Published on Kurzweilai.net Dec. 1, 2003.

Nanotechnology pioneer Eric Drexler and Rice University Professor and Nobelist Richard Smalley have engaged in a crucial debate on the feasibility of molecular assembly, which is the key to the most revolutionary capabilities of nanotechnology.  Although Smalley was originally inspired by Drexler's ground-breaking works and has himself become a champion of contemporary research initiatives in nanotechnology, he has also taken on the role of key critic of Drexler's primary idea of precisely guided molecular manufacturing. 

This debate has picked up intensity with today's publication of several rounds of this dialogue between these two pioneers.  First some background:

Background: The Roots of Nanotechnology

Nanotechnology promises the tools to rebuild the physical world, our bodies and brains included, molecular fragment by molecular fragment, potentially atom by atom.  We are shrinking the key feature size of technology, in accordance with what I call the "law of accelerating returns," at the exponential rate of approximately a factor of 4 per linear dimension per decade.  At this rate, the key feature sizes for most electronic and many mechanical technologies will be in the nanotechnology range, generally considered to be under 100 nanometers, by the 2020s (electronics has already dipped below this threshold, albeit not yet in three-dimensional structures and not self-assembling).  Meanwhile, there has been rapid progress, particularly in the last several years, in preparing the conceptual framework and design ideas for the coming age of nanotechnology. 

Most nanotechnology historians date the conceptual birth of nanotechnology to physicist Richard Feynman's seminal speech in 1959, "There's Plenty of Room at the Bottom," in which he described the profound implications and the inevitability of engineering machines at the level of atoms:

"The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom.  It would be, in principle, possible. . . .for a physicist to synthesize any chemical substance that the chemist writes down. . .How?  Put the atoms down where the chemist says, and so you make the substance.  The problems of chemistry and biology can be greatly helped if our ability to see what we are doing, and to do things on an atomic level, is ultimately developed – a development which I think cannot be avoided."

An even earlier conceptual root for nanotechnology was formulated by the information theorist John Von Neumann in the early 1950s with his model of a self-replicating system based on a universal constructor combined with a universal computer.  In this proposal, the computer runs a program that directs the constructor, which in turn constructs a copy of both the computer (including its self-replication program) and the constructor.  At this level of description, Von Neumann's proposal is quite abstract -- the computer and constructor could be made in a great variety of ways, as well as from diverse materials, and could even be a theoretical mathematical construction.  He took the concept one step further and proposed a "kinematic constructor," a robot with at least one manipulator (arm) that would build a replica of itself from a "sea of parts" in its midst. 

It was left to Eric Drexler to found the modern field of nanotechnology, with a draft of his seminal Ph.D. thesis in the mid 1980s, by essentially combining these two intriguing suggestions.  Drexler described a Von Neumann Kinematic Constructor, which for its "sea of parts" used atoms and molecular fragments, as suggested in Feynman's speech.  Drexler's vision cut across many disciplinary boundaries, and was so far reaching, that no one was daring enough to be his thesis advisor, except for my own mentor, Marvin Minsky.  Drexler's doctoral thesis (premiered in his book, Engines of Creation in 1986 and articulated technically in his 1992 book Nanosystems) laid out the foundation of nanotechnology and provided the road map still being pursued today. 

Von Neumann's Universal Constructor, as applied to atoms and molecular fragments, was now called a "universal assembler."  Drexler's assembler was universal because it could essentially make almost anything in the world.  A caveat is in order here.  The products of a universal assembler necessarily have to follow the laws of physics and chemistry, so only atomically stable structures would be viable.  Furthermore, any specific assembler would be restricted to building products from its sea of parts, although the feasibility of using individual atoms has been repeatedly demonstrated. 

Although Drexler did not provide a detailed design of an assembler, and such a design has still not been fully specified, his thesis did provide extensive existence proofs for each of the principal components of a universal assembler, which include the following subsystems:

• The computer: to provide the intelligence to control the assembly process.  As with all of the subsystems, the computer needs to be small and simple.  Drexler described an intriguing mechanical computer with molecular "locks" instead of transistor gates.  Each lock required only 5 cubic nanometers of space and could switch 20 billion times a second.  This proposal remains more competitive than any known electronic technology, although electronic computers built from three-dimensional arrays of carbon nanotubes may be a suitable alternative.
  
   
• The instruction architecture: Drexler and his colleague Ralph Merkle have proposed a "SIMD" (Single Instruction Multiple Data") architecture in which a single data store would record the instructions and transmit them to trillions of molecular-sized assemblers (each with their own simple computer) simultaneously.  Thus each assembler would not have to store the entire program for creating the desired product.  This "broadcast" architecture also addresses a key safety concern by shutting down the self-replication process if it got out of control by terminating the centralized source of the replication instructions.  However, as Drexler points out[1], a nanoscale assembler does not necessarily have to be self-replicating. Given the inherent dangers in self-replication, the ethical standards proposed by the Foresight Institute contain prohibitions against unrestricted self-replication, especially in a natural environment.
  
   
• Instruction transmission: transmission of the instructions from the centralized data store to each of the many assemblers would be accomplished electronically if the computer is electronic or through mechanical vibrations if Drexler's concept of a mechanical computer were used. 
  
   
• The construction robot: the constructor would be a simple molecular robot with a single arm, similar to Von Neumann's kinematic constructor, but on a tiny scale.  The feasibility of building molecular-based robot arms, gears, rotors, and motors has been demonstrated in the years since Drexler's thesis, as I discuss below.
  
