Nanotechnology

Summary

Nanotechnology is dedicated to the study and manipulation of structures at the extremely small nano level. The technology focuses on how particles of a substance at a nanoscale behave differently than particles at a larger scale. Nanotechnology explores how those differences can benefit applications in a variety of fields. In medicine, nanomaterials can be used to deliver drugs to targeted areas of the body needing treatment. Environmental scientists can use nanoparticles to target and eliminate pollutants in the water and air. Microprocessors and consumer products also benefit from increased use of nanotechnology, as components and associated products become exponentially smaller.

Definition and Basic Principles

Nanotechnology is the science that deals with the study and manipulation of structures at the nano level. At the nano level, things are measured in nanometers (nm), or one billionth of a meter (10⁻⁹). Nanoparticles can be produced using various techniques known as top-down nanofabrication, which starts with a larger quantity of material and removes portions to create the nanoscale material. Another method is bottom-up nanofabrication, in which individual atoms or molecules are assembled to create nanoparticles. One area of research involves developing bottom-up self-assembly techniques that would allow nanoparticles to create themselves when the necessary materials are placed in contact with one another.

Nanotechnology is based on the discovery that materials behave differently at the nanoscale, less than 100 nm in size, than they do at slightly larger scales. For instance, gold is classified as an inert material because it neither corrodes nor tarnishes; however, at the nano level, gold will oxidize in carbon monoxide. It will also appear as colors other than the yellow for which it is known.

Nanotechnology is not simply about working with materials such as gold at the nanoscale. It also involves taking advantage of the differences at this scale to create markers and other new structures that are of use in a wide variety of medical and other applications.

Background and History

In 1931, German scientists Ernst Ruska and Max Knoll built the first transmission electron microscope (TEM). Capable of magnifying objects by a factor of up to one million, the TEM made it possible to see things at the molecular level. The TEM was used to study the proteins that make up the human body. It was also used to study metals. The TEM made it possible to view particles smaller than 200 nm by focusing a beam of electrons to pass through an object, rather than focusing light on an object, as is the case with traditional microscopes.

In 1959, the noted American theoretical physicist Richard Feynman brought nanoscale possibilities to the forefront with his talk "There's Plenty of Room at the Bottom," presented at the California Institute of Technology in 1959. In this talk, he asked the audience to consider what would happen if they could arrange individual atoms, and he included a discussion of the scaling issues that would arise. It is generally agreed that Feynman's reputation and influence brought increased attention to the possible uses of structures at the atomic level.

In the 1970s, scientists worked with nanoscale materials to create technology for space colonies. In 1974, Tokyo Science University professor Norio Taniguchi coined the term "nano-technology." As he defined it, nanotechnology would be a manufacturing process for materials built by atoms or molecules.

In the 1980s, the invention of the scanning tunneling microscope (STM) led to the discovery of fullerenes, or hollow carbon molecules, in 1986. The carbon nanotube was discovered a few years later. In 1986, K. Eric Drexler's seminal work on nanotechnology, Engines of Creation, was published. In this work, Drexler used the term "nanotechnology" to describe a process that is now understood to be molecular nanotechnology. Drexler's book explores the positive and negative consequences of being able to manipulate the structure of matter. Included in his book are ruminations on a time when all the works in the Library of Congress would fit on a sugar cube and when nanoscale robots and scrubbers could clear capillaries or whisk pollutants from the air. Debate continues as to whether Drexler's vision of a world with such nanotechnology is even attainable.

In 2000, the US National Nanotechnology Initiative was founded. Its mandate is to coordinate federal nanotechnology research and development. Great growth in the creation of improved products using nanoparticles has taken place since that time. The creation of smaller and smaller components—which reduces all aspects of manufacture, from the amount of materials needed to the cost of shipping the finished product—is driving the use of nanoscale materials in the manufacturing sector. Furthermore, the ability to target delivery of treatments to areas of the body needing those treatments is spurring research in the medical field.

The true promise of nanotechnology is not yet known, but this multidisciplinary science is widely viewed as one that will alter the landscape of fields from manufacturing to medicine.

