Nanotechnology and the tendency to miniaturization in the manufacturing industry are familiar to most people employed in the microelectronics and computer industry. Nevertheless, nanotechnology has already been introduced into other scientific and technological areas as well, like robotics, biology and medicine, fiber optic communication networks, aerospace technology, advanced materials technology, chemical engineering and precision manufacturing. Two interlinked trends are involved, the trend towards miniaturization and the trend towards ultraprecision processing. Ultraprecision processes are already extensively applied in manufacturing industry, for example, in manufacturing of car and aircraft engines by improving their performance and in manufacturing of optical parts, such as lenses and mirrors, by obtaining high quality surfaces, replacing, therefore, “traditional” manufacturing methods. On the order hand, in order to observe and measure at the nanometer scale, new instruments and measuring techniques, that provide this ability, are developed. By employing principles of physics, various new methods are used, such as atomic force microscopy, laser position measurement and tunneling electron microscopy. These techniques also allow for manipulating objects on the atomic scale and putting an atom or a molecule on a designated location.
The original idea for the development of nanotechnology comes from the area of microelectronics and its applications in computer systems. According to this manufacturing concept, the smaller the particles are, the reduced is their manufacturing cost and the higher is their productivity. This has already been achieved in the chips industry as it can be seen by comparing the size and the speeds of computers of the 1980s and today. Nanotechnology is made possible through technological advances made in several disciplines, where the commercial opportunities, arisen from engineering research in this field, are usefully classified.
As already mentioned, the two main trends in the miniaturization of products are the ultraprecision and the nanotechnology processing. By ultraprecision processing, defined are these processes by which the highest possible dimensional accuracy has been achieved at a given time. It is carried out by machine tools with very high accuracy. Nanotechnology is defined as the fabrication of devices with atomic or molecular scale precision, but it also includes all devices with size less than 100 nm. It is perhaps today's most advanced manufacturing technology and is usually called “extreme technology” or “bottom-up” manufacturing because it reaches the theoretical limit of accuracy in machining, which is the size of an atom or molecule of a substance.
Sunday, November 30, 2008
Thursday, November 27, 2008
Today, ultraprecision machining refers to the achievement of dimensional tolerances of the order of 10 nm and surface roughness of 1 nm. The dimensions of parts or elements of parts produced may be as small as 1 μm and the resolution and repeatability of the machines used are of the order of 10 nm. Note, that the accuracy targets for today's ultraprecision machining cannot be achieved by simple extension of conventional machining processes, but, also, new processes are required. In order to use ultraprecision machines in the nanometer regime, three-dimensional control of the position of the tool and the workpiece is necessary. This can be achieved with CNC ultraprecision machine systems, that can provide such control, and with the aid of new measuring methods as the scanning tunneling microscopy and the atomic force microscopy. Several cutting material removal processes, depending on the desired result, are suitable for ultraprecision machining, like drilling of microholes, milling of grooves, turning of mirror-like surfaces and micropins, whilst usually, ultraprecision turning is combined with other ultraprecision processes, such as grinding. Typical products of the above processes are miniaturized machine parts mirror-like surfaces or macro-components with ultraprecision finished smooth surfaces. Other processes are also used for performing ultraprecision cutting, like EDM, ECM, laser beam machining, ultrasonic machining, micro-punching and injection molding.
At this stage, the pioneering work of the Laboratory of Manufacturing Technology of the NTUA in this field may be acknowledged. The precision and ultraprecision cutting and grinding of metals, engineering ceramics and polymers, with the aim in mind of manufacturing high-technology industrial parts, constitutes the topic of a large European Union research project with cooperation between Hungary, Ukraine, France and Greece and of subsequent forthcoming research projects .
Advancing now from the micrometer domain into the nanometer regime (fig2), it renders difficulties to use the ultraprecision processes discussed so far. For such products, new processes need to be employed.
Fig. 2. Size scale and examples of micro- and nanocomponents.
The techniques used for nanotechnology applications are the energy beam processes, based on the principle, that the energy carried on a beam can remove material by melting, vaporization or ablation. These processes have been developed during the last decade due to their application in the electronics industry and may be listed: photolithography, X-ray lithography, micro-EDM, electron beam machining, focused ion beam, laser beam machining, excimer and femtosecond lasers, scanning tunneling microscopy and atomic force microscopy
Probably, the most important application of nanotechnology is the manufacturing of microchips. By reducing the dimensions of the chip components their number on the chip can be increased, making them even faster because the electric signal has to travel less distance between them. The dimensions of chip components cannot be reduced in size any further with today's manufacturing methods, because photolithography does not permit the manufacturing of particles with dimensions of 100 nm or less. Therefore, new methods are investigated, based, either on the same physical principles as photolithography, like LIGA, which is a deep etching process based on lithography, electroplating and molding or on completely new ideas.
Electron beam machining, focused ion beam and laser beam machining are new processes, providing the energy for material removal in the form of heat. The main advantage of these methods, for both the tool and the workpiece, is the virtually zero machining force. Although the mechanical properties of the workpiece do not affect the machining process, its thermal properties, like the melting point, the boiling point and the heat capacity, greatly influence the machining characteristics, which may cause problems. Furthermore, due to the excessive heat generated on the machined surface, a heat-affected zone is developed, since the molten material remaining on the machined surface re-solidifies during cooling, whilst the structure of the layers underneath the surface changes, resulting in phase transformations in ferrous materials, which may induce residual stresses and changes in the surface hardness. A typical application of focused ion beam is the sharpening of diamond cutting tools to a cutting edge of 10 nm.
In excimer and femtosecond laser processing, very high quantum energy is induced into the workpiece, exceeding the energy among atoms, permitting each molecule to be decomposed into atoms, which are removed from the workpiece. The great advantage of this method, in contrast with the previous methods, is that the developed heat-affected layer is very small. This particular feature of these processes allows for performing very accurate cutting surfaces almost without defects. Their main disadvantages are the low machining speed and, thus, the low efficiency and the high cost of the required equipment.
Scanning tunneling microscopy is very important technology in nanotechnology, because it makes possible atom manipulation. The technique is based upon a phenomenon discovered in the 1960s, if a conducting surface is brought within 1 nm from the tip of the instrument and a potential difference is applied between the tip and the surface, then a “tunneling current” will flow. The relation of the current towards the distance is known and, thus, the machined surface can be depicted. The invention that greatly advanced nanotechnology used was the “scanning tunneling microscope”, developed in the laboratories of IBM in
Nanotechnology processes made possible the manipulation of atoms and, therefore, the design and manufacture of the nanostructured materials.
Fig. 3. Carbon nanotubes rolled with AFM
Fig. 4. A perspective view of a carbon nanotube kink junction (blue) between two electrodes (yellow) on an insulating substrate SiO2 (green).
Materials often behave in a different way when they are nanostructured. This is accomplished by having every atom or molecule in a designated location. The resulting materials and systems can be rationally designed to exhibit novel and significantly improved optical, chemical and electrical properties. For example, carbon nanotubes, are promising building blocks for nanosystems; they consist of honeycomb lattices, rolled into cylinders with atomic force microscopy, having a nanometer-scale diameter and length of about a micron (fig 3). Their weight is about one-sixth of the weight of steel the Young's modulus about five times and their tensile strength more than 100 times those of steel. They are even stronger than diamond, because their carbon–carbon band lengths are shorter than the related ones in diamond. Such materials are very light and, at the same time, very strong; therefore, they can be used as structural materials for aerospace and bone surgery applications. Furthermore, the current carrying capacity of nanometer-scale carbon wires is about 100,000 times better than that of copper, which makes them suitable for applications in integrated circuits for performing functions currently performed by semiconductor devices in electronic circuits (fig.4). Electronic devices constructed from molecules can be hundreds of times smaller than their semiconductor based counterparts. The newly invented third type of carbon, after graphite and diamond, the C60, may be used as a dry lubricant in mechanical applications.
Fig. 3. Carbon nanotubes rolled with AFM
Fig. 4. A perspective view of a carbon nanotube kink junction (blue) between two electrodes (yellow) on an insulating substrate SiO2 (green).
Nanoparticles have larger active surfaces per unit volume and mass, exhibiting greater chemical activity and, therefore, they can be used as catalysts. Nanostructured materials can also be built in such a way that they will be biocompatible for implants. The following types of metal-base nanopowders are commonly used:
Tuesday, November 25, 2008
Aluminium oxide nanopowders. The synthesized product is a highly porous white powder with the bulk density 0.6
0.7 g/cm3 and specific surface 20 m2/g. The shape of Al2O3 particles is predominantly spherical, with an average particle size varying from 30 up to 300 nm, depending on the synthesis conditions.
