Part 3 Proceedings of the Roadmap Working Group The Roadmap development process included four intensive workshops held from October 2005 through December 2006. Following an inaugural workshop San Francisco, the meetings were sponsored by the Battelle Memorial Foundation and hosted by the Oak Ridge, Brookhaven, and Pacific Northwest National Laboratories. The Working Group Proceedings presents a collection of papers, extended abstracts, and personal perspectives contributed by participants in the Roadmap workshops and subsequent online exchanges. These contributions are included with the Roadmap document to make available, to the extent possible, the full range of ideas and information brought to the Roadmap process by its participants. The papers are arranged in the order given below. Atomically Precise Fabrication 01 Atomically Precise Manufacturing Processes 02 Mechanosynthesis 03 Patterned ALE Path Phases 04 Numerically Controlled Molecular Epitaxy 05 Scanning Probe Diamondoid Mechanosynthesis 06 Limitations of Bottom-Up Assembly 07 Nucleic Acid Engineering 08 DNA as an Aid to Self-Assembly 09 Self-Assembly 10 Protein Bioengineering Overview 11 Synthetic Chemistry 12 A Path to a Second Generation Nanotechnology 13 Atomically Precise Ceramic Structures 14 Enabling Nanoscience for Atomically-Precise Manufacturing of Functional Nanomaterials Nanoscale Structures and Fabrication 15 Lithography and Applications of New Nanotechnology 16 Scaling Up to Large Production of Nanostructured Materials Nanotechnology Roadmap Working Group Proceedings I-1 17 Carbon Nanotubes 18 Single-Walled Carbon Nanotubes 19 Oligomer with Cavity for Carbon Nanotube Separation 20 Nanoparticle Synthesis 21 Metal Oxide Nanoparticles Motors and Movers 22 Biological Molecular Motors for Nanodevices 23 Molecular Motors, Actuators, and Mechanical Devices 24 Chemotactic Machines Design, Modeling, and Characterization 25 Atomistic Modeling of Nanoscale Systems 26 Productive Nanosystems: Multi-Scale Modeling and Simulation 27 Thoughts on Prospects for New Characterization Tools 28 Characterization/Instrumentation Capabilities for Nanostructured Materials Applications 29 Nanomedicine Roadmap: New Technology and Clinical Applications 30 Applications for Positionally Controlled Atomically Precise Manufacturing Capability 31 Piezoelectrics and Piezo Applications 32 Fuel Cell Electrocatalysis: Challenges and Opportunities 33 Atomic Precision Materials Development in PEM Fuel Cells 34 Hydrogen Storage 35 The Potential of Atomically Precise Manufacturing in Solid State Lighting 36 Towards Gaining Control of Nanoscale Components and Organization of Organic Photovoltaic Cells 37 Impact of Atomically Precise Manufacturing on Transparent Electrodes 38 Atomically Precise Fabrication for Photonics: Waveguides, Microcavities 39 Impact of Atomically Precise Manufacturing on Waveguide Applications I-2 Working Group Proceedings Nanotechnology Roadmap Paper 01 J. Randall Zyvex Labs Atomically Precise Manufacturing Processes Introduction Simplifying Assumptions In this section, atomically precise manufacturing (APM) The following assumptions are made: will be discussed. As discussed elsewhere, productive nanosystems do not necessarily carry out APM, though that is expected to be one of their most important uses, and that it 1. To do APM, it is required to deliver specific atoms is possible to do APM with methods that do not employ and/or molecules to a particular point in space and to productive nanosystems. The heart of this section is the get them to bind to the product in the desired fashion. discussion of the process of APM whether carried out by The designer of the product will predetermine the productive nanosystems or macroscale machinery and position of each atom or molecule, its binding instrumentation. method, and to some extent the order of the assembly of the atoms and molecules. An atomically precise manufacturing (APM) process will be able to create products where the type, number, and 2. The value of an APM process will increase with the position of all atoms and/or molecules in the product are size and complexity of the product and the range of known. The yield of any manufacturing process is rarely materials that may be designed in. 100%, and we should not expect that APM processes will be free of defects. Assembly By this definition, there are many chemical manufacturing In order to assemble atoms or molecules there must be processes that would qualify as APM, in particular as available binding sites, with some sort of binding interaction bottom-up, self-assembly. However, these chemical that could be covalent, metallic, ionic, or hydrogen bonds, or manufacturing processes have limitations that we expect can some form of Van der Waals interaction. And