   
• The robot arm tip: Drexler's follow-up book in 1992, Nanosystems: molecular machinery, manufacturing, and computation, provided a number of feasible chemistries for the tip of the robot arm that would be capable of grasping (using appropriate atomic force fields) a molecular fragment, or even a single atom, and then depositing it in a desired location.  We know from the chemical vapor deposition process used to construct artificial diamonds that it is feasible to remove individual carbon atoms, as well as molecular fragments that include carbon, and then place them in another location through precisely controlled chemical reactions at the tip.  The process to build artificial diamond is a chaotic process involving trillions of atoms, but the underlying process has been harnessed to design a robot arm tip that can remove hydrogen atoms from a source material and deposit it at desired location in a molecular machine being constructed.  In this proposal, the tiny machines are built out of a diamond-like (called "diamondoid") material.  In addition to having great strength, the material can be doped with impurities in a precise fashion to create electronic components such as transistors.  Simulations have shown that gears, levers, motors, and other mechanical systems can also be constructed from these carbon arrays.  Additional proposals have been made in the years since, including several innovative designs by Ralph Merkle[2].  In recent years, there has been a great deal of attention on carbon nanotubes, comprised of hexagonal arrays of carbon atoms assembled in three dimensions, which are also capable of providing both mechanical and electronic functions at the molecular level. 
  
   
• The assembler's internal environment needs to prevent environmental impurities from interfering with the delicate assembly process.  Drexler's proposal is to maintain a near vacuum and build the assembler walls out of the same diamondoid material that the assembler itself is capable of making. 
  
   
• The energy required for the assembly process can be provided either through electricity or through chemical energy.  Drexler proposed a chemical process with the fuel interlaced with the raw building material.  More recent proposals utilize nanoengineered fuel cells incorporating hydrogen and oxygen or glucose and oxygen.

Although many configurations have been proposed, the typical assembler has been described as a tabletop unit that can manufacture any physically possible product for  which we have a software description.  Products can range from computers, clothes, and works of art to cooked meals.  Larger products, such as furniture, cars, or even houses, can be built in a modular fashion, or using larger assemblers.  Of particular importance, an assembler can create copies of itself.  The incremental cost of creating any physical product, including the assemblers themselves, would be pennies per pound, basically the cost of the raw materials.  The real cost, of course, would be the value of the information describing each type of product, that is the software that controls the assembly process.  Thus everything of value in the world, including physical objects, would be comprised essentially of information.  We are not that far from this situation today, since the "information content" of products is rapidly asymptoting to 100 percent of their value. 

In operation, the centralized data store sends out commands simultaneously to all of the assembly robots.  There would be trillions of robots in an assembler, each executing the same instruction at the same time.  The assembler creates these molecular robots by starting with a small number and then using these robots to create additional ones in an iterative fashion, until the requisite number of robots has been created. 

Each local robot has a local data storage that specifies the type of mechanism it is building.  This local data storage is used to mask the global instructions being sent from the centralized data store so that certain instructions are blocked and local parameters are filled in.  In this way, even though all of the assemblers are receiving the same sequence of instructions, there is a level of customization to the part being built by each molecular robot.  Each robot extracts the raw materials it needs, which includes individual carbon atoms and molecular fragments, from the source material.  This source material also includes the requisite chemical fuel.  All of the requisite design requirements, including routing the instructions and the source material, were described in detail in Drexler's two classic works.

The Biological Assembler

Nature shows that molecules can serve as machines because living things work by means of such machinery.  Enzymes are molecular machines that make, break, and rearrange the bonds holding other molecules together.  Muscles are driven by molecular machines that haul fibers past one another.  DNA serves as a data-storage system, transmitting digital instructions to molecular machines, the ribosomes, that manufacture protein molecules.  And these protein molecules, in turn, make up most of the molecular machinery.

 -- Eric Drexler

The ultimate existence proof of the feasibility of a molecular assembler is life itself.  Indeed, as we deepen out understanding of the information basis of life processes, we are discovering specific ideas to address the design requirements of a generalized molecular assembler.  For example, proposals have been made to use a molecular energy source of glucose and ATP similar to that used by biological cells. 

Consider how biology solves each of the design challenges of a Drexler assembler.  The ribosome represents both the computer and the construction robot.  Life does not use centralized data storage, but provides the entire code to every cell.  The ability to restrict the local data storage of a nanoengineered robot to only a small part of the assembly code (using the "broadcast" architecture), particularly when doing self-replication, is one critical way nanotechnology can be engineered to be safer than biology. 

With the advent of full-scale nanotechnology in the 2020s, we will have the potential to replace biology's genetic information repository in the cell nucleus with a nanoengineered system that would maintain the genetic code and simulate the actions of RNA, the ribosome, and other elements of the computer in biology's assembler.  There would be significant benefits in doing this.  We could eliminate the accumulation of DNA transcription errors, one major source of the aging process.  We could introduce DNA changes to essentially reprogram our genes (something we'll be able to do long before this scenario, using gene-therapy techniques). 

With such a nanoengineered system, the recommended broadcast architecture could enable us to turn off unwanted replication, thereby defeating cancer, autoimmune reactions, and other disease processes.  Although most of these disease processes will have already been defeated by genetic engineering, reengineering the computer of life using nanotechnology could eliminate any remaining obstacles and create a level of durability and flexibility that goes vastly beyond the inherent capabilities of biology.

Life's local data storage is, of course, the DNA strands, broken into specific genes on the chromosomes.  The task of instruction-masking (blocking genes that do not contribute to a particular cell type) is controlled by the short RNA molecules and peptides that govern gene expression.  The internal environment the ribosome is able to function in is the particular chemical environment maintained inside the cell, which includes a particular acid-alkaline equilibrium (pH between 6.8 and 7.1 in human cells) and other chemical balances needed for the delicate operations of the ribosome.  The cell wall is responsible for protecting this internal cellular environment from disturbance by the outside world. 

