US Academics Use Piezoelectric Strip to Power Pacemaker

A US research team has demonstrated a printed piezoelectric circuit which can be fitted inside a living body.

A prototype of the piezoelectric strip was used to power a cardiac pacemaker that has been successfully implanted into anesthetised sheep and cows according to research published in January 2014.

PZT
The device was designed by academics at the University of Illinois and University of Arizona. It contains a strip of the piezoelectric material lead zirconate titanate (PZT) encased in biocompatible polyimide.

The strip generates power as the test animal's heart muscles contract and relax.

When attached to an optimal point on the right ventricle, the prototype was able to generate 0.18µW/cm². It will be possible to increase the output in future models by stacking multiple layers of the 500nm PZT ribbons on top of each other. This will easily put it in the range of modern human cardiac pacemakers which can operate on a little as 0.3 µW.

The next step for the piezoelectric device will be to test its charging performance in an animal subject over time and whether there will ultimately be an immune system response.

Saving lives
In-body charging would remove the need to replace the batteries of an implanted medical device. For a standard pacemaker this currently needs to be done every six to ten years. Money is not the only saving, it is estimated that 3% of deaths for pacemaker users occur during surgery to replace batteries.

A discrete charging solution, like the PZT strip, could be a key component for a range of plastic electronic circuits designed to be implanted in humans for monitoring and therapeutic functions.

If it could be combined with another recent demonstration, which will allow printed electronics on shape-memory polymer to be implanted and resist rejection in soft body tissues, a raft of new medical applications will be possible.