This question is a tricky one because "nanotechnology" is such a broad and vague term. Four researchers wrote in to give their views regarding the meaning of nanotechnology and when we will begin to benefit from it.

James D. Plummer, professor of electrical engineering at Stanford University, replies:

"It is difficult to give a precise answer to this question because the term 'nanotechnology' is not well defined. It means different things to different people. Perhaps the broadest definition of a 'nanostructure' is something which has a physical dimension smaller than 0.1 micron, or 100 nanometers (billionths of a meter). Using this definition, integrated circuits will qualify as nanostructures shortly after the turn of the century. Current integrated circuits have minimum dimensions on the order of 0.35 microns. Based on current rates of development, people have projected that around the year 2005 companies will be manufacturing in high volume integrated circuits that have dimensions around 0.1 micron. These numbers refer to the lateral dimensions that are used to define the patterns in integrated circuits.

"Furthermore, the vertical dimensions in current integrated circuits are already as small as five to 10 nanometers. (That is the rough dimension of the gate insulator thickness in current MOS transistors, the most common kind of transistor.) So if size alone defines nanotechnology, then everyone of us is seeing practical benefits of it today.

"When many people think of nanotechnology, however, they think of other, more exotic kinds of devices: nanomachines or medical applications in which tiny machines circulate in the bloodstream cleaning out fat deposits from our arteries, for example. Such technologies are much further off, probably 25 years at least. In those kinds of applications, the problem often lies as much in defining a useful, appropriate application for nanotechnology as it does in actually building the nanostructure."

Nadrian C. Seeman in the department of chemistry at New York University offers another viewpoint:

"This is a very broad question, containing at least two ambiguities. The first lies in the meaning of 'nanotechnology.' To most people, nanotechnology implies an intelligently directed association of chemical components used to make objects and devices on the chemical scale, much as we make them on the macroscopic scale. How does this procedure differ in practice from ordinary chemistry? To my mind, not at all. Chemists try to assemble molecules using a combination of theoretical principles and practical experience to mold molecules that have desired structural and chemical properties. This is also what nanotechnologists do.

"The element of structure is key here. The structural goals of nanotechnology are frequently more ambitious than making a single molecule. Often nanotechnologists wish to make arrays of identical or complexed molecules, sometimes on a scale that will transcend the boundaries of the microscopic and approach the macroscopic. There are two different approaches to this end, 'top-down' and 'bottom-up.' The top-down approach is exemplified by scientists who build objects and molecular arrays using the techniques of scanning probe microscopy. The bottom-up approach is exemplified by investigators who design two- and three-dimensional chemical systems that cohere according to the rules of chemical interactions. The advantage of the top-down approach is its exquisite precision, but its disadvantage is its lack of extensive parallelism--it requires manipulating atoms and molecules practically one by one. In contrast, the bottom-up approach is massively parallel.

"There is already one highly successful nanotechnological system: we call it life. All the goals of nanotechnology are already fulfilled in living systems, and most of our attempts at nanotechnological applications can be called biomimetic, either applying the structural principles of living systems to different compounds or using the compounds of living systems for different purposes. For example, in our laboratory at N.Y.U., we have used analogs of branched DNA molecules (found in the process of genetic recombination) to form stick polyhedra, a cube and a truncated octahedron, whose edges consist of DNA double helices. The polyhedra are assembled from branched molecules that hold together because of the same sticky-ended hydrogen bonding that is used by the cell to direct replication of the genetic code. As in our work, living systems tend to make their structural components on the nanometer scale, rather than on the angstrom scale where most chemists work.

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