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

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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


The Vision

The goal

  • Fabricate most structures consistent with physical law

  • Get essentially every atom in the right place

  • Inexpensive (~10-50 cents/kilogram)


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


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…


Self replication

The Von Neumann architecture

Universal

Computer

Universal

Constructor

http://www.zyvex.com/nanotech/vonNeumann.html


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


Self replication

The Von Neumann architecture

Instructions

New

manufacturing

element

Manufacturing

element

http://www.zyvex.com/nanotech/vonNeumann.html


Self replication

The Von Neumann architecture

Read head

Instructions

(tape)

New

manufacturing

element

Manufacturing

element

http://www.zyvex.com/nanotech/vonNeumann.html


Self replication

Replicating bacterium

DNA

DNA Polymerase


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


Self replication

Drexler’s proposal for an assembler

http://www.foresight.org/UTF/Unbound_LBW/chapt_6.html


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


Molecular

constructor

Molecular

constructor

Molecular

constructor

Broadcast replication

Broadcast architecure

Macroscopic

computer

http://www.zyvex.com/nanotech/selfRep.html


Broadcast replication

Advantages of broadcast architecture

  • Smaller and simpler: no instruction storage, simplified instruction decode

  • Easily redirected to manufacture valuable products

  • Inherently safe


Broadcast replication

Overview of HC assembler

Approximate dimensions:

1,000 nm length

100 nm radius

Compressed neon

http://www.zyvex.com/nanotech/casing.html


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)


HC assembler

A hydrocarbon bearing


HC assembler

A hydrocarbon universal joint


Molecular tools

A hydrogen abstraction tool

http://www.zyvex.com/nanotech/Habs/Habs.html


Broadcast replication

Exponential assembly


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


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


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


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)


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)


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


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


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


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);}


Self replication

English translation:

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

“Print the following statement twice, the second time in quotes:”


The Vision

Classical uncertainty

σ:mean positional error

k: restoring force

kb: Boltzmann’s constant

T:temperature


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


Proposal for amolecular robotic arm

The Vision


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


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


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


Approach

Manipulation and bond formation by STM

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


I

I

Approach

Manipulation and bond formation by STM

Saw-Wai Hla et al., Physical Review Letters 85, 2777-2780, September 25 2000


Approach

What to make:Diamond Physical Properties

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 109 (natural)1011 (theoretical)

Compressive strength (pascals)1011 (natural)5 x 1011 (theoretical)

Band gap (ev)5.5Si: 1.1 GaAs: 1.4

Resistivity (W-cm)1016 (natural)

Density (gm/cm3)3.51

Thermal Expansion Coeff (K-1)0.8 x 10-6SiO2: 0.5 x 10-6

Refractive index2.41 @ 590 nmGlass: 1.4 - 1.8

Coeff. of Friction0.05 (dry)Teflon: 0.05

Source: Crystallume


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.


Molecular tools

Some other molecular tools


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


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