Here I continue my attempt to define what is meant by the term nanotechnology. In Part 1 I tried to define the relevant length-scale, the nanoscale, and in Part 2 I made the distinction between nanoscience and nanotechnology. This leaves us with a definition of nanotechnology that includes any branch of technology that results from our ability to control and manipulate matter on the nanoscale.
This is impossibly broad, and a lot of trouble continues to be caused by people confusing the many very different technologies that are grouped together in this word nanotechnology. I’ve found it useful to break the definition up in the following way (of course the boundaries between the categories are porous and arbitrary):
Incremental nanotechnology involves improving the properties of many materials by controlling their nanoscale structure. Plastics, for example, can be reinforced by nanoscale clay particles, making them stronger, stiffer and more chemically resistant. Cosmetics can be formulated in which the oil phase is much more finely dispersed, improving the feel of the product on the skin. Textiles can be coated with nanoscale layers to alter their wetting properties, making them stain-resistant. This kind of nanotechnology is essentially a continuation of existing trends in disciplines like materials science, colloid science and powder technology. Most commercially available products that are said to be based on nanotechnology fall into this category. The science underlying them is sound and the products often are big improvements on what has gone before. However, they do not really represent a decisive break from existing products, many of which already involve nanotechnology as defined this way, even if they aren’t marketed as owing anything to nanotechnology.
Evolutionary nanotechnology involves scaling existing technologies down in size to the nanoscale. Here we generally move beyond simple materials that have been redesigned at the nanoscale to functional devices. Such devices could, for example, sense the environment, process information, or convert energy from one form to another. They include nanoscale sensors, which exploit the huge surface area of nanostructured materials like carbon nanotubes to detect environmental contaminants or biochemicals. Other products of evolutionary nanotechnology are semiconductor nanostructures such as quantum dots and quantum wells which are be used to build better solid-state lasers. Another, less well known but potentially important area is in the development of nano-structures that can wrap up molecules and release them under some stimulus; the most obvious use for these is in drug delivery.
Radical nanotechnology involves sophisticated nanoscale machines, operating with nanoscale precision. K. Eric Drexler pointed out in Engines of Creation, that we have an existence proof for such a technology in cell biology, which gives us many remarkable examples of such nanoscale machines. Drexler sketched out, in Nanosystems, one particular route to achieve a radical nanotechnology, which involved a mechanical engineering paradigm executed largely in diamond-like carbon. This is often referred to as molecular nanotechnology or MNT. It’s important to realise that MNT isn’t the only conceivable radical nanotechnology. Bionanotechnology refers to an approach in which biological nanomachines are reassembled in artifical contexts, while one can imagine various biomimetic approaches to radical nanotechnology in which design principles from biology are executed in synthetic materials. This sort of approach is the subject of my book Soft Machines.