Nanotechnology involves the understanding and control of matter at the nanometer-scale. The so-called nanoscale deals with dimensions between approximately 1 and 100 nanometers.

A nanometer is an extremely small unit of length—a billionth (10^-9) of a meter. Just how small is a nanometer (nm)?

On the nanometer-scale, materials may exhibit unusual properties. When you change the size of a particle, it can change color, for example. That’s because in nanometer-scale particles, the arrangement of atoms reflects light differently. Gold can appear dark red or purple, while silver can appear yellowish or amber-colored.

Nanotechnology can increase the surface area of a material. This allows more atoms to interact with other materials. An increased surface area is one of the chief reasons nanometer-scale materials can be stronger, more durable, and more conductive than their larger-scale (called bulk) counterparts.

Nanotechnology is not microscopy. "Nanotechnology is not simply working at ever smaller dimensions," the U.S.-based National Nanotechnology Initiative says. "Rather, working at the nanoscale enables scientists to utilize the unique physical, chemical, mechanical, and optical properties of materials that naturally occur at that scale."

Scientists study these properties for a range of uses, from altering consumer products such as clothes to revolutionizing medicine and tackling environmental issues.

Classifying Nanomaterials

There are different types of nanomaterials, and different ways to classify them.

Natural nanomaterials, as the name suggests, are those that occur naturally in the world. These include particles that make up volcanic ash, smoke, and even some molecules in our bodies, such as the hemoglobin in our blood. The brilliant colors of a peacock’s feathers are the result of spacing between nanometer-scale structures on their surface.

Artificial nanomaterials are those that occur from objects or processes created by people. Examples include exhaust from fossil fuel burning engines and some forms of pollution. But while some of these just happen to be nanomaterials—vehicle exhaust, for instance, was not developed as one—scientists and engineers are working to create them for use in industries from manufacturing to medicine. These are called intentionally produced nanomaterials.

Fullerenes and Nanoparticles

One way to classify nanomaterials is between fullerenes and nanoparticles. This classification includes both naturally occurring and artificial nanomaterials.

Fullerenes

Fullerenes are allotropes of carbon. Allotropes are different molecular forms of the same element. The most familiar carbon allotropes are probably diamond and graphite, a type of coal.

Fullerenes are atom-thick sheets of another carbon allotrope, graphene, rolled into spheres or tubes.

The most familiar type of spherical fullerene is probably the buckminsterfullerene, nicknamed the buckyball. Buckyballs are nanometer-sized carbon molecules shaped like soccer balls—tightly bonded hexagons and pentagons.

Buckyballs are very stable—able to withstand extreme temperatures and pressure. For this reason, buckyballs are able to exist in extremely harsh environments, such as outer space. In fact, buckyballs are the largest molecules ever discovered in space, detected around planetary nebula in 2010.

Buckyballs’ cage-like structure seems to protect any atom or molecule trapped within it. Many researchers are experimenting with "impregnating" buckyballs with elements, such as helium. These impregnated buckyballs may make excellent chemical "tracers," meaning scientists could follow them as they wind through a system. For example, scientists could track water pollution kilometers away from where it entered a river, lake, or ocean.

Tubular fullerenes are called nanotubes. Thanks to the way carbon atoms bond to each other, carbon nanotubes are remarkably strong and flexible. Carbon nanotubes are harder than diamond and more flexible than rubber.

Carbon nanotubes hold great potential for science and technology. The U.S. space agency NASA, for example, is experimenting with carbon nanotubes to produce "blacker than black" coloration on satellites. This would reduce reflection, so data collected by the satellite are not "polluted" by light.

Nanoparticles

Nanoparticles can include carbon, like fullerenes, as well as nanometer-scale versions of many other elements, such as gold, silicon, and titanium. Quantum dots, a type of nanoparticle, are semiconductors made of different elements, including cadmium and sulfur. Quantum dots have unusual fluorescent capabilities. Scientists and engineers have experimented with using quantum dots in everything from photovoltaic cells (used for solar power) to fabric dye.

The properties of nanoparticles have been important in the study of nanomedicine. One promising development in nanomedicine is the use of gold nanoparticles to fight lymphoma, a type of cancer that attacks cholesterol cells. Researchers have developed a nanoparticle that looks like a cholesterol cell, but with gold at its core. When this nanoparticle attaches to a lymphoma cell, it prevents the lymphoma from "feeding" off actual cholesterol cells, starving it to death.

Intentionally Produced Nanomaterials

There are four main types of intentionally produced nanomaterials: carbon-based, metal-based, dendrimers, and nanocomposites.

Carbon-based nanomaterials

Carbon-based nanomaterials are intentionally produced fullerenes. These include carbon nanotubes and buckyballs.

