Responsible Nanotechnology

Common Sense Physics

For a few decades after molecular manufacturing was first described in detail, a variety of scientists looked for, and thought they found, a variety of reasons why it couldn't work.

In the end, it turned out that math trumps intuition - and the math supports molecular manufacturing.

For example, scientists who studied unattached atoms on surfaces knew that those atoms sometimes move around at room temperature. But the fact that an unattached atom will move says almost nothing about whether a firmly bonded atom will move - in fact, it's pretty easy to calculate that in most cases, it won't move. Atoms are slippery, but not that slippery.

Of course, even doing math can sometimes get you into trouble, if you don't check your assumptions. Some scientists dug up a theorem that appeared to prove that a flat graphene sheet could not exist, unless it was supported by something. (Graphene is just a single layer of graphite.) In other words, if you stretched a graphene sheet across a hole, something would break it or bend it or otherwise make it unstable. Since graphene has been proposed as a construction material for nanomachines, this might be a problem.

But in fact, the theorem doesn't say what the scientists thought. All it says is that the spacing between the carbon atoms in the graphite will not be quite regular over long distances. In effect, the sheet will be distorted sideways, randomly, a little bit, in patches. This is a pretty boring result, for most engineering purposes. As far as I know, it does not affect any proposed nanodevices.

For a more technical explanation, see Drexler's explanation of the issue.

Chris Phoenix

Are We Fascists?

We recently received an email referring to a page on CRN's website, and asking the question: "So you're going to monopolize this technology and keep as many people out of the loop as possible?  What are you, capitalists? fascists?"

(On reviewing our online content, I think maybe this page would be a better target for the question.)

CRN was founded on the belief that nanotechnology will lead to general-purpose manufacturing of high-performance products, some of which could destabilize whole societies (and others of which could solve many of the world's problems).

Before I answer the question, I would ask: Given that the US government does not allow us to own powerful weapons such as anti-aircraft missiles, how would you describe this policy? And how would you describe export controls on weapons (and even sufficiently powerful computers)? How about the International Atomic Energy Agency?

I don't mean to imply that CRN is the same as these policies, but they are attempts to solve similar problems. I don't think they can be described as simply as "capitalist" or "fascist," and I'd like to get a few more terms on the table before we decide which one fits CRN.

I've invited the person who sent that question to comment on this post. I hope we can get a fruitful discussion going.

Chris Phoenix

Seeing Smaller Than Light

Seeing nanostructures with light is like trying to read Braille by throwing beanbags at the dots and seeing how they bounce off.

A few years ago, it was assumed that light simply could not be used to see things smaller than half its wavelength - which means a large fraction of a micron, not much smaller than a bacterium. But in the past decade, technique after technique has been developed that lets light be used to see nanoscale objects.

A new technique has been announced recently - a very clever way of using "near-field" effects - very roughly equivalent to holding the beanbag instead of throwing it. 

If you look down into a water glass made of clear glass and filled with water, you may notice that you don't see through the walls of the glass - instead, you see a reflection back into the glass. But if you put your fingertip on the outside of the glass, you can see your fingerprint. This is called "total internal reflection" and it happens because the light bounces off the boundary between the glass and the air. But in bouncing, an aspect of the light (the "near field") extends slightly beyond the surface, and if your fingertip is right there, the light can interact with it.

Gold nanoparticles are highly effective at scattering light. If a gold nanoparticle were held very near the glass, it could reflect light back to a detector. If there were a very thin pattern of objects between the particle and the glass, then the light scattered by the particle would be affected by the objects. Now, keep in mind that the particle is very small. If it could be scanned back and forth, you could get a pretty precise impression of the objects laid on the glass - even without touching the objects. By controlling the height of the nanoparticle, you could get information about multiple layers of objects.

This is exactly how the microscope works. An atomic force microscope is used to scan the nanoparticle back and forth, up and down, over a slab of material (perhaps sliced from a cell) that's thinner than a wavelength of light. The light that's scattered off the nanoparticle is analyzed, and a 3D picture of the structures inside the slab of material that's being analyzed. The resolution can be as small as a few nanometers.

While I'm talking about microscopes, here's one that's cool because it's so low-tech. It uses an ordinary cell phone camera to record holograms of an image. I don't fully understand this one, so I won't try to explain it. But read the article, check out the cool holographic picture, and you'll get an idea of the kind of data that the system can generate. The cool thing is that somehow this is done without lenses, which means that it costs $10 (not counting the cell phone), suitable for back-country medical diagnostics. (Hat tip to Sander Olson.)

Chris Phoenix

DNA-Templated Buckytube Transistor

DNA Origami technology has been used to assemble buckytubes in a crossed structure that can act like a transistor.

This is important for several reasons. First, it may eventually provide a new way to build computer chips. There's a massive amount of money in semiconductors, and this achievement all but guarantees that DNA origami and nanotube circuitry will get funding.

Second, it provides a bridge between "hard" style nanotech - molecules that aren't very flexible, such as buckytubes - and "soft" style nanotech - relatively squishy molecules, like DNA, that can self-assemble. 

Since DNA origami shapes can be attached to a surface in fairly precise locations and orientations (templated by electron beam marks), this means that buckytubes can now be attached as well - or anything else that DNA can be self-assembled to (as with buckytubes) or covalently bound to. So, in theory, large arrays of bucky transistors could be self-assembled. Eventually, even irregular (but pre-planned) patterns could be created.

Hat tip to Eric Drexler for the story. And here's the abstract of the Nature paper.

