1 Whither nanotechnology? Ralph C. Merkle Distinguished Professor of Computing Georgia Tech College of Computing

2 Web pages

3 Health, wealth and atoms

4 Arranging atoms Flexibility Precision Cost

5 Richard Feynman,1959 There’s plenty of room at the bottom

6 1980’s, 1990’s First STM By Binnig and Rohrer Experiment and theory

7 President Clinton, 2000 “Imagine the possibilities: materials with ten times the strength of steel and only a small fraction of the weight -- shrinking all the information housed at the Library of Congress into a device the size of a sugar cube -- detecting cancerous tumors when they are only a few cells in size.” The National Nanotechnology Initiative

8 Arrangements of atoms. Today The goal

9.

10 Positional assembly

11 H. J. Lee and W. Ho, SCIENCE 286, p. 1719, NOVEMBER 1999 Experimental

12 Theoretical

13 Manufacturing is about moving atoms Molecular mechanics studies the motions of atoms Molecular mechanics is based on the Born-Oppenheimer approximation Molecular mechanics

14 The carbon nucleus has a mass over 20,000 times that of the electron Moves slower Positional uncertainty smaller Born-Oppenheimer

15 Treat nuclei as point masses Assume ground state electrons Then the energy of the system is fully determined by the nuclear positions Directly approximate the energy from the nuclear positions, and we don’t even have to compute the electronic structure Born-Oppenheimer

16 Internuclear distance Energy Hydrogen molecule: H 2

17 Hydrocarbon machines

18 Molecular machines

19 Theoretical

20 σ:mean positional error k: restoring force k b : Boltzmann’s constant T:temperature Thermal noise

21 σ:0.02 nm (0.2 Å) k: 10 N/m k b : 1.38 x J/K T:300 K Thermal noise

22 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 Diamond physical properties What to make

23 Making diamond today Illustration courtesy of P1 Diamond Inc.

24 Hydrogen abstraction tool

25 Other molecular tools

26 Some journal publications Theoretical Analysis of Diamond Mechanosynthesis. Part I. Stability of C2 Mediated Growth of Nanocrystalline Diamond C(110) Surface, J. Comp. Theor. Nanosci. 1(March 2004), Jingping Peng, Robert A. Freitas Jr., Ralph C. Merkle. In press. Theoretical Analysis of Diamond Mechanosynthesis. Part II. C2 Mediated Growth of Diamond C(110) Surface via Si/Ge-Triadamantane Dimer Placement Tools, J. Comp. Theor. Nanosci. 1(March 2004). David J. Mann, Jingping Peng, Robert A. Freitas Jr., Ralph C. Merkle, In press. Theoretical analysis of a carbon-carbon dimer placement tool for diamond mechanosynthesis, Ralph C. Merkle and Robert A. Freitas Jr., J. Nanosci. Nanotechnol. 3 June (Abstract)Theoretical analysis of a carbon-carbon dimer placement tool for diamond mechanosynthesisAbstract A proposed "metabolism" for a hydrocarbon assembler, Nanotechnology 8 (1997) pages A proposed "metabolism" for a hydrocarbon assembler Theoretical studies of reactions on diamond surfaces, by S.P. Walch and R.C. Merkle, Nanotechnology 9 (1998) pages Theoretical studies of reactions on diamond surfaces Theoretical studies of a hydrogen abstraction tool for nanotechnology, by Charles Musgrave, Jason Perry, Ralph C. Merkle and William A. Goddard III; Nanotechnology 2 (1991) pages Theoretical studies of a hydrogen abstraction tool for nanotechnologyCharles MusgraveWilliam A. Goddard III

27 Self replication A redwood tree (sequoia sempervirens) 112 meters tall Redwood National Park

28 The Von Neumann architecture Universal Computer Universal Constructor Self replication

29 Drexler’s proposal for an assembler Self replication

30 Exponential assembly

31 Convergent assembly

32 Kinematic Self- Replicating Machines Kinematic Self- Replicating Machines (Landes Bioscience, 2004, in review).Landes Bioscience Reviews the voluminous theoretical and experimental literature about physical self- replicating systems. Freitas and Merkle Self replication

