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Is it Chemistry? Is it Physics?

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The answer is...Yes! Nanotechnology also involves biology, several disciplines of engineering, material science, and medicine. Anywhere molecules and atoms are concerned, nanotechnology can potentially play a role.

When the terms "nanoscience" and "nanotechnology" first appeared, there was a tendency to treat them as a separate scientific discipline or as a new industry. Most practitioners nowadays tend to view nanoscience and nanotechnology as interrelated with other disciplines. Thus, observational tools that image the nano world (like the Atomic Force Microscope) can be applied in several scientific areas, and researchers of different backgrounds and aims are using those tools routinely to answer questions about the material and biological world around us.

For centuries researchers have known that properties of materials, such as hardness, electrical conductivity, elasticity and adhesion are (or are likely to be) dependent on the atomic or crystalline structure of these material. Using information from the Periodic Table of the Elements we could infer atomic bonding and crystal structure, and use these to explain the characteristics of different materials and solutions. What we could not do in the past (but can increasingly do nowadays) was to observe those materials at the molecular or atomic level and test our assumptions and hypotheses directly.

Nanotechnology thus helps us understand better the mechanisms behind many phenomena that were studied earlier in the fields of chemistry, physics and biology. For example, chemists have been creating solutions, suspensions and colloids for hundreds of years. However, they were not able to actually measure and observe the particles or mixtures that they were creating at the molecular level. Now, by being able to measure and view these products at the nanoscale, chemists can more accurately verify performance predictions and understand better the chemical interaction processes.

Is it Physics?

Visualization of human keratinocyte cell line HaCaT cells and the cell junction by AFM. Three-dimensional view showing the height of the cell.
Image Source: MSU Nano Manufacturing Lab

Much of the widely studied field of classical mechanics (which is part of classical physics) describes the motion of physical objects that are measurable and observable by the naked eye (these are known as being on the macroscopic scale). An important sub-filed of classical mechanics is the science of mechanics, which studies the physical laws governing the motion of bodies and systems of bodies. An example of a problem addressed through mechanics is prediction of the trajectory of a baseball which was released under some known initial conditions (such as position, speed, direction and spin). While understanding of motion at the macroscopic scale often provides insight toward analyzing motion on other scales, other mechanisms and rules may have to be considered at the nanoscale.

Consider for example, the interaction between a moving bowling ball and a stationary (and smaller) billiard ball. One way to analyze this interaction is through the study of momentum in this system of objects. The momentum of an object (more precisely its linear momentum) is the product of the mass and velocity of the object. The principle of conservation of momentum is that the total momentum of any group of objects (the two balls in our example) remains the same unless outside forces act on the objects. In our example, with no external forces) the consequence is that the smaller billiard ball will speed away from the bowling ball after the collision, and the bowling ball will continue on its path at a slightly slower pace.

This image was obtained using a Scanning Electron Microscope. It shows gold nanoparticles of various sizes and shapes. Note that individual atoms of gold can be seen as well as the boundaries between different crystal organizational regions of the nano particles. These boundary regions may prove important in understanding the strength of the nano particle.

Suppose now that instead of a bowling ball rolling along, we follow a red blood cell traveling through the blood stream. Instead of the billiard ball, imagine a drug coated nanoparticle made up of several hundred gold atoms. Can we calculate the path of the cell and the nanoparticle after they collide using the same approach we used with the bowling and billiard balls, or should we take into account other mechanisms such as the viscosity of the blood? Is it possible that the interaction between the much larger red blood cell and the small nano particle may convey sufficient energy to the nanoparticle so that the bonding force between its atoms would be overcome and the nanoparticle would fall apart? At the present time the answer to such questions is not always fully known, and such scenarios are studied by nanoscience researchers and practitioners.

Nanoscientists are asking questions like, "How do 100 atoms behave differently than 100,000?" or "How does friction work at the nanoscale? Or "Can we weigh proteins and viruses?" Finding the answers to these questions and others requires knowledge of chemistry, physics, engineering and materials science. Most importantly, the information and knowledge required to answer these questions does not come for only one or two disciplines - it requires a combination of knowledge, investigative and experimental skills from all of the disciplines. In the nanoscience research and product development arena many of the understanding and discoveries are coming about because of the interaction and synergistic efforts of multi-disciplinary teams.

Image Credit: Carole M. Hachney, Keele Univeristy

As implied above, we have a good understanding of how many things work and interact at the macro or micro scale but the understanding is less clear when we start observing the interaction of individual molecules or atoms. This is especially true, and even more so for biological systems. Although answers are being found daily, we do not know the exact interaction mechanism for a drug and various proteins, or how the ion channels in cell membranes "decide' whether to open or close.

The foundational cause of most diseases is fundamentally unknown. This is where the tools of nanotechnology enter into the picture. Researchers are using the tools of nanoscience; atomic force microscope (AFM), scanning electron microscope (SEM), transmission electron microscoe (TEM) and so on to understand how biological systems work at the molecular level.

The image to the right shows the hairs inside the ear of a turtle. By taking images like this we can begin to understand the chemical, electrical and physical operation of very small, complex biological systems.

The bundle in this hair cell is a pyramidal structure composed of sterocilia, which are connected by tip links. When the bundle is displaced, the tip links get stretched and pull open the transduction channels, thereby generating an electrical signal due to positively charged ions. Myosin motor proteins attached to the channels may be involved in active amplification.

Using nanoscience tools such as a nano mechanical indenter, researchers are studying the interface between the sponge-like dentin region and the hard enamel portion of a tooth. This understanding will lead to better dental care, treatment and protection materials.

As researchers begin to understand the molecular level operation of biological systems we can then begin to replicate those systems using tools and methods of chemistry, physics, materials science, and engineering.