Batteries not included

Research at two universities could create pacemakers that do not need to be removed to have their batteries replaced, sparing patients from invasive medical procedures. Polymer-based nanogenerators could convert mechanical energy from a beating heart into an electric current that can be used as a power source.

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, crystals that generate an electrical current when deformed under mechanical pressure, are commonly used in disposable lighters and mini speakers.

Led by University of Illinois engineering professor John Rogers, director of the Seitz Materials Research Laboratory, the team created bendable piezoelectric strips capable of attaching and conforming to the soft and slippery surfaces of internal organs and flexing with their movement. Canan Dagdeviren, a member of the Rogers lab, led the fabrication efforts for the piezoelectric constructs. Prototypes were then brought to the University of Arizona (UA) for further research and testing.

Under the rhythmic contraction of the heart muscle, the strips bend and relax, enabling the piezo-electric 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, the researchers say.

“Our advancement is to make the tiny power generators conformal so they move with living tissue, particularly when attached to internal organs,” says Dr. Marvin J. Slepian, director of interventional cardiology and professor of medicine at the UA Sarver Heart Center with a joint appointment in the university’s department of biomedical engineering.

Slepian has had a long-standing collaboration with Rogers.

“Many of the therapeutics we use today go beyond drugs and instead are device-based,” Slepian explains. “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,” Slepian continues. “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.”

While this study involved using the piezoelectric generators to harvest power from the heart, they also could be used to harness the motion of the lungs or other organs. Ultimately, the goal is to make medical devices that no longer need batteries.

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.

The research collaboration included Dr. Zain Khalpey, who joined the UA Department of Surgery last year as an associate professor and director of clinical and translational research.

Because of the needs for this technology in applications related to cardiovascular devices, the two universities filed a joint patent.

Adapted from a press release from The University of Arizona.