2 Nanotechnology: basic concepts and potential applications Ralph C. Merkle, Ph.D. Principal Fellow.

transcript

Nanotechnology:basic concepts and potential applications

Ralph C. Merkle, Ph.D.

Principal Fellow

The overheads (in PowerPoint) are available on the web at:

http://www.zyvex.com/nanotech/talks/ppt/

Berkeley 010505.ppt

Slides on web

Ninth Foresight Conferenceon Molecular Nanotechnology

November 9-11, 2001Santa Clara, CaliforniaIntroductory tutorial November 8

www.foresight.org/Conferences/MNT9/

Foresight

www.foresight.org/SrAssoc/

www.nanodot.org

Gatherings

Health, wealth and atoms

Arranging atoms

• Diversity• Precision• Cost

Richard Feynman,1959

There’s plenty of roomat the bottom

Eric Drexler, 1992

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 term “nanotechnology” is very popular.

Researchers tend to define the term to include their own work. Definitions abound.

A more specific term:

“molecular nanotechnology”

Terminology

Arrangements of atoms

The goal

• Consider what has been done, and improve on it.

• Design systems de novo based purely on known physical law, then figure out how to make them.

New technologies

What we can make today(not to scale)

If the target is “close” to what we can make, the evolutionary method can be quite effective.

Target

New technologies

. What we can make today(not to scale)

But molecular manufacturing systems are not “close” to what we can make today.

MolecularManufacturing

New technologies

• Backward chaining (Eric Drexler)

• Horizon mission methodology (John Anderson)

• Retrosynthetic analysis (Elias J. Corey)

• Shortest path and other search algorithms in computer science

• “Meet in the middle” attacks in cryptography

Working backwards

Core molecularmanufacturingcapabilities

Today ProductsProducts

Products

ProductsProducts

Products

ProductsProducts

Products

ProductsProducts

Products

Overview

Length meter mm 0.001

Area meter2 mm2 0.000001

Volume meter3 mm3 0.000000001

Mass kilogram g 0.000000001

Time second ms 0.001

Speed m/s mm/ms 1

Scaling laws

Chapter 2 of Nanosystems

• Manufacturing is about moving atoms

• Molecular mechanics studies the motions of atoms

• Molecular mechanics is based on the Born-Oppenheimer approximation

Molecular mechanics

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

• Moves slower

• Positional uncertainty smaller

Born-Oppenheimer

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

Quantum uncertainty

• 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

Internuclear distance

Hydrogen molecule: H2

• 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

• 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

Property Diamond’s value Comments

Chemical reactivity Extremely lowHardness (kg/mm2) 9000 CBN: 4500 SiC: 4000Thermal conductivity (W/cm-K) 20 Ag: 4.3 Cu: 4.0Tensile 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: 1.4Resistivity (W-cm) 1016 (natural)Density (gm/cm3) 3.51Thermal Expansion Coeff (K-1) 0.8 x 10-6 SiO2: 0.5 x 10-6

Refractive index 2.41 @ 590 nm Glass: 1.4 - 1.8Coeff. of Friction 0.05 (dry) Teflon: 0.05

Source: Crystallume

Diamond physical properties

What to make

Hydrocarbon bearing

Hydrocarbon universal joint

Rotary to linear

NASA Ames

Bucky gears

NASA Ames

Bearing

Planetary gear

Neon pump

Fine motion controller

Positional assembly

Stewart platform

σ: mean positional error k: restoring forcekb: Boltzmann’s constantT: temperature

Thermal noise

σ: 0.02 nm (0.2 Å) k: 10 N/mkb: 1.38 x 10-23 J/KT: 300 K

Thermal noise

E: Young’s modulusk: transverse stiffnessr: radiusL: length

Stiffness

E: 1012 N/m2

k: 10 N/mr: 8 nmL: 100 nm

Stiffness

Gimzewski et al.

Experimental work

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

Experimental work

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

Manipulation and bond formation by STM

Experimental work

Buckytubes

Experimental work

Nadrian Seeman’struncated octahedron from DNA

• Stiff struts• Adjustable length

Pathways

Self assembly ofa positional device

ABCABCABCABCABCABCABCABCABCABCABCABC a a a a | | | | x x x x

XYZXYZXYZXYZXYZXYZXYZXYZXYZXYZXYZXYZ

joins the two struts

Sliding struts

ABCABCABCABCABCABCABCABCABCABCABCABC a c a ca c a |/ |/ | / | xy xy x y x

a | x join the two struts

c | yand

Sliding struts

ABCABCABCABCABCABCABCABCABCABCABCABC c c c c | | | | y y y y

Joins the two struts, which have nowmoved over one unit.

