Analog Computers & Nanotechnology

In this month's CRN science essay, Chris Phoenix writes:

Far back in the misty dawn of time, around 1950 or so, there were two kinds of computers. One was the now-familiar digital computer, doing computations on hard-edged decimal or binary numbers—the forerunner of today's PC's. The other kind of computer was the analog computer. At the time, analog computers were far more powerful than digital computers. So, why did digital computers come to replace analog, and what lessons does that hold for nanotechnology? The answer can be found in several properties of digital computers—precision, abstraction, and high-throughput production of components—that will also be found in molecular manufacturing systems.

Molecular manufacturing proposes to build useful products by building molecules using mechanical processes under computer control. A few molecular construction techniques, repeated many times, would be able to build a wide array of molecular shapes. These shapes could be used in functional nanosystems, such as sensors, computers, and motors. The nanosystems could be combined into useful products—even kilogram-scale or larger products containing vast numbers of nanosystems built and assembled under automated control.

This type of nanotechnology is sometimes criticized by nanotechnologists working in other areas. Critics say that the approach is unnatural, and therefore will be inefficient and of limited utility. The trouble with this argument is that digital computers are unnatural in similar ways. If this argument were correct, then digital computers should never have been able to supplant analog computers. . .

[MORE HERE]

Today's nanoscale technologies are comparable to analog computers: they deal directly and elegantly with physical phenomena. However, digital computers have replaced analog computers in almost every instance, and have expanded to perform many tasks that would be impossible with analog methods. In the same way that digital computers attain greater flexibility, lower cost, and easier design by abstracting away from physical phenomena, molecular manufacturing will be able to take advantage of the precision of atoms and their bonds to build nanoscale manufacturing systems capable of making a wide variety of products. It remains to be seen whether molecular manufacturing methods will supplant or only complement other nanoscale technologies, but the history of computers suggests that such an outcome is possible.

Tags: nanotechnology nanotech nano science technology ethics weblog blog

Comments

[monty]

So if current nanoscale technologies are not general purpose does that mean molecular manufacturing will be?

I thought molecular manufacturing was only proposed for diamondoid stuff. Are you now saying that it will also be able to make food and water for poor people in famine zones too? What about medicines and things made out of metal?

If molecular manufacturing can't make them we'll still need traditional factories for metal things and medicines + cows + sheep + pigs + chickens + potatoes + onions + tractors.

You can't raise a chicken on acetylene feedstock, though many have tried.

[Tom Craver]

In many cases, metal is used for structural strength - most such applications could be replaced with diamond beams and nanotube cables.

Most engines may be replaced with MM'd electric motors and fuel cells.

Longer term, MM probably will handle metals - once you get MM working for carbon, moving on to other elements is an obvious elaboration. It probably won't take long to develop, and will kick off a second revolution in mixed-element materials shortly after the diamond revolution.

Organic materials may be made by confining them in diamond containers shaped and sized to hold just one molecule, so the "soft" organic molecules aren't allowed to deform while under construction. That'd likely only be done when one needs to produce ultra pure complex substances - e.g. for drugs.

For more mundane organic molecule production - e.g. for food production - it'll probably be cheaper to build artificial catalysts - diamond shells precisely shaped and with precisely charged surfaces so that molecules in solution very quickly fall into place on the shell, where they can be brought together with another attached molecule to greatly increase the chance of the two reacting in a desired fashion.

[Mike Treder, CRN]

Monty, the term "general-purpose" as it is typically used does not mean "able to make anything."

We refer to molecular manufacturing as a general-purpose technology because it will have significant impact on almost all industries and all areas of society. Even in its early stages, it should offer better built, longer lasting, cleaner, safer, and smarter products for the home, for communications, for medicine, for transportation, for agriculture, and for industry in general.

Diamondoid materials will be immensely adaptable and will fill a great many purposes. But to make foodstuffs or medicines, for example, more ingredients will be needed. Almost all foods will require water -- and that's where things get more complicated. It will take several generations of improved nanofactories until that capability is achieved.

[Tom Mazanec]

Don't forget...technology generations have been getting shorter and shorter...

[Mike Treder, CRN]

Yes, you're right. We haven't stated any expectations about how quickly nanofactory generations may pass. Some people say months, but others say years; we think it's too early to tell.

