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September 10, 2005
Dr. Richard Claus, Director, Fiber and Electro-Optics Research Center, Virginia Tech, and President, Nanosonic, 7/20/05
Dr. David Lemberg: Our next guest is Dr. Richard Claus, Director of the Fiber and Electro-Optics Research Center at Virginia Tech and President, Nanosonic, located in Blacksburg, VA. Dr. Claus is a recognized expert in advanced materials and structures. He is the author of more than 850 technical journal and conference publications and holds 30 issued patents, most concerning smart materials and structures in nanotechnology. Dr. Claus is co-Editor-in-Chief of Smart Materials and Structures, a journal of the Institute of Physics. He received the Optical Engineering Society’s Lifetime Achievement Award in 2002 and he was named Virginia’s Outstanding Scientist in 2001. Welcome, Dr. Richard Claus.
Dr. Richard Claus: Thank you very much.
Lemberg: Rick, thank you so much for being with us. Can you give us a brief background on the Fiber and Electro-Optics Research Center at Virginia Tech?
Claus: Sure. Our Fiber and Electro-Optics Research Center, or FEORC, was started in 1985, largely by the State of Virginia, the Commonwealth of Virginia, in an effort to try to entice university faculty to work with industrial people around the state and around the country. And, over the years, we’ve worked on, I think, now, it’s about 650 programs, totaling about $45,000,000. Things, obviously, in the fiberoptics area changed quite dramatically, as you know, a few years ago.
And, one of the technologies that we were involved in was making optical fibers with very specialized coatings. At Virginia Tech, we have a complete optical fiber manufacturing facility and out of that very specialized coating research work that was funded by the Army, we developed, back in the early 1990s, what now would be called a nanotechnology manufacturing capability, based on self-assembly.
Lemberg: Rick, we were just speaking about building a space elevator with carbon nanotube composites.
Claus: Yeah, I heard that. That’s interesting.
Lemberg: Really interesting.
Claus: Very interesting.
Lemberg: Can you tell us some of the primary technical challenges involved in developing nanotech for practical use?
Claus: Good question. Probably, the biggest challenge is one that’s been recognized by, for instance, the National Nanotechnology Initiative, the NNI, and that challenge is the transition of nano to macro. I heard your speaker a few minutes ago, say that his company doesn’t make the individual building blocks that are required to make something like a space elevator or the carbon nanotube components that go in. And, that’s one of the challenges. Right now, there is no nano-store. You can’t go and buy nano-things in large quantities. And, you also can’t find ways to put together nano-sized molecules or polymers or other materials to make large scale systems such as the space elevator components.
Sam Kephart: In terms of the whole concept of self-assembly, that assumes that you’re able to commercially produce sufficient quantities. And then, embedded in the material is, forgive the phrase, but some intelligence that lets it know what to do when it’s put to work.
Claus: That’s correct. That’s a good analogy. If I can repeat that back to you a different way, self-assembly’s real attractive because it means that we, as people, don’t have to do all the work in some way, and it would be very attractive if you could take a lot of molecules, put them in a beaker, shake them up and get part of an automobile. That’s not what we’re doing and I don’t think that’s what really anybody has in mind when they think about self-assembly. But, I think what they do mean, is that instead of working with materials, traditional materials as we normally do, taking large sheets of metal and cutting them and beating them and processing them to make some kind of a material or starting with a boule of silicon and cutting it, and then machine it and functionalizing it and transitioning materials into it and defining areas. That’s very complicated, as well.
The self-assembly process that we use is called a couple different names. What we usually call it is electrostatic self-assembly because the self-assembly occurs due to positive negative charge interactions. The way that it works, is we take a substrate. I’m sitting here in an office and I’m looking at my computer screen, so let’s take the piece of glass that’s on my computer screen, make that the substrate. We clean it and in cleaning it, we expose charges on the surface. If you want an analogy, we expose the top valance band electrons or the outer most atoms on the surface of the material. So, let’s say that the material that we start with is negative. It has a negative charge, locally, on the surface. We, then, make up usually water-based solutions but solvent-based solutions of materials, of molecules that are either anionic or cationic. They’re either negatively charged or positively charged molecules.
And, we take our substrate, and for want of a better analogy, we don’t get in the opposite charged solution. So, we would take my negatively charged computer screen and we’d immerse it in a bucket that contains positively charged molecules. And, everybody knows that the positively charged molecules are going to be attracted to the negative charges on the surface and they form a nice, perfect monolayer on the surface of the material.
We, then, take the material—now, the outside surface is positively charged. We go over to our negative molecule bucket and we stick our positively charged substrate into our negative bucket and the negative molecules stick on the surface. Now, the material’s negative. We stick it in the positive, then the negative and the positive, and we gradually grow a material and the thickness of the material is determined by the size of the molecules, which are small, they’re nano-sized—the size of the molecules and the number of dips that we use.
