Systems Issues in the Development of Nanotechnology

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Systems Issues in the Development of
Nanotechnology

• Ralph C. Merkle, Ph.D.
• Principal Fellow, Zyvex

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The Vision
The goal

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

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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

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Replication
There are many ways to make a replicating system

• Von Neumann architecture
• Bacterial self replication
• Drexlers original proposal for an assembler
• Simplified HydroCarbon (HC) assembler
• Exponential assembly
• And many more

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Self replication
The Von Neumann architecture
Universal Computer
Universal Constructor
http//www.zyvex.com/nanotech/vonNeumann.html
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Elements in Von Neumann Architecture
Self replication

• On-board instructions
• Manufacturing element
• Environment
• Follow the instructions to make a new
  manufacturing element
• Copy the instructions

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Self replication
The Von Neumann architecture
Instructions
New manufacturing element
Manufacturing element
http//www.zyvex.com/nanotech/vonNeumann.html
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Self replication
The Von Neumann architecture
Read head
Instructions (tape)
New manufacturing element
Manufacturing element
http//www.zyvex.com/nanotech/vonNeumann.html
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Self replication
Replicating bacterium
DNA
DNA Polymerase
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Elements in replicating bacterium
Self replication

• 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 arent too
  long

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Self replication
Drexlers proposal for an assembler
http//www.foresight.org/UTF/Unbound_LBW/chapt_6.h
tml
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Elements in Drexlers assembler
Self replication

• 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

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Broadcast replication
Broadcast architecure
Macroscopic computer
http//www.zyvex.com/nanotech/selfRep.html
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Advantages of broadcast architecture
Broadcast replication

• Smaller and simpler no instruction storage,
  simplified instruction decode
• Easily redirected to manufacture valuable
  products
• Inherently safe

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

• 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)

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HC assembler
A hydrocarbon bearing
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HC assembler
A hydrocarbon universal joint
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Molecular tools
A hydrogen abstraction tool
http//www.zyvex.com/nanotech/Habs/Habs.html
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Exponential assembly
Broadcast replication
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Elements in exponential assembly
Broadcast replication

• 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

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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

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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

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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)

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Replication
Popular misconceptionsreplicating 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)

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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

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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

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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

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Self replication
A C program that prints outan exact copy of
itself

• main()char q34, n10,a"main() char
  q34,n10,acscprintf(a,q,a,q,n)c"printf(
  a,q,a,q,n)

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Self replication
English translation

• Print the following statement twice, the second
  time in quotes
• Print the following statement twice, the second
  time in quotes

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The Vision
Classical uncertainty
s mean positional error k restoring force kb
Boltzmanns constant T temperature
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The Vision
Classical uncertainty
s 0.02 nm (0.2 Å) k 10 N/m kb 1.38 x 10-23
J/K T 300 K
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Proposal for amolecular robotic arm
The Vision
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Arranging Molecular Building Blocks (MBBs) with
SPMs
Positional assembly

• Picking up, moving, and putting down a molecule
  has only recently been accomplished
• Stacking MBBs with an SPM has yet to be done

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Designing MBBs and SPM tips
Positional assembly

• 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

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The Vision
Complexity of self replicating systems (bits)

• Mycoplasma genitalia 1,160,140
• Drexlers assembler 100,000,000
• Human 6,400,000,000

http//www.zyvex.com/nanotech/selfRep.html
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Approach
Manipulation and bond formation by STM
H. J. Lee and W. Ho, SCIENCE 286, p. 1719,
NOVEMBER 1999
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Approach
Manipulation and bond formation by STM
Saw-Wai Hla et al., Physical Review Letters 85,
2777-2780, September 25 2000
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Approach
What to makeDiamond 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

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Synthesis of diamond todaydiamond CVD
Molecular tools

• 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.
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Some other molecular tools
Molecular tools
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A synthetic strategy for the synthesis of
diamondoid structures
Molecular tools

• Positional assembly (6 degrees of freedom)
• Highly reactive compounds (radicals, carbenes,
  etc)
• Inert environment (vacuum, noble gas) to
  eliminate side reactions

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