Nanomythology
Myths of nanotechnologyG.V.ERLICH Doctor of Chemical Sciences
"Chemistry and life" No. 5-2010
Any kind of human activity is overgrown with myths. Nanotechnology, the main scientific and technological project of our time, is no exception. Moreover, here myth-making concerns the very essence. Most people, even those belonging to the scientific community, are convinced that nanotechnology is primarily the manipulation of atoms and the construction of objects through the assembly of atoms. This is the main myth.
Scientific myths have a twofold nature. Some are generated by the incompleteness of our knowledge of nature or lack of information. Others are created consciously, with a specific purpose. In the case of nanotechnology, we have the second option. Thanks to this myth and its consequences, it was possible to attract the attention of those in power and dramatically accelerate the launch of the Nanotechnology project with an autocatalytic increase in investment. In fact, it was a little cheating, quite permissible by the rules of the game at the highest level. The myth played its beneficial role as the initiator of the process and was safely forgotten when it came to technology itself.
But myths have an amazing property: having been born, they begin to live their own lives, while demonstrating amazing vitality and longevity. They are so firmly rooted in people's minds that they affect the perception of reality. Real nanotechnology processes, both foreign and Rusnano projects, fundamentally contradict the myth, which creates confusion in the minds (most people still do not understand what nanotechnology is), rejection (these are not real nanotechnology!) and even the denial of nanotechnology as such.
In addition to the main myth, the history of nanotechnology shows us several related myths that excite different groups of the population, generating unreasonable hopes for some and panic fear for others.
The myth of the Founding Father
The most harmless in a series of myths is the attribution to Richard Feynman, a specialist in the field of quantum field theory and elementary particle physics, of the role of the founding father of nanotechnology. This myth arose in 1992 during the speech of the prophet of nanotechnology Eric Drexler before the Senate Committee at a hearing on "New technologies for sustainable development". To push through the nanotechnology project he invented, Drexler referred to the statement of the Nobel laureate in physics, an unshakable authority in the eyes of senators.
Unfortunately, Feynman died in 1988 and therefore could neither confirm nor deny this statement. But if he could hear it, he would probably laugh merrily. He was not only an outstanding physicist, but also a famous joker, it was not for nothing that his autobiographical book was titled: "Of course you're joking, Mr. Feynman!" The same famous speech Feynman delivered at the New Year's Eve dinner of the American Society of Physics at the California Institute of Technology was perceived accordingly. According to the memoirs of one of the participants of that meeting, the American physicist Paul Schlict: "The reaction of the audience in general can be called cheerful. Most thought that the speaker was fooling around."
But the words: "The principles of physics known to us do not prohibit the creation of objects "atom by atom". Manipulation of atoms is quite real and does not violate any laws of nature," it was said, this is a fact. The rest was a discussion on the topic of miniaturization, coupled with futurological forecasts. After a quarter of a century, some of the ideas expressed by Feynman were "creatively" developed by Eric Drexler and gave rise to the main myths of nanotechnology. Next, we will often return to this speech to remind you what Feynman actually said, and at the same time to enjoy the clarity and imagery of the great scientist's formulations.
The myth of waste-free technology
Creating an object atom by atom, we obviously use waste-free technology. The word "obviously" is used here in the most primitive sense – when people, primarily officials, look at pictures depicting the process of manipulating atoms, they do not see any waste, no smoking pipes polluting the atmosphere, and industrial effluents polluting reservoirs. By default, it is clear that dragging an almost weightless atom over a distance of several nanometers requires an insignificant amount of energy. In general, the ideal technology for "sustainable development" is a concept that was extremely popular in the 90s of the last century.
The question of where the atoms for assembly come from is almost indecent. Naturally, from the warehouse, from where they are probably delivered by environmentally friendly electric cars. The vast majority of the population generally has little idea where it comes from. For example, the materials from which various industrial goods are made, which we consume in increasing quantities. The connection of these products with the chemical industry is not visible. Chemistry as a science is boring and not really needed, and the chemical industry as certainly harmful to the environment is subject to closure.
