Science: Size Matters

What is nanotechnology and why is it so attractive to scientists, business people and the government? Defining the term and the related fields of nanoscience and nanofabrication is difficult due to the multitude of complimentary (and sometimes competing) interpretations. Perhaps the best way to understand nanotechnology is to consider the prefix nano-. It comes from the Greek word nanos which literally means ‘dwarf’. In current English usage, nano- refers to one-billionth. So when we add nano to technology, we are referring to technology that is constructed at a very small scale. For example, nanometer refers to things that are measured in billionths of a meter. To put the nanoscale in perspective, consider that:

• A human hair is about 50,000 nanometers wide and a bacterial cell is a few hundred nanometers across. Ten hydrogen atoms in a row are equal to about one nanometer.
• The difference in size between a nanometer and a human being is about the same as the difference in size between a person and the orbit of the moon around the Earth.
• If a nanometer were equal to the length of your nose, then a red blood cell would be the size of the Empire State Building, a human hair would be two to three miles wide, one of your fingers would span the entire continental United States, and an average person would be size of six or seven planet Earths.

Scientists in the field of nanotechnology have generally defined nanotechnology as the study and manipulation of molecules and structures that are between 1 and 100 nanometers in length or diameter. Unlike other scientific fields, nanotechnology is not defined by one discipline but includes materials science and engineering, molecular chemistry, molecular biology, quantum physics, and many other scientific fields. Researchers from all of these fields have redefined themselves as nanotechnologists and nanoscientists to emphasize their focus on the nanoscale. It is helpful to think of nanotechnology as a toolkit that researchers use to manipulate matter at very small scales.

Nanotechnology is a multidisciplinary field that involves many different types of scientists as well as regulatory officials, business people, and consumers. A number of terms are used to describe nano activities, most commonly nanotechnology and nanoscience. Formally speaking, the difference between nanotechnology and nanoscience is that the former tends to emphasize research of particles at the nanoscale while the latter uses these scientific principles to develop useful applications. However, the distinction between these terms is not so clear in the real world and it is common for researchers to speak about developing nanoscience and nanotechnology simultaneously. In all cases, nanoscience and nanotechnology emphasize the manipulation and creation of nanomaterials at the nanoscale. Other common terms include nanoscale, nanomaterials, and nanomanufacturing.

The nanoscale (1 to 100 nm) is particularly compelling to scientists because it is in this range that materials exhibit very different behaviors. The nanoscale lies between the macroscale (greater than 100 nm) and the microscale (less than 1 nm) and here, substances exhibit peculiar and (hopefully) useful properties. This is due to the unusually high surface-to-volume ratio and the increased importance of the chemical bonds that link molecules. For example, gold is a material that is inert at the macroscale and microscale but is highly reactive at the nanoscale and thus, it is potentially valuable as a catalyst for chemical manufacturing. A number of common molecules exhibit chemical, mechanical, electrical, optical, and magnetic properties that are not present outside of the nanoscale. The goal of nanotechnology is to take advantage of these special properties to develop new products and technologies with superior performance characteristics.

Examples of objects from the macroworld to the microworld

To study and describe the various properties exhibited by nanomaterials, scientists employ a combination of principles from classical mechanics and quantum mechanics. Sir Isaac Newton and others developed classical mechanics in the seventeenth century to describe the motion of objects using a set of natural laws. For example, one can predict the trajectory of a ball flying through the air by applying the law of gravity and Newton’s laws of motion. Conversely, quantum mechanics was developed in the early twentieth century by Max Planck, Albert Einstein, and others to describe phenomena at atomic and subatomic scales where the principles of classical mechanics are not applicable. Quantum mechanics is different from classical mechanics because it is based not on natural laws and predictions but on probability to describe the activities of atoms and their constituents. Nanomaterials are particularly challenging to study because they exist at the boundary between the microworld where quantum mechanics can be applied and the macroworld where classical mechanics is applied.

Further Reading:

• Keiper, Adam. 2003. The nanotechnology revolution, The New Atlantis 17-34.
• Ratner, Mark, and Daniel Ratner. 2003. Nanotechnology: A Gentle Introduction to the Next Big Idea. Upper Saddle River, NJ: Prentice Hall
• Service, Robert F. 2004. Nanotechnology grows up, Science 304:1732-34.
• Stix, Gary. 2001. Little big science, Scientific American 285(3):32-36.
• Wilson, Mick, Kamali Kannangara, Geoff Smith, Michelle Simmons, and Burkhard Raguse. 2002. Nanotechnology: Basic Science and Emerging Technologies. New York, NY: Chapman & Hall.