It has been well known for a long time that the metabolisms of smaller animals are faster when compared to the metabolisms of larger animals relative to their body size. In 1883, German physiologist Max Rubner tried to define a scaling principle based on the laws of thermodynamics and geometry. The metabolism of an organism works like a perfect machine that continuously converts one form of energy into others. It also releases energy while doing so. Metabolic speed can be described as the speed at which cells convert nutrients into energy. This energy is utilized for the execution of cellular functions and the construction of new cells.

Calculations have shown that the speed of metabolism is directly proportionate to body mass. For instance, the biomass of a hamster is eight times bigger than a mouse. According to this ratio, one would expect the metabolism of a hamster to be eight times faster than that of a mouse. Similarly, the body mass of a hippopotamus is 125,000 times larger than a mouse; therefore its metabolism would be estimated to be 125,000 times faster.

The problem is that a hamster generates eight times more heat than a mouse. Furthermore, the total body surface area, which is how the heat energy leaves the hamster?s body, is four times bigger than the surface area a mouse has. Consequently, as the body of an organism grows, its surface area develops more slowly compared to its mass.

This situation is shown in Figure 1. Here a mouse, a hamster, and a hippopotamus are represented in spheres. As the spheres get larger, their volume and surface area also gets bigger. In geometry we know that the volume of a sphere is given as? ?(r is the radius of the sphere). The surface area of a sphere is also expressed as . In this case we can say that while the volume of a sphere is scaled with the cubed radius, the surface area of a sphere is scaled with the squared radius. In other terms, the volume of a sphere is directly proportionate to the cubed radius, as is the surface area of the sphere to the squared radius.

Figure 1. The scaled features of a mouse, hamster, and hippopotamus. Taken from Complexity: A Guided Tour by Melanie Mitchell, Oxford University Press.

Figure 1 displays the first model used by scientists when the relation between metabolic speed, body mass, and surface area was being investigated. According to this early model, the association between body mass, surface area, and volume was studied with spheres that encased organisms. As the volume of the sphere approximately provided the volume of the organism, the sphere?s surface area also represented the surface area of the organism (of their skin). According to this, the radius of the sphere containing the hamster is nearly twice as large as the radius of the sphere with the mouse. Therefore, it can be claimed that the volume of a hamster is approximately eight times the volume of a mouse, and its surface area is four times larger. When it comes to the hippopotamus; the radius of the sphere is 50 times larger than the one with the mouse; this shows it has a 2500 times wider surface area and a 125,000 times larger volume compared to the mouse.

As it can be seen with these examples, while the radius of the sphere increases, its surface area does, too, but at a slower ratio compared to the volume ? in other terms, it gets scaled.

Based on this model, since the surface area is scaled (enlarged) with the square of the radius, and the volume with the cube of the radius, it can be estimated that the surface area is scaled with 2/3 the power of the volume.

The interesting point that all these rough calculations take us to is that the surface-area width of the living things is adjusted in a way to permit the release of energy they generate into their surroundings in a healthy pattern. If a hamster generated more heat than the amount corresponding to four times its surface area, this would lead to the hamster overheating.

In a similar way, if you elevated the heat in a hippopotamus, which generates 125,000 times more heat than a mouse does, by eight, the hippopotamus would suffer from heat exhaustion. This is because the surface area of a hippopotamus is only 2500 times bigger than a mouse. This is called the ?surface hypothesis,? and until it was discovered that it does not correlate well with the experimental data, scientists carried out investigations based on this model for nearly 50 years.

Around 1930, Swiss animal scientist Max Kleiber performed a series of studies involving the metabolic speed of various animals. The data he collected showed that the metabolic speed is scaled to ? the power of body mass, or Metabolic speed = body mass3/4.? This is called the power law in science. Instead of the 2/3 power in the first model, the correlation of 3/4 power with the experiments demonstrated that animals, especially large ones, have higher metabolic speeds than the first model predicted.

In summary, the establishment and maintenance of this equilibrium requires knowledge beyond geometric calculations, and makes it impossible to explain via random occurrences.?

In Figure 2, the scaling of different animals in regard to their body mass is charted. The horizontal axis shows the body mass in kilograms, whereas the vertical axis marks the speed of their average basal metabolism in watts. The symbols displayed as dots are real values measured from different animals and the fact that these dots align almost on a line show the correlation of the metabolic speeds of organisms with 3/4 the power of their body masses. This points to an extraordinary order in the universe, one that has been created with perfect harmony built into it. ?

One feature of the ?power law? is that when the two axes are drawn logarithmically, the relation between the two physical magnitudes appears as a line. Here, a similar situation is present and this power law is called the ?Kleiber Law.? This law successfully provides the metabolic speeds of mammals, birds, fish, plants, and even single celled organisms.

