Nanotechnology
Gavin Lawes
Department of Physics and Astronomy
Earth-Moon distance
4x108 m
Length scales (Part I)
(courtesy NASA)
Person
2m
1010 m
105 m
Magnetic
nanoparticle
5x10-9 m
1m
Michigan width
2x105 m
Red blood cell
1x10-5 m
(courtesy Google)
(courtesy PBS)
10-5 m
10-10 m
Length scales (Part II)
10-1 m
10-3 m
Head of a pin
1,000,000 nm
Courtesy CSU Hayward
10-3 m=1 mm
Thickness of a human hair: 100,000 nm
Visible light
400 to 700 nm
10-5 m
10-6 m=1 mm=1 micron
10-7 m
10-9 m
10-9 m=1 nm
Distance between
atoms in a solid
~0.3 nm
Transistors
65 nm
(now 28 nm)
Courtesy Intel
Q: What is Nanotechnology?
Q: What is Nanotechnology?
A: Depends on who you ask.
Q: What is Nanotechnology?
Narrow
“Nanotechnology is the engineering of functional systems
at the molecular scale”
-Center for Responsible Nanotechnology
Broad
“Nanotechnology is the understanding and control of
matter at dimensions of roughly 1 to 100 nm.”
-National Nanotechnology Initiative
We will follow the broad definition for nanotechnology, since we
need to understand the properties of small objects before we can
build machines from them.
How can we see things on the nanoscale?
10-1 m
•The development of scanning 10-3 m
probe techniques (STM, AFM) in
1981 revolutionized imaging
nanoscale systems.
Optical
microscopy
10-5 m
10-7 m
Nanotechnology
10-9 m
Electron
microscopy
Scanning Electron Microscope
•Uses reflected electrons to image small objects.
Mite on a chip
Attogram (10-18 g) scale
Sandia National Laboratory
Courtesy H. Craighead, Cornell University
Transmission Electron Microscope
g-Fe2O3 nanoparticles
•Uses electrons passing
through sample to image
small objects
5 nm
Liver Cell
University of New England
TEM
Philips CM10
TEM image of Fe3O4 nanoparticle
8 nm
Scanning Tunneling Microscope
STM Tip
BiO planes in BSCCO
Courtesy Kiel University
Quantum Corral
Courtesy J.C.S. Davis, Cornell
Courtesy IBM
Atomic Force Microscope
•Images small objects by the
mechanical response of a cantilever.
Silicon atoms
AFM tip
4 nm
Pictures courtesy P. Hoffmann, WSU
What can nanotechnology do for us?
Biomedical
New drug delivery systems.
New imaging techniques.
Better sunscreens.
Materials Science
Stronger and lighter materials.
Combining properties on the nanoscale
Computers
Ultra-high density hard drives.
Smaller transistors.
New polishing methods using nanoparticle slurries.
Magnetic
nanoparticle
Why do we need nanotechnology for
these things?
1. Cells are a few microns in size, so nanometer sized objects can freely move
through cell walls, into the cell nucleus.
2. Nanoparticles have a very large surface area, making them useful for
applications relying on the interface between different materials.
3. Electronic components are already less than 100 nm; increasing their
performance will rely on working at smaller length scales.
4. The physical properties of materials at small length scales is very different
than in bulk.
How do you make nanotechnology?
Top-down approach
•Like making a statue of an elephant: start with a big block of marble, and chip
away everything that doesn’t look like an elephant.
Lithography
30 nm lines
Focused ion beam
90 nm lines
Courtesy IBM research
Courtesy C. Kruse, Bremen
Mask
Resist
Material
Expose resist to light using mask.
Chemically etch regions not
protected by the resist.
Remove portions of resist
not exposed to light.
Bottom-up approach
•Like making a statue of an elephant from lego, if the lego blocks were 1 nm across.
DNA
Xenon atoms positioned using STM
Courtesy NIH
Courtesy D. Eigler IBM
(Self-assembly)
DNA Tweezers
Courtesy B. Yurke, Bell Labs
Gold-polymer nanorods
Courtesy C. Mirkin, Northwestern
How do things change on the nanoscale?
Mechanical properties change
Silicon spur being broken
Courtesy J. Parpia, Cornell University
Electronic properties change
Carbon nanotubes
Courtesy UC Berkeley
Single electron transistor
Courtesy D. Ralph, Cornell University
Optical properties change
Medieval Stained Glass
CdSe Quantum (or Nano) Dots
Courtesy Iowa State
Courtesy NYTimes
Magnetic properties change
Iron oxide nanoparticles
Hard disk data sector
20 nm
Courtesy Dataclinic.co.uk
•The magnetization direction of magnetic nanoparticles can change spontaneously
at room temperature. This is bad for long-term magnetic storage.
Magnetic properties change
FC
M
TB
ZFC
H
Dynamical properties change
Pollen grains in water
Simulation of Brownian Motion
Courtesy P. Keyes, WSU
Courtesy P. Keyes, WSU
•At small length scales, even individual
collisions with water or air molecules can
be important.
Why does surface area matter for
nanotechnology?
A  4R
2
A 3

