Molecular Nanotechnology Ralph C. Merkle Principal Fellow, Zyvex

Nick Smith, Chairman House Subcommittee on Basic Research June 22, 1999 In Fiscal Year 1999, the federal government will spend approximately $230 million on nanotechnology research.

National Nanotechnology Initiative  Announced by Clinton at Caltech  Interagency (AFOSR, ARO, BMDO, DARPA, DOC, DOE, NASA, NIH, NIST, NSF, ONR, and NRL)  FY 2001: $497 million

Academic and Industry  Caltech’s MSC (1999 Feynman Prize), Rice CNST (Smalley), USC Lab for Molecular Robotics, etc  Private nonprofit (Foresight, IMM)  Private for profit (IBM, Zyvex)  And many more….

There is a growing sense in the scientific and technical community that we are about to enter a golden new era. Richard Smalley 1996 Nobel Prize, Chemistry

The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom. It is not an attempt to violate any laws; it is something, in principle, that can be done; but in practice, it has not been done because we are too big. Richard Feynman,

The book that laid out the technical argument for molecular nanotechnology: Nanosystems by K. Eric Drexler, Wiley 1992

Three historical trends in manufacturing  More flexible  More precise  Less expensive

The limit of these trends: nanotechnology  Fabricate most structures consistent with physical law  Get essentially every atom in the right place  Inexpensive (~10-50 cents/kilogram)

 Coal  Sand  Dirt, water and air  Diamonds  Computer chips  Grass It matters how atoms are arranged

Today’s manufacturing methods move atoms in statistical herds  Casting  Grinding  Welding  Sintering  Lithography

Possible arrangements of atoms. What we can make today (not to scale)

The goal: a healthy bite..

Core molecular manufacturing capabilities Today Products Overview of the development of molecular nanotechnology

Terminological caution “Nanotechnology” has been applied to almost any research where some dimension is less than a micron (1,000 nanometers) in size. Example: sub-micron optical lithography

Two more fundamental ideas  Self replication (for low cost) Self replication  Positional assembly (so molecular parts go where we want them to go) Positional assembly

Von Neumann architecture for a self replicating system Universal Computer Universal Constructor

Drexler’s architecture for an assembler Molecular computer Molecular constructor Positional deviceTip chemistry

Illustration of an assembler

The theoretical concept of machine duplication is well developed. There are several alternative strategies by which machine self-replication can be carried out in a practical engineering setting. Advanced Automation for Space Missions Proceedings of the 1980 NASA/ASEE Summer Study

A C program that prints out an 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);} For more information, see the Recursion Theorem:

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

C program 800 Von Neumann's universal constructor500,000 Internet worm (Robert Morris, Jr., 1988)500,000 Mycoplasma capricolum1,600,000 E. Coli9,278,442 Drexler's assembler100,000,000 Human6,400,000,000 NASA Lunar Manufacturing Facilityover 100,000,000,000 Complexity of self replicating systems (bits)

How cheap?  Potatoes, lumber, wheat and other agricultural products are examples of products made using a self replicating manufacturing base. Costs of roughly a dollar per pound are common.  Molecular manufacturing will make almost any product for a dollar per pound or less, independent of complexity. (Design costs, licensing costs, etc. not included)

How long?  The scientifically correct answer is: I don’t know  Trends in computer hardware suggest the 2010 to 2020 time frame  Of course, how long it takes depends on what we do

Developmental pathways  Scanning probe microscopy  Self assembly  Progressively smaller positional assembly  Hybrid approaches

Moving molecules with an SPM (Gimzewski et al.)

Self assembled DNA octahedron (Seeman)

DNA on an SPM tip (Lee et al.)

Buckytubes (Tough, well defined)

Buckytube glued to SPM tip (Dai et al.)

Building the tools to build the tools  Directly manufacturing a diamondoid assembler using existing techniques appears very difficult.  We’ll have to build intermediate systems able to build better systems able to build diamondoid assemblers.

If we can make whatever we want what do we want 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 10 9 (natural)10 11 (theoretical) Compressive strength (pascals)10 11 (natural)5 x (theoretical) Band gap (ev)5.5Si: 1.1 GaAs: 1.4 Resistivity (W-cm)10 16 (natural) Density (gm/cm3)3.51 Thermal Expansion Coeff (K-1)0.8 x 10-6SiO2: 0.5 x 10-6 Refractive 590 nmGlass: Coeff. of Friction0.05 (dry)Teflon: 0.05 Source: Crystallume

Strength of diamond  Diamond has a strength-to-weight ratio over 50 times that of steel or aluminium alloy  Structural (load bearing) mass can be reduced by about this factor  When combined with reduced cost, this will have a major impact on aerospace applications