There are also other scaling relations pertaining to these that have confounded biologists for a long time. For example, the bigger a mammal is, the longer its life span is. There are examples, like humans, who do not fit into this general principle. However this is applicable for many mammals. The life of a mouse lasts two years, typically, whereas the life of a pig is around 10 years ? and elephants live for 50 years. If you chart the average life span of many different species across their body masses, the value of the power law is seen as ?. In other terms, for mammals, the average life span is scaled to ? of the body mass (directly proportioned).

As another example of proportion and scale, if you draw a graphic displaying how the average heart beat speed changes against the body mass of different species, you will once again find the scale of the power law to be ?. This means that the larger the body mass of a mammal, the lower its heart beat is.

Biologists are trying to solve the mysteries among the relations of many power laws like this one. There is no doubt among scientists regarding the fact that these power laws manifest certain common features in living things as an important sign pointing to the presence of very significant common features for all organisms.

Figure 2. Metabolic speeds of different animals according to their body masses. Taken from Complexity: A Guided Tour by Melanie Mitchell, Oxford University Press.

The creation of living things according to a power law, which is a relation between their metabolic speeds and body sizes, is a wisdom that requires thanksgiving. To safely release their generated energy, the metabolic speeds of living things must be scaled to ? the power of their body mass. A lower value would cause a higher body heat, and a higher value would lead to very low body heat. In both situations it would not be possible for organisms to sustain their lives in the physical world. Our bodies are perfectly scaled for us to survive.

Note

Experimental values were obtained from the book of – K. Schmidt-Nielsen, Scaling: Why is animal size so important?, Cambridge University Press, 1984.

Reference

• Complexity – A Guided Tour, Melanie Mitchell, Oxford University Press, 2009.

Each creation is a work of art. All animals and plants, as well as every human being, are unique and priceless. And those who appreciate their value are like antique dealers as in the passage above. I recently had the chance to listen to such an “antique dealer,” Joanna Aizenberg of Bell Laboratories/Lucent Technologies, and witnessing the appreciation of the valuables she presented to us helped me better understand Said Nursi. Both the valuable object she was talking about and her appreciation of it were equally inspiring for me, and this is the reason why I have decided to share this story with you. Without any further ado, here is the story of a sponge species called the Venus’ Flower Basket and its “eternally” incarcerated residents: a pair of shrimp. Now, you must find what is hiding behind all this; after all, it is the eyes that look but the heart that perceives.

Venus’ Flower Baskets (Figure 1a) are vase-like sponges that grow upright on the sea floor of the Pacific Ocean, mostly around Japan. They have a very sophisticated mesh structure which caused medieval Europeans to assume they were glasswork made in China. In Japan they are called Kairou-Douketsu (together for eternity) and given as wedding gifts, since they generally house a pair of mated shrimp which are trapped in their cavity. As you have probably already understood, our story is about the engineering secrets of these sponges and their relationship with their guests.

The design

The skeleton of the Venus’ Flower Basket is made of silica, which is a very brittle material (remember the glass windows that you broke with your football when you were a kid; they were made with silica). How can these amazing creatures withstand the pressure and the currents present at the sea floor or the disturbance caused by two shrimp? The secret lies in the hierarchical construction of their cylindrical cage-like structure. As can be seen in Figure 1b, their skeleton is made up of beams that run perpendicular and parallel to the axis of the sponge, which forms a rectangular grid. This grid is further supported by beams that run diagonally in both directions. Finally, this whole structure is reinforced by ridges that spiral around. But these are just the macroscopic hierarchical levels of the construction. Now let’s start from the very first level of this hierarchy and try to understand how each level adds to the stability of the sponge.

The basic building block of the Venus’ Flower Baskets is a fiber composed of silica nano-spheres (Figures 1i and 2a) that grows around an organic filament (the black dots at the center of the circles in Figure 1f). Though this fiber is not very stress tolerant, due to the size of the spheres from which it is made, in the next level of hierarchy it is toughened by alternating organic and silica sheets that form a concentric lamellar (fine, alternating layers of different materials) fiber structure. The thickness of each layer in the fiber decreases from 1.5 (: 1/1000 mm) at the center to 0.2 towards the periphery (Figures 1f, 1g and 2b). Hence any crack that is initiated at the periphery is halted at the organic interlayers and while the thinner outer layers lessen the depth of crack propagation, the thicker inner layers enhance mechanical rigidity (in addition to their mechanical stability, these silica fibers are endowed with optical properties which are superior to man-made fibers, which will be discussed later on in the article).

