The Next Small Thing: A look at Nanotechnology

Nanotechnology is about seizing control of individual atoms and bending them to our will. Assembling structures and working machines out of atomic scale building blocks as easily as if they were Legos. With silicon chips, engineers learned to create tiny transistors made up of silicon trenches and towers only one micron — a thousandth of a millimetre — across. Nanotechnologists want to go smaller than that by a factor of a thousand. A nanometre is one billionth of a metre, and even this tiny dimension spans ten or so atoms. What’s the point? Small, in this case, is useful. Or terrifying, depending on your point of view.

Nanotechnology is about seizing control of individual atoms and bending them to our will. Assembling structures and working machines out of atomic scale building blocks as easily as if they were Legos. With silicon chips, engineers learned to create tiny transistors made up of silicon trenches and towers only one micron — a thousandth of a millimetre — across. Nanotechnologists want to go smaller than that by a factor of a thousand. A nanometre is one billionth of a metre, and even this tiny dimension spans ten or so atoms. What’s the point? Small, in this case, is useful. Or terrifying, depending on your point of view.

Imagine a world in which;

people no longer work in factories, replaced instead by sealed processing centres which receive truckloads of iron ore and crude oil and spit out a steady stream of solar-powered appliances or something or other;

a world in which people need never die, because every damaged cell is repaired instantly by a swarm of tiny robots the size of blood corpuscles thronging the veins and arteries;

a world never short of nourishment, in which a “food machine” in every house receives any kind of organic material from grass clippings to potato peelings and transforms them into steak, tofu or rice on command.

That (and a lot more besides) is the vision of the Nanotechnologists.

Social Problems of Nanotechnology

The technological problems are awesome; the social problems even more so. While we cannot do any of this yet, there are enough clues about how it might be done to make the possibility one worth taking seriously; and on the whole, the history of technology teaches us that if it can be done, it will be done, and usually sooner than you think.

Such a nanotechnology revolution could be so profound as to make the steam-and-steel-driven Industrial Revolution look like a mere historical blip. Or so the nanotechnology enthusiasts would have us believe.

Their detractors hold up a more sombre vision: one of a world stripped of resources and de-populated by engineered nanotechnology machines that have “gone native” – escaped from the confines of their factory homes, evolved and multiplied, and eventually transformed the entire globe in accordance with their twisted programming. Of course, most detractors just don’t believe that nanotechnology can be made to happen at all, on any scale.

But all around the world, in the labs of universities and some of the world’s biggest corporations, scattered groups of scientists in many different disciplines – biochemists, physicists, computer scientists – are working on the “enabling technologies” that are the foundations of nanotechnology which has the capability to be the biggest enabling technology of all.

“Plenty of Room at the Bottom”

Like so many socially and technologically revolutionary ideas – Hollywood, The Sixties, the personal computer – nanotechnology was born in California. To be specific, on December 29th, 1959, at the annual dinner of the American Physical Society held at CalTech in Pasadena. The inspirational after-dinner speaker on that occasion, whose words reached out of the past twenty years later and planted a fertile seed in the minds of today’s first-generation nanotechnologists, was Richard Feynman Nobel prize-winning physicist, bongo player, and butterfly-minded genius.

Feynman’s talk was called “There’s Plenty of Room at the Bottom,” and it was a prescient vision of Nanotechnology – although the word was not yet coined. He began by imagining how the Encyclopaedia Britannica could be stored on the head of a pin. It’s not hard. All you have to do is to reduce the size of the printing by a factor of 25,000. Even the smallest dots in the half-tone process used to print photographs would still be at least 40 atoms across at this reduction.

Feynman’s vision is even more astonishing when you remember that he was speaking at a time when the transistor was barely more than a lab curiosity, the integrated circuit had not yet been dreamed of, and large-scale chip manufacture and micron-scale lithography were unimaginable. But Feynman went further. He proposed that if you were to code information using dots and dashes, represent those dots and dashes with two or five atoms, and then assemble the atoms into lines, the lines into layers, and the layers into a three-dimensional lattice, the information storage possibilities were enormous. In fact, you could assemble the information in all the books in the world, 24 million volumes or so, into a metal cube 1/10mm on a side. Smaller than a grain of sand.

