How the body could power pacemakers and other implantable devices

["Dave Farber" <farber () gmail com>]

Begin forwarded message:

> From: Dewayne Hendricks <dewayne () warpspeed com>
> Date: June 10, 2018 at 5:52:21 AM PDT
> To: Multiple recipients of Dewayne-Net <dewayne-net () warpspeed com>
> Subject: [Dewayne-Net] How the body could power pacemakers and other implantable devices
> Reply-To: dewayne-net () warpspeed com
>
> How the body could power pacemakers and other implantable devices
> By Charles Q. Choi
> Jun 9 2018
> <https://www.washingtonpost.com/national/health-science/how-the-body-could-power-pacemakers-and-other-implantable-devices/2018/06/08/16d287b0-5559-11e8-a551-5b648abe29ef_story.html>
>
> In “I Sing the Body Electric,” poet Walt Whitman waxed lyrically about the “action and power” of “beautiful, curious, 
> breathing, laughing flesh.” More than 150 years later, MIT materials scientist and engineer Canan Dagdeviren and 
> colleagues are giving new meaning to Whitman’s poem with a device that can generate electricity from the way it 
> distorts in response to the beating of the heart.
>
> Despite tremendous technological advances, a key drawback of most wearable and implantable devices is their 
> batteries, whose limited capacities restrict their long-term use. The last thing you want to do when a pacemaker runs 
> out of power is to open up a patient just for battery replacement.
>
> The solution may rest inside the human body — rich in energy in its chemical, thermal and mechanical forms.
>
> The bellows-like motions that a person makes while breathing, for example, can generate 0.83 watts of power; the heat 
> from a body, up to 4.8 watts; and the motions of the arms, up to 60 watts. That’s not nothing when you consider that 
> a pacemaker needs just 50 millionths of a watt to last for seven years, a hearing aid needs a thousandth of a watt 
> for five days, a smartphone requires one watt for five hours.
>
> Increasingly, Dagdeviren and others are investigating a plethora of ways that devices could make use of these inner 
> energy resources and are testing such wearable or implantable devices in animal models and people.
>
> Good vibrations
>
> One energy-harvesting strategy involves converting energy from vibrations, pressure and other mechanical stresses 
> into electrical energy. This approach, producing what is known as piezoelectricity, is often used in loudspeakers and 
> microphones.
>
> To take advantage of piezoelectricity, Dagdeviren and colleagues have developed flat devices that can be stuck onto 
> organs and muscles such as the heart, lungs and diaphragm. Their mechanical properties are similar to whatever they 
> are laminated onto, so they don’t hinder those tissues when they move.
>
> So far, such devices have been tested in cows, sheep and pigs, animals with hearts roughly the same size as those of 
> people. “When these devices mechanically distort, they create positive and negative charges, voltage and current — 
> and you can collect this energy to recharge batteries,” Dagdeviren explains. “You can use them to run biomedical 
> devices like cardiac pacemakers instead of changing them every six or seven years when their batteries are depleted.”
>
> Scientists are also developing wearable piezoelectric energy harvesters that can be worn on joints such as the knee 
> or elbow, or in shoes, trousers or underwear. People could generate electricity for electronics whenever they walk or 
> bend their arms.
>
> Body heat
>
> A different energy-harvesting approach uses thermoelectric materials to convert body heat to electricity. “Your heart 
> beats more than 40 million times a year,” Dagdeviren notes. All that energy is dissipated as heat in the body — it’s 
> a rich potential source to capture for other uses.
>
> Thermoelectric generators face key challenges. They rely on temperature differences, but people usually keep a fairly 
> constant temperature throughout their bodies, so any temperature differences found within are generally not dramatic 
> enough to generate large amounts of electricity. But this is not a problem if the devices are exposed to relatively 
> cool air in addition to the body’s continuous warmth.
>
> Scientists are exploring thermo­electric devices for wearable purposes, such as powering wristwatches. In principle, 
> the heat from a human body can generate enough electricity to power wireless health monitors, cochlear implants and 
> deep-brain stimulators to treat disorders such as Parkinson’s disease.
>
> Static and dynamic
>
> Scientists have also sought to use the same effect behind everyday static electricity to power devices. When two 
> different materials repeatedly collide with, or rub against, one another, the surface of one material can steal 
> electrons from the other, accumulating a charge, a phenomenon known as triboelectricity. Nearly all materials, both 
> natural and synthetic, are capable of creating triboelectricity, giving researchers a wide range of choices for 
> designing gadgets.
>
> “The more I work with triboelectricity, the more exciting it gets, and the more applications it might have,” says 
> nanotechnologist Zhong Lin Wang of Georgia Tech. “I can see myself devoting the next 20 years to it.”
>
> [snip]
>
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