How fast can nanites work

Question

I've watched and read many SF stories which included nanites as a wonder weapon that can do pretty much anything. One such series is the Star Marine series by Ian Douglas.

Those books frequently quote the nano disassemblers as able to chew through a meter or more of exotic materials in several minutes.

I've always thought this was far too optimistic performance for nano-machinery.

I would agree with the theoretical capabilities of these devices (manipulate materials at the molecular level, transport materials from one location to another, etc.). However, manipulating materials at this scale does not circumvent the laws of thermodynamics or geometry.

From a thermodynamics perspective, they require a means of transporting instructions into the nano machines, usable energy into the system, transporting waste heat out of the system, and transporting materials out (for disassembly) or in (for assembly).

One great advantage of nano machinery is its potential ability to multiply capabilities. However, geometry restricts them to acting on an expanding spherical surface or a constant area surface (e.g. burrowing a tunnel).

Nano machines do not move quickly in relation to the macroscopic world. The world's first nano-machine race is expecting the machines to move 0.3 nm (0.000000003 meters) per each propulsive impulse and complete the 100 nm course in 36 hours.

What are realistic numbers for nano-machine performance?

1. How fast can they move?
2. How fast could they chew through a surface?
3. How fast could that build a macroscopic machine?

Answer 1

Forgive me if this carries on a bit. I tried to be comprehensive and remain brief. Comprehensive won out in the end.

I'll define a nanomachine as an artificial mechanical construct to the scale of a nanometer (10⁻⁹ m). I would assume anything measured under 100 nm could be considered "to the scale" of a nanometer. I'll use a 10 nm³ block as a general size for one of these nanomachines.

This size brings problems with mobility, precision movement, available construction materials, and versatility among other issues. I hope to cover those somewhat thoroughly in the answer.

Also, there are a wide variety of potential uses for these machines, so for simplicities sake I will assume you are dissolving bad guys and their stuff with these little destructo bots or building yourself something awesome with them.

Let's hit the first topic: How Fast Can They Move?

Often nanobots are introduced into an already existing system (usually aqueous) and serve a specific purpose within that system. I think comparing them to catalysts, or cells is a pretty good way to look at it. With that being said, almost nothing of this size moves on it's own in nature. The only self-propelling elements at this level that readily come to mind are viruses and bacteria.

The fastest speed I can find for bacterial movement is 200 microns/second (a micron is 10⁻⁶ m). For something 10 nm in size that is an incredible rate, though not a lot of overall distance. If your machines were to move on their own I arbitrarily think up to doubling this could still be considered believable. I submit a max self-propelling speed of ~400 microns/second.

However, systems themselves can move much faster. For example, the highest blood flow rate in the human body reaches ~180 cm/s. If you were to transport nanomachines in a similar way (expelling an aqueous solution through pressured valves) you would not have to bother with aiding their movement. This leads to the maximum speed that a thin aqueous solution (like an alcohol) could move. However, a reaction between the nanomachine and whatever it is eating needs to happen. I would again apply my arbitrary double rule to the blood flow rate since countless reactions happen while blood is moving. System propelled speed of ~400 cm per second. That gets you magnitudes greater in nanomachine speed.

Really, depending on the activity the machines are serving this could vary greatly. In essence, if you propel them, they are limited on the speed of the action they perform. Seeing as some chemical reactions are basically instantaneous (photo decomposition) while other physical reactions can take millenea (forming diamond), your variety is huge. I'll address this later though.

Now we move on to the next topic: How fast can they chew through something?

This is also pretty variable. There are so many surfaces they can chew through, from weak fleshy membranes which even mild chemicals destroy instantly, to a slab of tungsten that could possibly survive hitting the surface of the sun (for an instant). I'll keep any calculations vague to accommodate this.

I'll settle on magnesium metal since it is somewhat similar to aluminum (one of the most commonly used metals in modern manufacturing) and I found data for it without needing a lot of research. If you react magnesium (also aluminum) with Hydrochloric acid (HCl) it quickly dissolves. I found this data from an experiment measuring the rate of dissolution for magnesium in HCl. Powdered samples dissolved within 30 seconds when submerged in 3 molar HCl. It is possible to get higher molar acid, with a max around 12M. It appears that even with the strongest acid the max speed of dissolution floats around 15 seconds. These samples could be equivalent to maybe 1cm^3 of solid metal. Because solid metal has less surface area I'll use my magic doubler and give a value of 1 cm of metal surface dissolved every 30 seconds. Assuming we would only use nanomachines if they were more efficient than this acid, I'll double efficacy, leaving 1cm of metal dissolved per 15 seconds.

