Nanotech: Engines of Hyperbole? ******************************* By Charles Platt Ralph Merkle and Eric Drexler are designing a robot arm. The arm contains about four million atoms, which sounds like a lot until you realize it takes up about as much room as a dust mote. In fact, if you laid out these robot arms like cookies on a baking tray, you could fit more than 62 billion per square inch. The concept driving this research is that instead of smelting steel, making molds, stamping out components, and fitting everything together on an assembly line, we can have robots tiny enough to assemble molecules one by one. This way, a gadget should be able to grow itself from a chunk of raw material, much as human beings grow by absorbing nutrients, turning them into useful compounds, and fitting them together according to instructions stored in our DNA. Stacking atoms individually is obviously going to be a time-consuming business. But suppose you tell your microminiaturized robot arm to build a copy of itself. Then you get the two arms to make two more, and you get those four to build another four. . .until, in a short space of time, this exponential growth gives you billions upon billions of arms ready to do whatever you want. Now suppose each arm has an equally tiny onboard computer controlling it, so that it can be quickly reprogrammed in a way that DNA never could be. Result: You have an entire factory of microbe-sized machines capable of building just about anything you want, including drugs, televisions, homes, highways, or microscopic repair robots that could run around in the human blood stream, rejuvenating tissues and zapping cancer cells. Our tiny helpers can be told to create whole new cities (and disassemble the old ones), eat up pollution, and remake the world as a neat, clean, postindustrial paradise. Along the way, they can bring us immortality by arresting the aging process. This is the promise of nanotechnology, the prefix "nano" meaning on the scale of a nanometer, which is a billionth of a meter (a typical virus might be about 100 nanometers long). It's a vision that some people have trouble taking seriously because it sounds so wildly transcendent. Can it really happen? Right now, the smallest control devices in the real world are still 1,000 times too big to manipulate single atoms in three dimensions. Ralph Merkle, however, is not discouraged. He's a calm, dignified, affable man with a friendly smile, the type who likes to resolve conflicts by asking everyone to sit down and be reasonable. But behind his easygoing manner there's no hint of compromise, and his impatience is obvious. If we make the right decisions, according to Merkle, we could see real results in maybe twenty years' time. Nanotechnology, he says, can be "the cornerstone of future technology, a fundamental factor in the future development of civilization." This sounds like empire-building on a grand scale; but like most nanotech advocates, Merkle seems at least as interested in living in it as in building it. (That bit about arresting the aging process does have its attractions.) Merkle heads the Computational Nanotechnology Project at Xerox PARC in Palo Alto, California, where he runs Polygraf chemistry-simulation software on a Silicon Graphics workstation. That's how he and Drexler are designing the robot arm - on the screen, where molecules can be edited with the same fluency with which most people edit text. The simulations verify that the atomic configurations are stable, and skeptical chemists are forced to admit that if the particles could just be pushed into place, the molecular bearings and reduction gears would work as advertised. But how long will it really be until this is possible? Seven years have passed since Eric Drexler developed the concept of nanotech in his groundbreaking book, The Engines of Creation. Is anything actually being done on benches in real-life laboratories to turn his utopian vision into reality? To answer this question, I did a quick survey of recently published literature and labs across the country. The National Nanofabrication Facility (NNF) at Cornell University in Ithaca, New York, seemed the most logical place to start. It's the largest facility of its kind, with a US$4 million annual budget, 250 graduate students, and a huge array of equipment that outsiders can use on a guest basis. Edward Wolf was president of the facility for its first ten years and now serves as its spokesman. He's an electrical engineer who used to work at Hughes Aircraft, and he has a can-do, no-nonsense, problem-solving style - the sort of man you can imagine saying, "If it ain't broke, son, don't fix it." Wolf is a believer in the top-down approach. In other words, we start by building small things, then we build very small things, and we keep on working downward in size, until we eventually end up at the atomic level. The NNF is currently exploring projects ranging from ultra-fast gallium-arsenide logic gates to chips that incorporate miniaturized sensors carved out of silicon. There are immediate applications for this kind of device. The mechanism for locking seat belts in a car, for instance, will soon be based around a chip that contains its own ultra-tiny motion sensor, like a miniaturized pea rattling in a pod. This is real, and it's practical, but it doesn't have the power and promise of nanotechnology, a word that now has at least two different meanings. To clarify matters, Drexler now talks about "molecular nanotechnology" to describe the process of moving molecules individually to create more complex