Feynman’s talk is almost certainly the first reference to the manipulation of matter atom by atom. He even went on to discuss how it might be done. Drawing on an idea from a 1940s science fiction story by writer Robert Heinlein, “Waldo,” Feynman suggested that by developing a mechanism that scaled down movements by a factor of four, say, an operator moving his hands in sensor-equipped gloves might reproduce those movements on a smaller scale, and build a tiny lathe, for example. The lathe could then reproduce itself four times smaller, and so on until machines capable of manipulating individual atoms were the result.

The design of such “assemblers” is the key technological issue of nanotechnology, and Feynman had recognized it thirty years early.

At the end of his speech, Feynman threw out a couple of spur-of-the-moment $1000 challenges to the audience of physicists and engineers. As a recent house-buyer on a not-too-very-considerable salary, perhaps he should have thought better of it.

The first was to produce writing reduced by a factor of 25,000;

the second to build an electric motor that would fit into a cube less than 1/64th of an inch on a side.

The writing challenge was finally met in 1985, when a graduate student at Stanford University, Tom Newman, inscribed the first page of Dickens’ A Tale of Two Cities onto a silicon wafer using a beam of electrons only 5 nanometres in diameter. As it turned out, the motor problem proved more tractable. Only a few months after the talk, a CalTech physicist, William McLellan, had taken Feynman’s $1000. His motor had been built with the aid of a microscope, a watchmakers lathe, and an ample supply of toothpicks.

Top-down verses Bottom-up

For the same reasons that building Feynman’s tiny motor proved easier than writing on an atomic scale, today scientist’s approaches to engineering the ultimately small are divided into two camps: “top-down” and “bottom-up.”

In some ways the philosophical distinctions between the two techniques are as great as the yawning technological gulf that separates them. Top-down engineering is the art of making the big smaller. For millennia, mankind has manipulated chunks of material. With the industrial revolution and precision engineering came the ability to make small mechanisms, on the millimetre scale. With the electronics revolution and the development of the integrated circuit came the ability to create devices a tenth and then a hundredth of a millimetre across. Finally, Very-Large-Scale Integration (VLSI) of electronic circuits produced new chip-making techniques able to produce feature a thousandth of a millimetre, or a micron, across.

Top-down engineering, the building of micro-machines, takes the latest techniques off the chip production lines and applies them to making machines. Instead of being transformed into a million transistors, the silicon wafer is etched into tiny cogs, gears, levers and motors. Top-down engineering has produced steam engines with pistons 10 microns in diameter, electric motors 130 microns across that spin at 10,000 rpm and produce a billion times less torque than a car engine, and tiny acceleration sensors that can be fitted to cars for a fraction of the cost of the gyroscopes used in aircraft accelerometers. Top-down micro engineering is here now, and is useful now.

But it is not nanotechnology. Not according to the nanotechnologists, anyway.

Top-down microtechnology is a fundamentally different path that I don’t think leads to the same destination,” says K. Eric Drexler, nanotechnology’s founding father and the man who gave nanotechnology its name. “With the top-down approach you use large machines to make smaller and smaller features while still keeping enough control of those little structures to do what you want.

“Molecular nanotechnology moves in the opposite direction. It starts with small, precisely structured molecules – the sort that people have been making for a hundred years with organic chemistry. The challenge is to make things bigger, while still keeping that precise control.”

The philosophical differences between proponents of the top-down and bottom-up approaches are enormous. Bottom-up nanotechnology is the ultimate machine, the revolutionary technology that will change the world for ever. Top-down is just another way of moving chunks of material around – smaller chunks, but chunks all the same. To ordinary people, who are after all built on a 1-metre scale, the difference between microns and nanometres may not seem a lot. Very small is very small. But to nanotechnologists, the difference is everything: micromachines are specifically excluded from the Internet’s “sci.nanotech” discussion group.

But despite the philosophical and technological gulf between the two-camps, there is one technology that bridges the gap. It uses a big machine to affect tiny samples of material, putting it in the top-down camp. But it is capable of moving one atom at a time which is the goal of the bottom up nanotechnologists. That technology is the microscope. There are, in fact, two specific types of machine – the scanning tunneling microscope (STM) and atomic force microscope (AFM). In both, a very fine point, only a few atoms across, flies a few atom-diameters above the surface being investigated. Using a feedback loop, the point is moved up and down to track the contours of the surface below. But the tip can also be used to reposition atoms.