Figure 1. Structural analysis of the mineralized skeletal system of Euplectella sp. (a) Photograph of the entire skeleton, showing cylindrical glass cage. Scale bar, 1 cm. (b) Fragment of the cage structure showing the square-grid lattice of vertical and horizontal struts with diagonal elements arranged in a chessboard manner. Orthogonal ridges on the cylinder surface are indicated by arrows. Scale bar, 5 mm. (c) Scanning electron micrograph (SEM) showing that each strut (enclosed by a bracket) is composed of bundled multiple spicules (the arrow indicates the long axis of the skeletal lattice). Scale bar, 100 mm. (d) SEM of a fractured and partially HF-etched (25) single beam revealing its ceramic fiber-composite structure. Scale bar, 20 mm. (e) SEM of the HF-etched (25) junction area showing that the lattice is cemented with laminated silica layers. Scale bar, 25 mm. (f) Contrast-enhanced SEM image of a cross section through one of the spicular struts, revealing that they are composed of a wide range of different-sized spicules surrounded by a laminated silica matrix. Scale bar, 10 mm. (g) SEM of a cross section through a typical spicule in a strut, showing its characteristic laminated architecture. Scale bar, 5 mm. (h) SEM of a fractured spicule, revealing an organic interlayer. Scale bar, 1 mm. (i) Bleaching of biosilica surface revealing its consolidated nanoparticulate nature (25). Scale bar, 500 nm. Figure and captions from ref. 2.

Fibers of different diameters reinforced this way are then bundled loosely in a silica matrix (Figure 1d and 1f). The different diameter of the fibers in the bundle and the weak lateral bonding between them are essential for increasing the strength of the bundle against crack propagation. At the next level of hierarchy, these bundles are used as building blocks of the cylindrical cage of the sponge, being arranged horizontally and vertically into a square grid. This grid in turn is reinforced by diagonal bundles that run in both directions along every second square lattice. The minimum number of pin-jointed struts (i.e. ones that are free to rotate at the joints) per node needed in order to form a rigid two-dimensional grid has been shown to be six; this is the number present in the skeleton of the Venus’ Flower Basket. In fact, if the diagonal bundles were to run along every square lattice, the number of struts per node would be 8, which would be redundant for the stability in the skeleton.

At the early stages of the growth of the Venus’ Flower Basket the struts are not connected at the nodes. However as the sponge gets older the struts are joined by a silica cement which itself also has a lamellar structure (Figure 1e). Hence, while the younger sponges are flexible, the older ones are stiff; this also has important implications for the symbiotic relation that the sponge has with its guests, the shrimp. (This issue will be discussed in detail when the lifecycle of the shrimp is examined.) While the resulting grid is stable in two dimensions, in three dimensions it may still suffer from exterior effects, such as ovalization. This problem however is solved at the next level of hierarchy by the helical ridges that surround the grid (Figure 1b). The absence of the ridges at the base of the skeleton of the sponge where the cage diameter is small, and their increased density further up the cage where the diameter is much greater is proposed as evidence supporting this argument. Finally, this whole cage structure must be anchored to the sea floor in a way that will withstand the bending stresses caused by the currents. This is managed through the use of the fibers that have been discussed earlier; they are used as connectors between the base of the sponge that is anchored to the sea floor and the vertical struts of the skeleton, resulting in a flexible connection that enables the cage to swing freely in the currents (Figure 1a).

As a conclusion, it can be said that “The resultant structure might be regarded as a textbook sample in mechanical engineering, because the seven hierarchical levels in the sponge skeleton represent major fundamental construction strategies, such as laminated structures, fiber-reinforced composites, bundled beams, and diagonally reinforced square-grid cells to name a few.”

Now let’s concentrate more on the fibers (or spicules) that anchor the cage to the sea floor. These anchorage spicules (a term used for describing the skeletal structures of sponges which comes from the Latin word speculum, meaning the head of a spear or arrow)* are 5-15 cm in length and 40-70 um in diameter. In the above discussion we have briefly discussed the cross-sectional structure of these fibers that gives them their flexible, but resistant nature. Here we will focus on the optical properties of these spicules. But before doing so, let’s briefly explain how optical fibers work.

Optical fibers are silica fibers of a 5 to 80 um diameter that are coated with a cladding layer; light waves can travel in these for long distances by constantly bouncing off the cladding. The reason for this is the refractive index difference between the silica core and the cladding layer. Refractive index (n) is a measure of the ability of a medium to change the phase velocity of light and cause the light waves to bend while leaving one medium and entering another (refraction); in the case of fiber optics, leaving the core and entering the cladding. However, if the refractive index of the second medium is lower than that of the initial one, the incident light waves that have an incidence angle higher than a critical value or critical angle can be reflected back to the first medium and this is what happens in fiber optics (See red ray in figure 2). If the core diameter is small (5-10 um), light rays can propagate only through a single path in the fiber (which runs parallel to the fiber axis), hence these type of fibers are called single-mode fibers (See Figure 2a). If the core diameter is larger however, (60-80 um) several paths are accessible, and more paths will have incidence angles that are greater than the critical angle, hence they are called multi-mode (See Figure 2b).

