Diamondoids are a girl's...

From a May 7 article in SpaceDaily:

Oil giant ChevronTexaco has announced it can now refine from crude oil sizable quantities of diamond-like molecules that hold great potential for science and health researchers. Chemists say the diamondoids, as they are called -- each less than a billionth of billionth of a carat in size -- could find their way into everything from advanced materials and microscopic devices to pharmaceuticals and jet fuel.

Carbon lattice -- diamond and buckytubes -- forms the strongest known material. Diamondoid molecular manufacturing is expected to be orders of magnitude better than rapid-prototyping systems, lithography, or biomimetic engineering. No other general-purpose manufacturing system can produce this material.

The SpaceDaily article continues:

For years, scientists for have salivated over the possibilities inherent in higher diamondoids -- those possessing four or more cages. The molecules come in a menagerie of shapes, from rods to disks to screws, and combine the useful properties of diamonds with the versatile chemistry of hydrocarbon molecules. This makes them ideal building blocks for nanotechnology -- or machines at the nanometer scale.

However, CRN Director of Research Chris Phoenix says:

The current diamondoids are not useful for complex nanomachines. They're only a few diamond crystal cells -- not enough to make complex shapes. They occur naturally in crude oil, so they are refined not produced, and they are mainly small molecules.

But the availability of these diamondoid molecules should allow researchers to improve their models of small diamondoid structures. This will be very useful when the time comes to design diamondoid machines. Also, the existence of these molecules further strengthens the case that there are many chemical pathways to synthesize diamond, and that small diamondoids can be stable.

Comments

[jim moore]

Chris,
I think these diamond molecules could end up being far more useful than you. I am not sure if that article mentioned it or not but these molecules can be chemically functionalized and turned into monomers. The monomers can be injected into a simple or a complex mold then polymerized. You can end up with a part made of stiff and tough plastic. This plastic will not be as stiff, as hard, as heat conductive as diamond but it could be tougher. And the molding process would likely at best be at least an 1 or 2 orders of magnitude less precise than mechano-chemistry. But i am thinking that a type of diamondiod plastic could be the basic building material for a proto-fabricator.

Your thoughts?

[jim moore]

To be a bit more precise, place four functional groups (maybe an acrylic acid group?) on the corners of the diamond cage. (I believe that the corners of the pure hydrocarbon should be the most reactive, they are the most exposed areas on the molecule. ) Then use nano-dip pen lithography to draw out a pattern using the tetra-functional molecular diamond monomer as the ink. Or you could pre-structure a substrate then jet out tiny drops and allow surface tension to organize the monomer. You then use an electron beam to provide the energy to initiate the polymerization. Boom you gone from a liquid monomer (critical question? what is the viscosity of the monomer? I don't know) to a stiff solid with a defined shape. The use of electron beams to cure plastic inks has been going on for years. Although, I haven't heard of any one using E-beams to cure nano-structured plastics.

[Chris Phoenix, CRN]

We already know how to make cubane. I'm not sure that a diamond cage would be more useful.

A diamondoid-based crosslinked polymer might have better material properties than other polymers. But without being atomically precise, and being made of somewhat "lumpy" parts, it would almost certainly suffer from high friction. This would make it hard to design mechanical devices.

We can already build things down to 20 nm by any of several lithographic technologies. I asked Ralph Merkle recently about whether one of these technologies could be a useful enabling technology for building a Merkle-style fabricator, and he said that friction would keep it from working.

I'm not saying this can't work, because it's not in my field and I want to avoid denigrating anything I don't know a lot about. But I'm not getting very excited about it.

Nanosys claims to have the ability to design and build a wide range of atomically-precise heterogeneous shapes out of semiconductor materials. Not just dots and rods, but bilayer ribbons and tetrapods. To me, this looks like a more significant enabling technology for eventually building nanoscale machines--though they don't seem to be working in that direction. http://www.nanosysinc.com/technology.html (Since they're about to go public, let me point out that I am *not* saying anything about them as an investment.)

Chris

[jim moore]

In reverse order
- Nanosys has some really neat tech, and hopefully if I can get on the right project at work I can work with some of their materials. (I do project development work for inks and coatings. One of the things possible with Nanosys's materials is printing electronics)

-Friction -Forget quantum uncertainty and thermal vibrations it sounds like friction is the biggest obstacle to MNT. Other than graphite on graphite (this includes bucky balls and bucky tubes) what interface has a low enough coefficient of friction?

-I have been working with energy curable inks and coatings for the last two years, so I kind of have monomers on the brain. Normally printers will use a UV light source to polymerize the liquid ink but some printers ( printing on some food packages) use an electron beam to initiate the polymerization. Now I know that electron beams can be focused on very small areas so I thought it might be possible to use mechanical placement followed by controlled polymerization to build the nanoparts, rather than using solely mechanical means.

-Cubane- bitch to make and not very stable- has strained bond angles between the carbons- The bond angles between the carbons in the diamondiods are not stressed

[Chris Phoenix, CRN]

Small-feature polymerization looks interesting. Can you make 3D shapes with elecron beams? You can with two-photon techniques--down to 20 nm. That isn't eutactic, but might help in a hybrid scheme. For large-scale production, mechanically guided chemistry is still the best I've seen.

Friction: Low friction has been observed between tungsten and (IIRC) graphite. And someone told me that it had been observed between H-implanted diamond surfaces. Theory predicts that it should be observed between a variety of surfaces, as long as they're quite clean. Anyway, what's wrong with graphite/graphite?

Chris