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

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

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

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

6 The Von Neumann architecture Universal Computer Universal Constructor Self replication

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

8 The Von Neumann architecture Self replication Manufacturing element New manufacturing element Instructions

9 The Von Neumann architecture Self replication Instructions (tape) Read head Manufacturing element New manufacturing element

10 Replicating bacterium Self replication DNA DNA Polymerase

11 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 Self replication

12 Self replication Drexler’s proposal for an assembler

13 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 Self replication

14 Broadcast replication Macroscopic computer Molecular constructor Molecular constructor Molecular constructor Broadcast architecure

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

16 Compressed neon Approximate dimensions: 1,000 nm length 100 nm radius Broadcast replication Overview of HC assembler

17 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) Broadcast replication

18 A hydrocarbon bearing HC assembler

19 A hydrocarbon universal joint HC assembler

20 A hydrogen abstraction tool Molecular tools

21 Exponential assembly Broadcast replication

22 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 Broadcast replication

23 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 Take home message: the diversity of replicating systems is enormous Replication

24 An overview of replicating systems for 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: Replication

25 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) Terminology Replication

26 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) Popular misconceptions: replicating systems must Replication

27 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 Misconceptions are harmful Replication

28 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 Research is a good idea banning research is a bad idea Replication

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

31 Self replication 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);} A C program that prints out an exact copy of itself

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

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

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

35 Proposal for a molecular robotic arm The Vision

36 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 Positional assembly

37 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 Positional assembly

38 Complexity of self replicating systems (bits) Mycoplasma genitalia 1,160,140 Drexler’s assembler 100,000,000 Human 6,400,000,000 The Vision

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

40 Approach Saw-Wai Hla et al., Physical Review Letters 85, , September Manipulation and bond formation by STM II

41 PropertyDiamond’s valueComments Chemical reactivityExtremely low Hardness (kg/mm2)9000CBN: 4500 SiC: 4000 Thermal conductivity (W/cm-K)20Ag: 4.3 Cu: 4.0 Tensile strength (pascals)3.5 x 10 9 (natural)10 11 (theoretical) Compressive strength (pascals)10 11 (natural)5 x (theoretical) Band gap (ev)5.5Si: 1.1 GaAs: 1.4 Resistivity (W-cm)10 16 (natural) Density (gm/cm3)3.51 Thermal Expansion Coeff (K-1)0.8 x SiO2: 0.5 x Refractive 590 nmGlass: Coeff. of Friction0.05 (dry)Teflon: 0.05 Source: Crystallume Approach What to make: Diamond Physical Properties

42 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. Molecular tools

43 Some other molecular tools Molecular tools

44 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 Molecular tools