structures (the bottom up-approach). From listening to Wolf, it quickly becomes clear that top-down advocates such as he have formed a faction that's violently opposed to the bottom-up approach. Wolf tries to be nice about it, but his impatience is evident. "The fact is," he says, "we have no idea how to do 3-D assembly. I don't want to demean anybody, but nanotechnology has been oversold, in the sense that it's been popularized." What's so bad about popularization? "Let me put it this way. As scientists, we all have great imaginations. But most of us are a little more cautious about speaking out." Meanwhile, on the other side are scientists like David Blair, a biologist at the University of Utah. "I have a lot of respect for Eric Drexler," he says. "He's a visionary." Blair is studying one of the smallest, most complicated, most fascinating objects in the natural world. It's an incredibly tiny motor, one-fourth the size of the robot arm that Merkle and Drexler would like to build. It also happens to be up and running. It's made of protein, and the amazing thing is, it grows naturally as a component of common, ordinary bacteria. Like any cells, bacteria must eat to survive. Somehow (no one knows how) they detect nearby nutrients and swim toward them. Their means of propulsion is the flagellum, which consists of a corkscrew-shaped filament attached to the nanomotor. It spins the filament at about 15,000 rpm, propelling bacteria in the same way that outboard motors propel boats. Make no mistake, this genuinely is a motor. There's a stator and a rotor, just as in a motor that turns an electric fan. Blair would like to take the motor to pieces, but he has no tools tiny enough for the job. So, he uses an indirect method, selectively damaging the proteins that the motor grows from and watching how it malfunctions. "We're like auto mechanics who only have hammers to do our work," he says. "But I think we may learn interesting lessons for the design of man-made motors some time in the future." A more precise tool for investigating the nanorealm is the scanning-tunneling electron microscope (STM), which uses a super-sharp, servo-controlled tungsten tip to measure the size of individual atoms on a hard, flat surface. The STM is unsuitable for tracing the contours of soft bioforms, but its powers have been amply demonstrated in other areas. In 1990, Don Eigler attracted global publicity when he used his STM to push individual xenon atoms around so that they spelled out the initials of his employer, IBM. Eigler is now reportedly pushing carbon and oxygenatoms together to create carbon monoxide, but to advocates like Ralph Merkle, this kind of work is just the first step down a long road. Using today's STMs to manipulate molecules, says Merkle, "is like trying to build a wristwatch with a sharpened stick." However, an exciting new development in the STM world has come from an unlikely source. A graduate student named Mark Voelker, at the Optical Sciences Center of the University of Arizona at Tucson, has built the nation's first dual-tip scanning-tunneling electron microscope. Voelker is shy and soft-spoken, and he describes himself as "just another science nerd." But he seems to have a practical, do-it-yourself side to his personality. He enjoys hanging out in pool rooms, and he drives a rebuilt 1970 Corvette. "I blueprinted the car," he says, in his placid, low-key style. "That means I completely disassembled the engine, measured every part, and machined them to adjust the tolerances. Then I put everything back together again." He used the same kind of patient skill in building his microscope. Coming from a background in infrared astronomy, he had no special qualifications for the job; he just figured he ought to be able to do it. "I got funding to build a single-tip machine, originally," he says, "but part way through, I realized that with a little more effort and a little more risk, we could have two tips. So, while my advisor was away for the summer, I decided just to go ahead and do it." The advantage of using two probes is that one can apply an electrical signal while the other listens for it. This way, the microscope can not only sense its target, but interact with it. "People have a lot of designs for molecular electronic devices," Voelker says. "They've made wires consisting of conductive polymers just one molecule thick. But these things haven't been properly tested, because there's no easy way to make contact with devices that are 1,000 times smaller than current chips." Why is molecular electronics important? "Because it should enable us to put a million transistors in the same area occupied by one transistor on a chip today, and the smaller transistors should run a thousand times faster. That gives you a computing technology a billion times more powerful, in terms of computing power per square centimeter." Voelker sees other possible uses for his invention, and figures that for around US$100,000, he could put together an entire nanotechnology workbench. To build 3-D structures, he thinks it might work to create layers one molecule thick, then stack them. And he believes something of this sort could be achieved before the year 2000. But even molecular electronics is just a way-station along the path to true molecular nanotechnology. Drexler's ultimate model for a nanocomputer wouldn't use electricity at all. Instead, it would contain "rod logic"- a crisscross pattern of sliding rods, one molecule thick, each fitted with stops that interact with the others. If this sounds clunky, it's because we're used to thinking