How It Works

Basic Tools. Nanoscale materials can be created for specific purposes, but there exists also natural nanoscale material, like smoke from fire. To create nanoscale material and to be able to work with it requires specialized tools and technology. One essential piece of equipment is an electron microscope. Electron microscopy makes use of electrons, rather than light, to view objects. Because these microscopes have to get the electrons moving, and because they need several thousand volts of electricity, they are often quite large.

One type of electron microscope, the scanning electron microscope (SEM), requires a metallic sample. If the sample is not metallic, it is coated with gold. The SEM can give an accurate image with good resolution at sizes as small as a few nanometers.

For smaller objects or closer viewing, a TEM is more appropriate. With a TEM, the electrons pass through the object. To accomplish this, the sample has to be very thin, and preparing the sample is time consuming. The TEM also has greater power needs than the SEM, so SEM is used in most cases, and the TEM is reserved for times when a resolution of a few tenths of a nanometer is absolutely necessary.

The atomic force microscope (AFM) is a third type of electron microscope. Designed to give a clear image of the surface of a sample, this microscope uses a laser to scan across the surface. The result is an image that shows the surface of the object, making visible the object's "peaks and valleys."

Moving the actual atoms around is an important part of creating nanoscale materials for specific purposes. Another type of electron microscope, the scanning tunneling microscope (STM), images the surface of a material in the same way as the AFM. The tip of the probe, which is typically made up of a single atom, can also be used to pass an electrical current to the sample, which lessens the space between the probe and the sample. As the probe moves across the sample, the atoms nearest the charged atom move with it. In this way, individual atoms can be moved to a desired location in a process known as quantum mechanical tunneling.

Molecular assemblers and nanorobots are two other potential tools. The assemblers would use specialized tips to form bonds with materials that would make specific types of materials easier to move. Nanorobots might someday move through a person's blood stream or through the atmosphere, equipped with nanoscale processors and other materials that enable them to perform specific functions.

Bottom-Up Nanofabrication. Bottom-up nanofabrication is one approach to nanomanufacturing. This process builds a specific nanostructure or material by combining components of atomic and molecular scale. Creating a structure this way is time consuming, so scientists are working to create nanoscale materials that will spontaneously join to assemble a desired structure without physical manipulation.

Top-Down Nanofabrication. Top-down nanofabrication is a process in which a larger amount of material is used at the start. The desired nanomaterial is created by removing, or carving away, the material that is not needed. This is less time consuming than bottom-up nanofabrication, but it produces considerable waste.

Specialized Processes. To facilitate the manufacture of nanoscale materials, a number of specialized processes are used. These include nanoimprint lithography, in which nanoscale features are stamped or printed onto a surface; atomic layer epitaxy, in which a layer that is only one atom thick is deposited on a surface; and dip-pen lithography, in which the tip of an atomic force microscope writes on a surface after being dipped into a chemical.

Applications and Products

Smart Materials. Smart materials are materials that react in ways appropriate to the stimulus or situation they encounter. Combining smart materials with nanoscale materials would, for example, enable scientists to create drugs that would respond when encountering specific viruses or diseases. They could also be used to signal problems with other systems, such as nuclear power generators or pollution levels.

Sensors. The difference between a smart material and a sensor is that the smart material will generate a response to the situation encountered, while the sensor will generate an alarm or signal that there is something that requires attention. The capacity to incorporate sensors at a nanoscale greatly enhances the ability of engineers and manufacturers to create structures and products with a feedback loop that is not cumbersome. Nanoscale materials can easily be incorporated into the product.

Medical Uses. The potential uses of nanoscale materials in the field of medicine are of particular interest to researchers. Theoretically, nanorobots could be programmed to perform functions that would eliminate the possibility of infection at a wound site. They could also speed healing. Smart materials could be designed to dispense medication in appropriate doses when a virus or bacteria is encountered. Sensors could be used to alert physicians to the first stages of malignancy. There is great potential for nanomaterials to meet the needs of aging populations without intrusive surgeries requiring lengthy recovery and rehabilitation.

As an example of the potential medical benefits of nanotechnology, researches pursued several new uses for the technology in the early 2020s. According to a paper published in the journal Frontiers in Bioengineering and Biotechnology, scientists studied the use of nanotechnology to stop the spread of tropical mosquitos that can carry diseases such as yellow fever, dengue, and the Zika virus. Another 2020 study published in the Journal of Drug Delivery Science and Technology, touted the technology’s success in helping patients heal from nerve injuries.

