Wires of Wonder

It was the kind of discovery that only happens in chemistry once every few decades-if you’re very lucky. In 1985, Richard E. Smalley and several collaborators at Rice University made a form of carbon never seen before. The arrangement of carbon atoms in each molecule resembled a tiny geodesic dome, so the researchers called the material “buckminsterfullerene” after the architect who had popularized the shape. With its neatly structured network of atoms, the “buckyball” quickly became the poster molecule for nanotechnology. Then in the early 1990s, researchers made another startling discovery: you could also make hollow tubes out of the same carbon structure. Carbon nanotubes had many times the strength of steel, the electrical conductivity of copper, and were the diameter of a DNA molecule. They were, in short, perfect materials for building and wiring the nano world.

More than a decade after his initial discovery, Smalley’s enthusiasm for the new materials shows no sign of waning. Last year he co-founded a company, Carbon Nanotechnologies, to make the commercial quantities of nanotubes that will enable other labs to push the technology forward, and to develop applications. But his continuing excitement for fullerenes (as the general category of these carbon-based molecules is known) goes far beyond anticipation of future technological uses. Trained as a spectroscopist, Smalley, a chemistry professor at Rice since 1976, is fascinated by the molecules themselves. In accepting the 1996 Nobel Prize in chemistry for fullerenes research, Smalley called the discovery “one of the most spiritual experiences that any of us in the original team of [researchers] have ever experienced.”

The $33 million Center for Nanoscale Science and Technology, which Smalley established in 1995 and now directs, sits at the edge of the Rice campus in Houston as a testimonial to the potential of fullerenes. The number of research groups at the nanotech center is growing so fast that Smalley’s own lab has moved next door to the third floor of Rice’s Space Science Center. Technology Review deputy editor David Rotman recently visited Smalley to ask about the future of nanotech and hear why the Nobel Prize winner thinks nanotubes are so special.

TR: How has the increased attention and funding, such as President Clinton’s $495 million nanotech initiative for 2001, affected the field of nanotechnology?

SMALLEY: To have the president talk about it has emboldened scientists and technologists to start to put “nano” in their proposals. They know what the new buzzword is. But more impressive to me has been how this idea has caught hold with those out there doing science. And I don’t get the feeling that it’s artificial posturing. The core disciplines of chemistry and physics have warmed to this idea. Part of that has been a response to the funding. But I think there really is a general appreciation that there really is something here. The chemistry and physics have now advanced to the point that you can think of, and in some cases actually build and do experiments on, [nano] structures of sufficient complexity that something new happens.

TR: Is there a danger that, like many other buzzwords, “nanotechnology” will begin to lose its real meaning?

SMALLEY: I like the word “nanotechnology.” I like it because the prefix “nano” guarantees it will be fundamental science for decades; the “technology” says it is engineering, something you’re involved in not just because you’re interested in how nature works but because it will produce something that has a broad impact. When you put those two things together in one word, there’s a tension. As our disciplines, particularly chemistry and physics, have matured, we’re now dealing with things at a very fundamental level that do have a practical importance.

TR: When you look at the different work going on in nanotechnology, what gets you most excited?

SMALLEY: I have to admit I’m just obsessed about carbon nanotubes. It’s hard for me to go more than 10 minutes without talking about them. I think they are the coolest thing out there, and I think they’ll have the greatest likely impact. But if I break myself away from that for a moment, I believe research at what I call the wet/dry interface is intellectually most intriguing to me. It may be that in 20 years from now that is where we’ll look back and say we have made huge advances. What I call the wet side of nanotechnology is the machinery of cellular life. As we learn to interface this natural machinery with inorganic, electromechanical structures and systems engineered on the nanometer scale (the dry side of nanotechnology), vast new frontiers will be opened both in fundamental science and in practical technology.

Having said that, I can come back and say that nanotubes will be tremendously important to the wet/dry interface because they bring something new to the game. Organic molecules [carbon-containing molecules that are the basis of living things] are magnificently versatile, but there are some things they can’t do well. In fact there are some things that biological systems have not yet been able to figure out, even after four-plus billion years. One thing is conducting electricity the way that metals do. Others are thermal conduction, and strength and toughness. Bones are very impressive, and so are teeth. But they aren’t steel-let alone what nanotubes can do with strength and conductivity. So, being able to take a carbon nanotube and get it into the molecular biology realm-whether it’s actually dissolved and is one of the players, or as a probe, or as part of an implant, as part of a new membrane-it’s really bringing something brand new to the table in biology. Almost an alien thing.

TR: An alien thing because…

SMALLEY: Because it conducts electricity. It brings those properties you cannot get from other organic molecules. And it’s still carbon, so it has organic chemistry. Here is an object that has, to a superlative degree, the aspects that we hold most central to the inorganic world: hardness, toughness, terrific strength, thermal and electrical conductivity. Things you just can’t do with bone and wood. But it’s made out of carbon. It’s something that plays the game at the same level of perfection as molecules and life.

There is electricity in biological systems, but it’s due to ions moving across membranes. Nerves work by electrical conduction; electric eels certainly have electricity. But that kind of electricity is different than the kind that runs in wires and houses, runs around computers, makes radios work. It’s not the kind of electricity that has to do with electrons moving in coherent fashion over long distances with little loss. That’s the property of metals, of inorganic compounds.

TR: And now nanotubes could bring this kind of electricity to biological systems?

SMALLEY: Yes. They bring to molecular biology, to the things that go bump in the night inside a cell, a new toy to play with-something that conducts electricity.

TR: What will the new toys be?