Now with this information in mind, let’s have a look at the characteristics of the anchoring spicules of the Venus’ Flower Basket. First of all, as mentioned in the previous discussion, the lamellar structure of these spicules prevents crack propagation, which is the main failure mode of commercial silica fibers. This lamellar structure, however, also determines the dependence of the optical behavior of the spicules on the environment in which they are embedded. For instance if the spicules are embedded in an epoxide medium with a refractive index of 1.57, the spicule as a whole would not be able to act as an optical fiber, due to the smaller refractive index of the cladding. However, since the core region of the spicules has a slightly higher refractive index than that of the cladding, the core acts as a single mode fiber in such an environment (see Figure 2a). In sea water-the spicules’ native environment-which has a refractive index of 1.33, the whole spicule acts as a multimode fiber, since the refractive index difference between the core and the cladding is much smaller than that between the cladding and the surrounding sea water.

Another advantage of these spicules over man-made fibers is their formation/production parameters, which are ambient temperature and pressure; these enable the introduction of impurities into the silica. Though at first it may not sound as if impurities are a positive characteristic, these impurities are very important for increasing the refractive index of silica and act as dopants (impurity elements added to a semiconductor lattices in low concentrations in order to alter the optical/electrical properties of the semiconductor). The core section of the spicules, for instance, shows increased sodium concentration, which is the cause of the higher refractive index of this section. Such dopant introduction in the silica during the fabrication process, however, is not possible in the case of man-made fibers, due to the very high processing temperatures.

In addition to this, the spicules have crown-like caps at their base and thorn-like structures throughout their middle section. While the crown-like termini most probably are used to anchor the sponge to the ocean floor, it has also been shown that the waveguiding efficiency of the spicules increases when the illumination comes through the end that has the crown-like structure. Hence, it has been proposed that this structure may be acting as a light harvesting lens. The thorn-like structures, on the other hand, share the lamellar construction of the spicule body, and the light guided through the body branches out to these spines and emerges at the tip. Since sea water comes into contact with the tip at an almost perpendicular angle to the guided light, the coupling is pretty efficient. Hence the combination of crown-like ends and thorn-like structures forms optical networks that collect and distribute light. However, at the depths inhabited by the Venus’ Flower Baskets there is no accessible light source. If one accepts the fact that there is no waste in nature-whether one believes in “creation” or “evolution”-the existence of such an advanced network-like structure as a part of a sponge-the most primitive animal-is at least thought-provoking. In the case of sponges that dwell in shallower waters with similar spicules, it has been postulated that such spicules gather and provide sunlight for the sponge’s endosymbiotic algae. However, at the depths at which the Venus’ Flower Baskets live, direct sunlight is not available. However it has been suggested that if light sources, such as bioluminescent microorganisms (bioluminescence is the production and emission of light by a living organism as the result of a chemical reaction during which chemical energy is converted to light energy) or chemiluminescence (emission of light as the result of a chemical reaction) exist, their light may be efficiently distributed by the sponge and act as an attractant for juvenile shrimp that are searching for a host. But for now these suggestions are just speculation and merit further investigation.

Before concluding this section, we should also note that, as a natural outcome of their construction/composition, these spicules do not have as great a transparency as their industrial counterparts and light cannot be transferred over long distances with them. However, it seems this is not a problem for the Venus’ Flower Basket as, apparently, they just need fibers of 5-15 cm to survive and it is the scientists who need to figure out a way to incorporate the traits of the Venus’ Flower Basket into industrial fibers.

The love

As mentioned in the introduction, the Venus Flower Basket hosts a pair of mated shrimp. These belong to the family of Spongicolidae, the Spongicala japonica. These shrimp, which can be as “big” as 9 mm in length, spend most of their lives in their host sponge. Though studies about them are limited, it is believed that before permanently being entrapped in their host, the shrimp have two free- living periods. The first one is just after hatching when they are small enough to exit through the mesh of the sponge. During this period they exit and re-enter their cages and live in a group with their parents and other juveniles. Studies suggest that the females generally stay with their parents until sexual maturity, whereas the males tend to leave their original host and live a solitary life until they reach a length of about 4 mm.