• Magnesium oxide whiskers. The synthesized product is a highly porous white powder. Its particles mainly have a shape of the whisker with an average diameter of 60 nm and a relation of whisker's length to its diameter about 100.
• Zirconium dioxide nanopowders. The synthesized product is a highly porous white powder with a white light yellow shade.
- Zirconium dioxide ZrO2 + 6% Y2O3, with an average size of particles 30–200 nm may be synthesized, stabilized in equilibrium tetragonal modification.
- Zirconium dioxide ZrO2, with a characteristic particle size 5 nm. The powder has cubic modification, the stabilization of which is determined by the small size of particles.
• Mixtures of nanopowders of the above listed powders during the synthesis process. The obtained powdery products are characterized by the uniformity of components allocation in the mixture. The synthesized nanopowders were utilized for modifying wolframic and non-wolframic hard facing alloys. The positive changes in material structure allow for increasing wear resistance by 150–200%, fracture toughness by 50%, stability resistance at metals treatment by cutting by 150–200%.
Nanopowders of metal oxides and carbides may also consist another group of mixtures. Turbostratum graphite with interplanar distance 3.42 Å may also form mixtures with metals like Ti, Mg, Zr; burns and metal carbides are forming by self-propagating high-temperature synthesis.
The above described nanotechnology processes need to be controlled for surface integrity and dimensional accuracy, which constitutes the field of nanometrology. Atomic force microscopy is the latest device developed for that reason but laser and X-ray interferometers are also used in nanometrology.
A specific area of nanometrology is the form measurement, e.g. the roundness or the flatness of the machined workpiece. This kind of metrology is very demanding and difficult to achieve, because there are many sources of uncertainty involved, especially in large-scale structures, like astronomical mirrors, where the measuring of roughness, dimensions and shape is essential for the functionality of the structure.
The above described nanotechnology processes need to be controlled for surface integrity and dimensional accuracy, which constitutes the field of nanometrology. Atomic force microscopy is the latest device developed for that reason but laser and X-ray interferometers are also used in nanometrology.
A specific area of nanometrology is the form measurement, e.g. the roundness or the flatness of the machined workpiece. This kind of metrology is very demanding and difficult to achieve, because there are many sources of uncertainty involved, especially in large-scale structures, like astronomical mirrors, where the measuring of roughness, dimensions and shape is essential for the functionality of the structure.
Nanotechnology has already a profound place in manufacturing in many fields of science and engineering. It appears that the computer science and medicine may be most likely affected, since they both are directed towards molecular scale manipulation of matter. Nevertheless, other fields of application, like materials science, automotive industry and space research, will be greatly benefited from the evolution of nanotechnology.
The number of individual electronic components on a microprocessor has increased from 20,000 transistors in 1980, to 125 million in the latest silicon chips, with related increase in computer power and memory. The chip structures are more compact and the large number of transistors has allowed for an increase of the computer speed, since the electrical signal has less distance to travel between two transistors. Small sizes of the microchips resulted in smaller and, yet, more powerful computer systems, which can be transported more easily. The main process used for the fabrication of microchips is photolithography. It appears, however, that this method has already reached its limitsComputer chips and the silicon-based transistors inside them are rapidly reduced in size by a factor of 4 every 3 years. According to the Semiconductor Industry Association, it is expected that the size of the circuits in the chips will reach the size of only a few atoms in about 20 years. Since, almost all modern computers are made from silicon semiconductor transistors, patterned and carved by photolithography, the predicted size reduction of the circuits may be not the most economical method for the future. An enormous amount of money has been invested in the semiconductor industry in order to consistently reduce the size and improve semiconductor electronics. Smaller circuits require less energy, operate more quickly and require less space. Currently, ultraviolet light is used to create the silicon circuits with a lateral resolution around 200 nm, which is the wavelength of ultraviolet light. As the size of the circuits reduces below 100 nm, new fabrication methods must be developed.
Data storage is another area of application of nanotechnology. Data storage devices need to be smaller and a way to succeed in this is to write and read data with more density. The atomic force microscopy is suitable for such a task. Data storage with a density of 400–500 Gb/in.2 can be achieved, about 10 times more dense than conventional magnetic data storage devices. The small size will allow for use in watches, cellular telephones, laptop computers, whilst its high-density data storage capability will lead to terabit data storage systems on 2.5 in. hard disks.
Automotive industry extensively employs electronic devices in car manufacturing, using mainly miniaturized sensors. Pressure sensors, fuel and air flow control systems, gyroscopes, accelerometers and microactuators are some of the examples of the use of nanotechnology in automotive applications. The new technology results in increased car performance and safety and, at the same time, in reduced component cost. Typical examples are the airbag accelerometers, that protect the driver from being injured after severe crash but, also, from being injured by the airbag itself, anti-skid and roll-over systems and intelligent sensors for efficient engine control. The use of nanostructured materials will further benefit the automotive industry.
Nanostructured materials and sensors, that are currently used or will be used in the future in automotive industry, is almost certain that will find application in aerospace industry as well, where the demand for safety is also great. Concentrating on space applications, it can be pointed out that the trend towards miniaturization is greater. The demand of small satellites orbiting the earth has increased over the past few years, due to special demands in communications. The Internet, mobile phones, TV stations and other domestic applications require satellites. Companies are trying to make them smaller, because it is easier to be put on orbit, maintained them there and cause little pollution, when they are put out of order. NASA is also preparing small space probes that will be able to travel to other planets; they must be as small as possible, fabricated from materials that can withstand the extreme conditions in space.
The nanotechnology applications in medicine and biology are very important on the basis that the quality of life can be improved with the use of such devices. Prosthetic implants and surgical tools, that are ultraprecision finished, are only some of the nanotechnology products already in use. Various diagnostic devices, with very small size, that enter the human body, are now available in the market, like sensors that record accurate data of the blood pressure during the “balloon inflation” treatment, performed to patients with blocked arteries. Other medical applications are related to manufacturing of miniaturized surgical instruments and diagnostic tools entering the body of the patient, like micro-catheters, with sizes smaller than 100 μm, attached to wires or optical fibers for acquiring photographs or videos from the interior of the body of the patient, and micro-cutters for the removal of arterial plaque. Furthermore, the application of laser cutting in some very delicate operations, like ophthalmic surgery, is under consideration, whilst the preparation of laminated drugs, with selective reactive molecular coatings, which will act in specific places inside the human bodies, is currently being studied.
From all that above mentioned, a big question arises. Which is the future of nanotechnology? There is not a straightforward answer, since the future of nanotechnology lies somewhere between science and fiction. The new applications and devices that are currently under investigation by scientists and engineers, promise to bring revolution to each field they will be applied. In the field of computer science, new quantum computers are designed. Automotive and aerospace industry have a demand for “systems-on-a-chip”, in which miniaturization allows all electronic systems, like computer, memory, guidance, navigation, communication, power, sensors, actuators, to fit on a tiny chip. Such systems cannot be materialized with present technologies, but their deployment will lead to a new era of computer and aviation systems, space transportation and exploration. The expectation of such systems is to reduce the cost of air transportation and make them even more reliable.
Another area the scientists are turned to is biotechnology, which can be considered as the application of biological knowledge and techniques to produce innovative materials, devices and systems. There is a great overlap among biotechnology, nanotechnology and information technology. The coupling of these technologies with other leading edge aerospace technologies can produce breakthroughs in vehicle concepts, enable new science, introduce new computer systems, and improve communications, transportation and health care.
A great number of scientists and engineers already work towards molecular nanotechnology with the prospect of “self-assembly”, where atoms and molecules are self-arranged into functioning entities without human intervention. Steps have already been taken towards manufacturing of machine components that are exclusively made of atoms. Computer simulations have shown that operations like this can be performed and the first results are very encouraging.
The future medical aspects of nanotechnology concentrate on the combination of mechanical and electrical systems with human cells and tissues. A great expectation is also the minimization of invasive surgery. New miniaturized machines will enter the human body, focus on the damaged area and proceed with its healing task. The development of new biocompatible materials will permit the replacement of damaged nerves by artificial equivalents, the restoration of hearing or sight and the improved adhesion of living tissue cells on prosthetic implants.
