Overview of the emerging nanotechnology field

Nanotechnology “Nano” is a prefix that means “one-billionth” The nanometer is one-billionth of a meter or 1o the 9th power. It is abbreviated “nm” A red blood cell is between 6,000-10,000 nanometers in diameter. A ribosome is approximately 30 nanometers long. The width of a DNA molecule is about 3 nanometers.

Nanotechnology involves creating and manipulating materials at the nano scale. Nanobiotechnology applies the tools and processes of nanotechnology to build devices for studying and manipulating biosystems. In the field of medicine, nanotechnology has transformed drug delivery systems, diagnostic tests and biocompatible coatings for implants, such as replacement joints.

Properties Matter is made up of atoms and molecules with physical and chemical properties. Physical properties can be measured without changing the composition. For example, the boiling and freezing of water; you can measure these temperatures without changing the water into a different chemical.

Chemical properties refer to how the material will interact with other materials. Materials composed of the same atoms and molecules may have different properties depending on their arrangement at the nanoscale. An example is a snowflake! The chemical structure of the water molecule remain the same, although different shapes are formed by nanoscale interactions such as the shape of the dust the flake forms on, temperature, water vapor in the air and the amount of water.

Concerns about Nanotechnology A concern is that we are producing new kinds of particles that were not previously found in nature, and they may have negative effects. Nanoparticles are so small that they may be able to enter and react with cells in ways that larger particles of the same substance would not.

Concerns continued Nanoparticles are being manufactured into more consumer products, which eventually break down and release the nanoparticles. These particles then accumulate in the environment and may bioaccumulate in organisms.

Concerns continued As nano particles break down and enter various food webs, they may biomagnify and potentially build up to toxic levels as they move up the food chain. One potential problem is the release of silver nanoparticles. Silver nanoparticles frequently are used to make antibacterial products such as clothing and food containers. The particles are gradually released into the environment as the products are used, washed and eventually discarded.

Concerns: Siver nanoparticles can cause dangerous changes in soil bacteria populations, reducing the population of bacteria that fix atmospheric nitrogen. These bacteria convert atmospheric nitrogen into ammonia and other nitrogen compounds that can be used by plants. Without these bacteria, the soil becomes infertile. Titanium dioxide nanoparticles found in sunscreen gradually wash off swimmers and accumulate in the water supply, where they may affect aquatic food chains.

Characterizing Materials Material characterization is analyzing the structure and properties of the material to understand how it will work in various applications. It starts with looking at the material, however, nanoscale structures are much too small to be seen with the naked eye or even with a light microscope. Specialized tools such as scanning probe microscopes, atomic force microscopes and helium ion microscopes are used.

Fabricating Materials Fabrication of nanoscale materials are categorized as “top-down” or “bottom-up”. Top-down methods start with existing materials and shape them at the nanoscale. An example is photolithography, where a photosensitive substance is painted onto an underlying substrate such as a silicon wafer like in a computer chip production. The layers are repeated.

Fabricating Materials The “bottom-up” method uses the natural property of molecules and their tendency to organize themselves. An example is like the snowflake that is self assembled.

Challenges One challenge of working at the nanoscale is how to prevent contamination of the materials being fabricated. Because the scale is so small, even the tiniest particles present a threat. Cleanrooms are special facilities designed to keep airborne particles out. Air entering and circulating within a cleanroom is constantly filtered to remove particles.

Challenges continued Special clothing must be worn to keep particles from skin and clothing from contaminating the air. Workers must enter the cleanroom through special airlocks that keep particles out. Special cleaning procedures and training for all staff and ongoing vigilance are required to maintain each cleanroom.