No More BatteriesHeart-powered pacemaker could one day eliminate

battery-replacement surgery

Raunaq Singh | @rsingh__

The basics of how the human heart and conventional

pacemakers work

traditional pacemaker

Pacemakers• Power requirement of modern pacemakers

has now reduced to one microwatt.

• The size of the pacemaker is 42mm X 51mm X 6mm

• The batteries take up about 2/3rd of the size of the pacemaker’s generator.

• A pacemaker’s batteries last for only 5 - 7 years.

[1]

Piezoelectric Pacemakers

• Piezoelectricity generated from mechanical vibrations in our chest area could be used to power the pacemaker.[1]

• M. Amin Karami and Daniel J. Inman, Phds from the Aerospace Engineering Dept. of University of Michigan have proposed have proposed this concept.[6]

Piezoelectricity• An electric charge accumulates in certain

solid materials in response to mechanical stress.

• Common piezoelectric materials :-Natural crystals - quartz, rochelle salt, topazSynthetic crystals - Gallium orthophosphate, a quartz analogic crystal

• The most common piezo electric material used is Lead zirconate titanate. [7]

Piezoelectric Pacemaker• Vibrations produced by our beating heart our

used to generate electricity to power the pacemaker

• The piezoelectric energy harvester is placed in the vicinity of the heart

• The vibrations in the vicinity of our heart are estimated using ultrasonic velocity measurements performed by Kanai H. in a paper published by IEEE.

[1]

Piezoelectric energy harvester

• A unimorph zigzag geometry piezoelectric structure is used so that:- its size remains small- the natural frequency vibrations it responds to our within the range of our heart’s frequency- it is designed to have high strength

• The researchers target reducing the power source area by 50%.

[1]

Specifics• the zigzag energy harvesters have 27mm long

beams

• brass is chosen as the suitable substrate material

• the piezoelectric material used is Lead Zirconate Titanate (PZT-5A)

• the piezoelectric layer is attached to the substrate using poly-epoxide.

• the thickness of the PZT-5A used is 0.01 in (254um). [1]

Specifics• The maximum power harvested corresponds

to 1800 um substrate thickness if excited at nominal heart rate.

• The power output from such structure is 10 uW, which is 10 times the power requirement of a pacemaker

• This type of piezoelectric energy harvester is called linear energy harvester and it harvests energy in response to 39 Hz oscillations. [1]

Limitations & Further improvements• Linear harvesters work well only at a specific heart

rate, so heart rate changes in patients with an irregular heart rate could prevent them from harvesting enough power.[4]

• To overcome this limitation in patients who have a relatively irregular heart rate, nonlinear broadband energy harvesters are used.[4]

• A nonlinear harvester uses magnets to enhance power production and make the harvester less sensitive to heart rate changes. The nonlinear harvester generated enough power from heartbeats ranging from 20 to 600 beats per minute to continuously power a pacemaker.[5]

• Karami told the Daily Mail that, “What we have proven is that under optimal conditions, this concept is working.” I don’t know that that would be enough to put my life on the line. But if the device proves itself and manages to pass all the regulatory lines of defense, it could be a real boon to heart patients.And it’s a large market opportunity for device-makers, too: some 700,000 people get a pacemaker or defibrillator each year, reportedly.[2]

Citations• [1] Powering pacemakers from heartbeat vibrations using linear and

nonlinear energy harvesters by M. Amin Karami and Daniel J. Inman, Applied Physics Letters, 23rd January 2012

• [2] A Heartbeat-Powered Pacemaker - MIT Technology Review, Nov 7 2012

• [3] New device could allow your heartbeat to power pacemaker - American Heart Association, Nov 04, 2012

• [4] UMich researchers closer to producing piezo-powered pacemaker - The American Ceramic Society, March 05, 2012

• [5] No More Batteries: Piezoelectric Pacemaker Powered By The Heart - Science 2.0, Nov 4, 2012

• [6] Heart-powered pacemaker could one day eliminate battery-replacement surgery - University of Michigan News, March 02, 2012

• [7] Piezoelectricity - Wikipedia Article