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Nanotechnology:basic concepts and potential applications
Ralph C. Merkle, Ph.D.
Principal Fellow
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The overheads (in PowerPoint) are available on the web at:
http://www.zyvex.com/nanotech/talks/ppt/
Berkeley 010505.ppt
Slides on web
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Ninth Foresight Conferenceon Molecular Nanotechnology
November 9-11, 2001Santa Clara, CaliforniaIntroductory tutorial November 8
www.foresight.org/Conferences/MNT9/
Foresight
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Foresight
www.foresight.org/SrAssoc/
www.nanodot.org
Gatherings
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Health, wealth and atoms
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Arranging atoms
• Diversity• Precision• Cost
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Richard Feynman,1959
There’s plenty of roomat the bottom
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Eric Drexler, 1992
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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
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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
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Arrangements of atoms
.
Today
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The goal
.
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• 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
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.
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
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. What we can make today(not to scale)
But molecular manufacturing systems are not “close” to what we can make today.
MolecularManufacturing
New technologies
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• 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
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Core molecularmanufacturingcapabilities
Today ProductsProducts
Products
Products
Products
Products
Products
Products
Products
ProductsProducts
Products
Products
ProductsProducts
Products
Products
Products
Products
Products
Products
ProductsProducts
Products
Products
Overview
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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
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• Manufacturing is about moving atoms
• Molecular mechanics studies the motions of atoms
• Molecular mechanics is based on the Born-Oppenheimer approximation
Molecular mechanics
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The carbon nucleus has a mass over 20,000 times that of the electron
• Moves slower
• Positional uncertainty smaller
Born-Oppenheimer
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σ2: positional variance
k: restoring force
m: mass of particle
ħ: Planck’s constant divided by 2π
km22
Quantum uncertainty
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• 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
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• 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
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Internuclear distance
Ene
rgy
Hydrogen molecule: H2
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• 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
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• 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
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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
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Hydrocarbon bearing
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Hydrocarbon universal joint
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Rotary to linear
NASA Ames
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Bucky gears
NASA Ames
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Bearing
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Planetary gear
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Neon pump
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Fine motion controller
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Positional assembly
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Stewart platform
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kTkb2
σ: mean positional error k: restoring forcekb: Boltzmann’s constantT: temperature
Thermal noise
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kTkb2
σ: 0.02 nm (0.2 Å) k: 10 N/mkb: 1.38 x 10-23 J/KT: 300 K
Thermal noise
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3
4
4
3k
L
Er
E: Young’s modulusk: transverse stiffnessr: radiusL: length
Stiffness
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3
4
4
3k
L
Er
E: 1012 N/m2
k: 10 N/mr: 8 nmL: 100 nm
Stiffness
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Gimzewski et al.
Experimental work
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H. J. Lee and W. Ho, SCIENCE 286, p. 1719, NOVEMBER 1999
Experimental work
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Saw-Wai Hla et al., Physical Review Letters 85, 2777-2780, September 25 2000
Manipulation and bond formation by STM
I I
Experimental work
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Buckytubes
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Experimental work
Nadrian Seeman’struncated octahedron from DNA
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• Stiff struts• Adjustable length
Pathways
Self assembly ofa positional device
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ABCABCABCABCABCABCABCABCABCABCABCABC a a a a | | | | x x x x
XYZXYZXYZXYZXYZXYZXYZXYZXYZXYZXYZXYZ
a | x
joins the two struts
Sliding struts
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ABCABCABCABCABCABCABCABCABCABCABCABC a c a ca c a |/ |/ | / | xy xy x y x
XYZXYZXYZXYZXYZXYZXYZXYZXYZXYZXYZXYZ
a | x join the two struts
c | yand
Sliding struts
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ABCABCABCABCABCABCABCABCABCABCABCABC c c c c | | | | y y y y
XYZXYZXYZXYZXYZXYZXYZXYZXYZXYZXYZXYZ
Joins the two struts, which have nowmoved over one unit.
c | y
Cycling through a-x, c-y and b-z produces controlled relative motion of the two struts.