Interest in nanotechnology is greatly increasing worldwide leading to an extensive research funded each year. The
From the above-mentioned, it may be concluded that nanotechnology is currently in a more or less infantile stage. Nevertheless, the expectations of nanotechnology in the near future are high and the demand for advanced technology is increasing. The benefits of such advanced products and applications in many technological areas will be significant and the fields it will be applied to will lead to a new era. The impact of this technology in everyday life is considered to be great, since it will make communications, transportations, data storage, health treatment and many other technological applications faster, safer and cheaper. Some of these developments may be not materialized in the near future, but the imagination of scientists has always led technology in new paths. As the famous Greek philosopher Aristotelis recognized two millennia ago, “Knowledge of the fact is different from knowledge of the reason for the fact”.
Scientists Discover Mist Opportunity
Scientists have cracked a problem that popular opinion suggests they suffer from most: steamed-up spectacles. The solution, they found, lies in nanotechnology, the science of the vanishingly small. By applying an ultra-thin coating of particles to sheets of glass and other transparent surfaces, scientists at Massachusetts Institute of Technology made them permanently fog-proof.
Glasses steam up and car windscreens fog over when they are cold and meet warm, moist air, making thousands of tiny droplets of water condense on to the surface. The droplets scatter light as it passes through them, producing the misty, blurred effect.
The coating, a thin sandwich of transparent plastic and layers of silica particles too small to be seen with the naked eye, works by attracting water more strongly than the glass does. This flattens each of the water droplets, smearing them over the surface in a see-through layer.
"The coating basically causes water that hits the surfaces to develop a sustained sheeting effect, and that prevents fogging," said Michael Rubner, a materials scientist who led the research.
Dr Rubner, who announced the work at a meeting of the American Chemical Society in
They might find more bizarre applications. By patterning solid surfaces with the coating, Dr Rubner hopes to produce water-attracting channels that recreate a trick perfected by the
Two car manufacturers and the
Nanotechnology Unfolds Futuristic Green Cars
Automakers are constantly incorporating the most advanced technology in their lineup. This time around they are planning to use nanotechnology to come up with spectacular vehicles. Two of the most sought-after vehicles are Acura FCX 2020
Recently, automakers have unleashed their environment-friendly concept cars that are expected to be manufactured using nanotechnology. The latter is a technology of building tiny machines using functional systems at a molecular scale. According to experts, nanotechnology, in its original sense, means projected ability to assemble items from the bottom up, utilizing techniques and tools being developed these days to make complete, high performance products.
Nanotechnology works from the bottom to the inside of the machine called personal nanofactories (PNs). Using mechanochemistry, nanotechnology will facilitate control at the nanometer scale. A nanometer is one billionth of a meter. Basically, it is about the width of 3 to 4 atoms.
One of the striking future cars presented is FCX 2020
Acura FCX 2020
Another viable future car is Volkswagen Nanospyder. The captivating car is made up billions of spore-like nanobots. The car is inclusive of mouth, eyeballs and other Volkswagen car accessories including tiny logos.
One of the exciting features of this VW Nanospyder is the ability of its lead bots to pick up impending collisions. Aside from that, the information can be sent away to support particular sections of the car.
Analysts in the auto industry are expecting a greener car future because of nanotechnology. In fact, there have been interesting concept cars submitted in the upcoming Los Angeles Auto Show’s Design Challenge. The latter is a competition designed to cover future cars that are environment-friendly. Mechanics of the competition include originality, safety, environmentalism and relevancy to
Monday, November 24, 2008
Introduction of Nanotechnology and Life Extension
This article is not really about life extension. Instead, its focus is on health extension: keeping the body in a state of good health. This is a simpler topic, because we can ignore several philosophical questions. However, as the chapter unfolds, it will become clear that life extension is a natural consequence of health extension. As diseases are cured, causes of death will be avoided; as people make use of technology to improve their health, they will find themselves living longer--perhaps much longer.
A few thousand years ago, people lived about thirty years. From their point of view, we have already extended our lives to an amazing degree. However, from where we stand today, we can see that we still have a long way to go. Some people still die in their 40's from cancer, heart attack, stroke, and infections. This is tragic, and frustrating. Today's medicine is only somewhat able to deal with these and other conditions--and it has barely started to attack the problem of aging. But we can see light at the end of the tunnel.
Fifty years from now, what causes of death will be preventable? That depends largely on the technology we will have available, so let's start by projecting some technology trends. Gene sequencing and identification will be as easy as a blood sugar test. Medical devices such as artificial hearts and insulin pumps will be implantable and well-integrated with the body's natural demands. Surgical instruments will be more delicate and less destructive; what today is "major surgery" will be done with an office visit. Computers will be millions of times faster than today's machines. Last but not least, we will probably have the ability to build strong, useful, complex machines out of individual atoms and molecules. This is called "nanotechnology" or simply "nanotech", and it will make us healthier in several important ways.
Can we expect technology to solve all our medical problems? This chapter will answer that question by examining what nanotech can do for medicine. Nanotech is a huge topic, and medicine is even bigger, so this chapter can give only a sketchy overview. On the nanotech side, we will focus on robot-like machines with precise molecular parts; on the medicine side, we will limit ourselves to a mechanical view of medicine that mostly ignores the complexity that arises from all the body's systems working together. And I'll be remarkably unambitious (by future standards) in defining "good health": Good health is when the body is able to support typical activities without significant discomfort. (Optimum health is a matter of personal preference, and the chapter is long enough without getting into all the ways people could improve their bodies.) Even with these restrictions, it will become clear that nanotech can solve most or all of the medical problems that might keep us from being in good health, thus allowing us to remain in a state of good health for many decades or even centuries.
Biology and Chaos
In order to be in good health, every system in the body (including the systems we haven't discovered yet) must be functioning well. Furthermore, the states of each system must be in sync with each other so that they will keep functioning well for a reasonable period of time. If the lungs are working faster than the muscles, the blood will gain too much oxygen and lose too much carbon dioxide, which will soon throw several systems off balance. But if all your systems are working well, and working together well, then your health will be good.
An automobile can be analyzed piece by piece. If the battery is dead, the headlights won't work; the burning gasoline pushes on the piston, which makes the wheels turn; and so on. A biological organism is not so simple. Frequently there is no clear boundary between the parts--one part may have several functions, and the whole system is in constant flux. A simple mechanical analysis will miss subtleties of operation. In fact, there is a whole new branch of mathematics called chaos that had to be invented to deal with systems like this.
You may have heard of the "butterfly effect"--a butterfly flapping its wings in China may create an air current that grows into a hurricane months later. A chaotic system, such as the weather or the human body, is inherently unpredictable: no matter how precisely you know its starting state, you can't tell what it will do in the future. (As we'll see later, most butterflies do not cause hurricanes--the point is that a single butterfly can sometimes make a big difference.) In fact, the body seems to depend on chaos. Normally the timing of the heartbeat is chaotic; if it ever becomes more regular, the person is about to have a heart attack. (References are at the end of this article.)
Suppose you wanted to study the body's response to exercise. You could look at the effect of blood oxygen level on breathing rate by making a graph with oxygen level on one axis and breathing rate on the other. Measure each quantity at one-minute intervals, plot the resulting points on the graph, and draw a line between successive points. If the relationship were perfectly simple, the graph would show a diagonal line: breathing rate would increase when oxygen level went down, and decrease as oxygen level recovered. In fact, because breathing affects oxygen level with some delay, the graph will show a cycle: first the oxygen decreases, then breathing increases, then oxygen increases, then breathing decreases, and around and around it goes. On the graph, this cycle would appear as an oval. Other factors would be deforming the shape. Over time, you would notice that the tracing crossed itself repeatedly. And you'd see something else: there would be more than one oval on the graph, representing states of waking, sleep, and so on, and the lines running from one oval to another would themselves be interestingly complex. If you did the experiment for years, you would find that all the lines stayed within a certain area of the graph: the breathing rate would never be above, say, 120 breaths per minute or below one breath every three minutes.
Now consider all the vast array of bodily mechanisms and substances. You could make a 3-D graph by adding insulin to your list of things to measure. But there are hundreds of hormones in the body, as well as other chemicals, temperature (core and extremity), bacterial counts, and physical conditions including scarring and posture. You would have to make a 300-D graph! If you could do such a thing, the shape on the graph would be vastly more complex than a few ovals. Even if you could make the graph, it's not clear how much you could learn from it--the graph covers so many possibilities, and the line you plot would be so small in comparison, that even several lifetimes of data could only explore a tiny fraction of the possible states. And don't forget that the body is chaotic: even if another body seemed to begin in a similar state, it would inevitably trace a different course through the graph.
