1. Long and medium term goals in molecular nanotechnology Ralph C. Merkle Xerox PARC www.merkle.com

2. Fifth Foresight Conference on Molecular Nanotechnology November 5-8 Palo Alto, CA www.foresight.org/Conferences

3. The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom. It is not an attempt to violate any laws; it is something, in principle, that can be done; but in practice, it has not been done because we are too big. Richard Feynman, 1959 http://nano.xerox.com/nanotech/feynman.html

4. Molecular nanotechnology (a.k.a. molecular manufacturing) 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

5. Possible arrangements of atoms. What we can make today (not to scale)

6. The goal of molecular nanotechnology: a healthy bite..

7. Two ways to create new technologies: Consider what has been done, and improve on it. Design systems de novo based purely on known physical law, then figure out how to make them.

8. . What we can make today (not to scale) If the target is “close” to what we can make, the evolutionary method can be quite effective.. Target

9. . What we can make today (not to scale) But there is every reason to believe that molecular manufacturing systems are not “close” to what we can make today. Molecular Manufacturing

10. To develop tomorrow’s technology starting with today’s we have to: Understand what will be possible tomorrow — which means thinking about things we can not make today Understand what is possible today Find paths from the today we know to the tomorrow we know is possible.

11. Working backwards from the goal as well as forwards from the start 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

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

13. If you don't know where you are going, you will probably wind up somewhere else Laurence J Peter

14. Two more fundamental ideas Self replication (for low cost) Programmable positional control (to make molecular parts go where we want them to go)

15. Von Neumann architecture for a self replicating system Universal Computer Universal Constructor

16. Von Neumann's universal constructorabout 500,000 Internet worm (Robert Morris, Jr., 1988)500,000 Mycoplasma capricolum1,600,000 E. Coli8,000,000 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)

17. A C program that prints out an exact copy of itself main(){char q=34, n=10,*a="main() {char q=34,n=10,*a=%c%s%c; printf(a,q,a,q,n);}%c";printf(a,q,a,q,n);} For more information, see the Recursion Theorem: http://nano.xerox.com/nanotech/selfRep.html

18. English translation: Print the following statement twice, the second time in quotes: “Print the following statement twice, the second time in quotes:”

19. Drexler’s architecture for an assembler Molecular computer Molecular constructor Positional deviceTip chemistry

20. The broadcast architecture Macroscopic computer Molecular constructor Molecular constructor Molecular constructor

21. Advantages of the broadcast architecture Simpler design Fewer parts Inherently safe

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

23. A broadcast method: Acoustic transmissions. 10 megahertz is sufficient, faster is feasible Pressure actuated ratchets. 125 nm 3 volume at 3,200,000 Pascals (~32 atmospheres) provides ~4 x 10 -19 joules (~2.5 ev, ~58 kcal/mole).

24. Simple pressure actuated device Compressed gas External gas Actuator (under tension)

25. A proposal for a molecular positional device

27. 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

28. A simple binding site for butadiyne

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

30. Some other molecular tools

31. Synthesis of diamond today: diamond CVD Carbon: methane (ethane, acetylene...) Hydrogen: H 2 Add energy, producing CH 3, H, etc. Growth of a diamond film. The right chemistry, but little control over the site of reactions or exactly what is synthesized.

32. A synthetic strategy for the synthesis of diamondoid structures Positional control (6 degrees of freedom) Highly reactive compounds (radicals, carbenes, etc) Inert environment (vacuum, noble gas) to eliminate side reactions

33. A modest set of molecular tools should be sufficient to synthesize most stiff hydrocarbons. http://nano.xerox.com/nanotech/ hydroCarbonMetabolism.html

34. The theoretical concept of machine duplication is well developed. There are several alternative strategies by which machine self-replication can be carried out in a practical engineering setting. Advanced Automation for Space Missions Proceedings of the 1980 NASA/ASEE Summer Study http://nano.xerox.com/nanotech/selfRepNASA.html

37. We could design and model an assembler today. This would: Speed the development of the technology Allow rapid and low cost exploration of design alternatives Provide a clearer target for experimental work Give us a clear picture of what this technology will be able to do

38. Rationale for the design of the simple assembler We want to make diamond Known reactions for the synthesis of diamond (diamond CVD) involve reactive species (carbenes, radicals) This requires an inert environment and positional control to prevent side reactions

39. Rationale for the design of a simpler system Forget diamond. Use molecular building blocks (there are a lot to choose from) Combine building blocks using reactions that are relatively specific. Diels-Alder reactions are a good example An inert environment is unnecessary, and positional control can be combined with self- assembly and other methods

40. Disadvantages of Molecular Building Block (MBB) based systems Greatly reduced strength-to-weight ratio Reduced stiffness (poorer positional control for a given size) Slower speed Much smaller range of things can be synthesized

41. Diels-Alder cycloaddition Steps Towards Molecular Manufacturing, by Markus Krummenacker, Chem. Design Autom. News, 9, (1994). http://www.ai.sri.com/~kr/nano/cda-news/link-chemistry.html

42. Can we self assemble a robotic arm?

43. Can we self assemble a Stewart platform?

44. Can we self assemble an octahedron?

45. A Stewart platform is an octahedron in which: The struts are stiff The length of the struts can be changed Struts connect at flexible joints

46. Sliding struts Needed: a method of controlling the relative position of two struts, i.e., of sliding one strut over a second strut in a controlled fashion to extend and shorten the combined two-strut unit.

47. Sliding struts ABCABCABCABCABCABCABCABCABCABCABCABC a a a a | | | | x x x x XYZXYZXYZXYZXYZXYZXYZXYZXYZXYZXYZXYZ a | x joins the two struts

48. Sliding struts ABCABCABCABCABCABCABCABCABCABCABCABC a c a ca c a |/ |/ | / | xy xy x y x XYZXYZXYZXYZXYZXYZXYZXYZXYZXYZXYZXYZ a | x join the two struts c | y and

49. Sliding struts ABCABCABCABCABCABCABCABCABCABCABCABC c c c c | | | | y y y y XYZXYZXYZXYZXYZXYZXYZXYZXYZXYZXYZXYZ Joins the two struts, which have now moved over one unit. c | y Cycling through a-x, c-y and b-z produces controlled relative motion of the two struts.

50. Can today’s molecular motors be modified so they can be controllably stepped? Chemical signals Acoustic signals Optical (photochemical) signals Other

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

52. The problems of chemistry and biology can be greatly helped if our ability to see what we are doing, and to do things on an atomic level, is ultimately developed---a development which I think cannot be avoided. Richard Feynman, 1959 http://nano.xerox.com/nanotech/feynman.html