Self Assembly July 22, 2009 Summer 2009 Nanotechnology Institute

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

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

Tobacco Mosaic Virus wisc.edu nih.gov

Gecko feet

Diatoms sinancanan.net priweb.org

Abalone

The Cell and Its Hierarchy ebi.ac.uk

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

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)

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!

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

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

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)

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

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

Nanoparticle Monolayer Formed at a Liquid-Air Interface

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

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

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

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

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

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

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

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

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, 302 - 306 (2004)

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)

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 ~ 10-400 nm possible by choice of anodization conditions Figure adapted from Jessensky, Müller, & Gösele, Appl. Phys. Lett. 72, 1173 (1998)

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)

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

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

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

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

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

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

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