The robot arm tip would use the ribosome's ability to implement enzymatic reactions to break off each amino acid, each bound to a specific transfer RNA, and to connect it to its adjoining amino acid using a peptide bond. 

However, the goal of molecular manufacturing is not merely to replicate the molecular assembly capabilities of biology.  Biological systems are limited to building systems from protein, which has profound limitations in strength and speed.  Nanobots built from diamondoid gears and rotors can be thousands of times faster and stronger than biological cells.  The comparison is even more dramatic with regard to computation: the switching speed of nanotube-based computation would be millions of times faster than the extremely slow transaction speed of the electrochemical switching used in mammalian interneuronal connections (typically around 200 transactions per second, although the nonlinear transactions that take place in the dendrites and synapses are more complex than single computations). 

The concept of a diamondoid assembler described above uses a consistent input material (for construction and fuel).  This is one of several protections against molecule-scale replication of robots in an uncontrolled fashion in the outside world.  Biology's replication robot, the ribosome, also requires carefully controlled source and fuel materials, which are provided by our digestive system.  As nano-based replicators become more sophisticated, more capable of extracting carbon atoms and carbon-based molecular fragments from less well-controlled source materials, and able to operate outside of controlled replicator enclosures such as in the biological world, they will have the potential to present a grave threat to that world, particularly in view of the vastly greater strength and speed of nano-based replicators over any biological system.  This is, of course, the source of great controversy, which is alluded to in the Drexler-Smalley debate article and letters.

In the decade since publication of Drexler's Nanosystems, each aspect of Drexler's conceptual designs has been strengthened through additional design proposals, supercomputer simulations, and, most importantly, actual construction of molecular machines.  Boston College chemistry professor T. Ross Kelly reported in the journal Nature that his construction of a chemically-powered nanomotor was built from 78 atoms.[3]  A biomolecular research group headed by C. D. Montemagno created an ATP-fueled nanomotor.[4]  Another molecule-sized motor fueled by solar energy was created by Ben Feringa at the University of Groningen in the Netherlands out of 58 atoms.[5]  Similar progress has been made on other molecular-scale mechanical components such as gears, rotors, and levers.  Systems demonstrating the use of chemical energy and acoustic energy (as originally described by Drexler) have been designed, simulated, and, in many cases, actually constructed.  Substantial progress has been made in developing various types of electronic components from molecule-scale devices, particularly in the area of carbon nanotubes, an area that Smalley has pioneered. 

Fat and Sticky Fingers

In the wake of rapidly expanding development of each facet of future nanotechnology systems, no serious flaw to Drexler's universal assembler concept has been discovered or described.  Smalley's highly publicized objection in Scientific American [6] was based on a distorted description of the Drexler proposal; it ignored the extensive body of work in the past decade.  As a pioneer of carbon nanotubes, Smalley has gone back and forth between enthusiasm and skepticism, 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 …."

Smalley describes Drexler's assembler 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 space that a nanobot assembly robot 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 describes the "intricate three-dimensional waltz that is carried out" by five to fifteen atoms in a typical chemical reaction.  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, have a single probe, or "finger." 

Moreover, there have been extensive description and analyses of viable tip chemistries that do not involve grasping and placing atoms as if they were mechanical pieces to be deposited in place.  For example, the feasibility of moving hydrogen atoms using Drexler's "propynyl hydrogen abstraction" tip[7] has been extensively confirmed in the intervening years.[8]  The ability of the scanning probe microscope (SPM), developed at IBM in 1981, and the more sophisticated atomic force microscope to place individual atoms through specific reactions of a tip with a molecular-scale structure provide additional existence proofs.  Indeed, if Smalley's critique were valid, none of us would be here to discuss it because life itself would be impossible. 

Smalley also objects that despite "working furiously  . . . generating even a tiny amount of a product would take [a nanobot] … millions of years."  Smalley is correct, of course, that an assembler with only one nanobot wouldn't produce any appreciable quantities of a product.  However, the basic concept of nanotechnology is that we will need trillions of nanobots to accomplish meaningful results.  This is also the source of the safety concerns that have received ample attention.  Creating trillions of nanobots at reasonable cost will require the nanobots to make themselves.  This self-replication solves the economic issue while introducing grave dangers.  Biology used 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 nanobots 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.  Analysis of these designs have shown them to be thousands of times more stable in the presence of thermal effects than biological systems, so they can operate in a far wider temperature range[9].

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 20,000 times more massive than an electron.  A nanobot will be constructed from hundreds of thousands to millions of carbon and other atoms, so a nanobot will be billions of times more massive than an electron.  Plugging this ratio in the fundamental equation for quantum positional uncertainty shows this to be an insignificant factor. 

Power has represented another challenge.  Drexler's original proposals involved glucose-oxygen fuel cells, which have held up well in feasibility studies.  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.[10] 

However, recent progress in implementing MEMS-scale and even nanoscale hydrogen-oxygen fuel cells have provided an alternative approach.  Hydrogen-oxygen fuel cells, with hydrogen provided by safe methanol fuel, have made substantial progress in recent years.  A small company in Massachusetts, Integrated Fuel Cell Technologies, Inc.[11] has demonstrated a MEMS-based fuel cell.  Each postage-stamp- sized device contains thousands of microscopic fuel cells and includes the fuel lines and electronic controls.  NEC plans to introduce fuel cells based on nanotubes in 2004 for notebook computers and other portable electronics.  They claim their small power sources will power devices for up to 40 hours before the user needs to change the methanol canister. 

