Part 11 (1/2)

In the wake of the rapidly expanding development of each facet of future nanotechnology systems, no serious flaw in Drexler's nanoa.s.sembler concept has been described. A highly publicized objection in 2001 by n.o.belist Richard Smalley in Scientific American Scientific American was based on a distorted description of the Drexler proposal; was based on a distorted description of the Drexler proposal;92 it did not address the extensive body of work that has been carried out in the past decade. As a pioneer of carbon nanotubes Smalley has been enthusiastic about a variety of applications of nanotechnology, having written that ”nanotechnology holds the answer, to the extent there are answers, to most of our pressing material needs in energy, health, communication, transportation, food, water,” but he remains skeptical about molecular nanotechnology a.s.sembly. it did not address the extensive body of work that has been carried out in the past decade. As a pioneer of carbon nanotubes Smalley has been enthusiastic about a variety of applications of nanotechnology, having written that ”nanotechnology holds the answer, to the extent there are answers, to most of our pressing material needs in energy, health, communication, transportation, food, water,” but he remains skeptical about molecular nanotechnology a.s.sembly.

Smalley describes Drexler's a.s.sembler as consisting of five to ten ”fingers” (manipulator arms) to hold, move, and place each atom in the machine being constructed. He then goes on to point out that there isn't room for so many fingers in the cramped s.p.a.ce in which a molecular-a.s.sembly nanorobot has to work (which he calls the ”fat fingers” problem) and that these fingers would have difficulty letting go 'of their atomic cargo because of molecular attraction forces (the ”sticky fingers” problem). Smalley also points out that an ”intricate three-dimensional waltz ... is carried out” by five to fifteen atoms in a typical chemical reaction.

In fact, Drexler's proposal doesn't look anything like the straw-man description that Smalley criticizes. Drexler's proposal, and most of those that have followed, uses a single ”finger.” Moreover, there have been extensive descriptions and a.n.a.lyses of viable tip chemistries that do not involve grasping and placing atoms as if they were mechanical pieces to be deposited in place. In addition to the examples I provided above (for example, the DNA hand), the feasibility of moving hydrogen atoms using Drexler's ”propynyl hydrogen abstraction” tip has been extensively confirmed in the intervening years.93 The ability of the scanning-probe microscope (SPM), developed at IBM in 1981, and the more sophisticated atomic-force microscope (AFM) to place individual atoms through specific reactions of a tip with a molecular-scale structure provides additional proof of the concept. Recently, scientists at Osaka University used an AFM to move individual nonconductive atoms using a mechanical rather than electrical technique. The ability of the scanning-probe microscope (SPM), developed at IBM in 1981, and the more sophisticated atomic-force microscope (AFM) to place individual atoms through specific reactions of a tip with a molecular-scale structure provides additional proof of the concept. Recently, scientists at Osaka University used an AFM to move individual nonconductive atoms using a mechanical rather than electrical technique.94 The ability to move both conductive and nonconductive atoms and molecules will be needed for future molecular nanotechnology. The ability to move both conductive and nonconductive atoms and molecules will be needed for future molecular nanotechnology.95 Indeed, if Smalley's critique were valid, none of us would be here to discuss it, because life itself would be impossible, given that biology's a.s.sembler does exactly what Smalley says is impossible.

Smalley also objects that, despite ”working furiously, ... generating even a tiny amount of a product would take [a nan.o.bot] ... millions of years.” Smalley is correct, of course, that an a.s.sembler with only one nan.o.bot wouldn't produce any appreciable quant.i.ties of a product. However, the basic concept of nanotechnology is that we will use trillions of nan.o.bots to accomplish meaningful results-a factor that is also the source of the safety concerns that have received so much attention. Creating this many nan.o.bots at reasonable cost will require self-replication at some level, which while solving the economic issue will introduce potentially grave dangers, a concern I will address in chapter 8. Biology uses the same solution to create organisms with trillions of cells, and indeed we find that virtually all diseases derive from biology's self-replication process gone awry.

