A new power scheme for
cardiac pacemakers turns to an unlikely source: vibrations from heartbeats
themselves.
Engineering researchers at
the University of
Michigan designed a
device that harvests energy from the reverberation of heartbeats through the
chest and converts it to electricity to run a pacemaker or an implanted
defibrillator. These miniature medical machines send electrical signals to the
heart to keep it beating in a healthy rhythm. By taking the place of the
batteries that power them today, the new energy harvester could save patients
from repeated surgeries. That’s the only way today to replace the batteries,
which last five to 10 years.
“The idea is to use
ambient vibrations that are typically wasted and convert them to electrical
energy,” said Amin Karami, a research fellow in the U-M Department of
Aerospace Engineering. “If you put your hand on top of your heart, you can
feel these vibrations all over your torso.”
The researchers haven’t
built a prototype yet, but they’ve made detailed blueprints and run simulations
demonstrating that the concept would work. Here’s how: A hundredth-of-an-inch
thin slice of a special “piezoelectric” ceramic material would
essentially catch heartbeat vibrations and briefly expand in response.
Piezoelectric materials’ claim to fame is that they can convert mechanical
stress (which causes them to expand) into an electric voltage.
Karami and his colleague
Daniel Inman, chair of Aerospace Engineering at U-M, have precisely engineered
the ceramic layer to a shape that can harvest vibrations across a broad range
of frequencies. They also incorporated magnets, whose additional force field
can drastically boost the electric signal that results from the vibrations.
The new device could generate
10 uW of power, which is about eight times the amount a pacemaker needs to
operate, Karami said. It always generates more energy than the pacemaker
requires, and it performs at heart rates from 7 to 700 beats per minute. That’s
well below and above the normal range.
Karami and Inman originally
designed the harvester for light unmanned airplanes, where it could generate
power from wing vibrations.
A paper on the research,
titled “Powering pacemakers from heartbeat vibrations using linear and
nonlinear energy harvesters,” is published in Applied Physics Letters.