33 Today: potatoes, lumber, wheat, etc. are all about a dollar per kilogram. Tomorrow: almost any product will be about a dollar per kilogram or less. (Design costs, licensing costs, etc. not included) Replication Manufacturing costs per kilogram will be low

34 The impact of a new manufacturing technology depends on what you make Impact

35 We’ll have more computing power in the volume of a sugar cube than the sum total of all the computer power that exists in the world today More than bits in the same volume Almost a billion Pentiums in parallel Powerful Computers Impact

36 New, inexpensive materials with a strength-to-weight ratio over 50 times that of steel Critical for aerospace: airplanes, rockets, satellites… Useful in cars, trucks, ships,... Lighter, stronger, smarter, less expensive Impact

37 50x reduction of structural mass Cost per kilogram under a dollar Reducing cost to low earth orbit by 1,000 or more Impact Nanotechnology/publications/1997/ applications/

38 Mitochondrion ~1-2 by microns Size of a robotic arm ~100 nanometers Impact 8-bit computer

39 “Typical” cell: ~20 microns Mitochondrion Size of a robotic arm ~100 nanometers Scale 8-bit computer

40 Provide oxygen

41 Digest bacteria

42 Digest bacteria

43 Surveys medical applications of nanotechnology Volume I (of three) published in 1999 Robert Freitas, Zyvex Survey of the field Nanomedicine

44 Military applications of molecular manufacturing have even greater potential than nuclear weapons to radically change the balance of power. Global Security Admiral David E. Jeremiah, USN (Ret) Former Vice Chairman, Joint Chiefs of Staff November 9, 1995

45 Core molecular manufacturing capabilities Today Products Overview

46 Correct scientific answer: I don’t know Trends in computer hardware suggestive Beyond typical 3-5 year planning horizon Depends on what we do Babbage’s computer designed in 1830’s How long?

47 Research objectives Mechanosynthesis H abstraction, Carbene insertion, … System design assemblers, robotic arms, … Goals

48 Nanotechnology offers... possibilities for health, wealth, and capabilities beyond most past imaginings. K. Eric Drexler

49 σ 2 :positional variance k: restoring force m: mass of particle ħ :Planck’s constant divided by 2 π Quantum uncertainty

50 C-C spring constant:k~440 N/m Typical C-C bond length:0.154 nm σ for C in single C-C bond:0.004 nm σ for electron (same k):0.051 nm Quantum uncertainty

51 Internuclear distance for bonds Angle (as in H 2 O) Torsion (rotation about a bond, C 2 H 6 ) Internuclear distance for van der Waals Spring constants for all of the above More terms used in many models Quite accurate in domain of parameterization Molecular mechanics

52 Limited ability to deal with excited states Tunneling (actually a consequence of the point-mass assumption) Rapid nuclear movements reduce accuracy Large changes in electronic structure caused by small changes in nuclear position reduce accuracy Molecular mechanics Limitations

53 Buckyballs

54 Buckytubes Fullerenes SWNT MWNT Chirality Buckminsterfullerenes

55 Buckytubes What is “chirality?”

56 Macroscopic computer Molecular constructor Molecular constructor Molecular constructor Broadcast architecture

57 Nanopores Illustration from Harvard Nanopore Group

58 Millipede Illustration from IBM Zurich

59 Minimal assembler

60 System Sub-system part System designs

61 Why don’t we have more system designs? System designs Development times are 10+ years Planning horizons are usually 10- years Research funding focused on “science” FUD

62 Shorten development times Identify intermediate targets Gain support from groups with long planning horizons Lengthen planning horizons Reduce FUD by detailed design and analysis What to do

63 E:Young’s modulus k: transverse stiffness r: radius L:length Stiffness

64 E:10 12 N/m 2 k: 10 N/m r: 8 nm L:100 nm Stiffness

65 Convergent assembly

66 Convergent assembly

67 Convergent assembly

68 SSTO (Single Stage To Orbit) vehicle 3,000 kg total mass (including fuel) 60 kilogram structural mass 500 kg for four passengers with luggage, air, seating, etc. Liquid oxygen, hydrogen Cost: a few thousand dollars Space K. Eric Drexler, Journal of the British Interplanetary Society, V 45, No 10, pp (1992). Molecular manufacturing for space systems: an overview

69 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