Seebeck Effect - Self powered LED implants
I’ve been trying to read up on areas of the human body that exhibit enough of a temperature difference to create a seebeck effect which could be used to power an LED implant.
Obviously there is a difference near the skin between interior and exterior temperature but that sounds challenging to utilise without visible surface implants.
Rather than a generator in a single position, a longer setup could be used say between the fingers and wrist where I would anticipate the wrist is hotter.
Anyone care to weigh in on this?
Obviously there is a difference near the skin between interior and exterior temperature but that sounds challenging to utilise without visible surface implants.
Rather than a generator in a single position, a longer setup could be used say between the fingers and wrist where I would anticipate the wrist is hotter.
Anyone care to weigh in on this?
Comments
Long story short: not feasible.
I'm pretty sure we had thermoelectric generators in the ever-so-big implant-power thread. Anyway here's the quick rundown you'r probably interested in:
Assuming a healthy fully grown adult body somewhere between male and female and slightly less obese than the american average you get:
The body converts about 90 to 110 Joule into movement/heat every second.
Given the body's surface area of about 1.8m² that's 100W/1,8m² that's gives about 55W/m². Or about 5,5mW per cm². A typical LED runs at somewhere between 1.9 and 2.somethingish depending on the color, and eats 20mA. So an LED takes 40 to 60mW input power.
So without any loss in a world where physics wouldn't ruin your day you'd only need maybe a 4x4cm big area of skin to power an LED.
And now for the bad news: Physics. Thermoelectric elements are heat engines and their efficiency is limited by a stupid thing called Carnot's theorem which basically means the bigger the temperature difference , the better your conversion efficiency. So with a warm body of 37°C on the inside, and a topmost frozen-skin layer with 0°C we'd get (37+273-273)/(37+273) (all in °C) which is about 12% maximum efficiency. Bumps the required size of the thing up to 10x10cm (with your topmost skin layer frozen solid). And this does not include losses from the heat conduction, the rather quite poor efficiency of the thermoelectric element itself etc etc.
Using a shaking movement, magnet and coil will provide a lot more power and is way less inconvenient.
Even with the difficulties involved, I think that power sources are the #1 obstacle to many biohacking projects. I think metabolic power generation would be ideal, especially combined with maybe ambient power generation through fractal antennas. Not having an organ system to move this power where it needs is unfortunate, but could be designed.
@Cha0sthe0rist battery, inductive charging, done. No need to rely on stuff that's not existant, not field proven, or not affordable.
Coating is number 1. Circuits are pretty easy these days.
@ThomasEgi that's fair, perhaps my perspective on the matter was a little skewed.
so is mine. Having a background in electrical engineering problems on that front seem to be less difficult to figure out.
I posted about some cut-down inductive charging circuits last year: https://forum.biohack.me/index.php?p=/discussion/2064/powering-and-communication-with-implants-build-from-scratch/p1
Really not that difficult to build, given you can calculate things and got access to basic electronic-dev equipment.
I'd bet some chemistry guy would claim coatings to be easy.