Carbon nanotubes are often produced using a process called carbon assisted vapor deposition. (This is the process NASA uses to create its "blacker than black" satellite color.) In this process, scientists establish a substrate, or base material, where the nanotubes grow. Silicon is a common substrate. Then, a catalyst helps the chemical reaction that grows the nanotubes. Iron is a common catalyst. Finally, the process requires a heated gas, blown over the substrate and catalyst. The gas contains the carbon that grows into nanotubes.

Metal-based nanomaterials

Metal-based nanomaterials include gold nanoparticles and quantum dots.

Quantum dots are synthesized using different methods. In one method, small crystals of two different elements are formed under high temperatures. By controlling the temperature and other conditions, the size of the nanometer-scale crystals can be carefully controlled. The size is what determines the fluorescent color. These nanocrystals are quantum dots—tiny semiconductors—suspended in a solution.

Dendrimers

Dendrimers are complex nanoparticles built from linked, branched units. Each dendrimer has three sections: a core, an inner shell, and an outer shell. In addition, each dendrimer has branched ends. Each part of a dendrimer—its core, inner shell, outer shell, and branched ends—can be designed to perform a specific chemical function.

Dendrimers can be fabricated either from the core outward (divergent method) or from the outer shell inward (convergent method).

Like buckyballs and some other nanomaterials, dendrimers have strong, cage-like cavities in their structure. Scientists and researchers are experimenting with dendrimers as multifunctional drug-delivery methods. A single dendrimer, for example, may deliver a drug to a specific cell, and also trace that drug's impact on the surrounding tissue.

Nanocomposites

Nanocomposites combine nanomaterials with other nanomaterials, or with larger, bulk materials. There are three main types of nanocomposites: nanoceramic matrix composites (NCMCs), metal matrix composites (MMCs), and polymer matrix composites (PMCs).

NCMCs, sometimes called nanoclays, are often used to coat packing materials. They strengthen the material’s heat resistance and flame-retardant properties.

MMCs are stronger and lighter than bulk metals. MMCs may be used to reduce heat in computer "server farms" or build vehicles light enough to airlift.

Industrial plastics are often composed of PMCs. One promising area of nanomedical research is creating PMC "tissue scaffolding." Tissue scaffolds are nanostructures that provide a frame around which tissue, such as an organ or skin, can be grown. This could revolutionize the treatment of burn injuries and organ loss.

Nanomanufacturing 

Nanotech equipment

Scientists and engineers working at the nanometer-scale need special microscopes. The atomic force microscope (AFM) and the scanning tunneling microscope (STM) are essential in the study of nanotechnology. These powerful tools allow scientists and engineers to see and manipulate individual atoms.

AFMs use a very small probe—a cantilever with a tiny tip—to scan a nanostructure. The tip is only nanometers in diameter. As the tip is brought close to the sample being examined, the cantilever moves because of the atomic forces between the tip and the surface of the sample.

With STMs, an electronic signal is passed between the microscope’s tip—formed by one single atom—and the surface of the sample being scanned. The tip moves up and down to keep both the signal and the distance from the sample constant.

AFMs and STMs allow researchers to create an image of an individual atom or molecule that looks just like a topographic map. Using an AFM’s or STM’s sensitive tip, researchers can also pick up and move atoms and molecules like tiny building blocks.

Nanomanufacturing

There are two ways to build materials on the nanometer-scale: top-down or bottom-up.

Top-down nanomanufacturing involves carving bulk materials to create features with nanometer-scale dimensions. For decades, the process used to produce computer chips has been top-down. Producers work to increase the speed and efficiency of each "generation" of microchip. The manufacture of graphene-based (as opposed to silicon-based) microchips may revolutionize the industry.

Bottom-up nanomanufacturing builds products atom-by-atom or molecule-by-molecule. Experimenting with quantum dots and other nanomaterials, tech companies are starting to develop transistors and other electronic devices using individual molecules. These atom-thick transistors may mark the future development of the microchip industry.

History of Nanotechnology

U.S. physicist Richard Feynman is considered the father of nanotechnology. He introduced the ideas and concepts behind nanotech in a 1959 talk titled "There’s Plenty of Room at the Bottom." Feynman did not use the term "nanotechnology," but described a process in which scientists would be able to manipulate and control individual atoms and molecules.

Modern nanotechnology truly began in 1981, when the scanning tunneling microscope allowed scientists and engineers to see and manipulate individual atoms. IBM scientists Gerd Binnig and Heinrich Rohrer won the 1986 Nobel Prize in Physics for inventing the scanning tunneling microscope. The Binnig and Rohrer Nanotechnology Center in Zurich, Switzerland, continues to build on the work of these pioneering scientists by conducting research and developing new applications for nanotechnology.

