self assembly nanoscience education institute. making nanostructures: nanomanufacturing "top...

Self Assembly

Nanoscience Education Institute

Making Nanostructures: Nanomanufacturing

"Top down" versus "bottom up" methods

•Lithography•Deposition•Etching•Machining

•Chemical•Self-Assembly

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....

First a case you already know: The nanofilm

Franklin made this observation, but did not determine the thickness.

• The first person to make worthwhile, reproducible measurements on monolayers was Agnes Pockels who lived in Braunschweig, Germany. Agnes Pockels was the original housewife superstar. She performed her first experiments on monolayers in her kitchen in her home, starting in about 1882. She used a tin tray as the water container and a small disk suspended from a balance with a slide weight to measure the surface tension of the water.

• By contaminating the water surfaces with different materials, Pockels created monolayers and observed their properties when confining the water surfaces to various areas using waxed tin strips. Pockels observed that the surface tension of a water surface varies with its size and depends on the type of contamination.

• She sent an account of her work to Lord Rayleigh, who recommended its publication in the journal Nature. Lord Rayleigh had a similar interest in the science of interfaces and was inspired by Pockels to make his own experiments, from which he concluded that these layers were just a single molecule thick.

Agnes Pockels

Langmuir-Blodgett Film

pressuree.g., steric acid

monolayer filmwater

hydrophilic end

hydrophobic end

of an amphiphilicmolecule

The people behind the researchIrving Langmuir Katharine Burr Blodgett

• Nobel prize in chemistry for his work in surface chemistry

• First woman to earn a PhD in Physics from Cambridge University

Performed their research at General Electric in Schenectady, New York

Langmuir-Blodgett Film Transferred to a Solid Surface

Must control movablebarrier to keep constantpressure

multiple dips -multiple layers

solid

liquid

What drives and governs self assembly?

As you view the following images you should consider

the question:

Tobacco Mosaic Virus

wisc.edu

nih.gov

Diatoms

priweb.org

sinancanan.net

Abalone

The Cell and Its Hierarchy

ebi.ac.uk

Gecko feet

Publicity: http://www.sciencedaily.com/releases/2012/01/120125101950.htm

Scorpion Armor

Original article: http://dx.doi.org/10.1021/la203942r

The scorpion a special grooved shield to protect itself against scratches from desert sand. Researchers study this to help develop materials with good erosion resistance for helicopters, pipes, and other applications.

Ultra-tough Shrimp Hammer

The peacock mantis shrimp feasts on snails, crabs and other mollusks and crustaceans by smashing through their shells with its front hammer-like claws, delivering 500 Newtons of force. This is powerful enough to punch through aquarium glass.

Science magazine June 8, 2012 DOI: 10.1126/science.1218764

Whitesides et al. Science 295, 2418 (2002);

Self assembly at all scales?

What enables self assembly?• Static assembly (thermodynamic free energy minimum; requires agitation) -- 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)

SAM: Self Assembled Monolayer

• Chemisorbed molecules• Stabilized by intermolecular van der Waals interaction

solid

moleculesfrom solution

SAM: Self Assembled Monolayer

Review article: J.C. Love, et al., Chem. Rev. 2005, 105, 1103(G. Whitesides group, Chem Dept, Harvard)

HS(CH2)nX alkanethiol on gold (Au)

where X is the end group of the chain –CH3, –OH, or –COOH

Longer alkanethiol molecules have greater thermodynamic stability

SAMs on Nanoparticles

J.C. Love, et al., Chem. Rev. 2005, 105, 1103

gold NP

There are now many configurations and uses of SAMs

imperfect packing

Nanoparticle Monolayer Formed at a Liquid-Air Interface

Nanoparticle Monolayer Formation

Nature Materials MOVIE

toluene

Requirements:• rapid evaporation• excess dodecane present• attractive interation to liq-air interface and between particles

SELF ASSEMBLY with DIBLOCK COPOLYMERS

Block “A ” Block “B”

10% A 30% A 50% A 70% A 90% A

~10 nm

Ordered Phases

PMMA PS

Scale set by molecular size

CORE CONCEPT FOR NANOFABRICATION Deposition

Template

EtchingMask

NanoporousMembrane

Remove polymerblock within cylinders(expose and develop)

Versatile, self-assembling, nanoscale lithographic system

(physical orelectrochemical)

Array Period = 24 nm Pore Diameter = 14 nm

MW = 42,000PS/PMMA

TEMPLATE CHARACTERIZATION

100 cpp

SEMSAXS

Improving Order: Guided Assembly in a Trench: Graphioepitaxy

UMass-Seagate

assemble here

side view

top

view

nanoporous template

Nanomagnets in a Self-Assembled Polymer Mask

1x1012 magnets/in2

Data Storage......and More

Metal Nanorings

Ferromagnetic cobalt rings as small as 15 nm OD

Mohan Srinivasarao, et al. Science 292, 79 (2001).

Kinetic Self-Assembly - by Breath Figures

Polystyrene Film

More Fabrication by Breath Figures

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)

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.

Anodized Aluminum Oxide Templates

Aluminum

Nanoporousaluminum

oxide (AAO)~ 40 V

counter electrode

Anodization Acid Bath

I

e.g., • Keller, et al., J. Electrochem. Soc. 100, 411 (1953) • Masuda & Fukuda, Science 268, 1466 (1995)

(oxalic, sulfuric, orphosphoric acid)

Masuda, et al.

Proposed AAO Growth Mechanism

Figure adapted fromJessensky, Müller, & Gösele, Appl. Phys. Lett. 72, 1173 (1998)

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 possibleby choice of anodizationconditions

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)

Molecular Recognition("lock and key" bonding)

biotin-avidin pair (site-specific binding)thymine (T) adenine (A)

guanine (G) cytosine (C)

hydrogen bonding

Using Synthetic DNA for Designer Structures

Ned Seeman, NYU

Designer DNA molecules can be synthesized chemically, and allowed to assemble into a specific configuration of lowest energy.

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

Programmed DNA Folding: Advanced DesignsWilliam Shih, Harvard University

Microfluidic Assembly

Application: RFID

Alien Technology

Nanoscale Phase SeparationIBM "air gap" technology

Introducing nanoscale air pockets into the insulating material separating wires on a computer chip -- lowers the capacitance

flow direction

Parts, having unique shape, are delivered via fluid flow to mating pockets on an assembly substrate.

NEW! Self-Folding Objects

https://www.youtube.com/watch?v=NKRWZG67dtQ http://www.prism-magazine.org/jan13/feature_01.cfm

Large Scale Self-Assembly (Geological)

Giant's Causeway(Northern Ireland)

Volcanic basalt cooled rapidly to form these (mostly) hexagonally shaped columns

Explore concepts of self assembly in the classroom

• Balls in a box (best packing)• Straws or toothpicks in a container (lattice and defects)• How shape influences packing density and the symmetry of assembled structures• Objects floating on water (Cheerios and other shapes)• Two-dimensional array of magnets; floating magnets - attractive and repulsive cases• Crystallization - explore how conditions influence size and perfection of crystals

Underlying principles: forces (non-directional or directional), shape, thermal agitation