If the body is chaotic, how can it keep functioning for years at a time in a changing environment? There is a mechanism called "homeostasis" that tends to pull things back to nominal levels. If the blood sugar gets too high, extra insulin is released. If the core temperature gets too low, blood vessels in the skin contract to save heat. But even with homeostasis, there are things that can go wrong if the body is pushed too far out of whack--vicious cycles the mechanisms of the body may enter. Medicine has named and studied many of them: diabetic coma, toxic shock, fibrillation, epilepsy, Cheyne-Stokes breathing, and death. Happily, many of these conditions are reversible with a big enough push in the right direction; the next section will explore the implications of that.
Medicine and Engineering
There is no doubt that an engineering approach to medicine is doomed to be incomplete. We will never know all there is to know about how the body works, and why it goes from one state to another. Nevertheless, medicine has been quite useful for some health problems, and is certain to become even more useful. The reason for the success is that, although the "butterfly effect" is real, most of the butterflies don't count--there are billions of butterflies but only a few hurricanes. Just as there are regions of instability where the smallest butterfly can create a storm cloud, there are regions of stability where even a bird won't cause much change. The fact that we can remain alive even for one day indicates that the homeostatic mechanisms of the body are usually able to keep it in the middle of the calm, "healthy" regions of the hypothetical graph. If every small change caused huge consequences, simply eating a meal would be terribly risky.
In fact, the body's ability to keep itself on track is quite powerful. Alcohol in large doses is a poison, but in slightly smaller quantities it causes only temporary and relatively mild effects. A person's blood sugar can vary by a factor of two or three without them even being aware of it. In rare cases, people have drowned for half an hour and been restored to life. People can be kept alive for hours with their heart and lungs disconnected during open-heart surgery, and if their kidneys fail, dialysis will work for years. Furthermore, the body constantly encounters and compensates for a wide variety of perturbations--depending on the physical demands a person faces, their food intake can vary from 1000 to 8000 calories per day.
If something does go seriously wrong, it can often be put right by a remarkably simple intervention. For example, a heartbeat is a delicately orchestrated ripple of activation that spreads from nerve centers through the heart muscle. When the ripples do not move smoothly (perhaps due to insufficient blood supply during a heart attack), different areas of the heart get out of sync and start to beat out of rhythm. This is called fibrillation, and it is generally fatal. But a single massive electric shock, enough to make the heart convulse in unison, is often enough to allow it to start beating normally (and yes, chaotically) again. That something as intricate as the heart can be restarted by such unsubtle treatment is evidence that the heartbeat is actually quite robust. Continuing the example of the graph, the shock has the effect of jolting the body back into a region of stability.
It seems, then, that a minor perturbation is quite unlikely to cause any disturbance in the body's overall state of health, and even major disturbances can often be tolerated. This is not to say that we can ignore the complexity and chaos inherent in the body. We will always have to be careful of unintended side effects. However, most well-designed treatments will not have any effects that are major, unexpected, and negative. As our medical technology improves, any negative effects will be either immediately noticeable or extremely slow and subtle, giving us plenty of opportunity to detect and correct them before they pose significant threats to health. And as we learn more about where the regions of stability are and how to push the body back to them, we will be able to apply simple "engineering fixes" to more and more problems.
We can assume, then, that medicine will generally be able to correct problems without creating worse problems. It will usually be the case that symptoms of sickness can be traced to improper status of particular systems, and those problems can be corrected using straightforward techniques without causing worse problems in other systems. This is not to say that an automobile-mechanic approach to health is always best--an "integrated" approach will work better for some problems. But the point of this chapter is that even a limited, mechanistic approach can result in greatly increased lifespan.
There are several types of systems in the body. The most obvious are physical systems, such as the bones and the lungs. The physical systems are coordinated by signaling systems--patterns of chemicals or of neural activity that provide control and feedback to the various organs and tissues. DNA can be considered a system whose main purpose is to store information; it interacts with many signaling systems to produce a wide range of proteins. Metabolic systems create and destroy chemicals in order to supply the body with energy and clean up waste. The neural system senses and influences various functions, and provides both short-term and long-term information storage as well as massive information processing. The immune system fights infection, and sometimes attacks body cells as well (which may be good or bad). Some might add soul or spirit to this list. However, any soul or spirit we may have is apparently unaffected by drowning, epileptic fits, and open-heart surgery. We need not consider it in the context of medical intervention--in other words, the presence, absence, or properties of soul or spirit is irrelevant to a discussion of medical techniques.
The body's systems operate on different time scales. DNA never changes, except as a result of mutation, retroviruses, or immune system adaptation (or learning). Physical systems change over a period of days to years. Metabolic systems have a time scale of minutes to hours; signaling, seconds to minutes; immune system, seconds to days; and neural system, milliseconds to decades. A complete medical maintenance program must be able to cope with all of these time scales, as well as the size scales (from molecules to organs) and signaling methods between the various systems. This is a tall order--medicine can't do it yet. But a little advanced technology goes a long way.
Build Small, Think Big
Nanotech is the ability to build complicated shapes and/or machines with every atom in its specified place. Chemists and biologists create molecules with every atom precisely placed--but the molecules we can build today are a tiny fraction of those that are possible. Engineers build incredibly complicated and useful machines--but even the most intricate is chock-full of wasted space. We have had several "revolutions" in technology--industrial, agricultural, medical, and computer--within the last two centuries. But each of these has only given us a small fraction of the capabilities we could have. Nanotech will let us finish the job, by being much more precise in our design and fabrication of machines and by using better materials.
Let's take a look at tiny gizmos. Start by taking apart a mechanical clock--clocks are full of small parts. Set a small metal gear on the floor, and start shrinking yourself. Shrink until you're the same size as the gear, about 200 times smaller than life-size. Hold up your hand and compare it to a tooth of the gear. They're about the same size--but the gear tooth is mostly featureless, while your hand has fingers, fingernails, muscles, blood vessels, and other working parts.
You shrink again, to a tenth of your already small size. Now you are one millimeter high. You can easily see microscopic roughness on the surface of the gear, but it is random and pointless; the clock would work better if its pieces were smooth. You spot something that looks like a grain of sand: a bacterium crawling across the gear's surface. Only 1/10,000 the size of the gear it's crawling on, it is a fully functional and highly intricate machine: it contains chemical factories, a navigation system, a self-repair mechanism, and a data storage and retrieval system. Bored with the gear, you shrink again, to get a better look at the bacterium; after shrinking another thousand times, you're the same size as the single-celled wonder.
You are now about 100 times shorter than the width of a human hair. At this scale, you can see blobs inside the bacterium. Some of them are ribosomes, which manufacture protein. Some are holding tanks for chemicals. There's one blob anchoring a thrashing tail as thick as your wrist and longer than you are tall. This is the flagellum, which the bacterium uses to swim, and the blob is the motor that turns it. It's about as wide as your hand--and remember, you're shrunk by a factor of two million. You glance at the random metal crystals of the gear, and then shrink again to get a closer look at the motor. After shrinking another twenty times, the motor is as big as you are--and the atoms in the motor are still only the size of your fingernail. The whole thing is wiggling like a nest of water balloons because of thermal noise, but it still manages to process 300,000 hydrogen ions every second as an energy source. The gear, meanwhile, has become merely a featureless smear of metal atoms extending as far as you can see--from an engineering point of view, almost all of the volume of the gear is wasted space.
What if we could build machines as small and precise as the flagellar motor, with every atom carefully placed? Such machines would be about a million times as small as they are today. Take a moment to imagine that. Picture a six-story building, with each room filled floor to ceiling with machinery. A chemistry lab; a computer center; lathes and drill presses; storage bins and holding tanks; vats and furnaces; anything else you can fit in. Now imagine more buildings next to the first. Fill them up with machinery too. Put them all the way out to the horizon, from sea to shining sea. Cover an area the size of the United States with machinery six stories high! Now shrink it one million times. You'd be able to hold the whole thing in your hand--all that complexity can fit into something about the size of a plastic dropcloth. A thousand engineers working a thousand years couldn't begin to fill the available space. There are limits to the amount of complexity we'll be able to cram in, but for most applications we won't need to worry about it.
Size isn't the only advantage of nanotech. The structure of biological organisms is mostly made up of long linear molecules, wadded into tiny lumps and stuck together with static cling. Just as diamond is stronger than wood, the machines we build can use materials that biology has never been able to work with. In fact, many researchers think that 3D forms of carbon, such as diamond or "buckytubes", will make ideal building materials for nanomachines. These materials are about fifty times as strong as the best steel. When things are stronger, they can be more efficient; as marvelous as the flagellar motor is, an electrostatic motor made of diamond should be able to produce ten million times the power in the same volume!
Making Nanotech Work
For centuries, humans watched birds flying and wished they could do the same. However, today's airplanes look and function very differently from birds. We have learned that rigid wings, engines, and propellers or turbines can be used to build much larger and faster flying machines than nature ever created. Still, it was the birds that showed us it was possible.