V R
4 3
V  R
3
At R=1 mm, A/V=3x103 m-1
At R=10 nm, A/V=3x108 m-1
Factor of 105 difference!
Air resistance
Fdrag  12 Cd air v2 A
Fdrag
Fgravity
Fgravity  mg  V g
alt.
v
Fdrag
A
~
V
Fdrag
A

~
m
V V
The relative importance of drag forces increase as the surface to volume ratio,
which becomes very large in nanoscale systems.
% of Au atoms near surface
Gold atoms are about 0.2 nm apart. What fraction of Au atoms are near the
surface (2 layers away) in a 2 mm dia. gold ball? 20 nm dia. gold ball?
at R=1 mm, 1.2x10-4 %
of atoms are near the
surface.
Vsurface
Vtotal
at R=10 nm, 12 % of
atoms are near the
surface.
4R 2 0.4nm 1.2nm


3
4
R
3 R
Surface loss mechanisms
Dissipative losses in small devices can be strongly affected by the
motion of atoms and molecules bonded to the surface.
Cantilever
•The dissipation in nanodevices can be
reduced by over a factor of 10 by
heating them to 1000 oC.
•This is important for removing
molecules attached to the surface.
Courtesy H. Craighead, Cornell University
What can we do with nanotechnology?
Damascus sabre steel contains nanotubes
Multiwalled carbon
nanotubes found in 17th
century sword.
10 nm
These are formed
during the synthesis
and may have produced
the very good
mechanical properties.
Carbon nanostructures may be used in devices
from nanotechweb.org
Carbon nanotube mechanical oscillator
Force sensitivity of 1 fN Hz-1/2
Nanostructured photovoltaics
Targeted drug delivery
Schematic diagram of a nanocomposite
FITC
NH2
NH2
NH2
NH2
Dextran
TAT Peptide
Nanoparticle delivery into cells
FITC alone
FITC +
nanoparticles
L. Runyan, V. Singh, G. Hillman
Summary
•Recent scientific developments have spurred nanotechnology
research.
•Things on small length scales often act very differently from
things at larger length scales.
•This can be used to develop new applications for nanotechnology,
but also leads to new types of problems to be addressed.
End
Atomic scale friction
Atomic scale friction
Commensurate surfaces
higher friction
A. Socoliuc et al., Science 313, 207 (2006)
Incommensurate surfaces
lower friction
Interfacial adhesion changes frictional
forces
Trailing clamp
Leading clamp
Inchworm actuator
Actuation Plate
Displacement
gauge
Courtesy A. Corwin, Sandia Labs
200 um
Suspension
spring
A. Corwin et al, APL 84, 2451 (2004)
Nanoscale friction
Laws of Friction
1. The force of friction is directly proportional to the applied load.
2. The force of friction is independent of the apparent area of contact.
3. Kinetic friction is independent of the sliding velocity.
NB: Both of these have the
same apparent area of contact,
but the real area of contact is
larger in the bottom case
(under a larger normal load).