The Debate Heats Up

On April 16, 2003, Drexler responded to Smalley's Scientific American article with an open letter.  He cited 20 years of research by himself and others and responded specifically to the fat and sticky fingers objection.  As I discussed above, molecular assemblers were never described as having fingers at all, but rather precise positioning of reactive molecules.  Drexler cited biological enzymes and ribosomes as examples of precise molecular assembly in the natural world.  Drexler closes by quoting Smalley's own observation that "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 were published today.  Smalley responds to Drexler's open letter by backing off of his fat and sticky fingers objection and acknowledging that enzymes and ribosomes do indeed engage in the precise molecular assembly that Smalley had earlier indicated was impossible. Smalley says biological enzymes only work in water and that such water-based chemistry is limited to biological structures such as "wood, flesh and bone." As Drexler has stated[12], this is erroneous. 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. [13].

Smalley goes on to state (without any derivation or citations) that enzymatic-like reactions can only take place with biological enzymes.  This is also erroneous. It is easy to see why biological evolution adopted water-based chemistry.   Water is the most abundant substance found on our planet.  It also comprises 70 to 90 percent of our bodies, our food, and indeed of all organic matter.  Most people think of water as fairly simple, but it is a far more complex phenomenon than conventional wisdom suggests.

As every grade school child knows, water is comprised of molecules, each containing two atoms of hydrogen and one atom of oxygen, the most commonly known chemical formula, H 2O.  However, consider some of water's complications and their implications.  In a liquid state, the two hydrogen atoms make a 104.5° angle with the oxygen atom, which increases to 109.5° when water freezes.  This is why water molecules are more spread out in the form of ice, providing it with a lower density than liquid water.  This is why ice floats. 

Although the overall water molecule is electrically neutral, the placement of the electrons creates polarization effects.  The side with the hydrogen atoms is relatively positive in electrical charge, whereas the oxygen side is slightly negative.  So water molecules do not exist in isolation, rather they combine with one another in small groups to assume, typically, pentagonal or hexagonal shapes[14].  These multi-molecule structures can change back and forth between hexagonal and pentagonal configurations 100 billion times a second.   At room temperature, only about 3 percent of the clusters are hexagonal, but this increases to 100 percent as the water gets colder.  This is why snowflakes are hexagonal. 

These three-dimensional electrical properties of water are quite powerful and can break apart the strong chemical bonds of other compounds.  Consider what happens when you put salt into water.  Salt is quite stable when dry, but is quickly torn apart into its ionic components when placed in water.  The negatively charged oxygen side of the water molecules attracts positively charged sodium ions (Na⁺), while the positively charged hydrogen side of the water molecules attracts the negatively charged chlorine ions (Cl^-).  In the dry form of salt, the sodium and chlorine atoms are tightly bound together, but these bonds are easily broken by the electrical charge of the water molecules.  Water is considered "the universal solvent" and is involved in most of the biochemical pathways in our bodies.  So 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 30,000 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 our electronic technology, not unassisted 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 (diamond-like material formed into precise patterns) has been extensively studied, including the ability to remove a single hydrogen atom from a hydrogenated diamond surface.[15]  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 Institute for Molecular Manufacturing, the University of Kentucky; the United States Naval Academy, and the Xerox Palo Alto Research Center.[16]

Smalley is also ignoring the well-established scanning probe microscope mentioned above, which uses precisely controlled molecular reactions.  Building on these concepts, Ralph Merkle has described tip reactions that can involve up to four reactants.[17]  There is extensive literature on site-specific reactions that can be precisely guided and that would be feasible for the tip chemistry in a molecular assembler.[18]  Smalley ignores this body of literature when he maintains that only biological enzymes in water can perform this type of reaction.  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 by alluding once again to the extensive body of literature that Smalley ignores.  He cites the analogy to a modern factory, only at a nano-scale.  He cites analyses of transition state theory indicating that positional control would be feasible at megahertz frequencies for appropriately selected reactants. 

The latest installment of this debate is a follow-up letter by Smalley.  This letter is short on specifics and science and long on imprecise metaphors that avoid the key issues.  He writes, for example, that "much like you can't make a boy and a girl fall in love with each other simply by pushing them together, you cannot make precise chemistry occur as desired between two molecular objects with simple mechanical motion…cannot be done simply by mushing two molecular objects together."  He again acknowledges that enzymes do in fact accomplish this, but refuses to acknowledge that such reactions could take place outside of a biological-like system: "this is why I led you…..to talk about real chemistry with real enzymes….any 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."

I can understand Drexler's frustration in this debate because I have had many critics that do not bother to read or understand the data and arguments that I have presented for my own conceptions of future technologies.  Smalley's argument is of the form that "we don't have 'X' today, therefore 'X' is impossible."  I encounter this class 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.  These critics ignore the extensive list of contemporary examples of AI (for example, airplanes and weapons that fly and guide themselves, automated diagnosis of electrocardiograms and blood cell images, automated detection of credit card fraud, automated investment programs that routinely outperform human analysts, telephone-based natural language response systems, and hundreds of others) that represent working systems that are commercially available today 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.  There was a small body of thought at the beginning of the 20^th century 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?  In 1990, Kasparov scoffed at the idea that machine chess players could ever possibly defeat him.  When it happened in 1997, observers were quick to dismiss the achievement by dismissing the importance of chess. 