Earlier challenges to the concepts underlying nanotechnology have also been effectively addressed. Critics pointed out that nan.o.bots would be subject to bombardment by thermal vibration of nuclei, atoms, and molecules. This is one reason conceptual designers of nanotechnology have emphasized building structural components from diamondoid or carbon nanotubes. Increasing the strength or stiffness of a system reduces its susceptibility to thermal effects. a.n.a.lysis of these designs has shown them to be thousands of times more stable in the presence of thermal effects than are biological systems, so they can operate in a far wider temperature range.96 Similar challenges were made regarding positional uncertainty from quantum effects, based on the extremely small feature size of nanoengineered devices. Quantum effects are significant for an electron, but a single carbon atom nucleus is more than twenty thousand times more ma.s.sive than an electron. A nan.o.bot will be constructed from millions to billions of carbon and other atoms, making it up to trillions of times more ma.s.sive than an electron. Plugging this ratio in the fundamental equation for quantum positional uncertainty shows it to be an insignificant factor.97 Power has represented another challenge. Proposals involving glucose-oxygen fuel cells have held up well in feasibility studies by Freitas and others.98 An advantage of the glucose-oxygen approach is that nanomedicine applications can harness the glucose, oxygen, and ATP resources already provided by the human digestive system. A nanoscale motor was recently created using propellers made of nickel and powered by an ATP-based enzyme. An advantage of the glucose-oxygen approach is that nanomedicine applications can harness the glucose, oxygen, and ATP resources already provided by the human digestive system. A nanoscale motor was recently created using propellers made of nickel and powered by an ATP-based enzyme.99 However, recent progress in implementing MEMS-scale and even nanoscale hydrogen-oxygen fuel cells has provided an alternative approach, which I report on below. However, recent progress in implementing MEMS-scale and even nanoscale hydrogen-oxygen fuel cells has provided an alternative approach, which I report on below.

The Debate Heats Up

In April 2003 Drexler challenged Smalley's Scientific American Scientific American article with an open letter. article with an open letter.100 Citing twenty years of research by himself and others, the letter responded specifically to Smalley's fat- and sticky-fingers objections. As I discussed above, molecular a.s.semblers were never described as having fingers at all but rather relying on precise positioning of reactive molecules. Drexler cited biological enzymes and ribosomes as examples of precise molecular a.s.sembly in the natural world. Drexler closed by quoting Smalley's own observation, ”When a scientist says something is possible, they're probably underestimating how long it will take. But if they say it's impossible, they're probably wrong.” Citing twenty years of research by himself and others, the letter responded specifically to Smalley's fat- and sticky-fingers objections. As I discussed above, molecular a.s.semblers were never described as having fingers at all but rather relying on precise positioning of reactive molecules. Drexler cited biological enzymes and ribosomes as examples of precise molecular a.s.sembly in the natural world. Drexler closed by quoting Smalley's own observation, ”When a scientist says something is possible, they're probably underestimating how long it will take. But if they say it's impossible, they're probably wrong.”

Three more rounds of this debate occurred in 2003. Smalley responded to Drexler's open letter by backing off of his fat- and sticky-fingers objections and acknowledging that enzymes and ribosomes do indeed engage in the precise molecular a.s.sembly that Smalley had earlier indicated was impossible. Smalley then argued that biological enzymes work only in water and that such water-based chemistry is limited to biological structures such as ”wood, flesh and bone.” As Drexler has stated, this, too, is erroneous.101 Many enzymes, even those that ordinarily work in water, can also function in anhydrous organic solvents, and some enzymes can operate on substrates in the vapor phase, with no liquid at all. Many enzymes, even those that ordinarily work in water, can also function in anhydrous organic solvents, and some enzymes can operate on substrates in the vapor phase, with no liquid at all.102 Smalley goes on to state (without any derivation or citations) that enzymatic-like reactions can take place only with biological enzymes and in chemical reactions involving water. This is also mistaken. MIT professor of chemistry and biological engineering Alexander Klibanov demonstrated such nonaqueous (not involving water) enzyme catalysis in 1984. Klibanov writes in 2003, ”Clearly [Smalley's] statements about nonaqueous enzyme catalysis are incorrect. There have been hundreds and perhaps thousands of papers published about nonaqueous enzyme catalysis since our first paper was published 20 years ago.”103 It's easy to see why biological evolution adopted water-based chemistry. Water is a very abundant substance on our planet, and const.i.tutes 70 to 90 percent of our bodies, our food, and indeed of all organic matter. The three-dimensional electrical properties of water are quite powerful and can break apart the strong chemical bonds of other compounds. Water is considered ”the universal solvent,” and because it is involved in most of the biochemical pathways in our bodies we can regard the chemistry of life on our planet primarily as water chemistry. However, the primary thrust of our technology has been to develop systems that are not limited to the restrictions of biological evolution, which exclusively adopted water-based chemistry and proteins as its foundation. Biological systems can fly, but if you want to fly at thirty thousand feet and at hundreds or thousands of miles per hour, you would use our modern technology, not proteins. Biological systems such as human brains can remember things and do calculations, but if you want to do data mining on billions of items of information, you would want to use electronic technology, not una.s.sisted human brains.

