Worldbuilding Stack Exchange is a question and answer site for writers/artists using science, geography and culture to construct imaginary worlds and settings. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

We have successfully put 37 trillion nanobots the size of a red blood cell into the experimental group test subjects' willing participants' bloodstream, but without a power source, the nanobots clot up the bloodstream and don't carry oxygen cause mild side-effects that last more than 4 hours. EnerThrive© Inc. is committed to avoiding lawsuits providing our customers with the best possible experience, so we've reached out to the uneducated scum public for free intellectual property ideas of how to power the nanobots.


What would be a feasible way to power trillions of nanobots? These nanobots would live in the bloodstream, so they never should run out of power. Powering the bots includes both acquiring the power, and storing the power. Assume that the nanobots mostly use technology available today (except scaled down, of course), though there can be some minor-moderate advances in a few areas. The nanobots (and their power) should last at least a whole lifetime. Whatever power source also must be very cheap (because you need 37 trillion of it). A handwavium-boson-tachyon nanofusion engine should be a last resort. Also, no magic.

share|improve this question
    
Do they have to be mechanical in nature? Bio-engineered bacteria or other cells of a similar sort would need food, rather than power. This would be easier to suppy to your <s>test subjects</s> willing participants – Miller86 Feb 15 at 13:15
1  
@Miller86 Bacteria causes too many problems. What if there's a mutation? How do you control them? IMHO, it makes the question a bit too broad. Also, your immune system would probably kill most of them. – Daniel M. Feb 15 at 13:18
4  
Fair enough, although you may want to bear in mind on that scale the immune system would probably not take too kindly to nanobots, unless appropriately "cloaked" - chemically or otherwise. – Miller86 Feb 15 at 13:24
2  
Body heat could theoretically work but it may be hard to find a heat gradient (a heat sink is necessary). – Kiran Linsuain Feb 15 at 17:10
2  
Have you read the paper on respirocites? That seems to be what you're describing, and the glucose engine is part of the basic design. – JDługosz Feb 16 at 23:55

17 Answers 17

up vote 58 down vote accepted

Why, glucose and oxygen!

These have significant benefits:

  • Fuel cells are already available technology, so you can get electricity from pretty much anything that would normally burn. Should be possible to adapt it to work on glucose all right
  • You already want oxygen and glucose in blood.
  • Both are pretty easy to supplement.
  • No real need to store energy, as human body is doing it's best to keep oxygen and glucose levels constant - so it should be always available in healthy test victims subjects.

Side effects may include

  • Increased appetite
  • serious light fatigue if nanobots are under heavy load
  • blood vessels clog dizziness if patient is really hungry
  • instant death complications in subjects suffering from diabetes

Nothing you can't work around, but all may make interesting plot hooks.

Wouldn't it be a problem in veins, there is no oxygen in them?

  • Without energy nanobots can't carry oxygen. So they can't carry oxygen if there is no oxygen. That's a big... Wait.
  • Blood makes full round around the body in about a minute. That gives us 30 seconds unpowered. Not a big deal.

  • Fuel cell membrane indeed works as short term storage anyway.

  • Last but not least, there is enough oxygen and glucose to power up blood cells. Not their full functionality, but see first bullet, we don't need it. We only need bots to have fuel economy at least as good as cells they replaced and no problem.

As King-Ink mentioned, making them work on fat could be nice. Additional selling point, certainly. Just be silent about the way you let more fat into bloodstream (and side effects of this), and don't ever mention increased failure rates due to higher complexity of your fuel cells.