In the same way, biology shows us that it is possible to build molecular machines--constructions of atoms that can perform intricate and useful operations at the atomic scale. An example of a machine in biology is the flagellar motor: an arrangement of protein molecules that turns chemical energy into rotating motion to help bacteria swim. Another example is the ribosome, which is made of protein and another molecule type called RNA, and is used by all living cells to make more protein by sticking amino acids together in a pattern specified by yet more molecules of RNA.
Protein, the building block of biology, has some significant limitations. A steel knife can cut even the toughest steak. Just as airplanes of aluminum and steel can fly faster than birds, a molecular machine, or nanobot, made out of stronger and stiffer materials such as diamond should be able to do things that biology cannot. Can we build such a thing? The answer is a qualified Yes--qualified only by the fact that we haven't done it yet.
In 1980, the scanning tunneling microscope (STM), which can make pictures of individual atoms, had not yet been invented. In 1990, buckytubes (incredibly strong rolled-up sheets of graphite) had not yet been discovered. Here in 2001, STMs have been used not only to make pictures of the atoms in buckytubes, but to cause a variety of chemical reactions at specific points in molecules. Buckytubes themselves, in addition to being incredibly strong, have been used to build electronic circuits. Researchers have recently developed a process for making three-dimensional plastic shapes with a resolution of 120 nanometers (nm), about 600 atoms wide, and several different techniques exist for making 2-D structures even smaller than that. Several trends indicate that by the end of this decade, we will be able to build small intricate structures while controlling the placement of each atom.
One use for small intricate structures is as machine parts. Soon after we create molecular gears and motors, we will be able to assemble them into robots ("nanomachines" or "nanobots"). A nanobot, for the purposes of this chapter, is a robot with parts of atomic scale and precision. A typical nanobot, smaller than a cell, may contain billions of atoms. But nanobots need not be small. Sometimes it's useful to fit a lot of functionality into a single device. Some nanobots may have structural application, such as reinforcing bone or replacing muscle--such devices could be quite large. The important point about a nanobot is that it can make efficient use of space, with functionality as densely packed as a bacterium.
Building structures one atom at a time will be very slow. There are 10,000,000,000,000,000,000,000 atoms in a one-carat diamond, and many times that in a potato. Every molecule in the potato was built one atom at a time (many of them by ribosomes). How can potatoes grow so fast? They contain trillions of cells, and each cell contains hundreds of ribosomes and thousands of enzymes dedicated to sticking molecules together. A simple bacterial cell can make a complete copy of itself in as little as fifteen minutes, and then both copies can duplicate themselves, and so on; one trillion cells requires only 40 replication cycles. A potato cell is more complicated than a bacterium, but with cells working in parallel to create more cells, a potato can grow in just a few weeks at very low cost.
If biology can create self-replicating devices, why can't humans design them? The answer, again speculative-but-likely, is that we can. A self-contained factory made with today's macroscopic (large-sized) technology, that can make a copy of itself from simple materials with no outside help, might be as small as 100 tons(see references). On the macroscopic scale, it's easier and cheaper to distribute the manufacturing processes and put some humans in the loop, since our hands and brains are far more capable than any robot. Nanoscale factories must be self-contained, since human hands cannot directly manipulate nanoscale objects. However, there are advantages to working with individual atoms and molecules. There are only a few dozen types of atoms that need to be manipulated to build almost any desired nanobot; the vast array of manufacturing techniques that would be needed to create a macroscopic factory from scratch will be unnecessary. Also, macroscopic parts have flaws and inaccuracies; nanoscale parts, being essentially large molecules, will be precisely identical and thus predictable enough for automated assembly. A self-replicating factory has the potential to make large quantities of product at extremely low cost.
Thus, although we have not yet built a self-replicating diamond nanobot, this chapter assumes that such a thing will exist within a few decades. Many medical problems may be solved without the use of fully-developed nanotech; the intent of this chapter is to show that nanotech can solve the rest of them, thus allowing a lifespan unlimited by disease.
Medical Techniques Using Nanotech
Medical theory and technique today are a vast improvement over the state of the art a century ago. However, by comparison with what could be, medical practice today can only be described as primitive. Surgery creates huge wounds which require days to heal. Cancer therapy usually aims to be as destructive as possible, without wiping out anything too important. Most of our drugs were discovered by trial and error, and their side effects are sometimes drastic. Organ transplantation requires crippling the immune system. Many conditions cannot be cured at all. The good news is that even basic nanotechnology can correct most if not all of these problems.
Biocompatibility
Any medical nanobot will have to interact closely with the chemicals of the body. Whatever the robot is built of, its surface must not provoke an allergic response. Most medical applications will require the detection and/or release of chemicals. The outside of a nanobot will be immersed in fluid, but the inside will probably be dry, at least with some types of mechanism. The interface between a nanomachine and the chemical environment of the body will form a large part of the design.
Carbon is an extremely versatile molecule; it can form linear or zig-zag chains, rings (benzene and other aromatic compounds), buckyballs (spherical molecules), sheets (graphite and buckytubes), or blocks (diamond). Chemists have been able to bond organic molecules to each of these forms of carbon, so we will be able to design the surface separately from the workings of the nanobot. We have been implanting gizmos into the body for decades, so we already know some materials we can use to make biocompatible surfaces. We can design surfaces that will remain separate from the body's tissues, or that will attract tissues such as bones or blood vessels to attach to them. Future research will give us more flexibility, but what we have today is good enough for most applications. Recently, researchers have even been able to make neurons grow through holes in a silicon chip, for the purpose of sensing the signals.
Each chemical compound has a certain characteristic shape, and also a pattern of electric charge on its surface. A pocket or pit of the same shape and lined with the opposite charge pattern will attract the desired chemical. This can be used to sense the presence of the chemical. If the pit is movable, it can be rotated inside the machine to take in chemicals for processing--a close-fitting pit would exclude most or all of the water and undesired chemicals, and deliver the desired chemical precisely packaged for the interior mechanism to work on. Likewise, a substance synthesized inside the machine can be moved outside; deforming the pit or changing the pattern of charge will make the chemical float away. Antibodies are nature's version of such pits; they attach themselves to chemicals with amazing specificity. Artificial pits or "binding sites" that attract specific molecules have been constructed.
Biotech researchers are already extracting molecular motors of several types from cells, and building systems to test the capabilities of the motors. Other researchers are building intricate shapes out of DNA molecules--an application nature never planned for, but potentially useful nevertheless.Research and Monitoring
A problem can't be corrected unless it is first detected. One of the first contributions nanotech will make to medicine is in the area of research. Miniaturization will create probes that gather orders of magnitude more data. Chemical sensors can be built small enough to put inside living cells. Probes may be thin enough to go through tissue without causing noticeable injury. Small, low-power devices may be implanted for continuous monitoring.
The human genome project will prove invaluable for understanding the biotechnology of the body; however, the genome is only a static record of what proteins the body is capable of making, and what molecular switches enable their manufacture. Information about the actual concentrations of proteins in living cells during the body's normal operation would be equally valuable. Such measurements could not be made today, but would be feasible with nanotech sensors capable of fitting inside single cells.
In order to detect the state of the body, information from thousands or millions of sensors would need to be coordinated. A Pentium-class nanocomputer could fit in 1/1000 the volume of a single cell. There are several ways that sensors can communicate, among themselves and with computers outside the body.
Miniaturization and efficiency would allow implanted sensors to be used full-time. Full-time sensors could detect medical problems before they became serious. In conjunction with other technologies, continuous monitoring could allow the full-time maintenance of a state of good health. Permanent implants could also interact directly with our fast systems, giving the body a continuous tuneup.
Intervention
Medical intervention generally consists of either surgery or drugs. To reach an area inside the body, the body must be cut somewhere. Drugs are usually delivered to the entire body at once. Most medical interventions today are designed to fix a specific problem, and are applied after the problem has already developed.
State of the art surgical technique uses instruments inserted through small tubes placed in small incisions. These instruments are necessarily simple; for example, a gripper or a blade. Although surgical robots are coming into use for certain delicate operations, the robots are considerably bigger than the area they operate on. We don't yet have robots that could fit through the tubes and do complicated operations on-site. Nanotech can eliminate this problem. The smallest acupuncture needle is 120 microns, or about as wide as twelve cells. 120 microns is 2,400 times as wide as a flagellar or electrostatic motor. A remarkably complex surgical robot could thus be inserted through a hole so small it doesn't even bleed.