The second free-living period comes at the time of sexual maturity, when it is believed that the male and female mate outside and then invade a host, or the female searches for a host that is already occupied by a solitary male. During this stage, the shrimp have a body length of 3.5 to 6.5 mm which is bigger than the mesh size of the host sponges. Though this seems puzzling, it is thought that the mated shrimp enter the sponge in its flexible stage-when it may be easier to penetrate through the mesh-and get trapped there “forever” as the sponge grows older and stiffer. In fact this theory is supported by the finding that several flexible sponge specimens host solitary and young mated shrimp, whereas in the stiff specimens only very few solitary and young mated shrimp have been observed.

References

1. “Biological glass fibers: Correlation between optical and structural properties.” J. Aizenberg, V. C. Sundar, A. D. Yablon, J. C. Weaver, and G. Chen, Proc. Nat. Ac. Sci. 101 3358 (2004).

2. “Skeleton of Euplectella sp.: Structural hierarchy from the nanoscale to the macroscale.” J. Aizenberg, J. C. Weaver, M. S. Thanawala, V. C. Sundar, D. E. Morse, P. Fratzl, Science, 309 275 (2005).

3. “Fibre-optical features of a glass sponge – Some superior technological secrets have come to light from a deep-sea organism.” V. C. Sundar, A. D. Yablon, J. L. Grazul, M. Ilan, J. Aizenberg, Nature 424 899 (2003).

4. “Skeletal growth of the deep-sea hexactinellid sponge Euplectella oweni, and host election by the symbiotic shrimp Spongicola japonica” (Crustacea: Decapoda: Spongicolidae). T. Saito, I. Uchida and M. Takeda J. Zool., Lond. 258 521 (2002)

5. “Pair formation in Spongicola japonica (Crustacea: Stenopodidea: Spongicolidae), a shrimp associated with deep-sea hexactinellid sponges.” T. Saito, I. Uchida and M. Takeda J. Mar. Biol. Ass. U.K. 81 789 (2001).

Note

*. Also defined as, one of the minute calcareous or siliceous bodies that support the tissue of various invertebrates (Merriam-Webster’s English dictionary)

In the 21st century, we are plunging forward into a new era of technological power — one that offers enormous promise and danger.

What is nanotechnology?

In its most basic form, nanotechnology refers to the manipulation of materials at the atomic or molecular level. The name derives from the nanometer, a scientific measurement unit representing a billionth of a meter, three to four atoms wide. Scientists are learning how to connect atoms and molecules together to create nano-scale mechanisms that create switches or transistors, or even small machines that can perform complex tasks.

To use an oft-quoted comparison, a human hair is between 100,000 and 200,000 nanometers thick, while a typical virus can be just 100 nanometers wide. Atoms are typically between one-tenth and one-half of a nanometer wide. Due to the difficulties involved in working at this scale, manipulation of items as “large” as 100 nanometers is generally included in the concept of nanotechnology.

Nanotechnology enables scientists to create new materials atom by atom. With increasingly more powerful microscopes, scientists can see molecules that are mere nanometers (billionths of a meter) in size. To clarify this size, a pinhead is one million nanometers across. The field intertwines nearly all fields of science.

Most nanotechnology discussions deal with the futuristic concept of nanomachines or nanorobots: microscopic devices that carry out tasks at the atomic or subatomic level. Nanotechnology, also called molecular manufacturing, is “a branch of engineering that deals with the design and manufacture of extremely small electronic circuits and mechanical devices built at the molecular level of matter.” The goal of nanotechnology is to manipulate materials at the atomic level to build the smallest possible electromechanical devices, given the physical limitations of matter. Many of the mechanical systems that we know how to build will be transferred to the molecular level as some atomic analogy.

A typical vision of the twenty-first century: “Nanotechnologists will be building our cars one molecule at a time, invading our bloodstream to declog our arteries, and replicating themselves thousands of times over.”

Nanorobots (1)

A nanorobot is a computer-controlled robotic device constructed of nanometer-scale components to molecular precision, usually microscopic in size (often abbreviated as nanobot). This reminds one of the 1966 film Fantastic Voyage, in which a team of scientists (including Raquel Welch) are miniaturized, placed in a tiny submarine, and injected into a sick man’s bloodstream. Nanotechnology invariably involves work on a much smaller scale than the average blood cell.

Producing commercially viable nanomachines will be more challenging, since atomic manipulation, while not theoretically contrary to the laws of physics, is still extremely slow and costly. The most widely discussed long-term solution is to make the nanomachines self-replicating. Control mechanisms for such systems, mainly how a machine “knows” to copy itself and when to stop doing so, are still in their very early stages. Once again, theory is far ahead of practical reality.

Many of nanotechnology’s more recent practical applications have been in the area of material research. However, scientists believe that transistors eventually could be built in this way, paving the way for computational technologies that do not depend on silicon and that can pack even more circuitry into microscopic spaces.

