Implanted TEG

Back to the topic of an implantable storage device I was thinking about power. I'm deciding that the whole battery life issue isn't that big of a deal. Admittedly, I've never had a battery expire. I have had devices with expired or nearly expired batteries, but never that were mine from original purchase to the time the battery expired. So...

Charging, Qi standard wireless would be fastest I think, but I like the idea of a secondary (slower) charging system that doesn't require an external device. A motion based generator, like you'd find in some flashlights, or a Thermoelectric Generator (Peltier Generator). The motion based generator is probably too big to use in an otherwise small implant, so I'm leaning toward the TEG idea, for which the power generation is very dependent on the temperature difference between the "hot" and "cold" sides. Based on some tests I've done with IR thermometers, the surface temperature of skin tends to vary from 96 degrees, down to ambient air temperature, for me anyways, depending on the place in the body, with the neck or head just below and behind the ear being the warmest from my checks.

Optimally I believe an area with a concentration of blood vessels such that it's quite warm would've best to intercept the heat as it makes its way to the surface of the skin.

Anyone have any thoughts on that? Assuming the surface skin directly over the generator doesn't absorb the heat from surrounding skin, I think that could work fairly well. Of course I imagine that charging could take hours, even a couple days to achieve a full charge in a fairly small capacity battery.

What I want to do is purchase two of these:

One to immediately test to ensure it works perfectly (so I know if it's me that breaks it) and then dismantle it and figure out how small it can be made. Then purchase a small Perrier TEG from here:;jsessionid=E51DDE0F15326A332BEA6A776802499A.p3plqscsfapp004

As well as possibly a smaller battery than the built in one (though I have a few and might just use one of those).

Once I'm satisfied with my build I plan on enlisting someone else to assist with costing and bioproofing it, and subsequently testing, but for the time being my questions are just about opinions on the use of the TEG for charging. I figure, if a TEG can power an LED from a thumb's heat, they should be able to charge a small battery in a decent amount of time.


  • Interesting idea. I could imagine the usb setting up a wireless network could drain the battery rather quickly, but on the other hand just storing files doesn't require any power at all. If this where possible i could imagine a similar thing could be done with other small wireless gadgets.

    Qi charging of implants sound's like a really useful thing. Just did a quick search on this and cant seem to find anything. Any big drawbacks to this? Or just not that much battery using implants?

    I dont really think a TEG would work in this case for the following reason:
    As far as i'm aware lithium-ion battery's do not require a minimum charging current or voltage. But i believe the latter could reduce the run time. Constantly charging the battery at a low rate and only incidentally discharging at a faster could work i think. I think the real problem would be getting the TEG to produce any substantial power at all.
    As you stated yourself it requires a difference in temperature. I once bought a cheap larger one of some Chinese website. It could actually charge a phone if attached to a  boiling pan and attaching a heat sink to the other end. Even then it would over time lose most of its potential because of the heat sink slowly heating up. Wood stoves using this principle exist, which can be used to charge usb devices and such.

    All current information i could find on using body temperature for powering a TEG were cases of external use. And all of them only producing small amounts of power. The skin acts as a buffer, keeping everything internal warm. I don't think the temperature just under the skin, and a small bit further inside is going to be that much of a difference. In a best case still a lot worse then when using it on top of the skin.

    That being said, i would be interested to know how much a implanted TEG could generate. 
  • Indeed the necessity to implant a TEG just for testing (and then not being able to easily measure output levels) is a bit of a challenge. I didn't know that about said batteries requiring a minimum input to actually charge. I can believe it though. I wonder if power could be stored up slowly in some sort of small capacitor and the released into the battery in chunks periodically. I figure, if it works, it would take a couple days to charge completely, hence my thought to incorporate a Qi charger if it doesn't take up too much space.

    As far as Qi chargers in other implants, the Qi Standard itself has only been around for several years and is only been adopted into common consumer devices over the past two or three. Currently there's not much in the way of high power implants (high power, where low power would be like a pace maker or something similar).

    I figure that the finished device would have a small magnetic (Reed) switch to toggle between "on" and "charging". I was aware of how devices generally aren't designed to be both charged and discharged simultaneously.

