Graduate student Jian Shi and Materials Science and Engineering Assistant Professor Xudong Wang demonstrate a material that could be used to capture energy from respiration. Photo: University of Wisconsin-Madison |
The same piezoelectric effect that ignites your gas grill
with the push of a button could one day power sensors in your body via the
respiration in your nose.
Writing in Energy and
Environmental Science, Materials Science and Engineering Assistant
Professor Xudong Wang, postdoctoral Researcher Chengliang Sun, and graduate
student Jian Shi report creating a plastic microbelt that vibrates when passed
by low-speed airflow such as human respiration.
In certain materials, such as the polyvinylidene fluoride
(PVDF) used by Wang’s team, an electric charge accumulates in response to
applied mechanical stress. This is known as the piezoelectric effect. The
researchers engineered PVDF to generate sufficient electrical energy from
respiration to operate small electronic devices.
“Basically, we are harvesting mechanical energy from
biological systems. The airflow of normal human respiration is typically below
about two meters per second,” says Wang. “We calculated that if we could make
this material thin enough, small vibrations could produce a microwatt of electrical
energy that could be useful for sensors or other devices implanted in the
face.”
Researchers are taking advantage of advances in
nanotechnology and miniaturized electronics to develop a host of biomedical
devices that could monitor blood glucose for diabetics or keep a pacemaker
battery charged so that it would not need replacing. What’s needed to run these
tiny devices is a miniscule power supply. Waste energy in the form or blood
flow, motion, heat, or in this case respiration, offers a consistent source of
power.
Wang’s team used an ion-etching process to carefully thin
material while preserving its piezoelectric properties. With improvements, he
believes the thickness can be controlled down to the submicron level. Because
PVDF is biocompatible, he says the development represents a significant advance
toward creating a practical micro-scale device for harvesting energy from
respiration.