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 titled 'Be a Scientist, Save the World' to about 700 middle and high school students in the Spring Branch ISD, 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 assumed that self-replicating nanobots were possible, and most were deeply worried about what would happen in their future as these nanobots 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 world-wide communication networks or software viruses that would spread across them were feasible.  Today, we have both the benefits and the damage from both of these capabilities.  However, along with the danger of software viruses has also emerged a technological immune system.  While it does not completely protect us, few people would advocate eliminating the Internet in order to eliminate software viruses.  We are obtaining far more benefit than damage from this latest example of intertwined promise and peril. 

Smalley's approach to reassuring the public about the potential abuse of this future technology is not the right strategy.  Denying the feasibility of both the promise and the peril of molecular assembly will ultimately backfire and fail to guide research in the needed constructive direction.  By the 2020s, molecular assembly 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 is important that we approach this technology in a knowledgeable manner to gain the profound benefits it promises, while avoiding its dangers.  Drexler and his colleagues at the Foresight Institute have been in the forefront of developing the ethical guidelines and design considerations needed to guide the technology in a safe and constructive direction. 

Denying the feasibility of an impending technological transformation is a short-sighted strategy. 

Notes

[1] Chemical & Engineering News, December 1, 2003

[2] Ralph C. Merkle, "A proposed 'metabolism' for a hydrocarbon assembler," Nanotechnology 8 (1997): 149-162; http://www.zyvex.com/nanotech/hydroCarbonMetabolism.html.

[3] T.R. Kelly, H. De Silva, R.A. Silva, "Unidirectional rotary motion in a molecular system," Nature 401 (September 9, 1999): 150-152.

[4] C.D. Montemagno, G.D. Bachan, "Constructing nanomechanical devices powered by biomolecular motors," Nanotechnology 10 (1999): 225-231; G. D. Bachand, C.D. Montemagno, "Constructing organic / inorganic NEMS devices powered by biomolecular motors," Biomedical Microdevices 2 (2000): 179-184.

[5] N. Koumura, R.W. Zijlstra, R.A. van Delden, N. Harada, B.L. Feringa, "Light-driven monodirectional molecular rotor," Nature 401 (September 9, 1999): 152-155.

[6] Richard E. Smalley, "Of chemistry, love, and nanobots," Scientific American 285 (September, 2001): 76-77.  http://smalley.rice.edu/rick's%20publications/SA285-76.pdf.

[7] Nanosystems: molecular machinery, manufacturing, and computation, by K. Eric Drexler, Wiley 1992.

[8] See for example, Theoretical Studies of a Hydrogen Abstraction Tool for Nanotechnology, by Charles B. Musgrave, Jason K. Perry, Ralph C. Merkle, and William A. Goddard III, Nanotechnology 2, 1991 pages 187-195.

[9] See equation and explanation on page 3 of "That's Impossible!" How good scientists reach bad conclusions by Ralph C. Merkle, http://www.zyvex.com/nanotech/impossible.html. 

[10] Montemagno, C., and Bachand G.  1999 Nanotechnology 10 225.

[11] By way of disclosure, the author is an advisor and investor in this company.

[12]  Chemical & Engineering News, December 1, 2003

[13] A. Zaks and A.M. Klibanov in Science (1984, 224:1249-51)

[14] "The apparent simplicity of the water molecule belies the enormous complexity of its interactions with other molecules, including other water molecules" (A. Soper. 2002. "Water and ice." Science 297: 1288-1289). There is much that is still up for debate, as shown by the numerous articles still being published about this most basic of molecules, H₂0. For example, D. Klug. 2001. "Glassy water." Science 294:2305-2306; P. Geissler et al., 2001. "Autoionization in liquid water." Science 291(5511):2121-2124; J.K. Gregory et al. 1997. "The water dipole moment in water clusters." Science 275:814-817; and K. Liu et al. 1996. "Water clusters." Science 271:929-933;

A water molecule has slightly negative and slightly positive ends, which means water molecules interact with other water molecules to form networks. The partially positive hydrogen atom on one molecule is attracted to the partially negative oxygen on a neighboring molecule (hydrogen bonding). Three-dimensional hexamers involving 6 molecules are thought to be particularly stable, though none of these clusters lasts longer than a few picoseconds.

The polarity of water results in a number of anomalous properties. One of the best known is that the solid phase (ice) is less dense than the liquid phase. This is because the volume of water varies with the temperature, and the volume increases by about 9% on freezing. Due to hydrogen bonding, water also has a higher-than-expected boiling point.

[15] http://www.foresight.org/SciAmDebate/SciAmResponse.html, http://www.imm.org/SciAmDebate2/smalley.html, http://www.rfreitas.com/Nano/DimerTool.htm.

[16] The analysis of the hydrogen abstraction tool has involved many people, including: Donald W. Brenner, Richard J. Colton, K. Eric Drexler, William A. Goddard, III, J. A. Harrison, Jason K. Perry, Ralph C. Merkle, Charles B. Musgrave, O. A. Shenderova, Susan B. Sinnott, and Carter T. White.

[17] Ralph C. Merkle, "A proposed 'metabolism' for a hydrocarbon assembler," Nanotechnology 8(1997):149-162; http://www.zyvex.com/nanotech/hydroCarbonMetabolism.html

[18] Wilson Ho, Hyojune Lee, "Single bond formation and characterization with a scanning tunneling microscope," Science 286(26 November 1999):1719-1722; http://www.physics.uci.edu/~wilsonho/stm-iets.html.

K. Eric Drexler, Nanosystems: Molecular Machinery, Manufacturing, and Computation, John Wiley & Sons, New York, 1992, Chapter 8.

Ralph C. Merkle, "A proposed 'metabolism' for a hydrocarbon assembler," Nanotechnology 8(1997):149-162; http://www.zyvex.com/nanotech/hydroCarbonMetabolism.html.

