1. Intermediate and long term objectives in nanotechnologynanotechnology Ralph C. Merkle Xerox PARC www.merkle.com

2. Core molecular manufacturing capabilities Today Products Overview of the development of molecular nanotechnology

3. The abstract goal Fabricate most structures that are specified with molecular detail and which are consistent with physical law Get essentially every atom in the right place Inexpensive manufacturing costs (~10-50 cents/kilogram) http://nano.xerox.com/nano

4. Two essential concepts Self replication (for low cost)Self replication Programmable positional control (to make molecular parts go where we want them to go)Programmable positional control

5. Von Neumann's universal constructorabout 500,000 Internet worm (Robert Morris, Jr., 1988)500,000 Mycoplasma capricolum1,600,000 E. Coli9,278,442 Drexler's assembler100,000,000 Human6,400,000,000 NASA Lunar Manufacturing Facilityover 100,000,000,000 http://nano.xerox.com/nanotech/selfRep.html Complexity of self replicating systems (bits)

6. A proposal for a molecular positional devicemolecular positional device

7. One embodiment of the goal: Drexler’s assembler Molecular computer Molecular constructor Positional deviceTip chemistry

8. Something a bit simpler: the hydrocarbon assembler We want to make diamond The synthesis of diamond using CVD involves reactive species (carbenes, radicals) This requires an inert environment and positional control to prevent side reactions Focusing our attention on stiff hydrocarbons greatly simplifies design and modeling

9. Major subsystems in a simple assembler floating in solutionsimple assembler Positional device Molecular tools Barrier Trans-barrier transport/binding sites Neon intake Pressure actuated ratchets Pressure equilibration

10. The value of a goal: we can work backwards from it (or: it’s hard to build something if you don’t know what it looks like) Backward chaining (Eric Drexler) Horizon mission methodology (John Anderson) Retrosynthetic analysis (Elias J. Corey) Shortest path and other search algorithms in computer science “Meet in the middle” attacks in cryptography

11. The focus today: self replication and molecular tools Molecular tools are made from feedstock molecule(s) Molecular tools are made using an existing set of molecular tools Starting with one set of molecular tools, we must end up with two full sets of molecular tools http://nano.xerox.com/nanotech/ hydroCarbonMetabolism.html

12. A hydrogen abstraction tool http://nano.xerox.com/nanotech/Habs/Habs.html

13. Some other molecular tools

14. Thermal noise, a classical equation:  2 = kT/k s  is the mean positional error (~0.02 nm) k is Boltzmann’s constant (~1.38 x 10 -23 J/K) T is the temperature (~300 K) k s is the stiffness (~ 10 N/m) See page 91 of Nanosystems for a derivation and further discussionNanosystems

15. Feedstock Acetone (solvent) Butadiyne (C 4 H 2, diacetylene; source of carbon and hydrogen) Neon (inert, provides internal pressure) “Vitamin” (transition metal catalyst such as platinum; silicon; tin) http://nano.xerox.com/nanotech/hydroCarbonMetabolism.html

16. A simple binding site for butadiynebinding site

17. These molecular tools should be able to synthesize a remarkably wide range of stiff hydrocarbons. http://nano.xerox.com/nanotech/ hydroCarbonMetabolism.html

18. Overview Start with molecular tools and butadiyne Finish with two sets of molecular tools Assumes the availability of positional control in an inert environment (e.g., vacuum)

19. Positioning and initially bonding to a molecule Intermolecular forces must be used Access is required for the molecular tool(s) which will first bond to the molecule Once attached covalently to a molecular tool, further positional control can be achieved by moving the molecular tool To position butadiyne for its first bonds, think of a hot dog in a hot dog bun

20. The first bonds to butadiyne Radicals could in principle attach at any of the six atoms in butadiyne Carbenes could in principle insert into any of the five bonds in butadiyne

22. Creating two hydrogen abstraction tools

24. Refreshing a hydrogen abstraction tool

26. Separating two hydrogen abstraction tools that are bonded together

28. Radicals weaker than the hydrogen abstraction tool can be created by abstracting a hydrogen from the appropriate precursor

29. We can dispose of excess hydrogen by making hydrogen rich structures

30. Extending a hydrogen abstraction tool

32. Transferring a dimer from a polyyne to a cumulene (the kind of reaction needed to refresh the carbene tool)

34. Parts closure We must be able to synthesize all tools from the available feedstock and a pre-existing set of molecular tools Quantitative parts closure requires that such synthesis does not cause a depletion of the pre-existing set of tools See http://nano.xerox.com/nanotech/ hydroCarbonMetabolism.html for further discussionhttp://nano.xerox.com/nanotech/ hydroCarbonMetabolism.html

35. Core molecular manufacturing capabilities Today Products Overview of the development of molecular nanotechnology

36. The design and modeling of a simple assembler could be done with existing capabilities. This would: Clarify the goal Speed the development of the technology Allow rapid and low cost exploration of design alternatives Clarify what this technology will be able to do