How could we use our own heart which pumps our blood, to potentially charge devices such as a cell phone?
First things first - that's putting a lot of strain on your heart. This system, however it works, will take the mechanical energy out of your blood. This means your heart needs to put more energy into pumping the blood around. While this is temporary since the heart will adapt and grow stronger, it's still going to be an issue.
In addition, the heart only provides about 1.3 watts. Phone chargers run at 2.5+ watts. The heart will have to triple its output to handle the energy of lower-powered chargers.
A better solution would be to run a charger off the user's blood sugar. Humans cosume power at an average of around 97 watts throughout the day. Most phones only take a few hours to charge, so that's going to be less than 5 watts average.
These batteries turn the motion caused by the pumping heart into electrical charge. It is not a perpetual motion machine because the signal from the pacemaker simply triggers the beat; it does not provide the energy for the beat.
I found news about this going back to 2008.
While the real world numbers don't quite line up (cell phones require much more power currently than the heart produces), this idea has already been transformed into a conceptual art piece entitled: Energy Addicts by Naomi Kizhner.
Is there any particular reason you'd choose the heart? There are much bigger and more powerful muscles in the body, that you can access without invasive surgery. I would suggest glutes and hamstrings are better suited. Look at Team New Zealand's recent America's Cup yachts for a real world example of using power from cyclists' legs to power the hydraulic systems of a boat. I've seen a similar setup connecting exercycles to generators to charge cellphones in an airport.
The main problem to solve is that our energy is chemical and it remains chemical for power conversion. Even our "low-voltage", information transfer systems (= nerve systems) works mainly on a chemical way: the nerves aren't cables transmitting electrons, rather sodium and potassium ions exchange place in the synapses.
Our "high power", i.e. energy transfer system happens in the blood. Blood sugar is used to transfer energy. Inside the cells, this sugar is used in the cytric acid cycle to convert ADP to ATP. The ATP moves our muscles while it converts back to ADP. But this happen deeply inside the cells.
Extracting energy from a living human, and convert it to electricity to drive an implant, means that we have to somehow convert the blood sugar to energy. It may be possible by some fuel cell-based technology.
If the implants to drive are inside the body, then from this point the system can be electronic.
If it is out of the body, you have to somehow put it through the skin. Note, cables sticking out from a human body are never healthy, the only way for a long-term solution if the skin remains intackt. Fortunately, there is already technology to transfer power by radio waves, here is an example to load phones without plugging them. The same could work also through the skin.
Note, making this on a way what doesn't poison you requires the development of a whole new medical technology. Although the research/development is on the way.
Its first human-friendly usage will be probably to drive artifical hearth implants.
In a dystopia it could be used also for many things, for example to
- identify people
- restricting them (Relevations 13:17: "It also forced all people, great and small, rich and poor, free and slave, to receive a mark on their right hands or on their foreheads, so that they could not buy or sell unless they had the mark, which is the name of the beast or the number of its name.")
releasing poison into their blood stream from wifi
Drawing energy from blood sugar is not necessary. The device itself could have used a sugar solution instead. The heart just moves food and oxygen to tissues and does not generate that much power.
Muscle power is the best. For that, you can harnrss leg power. A series of piezo electric crystals can turn changes in pressure into elrctricity. Yoi can mount them at the soles of your shoes and start walking
For a story idea you could do something along Faraday's law.
Instead of having the blood drive a rotor to generate power or tap into the sugar stores of the person, you could have a person injected with tiny magnets. These magnets theoretically would be pumped around the body without doing harm or putting a huge load on the heart. You then have coils of wire, either in a full body suit or localized to a sleeve/pant leg that would generate a current as the tiny magnets pass thru it.
Think of what happens when hydro power is made. The water spins a rotor that turns a giant magnet encased in copper windings. As the magnet moves it induces current in the wires. In this case the magnets flowing in your blood would simulate the spinning magnet and the body suit of jacket could act like the windings around the generator.
Yeah, there's no way it could happen as the magnetic fields would be so small but it's kind of a kewl jumping off point for a sci-fi premise. You could even write it with the iron in the blood being magnetized instead of having the addition of magnets.