Collect powers from human body via miniature implantation

Question

How much energy can we draw from miniature implanted device that collects energy from human body?

The goal is to design a type of implanted device in human body used to communicate over a distance, hence a reliable power supply is required. I am thinking about a combination of super-capacitor (examples: this) charged over human body to make this device self-powered. A possible energy source might be glucose.

Transmission over a long distance certainly requires a nontrivial amount of power, and being an implanted device makes this trickier. Currently there are nanoradios and this kind of design but the transmission range are not enough for long-range (say, over 100m or even over 1 mile) communications.

Now there are designs of bio-batteries, see for example this and this. But if the biochemicals, say glucose, are to be collected from human body, how much energy can a setup, implanted and “coupled” with human body generate and stored reliably? Also note that the device shouldn’t be too large: the size should be millimetres in scale.

I want the design to be scientific and based on current technology as much as possible. Hence I wonder if this is realistic, and if not, what are the current developments and potential difficulties to overcome?

A similar but not-the-same question.

Answer 1

For brief bursts we could.

It would be a great and happy deed if we could convert glucose from the body into enough useable electricity to power devices. Current batteries are invasive, requiring operations to replace or open power lines.

Unfortunately, as this notes, we don't yet have the technology to accomplish this. We can power very small and weak devices.

The enzymes required are fairly bulky, it's tricky getting them to reliably attach to polymers, oxygen can damage them, and most importantly, they only produce a trickle of power.

This experimental, not tested one produces 4mW/cm^-2.

A cellphone uses 20mW to 1 watt to call, and your device will likely draw a bit more since it needs to operate inside the body and penetrate the skin. So, have a chargeable battery, and you can have it make calls when needed. It won't be able to transmit constantly, without being very obvious and large, and the battery will drain fast if you do long range calls, but you can send messages.

Answer 2

Fortunately, the human body has a number of acidic locations and components. If you can tap into one of those (the stomach, for instance, with a pH comparable to commercial muriatic acid -- concrete cleaner -- and long term persistence), you can use a simple bimetal to produce a couple volts at several milliamps.

A potato battery, using strips of copper and zinc, will produce enough voltage and current to run a small electronic clock circuit from the juices of a potato, which is barely off neutral pH. A similar battery can be made with mere skin contact (using perspiration as electrolyte) with similar performance.

This kind of battery will use up the metal plates slowly, and selection of the metals may be critical (toxicity trades off against non-conductive reaction products), but it should be possible to draw a few milliamps continuous current for a couple years before corrosion of the plates reduces available current too much. Not enough to run a transmitter that will reach further than across a room -- but if you use that tiny current to charge a supercapacitor, you can run the actual transmitter (and whatever electronics create the signal it transmits) for seconds or minutes at a time and have enough reach that, on a quiet band, you might hear it at a block or more distance. And no future tech needed.

As an alternative that doesn't require replacing the battery plates even every few years, one could use an inductive "free power" setup -- at least as long as your subject won't be off-grid too much of the time. These systems use a loop antenna, transformer, and rectifier to pull "free power" out of the air -- in the form of electromagnetic radiation (radio, 60 Hz noise from power lines, etc.). In populated areas, these units can collect enough power for a fairly bright LED, which again would charge a supercapacitor enough to potentially produce several communication bursts per hour with usable range. And once again, no future tech needed (and no replacing the battery).