Cycling through a-x, c-y and b-z produces controlled relative motion of the two struts.

Sliding struts

Self replication

Complexity (bits)

• Von Neumann's constructor 500,000

• Mycoplasma genitalia 1,160,140

• Drexler's assembler 100,000,000

• Human 6,400,000,000

• NASA over 100,000,000,000

There are nine and sixty ways

of constructing tribal lays,

And every single one of them

is right.

Rudyard Kipling

There are many ways to make a replicating system

Replication

• Von Neumann architecture• Bacterial self replication• Drexler’s original proposal for an assembler• Simplified HydroCarbon (HC) assembler• Exponential assembly• Convergent assembly• And many more…

There are many ways to make a replicating system

Replication

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);}

A C program that prints outan exact copy of itself

Self replication

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

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

English translation:

Self replication

The Von Neumann architecture

UniversalComputer

UniversalConstructor

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

Manufacturingelement

Newmanufacturingelement

Instructions

Self replication

Instructions(tape)

Read head

Manufacturingelement

Newmanufacturingelement

Self replication

Replicating bacterium

DNA Polymerase

Self replication

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

Drexler’s proposal for an assembler

Self replication

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

Macroscopiccomputer

Molecularconstructor

Broadcast architecture

Some broadcast methods:

Pressure (acoustic)Electromagnetic (light, radio)Chemical diffusionElectrical

• Can provide both power and control

• Multi-megahertz operation

• Moderate pressure (P ~ one atmosphere) can be reliably detected with small pressure actuated pistons

• Feasible designs

Acoustic broadcast

Compressed gas

External gas

Actuator(under tension)

Pressure actuated device

• External pistons to detect pressure changes

• Two pistons can drive a demultiplexor, which in turn drives tens of signal lines

• Polyyne (carbyne) rods in buckytube sheaths is adequate to convey force (derailleur cable mechanism)

Piston design issues

• 12 nm radius by 20 nm length for a volume of about 9,000 nm3

• 105 Pa (~ one atmosphere) results in P V ~ 10-18 Joules ~ 200 kT at room temperature (high reliability)

• Force of ~45 piconewtons

Piston design issues

Advantages of broadcast architecture

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

• Easily redirected to manufacture valuable products

• Inherently safe

Broadcast replication

Compressed neon

Approximate dimensions:1,000 nm length100 nm radius

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

HC assembler

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)

Broadcast replication

• Well studied, robust

• Warning: synthesis of this casing will not use anything resembling current methods. Bucky tubes are well understood and well studied, simplifying design.

Buckytubes as casings

• An assembler manufactures two new assemblers inside its casing

• The casings of the new assemblers are rolled up during manufacture

• The original assembler releases the new assemblers by releasing the casing from the manufacturing component

Replication

• Compressed neon to maintain shape

• Pressure too low results in collapse

• Pressure too high bursts casing

• Pressures in the range of several tens of atmospheres should work quite well

Casing shape

• Acetone (solvent)• Butadiyne (C4H2, diacetylene: source of

carbon and hydrogen)• Neon (inert, provides internal pressure)• “Vitamin” (transition metal catalyst

such as platinum; silicon; tin)

http://nano.xerox.com/nanotech/hydroCarbonMetabolism.html

Feedstock

• A set of synthetic pathways that permits construction of all molecular tools from the feedstock.

• Can’t “go downhill,” must be able to make a new complete set of molecular tools while preserving the original set.

• http://www.zyvex.com/nanotech/

hydroCarbonMetabolism.html

(about two dozen reactions)

Parts closure

Binding sites

HC assembler

Freitas, adapted from Drexler

HC assembler

Freitas, adapted from Drexler

HC assembler

Subsystems• Casing• Binding sites (3)• Pistons (2)• Demultiplexor• Positional device• Tool synthesis• Zero residue

HC assembler

Design and modeling of HC assembler feasible today

• Speed development

• Explore alternative designs

• Clearer target

• Clearer picture of capabilities

Assembler design project

Making diamond today

Illustration courtesy of P1 Diamond Inc.

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

Molecular tools

Hydrogen abstraction tool

Other molecular tools

C2 deposition

Carbene insertion

Micro rotation

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

Exponential assembly

Convergent assembly

• 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

Take home message: the diversity of replicating systems is enormous

Replication

• Potatoes, lumber, wheat and other agricultural products have costs of roughly a dollar per pound.