Smalley is ignoring the past decade of research on alternative means of positioning molecular fragments using precisely guided molecular reactions. Precisely controlled synthesis of diamondoid material has been extensively studied, including the ability to remove a single hydrogen atom from a hydrogenated diamond surface104 and the ability to add one or more carbon atoms to a diamond surface. and the ability to add one or more carbon atoms to a diamond surface.105 Related research supporting the feasibility of hydrogen abstraction and precisely guided diamondoid synthesis has been conducted at the Materials and Process Simulation Center at Caltech; the department of materials science and engineering at North Carolina State University; the Inst.i.tute for Molecular Manufacturing at the University of Kentucky; the U.S. Naval Academy; and the Xerox Palo Alto Research Center. Related research supporting the feasibility of hydrogen abstraction and precisely guided diamondoid synthesis has been conducted at the Materials and Process Simulation Center at Caltech; the department of materials science and engineering at North Carolina State University; the Inst.i.tute for Molecular Manufacturing at the University of Kentucky; the U.S. Naval Academy; and the Xerox Palo Alto Research Center.106 Smalley also avoids mentioning the well-established SPM mentioned above, which uses precisely controlled molecular reactions. Building on these concepts, Ralph Merkle has described possible tip reactions that could involve up to four reactants.107 There is an extensive literature on site-specific reactions that have the potential to be precisely guided and thus could be feasible for the tip chemistry in a molecular a.s.sembler. There is an extensive literature on site-specific reactions that have the potential to be precisely guided and thus could be feasible for the tip chemistry in a molecular a.s.sembler.108 Recently, many tools that go beyond SPMs are emerging that can reliably manipulate atoms and molecular fragments. Recently, many tools that go beyond SPMs are emerging that can reliably manipulate atoms and molecular fragments.

On September 3, 2003, Drexler responded to Smalley's response to his initial letter by alluding once again to the extensive body of literature that Smalley fails to address.109 He cited the a.n.a.logy to a modern factory, only at a nanoscale. He cited a.n.a.lyses of transition-state theory indicating that positional control would be feasible at megahertz frequencies for appropriately selected reactants. He cited the a.n.a.logy to a modern factory, only at a nanoscale. He cited a.n.a.lyses of transition-state theory indicating that positional control would be feasible at megahertz frequencies for appropriately selected reactants.

Smalley again responded with a letter that is short on specific citations and current research and long on imprecise metaphors.110 He writes, for example, that ”much like you can't make a boy and a girl fall in love with each other simply by pus.h.i.+ng them together, you cannot make precise chemistry occur as desired between two molecular objects with simple mechanical motion....[It] cannot be done simply by mus.h.i.+ng two molecular objects together.” He again acknowledges that enzymes do in fact accomplish this but refuses to accept that such reactions could take place outside of a biology-like system: ”This is why I led you ... to talk about real chemistry with real enzymes....[A]ny such system will need a liquid medium. For the enzymes we know about, that liquid will have to be water, and the types of things that can be synthesized with water around cannot be much broader than meat and bone of biology.” He writes, for example, that ”much like you can't make a boy and a girl fall in love with each other simply by pus.h.i.+ng them together, you cannot make precise chemistry occur as desired between two molecular objects with simple mechanical motion....[It] cannot be done simply by mus.h.i.+ng two molecular objects together.” He again acknowledges that enzymes do in fact accomplish this but refuses to accept that such reactions could take place outside of a biology-like system: ”This is why I led you ... to talk about real chemistry with real enzymes....[A]ny such system will need a liquid medium. For the enzymes we know about, that liquid will have to be water, and the types of things that can be synthesized with water around cannot be much broader than meat and bone of biology.”

Smalley's argument is of the form ”We don't have X today, therefore X is impossible.” We encounter this cla.s.s of argument repeatedly in the area of artificial intelligence. Critics will cite the limitations of today's systems as proof that such limitations are inherent and can never be overcome. For example, such critics disregard the extensive list of contemporary examples of AI (see the section ”A Narrow AI Sampler” on p. 279) that represent commercially available working systems that were only research programs a decade ago.