Or make them dual-fuel. Double the failure rates energy available!

share|improve this answer
8  
If you make them work on fat they could have a added selling point for the obese. Weightloss and obligatory milkshake drinking. – King-Ink Feb 15 at 14:17
1  
could they, at least, visit my belly? – King-Ink Feb 15 at 14:25
3  
@King-Ink: and anyway it's all the same to your body's energy economy. If the nanobots are using a lot of glucose then that's more or less equivalent to your own cells using glucose: initially the liver will convert glycogen to glucose in order to make up the deficit, eventually if you're not consuming the calories that the nanobots are using then fat will be released from adipose tissue. – Steve Jessop Feb 15 at 14:26
1  
Or you could just have some special nanobots whose sole/main purpose is to travel to your belly and "burn" fats. That way the regular bloodstream nanobots, that most of the time are nowhere near any appreciable amount of fat, wouldn't be carrying around fat-using machinery they don't need. Would also keep you nice and warm. – Steve Jessop Feb 15 at 14:27
2  
There is plenty of oxygen in veins. Near sea level, the typical consumption of oxygen (by the body) during a full circuit of the blood stream is less than one-fifth of the maximum oxygen concentration. (The vein tissues have to get oxygen, too!) – Jasper Feb 16 at 23:14

Piezoelectricity

Since plasticity is a required function of these nanobots and the heart is going to be compressing them at a steady rate, piezoelectricity is your very best friend here. As it's generated very simply, there are no moving parts required, no batteries to charge, no complex chemicals, all you have to do is stay alive and they'll keep running, they'll run even better when you're running.

Side effects are minimal, possibly a little extra strain on the heart.

share|improve this answer
7  
Interesting answer, but TANSTAAFL - if energy comes from pressure changes, that come from heart beat, then you are effectively powering nanobots thorough heart, putting an additional strain on it. But it wouldn't really be "little". It'll be watt for watt. Nominal power seems to be around 2W. So every watt of nanobot power is significant strain on heart. (You stil got +1 from me because I like your idea, I just think you underestimate side effects) – Mołot Feb 15 at 15:25
2  
You want watts in these things? They're only 7μm varying to 3μm under compression.The actual load on the heart is relatively small, power will mostly come from vibrations from movement. One of the conditions from the previous question was that they had to match normal blood cell behaviour, plasticity etc. – Separatrix Feb 15 at 15:32
5  
37 trillion of it is pretty big number. Blood cells use 10^(-12) W/cell. 10^(-12) W * 37 trillion = 37 watts. So yes. I want watts there unless this tech will be hundreds of times more efficient than blood cells. – Mołot Feb 15 at 15:36
2  
On a nano-scale, pressure isn't a "steady" thing. It's just a statistical variation in the collisions between the nanobot and surrounding large/small molecules, as they all move around in brownian motion – Peter Cordes Feb 15 at 18:58
2  
@PeterCordes There are papers like "Piezoelectric Energy Generation and Harvesting at the Nano-Scale", so it may be difficult but at least was worth considering. – Mołot Feb 15 at 19:38

Since all the other ones I thought of have already been used, I had to go find something else.

The one I was going to use was piezoelectricity (though I didn't know what it was called!) And I think that would be the most useful for machines of this size.

However, my contribution to this would be Inductive charging.

It uses an electromagnetic field to transfer energy between two objects.

It is just starting to be used for more commercial electronics to charge batteries. Some want to get cell phone chargers this way, it would eliminate the little port and cover.

So someone could wear an armband or wristband (watch?) and the little nanobots would pick up a charge as they flow through that part of the body. It would even be possible to walk through an arch and charge the whole body in one go. Then the arm band would just need to keep a trickle charge going. enter image description here

share|improve this answer
23  
That just gave me an image of a bed that people sleep on to charge. "I only stay at hotels with EnerCharge beds." – Daniel M. Feb 15 at 14:38
    
@DanielM. I was thinking about that after I posted my answer! – bowlturner Feb 15 at 14:38
2  
It would be enough to wear a simple magnetic armband (passive permanent magnets) and let the blood stream carry the nanobots through the magnetic field. This induces an electric current in the nanobots. – Michael Feb 15 at 22:06
1  
Why not? Unless your arm falls asleep and the nanobots run out of power ;) I think there are some watches which use a magnet bumping up and down in a coil to charge through movement. Same principle. – Michael Feb 15 at 22:11
1  
@bowlturner they are getting energy from movement, not from magnet. – Mołot Feb 15 at 22:49

There are a few options here. The simplest would probably be tiny batteries in the nano machines. You would wear some sort of charging pack (for example maybe around your wrist like a watch) and it would use magnetic fields to charge nano machines as they flow through in the blood stream.

