Chapter 1
Introduction and Overview

1.1. Why molecular manufacturing?

The following devices and capabilities appear to be both physically possible and practically realizable:

• Programmable positioning of reactive molecules with ~0.1 nm precision

• Mechanosynthesis at >10⁶ operations/device · second

• Mechanosynthetic assembly of 1 kg objects in <10⁴ s

• Nanomechanical systems operating at ~10⁹ Hz

• Logic gates that occupy ~10^–26 m³ (~10^{– 8} μ³)

• Logic gates that switch in ~0.1 ns and dissipate <10^{– 21} J

• Computers that perform 10¹⁶ instructions per second per watt

• Cooling of cubic-centimeter, ~10⁵ W systems at 300 K

• Compact 10¹⁵ MIPS parallel computing systems

• Mechanochemical power conversion at >10⁹ W/m ³

• Electromechanical power conversion at >10¹⁵ W/m ³

• Macroscopic components with tensile strengths >5×10¹⁰ Pa

• Production systems that can double capital stocks in <10 ⁴ s

Of these capabilities, several are qualitatively novel and others improve on present engineering practice by one or more orders of magnitude. Each is an aspect or a consequence of molecular manufacturing.

1.2. What is molecular manufacturing?

This volume describes the fundamental principles of molecular machinery and applies them to nanomechanical devices and systems, including molecular manufacturing systems and computers. At present, however, these are unfamiliar topics. New fields often need new terms to describe their characteristic features, and so it may be excusable to begin with a few definitions: Molecular manufacturing is the construction of objects to complex, atomic specifications using sequences of chemical reactions directed by nonbiological molecular machinery. Molecular nanotechnology comprises molecular manufacturing together with its techniques, its products, and their design and analysis; it describes the field as a whole. Mechanosynthesis—mechanically guided chemical synthesis—is fundamental to molecular manufacturing: it guides chemical reactions on an atomic scale by means other than the local °steric * and electronic properties of the ° reagents; it is thus distinct from (for example) enzymatic processes and present techniques for organic synthesis.¤

At the time of this writing, positional chemical synthesis is at the threshold of realization: precise placement of atoms and molecules has been demonstrated (for example, see Eigler and Schweizer, 1990), but flexible, extensible techniques remain in the domain of design and theoretical study (Part III), as does the longer-term goal of molecular manufacturing (Chapter 14). Accordingly, the implementation of molecular nanotechnologies like those analyzed in Part II awaits the development of new tools. This volume is addressed both to those concerned with identifying promising directions for current research, and to those concerned with understanding and preparing for future technologies.

The following chapters form three parts: Part I describes the chief physical principles and phenomena of importance in molecular machinery and manufacturing. Part II applies the results of Part I to the design and analysis of components and systems (yielding the conclusions summarized in Section 1.1). Part III then describes implementation pathways leading from our current technology base to systems like those described in Part II.

The rest of the present section attempts to clarify the nature of the topic by discussing an example of a nanomechanical device and by presenting a chemical perspective on molecular manufacturing. Sections 1.3 to 1.5 present a set of comparisons between this and other fields (mechanical engineering, microtechnology, chemistry, and molecular biology), a discussion of overall approach (including objectives, level, scope, and assumptions), and an overview of the later chapters and how they fit together. Table 1.1 lists some of the known problems and constraints that are addressed elsewhere in this volume.

Table 1.1. Some known issues, problems, and constraints

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Thermal excitation
Thermal and quantal positional uncertainty
Quantum-mechanical tunneling
Bond energies, strengths, and stiffnesses
Feasible chemical transformations
Electric field effects
Contact electrification
Ionizing radiation damage
Photochemical damage
Thermomechanical damage
Stray reactive molecules
Device operational reliabilities
Device operational lifetimes
Energy dissipation mechanisms
Inaccuracies in molecular mechanics models
Limited scope of molecular mechanics models
Limited scale of accurate quantal calculations
Inaccuracy of semiempirical models
Providing ample safety margins for modeling errors

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* Words appearing in the Glossary are sometimes prefixed with a small circle, e.g., °steric.

¤ Considering the words in isolation, the terms molecular nanotechnology and molecular manufacturing could instead be interpreted to include much of chemistry, and mechanosynthesis could be interpreted to include substantial portions of enzymology and molecular biology. These established fields, however, are already named; the above terms will serve best if reserved for the fields they have been coined to describe, or for borderline cases that emerge as these fields are developed.