Lecture :Nanotechnology and Introduction'

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Lecture Nanotechnology and Introduction.
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• Details on nanomachines, biobots and
  virus/bacteria manipulation.
• How far have we come with nanomachines?
• CLE lecture series Spring 2005
• Dr. Heidi Fearn.
• http//chaos.fullerton.edu/heidi

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Contents
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• Why cant we just scale down machines, build the
  same mechanical parts only smaller? Stickiness,
  Brownian motion, surface to volume ratio, weird
  quantum forces.
• Where are we with respect to self assembly of
  machine parts? Drexlers dream machines. Grey Goo?
  Borg?
• Can we live forever, with nanobots in our blood?
• What about components for circuits and the
  promise of Terahertz CPUs in the future? (1000x
  faster than todays Pentium 4 chip, 3 or 4 GHz).

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Scale in Pictures. Powers of 10pictures taken
from http//www.powerof10.com/powers/poster.php
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Scale in Pictures. Powers of 10pictures taken
from http//www.powerof10.com/powers/poster.php
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1966 Film Rachel Welsh firing laser guns To
destroy a tumor in the brain.
Sorry- this wont work!!
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Viscosity at the nanoscaleSoft Machines by R.
L. A. Jones, Oxford U. Press.
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• Water, at the nanoscale, is not the free flowing
  liquid we are used to in the macroscale. Tiny
  objects in water are surrounded by a sticky
  viscous fluid- more like molasses,
• or treacle.
• The properties of fluids at the nanoscale become
  dominated by viscosity.
• In order to move forward, the volume of fluid we
  have to move out of the way, in a given time,
  varies like the velocity (v)
• times the area (a). Momentum (p) is mass
  times velocity.
• Mass is density (?) times volume. Inertial
  force is
• Force dp/dt ?a²v²
• Force of viscosity is F ?av, where ? is
  the liquid viscosity.
• The ratio gives Reynolds number Force/F
  ?av/ ?

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The lower the Reynolds number the more is the
effect of viscosity!
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• The ratio gives Reynolds number
• (Inertial Force)/(Viscous Force) ?av/
  ?
• As you can see for a smaller surface area (a),
  the ratio gets smaller and hence the effect of
  viscosity gets greater and will effect the motion
  of the small object more.
• A bacterium is a million times smaller than a
  human, so the bacterium feels water one million
  times more viscous than we do!

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Swimming on the nanoscale.Soft Machines by R.
A. L. JonesOxford Univ. Press.
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• In treacle or molasses, even an expert swimmer
  would expend a lot of energy
• moving backward and forward and not getting
  anywhere fast!
• A fast motion on the downward stroke gives us a
  sharp kick forward, but the return stroke in
  treacle, would simple move us back to where we
  started. Hence we dont move much at all
• So how do nanoscale biological objects get
  around? They do the TWIST- twisting movement
  seems most efficient.

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Can nanobots really fly?Soft Machines p58, by
Jones Oxford press.
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In the book by Crichton, our hero is being
chased by a swarm of solar powered man made tiny
robots, which you can hardly see, Individually,
with the naked eye. They are chasing him and can
move faster than he can run and they want to kill
him.
Now it turns out that there is a minimum size for
insects that are able to fly. The mechanics of
flight for little bugs is not that well
understood. It is easier to build an airplane
than to build a bee sized flying machine. The
smallest flying Insect (according to Jones) is a
parasitic wasp called dicopomorpha
Echmepterygis, which is about 1/10 of a mm long.
This is roughly the smallest size creature that
could possibly fly in our atmosphere. Pollen
grains are smaller, tens of microns, but they do
not have directed flight, they drift with the
breeze. Small objects experience a large air
viscosity, also you need the power to stay in the
air as well as to propel forward in a given
direction. Wings generate lift but also drag.
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Scanning probe microscopesAtomic Force
Microscopy
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Scanning tunneling microscope
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Brownian Motion
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• Objects under a microscope appear to be
  undergoing continuous random motion- jiggling.
• This is due to the constant bombardment of a
  microscopic object by atoms and molecules. Atoms
  and molecules are always in constant motion and
  they collide frequently with other larger
  objects, making the object, look like it is
  jiggling around by itself. You cannot see the
  atoms bombarding the larger object.
• The discrete nature of atoms means that is it
  possible for there to be an imbalance in the
  number of impacts from one direction, hence the
  object moves one way and then another in an
  apparent random motion or random walk.