Another option would be for them to have organic reactors on board, for example maybe they can take sugar or fat or oxygen or something else similar out of the blood and use that to power themselves. Keep in mind that even large numbers of nanobots would still use a tiny amount of power. You might even use them as a dieting aid :)

share|improve this answer
    
I love this answer because Tim B doesn't need any magic or technology of the future: today! but rather a scaling down of things. Power robots with batteries. Power small ones with small batteries. +1 – Caleb Woodman Feb 16 at 3:13

Kinetic energy seems like the most obvious solution. Your heart is constantly pushing the blood throughout the body, supplying kinetic energy that can be harnessed by the nano machines. Automatic watches use this exact principle: they're powered by the regular movement of your arms. A tiny oscillator within the nano machines would move back and forth over tiny magnets, converting the kinetic energy to electrical power.

share|improve this answer
    
As people have pointed out on user16295's answer, this essentially pulls the necessary energy from the heart, which adds quite a bit of extra strain on it, which could lead to all sorts of complications – Kevin Wells Feb 16 at 23:53
    
@KevinWells The conversion of kinetic energy imposes no extra strain on the heart that isn't already expended by the very presence of the nanobots to begin with. If they're in the bloodstream, they already need to be moved. We'd simply be recapturing that energy. (For example, the breaks on a Tesla car convert kinetic energy back into electrical energy, but the initial energy was spent in the necessary action of moving the car.) – Dan Gayle Feb 17 at 0:09
    
@DanGayle they would only have kinetic energy against an obstruction (Tesla brakes work against road surface). Whlist floating around in the blood they have potential but not kinetic energy, other than minor collisions as discussed above under Piezoelectricity, which are unlikely to supply much. – Andy Dent Feb 17 at 8:31
    
@DanGayle The only way to convert kinetic energy into electric energy is to slow the thing down, which would slow down the flow of your blood overall, which then requires more work from your heart to get it moving again. There is no such thing as a free lunch in physics, so whenever you are extracting energy from something, try to figure out where that energy actually comes from. – Kevin Wells Feb 17 at 16:20
1  
@DanGayle That is a very interesting idea, and not one that I was considering. I missed the point of your last comment about the movement of our limbs, I thought you were referring to the watch. I suppose that if you could create something that was powered by the motion of your arms and legs that that would work, though you may then run into a problem if the person is stationary for too long (like when they sleep or if they have a desk job) – Kevin Wells Feb 17 at 23:45

By using a Fractal Rectenna EM energy can be harvested from ambient RF fields and even possibly at nano scales, IR light (which is very good as living things tend to be warm) or even the WiFi system.

It could be built into the structure of the nanobots themselves or a larger 'command' nanobot could be used as a recharging station and information distribution point.

share|improve this answer
3  
I'm sorry to burst your IR light idea, but the second law of thermodynamics says you can't extract heat energy from an environment that is at the same temperature as you. How do you intend to keep the nanobots cold enough to not emit as much IR as they are receiving? – Jan Dvorak Feb 15 at 14:22
2  
@JanDvorak Provided they circulate like ordinary blood cells, oscillating between the colder extremities and warmer core about once a minute, I foresee no issues, the nanobots will cool in the extremities and absorb IR when in the core. – Scott Downey Feb 15 at 14:31
    
Maybe not heat - but IR photons could be converted just like visible light ones could be. PV conversion of IR photons to electricity wouldn't be very efficient though. – Jim2B Feb 15 at 23:21
    
Also certain frequencies of photons should be able to penetrate to any layer of the body - the problem is, if it penetrates our bodies so freely, could the nanobots absorb them? Low frequencies would be too big for them to absorb. High frequencies would tend to cause <s>cancer</s> minor adverse side-effects. – Jim2B Feb 15 at 23:25
    
so they couldn't go in the slow moving stream, like the capillaries – njzk2 Feb 16 at 2:31

I just want to point you to a more comprehensive reference:

You are asking for a method of Energy Harvesting that can be used on a nano-scale within the human body.