Nanoshells (2)

Nanoshells, defined as tiny particles that can manipulate light, can be used to transform medical procedures, ranging from cancer therapy to medical testing and drug delivery. They are ideal for biotechnology applications because they are biocompatible, can be altered and modified, and absorb light easily in the near-infrared region, where human tissue is most transparent.

Nanoshells can be tagged and delivered specifically to tumor cells, thereby leaving healthy cells undamaged. In addition, they can reduce the amount of time needed to conduct medical tests from several days to a matter of seconds. When incorporated into temperature-sensitive polymers, nanoshells can be triggered to release a chemical using infrared light, thus enabling a patient to control the release of medicine that requires periodic dispensing.

A new bandage (3)

A new bandage that imitates natural healing process is used for injuries ranging from minor cuts to gunshot wounds. The bandage, a flannel-like material, stops bleeding immediately and eventually is absorbed by the body. This new material is developed by spinning a compound naturally found in the blood into a bandage that can minimize blood loss and be absorbed by the body, according to an article in the 12 Feb. 2003 issue of Nano Letters, a journal of the American Chemical Society. “We’ve taken an old technique — electrospinning — and applied it to natural fibers,” says Gary Bowlin, associate professor of biomedical engineering at Virginia Commonwealth University.

When a person bleeds from a cut or a wound, a blood clot forms and netting made of a substance called fibrin develops over the clot. According to researchers, fibrinogen, the compound in blood that comprises the “natural” bandage, is a fibrin precursor that can come from human, bovine, or genetically engineered bacterial sources. The goal is to pack the bandage like gauze so that it can be used to treat trauma patients, according to Bowlin.

Science fiction into reality (4)

Imagine a world in which cars can be assembled molecule-by-molecule, garbage can be disassembled and turned into beef steaks, and people can be operated on and healed by cell-sized robots. Sounds like science fiction? Well, with current semiconductor chip manufacturing encroaching upon the nanometer scale and the ability to move individual atoms at the IBM Almaden laboratory, we are fast approaching the technological ability to fabricate productive machines and devices that can manipulate objects at the atomic level. With this ability, we will be able to develop molecular-sized computers and robots that will give us unprecedented control over matter and the ability to shape the physical world as we see fit.

Nanofabrication techniques with applications in fiber optics, biotechnology, microelectromechanical systems (MEMS), and “tiny mechanical devices such as sensors, valves, gears, mirrors, and actuators embedded in semiconductor chips,” are of particular interest, as they are but a mere step away from the molecular machines envisioned by nanotechnology. MEMS are used in automobile airbag systems as accelerometers to detect collisions, and will become an increasing part of our everyday technology. In 1986, K. Eric Drexler, a researcher at MIT, foresaw the advent of molecular machines. In his Engines of Creation, he outlined the possibilities and consequences of this emerging field, which he called nanotechnology. Drexler has written numerous books on the subject, such as Unbounding the Future, and has founded the Foresight Institute, a nonprofit organization dedicated to the responsible development of nanotechnology. Today, nanotechnology research and development is widespread in numerous universities. The U.S. government has created an organization, the National Nanotechnology Initiative (NNI), to monitor and guide research and development in this field.

Potential benefits

It does not take much of a leap of imagination disassemblers dismantling garbage to be recycled at the molecular level, and then giving it to assemblers who will use it to build atomically perfect engines. Stretching this vision a bit, you can imagine a Star Trek type replicator that could reassemble matter in the form of a juicy steak, given the correct blueprints and organization of these nanomachines.

A laboratory-scale “in vivo nanoscope” could be capable of providing atomic resolution, real-time movies of happenings inside living cells in intact living animals. This nanoscope, a hybrid of conventional technology and early (pre-assembler) nanotechnology, is an enormous leap in the ability of biologists to understand the workings of cells and develop medical therapies.

Some of the more prominent benefits of nanotechnology would be precision manufacturing, material reuse, and miniaturization. Medical applications are pharmaceutical creation, disease treatment, and nanomachine-assisted surgery. Environmental applications lie in toxin cleanup, recycling, and resource consumption reduction.

Nanomedicine deals with the comprehensive monitoring, control, construction, repair, defense, and improvement of all human biological systems by working at the molecular level with engineered nanodevices and nanostructures; the science and technology of diagnosing, treating, and preventing disease and traumatic injury, as well as relieving pain and preserving and improving human health through the use of molecular tools and molecular knowledge of the human body; and the use of molecular machine systems to address medical problems and using molecular knowledge to maintain and improve human health at the molecular scale. Cosmetic nanosurgery carried out with simple nanomachines (no on-board computers, for example) could change hair color, cause hair to grow or not to grow in specific locations, keep teeth clean and skin smooth, and so on, all far more effectively than current treatments.