Also, of course, it depends if we’re at a university and we use graduate students, it depends on how tired the graduate students get. Over at Nanosonic, we have large robot systems that don’t tire out and they don’t eat as much as graduate students, and they run 24/7, so we can do this process for a long time to build up very interesting materials that are similar, in a way, if you like another analogy, to the way that your bones grow, one molecular layer at a time.
Kephart Well, the implication, again, going back to our previous guest, in theory, some of these intelligent materials could be positioned on this spaceport or space elevator and basically, it builds itself as it goes out. I’m oversimplifying, but if there’s robotics involved and sources of supply in a controlled environment, there’s no reason to assume that could not happen.
Claus: No, no, there would certainly be some engineering challenges to overcome, for example, what do you do with the water in space? That would be kind of difficult. How would you do dunking? How would you immerse a substrate? If you could work out some of those, you could do it. The type of approach that we’re looking at for terrestrial manufacturing, is, again, back to that nano to macro, that molecule to large scale structural component manufacturing where you, effectively, tell all the little molecules where to go and how to position themselves in the material. And, so far, the success we’ve had has been making materials up to about a half-inch thick and about two foot square, so something that’s about the size of a desk pad, or about a quarter of a four by eight sheet of half-inch plywood.
Lemberg: Rick, thanks. Can we talk more about Nanosonic? And, you have a product called Metal Rubber. Can you tell us about this? It sounds like a terrific product.
Claus: It’s a fun product. Let’s see, Nanosonic, we were formed back in 1998. We currently have 56 people. We’re located in Blacksburg, VA on Main Street, so it’s a hometown kind of company. Metal Rubber came about because I went to a technical conference with a couple colleagues, a couple young colleagues. And, an esteemed colleague from a university in the Northeast was giving a talk about self-assembly. And, he said that no one would ever make anything large using self-assembly. It was wonderful for making very thin coatings, what are called ultra-thin films, so maybe a hundred nanometer thick or submicron thick films. But, no one was ever going to use self-assembly processes to make anything significantly large.
And, the young Ph.D. student next to me leaned over and said, “We can do that.” So, obviously, motivation was there, especially knowing who our colleague was. So, she came back and put together a small group of people, and within about six weeks, we had our material called Metal Rubber. And, what it is, is we went back to our drawing board of self-assembly and we very carefully didn’t select—we didn’t buy, but we made our own nanoclusters and we made our own polymers. One of the great things about Blacksburg is it’s near Virginia Tech. And, Virginia Tech, as a research university, has a number of excellent programs, but one of them is in polymer science. And, we have some very good people working for Nanosonic who can design and synthesize pretty much anything we want in the polymer area.
By very good control over our molecules, we were able to put together metal nanoclusters and polymers very quickly, using that self-assembly process. And, we were able to make relatively thick millimeter- to centimeter-thickness materials. Again, I’m in an office and I’ve got a mouse pad in front of me. We were able to make pieces of material about the size of a mouse pad. And, the material has properties that are somewhat similar to metals and somewhat similar to polymers. Like metals, they conduct electricity, they’re electrical conductors. Top electrical conductivity is about 10-5 ohm-centimeters, which is about a factor of 10 less than the best noble metals like copper, silver, or gold.
So, the material’s an electrical conductor, but it’s also an elastomer, it’s also a rubbery-like material. It has a Young’s modulus—the lowest we can manage is around 1 megapascal, which is sort of like a very droopy rubber band. And, through design, we can make the modulus up to about that of a piece of plywood. So, Metal Rubber is pretty cool. The other really neat thing about it is that since you tell all the molecules where to go during the self-assembly process, you can control the percolation properties.
In other words, you can control sort of the exact percentage of, in this case, the electrically conducting species in the material so that from end to end, through the material. Now, remember, the material is, effectively, a polymer C, if you like, with little electrically conducting lily pads across it. So, electrical conductivity occurs by electron hopping or frog-hopping from lily pad to lily pad.
You can position the lily pads, so that the metal nanoclusters—just far apart enough, so that the frogs can just jump and get from end to end. And, by doing that, it means that you can make the weight percentage of the metal and the polymer very low. So, our Metal Rubber is electrically conducting. We can stretch it like a rubber band, and it weighs as much as the polymer, itself. So, its density is about a tenth of that, of conventional metals. Very exciting, very fun stuff.
Lemberg: Rick, this is great, thank you. We only have a minute left, and I apologize. Can you tell us just a bit about your nanotechnology school kits? This sounds terrific.
Claus: That came about—real briefly, that came about almost in the same way that Metal Rubber did. We saw some things that came out of the National Nanotechnology Initiative, and one of them was that it extolled the fact that nanotechnology was something that really could only be done at major research universities in the United States and elsewhere, around the world. We thought, you know, middle school is where—isn’t that where science and engineering and technology in students is really critical, in exposing middle schools? Why don’t we make a school kit for middle school students and have those middle school students two blocks down the road in Blacksburg, VA, be making nanotechnology stuff. So, we put some together, and we go on the road probably every two months or so and do another demo at another school, mostly in the region, of how to make your own nanomaterials.
Posted by David Lemberg at September 10, 2005 04:25 PM