Nanobots will probably be able to stitch tissue together at a cellular/molecular level, greatly accelerating the wound-healing process. This means that if large incisions are required, for example to replace whole organs, they can be repaired as part of the surgery. Accidental trauma will also be relatively easy to fix.
The normal way to deliver a chemical today is to dump it into either the bloodstream or the stomach, and let it spread all through the body. For some chemicals, such as insulin, this is appropriate. But for others, such as chemotherapy drugs and some antibiotics, it is best to keep them as local as possible. Nanosurgical techniques can put drug delivery devices right where they are needed. The devices can be numerous and tiny, so that they can be inserted into any organ. In most cases, the devices could manufacture the required chemicals on the spot, using elements and energy from the surrounding tissue, thus eliminating the need for holding tanks and external supply. (Nature has demonstrated that a complex chemical factory can fit into the space of a bacterium.)
Replacement
If an organ fails, we must either replace it or do without. Usually the replacement organ comes from someone else, which means that the body will reject it unless drugs are taken to cripple the immune system. Today several organs, including the larynx and the bladder, have been grown on special scaffolding. With nanotech to build far more complex and precise scaffolding, we will be able to create most organs this way from the patient's own cells, thus allowing rejection-free transplantation.
Artificial organs will become far more feasible. Today, artificial hearts have been used in a few cases, and the use of external artificial kidneys (dialysis) is common. These devices don't work very well, though they are certainly better than nothing. However, a nanotech-built device could use the body's own energy supply--glucose and oxygen--for power, and could be far more sensitive and responsive to the body's conditionRepair
oday, if a tissue is torn or cut, we must simply wait for the body to repair it. The most we can do to help is to hold the torn edges together with stitches or surgical glue. As mentioned above, nanobots should be able to re-form the molecular bonds that hold cells together, and thus repair wounds almost immediately.
Another form of injury is oxygen deprivation. Due to a blood clot or broken blood vessel, a tissue may be starved of oxygen. Normally this causes cells to kill themselves within minutes. However, drugs have already been found that tell the cells not to give up so soon; in early trials, they seem to cause significant improvement in stroke victims. A population of nanobots scattered throughout the tissues could provide more timely and targeted release of such drugs, and could also store a few minutes worth of oxygen in pressurized tanks keep the tissue alive until the wound repair machines can fix the problem.
Heterostasis
The body maintains its condition by a mechanism called homeostasis. There are hundreds of signals controlling hundreds of mechanisms, so that if part of the body starts to get out of sync with the others it is forced back in line. For the most part, these signals are sent by either chemical or neural signals. There is no overall control, and some of the signals cause undesired side effects.
Heterostasis is the idea that different parts of the body can be maintained deliberately out of sync with each other. For example, it appears that some immune diseases such as asthma may be caused by a lack of parasites. At least one doctor has deliberately infected himself with tapeworm in an effort to improve his immune function. Rather than go to such lengths, it may be possible to modify local chemical concentrations and/or the body's sensors for those chemicals, so that different systems have a slightly different picture of what's going on. It will take a lot of research to find what combinations of state are best, but it seems clear that our bodies are naturally optimized for a lifestyle different from the one we have chosen, and heterostasis may be a way to improve health.
Heterostasis may also be useful when modifying individual organs. Rather than trying to design a new organ to function precisely like the one it replaces, it may be easier to tweak the body's other systems so that they react correctly to the change. This also raises the possibility of maintaining different organs at different physiological ages for peak performance--a 90-year-old person might be healthiest with a ten-year-old liver but a 25-year-old heart.
The most extreme type of heterostasis would involve the separation of the body's components into independent subsystems, temporarily preventing all signaling between them. This would be an aggressive but straightforward treatment for massive damage or other dysfunction, in which part of the body was damaged enough to make the rest ill. Today, we can keep many organs alive for hours or even days outside the body, and we can keep the body alive for hours on a heart-lung machine. Our technology is incredibly crude in comparison with a nanotech-built interface that could simulate a healthy body in great detail. Each organ or system could thus be stabilized and repaired (or replaced) individually, without any harmful or unexpected messages from the other organs. Once everything was working well, the state of each organ would be synchronized, connections would be restored, and the body would be whole again. (When I wrote the first version of this article, in October of 2001, I thought this was a far-future possibility.Limitations of Medical Nanotech
Nanotech is technology, not magic. Although it can do a lot, there are some limits. The biggest limit will probably be waste heat. The body can usually dump about 100 watts of extra power without sweating. This sounds like a lot, but remember that nanotech motors can be far more powerful than biological ones. A single cell-sized cluster of nanotech motors could use ten watts! (Of course it would immediately overheat and burn out.) When it comes time to choose which medical devices to install in your body, you will be limited by a power budget.
Another limitation is space. Most of us imagine a cell as a bag full of watery stuff, but in fact a cell is quite full of chemicals and structural proteins. A nanobot will need to be carefully designed to avoid disrupting the mechanism, especially if it needs to move around. The good news is that some bacteria can hide in our cells, so we know it can be done.
Diseases and Cures
Medical science has scored some impressive successes. Diseases caused by bacteria have been greatly reduced by antibiotics. Vitamin and mineral deficiency diseases are almost unknown, at least in developed nations. However, we still have many diseases that limit our lifespan, and that medicine can only postpone, not cure. Life cannot be extended indefinitely without curing each disease that threatens to shorten it. This section will explore several of the worst problems and how nanotech can be used to cure them.
Telomere loss
Most cells have a length of DNA called the "telomere" that gets shorter each time they divide. After a certain number of divisions, the telomere is gone, and they die. (This is probably an anti-cancer mechanism.) If life is to be extended, cells will need to have their telomeres replaced so that they can keep working. We know that cancer cells have managed to avoid the telomere trap, and we already know of an enzyme that performs this function. It should be simple to induce a cell to lengthen its telomeres, using a machine built on the same scale as the cell that can sense its state and dispense the right chemicals at the right time.
Chemical accumulation
One cause of cell death is accumulation of harmful chemicals. The most famous type of chemical is the prion, a malformed protein that cannot be removed by the body and that causes normal protein to turn into prions. Prions are responsible for Mad Cow disease and similar human diseases. It is unclear how many other problems may be caused by the accumulation of other non-digestible chemicals. What is clear is that a diamond nanobot could make short work of breaking up a prion, or any other chemical that the body couldn't deal with on its own. Nanobots could go from cell to cell like a housecleaning service, absorbing and breaking down a variety of undesired chemicals.
DNA damage
Our genetic material is under constant attack from radiation and chemicals. Damage accumulates and causes cells to malfunction. This can be corrected in several ways. First, cells other than neurons that are malfunctioning can usually be killed; the body will replace them with no ill effects. In fact, cells contain several mechanisms for killing themselves if they detect that they are not working right. (Stem cells and other techniques can help if the body is slow to replace the missing cells.) Second, it should be possible to minimize damage by vacuuming up the chemicals that cause mutation, and by manipulating the cell's state to increase the amount of energy it spends on self-repair. Third, a nanomachine may scan each cell's DNA to search for and repair damage, or perhaps simply replace chromosomes periodically with new error-free copies.
Cancer
At a cellular level, cancers are usually quite different from normal tissue. Many cancer cells actually change the chemicals on their surface, so are easy to identify. Most of the rest grow faster or change shape. And every cancer involves a genetic change that causes a difference in the chemicals inside the cell.
The immune system already takes advantage of surface markers to destroy cancer cells; however, this is not enough to keep us cancer-free. Nanobots will have several advantages. First, they can physically enter cells and scan the chemicals inside. Second, they can have onboard computers that allow them to do calculations not available to immune cells. Third, nanobots can be programmed and deployed after a cancer is diagnosed, whereas the immune system is always guessing about whether a cancer exists. Nanobots can scan each of the body's cells for cancerous tendencies, and subject any suspicious cells to careful analysis; if a cancer is detected, they can wipe it out quickly, using more focused and vigorous tactics than the immune system is designed for.
Brain damage
The brain is unique among the body's organs: it stores our memories and personality, so that it cannot simply be replaced if it starts to wear out. This poses a special problem for life extension: the information stored in the brain must be preserved over extended periods of time, safe from disease and accident.
Obviously it is good to prevent the premature death of neurons. Poisons such as alcohol, accidents such as stroke, and diseases such as Alzheimer's can all cause neurons to die. In each of these cases, neuron death can be greatly slowed if not prevented entirely by controlling the chemistry inside the cell. Injurious chemicals can be vacuumed up and converted into harmless ones. Damaged neurons, like other cells, sometimes go into suicide mode (called "apoptosis"); as mentioned above, this can be chemically prevented, and the neuron can be stabilized until the problem is fixed and the damage is repaired.