Energy. Nanomaterials also hold promise for energy applications. With nanostructures, components of heating and cooling systems could be tailored to control temperatures with greater efficiency. This could be accomplished by engineering the materials so that some types of atoms, such as oxygen, can pass through, while others, such as mold or moisture, cannot. With this level of control, living conditions could be designed to meet the specific needs of different categories of residents.

Extending the life of batteries and prolonging their charge has been the subject of decades of research. With nanoparticles, researchers at Rutgers University and Bell Labs have been able to better separate the chemical components of batteries, resulting in longer battery life. With further nanoscale research, it may be possible to alter the internal composition of batteries to achieve even greater performance.

Light-emitting diode (LED) technology uses 90 percent less energy than conventional, non-LED lighting. It also generates less heat than traditional metal-filament light bulbs. Nanomanufacturing would make it possible to create a new generation of efficient LED lighting products.

Electronics. Moore's law states that transistor density on integrated circuits doubles about every two years. With the advent of nanotechnology, the rate of miniaturization has the potential to double at a much greater rate. This miniaturization will profoundly affect the computer industry. Computers will become lighter and smaller as nanoparticles are used to increase everything from screen resolution to battery life while reducing the size of essential internal components, such as capacitors.

Social Context and Future Prospects

Whether nanotechnology will ultimately be good or bad for the human race remains to be seen, as it continues to be incorporated into more and more products and processes, both common and highly specialized. There is tremendous potential associated with the ability to manipulate individual atoms and molecules, to deliver medications to a disease site, and to build products such as cars that are lighter yet stronger than ever. Much research is devoted to using nanotechnology to improve fields such as pollution mitigation, energy efficiency, and cell and tissue engineering. However, there also exists the persistent worry that humans will lose control of this technology and face what Drexler called a "gray goo" scenario, in which self-replicating nanorobots run out of control and ultimately destroy the world.

Despite fears linked to cutting-edge technology, many experts, including nanotechnology pioneers, consider such doomsday scenarios involving robots to be highly unlikely or even impossible outside of science fiction. More worrisome, many argue, is the potential for nanotechnology to have other unintended negative consequences, including health impacts and ethical challenges. Some studies have shown that the extremely small nature of nanoparticles makes them susceptible to being breathed in or ingested by humans and other animals, potentially causing significant damage. Structures including carbon nanotubes of graphene have been linked to cancer. Furthermore, the range of possible applications for nanotechnology raises various ethical questions about how, when, and by whom such technology can and should be used, including issues of economic inequality and notions of "playing God." These risks, and the potential for other unknown negative impacts, have led to calls for careful regulation and oversight of nanotechnology, as there has been with nuclear technology, genetic engineering, and other powerful technologies. Further highlighting the importance of the field of nanotechnology, in 2020, the US Food and Drug Administration, responsible for overseeing a wide range of products across the many categories within its purview, released a report detailing the continued studies, partnerships, and regulation considerations the agency had conducted and committed to since 2007, the year in which it last reported on the subject.

Furthermore, in 2020, efforts to create a vaccine as quickly but safely as possible for the devastating coronavirus disease 2019 (COVID-19) pandemic brought the potential for the use of nanotechnology in the field of medicine to prominence once more. The two vaccines for the disease ultimately produced by the companies Moderna and Pfizer implemented messenger RNA (mRNA) technology, and lipid nanoparticles, which had been used as part of drug delivery in the past, were involved in protectively carrying the mRNA to the proper location within cells.

The 2023 Nobel Prize in Chemistry was awarded to three researchers (Moungi G. Bawendi, Louis E. Brus, and Aleksey Yekimov) in recognition of their work in discovering and utilizing quantum dots, a type of bright crystalline nanoparticle capable of displaying different colors. The three specialists, who pioneered quantum dot research and fabrication in the 1980s and 1990s, paved the way for the use of quantum dots in such fields as technology (for use in televisions and other displays) and medicine (for use in marking living tissue to aid in surgeries). In addition to their practical use in these fields, quantum dots were seen by experts as the cornerstone of future nanotechnology developments.

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