Whither nanotechnology?

1
Whither nanotechnology?

• Ralph C. Merkle
• Distinguished Professor of Computing
• Georgia Tech College of Computing

2
Web pages
www.foresight.org
www.zyvex.com/nano
www.nano.gov
3
Health, wealth and atoms
4
Arranging atoms

• Flexibility
• Precision
• Cost

5
Richard Feynman,1959
Theres plenty of room at the bottom
6
1980s, 1990s
Experiment and theory
First STM By Binnig and Rohrer
7
President Clinton, 2000
The National Nanotechnology Initiative

• 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.

8
The goal
Arrangements of atoms
.
Today
9
The goal
The goal
.
10
Positional assembly
11
Experimental
H. J. Lee and W. Ho, SCIENCE 286, p. 1719,
NOVEMBER 1999
12
Theoretical
13
Molecular mechanics

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

14
Born-Oppenheimer

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

15
Born-Oppenheimer

• 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 dont even have to compute the
  electronic structure

16
Hydrogen molecule H2
Energy
Internuclear distance
17
Hydrocarbon machines
18
Molecular machines
19
Theoretical
20
Thermal noise
s mean positional error k restoring force kb
Boltzmanns constant T temperature
21
Thermal noise
s 0.02 nm (0.2 Å) k 10 N/m kb 1.38 x 10-23
J/K T 300 K
22
What to make
Diamond physical properties

• Property Diamonds 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 _at_ 590 nm Glass 1.4 - 1.8
• Coeff. of Friction 0.05 (dry) Teflon 0.05
• Source Crystallume

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 2003. (Abstract)
• A proposed "metabolism" for a hydrocarbon
  assembler, Nanotechnology 8 (1997) pages 149-162.
  
• Theoretical studies of reactions on diamond
  surfaces, by S.P. Walch and R.C. Merkle,
  Nanotechnology 9 (1998) pages 285-296.
• 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
  187-195.

27
Self replication
A redwood tree (sequoia sempervirens) 112 meters
tall Redwood National Park
http//www.zyvex.com/nanotech/selfRep.html
28
Self replication
The Von Neumann architecture
Universal Computer
Universal Constructor
http//www.zyvex.com/nanotech/vonNeumann.html
29
Self replication
Drexlers proposal for an assembler
http//www.foresight.org/UTF/Unbound_LBW/chapt_6.h
tml
30
Exponential assembly
31
Convergent assembly
32
Self replication
Kinematic Self-Replicating Machines (Landes
Bioscience, 2004, in review). Reviews the
voluminous theoretical and experimental
literature about physical self-replicating
systems. Freitas and Merkle
33
Replication
Manufacturing costsper kilogramwill be low

• 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)

34
Impact
The impact of a new manufacturing
technology depends on what you make
35
Impact
Powerful Computers

• Well 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 1021 bits in the same volume
• Almost a billion Pentiums in parallel

36
Impact
Lighter, stronger, smarter, less expensive

• 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, ...

37
Impact

• 50x reduction of structural mass
• Cost per kilogram under a dollar
• Reducing cost to low earth orbit by 1,000 or more

http//science.nas.nasa.gov/Groups/ Nanotechnology
/publications/1997/ applications/
38
Impact
Size of a robotic arm 100 nanometers
8-bit computer
Mitochondrion 1-2 by 0.1-0.5 microns
39
Scale
Mitochondrion
Size of a robotic arm 100 nanometers
8-bit computer
Typical cell 20 microns
40
Provide oxygen
41
Digest bacteria
42
Digest bacteria
43
Survey of the field
Nanomedicine

• Surveys medical applications of nanotechnology
• Volume I (of three) published in 1999
• Robert Freitas, Zyvex

http//www.foresight.org/Nanomedicine
44
Global Security

• Military applications of molecular manufacturing
  have even greater potential than nuclear weapons
  to radically change the balance of power.

Admiral David E. Jeremiah, USN (Ret) Former Vice
Chairman, Joint Chiefs of Staff November 9, 1995
http//www.zyvex.com/nanotech/nano4/jeremiahPaper.
html
45
Overview
Core molecular manufacturing capabilities
Products
Products
Products
Products
Products
Products
Products
Products
Products
Products
Products
Products
Today
Products
Products
Products
Products
Products
Products
Products
Products
Products
Products
Products
Products
Products
46
How long?

• Correct scientific answer I dont know
• Trends in computer hardware suggestive
• Beyond typical 3-5 year planning horizon
• Depends on what we do
• Babbages computer designed in 1830s

47
Research objectives
Goals

• Mechanosynthesis
• H abstraction, Carbene insertion,
• System design
• assemblers, robotic arms,

48

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

49
Quantum uncertainty

• s2 positional variance
• k restoring force
• m mass of particle
• h Plancks constant divided by 2p

50
Quantum uncertainty

• C-C spring constant k440 N/m
• Typical C-C bond length 0.154 nm
• s for C in single C-C bond 0.004 nm
• s for electron (same k) 0.051 nm

51
Molecular mechanics

• Internuclear distance for bonds
• Angle (as in H2O)
• Torsion (rotation about a bond, C2H6)
• 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

52
Molecular mechanics
Limitations

• 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

53
Buckyballs
54
Buckytubes
Fullerenes SWNT MWNT Chirality Buckminsterfulleren
es
55
Buckytubes
What is chirality?
56
Broadcast architecture
Macroscopic computer
http//www.zyvex.com/nanotech/selfRep.html
57
Nanopores
Illustration from Harvard Nanopore Group
58
Millipede
Illustration from IBM Zurich
59
Minimal assembler
60
System designs
System
Sub-system
Sub-system
Sub-system
part
part
part
part
part
part
61
System designs
Why dont we have more system designs?
Development times are 10 years Planning horizons
are usually 10- years Research funding focused on
science FUD
62
What to do

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

63
Stiffness
E Youngs modulus k transverse stiffness r
radius L length
64
Stiffness
E 1012 N/m2 k 10 N/m r 8 nm L 100 nm
65
Convergent assembly
66
Convergent assembly
67
Convergent assembly
68
Space

• 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

K. Eric Drexler, Journal of the British
Interplanetary Society, V 45, No 10, pp 401-405
(1992). Molecular manufacturing for space
systems an overview
69
An overview of replicating systemsfor
manufacturing
Replication

• 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