1. Self
Assembly
July 22, 2009
Summer 2009 Nanotechnology Institute

2. Making Nanostructures: Nanomanufacturing
"Top down" versus "bottom up" methods
Lithography
Deposition
Etching
Machining
Chemical
Self-Assembly

3. What drives and governs self assembly?
As you view the following images you should consider the question:
What drives and governs self assembly?

4. Tobacco Mosaic Virus
wisc.edu
nih.gov

5. Gecko feet

6. Diatoms
sinancanan.net
priweb.org

7. Abalone

8. The Cell and Its Hierarchy
ebi.ac.uk

9. Self assembly at all scales? Whitesides et al. Science 295,
2418 (2002);

13. What drives self assembly?
Static assembly (thermodynamic free energy minimum) -- once formed it is stable
Dynamic assembly (kinetically formed, not necessarily thermodynamic minimum) -- not necessarily stable
Forces of chemical bonding (4)
covalent, ionic, van derWaals, hydrogen
Other forces (magnetic, electrostatic, fluidic, ...)
Polar/Nonpolar (hydrophobicity)
Shape (configurational)
Templates (guided self assembly)
Kinetic conditions (e.g., diffusion limited)

14. Excerpt from Letter of Benjamin Franklin to William Brownrigg (Nov
...At length being at Clapham, where there is, on the Common, a large Pond ... I fetched out a Cruet of Oil, and dropt a little of it on the Water. I saw it spread itself with surprising Swiftness upon the Surface ... the Oil tho' not more than a Tea Spoonful ... which spread amazingly, and extended itself gradually till it reached the Lee Side, making all that Quarter of the Pond, perhaps half an Acre, as smooth as a Looking Glass....
A nanofilm!

15. Langmuir Film of an amphiphilic molecule water hydrophobic end
e.g., steric acid
pressure
of an amphiphilic
molecule
monolayer film
water
hydrophilic end

16. Langmuir-Blodgett Film
solid
Must control movable
barrier to keep constant
pressure
multiple dips -
multiple layers
liquid

17. SAM: Self Assembled Monolayer
alkanethiol on gold (Au)
HS(CH2)nX
where X is the end group of the chain
–CH3, –OH, or –COOH
Longer alkanethiol molecules have greater thermodynamic stability
Review article: J.C. Love, et al., Chem. Rev. 2005, 105, 1103
(G. Whitesides group, Chem Dept, Harvard)

18. SAM: Self Assembled Monolayer
molecules
from solution
solid
Chemisorbed molecules
Stabilized by intermolecular van der Waals interaction

19. SAMs on Nanoparticles gold NP
There are now many configurations and uses of SAMs
imperfect packing
J.C. Love, et al., Chem. Rev. 2005, 105, 1103

20. Nanoparticle Monolayer Formed at a Liquid-Air Interface

21. Nanoparticle Monolayer Formation
toluene
Nature Materials MOVIE
Requirements:
rapid evaporation
excess dodecane present
attractive interation to liq-air interface and between particles

22. SELF ASSEMBLY with DIBLOCK COPOLYMERS
Block “B”
Block “A” PS
PMMA
~10 nm
Scale set by molecular size
Ordered Phases
10% A
30% A
50% A
70% A
90% A

23. Versatile, self-assembling, nanoscale lithographic system
CORE CONCEPT
FOR NANOFABRICATION
Deposition
Template
Etching
Mask
Nanoporous
Membrane
(physical or
electrochemical)
Remove polymer
block within cylinders
(expose and develop)
Versatile, self-assembling, nanoscale lithographic system

24. TEMPLATE CHARACTERIZATION
MW = 42,000
PS/PMMA
SAXS
SEM
100 cpp
Array Period = 24 nm
Pore Diameter = 14 nm

25. Improving Order: Guided Assembly in a Trench: Graphioepitaxy
side view
assemble here
UMass-Seagate
top
view

26. Nanomagnets in a Self-Assembled Polymer Mask
nanoporous template
1x1012 magnets/in2
Pulse reverse electrodeposition results in improved microcrystalline structure and improved magnetic properties (larger perpendicula magnetocrystalline anisotropy)
Data Storage...
...and More