[monty]

So you think that ten years or sooner after developing diamondoid nanofactories we'll also be able to make stuff like cotton & coffee & tea & sugar & grits & mushrooms. Crazy!

What about soap, hairspray, bleach and toilet paper? toilet paper is gonna be a hard one.

Also you say that diamondoid materials will be immensely adaptable and will fill a great many purposes but can they ever replace metals? do you think its gonna be possible to build the first self-replicating nanofactory with no metal parts?

isn't that like a fundamental flaw in your plan?

[Mike Treder, CRN]

Monty: Metals will be among the first materials replaced by diamondoid.

You may be familiar with the predictions that structural components made from diamondoid will be "100 times stronger than steel and lighter than plastic." That's not an exaggeration. Already, in fact, before we're able to make large quantities of diamondoid, researchers are developing cables made from carbon nanotubes that will be much stronger than any metal.

Depending on how it's configured, carbon can be an excellent conductor of electricity or an excellent insulator; it can be highly flexible or extremely rigid; it can be translucent or opaque; simply put, it has all the properties needed to make it a superior alternative to metals (or plastics, for that matter).

[monty]

Woah! Back up! you're talking about a lot of different materials at the same tim ehere!

diamond is brittle. metal deforms to adsorb impact energy much better. you want proof... try hitting a penny with a hammer, then try hitting a similar shaped diamond!! who would live in a diamond skyscraper that shattered when someone attacked it with a chisel.

Nanotubes are only strong in tension in one direction if you can make them defect free but each one is very very thin so you'd need to join lots together somehow. Then the join becomes your weak point. Your talking about imaginary materials extrapolated out of nano material properties! it doesn't work like that!!

maybe you're thinking of a family of composites made out of nanotubes and diamond... along the same lines as reinforced concrete and carbon reinforced plastics. Perhaps you'd be able to get a trade-off of some properties for others if this could be done but you cant just assume you can get all the good properties you want at the same time!!

[Chris Phoenix, CRN]

Monty, slow down a bit. There's a fair amount of depth behind our expectations. I'm not saying don't be skeptical--just don't assume that our ideas are trivially broken.

Yes, we are projecting that we'll be able to make a variety of carbonaceous structures with a variety of material properties. Note that even if the components share a molecular structure, they can have differing properties--as different as glass and fiberglass.

I don't see any problem in expecting that long thin (sub-micron) diamond rods (or buckytubes if that's more convenient) will be combinable into strong, tough (non-brittle) structures. I certainly don't see a problem in building a nanofactory using diamond instead of metal as structural components. A nanofactory doesn't have to be very strong--a few small parts have to be very stiff, but diamond is good at that.

I don't know where your ten-year figure came from for making organic molecules--I don't think it came from us. I will note that a machine-learning system which can make and test trillions of mechanical variations per hour, and/or use exaflop computers for chemistry simulation, may be able to develop mechanosynthesis-based organic synthesis systems rather quickly. But I won't put a year on that. I will also note that nanofactories should be able to build excellent and inexpensive greenhouses.

As you note, metal deforms to absorb impact. But plastic deformation is destructive. And the migration of defects in metal causes weakness. Defect-free structures can be both stronger and tougher, absorbing impact *without* permanent deformation. (On the macro scale, you can use redundant structures so that most of your structure is defect-free despite a small defect rate.)

Chris

[monty]

please can you point me to some details regarding the "fair amount of depth behind our expectations" for carbonaceous materials. something technical if possible?

The ten year thing was me interpreting Mike's comment about it taking several generations. you don't seem to separate between diamond and non-diamond mm very clearly on this site! even if you are totally innocent of misleading people (which I doubt) you can see why you get laughed at when you rarely criticise other people's exaggerations.

not sure if your greenhouse comment was meant to be funny but it made me laugh! please elaborate how the steep price of greenhouses leads to world hunger. people in temperate climates overproduce as it is!

[Chris Phoenix, CRN]

Monty - Obviously I can't give a simple pointer to depth. There are some sections in my "Primitive Nanofactory" paper that are relevant.

There is a whole lot of stuff to criticize, if only we had time, and conversely there's a fair amount of stuff that looks like we should criticize it but it's actually plausible.

Open-air agriculture leads to a high environmental footprint, including water consumption, and high dependence on weather and climate. Greenhouses would make growing food more local and more predictable.

Chris