The IBM Nano-Logo

In 1990, physicist Don Eigler drew his company’s logo with a hundred or so carefully, and individually, positioned Xenon atoms. The letters IBM were only 5 nanometres tall. The STM and AFM are not the Holy Grail of nanotechnology, the “assembler”, despite the fact that the combination of electronics and micromachining has now produced the first STM-on-a-chip. Building nanotechnology an atom at a time using an STM would take “the age of the Universe” according to Eigler.

“It’s like trying to build a wristwatch with a sharpened stick,” says Ralph Merkle, a close associate of Drexler, who heads the Computational Nanotechnology Group at Xerox PARC. Drexler and his fellow nanotechnologists have a different model for the way they want their creations to behave. A tree.

The Tree as a Model of Nanotechnology

“To make wood and leaves, trees gather solar energy using molecular electronic devices, the photosynthetic reaction centres of chloroplasts,” explains Drexler in his 1992 manifesto, Unbounding the Future. “They use that energy to drive molecular machines – active devices with moving parts of precise molecular structure – which process carbon dioxide and water into oxygen and molecular building blocks. They use other molecular machinery to join these molecular building blocks to form roots, trunks, branches, twigs, solar collectors and more molecular machinery. They do all this without noise, heat, toxic fumes or human labour, and they consume pollutants as they go. Trees are high technology. Silicon chips and rockets aren’t.”

At the heart of Drexler’s nanotechnology is the “assembler”, a device capable of taking individual molecules or atoms, and putting them where they are wanted. Assemblers could be anything from the 4 million-atom robot arm that Merkle and Drexler are designing on a computer at Xerox PARC, to a type of protein that coils and folds in a specific way in response to chemical messengers in its environment. The assembler concept also draws on the infant science of quantum chemistry, which looks at exactly what happens when the jigsaw-like parts of different molecules fit together in a chemical reaction. Using quantum chemistry, one can predict what will happen when part of one molecule is physically pressed close to another. Will there be a “snap-fit” like Lego blocks, or will the parts twist out of the assembler’s grasp to join incorrectly. Quantum chemistry is very different from the solution-based reactions that have been the mainstay of chemistry since the seventeenth century.

“Producing engineered structures from reactions in solution is like putting all the parts of a watch in a box, shaking it hard, and expecting to open the box and pull out a working time-piece,” says Drexler.

Ribosome Assemblers

The assembler may sound like a pipe-dream, but in fact, untold billions of these devices already exist. One example is a ribosome, the molecular machine which builds all the proteins in every living thing on the Earth. Responding to instructions coded into the shape of the “messenger RNA” molecule, the ribosome grabs individual amino acids in sequence and welds each one to the growing protein structure.

Assemblers will have to be more complex and adaptable than ribosomes if they are to achieve the ultimate goals of the nanotechnologists. They will have to be able to make several different types of bonds rather than the one the ribosome can manage, for example. Even so, such an assembler need be only ten times larger than a ribosome. Today’s hand-waving designs for assemblers predict that they might be built weighing about 10exp9 atomic mass units – that’s 60 million million in every gram.

A New Computer

Where the ribosome has its messenger RNA, the assembler must clearly have some kind of controlling computer able to direct the work in progress. On the molecular scale, electronic circuitry becomes impossible to implement, so Drexler and his colleagues have come up with an entirely new kind of computer. In some ways, it is the descendant of the abacus, or one of Babbage’s nineteenth-century mechanical calculators. Except it is about a hundred-million times smaller. The control computer is made of up of mechanical “locks:” two rods that cross and can block each other’s movement. These locks can be used as simple logic gates. Ten thousand such gates would be enough to build a simple control computer with about the same power as the 6502 microprocessor at the heart of the early 80’s vintage BBC micro. Yet this rod computer would be a cube of material a mere 50 nanometres on a side. What could it be made of?

The natural world is an inspiration to bottom-up nanotechnologists, but they expect their creations to transcend it. Instead of cellulose and collagen, the structural building blocks of trees and people, “assemblers” will produce creations of pure diamond-like carbon. Diamond microstructures, the strongest arrangement of atoms known to man, should have thousands of times the strength of steel. Prototypes of such structures already exist in the labs where buckyballs and buckytubes are now being made routinely.