27. Metal Nanorings Ferromagnetic cobalt rings as small as 15 nm OD
Extracted from a paper in preparation “Nanoscopic Metal Rings Fabricated Using a Self-Assembled Template” by Deepak Singh (Physics), Qijun Xiao (Physics), Robert Krotkov (Physics), Hongie Xiang (PSE), Ting Xu (PSE), Thomas Russell (PSE) and Mark Tuominen (Physics). In magnetic applications the nanoscopic rings are promising for data storage and spintronic applications because of their favored magnetic vortex state. The rings offer promise for new plasmonic and negative refractive index applications.
Ferromagnetic cobalt rings
as small as 15 nm OD

28. Kinetic Self-Assembly - by Breath Figures
Polystyrene Film
Mohan Srinivasarao, et al. Science 292, 79 (2001).

29. More Fabrication by Breath Figures
a, Breath-figure pattern obtained with pure polystyrene. b, Optical and c, confocal fluorescence microscope images of different areas of a sample obtained from solvent-casting a polystyrene film from chloroform with CdSe nanoparticles. Scale bars: 16 mum. The inset in c shows a fluorescence intensity scan along the line indicated.
UMass: Alexander Böker, Yao Lin, Kristen Chiapperini, Reina Horowitz, Mike Thompson, Vincent Carreon, Ting Xu, Clarissa Abetz, Habib Skaff, A. D. Dinsmore, Todd Emrick and Thomas P. Russell, Nature Materials 3, (2004)

30. Anodized Aluminum Oxide Templates
counter electrode
Nanoporous
aluminum
oxide (AAO)
~ 40 V
Aluminum I
(oxalic, sulfuric, or
phosphoric acid)
Anodization Acid Bath
Masuda, et al.
e.g., • Keller, et al., J. Electrochem. Soc. 100, 411 (1953)
• Masuda & Fukuda, Science 268, 1466 (1995)

31. Proposed AAO Growth Mechanism
Al2O3 E Al
Al3+
O2-
Density mismatch between Al and Al2O3
Some Al3+ goes to solution
Mechanical stress yields pore growth in uniform hexagonal array
Pore diameters of
~ nm possible
by choice of anodization
conditions
Figure adapted from
Jessensky, Müller, & Gösele, Appl. Phys. Lett. 72, 1173 (1998)

32. Improving AAO Order at Surface
SiC stamp
Aluminum
anodize
e.g., Masuda et al., Appl. Phys. Lett 71, 2770 (1997);
Choi, et al., J. Vac. Sci. Tech. B 21, 763 (2003)

33. Ni in Anodized Aluminum Oxide Template
SEM
MFM
Nielsch, et al. Appl. Phys. Lett. 79, 1360 (2001).

34. Large Scale Self-Assembly (Geological)
Giant's Causeway
(Northern Ireland)
Volcanic basalt cooled rapidly to form these (mostly) hexagonally shaped columns

35. Microfluidic Assembly
Application: RFID
Alien Technology
flow direction
Parts, having unique shape, are delivered via fluid flow to mating pockets on an assembly substrate.
Nanoscale Phase Separation
IBM "air gap" technology
Introducing nanoscale air pockets into the insulating material separating wires on a computer chip -- lowers the capacitance

36. Molecular Recognition ("lock and key" bonding)
hydrogen bonding
thymine (T) adenine (A)
guanine (G) cytosine (C)
biotin-avidin pair (site-specific binding)

37. Using Synthetic DNA for Designer Structures
Designer DNA molecules can be synthesized chemically, and allowed to assemble into a specific configuration of lowest energy.
Ned Seeman, NYU

38. Programmed DNA Folding to Make "DNA Origami"
P.W.K. Rothemund, Nature 440, 297 (2006)

39. Additional examples to amplify concepts
balls in a box
magnets
crystallization
Forces (non-directional or directional), shape, thermal agitation
Nanoscale self assembly
coffee stain
nanoparticle assembly by droplet
others