The study of nanotechnology

Students interested in nanotechnology often ask what they should study. This web page provides a partial answer to that question. Foresight has a briefing on the subject by Eric Drexler.

Nanosystems

The standard text in the field is Nanosystems: molecular machinery, manufacturing and computation by K. Eric Drexler. Buy a copy and study it.

Molecular mechanics

Any manufacturing technology must move atoms from where they are to where we want them to be. How atoms move and the forces that act upon them during their motion are therefore critical areas of study in nanotechnology. This field is called molecular mechanics. A very brief discussion of molecular mechanics and its significance for nanotechnology is available on the web in Computational Nanotechnology. It contains references to further reading.

A classic introduction to molecular mechanics is Molecular Mechanics, by Ulrich Burkert and Norman L. Allinger, ACS Monograph 177, American Chemical Society, 1982. While out of print, it can often be found in campus libraries.

Nanosystems introduces the basic concepts of molecular mechanics in chapter 3. A great advantage of Drexler's treatment is the adoption of consistent SI units. A slow and careful reading of this chapter is worth the effort.

Many other introductions to molecular mechanics are available. Software packages implementing specific approaches to molecular mechanics are available, and can be very useful in learning the concepts.

Positional control, stiffness and elasticity

A central idea in nanotechnology is that of positional control. This can be provided by fairly standard robotic devices. A major difference between conventional robotic devices and the molecular robotic devices used to position molecular components is the need to consider thermal noise. At the molecular scale, components wiggle and jiggle because of Brownian motion. To control this, the component must be held stiffly, i.e., there must be a restoring force which acts to return the component to an equilibrium position if it is displaced. (The existence of a restoring force serves as a good abstract definition of "positional control.") The restoring force is usually assumed to be linear in the displacement: restoring force = k_s times displacement. The constant k_s is a measure of the stiffness of the system. The greater the stiffness, the greater the restoring force and the smaller the deviations of the system from its equilibrium position. The basic equation relating stiffness and positional uncertainty is:

sigma² = kT / k_s

This is equation 5.4 introduced in chapter 5 of Nanosystems. This equation should be memorized and basic applications understood. To use it, it is essential to determine the stiffness k_s. The stiffness of a structure can be determined from its geometry and material properties. The basic concepts are introduced by Feynman in chapters 38 and 39 of The Feynman Lectures on Physics, by R.P. Feynman, R.B. Leighton, and M. Sands, M. Addison-Wesley (1964). Buying the Feynman Lectures is recommended. Read and understand chapters 38 and 39.

Application of these equations to some robotic devices (including the Stewart platform which, because of its great stiffness, is very attractive for molecular robotic applications) is illustrated in A New Family of Six Degree of Freedom Positional Devices. Applications are also discussed in Chapter 5 of Nanosystems and in section 13.4 which discusses a robotic arm.

Self replication

A second central idea in nanotechnology is that of self replication. The student should read the web page introducing self replication and select some of the references therein for further reading. The recursion theorem is basic to self replicating systems. This theorem should be understood. Exercise: write a program which prints out an exact copy of itself. Buy a copy of Kinematic Self-Replicating Machines, it is an excellent survey of the literature.

Further study