Now for your last question: How fast could they build a macroscopic machine? (if I got that right)

This is where I think nanomachines are a bit over-hyped. There are a couple of issues that we run into.

1. Where do the machines get the materials to build with?
2. How do these machines transport these materials?
3. How do you give detailed instructions to the machines?

With these questions in mind, I am giving a lazy answer: Don't use nanomachines for manufacturing

Right now we have so much available that is rapid, precise, and simple. Robots already pump out parts, devices, and machines at incredible rates. These parts are often on a macro scale, and when they are not, the process is still incredibly efficient. I mean, we have 3D printers that use lasers and gel to create anything that you can draft accurate to microns. It is fast and cheap and easy. I don't imagine that throwing nanomachines into the mix would make any aspect of manufacturing measurably better. The energy used to move materials with nano-machines and to give instructions to them seems too great to be of benefit.

Their use in creating drugs and chemicals is already pretty amazing. They can clean materials or products, treat materials for specific uses, and do a host of other things, but as far as building larger machines themselves goes, it does not seem too useful (please list any good uses you can think of in a comment).

Maybe a better idea would be like the nanobots found in Big Hero 6. Instead of building a macromachine, perhaps these nanomachines could combine their efforts and function as a macromachine collectively.

Altogether my answer comes to this:

• Self Propelled Speed: ~400 microns / second
• System Propelled Speed: ~400 cm / second
• Speed to eat metal: ~1cm / 15 seconds
• Speed to build a macromachine: Not useful to build macromachines

This is all very general, and depending on specifics could vary quite a bit. I hope that helps.

Answer 2

I think the key is to span scales. A multi-cellular organism like a whale is not a simple collection of cells like a biofilm or even a sponge. It has a circulation system where materials are pumped at speeds many orders of magnitude faster than the numbers you lament about, and the vescles and pump are made from those same cells. There are large scale systems made from organs, which are made from tissues, which are made from eucaryote cells. Continuing down, those complex cells are made from organelles and internal resource distribution systems, made from nano tissues (to come up with a term) which are masses of individual nanomachines.

So you don’t apply a mass of primitive procaryote-scale nanobots at a meter-scale task. You organize them into a series of successive systems at ever larger scales. Each system operates at a scale about the same as its own size, and is made from systems at the next scale down.

Look at the task of making a meter diameter tunnel of some length through rock. Consider the difference between a drill and a hole saw. You don’t need to rip apart the entire bulk of rock at a molecular level. You break it up into small chunks and then move those chunks. This might be done like a fungi growing, with the working face attacking the rock with “enzymes” or other nano-scale tools to rip the atoms apart. Power, raw materials, and cooling is transported using a circulation system — blood or sap in pipes moving at high speed, not the same speed as nano-transport within a nanobot.

Clearing the debris can be done the same way a mole rat does it, by building up mechanical systems at the proper scale to lift and push them. So you build up tissues and then muscles (or whatever — hydrolics, belts and gears).

Answer 3

• I think If you want to go with disassembly, choose your regular fluor-antimonic acid. (the nanites can control, where it flows)
• The real problem is transporting. I can only speak about how my story got around this: magnetic nanites, carried around by superconductors (based on this).

• For building, I think it would be good if you use this strategy: nanites get a small task assigned to them, they execute it and build a block of the structure you want, these blocks get placed together, into bigger ones and the bigger ones into more bigger ones, the process will repeat itself.

• Communication and data storage: go with natural stuff (DNA, hormones, nerves, etc..), choose the toughest creature as your base for nanites, our tardigrade overlords, the ones who won the evolution.

And keep in mind:

Nanite's strength lies in their ability to cut the great work into their smaller, personal tasks. You don't just grow sphere with a constant speed, you cut it into two, then reunite them, once they grew enough.

Quotemine This! -Redacted Redacted

And for the aforementioned reason, I can't really answer your question, as there are lots of ways, in wich building times can be gradually decreased, but I'm gonna give you a link, about an ancient nano-factory, that is capable of reproducing itself, has some lower efficiency solar panels and has overtaken the planet by now. Here it is.