The hard limits of hard nanotech

There might be more agreement here than meets the eye. Drexler often posts informatively and approvingly about progress in DNA nanotechnology and other bio-related tech at http://metamodern.com ; this is the less surprising when you remember his very first nanotech paper outlined protein engineering as the development path. Nanosystems is mainly about establishing the feasibility of a range of advanced capabilities which happen to not already be done by biology, and for which it's not obvious how it could. Biology and its environment being complicated and all, as Jones says.

Freitas in Nanomedicine addresses applying a Nanosystems technology base to our bio problems, or at least purports to -- I haven't been able to get into it because it's really long-winded and set in tiny type. Nanosystems was more inviting.

For example, if you try to make very small, spherical diamond crystals, a layer or two of carbon atoms at the surface will spontaneously rearrange themselves into a new form--not of diamond, but of graphite.

What do we count as "spherical"? Adamantane is a symmetrical 10 carbon atom piece of a diamond lattice, with surface bonds terminated with hydrogen atoms. It is stable enough to be melted at 270C and recrystallized from the melt. It does not rearrange itself into graphite.

More generally: AFMs and STMs routinely use atomically precise positioning in the presence of thermal noise (the vibrational analog of Brownian motion) at room temperature. Set aside Drexler's analyses of thermal and quantum motions in molecular scale device for a moment: At this point we've had multiple decades of experimental experience of atomically precise positioning at room temperature. The tips of these devices are molecular scale structures being positioned with atomic precision. Sufficient?

The watery nanoscale environment of cell biology seems so hostile to engineering that the fact that biology works at all is almost hard to believe. But biology does work--and very well at that

Doesn't this mean that we shouldn't put too much weight on our intuition when estimating the long-term potential of nanotech?

Like most critics of the molecular manufacturing concept, Jones is attacking a straw man. Yes, Drexler’s initial vision of how to design nano-scale machines was a bit naïve, but we’ve known that since the 1990s and no one is claiming otherwise. The fact that mechanical engineering at the nano scale is different than at the macro scale should surprise no one, but different does not mean impossible (or even more difficult, really). See, for example, the extensive work of Robert Freitas analyzing the actual challenges and opportunities of nano-scale medical engineering.

If, for example, such devices can function only at low temperatures and in a vacuum, their impact and economic importance would be virtually nil.

Yeah, they would be limited to unimportant, fringe activities like:

• Scanning cryogenicly preserved human brains prior to uploading
• Repair and maintenance of deep space probes
• Isotope separation of deuterium, tritium, and He3 for fusion power.
• Mining operations on asteroids, comets, and gas-giant moons.
• Fabrication of carbon-nanotube-based structures for use in space-elevator and tether propulsion applications.

Minor, unimportant stuff like that. ;)

Well, impact and economic importance would be "virtually nil" until the second half of this century, maybe.

I figure most nanotechnology will work at room temperature and pressure.

If a particular manufacturing step requires a vaccuum, you can always just pump all the undesirable atoms out with a pump. If a low temperature is required, you can always just use a minature freezer. However, there is going to be plenty you can do without doing either.

Also, if nanotech can only work at low temperatures and in a vacuum, it's not much of an existential risk.

Biological nano-scale engineering has an additional constraint: it must be evolvable. The amount of bandwidth transmitted into the genome from the world via selection is surprisingly small.

In terms of software architecture, brownian motion gives a sort of message-broadcasting architecture - very decoupled. The messages (proteins) know how to execute themselves (very object oriented). The entity building it from data (ribosome) doesn't know what it's building. The entity powering it (ATP synthase) doesn't know what it's powering.

In this design, in order to one location to communicate a message to another location, some mass has to brownian-motion its way across. Suppose in a redesign, locations that needed to communicate messages were wired together with flexible polymers. Moving electrons, waves of configuration changes, or even molecular messages along a guide would be significantly faster, particularly over long distances; latency is proportional to square of distance for brownian motion. (Indeed, in latency-critical applications, biology does use wire-ish communication; neurons.)

Even admitting that Drexler's nanomachines probably look more ridiculous to a future experienced nanoscale engineer than Da Vinci's machines do to a mechanical engineer, there's obvious room for improvements. We cannot assume that biology is anywhere close to the limits on efficiency imposed by the laws of physics.

I never thought that kind of nanotechnology would work outside a vacuum. This never seemed like much of a problem to me.

Consider. Using such technology, it's relatively trivial to create a vacuum, including macroscale devices with internal vacuums.

They'd need a significant amount of shielding to prevent atmosphere from leaking in, yes. Millimeters, possibly. Is that.. really a problem?

The watery nanoscale environment of cell biology seems so hostile to engineering that the fact that biology works at all is almost hard to believe. But biology does work--...aided by its own design principles, which have evolved over billions of years to exploit those characteristics.

This is pure dark arts. Emphasis added.

The article seems pretty reasonable overall but enough of it is technical enough that I'd be wary.

immanent --> imminent