Chris Phoenix

Musings On Freedom

A few words on freedom from the Lab Lemming, on the fall of the Berlin Wall 20 years ago.

He has some good points: many of us take freedom for granted today, but it's not so long ago that people were routinely shot or imprisoned for trying to leave the Soviet Union. And even in the West, today, our freedom is far from perfect.

Freedom is not an absolute or universal good. I've heard a Chinese woman say, "Choice is pain." How much freedom do you want? The same police who give me tickets for parking my car on the grass in my own front yard, also prevent my neighbors from blasting loud music late at night. And there are other tradeoffs. Do I want to live in a society where kids are protected? Of course... to some extent... but recently in Holland a teenage girl was taken away from her family because they were letting her go on long sailing voyages alone.

Freedom is, to a large extent, a product of society. As the basis of our economy changes, our various freedoms are likely to change as well.

How much freedom will be appropriate to an economy where a few percent of workers are enough to do the manufacturing (just as a few percent are enough to do the agriculture) and the rest have to find other kinds of work? On the face of it, manufacturing jobs don't seem especially free, so we might expect our freedom to increase. But the transition will probably come with economic pain, which decreases freedom.

And if we get more freedom than we are comfortable with, we are likely to give it away... perhaps even give too much of it away... or perhaps give away freedoms that we really need, while fighting to keep less important freedoms. This process may be encouraged by people who are good at making us worry about the wrong things (which includes a wide range of media - fear sells).

In the end, if molecular manufacturing leads to an economic revolution, what effects will that have on freedom? If the products of molecular manufacturing revolutionize military and police forces, what effects will that have? Will we recognize the new choice points - not just governmental, but also corporate and social?

Chris Phoenix

CAD Robots For the Masses

Not so many years ago, computer-aided design was an arcane skill, requiring programs costing thousands of dollars. Today, CAD is used widely, and the programs have gotten cheaper and easier to use.

How cheap? How about free. And how easy? How about a CAD program designed for children?

Hat tip to Tom Craver for pointing me at this website. It is a free CAD program that will let anyone design an object, see it in 3D, and calculate what needs to be purchased to build the object. Once purchased, the components are easily assembled. A wide range of robots can be built, and the robot-programming system was also designed for kids. 

When you click the link, you may at first think, "This is a toy, not a real system!" But why shouldn't it be both? 

It's not hard to imagine incremental evolution of this "toy" to enable stronger and more capable robots, or some other manufacturer producing a system that was designed from the ground up for building robots. There's already a robotics contest based on the current system.

So our kids are going to grow up familiar with the idea that they can design stuff on the computer in 3D and then build it quickly. By the time they graduate college, they might possibly be using molecular manufacturing to do the building.

Chris Phoenix

Molecular Manufacturing and the Origin of Life

Molecular manufacturing designs have traditionally looked a lot more like machines than like life's biochemistry, and molecular manufacturing has even been criticized for not taking more inspiration from life's techniques. But there is a fundamental connection between them.

The digital nature of chemistry (to be specific, molecule-forming chemistry) is what will allow molecular manufacturing systems to build duplicate systems, driving down the cost of manufacturing and enabling high throughput and large products. It's easy to think of life as squishy and analog, or complex and chaotic, but at its core, life is digital too. And it may even be the case that this is what allowed life to form in the first place.

I was recently discussing the origin of life with some biologists and other scientists. During the course of the discussion, I suggested that life might have developed from a soup of simple organic molecules when a fairly simple self-replicating molecule was templated by clay particles. (This conjecture is not original to me, but I think it sounds at least somewhat plausible.)

Someone objected that, during the time needed for the next advance to develop, any tiny perturbation would destroy the pre-life structure. Someone else pointed me at the work of L. L. Whyte[PDF]. Now, Whyte was writing before much was known about molecular biology, and his theories are about as accurate as the early descriptions of electricity as a fluid. But his observations and logic are first-rate, and one of his observations is that there must be some core that implements heredity and provides an organizing principle to organisms, and that core must be replicated with unusually high fidelity.

As a computer scientist who's studied molecular manufacturing for two decades, I had gotten used to thinking of self-replication as digital and highly accurate, in the physical domain as well as the computer domain. Reading Whyte got me thinking, and I realized that indeed, life does depend on near-perfect duplication of information - and it's not guaranteed that any particular process of copying will provide that.

Of course, this is what DNA does. Using the highly nonlinear forces of chemistry, DNA can be copied with an extremely low error rate - orders of magnitude lower than most organic chemistry processes. If this were not the case, then life would devolve - errors would accumulate faster than they could be selected out. But with the ability to produce essentially perfect copies of DNA, the total number of accurate copies can increase with each generation. Then, the small percentage of random mutations that are beneficial will lead to an increase in the total number of improved copies in each generation - at which point the improved copies will out-compete the degenerated copies, and the species will improve.

In discussing the conjecture that life originated with simple molecular self-replicators, many people will not make explicit their assumptions about whether the copying process is digital and accurate, or analog and lossy. It seems clear to me, now, that 1) the copying process must have been digital, because lossy processes could not have produced a lineage of ever-improving self-replicators leading to life; 2) Since the formation of molecules is, in general, a digital process, the theory survives this restriction.

I could say that this means molecular manufacturing is biomimetic after all. But I suspect that the use of digital copying processes in molecular manufacturing owes its inspiration at least as much to computer science as to biology. The bottom line is that digital copying works, and if molecule-forming chemistry were not digital, there's a good chance we wouldn't be here to talk about it.

Chris Phoenix