Assemblers, Replicators and Nano-Computers

Assemblers are not the be-all and end-all of nanotechnology. Drexler divides the capabilities of nanomachines into assemblers, replicators and nano-computers. Replicators are assemblers that build copies of themselves; nano-computers much larger versions of the rod-logic control processor offering the calculating power comparable to one of today’s supercomputers in a package the size of a grain of sugar.

“Not all molecular machines will include assemblers,” he says in a recent essay, “for the same reason that not all of today’s machines include a stereo. Equally, only a skilled and hard-working fool would build replicating abilities into every nano-machine.”

Even with these specialist machines, the capabilities ascribed by enthusiasts to nanotechnology are awesome. One critic quipped that some nanotechnology literature reads like a religious tract with the word “God” replaced by nanotechnology. In a recent survey carried out by the “sci.nanotech” newsgroup, nanotechnology was given a 90% chance of curing cancer and AIDS, a 95% chance of halting the aging process, an 80% chance of creating affordable personal Earth-Moon spaceships, a 95% likelihood of converting garbage into food.

But just to show that nanotechnology is not all-powerful, the group also assigned 5% probabilities to transforming lead into gold and making instant teleportation a technological reality.

Nanotechnology may inspire a quasi-religious fervour in some. Ralph Merkle was originally attracted to the field because it appeared to offer a way to repair brain damage caused by the cryogenic freezing intended to allow people to come back from the dead. But to others it is a commercial technology today.

Nanothinc, one of the US’ first commercial nanotechnology companies, released “Nanobox,” a desktop nanochemistry set which allows PC users to model fullerene (buckyball) molecules and then set about analysing real fullerene powder. But Nanothinc has much bigger ideas: to provide the world with all the information it needs on nanotechnology and the related enabling technologies, particularly via the Internet.

Nanothinc will have most of the relevant nano information that is in the public domain under one roof, and will create ways to make it easy to find what you want. They will develop on the Internet an electronic “Nanomall” for ‘everything you ever wanted to know about nanotechnology’. Not only will you find information but also products and services in the nano stores. The Nanomall will have entertainments attractions, magnets and various features such as a nanomoo (an electronic environment many users can share at once) visualization software, moderated science fiction forums, video and sound clips of nanopersonalities, and more. If you have World Wide Web Internet access, you can obtain a preview at URL: http://www.nanocentral.com

According to Nanothinc Chairman, Paul Green, “By fostering communication in a global on-line forum, we hope to integrate these independent efforts into a comprehensive whole.” Green believes that nanotechnology will revolutionize manufacturing, allowing anything that CAN be built to be built extremely cheaply. Replication is the key to this dream, as nanomachines combining assemblers with replicators swing into action producing both cars and copies of themselves from the same raw materials.

This dream, of course, also contains the seeds of the nanotechnology nightmare – the so-called “grey goo” scenario. With machines containing assemblers, replicators and possibly nanocomputers, what is to stop them escaping, evolving, and running amok? It is an issue that all nanotechnologists are forced to address at some point. Their answers vary.

Paul Green believes that the capacity to evolve should not be built into such machines. Evolution should remain firmly as part of the design, and not in the manufacturing process. Eric Drexler suggests that nanomachines will be essentially fragile things, able to survive only under specific, and friendly, conditions. Perhaps they will contain instructions that limit the number of replications they can undergo; or they may be “doped” to die without a specific “antidote” which is available only in their proper working environment.

“Worrying about runaway nanotechnology is like worrying about a car leaving behind roads, gas stations and hydraulic fluid to live in the woods,” says Drexler.

Even without runaway grey goo, nanotechnology gives pause for thought. The industrial revolution changed every aspect of our society, creating the forces that shaped the modern world in which we live. Nanotechnology has the ability to turn that world upside-down once more. However unlikely the most dramatic scenarios of the nanotechnologists, their consequences are so far-reaching that mankind needs to think about them. Hard. And soon.

Seven steps to atomic scale

Computer chip : five millimetres

Grain of sand : one millimetre

Human hair : Fifty micron

Acoustical filter : One micron

Nanomachine : 100 nanometres

DNA molecule : Two nanometres

Individual atoms : One-tenth of a nanometre

Source

The Next Small Thing

Author: Matt Bacon

News Service: Nanocentral

URL: http://www.theexperiment.com/articles.php3?news_id=741