Low-power solution

Personally, I'd vote for piezoelectricity as user16295 suggested if you do not need much power. The idea of using piezoelectricity to power RFID tags has been presented a decade ago and printable piezoelectric sensors are already in use today.

As they can be mass-produced and there is promising research in using cheap sustainable materials this technology can be expected to become even more affordable in the near future.

High-power solution

If you take a look in the more distant future biofuel cells might be a way to generate more energy than piezoelectricity would allow for. However, I don't think this is feasible on a nano-scale just yet.

Depending on the use case you could also implant a bigger device using a biofuel cell to generate energy and charge your nanobots using induction.

share|improve this answer

Solar power is a possibility. They can charge up when blood is close enough to the surface of your skin, and hold enough power to continue operating the rest of the time. Downside is they wouldn't work very well at night or in places where the sun don't shine if you catch my drift. But all of the blood goes back to the heart in the end, and if the bots are smart enough, they can choose which arteries to go down such that those most in need of a recharge are sent to the parts of the body that receive the most light (e.g. head, hands).

Beach-goers and nudists would get extra power due to their degree of exposure. If the nanobots are built to combat things like skin cancer, their very means of powering themselves would counteract the dangers of over exposure to the sun. Not recommended for those who live in cold climates, especially past the Arctic/Antarctic circles during their respective winter months.

share|improve this answer
    
Although possible, I don't think this would be very practical. You'd essentially need a PV cell included in each nanobot. But only nanobots at the skin AND not covered by clothing would receive any light. This would leave most of them inert. – Jim2B Feb 15 at 23:23
    
@Jim2B - Well, there are "trillions" of them, so they don't all need to be active all the time. And as small as they are, they probably don't need all that much power. It may even be possible for them to transfer power from one bot to another. With that many of them, a complete circuit could be made from the exposed parts of your body all the way down to the deepest recesses if needed. – Darrel Hoffman Feb 16 at 15:21
    
Might do better with (low power) microwaves and/or IR. Better tissue penetration and the frequencies may still be high enough to be absorbed by the nanobots. – Jim2B Feb 16 at 15:38

The best answer is to not use anything that needs charging. Nano bots also mean adding tiny amounts of heat generating sources, which may add up to something possibly harmful. So what can you do? Engineer cells to emit the signals your nano bots would. The cells would feed off natural resources. And Of course, you'd turn off the ability to replicate and all other abilities that would cause the engineered cells to harm other cells.

share|improve this answer

Install wiring within the body in a pattern similar to blood vessels. Larger cables split repeatedly down to capillary-sized nano-wires. Nanobots plug themselves in anywhere along the line to juice up, and store energy in chemical, miniature-battery form.

At the macro scale the user can use any of a number of methods to provide their nanobots with electricity. They could use the installed bio-fuel cell that burns glucose and oxygen when other power sources are unavailable, or plug in a power cable from a wall wart (AC-to-DC power adapter) or a battery pack to avoid having to eat 5 meals/day.

Bonus Feature: desk workers could plug in a power cable and run the bio-fuel cell in reverse. They'd never need to take a break to eat lunch.

How do you implant these wires without painful, invasive, body-wide surgery? By having the nano-bots build it, of course! Install the power core in a normal, macro-scale surgery, then let the nano-bots build out the power supply system over the course of a few weeks. The victim test subjects will have to take vitamin+mineral+metal supplement pills to provide the nano-bots with materials not normally available in the human body.

During the construction phase, any nano-bot which goes too far from the power supply so it can't get back before running out of power will need to self-destruct* so it doesn't cause blood clots minor side effects.

* Self-destruct does not mean explode. (That would cause spontaneous human combustion major side effects.) Nano-bots would self-destruct in the same sense that dead cells self-destruct; they stop functioning and break down into biologically-harmless pieces.

share|improve this answer

My original idea did involve inductive charging, but then I got a brainwave.

How much power do your nanobots need? If its of the order of a few microwatts per nanobot, the cells themselves produce enough bioelectricity for the purpose. The tissue fluid - cytoplasm potential difference can be harvested as a Galvanic power source.