Among other things, the chemical industry, according to the majority, consumes natural resources predationally, using oil, gas, ores, minerals for its processes. And for the new technology, as its adherents imagine, only atoms are needed: here in this compartment of the warehouse we store gold atoms, in the next – iron atoms, then sodium atoms, chlorine atoms, in general, the entire Periodic system of Mendeleev. We have to disappoint the authors of this idyllic picture: atoms by themselves, with the exception of atoms of inert gases, exist only in a vacuum, in all other conditions they interact with their own kind or other atoms, in chemical interaction with the formation of chemical compounds. That's the nature of things, and there's nothing you can do about it.
Any technology requires some devices, means of production, which also escape the attention of apologists for assembling objects from atoms. However, sometimes, on the contrary, they attract their attention and shock them to the depths of their soul. Indeed, tunneling and force microscopes are the most beautiful devices, visible evidence of the power of the human mind. And in general, the laboratories in which they manipulate atoms are an image of future technologies in the spirit of the "Third Wave" by Alvin Toffler: the so-called clean rooms with air conditioning and special air purification, devices that exclude the slightest vibration, an operator in special clothes with a university diploma in his pocket.
Will all this also be wastelessly collected from atoms? Including the foundation, walls and roof of the premises? We believe that even the most ardent adherents of this technology will not dare to answer this question in the affirmative.
Humanity will someday create waste-free, environmentally friendly technologies, but they will be based on different principles or on a fundamentally different technique.
The myth of nanomachines
Actually, initially it was about another technique. The idea that it is necessary to have a manipulator of the appropriate size for designing at the nanoscale is obvious. This is how Richard Feynman saw the implementation of this idea:
"Suppose I made a set of ten manipulator arms, reduced by four times, and connected them with wires to the original system of control levers, so that these manipulators simultaneously and accurately repeat my movements. Then I will make a set of ten manipulators of a quarter of the normal size again. Naturally, the first ten manipulators will produce 10x10 = 100 pieces of manipulators, reduced, however, by 16 times...
Nothing prevents you from continuing this process and creating as many tiny machines as you want, since this production has no restrictions related to the placement of machines and their material consumption... It is clear that this immediately removes the problem of the cost of materials. In principle, we could organize millions of identical miniature factories in which tiny machines would continuously drill holes, stamp parts, etc."
This approach is a straightforward implementation of the idea of creating miniature devices. He, albeit with many limitations, works at the micro level, as evidenced by the so-called microelectromechanical devices. They are used in airbag deployment systems in cars in case of accidents, in laser and inkjet printers, in pressure sensors, in household air conditioners and fuel level indicators in the gas tank, in pacemakers and in game console joysticks. Looking at them under a microscope, we will see our usual gears and shafts, cylinders and pistons, springs and valves, mirrors and microcircuits.
But nanoobjects have properties different from the properties of macro- and microobjects. If we find a way to proportionally reduce the size of transistors from today's 45-65 nm to 10 nm, then they simply will not work, because the electrons will begin to tunnel through the insulator layer. And the connecting wires will thin out to a chain of atoms, which will conduct current differently from massive samples, and will scatter to the sides due to thermal motion or, conversely, gather in a pile, forgetting about the task of maintaining electrical contact.
The same applies to mechanical properties. As the size decreases, the ratio of surface area to volume increases, and the larger the surface, the greater the friction. Nanoobjects are literally glued to other nanoobjects or to surfaces that seem smooth to them due to their own smallness. This is a useful quality for a gecko that easily walks on a vertical wall, but extremely harmful for any device that needs to ride or slide on a horizontal surface. In order to simply move it from its place, you will have to spend a disproportionate amount of energy.
On the other hand, inertia is small, the movement stops quickly. It is not difficult to make a nano–pendulum - attach a gold particle with a diameter of several nanometers to a carbon nanotube with a diameter of 1 nm and a length of 100 nm and hang it to a silicon plate. But this pendulum, if you swing it in the air, will stop almost immediately, because even air is a significant obstacle for it.