Those of us who attempt to project into the future based on well-grounded methodologies are at a disadvantage. Certain future realities may be inevitable, but they are not yet manifest, so they are easy to deny. A small body of thought at the beginning of the twentieth century insisted that heavier-than-air flight was feasible, but mainstream skeptics could simply point out that if it was so feasible, why had it never been demonstrated?

Smalley reveals at least part of his motives at the end of his most recent letter when he writes:

A few weeks ago I gave a talk on nanotechnology and energy t.i.tled ”Be a Scientist, Save the World” to about 700 middle and high school students in the Spring Branch ISO, a large public school system here in the Houston area. Leading up to my visit the students were asked to write an essay on ”why I am a Nanogeek”. Hundreds responded, and I had the privilege of reading the top 30 essays, picking my favorite top 5. Of the essays I read, nearly half a.s.sumed that self-replicating nan.o.bots were possible, and most were deeply worried about what would happen in their future as these nan.o.bots spread around the world. I did what I could to allay their fears, but there is no question that many of these youngsters have been told a bedtime story that is deeply troubling.

You and people around you have scared our children.

I would point out to Smalley that earlier critics also expressed skepticism that either worldwide communication networks or software viruses that would spread across them were feasible. Today, we have both the benefits and the vulnerabilities from these capabilities. However, along with the danger of software viruses has emerged a technological immune system. We are obtaining far more gain than harm from this latest example of intertwined promise and peril.

Smalley's approach to rea.s.suring the public about the potential abuse of this future technology is not the right strategy. By denying the feasibility of nanotechnology-based a.s.sembly, he is also denying its potential. Denying both the promise and the peril of molecular a.s.sembly will ultimately backfire and will fail to guide research in the needed constructive direction. By the 2020s molecular a.s.sembly will provide tools to effectively combat poverty, clean up our environment, overcome disease, extend human longevity, and many other worthwhile pursuits. Like every other technology that humankind has created, it can also be used to amplify and enable our destructive side. It's important that we approach this technology in a knowledgeable manner to gain the profound benefits it promises, while avoiding its dangers.

Early Adopters

Although Drexler's concept of nanotechnology dealt primarily with precise molecular control of manufacturing, it has expanded to include any technology in which key features are measured by a modest number of nanometers (generally less than one hundred). Just as contemporary electronics has already quietly slipped into this realm, the area of biological and medical applications has already entered the era of nanoparticles, in which nanoscale objects are being developed to create more effective tests and treatments. Although nanoparticles are created using statistical manufacturing methods rather than a.s.semblers, they nonetheless rely on their atomic-scale properties for their effects. For example, nanoparticles are being employed in experimental biological tests as tags and labels to greatly enhance sensitivity in detecting substances such as proteins. Magnetic nanotags, for example, can be used to bind with antibodies, which can then be read using magnetic probes while still inside the body. Successful experiments have been conducted with gold nanoparticles that are bound to DNA segments and can rapidly test for specific DNA sequences in a sample. Small nanoscale beads called quantum dots can be programmed with specific codes combining multiple colors, similar to a color bar code, which can facilitate tracking of substances through the body.

Emerging micro fluidic devices, which incorporate nanoscale channels, can run hundreds of tests simultaneously on tiny samples of a given substance. These devices will allow extensive tests to be conducted on nearly invisible samples of blood, for example.

Nanoscale scaffolds have been used to grow biological tissues such as skin. Future therapies could use these tiny scaffolds to grow any type of tissue needed for repairs inside the body.

A particularly exciting application is to harness nanoparticles to deliver treatments to specific sites in the body. Nanoparticles can guide drugs into cell walls and through the blood-brain barrier. Scientists at McGill University in Montreal demonstrated a nanopill with structures in the 25- to 45-nanometer range.111 The nanopill is small enough to pa.s.s through the cell wall and delivers medications directly to targeted structures inside the cell. The nanopill is small enough to pa.s.s through the cell wall and delivers medications directly to targeted structures inside the cell.

j.a.panese scientists have created nanocages of 110 amino-acid molecules, each holding drug molecules. Adhered to the surface of each nanocage is a peptide that binds to target sites in the human body. In one experiment scientists used a peptide that binds to a specific receptor on human liver cells.112 MicroCHIPS of Bedford, Ma.s.sachusetts, has developed a computerized device that is implanted under the skin and delivers precise mixtures of medicines from hundreds of nanoscale wells inside the device.113 Future versions of the device are expected to be able to measure blood levels of substances such as glucose. The system could be used as an artificial pancreas, releasing precise amounts of insulin based on blood glucose response. It would also be capable of simulating any other hormone-producing organ. If trials go smoothly, the system could be on the market by 2008. Future versions of the device are expected to be able to measure blood levels of substances such as glucose. The system could be used as an artificial pancreas, releasing precise amounts of insulin based on blood glucose response. It would also be capable of simulating any other hormone-producing organ. If trials go smoothly, the system could be on the market by 2008.