Charles B. Musgrave, Jason K. Perry, Ralph C. Merkle, William A. Goddard III, "Theoretical studies of a hydrogen abstraction tool for nanotechnology," Nanotechnology 2(1991):187-195; http://www.zyvex.com/nanotech/Habs/Habs.html.

Michael Page, Donald W. Brenner, "Hydrogen abstraction from a diamond surface: Ab initio quantum chemical study using constrained isobutane as a model," J. Am. Chem. Soc. 113(1991):3270-3274.

Susan B. Sinnott, Richard J. Colton, Carter T. White, Donald W. Brenner, "Surface patterning by atomically-controlled chemical forces: molecular dynamics simulations," Surf. Sci. 316(1994):L1055-L1060.

D.W. Brenner, S.B. Sinnott, J.A. Harrison, O.A. Shenderova, "Simulated engineering of nanostructures," Nanotechnology 7(1996):161-167; http://www.zyvex.com/nanotech/nano4/brennerPaper.pdf

S.P. Walch, W.A. Goddard III, R.C. Merkle, "Theoretical studies of reactions on diamond surfaces," Fifth Foresight Conference on Molecular Nanotechnology, 1997; http://www.foresight.org/Conferences/MNT05/Abstracts/Walcabst.html.

Stephen P. Walch, Ralph C. Merkle, "Theoretical studies of diamond mechanosynthesis reactions," Nanotechnology 9(1998):285-296.

Fedor N. Dzegilenko, Deepak Srivastava, Subhash Saini, "Simulations of carbon nanotube tip assisted mechano-chemical reactions on a diamond surface," Nanotechnology 9(December 1998):325-330.

J.W. Lyding, K. Hess, G.C. Abeln, D.S. Thompson, J.S. Moore, M.C. Hersam, E.T. Foley, J. Lee, Z. Chen, S.T. Hwang, H. Choi, P.H. Avouris, I.C. Kizilyalli, "UHV-STM nanofabrication and hydrogen/deuterium desorption from silicon surfaces: implications for CMOS technology," Appl. Surf. Sci. 130(1998):221-230.

E.T. Foley, A.F. Kam, J.W. Lyding, P.H. Avouris, P. H. (1998), "Cryogenic UHV-STM study of hydrogen and deuterium desorption from Si(100)," Phys. Rev. Lett. 80(1998):1336-1339.

M.C. Hersam, G.C. Abeln, J.W. Lyding, "An approach for efficiently locating and electrically contacting nanostructures fabricated via UHV-STM lithography on Si(100)," Microelectronic Engineering 47(1999):235-.

L.J. Lauhon, W. Ho, "Inducing and observing the abstraction of a single hydrogen atom in bimolecular reaction with a scanning tunneling microscope," J. Phys. Chem. 105(2000):3987-3992.

Ralph C. Merkle, Robert A. Freitas Jr., “Theoretical analysis of a carbon-carbon dimer placement tool for diamond mechanosynthesis,” J. Nanosci. Nanotechnol. 3(August 2003):319-324. http://www.rfreitas.com/Nano/JNNDimerTool.pdf

Jingping Peng, Robert A. Freitas Jr., Ralph C. Merkle, “Theoretical Analysis of Diamond Mechanosynthesis. Part I. Stability of C2 Mediated Growth of Nanocrystalline Diamond C(110) Surface,” J. Comp. Theor. Nanosci. 1(March 2004). In press.

David J. Mann, Jingping Peng, Robert A. Freitas Jr., Ralph C. Merkle, “Theoretical Analysis of Diamond Mechanosynthesis. Part II. C2 Mediated Growth of Diamond C(110) Surface via Si/Ge-Triadamantane Dimer Placement Tools,” J. Comp. Theor. Nanosci. 1(March 2004). In press.

© 2003 KurzweilAI.net

Testimony presented April 9, 2003 at the Committee on Science, U.S. House of Representatives Hearing to examine the societal implications of nanotechnology and consider H.R. 766, The Nanotechnology Research and Development Act of 2003.

Summary of Testimony:

The size of technology is itself inexorably shrinking.  According to my models, both electronic and mechanical technologies are shrinking at a rate of 5.6 per linear dimension per decade.  At this rate, most of technology will be "nanotechnology" by the 2020s.

We are immeasurably better off as a result of technology, but there is still a lot of suffering in the world to overcome.  We have a moral imperative, therefore, to continue the pursuit of knowledge and advanced technologies, such as nanotechnology, that can continue to overcome human affliction.  There is also an economic imperative to continue due to the pervasive acceleration of technology, including miniaturization, in the competitive economy.

Nanotechnology is not a separate field of study that we can simply relinquish.  We will have no choice but to confront the challenge of guiding nanotechnology in a constructive direction.  There are strategies we can deploy, but there will need to be continual development of defensive strategies. 

We can take some level of comfort from our relative success in dealing with one new form of fully non-biological, self-replicating pathogen: the software virus. 

The most immediate danger is not self-replicating nanotechnology, but rather self-replicating biotechnology.  We need to place a much higher priority on developing vitally needed defensive technologies such as antiviral medications.  Keep in mind that a bioterrorist does not need to put his "innovations" through the FDA. 

Any broad attempt to relinquish nanotechnology will only push it underground, which would interfere with the benefits while actually making the dangers worse.

Existing regulations on the safety of foods, drugs, and other materials in the environment are sufficient to deal with the near-term applications of nanotechnology, such as nanoparticles.