Nanoobjects, as they say, have high windage, they are generally easy to lead astray. Many probably observed Brownian motion in a microscope – random throwing of a small solid particle in water. Albert Einstein explained the reason for this phenomenon back in 1905: water molecules in constant thermal motion hit the surface of the particle, and the uncompensated force of impacts from different sides leads to the fact that the particle acquires momentum in one direction or another. If a particle with a size of 1 micron feels the force of small molecules and changes the direction of movement, then what about a particle with a size of 10 nm, which weighs a million times less and for which the ratio of weight to surface area is less than 100 times.
Nevertheless, in scientific and popular science literature, especially in media publications, there are constantly descriptions of nanocopies of various mechanical parts, gears, wrenches, wheels, axles and even gearboxes. It is assumed that existing models of nanomachines and other devices will be created from them. It is not necessary to treat these works with excessive seriousness, condemning, wondering or admiring. "I am personally convinced that we physicists could solve such problems just for fun or for fun," Richard Feynman said. Physicists are joking...
In fact, they are fully aware that in order to create nanomechanical or nanoelectromechanical devices, it is necessary to use structural approaches other than macro– and micro-analogs. And here, to begin with, you don't even need to invent anything, because nature has created so many different molecular machines over billions of years of evolution that ten years won't be enough for all of us to figure them out, copy them, adapt them to our needs and try to improve something.
The most famous example of a natural molecular motor is the so–called flagellar motor of bacteria. Other biological machines provide muscle contraction, heartbeat, nutrient transport and ion transport across the cell membrane. The efficiency of molecular machines that convert chemical energy into mechanical work is in many cases close to 100%. At the same time, they are extremely economical, for example, less than 1% of the energy resources of the cell are spent on the operation of electric motors that ensure the movement of bacteria.
It seems to me that the described biomimetic approach (from the Latin words "bios" – life and "mimesis" – imitation) is the most realistic way to create nanomechanical devices and one of those areas where the cooperation of physicists and biologists in the field of nanotechnology can bring tangible results.
The myth of nanorobots
Let's assume that we have created a sketch of a nanodevice on paper or on a computer screen. How would you assemble it, and preferably not in one copy? It is possible, following Feynman, to create "tiny machines that would continuously drill holes, stamp parts, etc." and miniature manipulators for assembling the finished product. These manipulators must be controlled by a person, that is, they must have some kind of macroscopic equipment or, at least, act according to a program set by a person. In addition, it is necessary to somehow observe the whole process, for example, using an electron microscope that also has macro dimensions.
An alternative idea was put forward in 1986 by American engineer Eric Drexler in the futurological bestseller "Machines of Creation". Having grown up, like all people of his generation, on the books of Isaac Asimov, he proposed using mechanical machines of appropriate (100-200 nm) sizes – nanorobots - for the production of nanodevices. It was no longer about drilling and stamping, these robots had to assemble the device directly from atoms, so they were called assemblers - assemblers. But the approach remained purely mechanical: the collector was equipped with manipulators several tens of nanometers long, an engine for moving the manipulators and the robot itself, including the previously mentioned gearboxes and transmissions, as well as an autonomous power source. It turned out that the nanorobot should consist of several tens of thousands of parts, and each part should consist of one or two hundred atoms.
The problem of visualizing atoms and molecules somehow imperceptibly dissolved, it seemed quite natural that a nanorobot operating with objects of comparable size "sees" them, as a person sees a nail and a hammer with which he hammers this nail into a wall.
The most important node of the nanorobot was, of course, the on-board computer, which controlled the operation of all the mechanisms, determined which atom or which molecule should be captured by the manipulator and where to put them in the future device. The linear dimensions of this computer should not have exceeded 40-50 nm – this is just the size of one transistor achieved by industrial technology of our time, 25 years after Drexler wrote the book "Machines of Creation".