A hydrocarbon bearing

Neon pump

A planetary gear

A proposal for a molecular positional device

Classical uncertainty σ:mean positional error k: restoring force k b : Boltzmann’s constant T:temperature

A numerical example of classical uncertainty σ:0.02 nm (0.2 Å) k: 10 N/m k b : 1.38 x J/K T:300 K

Born-Oppenheimer approximation  A carbon nucleus is more than 20,000 times as massive as an electron, so it will move much more slowly  Assume the atoms (nuclei) are fixed and unmoving, and then compute the electronic wave function  If the positions of the atoms are given by r 1, r 2,.... r N then the energy of the system is: E(r 1, r 2,.... r N )  This is fundamental to molecular mechanics

Quantum positional uncertainty in the ground state σ 2 :positional variance k: restoring force m: mass of particle ħ :Planck’s constant divided by 2 π

Quantum uncertainty in position  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  Nuclei are point masses  Electrons are in the ground state  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

Example: H 2 Internuclear distance Energy

Molecular mechanics  Internuclear distance for bonds  Angle (as in H 2 O)  Torsion (rotation about a bond, C 2 H 6  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 tools  Today, we make things at the molecular scale by stirring together molecular parts and cleverly arranging things so they spontaneously go somewhere useful.  In the future, we’ll have molecular “hands” that will let us put molecular parts exactly where we want them, vastly increasing the range of molecular structures that we can build.

Synthesis of diamond today: diamond CVD diamond CVD  Carbon: methane (ethane, acetylene...)  Hydrogen: H 2  Add energy, producing CH 3, H, etc.  Growth of a diamond film. The right chemistry, but little control over the site of reactions or exactly what is synthesized.

A hydrogen abstraction tool

Some other 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

The impact of nanotechnology depends on what’s being made  Computers, memory, displays  Space Exploration  Medicine  Military  Environment, Energy, etc.

Powerful computers  In the future we’ll pack more computing power into a sugar cube than the sum total of all the computer power that exists in the world today  We’ll be able to store more than bits in the same volume  Or more than a billion Pentiums operating in parallel  Powerful enough to run Windows 2015

Memory probe

Displays  Molecular machines smaller than a wavelength of light will let us build holographic displays that reconstruct the entire wave front of a light wave  It will be like looking through a window into another world  Covering walls, ceilings and floor would immerse us in another reality

Space  Launch vehicle structural mass will be reduced by about a factor of 50  Cost per pound for that structural mass will be under a dollar  Which will reduce the cost to low earth orbit by a factor 1,000 or more Nanotechnology/publications/1997/applicatio ns/

It costs less to launch less  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)

Swallowing the surgeon...it would be interesting in surgery if you could swallow the surgeon. You put the mechanical surgeon inside the blood vessel and it goes into the heart and “looks” around.... Other small machines might be permanently incorporated in the body to assist some inadequately-functioning organ. Richard P. Feynman, 1959 Nobel Prize for Physics, 1965

Nanomedicine Volume I  By Robert Freitas  Surveys medical applications of nanotechnology  Extensive technical analysis  Volume I (of three) published in 1999 

Mitochondrion 20 nm scale bar Ribosome Molecular computer (4-bit) + peripherals Molecular bearing

“Typical” cell Mitochondrion Molecular computer + peripherals

Disease and illness are caused largely by damage at the molecular and cellular level Today’s surgical tools are huge and imprecise in comparison

In the future, we will have fleets of surgical tools that are molecular both in size and precision. We will also have computers that are much smaller than a single cell with which to guide these tools.

Medical applications  Killing cancer cells, bacteria  Removing blockages  Providing oxygen(artificial red blood cell)  Adjusting other metabolites

A revolution in medicine  Today, loss of cell function results in cellular deterioration: function must be preserved  With medical nanodevices, passive structures can be repaired. Cell function can be restored provided cell structure can be inferred: structure must be preserved

Cryonics 37º C -196º C (77 Kelvins) Freeze Restore to health Time Temperature (many decades)

Clinical trials to evaluate cryonics  Select N subjects  Freeze 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?

Would you rather join: The control group? (no action required) or The experimental group? (see for info)

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,

Human impact on the environment depends on  Population  Living standards  Technology

Restoring the environment with nanotechnology  Low cost greenhouse agriculture  Low cost solar power  Pollution free manufacturing  The ultimate in recycling

Solar power and nanotechnology  The sunshine reaching the earth has almost 40,000 times more power than total world usage.  Nanotechnology will produce efficient, rugged solar cells and batteries at low cost.  Power costs will drop dramatically

Environmentally friendly manufacturing  Today’s manufacturing plants pollute because they use imprecise methods.  Nanotechnology is precise — it will produce only what it has been designed to produce.  An abundant source of carbon is the excess CO 2 in the air

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

The best way to predict the future is to invent it. Alan Kay