Systems Issues in the Development of Nanotechnology

2. Systems Issues in the Development of Nanotechnology Ralph C. Merkle, Ph.D. Principal Fellow, Zyvex

3. The Vision The goal • Fabricate most structures consistent with physical law • Get essentially every atom in the right place • Inexpensive (~10-50 cents/kilogram)

4. The Vision Two important ideas • Self replication (for low cost) • Positional assembly (so parts go where we want them to go) • Both concepts are applicable at many different sizes

5. Replication There are many ways to make a replicating system • Von Neumann architecture • Bacterial self replication • Drexler’s original proposal for an assembler • Simplified HydroCarbon (HC) assembler • Exponential assembly • And many more…

6. Self replication The Von Neumann architecture Universal Computer Universal Constructor http://www.zyvex.com/nanotech/vonNeumann.html

7. Self replication Elements in Von Neumann Architecture • On-board instructions • Manufacturing element • Environment • Follow the instructions to make a new manufacturing element • Copy the instructions

8. Self replication The Von Neumann architecture Instructions New manufacturing element Manufacturing element http://www.zyvex.com/nanotech/vonNeumann.html

9. Self replication The Von Neumann architecture Read head Instructions (tape) New manufacturing element Manufacturing element http://www.zyvex.com/nanotech/vonNeumann.html

10. Self replication Replicating bacterium DNA DNA Polymerase

11. Self replication Elements in replicating bacterium • Instructions (DNA polymer) • Ribosome interprets mRNA derived from DNA (basic positional assembly) • Proteins self assemble • Liquid environment with feedstock molecules • Able to synthesize most proteins that aren’t too long

12. Self replication Drexler’s proposal for an assembler http://www.foresight.org/UTF/Unbound_LBW/chapt_6.html

13. Self replication Elements in Drexler’s assembler • Instructions (polymer) • Molecular computer • Molecular positional device (robotic arm) • Liquid environment with feedstock molecules • Able to synthesize most arrangements of atoms consistent with physical law

14. Molecular constructor Molecular constructor Molecular constructor Broadcast replication Broadcast architecure Macroscopic computer http://www.zyvex.com/nanotech/selfRep.html

15. Broadcast replication Advantages of broadcast architecture • Smaller and simpler: no instruction storage, simplified instruction decode • Easily redirected to manufacture valuable products • Inherently safe

16. Broadcast replication Overview of HC assembler Approximate dimensions: 1,000 nm length 100 nm radius Compressed neon http://www.zyvex.com/nanotech/casing.html

17. Broadcast replication Elements in HC assembler • No on-board instructions (acoustic broadcast) • No on-board computer • Molecular positional device (robotic arm) • Liquid environment: solvent and three feedstock molecules • Able to synthesize most stiff hydrocarbons (diamond, graphite, buckytubes, etc)

18. HC assembler A hydrocarbon bearing

19. HC assembler A hydrocarbon universal joint

20. Molecular tools A hydrogen abstraction tool http://www.zyvex.com/nanotech/Habs/Habs.html

21. Broadcast replication Exponential assembly

22. Broadcast replication Elements in exponential assembly • No on-board instructions (electronic broadcast) • External X, Y and Z (mechanical broadcast) • No on-board computer • MEMS positional device (2 DOF robotic arm) • Able to assemble appropriate lithographically manufactured parts pre-positioned on a surface in air

23. Replication Take home message: the diversity of replicating systems is enormous • Functionality can be moved from the replicating component to the environment • On-board / off board instructions and computation • Positional assembly at different size scales • Very few systematic investigations of the wide diversity of replicating systems

24. Replication An overview of replicating systemsfor manufacturing • Advanced Automation for Space Missions, edited by Robert Freitas and William Gilbreath NASA Conference Publication 2255, 1982 • A web page with an overview of replication: http://www.zyvex.com/nanotech/selfRep.html

25. Replication Terminology • The term “self replication” carries assumptions and connotations (mostly derived from biological systems) that are grossly incorrect or misleading when applied to many replicating systems (broadcast systems such as the HC assembler and Rotapod, as well as many others)

26. Replication Popular misconceptions:replicating systems must • be like living systems • be adaptable (survive in natural environment) • be very complex • have on-board instructions • be self sufficient (uses only very simple parts)

27. Replication Misconceptions are harmful • Fear of self replicating systems is based largely on misconceptions • Misplaced fear could block research • And prevent a deeper understanding of systems that might pose serious concerns • Foresight Guidelines address the safety issues

28. Replication Research is a good ideabanning research is a bad idea • Advances in technology can greatly reduce human suffering • Informed decisions require research, uninformed decisions can be dangerous • A 99.99% effective ban means the unregulated 0.01% will develop and deploy the technology

29. Replication What is needed • Development and analysis of more replicating architectures (convergent assembly, others) • Systematic study of existing proposals • Education of the scientific community and the general public

31. Self replication A C program that prints outan 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);}

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

33. The Vision Classical uncertainty σ: mean positional error k: restoring force kb: Boltzmann’s constant T: temperature

34. The Vision Classical uncertainty σ: 0.02 nm (0.2 Å) k: 10 N/m kb: 1.38 x 10-23 J/K T: 300 K

35. Proposal for amolecular robotic arm The Vision

36. Positional assembly Arranging Molecular Building Blocks (MBBs) with SPMs • Picking up, moving, and putting down a molecule has only recently been accomplished • Stacking MBBs with an SPM has yet to be done

37. Positional assembly Designing MBBs and SPM tips • The next step is to design an MBB/SPM tip combination that lets us pick up, move, put down, stack and unstack the MBBs • A wide range of candidate MBBs are possible

38. The Vision Complexity of self replicating systems (bits) • Mycoplasma genitalia 1,160,140 • Drexler’s assembler 100,000,000 • Human 6,400,000,000 http://www.zyvex.com/nanotech/selfRep.html

39. Approach Manipulation and bond formation by STM H. J. Lee and W. Ho, SCIENCE 286, p. 1719, NOVEMBER 1999

40. I I Approach Manipulation and bond formation by STM Saw-Wai Hla et al., Physical Review Letters 85, 2777-2780, September 25 2000

41. Approach What to make:Diamond Physical Properties Property Diamond’s value Comments Chemical reactivity Extremely low Hardness (kg/mm2) 9000 CBN: 4500 SiC: 4000 Thermal conductivity (W/cm-K) 20 Ag: 4.3 Cu: 4.0 Tensile strength (pascals) 3.5 x 109 (natural) 1011 (theoretical) Compressive strength (pascals) 1011 (natural) 5 x 1011 (theoretical) Band gap (ev) 5.5 Si: 1.1 GaAs: 1.4 Resistivity (W-cm) 1016 (natural) Density (gm/cm3) 3.51 Thermal Expansion Coeff (K-1) 0.8 x 10-6 SiO2: 0.5 x 10-6 Refractive index 2.41 @ 590 nm Glass: 1.4 - 1.8 Coeff. of Friction 0.05 (dry) Teflon: 0.05 Source: Crystallume

42. Molecular tools Synthesis of diamond today:diamond CVD • Carbon: methane (ethane, acetylene...) • Hydrogen: H2 • Add energy, producing CH3, H, etc. • Growth of a diamond film. The right chemistry, but little control over the site of reactions or exactly what is synthesized.

43. Molecular tools Some other molecular tools

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