Looking somewhat further in the future at more radical modifications of the human body through nanotechnology, Edward Reifman describes dentistry with assembly-fabricated teeth, and even with the teeth and jaws being made of diamonds. “In the long term, we hope to be able to build small nanorobots which can search out and destroy cancerous tumors when they comprise just one or two cells” or “small drilling machines which dissolve clots.”

Viruses, which are natural nanomachines, could be fought more effectively, as the body’s own immune system has some handicaps: it tends to forget the shape of its enemies, cannot always successfully identify malignant cells, and suffers from a certain delay until the immune reaction is fully developed. Therefore, nanomachines could support the immune system. Nanomachines could rout bacteria, excise tumors, reconstruct damaged tissue, and even make a huge contribution to treating the process of aging.

Along with the obvious manufacturing benefits, there are many potential medical and environmental benefits. With nanomachines, we could better design and synthesize pharmaceuticals, directly treat such diseased cells as cancer, better monitor a patient’s life signs, and make microscopic repairs in hard-to-operate-on bodily areas. With regard to the environment, we could use nanomachines to clean up toxins or oil spills, recycle garbage, and eliminate landfills, thus reducing our natural resource consumption.

Potential dangers

The downside to these benefits is the possibility of using assemblers and disassemblers to create weapons, to be used as weapons themselves, or the possibility that they may run wild and wreak havoc. Other less invasive but equally perilous uses would be in electronic surveillance.

However, with nanotechnology, armies could develop disassemblers to attack physical structures or biological organisms at the molecular level. A similar hazard would be if general-purpose disassemblers escaped into the environment and started disassembling every molecule they encountered, the so-called “gray goo scenario.” Furthermore, if nanomachines were created to be self-replicating and, for some reason, had a problem with their limiting mechanism, they would multiply endlessly, like viruses.

Even without considering such extreme disaster scenarios, we can find plenty of potentially harmful uses for nanotechnology, such as the erosion of our freedom and privacy. For example, people could use molecular-sized microphones, cameras, and homing beacons to monitor and track others.

Ethical issues and analysis

Given the awesome potential dangers inherent in nanotechnology, we must analyze its potential consequences. Nanotechnology may never become as powerful and prolific as envisioned by its evangelists, but as with any potential near-horizon technology, we should formulate solutions to potential ethical issues before the technology is irreversibly adopted. We must examine the ethics of developing nanotechnology and create policies designed to assist its development while eliminating, or at least minimizing, its damaging effects.

Nanosensors(5)

A nanosensor is defined as a chemical or physical sensor constructed by using nanoscale components, usually microscopic or submicroscopic in size.

Nanotechnology brings science fiction into everyday life6 Nanotechnology’s more immediate future lies in its application in such sensors as electronic “noses” that can detect, for example, the presence of individual protein molecules in a blood sample. This involves a fingernail-sized chip with thousands of sensors, each set to detect a specific substance. It might even be possible to make these noses so small that they could fit on a needle. Then, there would be no need for a blood test, for a finger prick would be sufficient to allow a full blood analysis.

Nanosensors also will be of great value in producing new medicines, for they can effectively find active substances. So far, it has been possible to build this type of sensor one by one; the difficulty lies in integrating perhaps 100,000 of them on one chip.

Aging can be delayed by repairing human cells one by one. Unlimited computer power can be obtained by improved microchip performance. Global warming can be reduced by cleaning greenhouse gases out of the atmosphere with nanoparticles, and pesticides could kill insects without harmful byproducts. Creating artificial muscles and sensors, as well as nanocoating for metal, could increase power plant efficiency and potentially save millions of dollars a year for electricity generators. For example, we now have self-washing windows that repel dirt, thanks to their nanostructured surface.

Nanofluids (7)

On the medical front, researchers at Virginia Polytechnic Institute are developing magnetic nanofluids. They posit that magnetic particles attached to medicines, like those used in chemotherapy, can be concentrated on one part of the body by using external magnets on patients. 

Always clean clothing (8,9)

Imagine textiles that cannot be stained or wrinkled, that always maintain the look and feel of fabrics made from natural fibers. Imagine materials that are 100 times stronger than steel, but weigh only one-sixth as much. Nanofibers could be used in astronauts’ suits, moving with them as they work to give them greater flexibility in space, or to allow the disabled greater mobility by acting as extra muscles.

Imagine batteries that take up less than one cubic millimeter, but supply a medical implant with power. Imagine sensors, smaller than a pinpoint, that detect anything in extremely low concentrations, from specific antibodies to toxic chemicals.