But Drexler also addressed his book to the future, to the distant future. At the time of writing, scientists have not yet confirmed even the fundamental possibility of manipulating individual atoms, let alone assembling at least some structures from them. It happened only four years later. The device used for this purpose for the first time and used until now – the tunneling microscope – has quite tangible dimensions, tens of centimeters in each dimension, and is controlled by a person using a powerful computer with billions of transistors.
The dream idea of nanorobots collecting materials and devices from individual atoms was so beautiful and tempting that this discovery only gave it credibility. Within a few years, US senators, journalists, who were far from science, believed in it, and from their submission – the public and, quite surprisingly, the author himself, who continued to defend it even when it was clearly explained to him that the idea was unrealizable in principle. There are many arguments against such mechanical devices, we will cite only the simplest one put forward by Richard Smalley: a manipulator that "captures" an atom will be connected to it forever due to chemical interaction. Smalley was a Nobel Prize winner in chemistry, that was probably the point.
But the idea continued to live its life and has survived to the present day, noticeably more complicated and supplemented with various applications.
The myth of medical nanorobots
The most popular myth is about millions of nanorobots that will prowl around our body, diagnose the condition of various cells and tissues, repair breakdowns using a nanoscalpel, dissect and dismantle cancer cells, build up bone tissue by assembling atoms, scrape cholesterol plaques with a nanoload, and selectively break synapses responsible for unpleasant memories in the brain. And also to report on the work done, transmitting messages through the nanoantenna like: "Alex to Eustace. Damage to the mitral valve was revealed. The breakdown has been eliminated." It is the latter that causes serious public concern, because it is the disclosure of private information – the message of the nanorobot can be received and decrypted not only by a doctor, but also by outsiders. This concern confirms that people believe in everything else unconditionally. Just like in nanorobots-spies, in "smart dust", which will penetrate into our apartments, watch us, eavesdrop on our conversations and again transmit the received video and audio materials through a nanotransmitter with a nanoantenna. Or into killer nanorobots, hitting people and equipment with nanoparticles, perhaps even nuclear ones.
The most amazing thing is that almost everything described can be created (and something has already been created). And invasive diagnostic systems that report on the state of the body, and drugs that act on certain cells, and systems that clean our blood vessels from atherosclerotic plaques, and bone buildup, and erasing memories, and invisible remote tracking systems, and "smart dust".
However, all these systems of the present and future have and will have nothing to do with mechanical nanorobots in the spirit of Drexler, except for size. They will be created by the joint efforts of physicists, chemists and biologists, scientists working in the field of synthetic science called nanotechnology.
The myth of the physical method of synthesis of substances
In his lecture, Richard Feynman unwittingly revealed the secret age-old dream of physicists:
"And finally, thinking in this direction (the possibility of manipulating atoms. – G.E.), we come to the problems of chemical synthesis. Chemists will come to us, physicists, with specific orders: "Listen, friend, will you make a molecule with such and such a distribution of atoms?" Chemists themselves use complex and even mysterious operations and techniques to prepare molecules. Usually, for the synthesis of the intended molecule, they have to mix, shake and process various substances for quite a long time. As soon as physicists create a device capable of operating individual atoms, all this activity will become unnecessary... Chemists will order synthesis, and physicists will simply "stack" the atoms in the right order."
Chemists don't synthesize a molecule, chemists get a substance. Substance, its production and transformations are a subject of chemistry that is still mysterious to physicists.
A molecule is a group of atoms, not just stacked in the right order, but also connected by chemical bonds. A transparent liquid in which two hydrogen atoms account for one oxygen atom may be water, or it may be a mixture of liquid hydrogen and oxygen (attention: do not mix at home!).
Suppose we somehow managed to put together a bunch of eight atoms–two carbon atoms and six hydrogen atoms. To the physicist, this bunch will probably appear to be an ethane molecule with 2 H 6, but the chemist will indicate at least two more possibilities for connecting atoms.
