Whither nanotechnology
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Whither nanotechnology?. Ralph C. Merkle Distinguished Professor of Computing Georgia Tech College of Computing. Web pages. www.foresight.org. www.zyvex.com/nano. www.nano.gov. Health, wealth and atoms. Arranging atoms. Flexibility Precision Cost. Richard Feynman,1959.

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Whither nanotechnology?

Ralph C. Merkle

Distinguished Professor of Computing

Georgia Tech College of Computing


Web pages

www.foresight.org

www.zyvex.com/nano

www.nano.gov


Health, wealth and atoms


Arranging atoms

  • Flexibility

  • Precision

  • Cost


Richard Feynman,1959

There’s plenty of room

at the bottom


1980’s, 1990’s

Experiment and theory

First STM

By Binnig and Rohrer


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


The goal

Arrangements of atoms

.

Today


The goal

The goal

.


Positional assembly


Experimental

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


Theoretical


Molecular mechanics

  • Manufacturing is about moving atoms

  • Molecular mechanics studies the motions of atoms

  • Molecular mechanics is based on the Born-Oppenheimer approximation


Born-Oppenheimer

The carbon nucleus has a mass over 20,000 times that of the electron

  • Moves slower

  • Positional uncertainty smaller


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 don’t even have to compute the electronic structure


Hydrogen molecule: H2

Energy

Internuclear distance


Hydrocarbon machines


Molecular machines


Theoretical


Thermal noise

σ:mean positional error

k: restoring force

kb: Boltzmann’s constant

T:temperature


Thermal noise

σ:0.02 nm (0.2 Å)

k: 10 N/m

kb: 1.38 x 10-23 J/K

T:300 K


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


Making diamond today

Illustration courtesy of P1 Diamond Inc.


Hydrogen abstraction tool


Other molecular tools


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, Nanotechnology8 (1997) pages 149-162.

  • Theoretical studies of reactions on diamond surfaces, by S.P. Walch and R.C. Merkle, Nanotechnology9 (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.


Self replication

A redwood tree

(sequoia sempervirens)

112 meters tall

Redwood National Park

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


Self replication

The Von Neumann architecture

Universal

Computer

Universal

Constructor

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


Self replication

Drexler’s proposal for an assembler

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


Exponential assembly


Convergent assembly


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


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)


Impact

The impact

of a new manufacturing technology

depends on what you make


Impact

Powerful Computers

  • 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 1021 bits in the same volume

  • Almost a billion Pentiums in parallel


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, ...


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/


Impact

Size of a robotic arm

~100 nanometers

8-bit computer

Mitochondrion

~1-2 by 0.1-0.5 microns


Scale

Mitochondrion

Size of a robotic arm ~100 nanometers

8-bit computer

“Typical” cell: ~20 microns


Provide oxygen


Digest bacteria


Digest bacteria


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


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


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


How long?

  • 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


Research objectives

Goals

  • Mechanosynthesis

    H abstraction, Carbene insertion, …

  • System design

    assemblers, robotic arms, …


Nanotechnology offers ... possibilities for health, wealth, and capabilities beyond most past imaginings.

K. Eric Drexler


Quantum uncertainty

σ2:positional variance

k: restoring force

m: mass of particle

ħ:Planck’s constant divided by 2π


Quantum uncertainty

  • 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


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


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


Buckyballs


Buckytubes

Fullerenes

SWNT

MWNT

Chirality

Buckminsterfullerenes


Buckytubes

What is “chirality?”


Molecular

constructor

Molecular

constructor

Molecular

constructor

Broadcast architecture

Macroscopic

computer

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


Nanopores

Illustration from Harvard Nanopore Group


Millipede

Illustration from IBM Zurich


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Minimal assembler


System designs

System

Sub-system

Sub-system

Sub-system

part

part

part

part

part

part


System designs

Why don’t we have more system designs?

Development times are 10+ years

Planning horizons are usually 10- years

Research funding focused on “science”

FUD


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


Stiffness

E:Young’s modulus

k: transverse stiffness

r: radius

L:length


Stiffness

E:1012 N/m2

k: 10 N/m

r: 8 nm

L:100 nm


Convergent assembly


Convergent assembly


Convergent assembly


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


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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