Another innovative proposal is to guide gold nanoparticles to a tumor site, then heat them with infrared beams to destroy the cancer cells. Nanoscale packages can be designed to contain drugs, protect them through the GI tract, guide them to specific locations, and then release them in sophisticated ways, including allowing them to receive instructions from outside the body. Nanotherapeutics in Alachua, Florida, has developed a biodegradable polymer only several nanometers thick that uses this approach.114

Powering the Singularity

We produce about 14 trillion (about 1013) watts of power today in the world. Of this energy about 33 percent comes from oil, 25 percent from coal, 20 percent from gas, 7 percent from nuclear fission reactors, 15 percent from bioma.s.s and hydroelectric sources, and only 0.5 percent from renewable solar, wind, and geothermal technologies.115 Most air pollution and significant contributions to water and other forms of pollution result from the extraction, transportation, processing, and uses of the 78 percent of our energy that comes from fossil fuels. The energy obtained from oil also contributes to geopolitical tensions, and there's the small matter of its $2 trillion per year price tag for all of this energy. Although the industrial-era energy sources that dominate energy production today will become more efficient with new nanotechnology-based methods of extraction, conversion, and transmission, it's the renewable category that will need to support the bulk of future energy growth. Most air pollution and significant contributions to water and other forms of pollution result from the extraction, transportation, processing, and uses of the 78 percent of our energy that comes from fossil fuels. The energy obtained from oil also contributes to geopolitical tensions, and there's the small matter of its $2 trillion per year price tag for all of this energy. Although the industrial-era energy sources that dominate energy production today will become more efficient with new nanotechnology-based methods of extraction, conversion, and transmission, it's the renewable category that will need to support the bulk of future energy growth.

By 2030 the price-performance of computation and communication will increase by a factor of ten to one hundred million compared to today. Other technologies will also undergo enormous increases in capacity and efficiency. Energy requirements will grow far more slowly than the capacity of technologies, however, because of greatly increased efficiencies in the use of energy, which I discuss below. A primary implication of the nanotechnology revolution is that physical technologies, such as manufacturing and energy, will become governed by the law of accelerating returns. All technologies will essentially become information technologies, including energy.

Worldwide energy requirements have been estimated to double by 2030, far less than antic.i.p.ated economic growth, let alone the expected growth in the capability of technology.116 The bulk of the additional energy needed is likely to come from new nanoscale solar, wind, and geothermal technologies. It's important to recognize that most energy sources today represent solar power in one form or another. The bulk of the additional energy needed is likely to come from new nanoscale solar, wind, and geothermal technologies. It's important to recognize that most energy sources today represent solar power in one form or another.

Fossil fuels represent stored energy from the conversion of solar energy by animals and plants and related processes over millions of years (although the theory that fossil fuels originated from living organisms has recently been challenged). But the extraction of oil from high-grade oil wells is at a peak, and some experts believe we may have already pa.s.sed that peak. It's clear, in any case, that we are rapidly depleting easily accessible fossil fuels. We do have far larger fossil-fuel resources that will require more sophisticated technologies to extract cleanly and efficiently (such as coal and shale oil), and they will be part of the future of energy. A billion-dollar demonstration plant called FutureGen, now being constructed, is expected to be the world's first zero-emissions energy plant based on fossil fuels.117 Rather than simply burn coal, as is done today, the 275-million-watt plant will convert the coal to a synthetic gas comprising hydrogen and carbon monoxide, which will then react with steam to produce discrete streams of hydrogen and carbon dioxide, which will be sequestered. The hydrogen can then be used in fuel cells or else converted into electricity and water. Key to the plant's design are new materials for membranes that separate hydrogen and carbon dioxide. Rather than simply burn coal, as is done today, the 275-million-watt plant will convert the coal to a synthetic gas comprising hydrogen and carbon monoxide, which will then react with steam to produce discrete streams of hydrogen and carbon dioxide, which will be sequestered. The hydrogen can then be used in fuel cells or else converted into electricity and water. Key to the plant's design are new materials for membranes that separate hydrogen and carbon dioxide.