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« CRN Hosts Kurzweil Interview | Main | What Does 'Responsible' Mean? »

February 07, 2006


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Nato Welch

I think it's important to note that exponential manufacturing seems possible without having to drop all the way to the molecular scale. The central criterion is the ability of a factory to build a copy of itself with cheap raw materials and components. If this can be accomplished to just submillimeter-scales, the explosive will still probably occur. Early, primitive version like http://reprap.org/ are probably only a couple of years out, so long as you can handle limitations on capabilities (plastic only, lots of non-replicable common compnents like screws, lubricants, etc).

If this is the case, I tend to think that progressions in the kinds of products recursive fabs can generate, along with the scale at which they can be manufactured, will be incremental advances after the first primitve fabs take people by surprise.

Ya think?

jim moore

String-Sort Fabrication: 3D Assembly, outside the printing box

A solid grey box is extruded from the Stringer and you rip into the box like an eight year old boy on Christmas. The "zero string" comes away in great clumps, revealing your latest variation of the Bathroom Slug, (now it matches the towels again). After putting the Slug to work and recycling the zero string, you head outside only to find that the String Faeries had been by. So, you pick up the spools of string they had left and head back in. You slip the spools into the fabricator then step back and think about the fabricator.

The Stringers constant rate and volume of extrusion greatly simplifies its design. There are three major parts:
A rack of spools of string.
A Zone for slicing and mixing the strings.
An Extrusion Plate

The two things that all strings have in common is their shape and size ( hexagonal fibers, 10 microns across). There are two types of fibers: zero strings and every thing else. The zero strings make up everything that isn't part of what you are making. All of the other strings can bind to one another, are made of a variety of materials and can have complex internal structures ( you remember when strings were made of single material, now there is Utility Fiber ). This fab has 10,000 spools and uses about 100 different types of strings.

The splice and mix zone is the real guts of the machine. It does the heavy computation/processing needed to order each stream of strings for each of the millions of extrusion ports.

The extrusion zone presses the strings together. The sections of the strings that make up the object are bound together, the sections made of zero string are not.

Tom Craver

Ha! Great minds and all that! That sounds a lot like something I proposed to Chris the other day in an email - except I was coming at it from a security perspective - by making unbreakable strings of nanoblocks have a certain volume (about 1mm^3) the fabber would be prevented from producing 'invisibly small dangers'. Chris pointed out a likely way to get around that, but I still think it is a useful approach, and probably accelerates fabrication considerably.

Also, it sounds like your approach is to lay the strings out linearly, which is a lot simpler than what I had in mind - ie. I was thinking of folding a 10meter x 10um x 10um string or chain up into a larger component (such as a ball bearing, plate, rod, etc) in a preliminary phase, and then having microbot arms do final assembly of products. Definitely my approach is more complex, and perhaps there are other ways to keep the fabber from producing very tiny objects.

Chris Phoenix, CRN

Nato, atom-scale has several advantages over micro-scale.

1) Maintenance of precision. Atom-built objects can be essentially perfect to N generations, by adding just a bit of energy to remove entropy.

2) Low friction. Perfect atom-built objects can take advantage of superlubricity and zero wear. Micro-scale objects have serious problems with wear due to scaling laws.

3) High performance. Performance increases with decreasing size, so nano has a few orders of magnitude over micro.

4) More applications. Especially medical applications.

5) More flexibility of construction. By rearranging atoms, you can make different materials as well as different shapes. Also, with improved functional density, it's easier to design products.

6) Chemistry in products. It'd be hard to build stuff like fuel cell membranes with micro-fabricators. Easier with molecular manufacturing.

There are probably other advantages as well.

RepRap is a great project. And it's worth noting that an inkjet printer can print its weight in ink in about a day. Micro-scale exponential manufacturing is neither impossible nor worthless. But nano-scale will be a whole lot better.


Chris Phoenix, CRN

Nato, on re-reading your post, I realized I didn't quite address your question. Will there be a continuum between micro and nano fabrication? I'll answer that if you'll answer this: Was there a continuum between ENIAC and a modern Web-enabled PC with a Google homepage?

In some ways, there was a continuum. But there were also a lot of breakthroughs and sudden leaps in capability. The average person never saw a $20,000 PC, and never used BITNET. ENIAC simply couldn't run a GUI (though the first video game dates back to the 50's IIRC).

In some ways, there may be a continuum between micro fabs and nano fabs. Micro fabs already make products like shoes; RepRap includes wires; eventually micro-fab products may even include fab-built electronics and actuators and sensors.

So in the sense that they both make products, there's a continuum, just as ENIAC and Pentium both crunch numbers. But for the reasons I listed above, molecular manufacturing will be able to do a whole lot of stuff that micro-fabs simply can't do.


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