The total power requirement would come out close to 10^7 watts for all the microbots, so this isn't a feasible long term solution. However, this is a good solution for powering the nanobots during the "dark period" of inductive charging.

37 trillion nanobots would be harvesting power from over 50 trillion normal epithelial cells, so that isn't a problem, but moderation is favourable as draining too much power from the cells will upset cellular transport mechanisms, (dropping the resting membrane potential below -70mV could become a problem even with non-excitable cells).

You could use a fine electrode injected momentarily into an epithelial cell of the blood vessel lining to get power. Not for long, though. And not at all with nerves or muscles, as they are excitable and the potential drop caused due to the nanobot power harvesting could cause involuntary contractions (spasms/tetany).

Side effects... Don't you have willing test subjects? Use them and find out!

share|improve this answer
    
37 trillion of nanobots is pretty big number. Blood cells use 10^(-12) W/cell. 10^(-12) W * 37 trillion = 37 watts. Assuming nanobots have similar needs, it's orders of magnitude bigger than your assumption. – Mołot Feb 17 at 11:05
    
I meant a few microwatts per nanobot, that I shall make clear in the answer. Also, it is not that this idea is not feasible as the body does produce approximately 200 watts of bioelectricity (read it somewhere, don't remember the source). – Tamoghna Chowdhury Feb 17 at 11:07
    
Yea, I didn't downvote nor anything. I just posted numbers to get a realistic starting point. Please clarify if you can :) – Mołot Feb 17 at 11:09
    
@Molot I edited some stuff. – Tamoghna Chowdhury Feb 17 at 11:13

Thermal Diodes. Let the test subjects natural body heat be directly converted to electricity to power the nanobots . If you have the tech to produce these nanobots in the first place, lowering the operative temperature on the thermal diodes to the range available in the human body and cranking up the efficiency should be simple. As a side effect if the subject develops a fever they may be able to help lower the body temperature while gathering a charge. They will have to be programmed to gather the charge slowly so as not to induce hypothermia of course.

share|improve this answer
1  
won't work. How big temp difference can you get at nano-scale? In water, perfect medium for making temperatures even? It's not about difference between your foot and your heart, it's about difference at distance equal to one cell diameter. – Mołot Feb 15 at 22:58
1  
to be very clear: you need a difference of temperature between the 2 sides of whatever thermoelectric generator you have. you can't just extract electricity by arbitray lowering the temperature. – njzk2 Feb 16 at 2:34
    
However, each nano-bot only needs a very small amount of energy. This could possibly work. – Kiran Linsuain Feb 16 at 17:36

Some of the answers already touched on this, but I feel it has not been fully addressed:

As food breaks down energy is released as electrons. The cells store that energy as ATP and NADH molecules. Over time, if there is excess energy, sugars and fats are formed as longer term storage of energy.

Here is an article that explains the process in details

The bots can use those molecules and do what cells do. If that is not enough the bots can help the digestive track to more fully absorb the energy from the food that was eaten.

The guinea pigs... I mean the willing participants, would have to eat a lot, but the benefit is that they won't gain any weight (and most likely lose some).

share|improve this answer

What you are describing is a respirocyte, first described in 1998.

§3.1 summarizes Power (bold mine):

Onboard power is provided by a mechanochemical engine that exoergically combines glucose and oxygen to generate mechanical energy to drive molecular sorting rotors and other subsystems, as demonstrated in principle in a variety of biological motor systems. Glucose engine design — possibly involving a ballistic turbine driven by rotor-combustion ejecta operating near ~1000 atm — is a critical research issue. Drexler [2] estimates engines can be designed to operate at >99% efficiency. However, since natural cellular metabolic pathways using the glycolysis and tricarboxylic acid (TCA) cycles achieve only 68% efficiency, we adopt a more conservative 50% efficiency for the present study. Sorting rotors absorb glucose directly from the blood and store it in a fuel tank. Oxygen is tapped from onboard storage.