Full Verbal Testimony:

Chairman Boehlert, distinguished members of the U.S. House of Representatives Committee on Science, and other distinguished guests, I appreciate this opportunity to respond to your questions and concerns on the vital issue of the societal implications of nanotechnology.  Our rapidly growing ability to manipulate matter and energy at ever smaller scales promises to transform virtually every sector of society, including health and medicine, manufacturing, electronics and computers, energy, travel, and defense.  There will be increasing overlap between nanotechnology and other technologies of increasing influence, such as biotechnology and artificial intelligence.  As with any other technological transformation, we will be faced with deeply intertwined promise and peril.

In my brief verbal remarks, I only have time to summarize my conclusions on this complex subject, and I am providing the Committee with an expanded written response that attempts to explain the reasoning behind my views. 

Eric Drexler's 1986 thesis developed the concept of building molecule-scale devices using molecular assemblers that would precisely guide chemical reactions.  Without going through the history of the controversy surrounding feasibility, it is fair to say that the consensus today is that nano-assembly is indeed feasible, although the most dramatic capabilities are still a couple of decades away.

 The concept of nanotechnology today has been expanded to include essentially any technology where the key features are measured in a modest number of nanometers (under 100 by some definitions).  By this standard, contemporary electronics has already passed this threshold. 

For the past two decades, I have studied technology trends, along with a team of researchers who have assisted me in gathering critical measures of technology in different areas, and I have been developing mathematical models of how technology evolves.  Several conclusions from this study have a direct bearing on the issues before this hearing.  Technologies, particularly those related to information, develop at an exponential pace, generally doubling in capability and price-performance every year.  This observation includes the power of computation, communication – both wired and wireless, DNA sequencing, brain scanning, brain reverse engineering, and the size and scope of human knowledge in general.  Of particular relevance to this hearing, the size of technology is itself inexorably shrinking.  According to my models, both electronic and mechanical technologies are shrinking at a rate of 5.6 per linear dimension per decade.  At this rate, most of technology will be "nanotechnology" by the 2020s. 

The golden age of nanotechnology is, therefore, a couple of decades away.  This era will bring us the ability to essentially convert software, i.e., information, directly into physical products.  We will be able to produce virtually any product for pennies per pound.  Computers will have greater computational capacity than the human brain, and we will be completing the reverse engineering of the human brain to reveal the software design of human intelligence.  We are already placing devices with narrow intelligence in our bodies for diagnostic and therapeutic purposes.  With the advent of nanotechnology, we will be able to keep our bodies and brains in a healthy, optimal state indefinitely.  We will have technologies to reverse environmental pollution.  Nanotechnology and related advanced technologies of the 2020s will bring us the opportunity to overcome age-old problems, including pollution, poverty, disease, and aging. 

We hear increasingly strident voices that object to the intermingling of the so-called natural world with the products of our technology.  The increasing intimacy of our human lives with our technology is not a new story, and I would remind the committee that had it not been for the technological advances of the past two centuries, most of us here today would not be here today. Human life expectancy was 37 years in 1800.  Most humans at that time lived lives dominated by poverty, intense labor, disease, and misfortune.  We are immeasurably better off as a result of technology, but there is still a lot of suffering in the world to overcome.  We have a moral imperative, therefore, to continue the pursuit of knowledge and of advanced technologies that can continue to overcome human affliction.

There is also an economic imperative to continue.   Nanotechnology is not a single field of study that we can simply relinquish, as suggested by Bill Joy's essay, "Why the Future Doesn't Need Us."  Nanotechnology is advancing on hundreds of fronts, and is an extremely diverse activity.  We cannot relinquish its pursuit without essentially relinquishing all of technology, which would require a Brave New World totalitarian scenario, which is inconsistent with the values of our society. 

Technology has always been a double-edged sword, and that is certainly true of nanotechnology.  The same technology that promises to advance human health and wealth also has the potential for destructive applications.  We can see that duality today in biotechnology.  The same techniques that could save millions of lives from cancer and disease may also empower a bioterrorist to create a bioengineered pathogen. 

A lot of attention has been paid to the problem of self-replicating nanotechnology entities that could essentially form a nonbiological cancer that would threaten the planet. I discuss in my written testimony steps we can take now and in the future to ameliorate these dangers. However, the primary point I would like to make is that we will have no choice but to confront the challenge of guiding nanotechnology in a constructive direction.  Any broad attempt to relinquish nanotechnology will only push it underground, which would interfere with the benefits while actually making the dangers worse. 

As a test case, we can take a small measure of comfort from how we have dealt with one recent technological challenge. There exists today a new form of fully nonbiological self-replicating entity that didn't exist just a few decades ago: the computer virus.  When this form of destructive intruder first appeared, strong concerns were voiced that as they became more sophisticated, software pathogens had the potential to destroy the computer network medium they live in. Yet the "immune system" that has evolved in response to this challenge has been largely effective. Although destructive self-replicating software entities do cause damage from time to time, the injury is but a small fraction of the benefit we receive from the computers and communication links that harbor them. No one would suggest we do away with computers, local area networks, and the Internet because of software viruses. 

One might counter that computer viruses do not have the lethal potential of biological viruses or of destructive nanotechnology. This is not always the case: we rely on software to monitor patients in critical care units, to fly and land airplanes, to guide intelligent weapons in our current campaign in Iraq, and other "mission critical" tasks. To the extent that this is true, however, this observation only strengthens my argument.  The fact that computer viruses are not usually deadly to humans only means that more people are willing to create and release them.  It also means that our response to the danger is that much less intense.  Conversely, when it comes to self-replicating entities that are potentially lethal on a large scale, our response on all levels will be vastly more serious, as we have seen since 9-11. 