It is now known that brain cells do regenerate: the brain is adding new ones all the time. This implies that some neural death is normal. How do the new cells know how to behave? It seems that a new neuron can take its cues from the existing ones; this means that a person's mind may be intact even after the death and replacement of a large percentage of their neurons.
Finally, it may be possible to measure neural connections and/or activity in enough detail to simulate the firing pattern. This may make it possible to create an artificial neuron or even an artificial neural net that can be used to replace missing neurons and retain old memories. But even if this proves to be impossible, the worst-case scenario is one in which people can't remember much farther than a century back. We accept more memory loss than this as a natural consequence of aging.
Hormone deficiency
Aging is associated with changes in the levels of many hormones; perhaps the best known example is menopause, which is caused by a reduction in estrogen. It is likely that treating glands against aging at the cellular level would restore age-appropriate hormone production. However, if this is not enough to bring the body to a younger state, artificial glands could be built that would maintain the desired hormone levels. In fact, different hormone levels could be supplied to different organs--something that the body cannot do for itself. This would be an example of heterostasis.
Infection
Bacteria, viruses, and parasites are continuing problems. Antibiotics work well against most bacteria; however, antibiotic-resistant strains are developing. Since viruses aren't active until they take over a cell, they are immune to antibiotics, and medicine cannot yet do much against them. There are many kinds of parasites that may need individual medical techniques.
Our immune system is quite effective at dealing with most infections. However, it needs to learn by experience--it is generally most effective at fighting organisms that it can recognize on a molecular level. Diseases can be very clever in evading it. Some diseases, such as Ebola, progress too rapidly for the immune system to respond. Syphilis survives by being stealthy and surrounding itself with the body's own chemicals to camouflage itself. Herpes splices itself into the genes of the body's cells, so the immune system can't detect it and wipe it out. HIV directly attacks the immune system.
Nanobots have several advantages over the immune system. They will not be susceptible to attack by natural pathogens. They will have computational resources unavailable to immune cells. They can be programmed to find and fight diseases they have never encountered--when a new disease shows up, as soon as it is analyzed everyone's nanobots can benefit. Likewise, the system can be activated based on external knowledge of the likelihood of a disease; the nanobots won't have to waste energy looking for malaria in winter. Nanotech will give us more options for cleaning up after a disease, since corrupted genes will be repairable without killing the affected cell.
Some diseases, such as cholera and tetanus, live in the environment; without scrubbing the whole earth, we can't get rid of them entirely, so we will need to maintain an immune system against them. But many diseases can't survive without humans to infect. With great effort, we managed to eradicate smallpox using 1970's technology. Cheap manufacturing would allow the creation of billions of doses of highly effective treatments that would be easy to distribute and administer; the main obstacles to wiping out many diseases worldwide would be political, not economic or technological.
Accidents
Accidents, especially motor vehicle accidents, are a leading cause of death at all ages. Although an accident is not itself a disease, it kills by producing damage to the body, and that damage can be treated or prevented like any other disease. Most accidents involve mechanical injury (trauma); most of the rest involve chemical injury, either poisoning or oxygen starvation. A permanent nanobot installation can make many accidents survivable that would be fatal today.
Nanobots embedded in tissue can strengthen it against tearing, or repair it if it does tear. It is common for a blow to the head to rattle the brain against the skull; a specially shaped nano-built device could cushion the brain, preventing this damage. Other devices could vacuum up common poisons before they could cause damage, or barricade poisoned areas to keep the poison from spreading through the body. Respirocytes could allow the body to function normally for several minutes without breathing or circulation, giving more opportunity to restore normal functioning. In cases of extreme injury, heterostasis could be used to stabilize the body until help can arrive. As long as the brain is not physically damaged, it can be functionally separated from the body and forced into a low-power state. With today's medicine, paramedics refer to the "golden hour": if an accident victim can be brought to a hospital in less than an hour, chance of survival is greatly increased. People have recovered after drowning in cold water for over an hour; artificial mimicry of this state, combined with the ability to aggressively repair the body, might extend the "golden hour" significantly.
Blood-related diseases
Many diseases, from heart attacks and strokes to sepsis and metastasizing cancer, involve the blood in some way. The author has proposed an aggressive nanomedical device, a "Vasculoid" , that would replace the blood volume and take over its functions by lining the entire vascular system with a multi-segmented robot. In addition to preventing many diseases, and limiting the scope of others (such as poisoning), such a system would provide detailed control of the body's chemical environment around each individual capillary, allowing heterostasis to be used extensively.
The Vasculoid is extremely complicated and would require much research to build and use successfully. This particular device may never be used, but it can provide a hint of the possibilities inherent in advanced nanomedicine.
Ethical Issues
Genetic Modification
It is likely that some conditions will be treated most easily by modifying the body's genetic material. Many people are disturbed by this idea, especially if the modification is transmissible to offspring. However, once we have a nanotechnology that can directly manipulate the genes, transmission of modified genes need not be a cause for concern. Any genetic manipulation that turns out to be a bad idea will be reversible. Furthermore, it would be trivial to edit the DNA of any offspring while still in embryo stage in order to remove the modifications. The idea that a genetic modification will irreversibly change the whole species becomes incorrect once genes can easily be directly manipulated.
Overpopulation
A common objection to life extension is that if everyone lives forever, the earth will become overcrowded. However, a little math will demonstrate that the earth can become overcrowded much faster due to excess births than due to reduced death. If everyone killed themselves after 80 years of life, that act would remove only one person from the population; meanwhile their children and grandchildren would be reproducing. But a person who chose to live a long time and have one fewer child would be reducing the population by more than one, since a nonexistent person can't have children. (Robert J. Bradbury points out that nanotechnology will also give us cheaper access to space. Using a fairly basic design (see references), it would be feasible for earth's entire population to leave the earth and live in space.)
Poor Health
Today, people are kept alive for years in terrible health, sometimes beyond the point where they wish to die. This has given life extension a bad reputation. Merely extending life without improving health is often a bad idea. The good news is that if health is improved, life will naturally be extended. Once we have the technology to eliminate diseases, we need no longer worry about living on in bad health.
Elitism
It has been argued that it would be selfish for some people to extend their lives when the technology is not available to everyone. However, life extension will not be a single technology hoarded by an elite--instead, it will be a natural consequence of health maintenance. Inequities in availability of health care are widespread today, and curing more diseases will not make the problem worse. On the other hand, development of more effective medical tools will reduce the cost of medical care. If you want to increase the availability and reduce the cost of a technology, you should invest in research and development, and buy more technology. The more people who make use of health maintenance technologies, the faster they will become cheap and widely available. (Several large private foundations are working to make medical care widely available in the developing world.)
Nanocosmetics in the news
Uncertainties surrounding the use of nanoparticles in cosmetics made the news in the
The two issues that concern Which? are some continuing uncertainties about nanoparticle safety and the fact that it hasn’t generally been made clear to consumers that nanoparticles are being used. Their head of policy, Sue Davies, emphasizes that their position isn’t blanket opposition: “We’re not saying the use of nanotechnology in cosmetics is a bad thing, far from it. Many of its applications could lead to exciting and revolutionary developments in a wide range of products, but until all the necessary safety tests are carried out, the simple fact is we just don’t know enough.” Of 67 companies approached for information about their use of nanotechnologies, only 8 replied with useful information, prompting Sue to comment: “It was concerning that so few companies came forward to be involved in our report and we are grateful for those that were responsible enough to do so. The cosmetics industry needs to stop burying its head in the sand and come clean about how it is using nanotechnology.”
On the other hand, the companies that did supply information include many of the biggest names - L’Oreal, Unilever, Nivea, Avon, Boots, Body Shop, Korres and Green People - all of whom use nanoparticulate titanium dioxide (and, in some cases, nanoparticulate zinc oxide). This makes clear just how widespread the use of these materials is (and goes someway to explaining where the estimated 130 tonnes of nanoscale titanium dioxide being consumed annually in the
The story is surprisingly widely covered by the media. Many focus on the angle of lack of consumer information, including the BBC, which reports that “consumers cannot tell which products use nanomaterials as many fail to mention it”, and the Guardin, which highlights the poor response rate. The story is also covered in the Daily Telegraph, while the Daily Mail, predictably, takes a less nuanced view. The Mail explains that “the size of the particles may allow them to permeate protective barriers in the body, such as those surrounding the brain or a developing baby in the womb.”