Sliding struts
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Self replication
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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
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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
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• 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
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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
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Print the following statement twice, the second time in quotes:
“Print the following statement twice, the second time in quotes:”
English translation:
Self replication
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The Von Neumann architecture
UniversalComputer
UniversalConstructor
http://www.zyvex.com/nanotech/vonNeumann.html
Self replication
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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
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The Von Neumann architecture
http://www.zyvex.com/nanotech/vonNeumann.html
Manufacturingelement
Newmanufacturingelement
Instructions
Self replication
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The Von Neumann architecture
http://www.zyvex.com/nanotech/vonNeumann.html
Instructions(tape)
Read head
Manufacturingelement
Newmanufacturingelement
Self replication
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Replicating bacterium
DNA
DNA Polymerase
Self replication
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http://www.foresight.org/UTF/Unbound_LBW/chapt_6.html
Drexler’s proposal for an assembler
Self replication
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http://www.zyvex.com/nanotech/selfRep.html
Macroscopiccomputer
Molecularconstructor
Molecularconstructor
Molecularconstructor
Broadcast architecture
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Broadcast architecture
Some broadcast methods:
Pressure (acoustic)Electromagnetic (light, radio)Chemical diffusionElectrical
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• 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
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Compressed gas
External gas
Actuator(under tension)
Pressure actuated device
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• 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
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• 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
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Advantages of broadcast architecture
• Smaller and simpler: no instruction storage, simplified instruction decode
• Easily redirected to manufacture valuable products
• Inherently safe
Broadcast replication
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Compressed neon
Approximate dimensions:1,000 nm length100 nm radius
http://www.zyvex.com/nanotech/casing.html
HC assembler
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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
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• 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
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• 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
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• 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
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• 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
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• 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
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Binding sites
HC assembler
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Freitas, adapted from Drexler
HC assembler
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Freitas, adapted from Drexler
HC assembler
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Subsystems• Casing• Binding sites (3)• Pistons (2)• Demultiplexor• Positional device• Tool synthesis• Zero residue
HC assembler
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Design and modeling of HC assembler feasible today
• Speed development
• Explore alternative designs
• Clearer target
• Clearer picture of capabilities
Assembler design project
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Making diamond today
Illustration courtesy of P1 Diamond Inc.
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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
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Hydrogen abstraction tool
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Other molecular tools
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C2 deposition
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Carbene insertion
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Micro rotation
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Exponential assembly
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• 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
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Convergent assembly
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Convergent assembly
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Convergent assembly
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Convergent assembly
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• 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
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• 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
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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
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• 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
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• 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
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• 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
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The impactof a new manufacturing technologydepends on what you make
Impact
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• 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
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• 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
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• 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
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• 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
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Mitochondrion~1-2 by 0.1-0.5 microns
Size of a robotic arm~100 nanometers
Impact
8-bit computer
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“Typical” cell: ~20 microns
MitochondrionSize of a robotic
arm ~100 nanometers
Impact
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Mitochondrion
Molecular computer + peripherals
“Typical” cell
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Remove infections
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Clear obstructions
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Respirocytes
http://www.foresight.org/Nanomedicine/Respirocytes.html
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• ATP, other metabolites
• Na+, K+, Cl-, Ca++, other ions
• Neurotransmitters, hormones, signaling molecules
• Antibodies, immune system modulators
• Medications
• etc.
Release/absorb
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Correcting DNA
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• 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
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• 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
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Liquid nitrogen
Time
Tem
pera
ture
Cryonics
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• 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
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It works It doesn't
Experimental groupwww.alcor.org
A very long andhealthy life
Die, lose lifeinsurance
Control group Die
Die
Payoff matrix
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“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
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“Everyone who has died and told me about it has said it’s terrific!”
Shirley MacLaine
122
• 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
Space
http://science.nas.nasa.gov/Groups/Nanotechnology/publications/1997/applications/
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• 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)
Space
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• 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
Space
K. Eric Drexler, Journal of the British Interplanetary Society,V 45, No 10, pp 401-405 (1992).Molecular manufacturing for space systems: an overview
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• 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
Space
K. Eric Drexler, Journal of the British Interplanetary Society,V 45, No 10, pp 401-405 (1992).Molecular manufacturing for space systems: an overview
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O’Neill Colonies
Dyson spheres
Skyhooks
Max population of solar system
Space
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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
128
• 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
129
Human impacton the environment
• Population• Living standards• Technology
The environment
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• Greenhouse agriculture/hydroponics• Solar power• Pollution free manufacturing
The environment
Reducing human impacton the environment
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• 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?
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Nanotechnology offers ... possibilities for health, wealth, and capabilities beyond most past imaginings.
K. Eric Drexler
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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
135
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
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137
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• 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
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20 nm scale bar
Ribosome
Molecular computer(4-bit) + peripherals
Molecular bearing
Mitochondrion