A big splash of coffee leaves an unmistakable stain on an ordinary pair of trousers; on a pair of nanotextile trousers, it can be brushed off without leaving a trace. A titanium frying pan and the laser in a fairly modern CD player are both based on nanotechnology. By using nanotechnology, wall paint could automatically sterilize an operating theatre, filters could be used in water purifiers to automatically kill undesirable bacteria, and roofing tiles that convert solar light into household electricity could give way to reinforced self-repairing houses immune to all natural disasters “short of a large incoming meteor.(10)

Hence nano-technology is and will continue to become part of our everyday lives … sometimes without us even noticing.

Michael Crichton (11)

Crichton says “These organisms [self-reproducing tiny computers] will be created by nanotechnology, perhaps the most radical technology in human history: the quest to build man-made machines of extremely small size, on the order of 100 nanometers, or 100/billionths of a meter. Such machines would be 1,000 times smaller than the diameter of a human hair. Experts predict that these tiny machines will provide everything from miniaturized computer components to new medical treatments to new military weapons. In the 21st century, they will change our world totally.

“The potential benefits are spectacular: Tiny robots may crawl through your arteries, cutting away atherosclerotic plaque; powerful drugs will be delivered to individual cancer cells, leaving other cells undamaged; teeth will be self-repairing. Cosmetically, you will change your hair color with an injection of nanomachines that circulate through the body, moving melanocytes in hair follicles. Other nanomachines will lighten or darken skin color at will, removing blemishes, birthmarks and liver spots in the process; still others could cleanse the mouth and eliminate bad breath. Nonsurgical nanoprocesses could even perform liposuction and body reshaping. They will also repair knees and spines.

Living spaces will be transformed with self-cleaning dishes and carpets and permanently clean bathrooms. Windows will lighten or darken at will; programmable paint will change color. You can walk through the walls of your house, since they are composed of particle clouds. Your personal computer and your watch will be painted on your arm. Temperature-sensitive clothing will loosen when it gets hot, insulate when it gets cold.”

In the future, roving nanomachines will convert trash dumps to energy, solar nanomachines will be coated on the houses to generate electricity, and flexible nanomachines will provide earthquake protection. It may even be possible to move a house across the lawn on the backs of millions of nanomachines.

In 2003, nanotechnology is still very much in its infancy. However, such major corporations as IBM, Fujitsu, and Intel are funding this research. U.S. government investment has gone from virtually nothing only a few years ago to well over $600,000,000 per year in 2003.

At present, nonotechniques are being used to make sunscreens, stain-resistant fabrics, and composite materials for cars; soon, they will be used to make extremely small computers and storage devices. Pittsburgh based PPG Industries, Inc. is making self-cleaning window glass; the Westaim Corporation of Toronto is making nanocrystal wound dressings with antibiotic and anti-inflammatory properties. Currently, nanotechnology is principally a material technology.

Most experts predict that self-reproducing machines are only a decade away. Man-made, self-reproducing entities already have been released into the environment. The first of these, of course, were computer viruses. The first viruses were created as a game (“core wars”), a 1960s battle between mainframe programmers, each releasing a program into the other’s mainframe computer. Originally limited to specialists, hackers soon joined in. The growth of computer networking made rapid worldwide transmission possible. Computer viruses, worms on the Internet, have become an international threat to information and global business.

Scientists are witnessing some of the problems of self-replicating biotechnology agents. For example, a recent report indicates that modified maize genes are appearing in native maize in Mexico, despite laws against it and efforts to prevent it. This is only the start of probably a long journey to control this new technology. Laws have been passed to put hackers in jail; delinquent biotechnologists will soon join them. We need international controls to deal with self-reproducing technologies right now, whereas now there are essentially none.

Footnotes

(1) www.zdnet.com.au/newstech/enterprise/story/0,2000048640,20267134-2,00.htm

(2)www.rice.edu/projects/reno/Newsrel/2001/20010402_nanotechnology.shtml.

(3) www.smalltimes.com/document_display.cfm?document_id=5481.

(4) http://cseserv.engr.scu.edu/StudentWebPages/AChen/ResearchPaper.htm.

(5) www.nansosensors.com.

(6) Nino Simic, “Nano into Everyday Life.” www.oresundit.com/composite(1610).htm.

(7) Ryan Randazzo, Reno Gazette-Journal, 15 June 2002.

(8) www.agg.com/Practice/Nanotechnology_main.html.

(9) www.oresundit.com/composite(1610).htm.

(10) www.foresight.org.

(11) Michael Crichton, “Could Tiny Machines Rule the World?” Parade Magazine, 24 November 2002, pgs. 6-8.

Some nanotechnology links:

• www.about.com/nanotechnology (A search engine that compiles various sources and articles).
• www.jmtour.com (Professor Jim Tour’s research home page).
• www-ece.rice.edu/~halas (Professor Naomi Halas’ research home page).
• www.nano.gov (The National Science and Technology Council’s site for nanoscale technology, including information on federal initiatives).