    Anyways, I plan on starting with a couple of the low capacity 32 GB ones since I'll likely end up breaking them in the process. Then getting the biggest 200 GB model for implanting. I wouldn't cost it myself. If I manage to get a device built as I'd like I'll probably ship them (the two smaller models I start with) to someone here for coating and coating tests. Once successful I'd proceed by making the same modifications to a 200 GB model and getting that coated. I'm still undecided about implant location, I won't decide for sure until I see exactly how big the finished device is. My current thought is in the sort of cavity behind the clavicle on either shoulder (when relaxed, the muscle there is sunken into the shoulder and so the skin gets pulled in, which suggests to me that you could easily implant something of a decent size that wouldn't be uncomfortable or (possibly) terribly visible under most circumstances). I'll return to discussing that when the device is closer to implanting time.

    My biggest concern is how the coating could hold up under the heat generated internally by the electronics, particularly the battery when charging via the Qi charger.

    I'll be honest, im not terribly excited about implanting something that isn't completely my own design, but I'd rather implant a product made (mostly) by a relatively large company that (although wouldn't warranty it in that condition) would have done extensive testing and I'd feel confident it wouldn't spontaneously stop working due to a software problem. I had also considered a tiny Android device, which would be capable of doing what I needed, and a bit more, but wouldn't be as small and (being implanted) I wouldn't have access to physically plug the device into a computer to fix software issues that may occur.

    As for any "enhancing" or "practical" implant, my thought is that it needs to be able to last at least 5 years. After which time, if it malfunctions or the coating wears down or I opt for an upgrade, its fine.
  • Sorry, i should have worded that a little differently. As far as i'm aware there is no minimum input required for the battery. But charging with a very low voltage could drastically reduce the total amount of power stored in the battery.
  • I see. Good to know. (About the batteries, I was surprised to find I'd misread that.) Hurricane Matthew somewhat heavily affected my area here, had no power for the past two days. Once power's back I have some things to take care of (getting things going again with the things that make me money) and then I should be getting around to purchasing some of the hardware involved. Starting with the low capacity version of the storage device.

    Traditionally Qi chargers work with a "unidirectional" communication method to tell the charging pad to stop drawing power from whatever it's plugged into when the battery is full. This is achieved by varying the amount of power the battery (by which I mean the Qi receiver connected to the battery) draws from the charging pad, supposed to make things more energy efficient, otherwise it'd be like you were always charging something, but when there was no receiving device a larger amount of power would just be sent into the air (sort of). I'm debating whether the extra hardware required to make that communication work is worth it, since I literally have to place a charger on my skin I figure there's no chance of me forgetting to unplug the charger when I'm done and wasting electricity.

    Opinions on that?

    Also, I've realized one reason to consider implanting sites during the design phase, it affects which if the 6 sides of the main device I place my added components on. (The reed switch to control the 1 button this thing has, the Qi receiver, and the TEG. And from my experience, batteries are never soldered directly to circuit boards so I can probably relocate the battery to a different side of the device if it makes the shape better for implanting.) Considering my "behind the clavicle" idea, any other implanting locations? I figure it's a little too big to go in the arm, due more to muscles needing to move under the skin as well, not so much because of the bulk bulging the skin, but I'll get more exact measurements when I'm working on that. Basically, should go for thin and spread out, or stack all the components on top of each other so it has the least horizontal surface area, but probably would be twice the height it would be otherwise?
  • Just going to leave this here: Link
  • @TheGreyKnight Thanks for that, that's why we have discussions, so people can throw in handy things that none of the rest of us know of.

    Also, power's finally back on after the hurricane. Yay! (Outage lasted 60 hours, give or take half an hour.)

    I was planning on (and mentioned the idea in the thread about brain augmentation) getting an Android Wear powered watch to perform similar modifications with (charging systems, though one of my candidates already has Qi built in). I thought this would be great for in the forearm just above the wrist, could connect via Wifi to the drive and allow me to view contents in a basic manner without any additional devices. However, something occurred to me today, in the past I've had problems with devices not "seeing" each other via Wifi on account of using different versions, (a/b/g/n) so I checked. The watches I was looking at all use B and G. The drive uses only N (which is newer than B or G). So, annoyed about that. Still think that drive is the best way to go though, just now trying to come up with alternative interaction methods that can be implanted. All the phones these days are monstrous, so they're sort of out the question. Anyone got thoughts on that?
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