A way to charge pacemakers using the heart’s own muscle | Hacker News Reader

A way to charge pacemakers using the heart’s own muscle

economist.com

52 pointsjkuria15 comments

Just wondering why wireless charging isn’t used? A pacemaker seems to use little energy so one overnight charge cycle should last for months if not years?

Though I admit that I haven't looked into the technicalities of how wireless charging works, I'd be concerned of passing radiation meant to hold enough energy to charge a battery through my own flesh. Even if it's somehow technically safe, you have to convince other people of that.

Wireless charging works with magnetic fields like a transformer (the primary coil being the wireless charging pad, the secondary being inside the device itself). There are people implanting magnets into their fingers and even after years I haven’t heard of any issues (the biggest risk with those seems to be the magnet shattering and small bits of it going in the blood stream, but nothing related to the magnetic field itself).

Move your head side to side in an MRI machine and you'll soon see that magnetic fields can have quite a considerable effect on humans...

(It causes all kinds of hallucinations - tingling body, seeing impossible shapes, a smell like something just died, and a feeling like you've just died)

They actually used to have them: https://www.theatlantic.com/health/archive/2014/02/who-kille...

https://jamanetwork.com/journals/jama/article-abstract/65488...

The short of it is that pacemakers last years already, and there's definitely an economic incentive to being able to charge thousands of dollars for a new device/battery, regardless of what The Atlantic would like to have you believe. The complications associated with pacemaker placement are high enough to warrant the risk reduction of only placing one once. You might argue that most patients don't need a pacemaker replacement since they're most likely going to die before needing one. What about the younger patient population of kids and young adults that need them due to arrhythmias or congenital heart disease?

There's maybe an argument to be made towards inconsistent battery life and not being sure when the batteries will fail due to lower and lower charge capacities. But pacemakers all have variable battery life due to each person's need for pacing. If someone needs constant pacing, they will probably need a replacement sooner. If it's every once in a while that they have an arrhythmia, then it will last far longer.

As said previously, they used to use these, but having an induction loop means you can never have an MRI as this would superheat the coil. I'd rather have the option of an MRI should I need it, and a daycase procedure to change my batteries.

You could use capacitive power transfer with a nonmagnetic electrode.

Happy to be corrected as I'm not an MR physicist, but I understand the problem is with any coils in the electronics rather than ferrous material.

Yes, magnetic flux induces a current in metal. It does not have to be ferrous.

Drop a magnet down through a copper or aluminum tube for a demonstration of the effect. (The induced current creates a magnetic field that opposes the magnet, slowing the fall.)

I’m not sure I see the problem. If the pacemaker kept the coil shorted except when charging, then even a fairly large AC field shouldn’t transfer much power or induce a problematic voltage. And an MRI is mostly a DC field, which seems mostly harmless.

Shorted, it would still create heat.

The AC fields in an MRI aren't that large.

You also don't have to short it. Leaving it open circuit with a charging circuit that can withstand large voltages is a much better bet.

Wouldn't this subtly sap the energy from the heart, making it just that little bit harder perform every beat do due the resistance of the piezoelectric strip? 10 microwatts seems little enough, but then how much does it take for the heart to beat? What % increase is this over normal functioning?

Google is your friend:

The heart has every other muscle in the body beat by producing between 1 and 5 watts

Thanks, so I guess that's basically smaller than the margin of error if you were sampling that

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