1. Department of Physics and Astronomy
Nanotechnology
Gavin Lawes
Department of Physics and Astronomy

2. Length scales (Part I) 1010 m 105 m 1 m 10-5 m 10-10 m
Earth-Moon distance
4x108 m
(courtesy NASA)
Person 2m
Magnetic nanoparticle
5x10-9 m
1010 m
105 m
1 m
10-5 m
10-10 m
Michigan width
2x105 m
(courtesy Google)
Red blood cell
1x10-5 m
(courtesy PBS)

3. Length scales (Part II)
10-1 m
Head of a pin
1,000,000 nm
10-3 m
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
Transistors
65 nm
(now 28 nm)
Distance between atoms in a solid
~0.3 nm
10-9 m
10-9 m=1 nm
Courtesy Intel

4. Q: What is Nanotechnology?

5. Q: What is Nanotechnology?
A: Depends on who you ask.

6. 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.

7. How can we see things on the nanoscale?
10-1 m
10-3 m
The development of scanning probe techniques (STM, AFM) in 1981 revolutionized imaging nanoscale systems.
Optical microscopy
10-5 m
Electron microscopy
10-7 m
Nanotechnology
10-9 m

8. 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

9. Transmission Electron Microscope
g-Fe2O3 nanoparticles
5 nm
Uses electrons passing through sample to image small objects
Liver Cell
University of New England
TEM
Philips CM10

10. TEM image of Fe3O4 nanoparticle
8 nm

11. Scanning Tunneling Microscope
STM Tip
BiO planes in BSCCO
Courtesy Kiel University
Quantum Corral
Courtesy J.C.S. Davis, Cornell
Courtesy IBM

12. Atomic Force Microscope
Images small objects by the mechanical response of a cantilever.
Silicon atoms
AFM tip
4 nm
Pictures courtesy P. Hoffmann, WSU

13. Magnetic nanoparticle
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

14. 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.

15. How do you make nanotechnology?

16. Top-down approach Focused ion beam Lithography
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.
Focused ion beam
Lithography
30 nm lines
90 nm lines
Courtesy C. Kruse, Bremen
Courtesy IBM research

17. 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.

18. Bottom-up approach Xenon atoms positioned using STM DNA
Like making a statue of an elephant from lego, if the lego blocks were 1 nm across.
Xenon atoms positioned using STM
DNA
Courtesy D. Eigler IBM
Courtesy NIH

19. (Self-assembly) DNA Tweezers Gold-polymer nanorods
Courtesy B. Yurke, Bell Labs
Courtesy C. Mirkin, Northwestern

20. How do things change on the nanoscale?

21. Mechanical properties change
Silicon spur being broken
Courtesy J. Parpia, Cornell University

22. Electronic properties change
Carbon nanotubes
Single electron transistor
Courtesy UC Berkeley
Courtesy D. Ralph, Cornell University

23. Optical properties change
Medieval Stained Glass
CdSe Quantum (or Nano) Dots
Courtesy Iowa State
Courtesy NYTimes

24. Magnetic properties change
Hard disk data sector
Iron oxide nanoparticles
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.

25. Magnetic properties changeFC
ZFC TB
Magnetic properties change

26. Dynamical properties change
Pollen grains in water
Simulation of Brownian Motion
Courtesy P. Keyes, WSU
At small length scales, even individual collisions with water or air molecules can be important.
Courtesy P. Keyes, WSU

27. Why does surface area matter for nanotechnology?
At R=1 mm, A/V=3x103 m-1
At R=10 nm, A/V=3x108 m-1
Factor of 105 difference!

28. Air resistance
alt. v
The relative importance of drag forces increase as the surface to volume ratio, which becomes very large in nanoscale systems.

29. % 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.
at R=10 nm, 12 % of atoms are near the surface.

30. 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

31. What can we do with nanotechnology?

32. Damascus sabre steel contains nanotubes
10 nm
Multiwalled carbon nanotubes found in 17th century sword.
These are formed during the synthesis and may have produced the very good mechanical properties.

33. Carbon nanostructures may be used in devices
from nanotechweb.org

34. Carbon nanotube mechanical oscillator
Force sensitivity of 1 fN Hz-1/2

35. Nanostructured photovoltaics

36. Targeted drug delivery

37. Schematic diagram of a nanocomposite
FITC
TAT Peptide
NH2
Dextran

38. Nanoparticle delivery into cells
FITC alone
FITC + nanoparticles
L. Runyan, V. Singh, G. Hillman

39. 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.

40. End

43. Atomic scale friction Atomic scale friction Commensurate surfaces
higher friction
A. Socoliuc et al., Science 313, 207 (2006)
Incommensurate surfaces
lower friction

44. Interfacial adhesion changes frictional forces
Trailing clamp
Leading clamp
Inchworm actuator
Actuation Plate
Displacement
gauge
200 um
Suspension
spring
Courtesy A. Corwin, Sandia Labs
A. Corwin et al, APL 84, 2451 (2004)

45. 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).