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Oxygen atoms and diffusion coefficient.
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• Diffusion coeff. of oxygen in water is
• D18 x 10 6 cm²/s¹
• Roughly speaking, the time it takes a molecule
  to diffuse a given distance, L, is given by L² /
  D.
• An Oxygen molecule will move 10nm in a few
  milliseconds. It takes a minute to move a micron
  but for it to move a cm or so by diffusion alone
  would take 100 years!!
• Bigger molecules have smaller diffusion
  coeffs and move more slowly. A bacterium is
  small enough that Brownian movement alone will
  transport fuel and oxygen around inside it. It
  does not need a blood supply. Also Brownian
  motion brings the meals to the bacterium- meals
  on wheels in this case is meals by courtesy of
  Brownian motion.

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Stickiness at the NanoscaleSoft Machines by
Jones again.
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• In the nanoworld everything is sticky.
• Polished glass and metal objects stick together
  on the macroscale- the only reason large objects
  do not stick together is that they usually have
  hard rough surfaces.
• If a material is soft and flexible it is usually
  sticky- like cling film. The soft material
  conforms to the shape of the hard material it is
  sticking too.
• In an engine made of metal, we allow the
  lubricating oil to leak out, the engine will
  seize up and the surfaces will stick together- a
  significant surface area comes into contact.

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Force of Electromagnetism
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• At the nanoscale electromagnetism rules supreme.
• Gravity is negligible- too small to worry about.
• Electromagnetic bonds, bind everything, hence the
  stickiness.
• Surface to Volume ratio increases rapidly and
  things get smaller- properties of materials
  change.
• Molecular bonds are electromagnetic in origin. So
  are Van der Waals forces and Casimir effect
  forces although they are also quantum mechanical.

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Weird Quantum Forces at the Nanoscale
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• Van der Waals forces
• Casimir forces
• Kondo effect - spintronics.
• Wave-particle duality
• Interference effects
• Quantum mechanical tunneling

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Kondo Effect
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Self Assembling Machines? Not Yet!!
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• Do we have any kind of mechanical parts for man
  made nano-machines?
• We have many computer models care of Drexler and
  www.imm.org but these are just models and not
  real atomic constructions.

Bearing top differential gear bottom
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What parts have we designed and what have we made
that works?
c/o Drexler http//www.imm.org Computer
simulations only.
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So- can we live for ever with nanobots or MEMS in
our blood, repairing cells as soon as they start
to wear or falter??
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What about assemblers?http//www.imm.org
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No factory assemblers any time soon.
We might be better off looking for ways for the
atoms to assemble themselves via chemistry.
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Carbon Nanotubes to the rescue!
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We have semiconductor carbon nanotubes which can
be made into all the different types
of Transistors, gates and switches and
memory needed for todays chip architecture.
Chicken wire Atomic structure is twisted like the
cardboard of a toilet roll.
We have conductor type carbon nanotubes which can
be used for Connecting the chip bits and pieces
together. Chicken wire looks Straight- hexagons
of carbon atoms are parallel and evenly aligned.
We have no way at present to mass produce the
parts or the chips for commercial use. The parts
are made painstakingly one at a time. They have
not been put into a working circuit yet.
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Nano Circuits on the horizon.
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• Do we know how to build the needed circuit
  components? YES
• Do we have the materials to build them from? YES
• Can we mass produce these components and make
  the venture profitable? NOT YET.
• Do people really need computers and laptops that
  small ? YES WE LIKE TOYS.

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How does a carbon Nanotube switch work?
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Carbon Nanotubes Understanding Nanotechnology
Scientific American, Warner Books.Drexler
www.imm.org
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Space Elevator
climber
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ATP molecular motor
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Molecular switch and quantum dot for luminous
drug tagging
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The End
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• On Feb 28th for the LAST CLE talk, Lecture 4 On
  wetware, biobots and biological manipulation.
• GO TO http//chaos.fullerton.edu/heidi
• For references and power point lectures on
  nanotechnology.
• WE need to teach SOLID STATE PHYSICS!
• For band gaps and nanotubes .