The power system is scaled such that each glucose engine can fill the O2 tank from a fully empty condition in 10 seconds, requiring a peak continuous output of 3 x 10−13 watts. This pumping rate, ~108 molecules/sec for the gases, is not diffusion limited because [86] maximum diffusion current J = 4 p R C D ~ 109 molecules/sec, for gas diffusion coefficient D ~ 2 x 10−5 cm2/sec for O2 and CO2 in distilled water at 20 °C [87], C = 7.3 x 1022 molecules O2/m3 (arterial blood), and R = 0.5 micron. Taking Drexler's estimate of 109 watts/m3 for mechanochemical power conversion [2], a glucose engine could measure 42 nm x 42 nm x 175 nm in size, comprising 108 atoms (~10−18 kg).

The glucose fuel tank is scaled such that one tankful of fuel drives the glucose engine at maximum output for 10 seconds, consuming 5% of the O2 gas stored onboard and releasing a volume of waste water approximately equal to the volume of the glucose consumed. Such a fuel tank can measure 42 nm x 42 nm x 115 nm in size comprising <108 atoms (<10−18 kg), hold ~106 glucose molecules and be filled using ~10−3 sec of engine output. Power is transmitted mechanically or hydraulically using an appropriate working fluid, and can be distributed as required using rods and gear trains, or using pipes and mechanically operated valves, controlled by the computer.

share|improve this answer

Nano guides are required spread around and connected to a power source by magnet, so then, they can transfer energy to all the nanobots, nano guides are also necessary for many other tasks like, transfering new orders, updates, signals etc. This nano guides can be placed in only one position so they act as GUIDES.

share|improve this answer
    
Welcome to the site! Could you define what "nano guides" are? I haven't heard that term before. What are they, how do they work, and how does the "connect by magnet" work to get them power? What kind of external device would be needed? – Dronz Feb 18 at 1:44
    
Nano guides is my design I have been working for some time. I am happy to share the info with anyone on this. A nano guide or leader is like a boss of minions, so you only need to establish communication with the leader, the leader once inside the patient it will act as a nexus in between the nanobots and the device that control the movement or functions running on the nanobots. This nano leader will be bigger and with different magnetic outputs in order to send signal to the others to do different things. Each nanobot should have 3 functions at least so we can start combining. – user3595142 Feb 22 at 0:51
    
A good example can be for threatening BD (Bipolar Disorder) in order to control the Serotonin and Dopamine with other acids in brain, you can choose to block, release dopamine or Serotonin to create the perfect mix in brain to manipulate Moods. I have a DB model for this. To communicate nanobots to respond to the model I have, you can use low frequency magnet fields to repel or attract, nanobots can have multiple functions in an atomic level can be powerful. Having an orquestrator inside the PT can help him to not depend on other devices to control the nanobots. – user3595142 Feb 22 at 1:01
    
Thanks! That makes sense as a control hierarchy, but as for the question here, what is the mechanism by which the nanobots continue to have power to do what they do? – Dronz Feb 22 at 6:02

A graphene nanotube coiled around a gold shaft and tuned through a joule theif circuit and tuned to the radiation resulting from the big bang should not only function as a constant power supply but also as the system clock for any process routines...presuming you are using the superconductive perfect graphene as the basis of your nanobots.

To add details the cosmic radiation ever present permiates through every spec of matter in existence to my knowledge even lead does not have the ability to filter it out...the function is not so different in other proposed induction coils such as those used to charge cellphones only as we would be dealing with graphene the superconductor the energy needed would be so small the oscillation of this ever present frequency should drive the heart of the machine.

share|improve this answer
    
This is a little short. Could you try to expand on that a little bit? How would this system generate power when it's floating in someone's blood stream, for example. – AndreiROM Feb 18 at 18:12

What about your brain, you could use it as a power source. Think of the electrical charges that pass through your body every second powered form your brain. When they become low on charge maybe it could be programmed into them that, that is where they need to go. If they could somehow harness the natural electricity provided by the human brain it may be possible to always keep them at charge. They Wouldn't need a permanent place to be recharged, as the human body is always healing itself...

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.