I would describe our response to software pathogens as effective and successful.  Although they remain (and always will remain) a concern, the danger remains at a nuisance level.  Keep in mind that this success is in an industry in which there is no regulation, and no certification for practitioners.  This largely unregulated industry is also enormously productive.  One could argue that it has contributed more to our technological and economic progress than any other enterprise in human history.  

Some of the concerns that have been raised, such as Bill Joy's article, are effective because they paint a picture of future dangers as if they were released on today's unprepared world.  The reality is that the sophistication and power of our defensive technologies and knowledge will grow along with the dangers. 

The challenge most immediately in front of us is not self-replicating nanotechnology, but rather self-replicating biotechnology.  The next two decades will be the golden age of biotechnology, whereas the comparable era for nanotechnology will follow in the 2020s and beyond.  We are now in the early stages of a transforming technology based on the intersection of biology and information science.  We are learning the "software" methods of life and disease processes.  By reprogramming the information processes that lead to and encourage disease and aging, we will have the ability to overcome these afflictions.  However, the same knowledge can also empower a terrorist to create a bioengineered pathogen. 

As we compare the success we have had in controlling engineered software viruses to the coming challenge of controlling engineered biological viruses, we are struck with one salient difference.  As I noted, the software industry is almost completely unregulated.  The same is obviously not the case for biotechnology.  A bioterrorist does not need to put his "innovations" through the FDA.  However, we do require the scientists developing the defensive technologies to follow the existing regulations, which slow down the innovation process at every step.  Moreover, it is impossible, under existing regulations and ethical standards, to test defenses to bioterrorist agents on humans.  There is already extensive discussion to modify these regulations to allow for animal models and simulations to replace infeasible human trials.  This will be necessary, but I believe we will need to go beyond these steps to accelerate the development of vitally needed defensive technologies. 

With the human genome project, 3 to 5 percent of the budgets were devoted to the ethical, legal, and social implications (ELSI) of the technology.  A similar commitment for nanotechnology would be appropriate and constructive. 

Near-term applications of nanotechnology are far more limited in their benefits as well as more benign in their potential dangers.  These include developments in the materials area involving the addition of particles with multi-nanometer features to plastics, textiles, and other products.  These have perhaps the greatest potential in the area of pharmaceutical development by allowing new strategies for highly targeted drugs that perform their intended function and reach the appropriate tissues, while minimizing side effects.  This development is not qualitatively different than what we have been doing for decades in that many new materials involve constituent particles that are novel and of a similar physical scale.  The emerging nanoparticle technology provides more precise control, but the idea of introducing new nonbiological materials into the environment is hardly a new phenomenon.  We cannot say a priori that all nanoengineered particles are safe, nor would it be appropriate to deem them necessarily unsafe.  Environmental tests thus far have not shown reasons for undue concern, and it is my view that existing regulations on the safety of foods, drugs, and other materials in the environment are sufficient to deal with these near-term applications. 

The voices that are expressing concern about nanotechnology are the same voices that have expressed undue levels of concern about genetically modified organisms.  As with nanoparticles, GMO's are neither inherently safe nor unsafe, and reasonable levels of regulation for safety are appropriate.  However, none of the dire warnings about GMO's have come to pass.  Already, African nations, such as Zambia and Zimbabwe, have rejected vitally needed food aid under pressure from European anti-GMO activists.  The reflexive anti-technology stance that has been reflected in the GMO controversy will not be helpful in balancing the benefits and risks of nanoparticle technology. 

In summary, I believe that existing regulatory mechanisms are sufficient to handle near-term applications of nanotechnology.  As for the long term, we need to appreciate that a myriad of nanoscale technologies are inevitable.  The current examinations and dialogues on achieving the promise while ameliorating the peril are appropriate and will deserve sharply increased attention as we get closer to realizing these revolutionary technologies. 

Written Testimony

I am pleased to provide a more detailed written response to the issues raised by the committee.  In this written portion of my response, I address the following issues:

• Models of Technology Trends: A discussion of why nanotechnology and related advanced technologies are inevitable.  The underlying technologies are deeply integrated into our society and are advancing on many diverse fronts.
• A Small Sample of Examples of True Nanotechnology: a few of the implications of nanotechnology two to three decades from now.
• The Economic Imperatives of the Law of Accelerating Returns: the exponential advance of technology, including the accelerating miniaturization of technology, is driven by economic imperative, and, in turn, has a pervasive impact on the economy. 
• The Deeply Intertwined Promise and Peril of Nanotechnology and Related Advanced Technologies: Technology is inherently a doubled-edged sword, and we will need to adopt strategies to encourage the benefits while ameliorating the risks.  Relinquishing broad areas of technology, as has been proposed, is not feasible and attempts to do so will only drive technology development underground, which will exacerbate the dangers. 

Models of Technology Trends

A diverse technology such as nanotechnology progresses on many fronts and is comprised of hundreds of small steps forward, each benign in itself.  An examination of these trends shows that technology in which the key features are measured in a small number of nanometers is inevitable.  I hereby provide some examples of my study of technology trends. 

The motivation for this study came from my interest in inventing.  As an inventor in the 1970s, I came to realize that my inventions needed to make sense in terms of the enabling technologies and market forces that would exist when the invention was introduced, which would represent a very different world than when it was conceived.  I began to develop models of how distinct technologies – electronics, communications, computer processors, memory, magnetic storage, and the size of technology – developed and how these changes rippled through markets and ultimately our social institutions.   I realized that most inventions fail not because they never work, but because their timing is wrong.  Inventing is a lot like surfing, you have to anticipate and catch the wave at just the right moment. 

In the 1980s, my interest in technology trends and implications took on a