SMALLEY: Stay tuned for the next millennium and we’ll see. I could give some examples, but they’d seem rather pedestrian and ad hoc. Up until you add something like this to the mix, there is no way that the incredible machinery of living cells can construct something that can conduct electricity with the efficiency of metals. Here we have an [organic] molecule that can do that. I don’t believe anyone is bright enough to predict the vast implications of that. But Lord knows how many years it will be before nanotubes are part of living cells. Before that, we can use nanotubes as probes into cells, as probes to detect the structure of molecules, to sequence DNA. These are wonderful new wires to do that.

TR: What projects are you and your group working on now?

SMALLEY: The single biggest focus is making nanotubes. That’s what this company initially is about, turning on the spigot so that researchers around the world will have access to the most pristine-quality tubes that we can possibly make in large amounts at low cost. We want to make nanotubes available at small enough cost to let your imagination fly. These tubes come in three types: metals [excellent electrical conductors] and two types of semiconductors. I want to produce them with high enough efficiency that I can deliver a kilogram of a particular tube.

TR: So you’re looking to make nanotubes more widely available. Other groups are looking at the nanotubes strictly from the point of view of applications. What are some of the interesting applications they’re working on?

SMALLEY: In the nearest term, it looks like one application will be in [flat-panel] displays. A number of companies already have prototype displays using nanotubes. I won’t be surprised if you see displays using nanotubes on the market within a few years.

Another area that will be quick is as additives in engineering plastics [used in structural or high-tech applications like computer housing]. You can give rise to antistatic behavior at even very, very low levels of nanotubes, and shielding for EMI [electromagnetic interference: such shielding is used to protect laptops and other portable electronics] at very moderate levels. Unlike anything else you add to polymers to make them antistatic or for EMI shielding, this will probably increase the engineering plastics’ toughness and strength. Also, I expect within a few years that you’ll find commercially available nanotube tips on atomic-force microscope probes. Use in nanotech gadgetry in general I expect will really flourish in the next five years or so.

What we would like to see is that the business develops so that there are economic incentives to build a large [manufacturing] process and get the price way down. At this moment, the cost of nanotubes is about $500 a gram. Calculate the numbers. That’s nearly $230,000 a pound. In time this stuff will be made as a bulk commodity closer to $10 a pound or even below that. But you’ll have to build a plant, and the market has to be out there. The rate at which the business develops is heavily dependent on these early markets.

TR: The hope is that as you get more and better materials out there, the applications will open up?

SMALLEY: That’s right. And this next year will be a real watershed because our process will be putting out into the research community a minimum of 10 kilograms. The total production of single-wall nanotubes of any quality up to this time has probably been less than one kilogram.

TR: Of course, none of those shorter-term applications really fulfill the huge promise of nanotubes, do they? Such as acting as an electrical conductor in a biological environment?

SMALLEY: And what I was talking about before was only on the wet/dry interface. Then you get back to the dry side. There is a “lunatic fringe” of the nanotube world that we haven’t talked about yet. Over the next year there will be in my lab, and I suspect in many around the world, a big push to develop means of spinning continuous fibers-macroscopic fibers-of nanotubes with a high degree of orientation [the nanotubes would be aligned like uncooked spaghetti in a box]. I think that’s going to be successful, and it will be something special.

In one direction nanotubes are the strongest damn thing you’ll ever make in the universe and are excellent electrical conductors; in the other [perpendicular] direction, they’re floppy, and the electrical conductivity is quite poor. So, in materials where you want electrical conduction, you care about how well the nanotubes are aligned. I believe it is going to be possible to make continuous fibers of nanotubes in an efficient spinning process that will have the tubes all aligned. I wouldn’t call that the lunatic fringe; I think it’s going to happen. But now let’s talk about the really lunatic extreme. What if these spun fibers were, instead of a micrometer long, a kilometer long?

TR: In theory you could make nanotube fibers a kilometer long?

SMALLEY: In theory you can make them to Alpha Centauri. What would be the strength of a long fiber? You would have the strongest damn thing ever made in the universe. Can we ever make that? And what good would it be? If you could make it cheaply and a continuous length, you could make the longest suspension bridge you ever heard about, elevators in space. But “buckycables” would also be terrific conductors of electricity. It is the logical replacement for all power transmission cables in the world. That’s at the lunatic fringe, but I can say that because I’m an advocate of it.

TR: As you know, there has been a growing effort to use organic molecules as tiny switches in nanoelectronic devices (see “Molecular Computing,” TR May/June 2000). What role do you expect that nanotubes will play in molecular electronics?

SMALLEY: In the long term, it seems they must figure in-because they’re nano and they conduct electricity. Whether or not they’ll figure into nanoelectronic gadgetry in the next decade, I don’t think anyone is smart enough to know. In fact, no one is smart enough to know if there will be any nanoelectronic gadgetry in the next decade. But most people agree that if you had to pick the electrical conductor in nanoelectronics it will eventually be a nanotube. We’ll just have to stay tuned to see how quickly that happens.

TR: For now, even something as simple as putting a nanotube where you want it is still a challenge, isn’t it?

SMALLEY: We are really children, not even children, babies, in understanding how nanotubes work.

TR: Still, I was thinking how quickly the field of nanotech has moved. When I interviewed you a few years ago, we talked a lot about the hype surrounding nanotechnology. Now, with more and more serious scientists getting involved, it seems to have moved beyond that.

SMALLEY: That was the key factor, serious scientists getting involved that are far removed from “nanobots” [nanoscale robots figure in many speculative visions of nanotech]. We haven’t quite completed the task of “de-nanobotting” the field. But the main point is that nanotechnology is so important that we don’t want it to be associated with just nanobots. Whether or not they can ever happen is another issue, but there’s a so much broader reality to nanotechnology-and in ways a much more interesting one.