• Molecular manufacturing will make almost any product for a dollar per pound or less, independent of complexity. (Design costs, licensing costs, etc. not included)

Replication

Take home message: and manufacturing costs will be very low

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

• 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)

Popular misconceptions:replicating systems must

Replication

• 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

Misconceptions are harmful

Replication

• Development and analysis of more replicating architectures

• Systematic study of existing proposals• Education of the scientific community and

the general public

What is needed

Replication

The impactof a new manufacturing technologydepends on what you make

Impact

• 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

Powerful Computers

Impact

• 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

• Disease and ill health are caused largely by damage at the molecular and cellular level

• Today’s surgical tools are huge and imprecise in comparison

Impact

Nanomedicine

• In the future, we will have fleets of surgical tools that are molecular both in size and precision.

• We will also have computers much smaller than a single cell to guide those tools.

Impact

Nanomedicine

Mitochondrion~1-2 by 0.1-0.5 microns

Size of a robotic arm~100 nanometers

Impact

8-bit computer

“Typical” cell: ~20 microns

MitochondrionSize of a robotic

arm ~100 nanometers

Impact

Mitochondrion

Molecular computer + peripherals

“Typical” cell

Remove infections

Clear obstructions

Respirocytes

http://www.foresight.org/Nanomedicine/Respirocytes.html

• ATP, other metabolites

• Na+, K+, Cl-, Ca++, other ions

• Neurotransmitters, hormones, signaling molecules

• Antibodies, immune system modulators

• Medications

• etc.

Release/absorb

Correcting DNA

• Nanosensors, nanoscale scanning

• Power (fuel cells, other methods)

• Communication

• Navigation (location within the body)

• Manipulation and locomotion

• Computation

• http://www.foresight.org/Nanomedicine

Nanomedicine Volume I

• Today, loss of cell function results in cellular deterioration:

function must be preserved

• With medical nanodevices, passive structures can be repaired:

structure must be preserved

A revolution in medicine

Liquid nitrogen

Cryonics

• Select N subjects

• Vitrify them

• Wait 100 years

• See if the medical technology of 2100 can indeed revive them

But what do we tell those who don’t expect to live long enough to see the results?

Clinical trials

It works It doesn't

Experimental groupwww.alcor.org

A very long andhealthy life

Die, lose lifeinsurance

Control group Die

Payoff matrix

“Thus, like so much else in medicine, cryonics, once considered on the outer edge, is moving rapidly closer to reality”

ABC News World News Tonight, Feb 8th

“…[medical] advances are giving new credibility to cryonics.”

KRON 4 News, NightBeat, May 3, 2001

Public perception

“Everyone who has died and told me about it has said it’s terrific!”

Shirley MacLaine

• Launch vehicle structural mass could be reduced by about a factor of 50

• Cost per pound for that structural mass can be under a dollar

• Which will reduce the cost to low earth orbit by a factor of better than 1,000

http://science.nas.nasa.gov/Groups/Nanotechnology/publications/1997/applications/

• Light weight computers and sensors will reduce total payload mass for the same functionality

• Recycling of waste will reduce payload mass, particularly for long flights and permanent facilities (space stations, colonies)

• 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

• Solar electric ion drive

• Thin (tens of nm) aluminum reflectors concentrate light

• Arrays of small ion thrusters

• 250,000 m/s exhaust velocity

• Acceleration of 0.8 m/s

• Tour the solar system in a few months

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

O’Neill Colonies

Dyson spheres

Skyhooks

Max population of solar system

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

http://nano.xerox.com/nanotech/nano4/jeremiahPaper.html

Weapons

Admiral David E. Jeremiah, USN (Ret)

Former Vice Chairman, Joint Chiefs of Staff

November 9, 1995

• New technologies, new weapons• At least one decade and possibly a few

decades away• Public debate has begun• Research into defensive systems is

essential

Gray goo, gray dust, …

Weapons

Human impacton the environment

• Population• Living standards• Technology

The environment

• Greenhouse agriculture/hydroponics• Solar power• Pollution free manufacturing

The environment

Reducing human impacton the environment

• The scientifically correct answer is I don’t know

• Trends in computer hardware suggest early in this century — perhaps in the 2010 to 2020 time frame

• Of course, how long it takes depends on what we do

How long?

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

K. Eric Drexler

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

Positional assembly

• The sunshine reaching the earth has almost 40,000 times more power than total world usage.

• Molecular manufacturing will produce efficient, rugged solar cells and batteries at low cost.

• Power costs will drop dramatically

Energy

20 nm scale bar

Ribosome

Molecular computer(4-bit) + peripherals

Molecular bearing

Mitochondrion

2 Nanotechnology: basic concepts and potential applications Ralph C. Merkle, Ph.D. Principal Fellow.

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