It may well be that these ingredients are present in such small quantities that there is no possibility of danger, but given the uncertainties surrounding fullerene toxicology putting products like this on the market doesn’t seem very smart, and is likely to cause reputational damage to the whole industry. There is a lot more data about nanoscale titanium dioxide, and the evidence that these particular nanoparticles aren’t able to penetrate healthy skin looks reasonably convincing. They deliver an unquestionable consumer benefit, in terms of screening out harmful UV rays, and the alternatives - organic small molecule sunscreens - are far from being above suspicion. But, as pointed out by the EU’s Scientific Committee on Consumer Products, there does remain uncertainty about the effect of titanium dioxide nanoparticles on damaged and sun-burned skin. Another issue recently highlighted by Andrew Maynard is the issue of the degree to which the action of light on TiO2 nanoparticles causes reactive and potentially damaging free radicals to be generated. This photocatalytic activity can be suppressed by the choice of crystalline structure (the rutile form of titanium dioxide should be used, rather than anatase), the introduction of dopants, and coating the surface of the nanoparticles. The research cited by Maynard makes it clear that not all sunscreens use grades of titanium dioxide that do completely suppress photocatalytic activity.
This poses a problem. Consumers don’t at present have ready access to information as to whether nanoscale titanium dioxide is used at all, let alone whether the nanoparticles in question are in the rutile or anatase form. Here, surely, is a case where if the companies following best practise provided more information, they might avoid their reputation being damaged by less careful operators.
Responsible nanotechnology – from discourse to practice
There were some interesting facts looking at the empirical evidence for the development, or otherwise, of regional clusters with particular strengths in nanotechnology; under discussion was the issue of whether new industries based on nanotechnologies would inevitably be attracted to existing technological clusters like Silicon Valley and the Boston area, or whether the diverse nature of the technologies grouped under this banner would diffuse this clustering effect.
From mocro to nano medical applicalions
Nanotechnology in Medicine and Biotechnology, which raised the question of what is the right size for new interventions in medicine. There’s an argument that, since the basic operations of cell biology take place on the nano-scale, that’s fundamentally the right scale for intervening in biology. On the other hand, given that many current medical interventions are very macroscopic, operating on the micro-scale may already offer compelling advantages.
Jon Cooper gave some nice examples illustrating this. His title was Integrating nanosensors with lab-on-a-chip for biological sensing in health technologies, and he began with some true nanotechnology. This involved a combination of fluid handling systems for very small volumes with nanostructured surfaces, with the aim of detecting single biomolecules. This depends on a remarkable effect known as surface enhanced Raman scattering. Raman scattering is a type of spectroscopy that can detect chemical groups with what is normally rather low sensitivity. But if one illuminates metals with very sharp asperities, this hugely magnifies the light field very close to the surface, increasing sensitivity by a factor of ten million or so. Systems based on this effect, using silver nanoparticles coated so that pathogens like anthrax will stick to them, are already in commercial use. But Cooper’s group uses, not free nano-particles, but very precisely structured nanosurfaces. Using electron beam lithography his group creates silver split-ring resonators - horseshoe shapes about 160 nm across. With a very small gap one can get field enhancements of a factor of one hundred billion, and it’s this that brings single molecule detection into prospect.
On a larger scale, Cooper described systems to probe the response of single cells - his example involved using a single heart cell (a cardiomyocyte) to screen responses to potential heart drugs. This involved a pico-litre scale microchamber adjacent to an array of micron size thermocouples, which allow one to monitor the metabolism of the cell as it responds to a drug candidate. His final example was on the millimeter scale, though its sensors incorporated nanotechnology at some level. This was a wireless device incorporating an electrochemical blood sensor - the idea was that one would swallow this to screen for early signs of bowel cancer. Here’s an example where, obviously, smaller would be better, but how small does one need to go?
What’s meant by “Food nanotechnology”?
The latter group recently released a report on food nanotechnology –Out of the laboratory and on to our plates: Nanotechnology in food and agriculture;; according to the press release, this “reveals that despite concerns about the toxicity risks of nanomaterials, consumers are unknowingly ingesting them because regulators are struggling to keep pace with their rapidly expanding use.” The position of the CIAA is essentially that nanotechnology is an interesting technology currently in research rather than having yet made it into products. One can get a good idea of the research agenda of the European food industry from the European Technology Platform Food for Life.
What makes the subject of nanotechnology particularly confusing and contentious is the ambiguity of the definition of nanotechnology when applied to food systems. Most people’s definitions are something along the lines of “the purposeful creation of structures with length scales of 100 nm or less to achieve new effects by virtue of those length-scales”. But when one attempts to apply this definition in practise one runs into difficulties, particularly for food. It’s this ambiguity that lies behind the difference of opinion we’ve heard about already today about how widespread the use of nanotechnology in foods is already. On the one hand, Friends of the Earth says they know of 104 nanofood products on the market already (and some analysts suggest the number may be more than 600). On the other hand, the CIAA (the Confederation of Food and Drink Industries of the EU) maintains that, while active research in the area is going on, no actual nanofood products are yet on the market. In fact, both parties are, in their different ways, right; the problem is the ambiguity of definition.
The issue is that food is naturally nano-structured, so that too wide a definition ends up encompassing much of modern food science, and indeed, if you stretch it further, some aspects of traditional food processing. Consider the case of “nano-ice cream”: the FoE report states that “Nestlé and Unilever are reported to be developing a nano- emulsion based ice cream with a lower fat content that retains a fatty texture and flavour”. Without knowing the details of this research, what one can be sure of is that it will involve essentially conventional food processing technology in order to control fat globule structure and size on the nanoscale. If the processing technology is conventional (and the economics of the food industry dictates that it must be), what makes this nanotechnology, if anything does, is the fact that analytical tools are available to observe the nanoscale structural changes that lead to the desirable properties. What makes this nanotechnology, then, is simply knowledge. In the light of the new knowledge that new techniques give us, we could even argue that some traditional processes, which it now turns out involve manipulation of the structure on the nanoscale to achieve some desirable effects, would constitute nanotechnology if it was defined this widely. For example, traditional whey cheeses like ricotta are made by creating the conditions for the whey proteins to aggregate into protein nanoparticles. These subsequently aggregate to form the particulate gels that give the cheese its desirable texture.
It should be clear, then, that there isn’t a single thing one can call “nanotechnology” – there are many different technologies, producing many different kinds of nano-materials. These different types of nanomaterials have quite different risk profiles. Consider cadmium selenide quantum dots, titanium dioxide nanoparticles, sheets of exfoliated clay, fullerenes like C60, casein micelles, phospholipid nanosomes – the risks and uncertainties of each of these examples of nanomaterials are quite different and it’s likely to be very misleading to generalise from any one of these to a wider class of nanomaterials.
To begin to make sense of the different types of nanomaterial that might be present in food, there is one very useful distinction. This is between engineered nanoparticles and self-assembled nanostructures. Engineered nanoparticles are covalently bonded, and thus are persistent and generally rather robust, though they may have important surface properties such as catalysis, and they may be prone to aggregate. Examples of engineered nanoparticles include titanium dioxide nanoparticles and fullerenes.
In self-assembled nanostructures, though, molecules are held together by weak forces, such as hydrogen bonds and the hydrophobic interaction. The weakness of these forces renders them mutable and transient; examples include soap micelles, protein aggregates (for example the casein micelles formed in milk), liposomes and nanosomes and the microcapsules and nanocapsules made from biopolymers such as starch.
So what kind of food nanotechnology can we expect? Here are some potentially important areas:
• Food science at the nanoscale. This is about using a combination of fairly conventional food processing techniques supported by the use of nanoscale analytical techniques to achieve desirable properties. A major driver here will be the use of sophisticated food structuring to achieve palatable products with low fat contents.
• Encapsulating ingredients and additives. The encapsulation of flavours and aromas at the microscale to protect delicate molecules and enable their triggered or otherwise controlled release is already widespread, and it is possible that decreasing the lengthscale of these systems to the nanoscale might be advantageous in some cases. We are also likely to see a range of “nutriceutical” molecules come into more general use.
• Water dispersible preparations of fat-soluble ingredients. Many food ingredients are fat-soluble; as a way of incorporating these in food and drink without fat manufacturers have developed stable colloidal dispersions of these materials in water, with particle sizes in the range of hundreds of nanometers. For example, the substance lycopene, which is familiar as the molecule that makes tomatoes red and which is believed to offer substantial health benefits, is marketed in this form by the German company BASF.
What is important in this discussion is clarity – definitions are important. We’ve seen discrepancies between estimates of how widespread food nanotechnology is in the marketplace now, and these discrepancies lead to unnecessary misunderstanding and distrust.
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