in macro terms. On the molecular scale, everything is so small and light, there's virtually no inertia, and nanomechanical systems can vibrate millions of times per second. Friction as we know it does not exist, and so far as anyone can tell, a rod-logic computer should never wear out. According to Drexler, a computer slightly larger than a virus, using this system, should possess the computing power of a present-day personal computer. This opens up some truly incredible possibilities. Imagine a "factory" the size of a stapler. It sits on your desk and "builds" a sheet of paper whenever you need one. But the paper isn't really paper; it's a matrix of tiny display and arithmetic modules, so it functions like a video screen and a computer combined, with voice recognition built in. Imagine every object in the everyday world imbued with this kind of intelligence. Clothes restyle themselves, houses remodel themselves, food grows itself and cooks itself, and surgical implants could adapt themselves to the human body. Nanotech advocates find this vision compelling, to put it mildly. They want to develop it, but more than that, they want to live in it - which is why they're so impatient to get funds for research that will create the tiny building blocks to make it all happen. It's hard to see how an STM could tackle this job. For the time being, at least, it may make more sense to fabricate nanodevices in the same way that chemists fabricate exotic compounds: by using the capability of molecules to self-assemble. In other words, on a molecular scale, we can throw pieces of a jigsaw puzzle into a bag, shake them around, and they'll put themselves together - so long as the shapes are chosen cunningly enough. There's already been some progress in this direction. Nadrian Seeman, at New York University, has "trained" DNA to form itself into the framework of a cube. Galen Stuckey, at the University of California in Santa Barbara, has created caged structures where one molecule literally wraps itself around another. This is getting back to the top-down approach to nanotechnology. Does it make sense to put resources into this, or should we find better ways of repositioning individual atoms? Eric Drexler claims to be agnostic on this subject. "I'd like to see vigorous research in both approaches," he says, "adapting atomic-force microscopes to position molecules and do mechanosynthesis, and applying existing chemistry to make polymers that will fold up like proteins, to form molecular machines." He's more definite about the areas in which he expects to see nanotechnology make its first impact. "The first high-payoff applications are likely to be in information. First, molecular sensors that provide special information about compounds, perhaps in home medical-test kits. Second, molecular devices that do what silicon does now, but better, perhaps providing terabyte RAM chips." (A terabyte is a million megabytes.) Meanwhile, Drexler is philosophical about the prejudice that many scientists still harbor. "The tide seems to be turning," he says, although he admits that many researchers take a short-term view. "They are interested in what they and their team can test in the labs this year, with available grant money, and they tend to be less interested in what could be developed by many teams working together over the next decade or two. In addition, the consequences of molecular nanotechnology simply strike many people as being too big to be true. I find this hard to understand. It's like saying that the ability to process the ones and zeros of information can't have much importance, because bits are so small." As always, Drexler feels he is able to refute his critics. His recent book Nanosystems is heavy with formulas, tables, and graphs, relentlessly proving the feasibility of molecular nanotech, and addressing every conceivable problem. Will thermal noise (vibration on the atomic level) impair the accuracy of nanomachines? How can reactive atoms be manipulated safely? After we build nanoscale robots, how will we communicate with them, to tell them what to do? He tackles all these questions using the tools of orthodox chemistry and biology. Of course, this is pointless if some scientists are so prejudiced against him that they won't take the time to listen. Edward Wolf, at the National Nanofabrication Facility, says that he can't comment on Drexler's arguments because "I haven't considered his work important enough to read." Biologist Thomas Donaldson has pointed out: "The future isn't a place that we travel to. The future is something that we have to build." As long as large laboratories focus on short-term solutions, the future of nanotechnology rests on the active work of scattered researchers like Blair and Voelker, and it will take a while before the simulations move off the screen, into the home. * * * Charles Platt (charles@phantom.mindvox.com) is a science writer and author of The Silicon Man. =-=-=-=-=-=-=-=-=-=-=-=WIRED Online Copyright Notice=-=-=-=-=-=-=-=-=-=-=-= Copyright 1993,4 Wired Ventures, Ltd. All rights reserved. This article may be redistributed provided that the article and this notice remain intact. This article may not under any circumstances be resold or redistributed for compensation of any kind without prior written permission from Wired Ventures, Ltd. If you have any questions about these terms, or would like information about licensing materials from WIRED Online, please contact us via telephone (+1 (415) 904 0660) or email (info@wired.com). 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