Let's say we want to get ethane by assembling it from atoms. How can this be done? Where to start: move two carbon atoms or attach a hydrogen atom to a carbon atom? A question for backfilling, including for the author. The problem is that scientists have so far learned how to manipulate atoms, firstly, heavy, and secondly, not very reactive. Rather complex structures are assembled from xenon, gold, and iron atoms. How to operate with light and extremely active atoms of hydrogen, carbon, nitrogen and oxygen is not entirely clear. So with the atomic assembly of proteins and nucleic acids, which some authors say is practically solved, we will have to wait.
There is another circumstance that significantly limits the prospects of the "physical" synthesis method. As already mentioned, chemists do not synthesize a molecule, but receive a substance. The substance consists of a huge number of molecules. 1 ml of water contains ~3x10 22 water molecules. Let's take a more familiar object for nanotechnology – gold. A 1 cm3 gold cube contains ~6x10 22 gold atoms. How long will it take to assemble such a cube of atoms?
To this day, working on an atomic force or tunneling microscope is akin to art, no wonder it requires a special and very good education. The work is manual: hook the atom, drag it to the right place, evaluate the intermediate result. The speed is approximately like brickwork. In order not to frighten the reader with unthinkable numbers, let's assume that we have found a way to somehow mechanize and intensify the process and can stack a million atoms per second. In this case, we will spend two billion years assembling a cube with a volume of 1 cm3, about the same time as it took nature to create the whole living world and ourselves as the crown of evolution by trial and error.
That is why Feynman spoke about millions of "factories", without, however, assessing their possible productivity. That is why even a million nanorobots scurrying around inside us will not solve the problem, because we will not have enough life to wait for the result of their labors. That is why Richard Smalley urged Eric Drexler to exclude from public speeches any mention of "creation machines" in order not to mislead the public with this anti-scientific nonsense.
So, is it possible to put an end to this method of obtaining substances, materials and devices? No, not at all.
Firstly, using the same technique, it is possible to manipulate not atoms, but significantly larger building blocks, for example carbon nanotubes. At the same time, the problems of light and reactive atoms are removed, and productivity will automatically increase by two or three orders of magnitude. This, of course, is still too little for real technology, but by this method scientists are already getting single copies of the simplest nanodevices in laboratories.
Secondly, it is possible to come up with many situations when the introduction of an atom, nanoparticles, or even just the physical impact of a tunneling microscope needle initiates the process of self-organization, physical or chemical transformations in the medium. For example, a chain reaction of polymerization in a thin film of organic matter, changes in the crystal structure of an inorganic substance or the conformation of a biopolymer in a certain neighborhood of the impact point. High-precision scanning of the surface and repeated exposure will make it possible to create extended objects characterized by a regular nanostructure.
And finally, this method can be used to obtain unique template samples for further reproduction by other methods. For example, a hexagon of metal atoms or a single molecule. But how to multiply a single molecule? Impossible, you say, this is some kind of unscientific fiction. Why is that? Nature is perfectly able to create multiple, absolutely identical copies of both individual molecules and whole organisms. In everyday life, this is called cloning. Even people who are far from science, but have visited a modern medical diagnostic laboratory at least once, have heard about the polymerase chain reaction. This reaction makes it possible to multiply a single fragment of a DNA molecule extracted from biological material or synthesized artificially by chemical means. To do this, scientists use "molecular machines" created by nature – proteins and enzymes. Why can't we make similar machines for cloning other molecules, not just oligonucleotides?
I will risk paraphrasing Richard Feynman a little: "The principles of chemistry known to us do not prohibit cloning single molecules. The "reproduction" of molecules according to the sample is quite real and does not violate any laws of nature."
The myth of "grey slime"
Elementary consideration of extremely low (by mass) the performance of nanorobots, of course, did not pass by the attention of Eric Drekeler. There were other problems in the world of "creation machines" that we did not discuss in detail due to lack of space, for example, quality control, mastering the release of new products and sources of raw materials, where and how atoms appear in the "warehouse". To solve these problems, Drexler introduced two more types of devices into the concept.