The iconic example of the development of nanotechnology was an effort led by Don Eigler at IBM to spell out "IBM" using 35 individual atoms of xenon.

By the end of the 20th century, many companies and governments were investing in nanotechnology. Major nanotech discoveries, such as carbon nanotubes, were made throughout the 1990s. By the early 2000s, nanomaterials were being used in consumer products from sports equipment to digital cameras.

Modern nanotechnology may be quite new, but nanometer-scale materials have been used for centuries. 

As early as the 4th century, Roman artists had discovered that adding gold and silver to glass created a startling effect: The glass appeared slate green when lit from the outside, but glowed red when lit from within. Nanoparticles of gold and silver were suspended in the glass solution, coloring it. The most famous surviving example of this technique is a ceremonial vessel, the Lycurgus Cup.

Artists from China, western Asia, and Europe were also using nanoparticles of silver and copper, this time in pottery glazes. This gave a distinctive luster to ceramics such as tiles and bowls.

In 2006, modern microscopy revealed the technology of Damascus steel, a metal used in South Asia and the Middle East until the technique was lost in the 18th century—carbon nanotubes. Swords made with Damascus steel are legendary for their strength, durability, and ability to maintain a very sharp edge.

One of the most well-known examples of premodern use of nanomaterials is in European medieval stained-glass windows. Like the Romans before them, medieval artisans knew that by putting varying, small amounts of gold and silver in glass, they could produce bright reds and yellows.

Nanotech and the Environment

Many governments, scientists, and engineers are researching the potential of nanotechnology to bring affordable, high-tech, and energy-efficient products to millions of people around the world. Nanotechnology has improved the design of products such as light bulbs, paints, computer screens, and fuels.

Energy

Nanotechnology is helping inform the development of alternative energy sources, such as solar and wind power. Solar cells, for instance, turn sunlight into electric currents. Nanotechnology could change the way solar cells are used, making them more efficient and affordable.

Solar cells, also called photovoltaic cells, are usually assembled as a series of large, flat panels. These solar panels are big and bulky. They are also expensive and often difficult to install. Using nanotechnology, scientists and engineers have been able to experiment with print-like development processes, which reduces manufacturing costs. Some experimental solar panels have been made in flexible rolls rather than rigid panels. In the future, panels might even be "painted" with photovoltaic technology.

The bulky, heavy blades on wind turbines may also benefit from nanotech. An epoxy containing carbon nanotubes is being used to make turbine blades that are longer, stronger, and lighter. Other nanotech innovations may include a coating to reduce ice buildup.

Nanotech is already helping increase the energy-efficiency of products. One of the United Kingdom's biggest bus operators, for instance, has been using a nano-fuel additive for close to a decade. Engineers mix a tiny amount of the additive with diesel fuel, and the cerium-oxide nanoparticles help the fuel burn more cleanly and efficiently. Use of the additive has achieved a 5 percent annual reduction in fuel consumption and emissions.

Water

Access to clean water has become a problem in many parts of the world. Nanomaterials may be a tiny solution to this large problem.

Nanomaterials can strip water of toxic metals and organic molecules. For example, researchers have discovered that nanometer-scale specks of rust are magnetic, which can help remove dangerous chemicals from water. Other engineers are developing nanostructured filters that can remove viruses from water.

Researchers are also experimenting with using nanotechnology to safely, affordably, and efficiently turn saltwater into freshwater, a process called desalination. In one experiment, nano-sized electrodes are being used to reduce the cost and energy requirements of removing salts from water.

Oil Spill Clean-Up

Scientists and engineers are experimenting with nanotechnology to help isolate and remove oil spilled from offshore oil platforms and container ships.

One method uses nanoparticles' unique magnetic properties to help isolate oil. Oil itself is not magnetic, but when mixed with water-resistant iron nanoparticles, it can be magnetically separated from seawater. The nanoparticles can later be removed so the oil can be used.

Another method involves the use of a nanofabric "towel" woven from nanowires. These towels can absorb 20 times their weight in oil.

Nanotech and People

Hundreds of consumer products are already benefiting from nanotechnology. You may be wearing, eating, or breathing nanoparticles right now! 

Clothing

Scientists and engineers are using nanotechnology to enhance clothing. By coating fabrics with a thin layer of zinc oxide nanoparticles, for instance, manufacturers can create clothes that give better protection from ultraviolet (UV) radiation, like that from the sun. Some clothes have nanoparticles in the form of little hairs or whiskers that help repel water and other materials, making fabric more stain-resistant.

Some researchers are experimenting with nanotechnology for "personal climate control." Nanofiber jackets allow the wearer to control the jacket’s warmth using a small set of batteries.

