers.

The researchers, led by John Rogers, professor of engineering at the University of Illinois, created bendable piezoelectric strips capable of attaching and conforming to soft and slippery surfaces of internal organs and flex with their movement.

Canan Dagdeviren, a member of the Rogers lab, led the fabrication efforts for these piezoelectric constructs. The prototype devices were then brought to Arizona for further research and testing.

Trickle charge

Under the rhythmic contraction of the heart muscle, the strips bend and relax, enabling the piezoelectric crystals to convert the movement into tiny electrical signals. The devices used in this study were able to supply enough trickle charge—a steady stream of charging current at low rate—to satisfy the needs of a pacemaker.

“Our advancement is to make the tiny power generators conformal so they move with living tissue, particularly when attached to internal organs,” Slepian says. “Many of the therapeutics we use today go beyond drugs and instead are device-based. Think of pacemakers and defibrillators, ventricular assist devices and the Total Artificial Heart. All these and future devices require power.

“Current devices rely on batteries and therefore have to be taken out when the batteries need replacement,” he says. “Wouldn’t it be nice to have a recharge and trickle system that can charge the batteries all the time? That is where we are coming from.”

Lungs and other organs, too

While this study involved using the piezoelectric generators to harvest power from the heart, they could be used to harness the motion of the lungs and other organs, too. Ultimately, the goal is to make medical devices that no longer rely on batteries at all.

Extending battery life of implanted medical devices or eliminating the need for replacement altogether would spare patients repeated operations and the risk of resulting complications. Another possible application is in health monitors worn outside the body on the skin, which could be powered by this technology.

Because of the needs for this technology in applications related to cardiovascular devices, the University of Arizona and the University of Illinois filed a joint patent.

Source: University of Arizona

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