The first is the pickers, the antipodes of the pickers. The disassembler, in particular, must study the structure of a new object by writing its atomic structure into the memory of the nanocomputer. Not a device, but a dream, a dream of chemists! Despite all the achievements of modern research technology, we do not "see" all the atoms, for example, in a protein. It is possible to establish the exact structure of a molecule only if it forms a crystal together with millions of other similar molecules. Then, using the method of X-ray diffraction analysis, we can determine the exact location of all atoms in space, up to thousandths of a nanometer. This is a long, time-consuming procedure that requires cumbersome and expensive equipment.
The second type of devices are creators, or replicators. Their main tasks are the in–line production of assemblers and the assembly of similar replicators, that is, reproduction. According to their creator, replicators are much more complex devices than simple assemblers, they should consist of hundreds of millions of atoms (two orders of magnitude smaller than in a DNA molecule) and, accordingly, have a size of about 1000 nm. If the duration of their replication is measured in minutes, then, multiplying exponentially, they will create trillions of replicators in a day, they will produce quadrillions of specialized assemblers who will begin assembling macro objects, houses or rockets.
It is easy to imagine a situation when the functioning of the system will go into production mode for the sake of production, unrestrained accumulation of the means of production – the nanorobots themselves, when all their activities will be reduced to increasing their own population. Such is the revolt of the machines of the era of nanotechnology. For their own construction, nanorobots can get atoms only from the environment, so the disassemblers will begin to disassemble into atoms everything that falls under their tenacious manipulators. As a result, after some time, all matter and, most offensively for us, biomass will turn into a cluster of nanorobots, into "gray slime", as Eric Drexler figuratively called it.
Each new technology generates scenarios of the inevitable end of the world, due to its introduction and distribution. The myth of gray slime is only historically the first such scenario associated with nanotechnology. But he is very imaginative, which is why journalists and cinematographers love him so much.
Fortunately, such a scenario is not possible. If, despite all of the above, you still believe in the possibility of assembling something substantial from atoms, think about two circumstances. Firstly, the replicators described by Drexler do not have enough complexity to create similar devices. A hundred million atoms is not enough even to create a computer controlling the assembly process, even for memory. If we assume the unattainable – that each atom carries one bit of information, then the amount of this memory will be 12.5 megabytes, and this is too little. Secondly, replicators will have problems with raw materials. The elemental composition of electromechanical devices is fundamentally different from the composition of environmental objects and, first of all, from biomass. The search, extraction and delivery of atoms of the necessary elements, which require a huge expenditure of time and energy, is what will determine the speed of reproduction. If you project the situation on a macro scale, then this is the same as assembling a machine from materials that need to be found, extracted, and then delivered from various planets of the Solar System. The lack of vital resources puts a limit to the unrestrained spread of any populations that are much more adapted and perfect than the mythical nanorobots.
Conclusion
The list of myths can be continued. The myth of nanotechnology as the locomotive of the economy is worthy of a separate article. Earlier in the article "Nanotechnology as a national idea" (see "Chemistry and Life", 2008, No. 3), we tried to dispel the myth that the "National Nanotechnology Initiative" of the USA is a purely technological project.
The canonical history of nanotechnology is also a myth, the key event of which is the invention of the tunneling electron microscope. The latter is easily explained. "History is written by the winners," and a global project called "Nanotechnology", which largely determines the face (and funding) of modern science, has been penetrated by physicists. For which we all, researchers working in this and related fields, express our infinite gratitude to physicists.
Myths have played a positive role, they have generated enthusiasm and attracted the attention of the political and economic elite, as well as the public to nanotechnology. However, at the stage of practical implementation of nanotechnology, it's time to forget about these myths and stop repeating them from article to article, from book to book. After all, myths slow down development, set wrong guidelines and goals, generate misunderstanding and fears. And finally, it is necessary to write a new history of nanotechnology – a new science of the XXI century, the field of natural science, combining physics, chemistry and biology.
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