Nanotechnology involves working with extremely small things — things that can be measured in nanometers. A nanometer is one millionth the size of a pinhead. That’s also about the width of ten hydrogen atoms laid out side by side. Scientists in many fields — from medicine to computing to materials science — are attempting to build things that are smaller than a few hundred nanometers. Ralph Merkle — a theorist at the Foresight Institute in Palo Alto, California — says it could be done with a tiny robotic arm.
Ralph Merkle: Something that might be a fraction of a micron in size, and would be able to position its tip to a fraction of an atomic diameter, and would literally be able to pick up and assemble molecular parts and put them together much as we might pick up parts on the scale of you and me.
Some scientists counter that physical challenges might make such a “nanorobotic arm” impossible. Still, using current tools, scientists have already produced tiny identification tags that stick to cancer cells — and computer circuits made by laying down atoms, one by one.
Nanotechnology is a catch-all term. People from a broad range of traditional science fields — from medicine to computing to molecular biology to physics — also consider themselves to be a part of this new field. Nanotechnolgy existed long before there was a term for it. Scientists making vaccines in the 1950s were already working with viruses on the nano scale. For over 100 years, tire manufacturers have added nano-sized carbon black particles — or high-tech soot — to tires to make them stronger.
The term “nanotechnology” was coined in 1974, but the idea became widely popularized in the mid 1980s. Nano is the greek prefix for “dwarf” — in scientific terms, it means “one billionth.” So a nanometer is one billionth of a meter.
Depending on who you talk to, nanotechnology might simply mean the process of making things on the nano scale. Those things might be raw materials for larger things — such as bulletproof vests. They might be simple machines such as gears and motors or complex machines that can build other things. Or they might be electronic devices.
This work has already led to improvements in computer data storage and more compact computer microchips. It’s also produced “biotags” — tiny semiconductor dots that can be used to label specific genes, cancerous cells, antibodies for disease and a whole host of other biological targets. Other “nanoproducts” in use today include catalysts for converting hydrocarbons into gasoline, nanoparticles in sunscreen to make them clear and “liposomes” — lipid spheres used to deliver AIDS drugs.
On the other hand, nanotechnology might mean studying how matter behaves on the nano scale. Scientists doing this end of things are trying to understand how this miniature world differs from ours. In other words, how is picking up an atom different from picking up a phone book? To do that kind of research, scientists need sensors that can help them see what’s going on in the nano world. Scanning probe microscopes — such as scanning tunneling microscopes or atomic force microscopes — are just such tools.
You can create a nanomaterial in two ways:
- “top-down” — that is, you chisel away or add material to create what you want. Some computer microchips are created using this approach.
- “bottom-up” — that is, you use “self-assembly” or “self replication.” With self-assembly, you put the right items into the right conditions and let them spontaneously come together to create what you want. Long carbon fibers called “nanotubes” are an example of this. With self replication, you create little nanorobots — complete with an energy source, motors, robotic arms, tools and raw materials — that can build nanomaterials or other nanorobots.
Dr. Merkle has suggested making a “nanorobotic arm” that could position atoms one at a time to build nanoproducts or other nanorobots. But there are challenges with that approach. One “nanorobot” working fast would still produce only a very small amount of product in a human lifetime. Merkle thinks a way around this could be to make nanorobots that could make billions of copies of themselves. Then this army of nanorobots could make a lot of “nanoproduct” in a short time. Still, some scientists say the costs and physical challenges may make that impossible.
Researchers hope to use the laws of chemistry to create, as it were, “designer molecules” that will be the building blocks of new products. But, to do this, the location and scope of specific chemical reactions within individual molecules will need to be precisely controlled. According to Dr. Merkle, “We know that if we pour a bunch of chemicals into a test tube and stir, that they can react, but we don’t have any control over where they react.” He added, “With the ability to position molecular parts, we’ll be able to build up a complex structure, by a series of site-specific chemical reactions, and control exactly what that structure is.”
Dr. Merkle thinks we’re anywhere from one to a few decades away from a nanotechnology that could revolutionize manufacturing, medicine, and computing. The pace of progress will largely depend, he says, on the amount of resources we dedicate to the research.
Dr. Merkle has noticed three basic trends in manufacturing:
- Increased precision — building things smaller and smaller (e.g. computer chips);
- Increased flexibility — building more kinds of things than we have in the past;
- Decreased cost of manufacturing.
In the next few decades these trends will have reached their limits, according to Merkle, and those limits will be nanotechnology — controlling the placement of individual atoms and molecules according to the laws of physics. Merkle predicts the cost of any nanotech product eventually will not greatly exceed the cost of the raw materials and the energy used in the production process.
Scientists can already arrange individual atoms in a limited, surface manner (using, for example, a scanning probe microscope). Researchers like Merkle believe fundamental nanotech principles and capabilities have already been demonstrated. The task now, he says, is to refine control so that we can construct three-dimensional molecular structures.
- Scientific American’s nanotech page
- Illustrations of possible positional devices and robotic arms (Zyvex.com)
- Example of how mechanical positioning can lead to site-specific chemical reaction (Zyvex.com)
- Foresight Institute Home Page
- Scientific American, Special Nanotechnology Issue, September 2001, Vol. 285, Number 3
- For some of the physical limitations to nanotechnology, see these three articles:
- Michael Roukes, “Plenty of Room, Indeed”, Scientific American, Special Nanotechnology Issue, September 2001, Vol. 285, Number 3, pg. 48-57.
- Charles M. Lieber, “The Incredible Shrinking Circuit”, Scientific American, Special Nanotechnology Issue, September 2001, Vol. 285, Number 3, pg. 59-64.
- Steven Ashley, “Nanobot Construction Crews”, Scientific American, Special Nanotechnology Issue, September 2001, Vol. 285, Number 3, pg. 84-85.