It's pretty much moving atoms in two-dimensions only (essentially pushing them on a surface with a tiny needle). And it's painstaking--you certainly couldn't make anything on the macroscopic scale. I doubt even nanobots are feasible (how would they work?).

Also, in the case of e.g. the 3D Sierpinksi triangle there'd be structural issues (the voids would be fill with something), and you'd be up against entropy (there would be defects, so I'm not sure if it wouldn't just collapse) so it's really not much more than a thought experiment at this time. And, ultimately, what would be the point? Unless you can get novel electronic or mechanical effects etc. I'm not sure it'd be worth it.

We basically have nanobot's. The problem is unlike science fiction working at the atomic scale things don't react the same way. For example you can build a motor, but ATP or something close it it's going to be the fuel as heat engines don't really work. Which is why we end up using Bactria/viruses/plants/animals and simply overwrite their DNA. Granted we can get a lot better but don't expect anything to be both small and intelligent even the simplest chip is huge we compared to a virus.

Insanely-high surface area materials exist, the best example I can think of is activated charcoal https://en.wikipedia.org/wiki/Activated_charcoal#Properties but batteries are using it too http://spectrum.ieee.org/nanoclast/semiconductors/nanotechno... "Solids" like you mention are aerogels https://en.wikipedia.org/wiki/Aerogel#Alumina and this new aerographite http://www.extremetech.com/extreme/133056-aerographite-six-t...

> Tiny self-replicating machines which produce other things to atomic precision

Don't expect it to happen soon - we can't even make big self-replicating machines yet.

We don't even know what machines would look like at such a small scale. Structures behave very differently than they do at human scale; fundamental components like ropes, gears and pulleys might not be possible.

And then there's the problem of programming these machines; you can't exactly put an AVR inside them.

I don't think there's any particular reason to believe that building a large self-replicating machine wouldn't be feasible with modern technology. It's just not useful or cheap, so nobody's done it. NASA studied the idea and I don't think they came up with anything too impossible about it:

http://en.wikipedia.org/wiki/Clanking_replicator

From-scratch nanoscale replicators are a whole other beast. However, I think we can say that we know what they would look like, as we have a ton of examples from the natural world. Building ones that do our bidding is a bit tougher, obviously.

A machine that could build faithful copies of itself using only materials from the natural environment (i.e. not this http://en.wikipedia.org/wiki/File:MolecubesInMotion.jpg) would be absolutely revolutionary and would essentially be a completely alien and artificial life (mutation not being especially difficult to include, and probably difficult to prevent). It would change the world, because once you have replication you can piggy back just about any other ability on top of it and do it on a massive scale, no matter how inefficient at the individual level.

I will gladly pay you $100 billion for a self-replicating machine.

The machine they used to do this weighs about two tons. I don't think there's any indication that being able to do this implies being able to build atomic-scale machines that can do the same thing.

Avogadro's number matters. At 100 atoms/sec, how long will it take to make something larger than a cubic millimeter?

That's where the nanobot idea would come in - divide and conquer <=> replicate and multiply? Somehow a single DNA strand turns into a 3 kg baby in 9 months... so maybe it's possible to make a tiny machine that makes some bigger tiny machines etc. etc.

That was awesome, thank you for this video. The demoscene is inspiring.

You might find this page interesting too - goes into some detail on how it works: http://inst.eecs.berkeley.edu/~cs184/sp12/assignments/Archiv...

I'm itching to go try writing one now...