there must be be overcome by more advanced APM processes. One of the some method of delivering the correct atom or molecule to prime distinctions that one could use to distance more the desired location in a way that will lead to the desired advanced APM processes from the chemical manufacturing interaction that results in the atom or molecule binding to processes today, is that self-assembly tends to produce and becoming part of the desired structure. structures in their minimum energy configuration. Indeed, it is the minimization of energy that drives most chemical In addition, it is necessary to protect the binding site from reactions. having an undesirable interaction with some atom or molecule other than the one that is intended to bind there. The fact that the output of any self-assembly process This is usually accomplished by excluding any undesirable would have to minimize energy in the output product atoms or molecules from the environment by using highly presents some limitations. A microprocessor, the heart of purified feedstock and either highly purified solvents or ultra most electronic computers, is not a minimum energy high vacuum environments. arrangement of the semiconductor, metal, and insulating materials that make up the integrated circuit chip. However, Another component of APM can be protecting the binding the fact that a single self assembly step drives to minimum sites until it is desirable to react/assemble/bind the energy configuration, does not restrict the output of multiple appropriate atom or molecule. This protection is done by a self assembly processes from producing products that are not surrogate atom or molecule that keeps the binding site in their minimum energy configuration. Given a sufficiently unreactive until some process removes the surrogate, clever chemical synthesis approach, very complex molecules “deprotecting” the site. can be created that are certainly not a minimum energy configuration of their constituent atoms. Complex Limitations of Bottom-Up Assembly molecules can self assemble into more complex structures that can be useful. One could argue that the most complex Much of the beauty and complexity in chemical synthesis structures on the planet, multi cell living organisms are is the combinations of chemical reactions that add molecules created by self-assembly. In this section however, the and later remove part (or all) of what was added as the possibility of a top-down, mechanically implemented, complex molecule is built up. computer controlled process will be explored. Nanotechnology Roadmap Working Group Proceedings 01-1 Paper 01 J. Randall Zyvex Labs When diffusion is the method of delivering the atom or designed binding site. This results in the ability to create molecule, there are two problems and one large advantage. directly structures that are not in their minimum energy The advantage is that diffusion is a massively parallel configuration. This also leads directly to the second process with little or no cost. The disadvantages are the advantage of avoiding the need to protect and deprotect stochastic nature of the process and the lack of spatial binding sites. When the atomic or molecular building blocks control. The stochastic nature of the self-assembly leads to are delivered to the binding site by some mechanism that yields of less than 100% on any one step. When the controls its path then other potential binding sites do not synthesis is involves many steps the problem is need to be protected. The ability to avoid the need to protect compounded. For example the ability to synthesize designed and deprotect binding sites is an attractive feature. sequences of DNA is of huge value, but these synthesized The requirement of having to directly manipulate each DNA strands are limited to a modest number of base pairs, atom or molecule would seem to be a huge disadvantage because of this very problem. compared to self-assembly where the delivery of atoms or The lack of spatial control creates problems when molecules in a massively parallel manner is easily multiple identical binding sites exist that need different accomplished. It is an important point that, productive components added to them. It is difficult if not impossible nanosystems could also provide the massive parallelism to address these identical binding sites when using diffusion required to produce atomically precise products cost as the delivery mechanisms. effectively. In this section however, we will not explore the requirements for achieving the productive nanosystems While there are techniques to deal with these limitations, themselves but rather the mechanisms that could be used by they do result in trade off between the complexity of the end any approach to APM. Thus we will consider