Cosmetics

Many cosmetic products contain nanoparticles. Nanometer-scale materials in these products provide greater clarity, coverage, cleansing, or absorption. For instance, the nanoparticles used in sunscreen (titanium dioxide and zinc oxide) provide reliable, extensive protection from harmful UV radiation. These nanomaterials offer better light reflection for a longer time period.

Nanotechnology may also provide better "delivery systems" for cosmetic ingredients. Nanomaterials may be able to penetrate a skin’s cell membranes to augment the cell’s features, such as elasticity or moisture.

Athletics

Nanotech is revolutionizing the sports world. Nanometer-scale additives can make sporting equipment lightweight, stiff, and durable.

Carbon nanotubes, for example, are used to make bicycle frames and tennis rackets lighter, thinner, and more resilient. Nanotubes give golf clubs and hockey sticks a more powerful and accurate drive.

Carbon nanotubes embedded in epoxy coatings make kayaks faster and more stable in the water. A similar epoxy keeps tennis balls bouncy.

Food

The food industry is using nanomaterials in both the packaging and agricultural sectors. Clay nanocomposites provide an impenetrable barrier to gases such as oxygen or carbon dioxide in lightweight bottles, cartons, and packaging films. Silver nanoparticles, embedded in the plastic of storage containers, kill bacteria.

Engineers and chemists use nanotechnology to adapt the texture and flavor of foods. Nanomaterials’ greater surface area may improve the "spreadability" of foods such as mayonnaise, for instance. 

Nanotech engineers have isolated and studied the way our taste buds perceive flavor. By targeting individual cells on a taste bud, nanomaterials can enhance the sweetness or saltiness of a particular food. A chemical nicknamed "bitter blocker," for instance, can trick the tongue into not tasting the naturally bitter taste of many foods.

Electronics

Nanotechnology has revolutionized the realm of electronics. It provides faster and more portable systems that can manage and store larger and larger amounts of data.

Nanotech has improved display screens on electronic devices. This involves reducing power consumption while decreasing the weight and thickness of the screens.

Nanotechnology has allowed glass to be more consumer friendly. One glass uses nanomaterials to clean itself, for example. As ultraviolet light hits the glass, nanoparticles become energized and begin to break down and loosen organic molecules—dirt—on the glass. Rain cleanly washes the dirt away. Similar technology could be applied to touch-screen devices to resist sweat.

Nanomedicine

Nanotechnology can help medical tools and procedures be more personalized, portable, cheaper, safer, and easier to administer. Silver nanoparticles incorporated into bandages, for example, smother and kill harmful microbes. This can be especially useful in healing burns.

Nanotech is also furthering advances in disease treatments. Researchers are developing ways to use nanoparticles to deliver medications directly to specific cells. This is especially promising for the treatment of cancer, because chemotherapy and radiation treatments can damage healthy as well as diseased tissue.

Dendrimers, nanomaterials with multiple branches, may improve the speed and efficiency of drug delivery. Researchers have experimented with dendrimers that deliver drugs that slow the spread of cerebral palsy-like symptoms in rabbits, for example.

The list goes on. Fullerenes can be manipulated to have anti-inflammatory properties to slow or even stop allergic reactions. Nanomaterials may reduce bleeding and speed coagulation. Diagnostic testing and imaging can be improved by arranging nanoparticles to detect and attach themselves to specific proteins or diseased cells.

Grey Goo and Other Concerns

Unregulated pursuit of nanotechnology is controversial. In 1986, Eric Drexler wrote a book called Engines of Creation, which painted a vision of the future of nanotech, but also warned of the dangers. The book’s apocalyptic vision included self-replicating nanometer-scale robots that malfunctioned, duplicating themselves a trillion times over. These nano-bots rapidly consumed the entire world as they pulled carbon from the environment to replicate themselves.

Drexler’s vision is nicknamed the "grey goo" scenario. Many experts think concerns like "grey goo" are probably premature. Even so, many scientists and engineers continue to voice their concerns about nanotech’s future.

Nanopollution is the nickname given to the waste created by the manufacturing of nanomaterials. Some forms of nanopollution are toxic, and environmentalists are concerned about the bioaccumulation, or buildup, of these toxic nanomaterials in microbes, plants, and animals.

Nanotoxicology is the study of toxic nanoparticles, particularly their interaction with the human body. Nanotoxicology is an important research field, as nanomaterials can enter the body both intentionally and unintentionally. 

“Research is needed,” writes the U.S. Environmental Protection Agency, “to determine whether exposure to manufactured nanomaterials can lead to adverse effects to the heart, lungs, skin; alter reproductive performance; or contribute to cancer.”

Another concern about nanotechnology is the price. Nanotech is an expensive area of research, and largely confined to developed nations with strong infrastructure. Many social scientists are concerned that underdeveloped countries will fall further behind as they cannot afford to develop a nanotechnology industry.