An experimental device uses energy from a beating heart to power a pacemaker, signaling the next generation of implanted devices
--by Nina Lincoff
Human-powered medical devices sound like something out of a science-fiction movie where androids walk the street, cars hover above, and your daily cup of coffee is teleported onto your nightstand. (Now wouldn’t that be nice?) While those latter items may be a few years off, heart-powered pacemakers are closer than you'd think.
Findings from the study of an experimental device
that used energy from a beating heart to power a pacemaker was presented
on Sunday at the American Heart Association’s Scientific Sessions. This
type of energy-harvesting device uses piezoelectricity, or electric
charge that is generated from motion, the study says. The potential
impact of pacemakers that run on piezoelectricity is huge, largely
because it could decrease the number of surgeries required to change out
the batteries on traditional pacemaker devices.
Pacemakers are electrical devices that are implanted under the skin to help manage irregular heartbeats. There are two kinds of heartbeat irregularities, or arrhythmias, that pacemakers are used to treat: tachycardia and bradycardia, too fast and too slow, respectively. Today’s pacemakers generally consist of the battery and electronics that regulate arrhythmias and the leads that reach out to and communicate with the heart. The problem is that, eventually, the batteries must be replaced.
With piezoelectric-powered pacemakers, the extra surgeries needed to replace batteries won’t be required.
Researchers determined that nonlinear energy harvesters, or those that adapt to fluctuating heartbeats of 20 to 600 beats per minute (bpm), could continuously power pacemakers. Super-fit athletes rarely have a resting pulse below 50 bpm, and tachycardic rhythms are in the 200 bpm range. Nonlinear harvesters utilized magnets to streamline energy conversion and desensitize the device to changes in the number of heartbeats per minute.
human-powered devices sound cool, practically, they mean amazing things
for the lives of pacemaker patients. “Currently, pacemaker patients have
to go through surgeries every five to seven years to replace the
battery of their pacemakers,” says lead study author Amin Karami, a
research fellow in the department of aerospace engineering at the
University of Michigan. The proposed technology removes this need.
“Our nonlinear piezoelectric harvester (NPH) provides more power than the batteries,” says Karami. This also means that more capabilities can be integrated into future pacemakers—think more efficient and longer-lived devices.
Researchers turned to piezoelectric devices because they were looking for a mechanism that converts mechanical—in this case, vibrational—energy into electrical energy. And the flexibility of NPH devices makes them a reliable, sustainable substitute for batteries in pacemakers. “Among the transduction mechanisms, piezoelectric devices work best at the small scales,” Karami says.
Piezoelectric devices may power the next generation of pacemakers. Because of their durability, they may be a more attractive means of powering many implanted devices. Future study, says Karami, will look into applying this technology to commercially distributed pacemakers.
Researchers simulated human heartbeats using a “shaker” device in the laboratory, which produced vibrations that powered NPH devices. They tested 100 simulated sets of heartbeats across a range of rates and found that the energy harvester generated more than 10 times the power needed for a functioning pacemaker. NPH harvesters are about half the size of the batteries currently used in pacemakers, and implantation tests of these devices is the next step.
The wire's alive: In a report published in Advanced Functional Materials in 2010, researchers observed the effects of piezoelectricity on nanowires.