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Self Assembly

Self Assembly. July 22, 2009. Summer 2009 Nanotechnology Institute. Lithography Deposition Etching Machining. Chemical Self-Assembly. Making Nanostructures: Nanomanufacturing. "Top down" versus " bottom up" methods. What drives and governs self assembly?.

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Self Assembly

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

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

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

  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);

  10. 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)

  11. Excerpt from Letter of Benjamin Franklin to William Brownrigg (Nov. 7, 1773) ...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!

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

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

  14. 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)

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

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

  17. Nanoparticle Monolayer Formed at a Liquid-Air Interface

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

  19. ~10 nm SELF ASSEMBLY with DIBLOCK COPOLYMERS Block “B” Block “A” PS PMMA Scale set by molecular size Ordered Phases 10% A 30% A 50% A 70% A 90% A

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

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

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

  23. Nanomagnets in a Self-Assembled Polymer Mask nanoporous template 1x1012 magnets/in2 Data Storage... ...and More

  24. Metal Nanorings Ferromagnetic cobalt rings as small as 15 nm OD

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

  26. 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)

  27. 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)

  28. Al2O3 Al3+ O2- E Al Proposed AAO Growth Mechanism • 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)

  29. 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)

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

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

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

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

  34. 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

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

  36. 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

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