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Nanotechnology
Versatile Bottom-up Nanofabrication
Technique:
Layer-by-Layer Assembly
~ Anuja Choubey
12-01-2007
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Introduction
Nanofabrication Techniques
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“Top-down”
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Photon based Nanolithography
Electron Beam Lithography
Focused Ion Beam Lithography
“Bottom-up”
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Self Assembled Monolayers (SAMs)
Block Copolymers
Electrostatic Self-Assembly
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Layer-by-Layer Assembly (LBL)
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Background
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Langmuir-Blodgett (LB)
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Self assembled Monolayer (SAM)
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Expensive instrumentation
Not applicable for non-amphiphilic materials
Not suitable for multilayer fabrication
Layer-by-Layer Assembly (LBL)
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Inexpensive
Simple, Easy-to-use
Enhanced modularity
Potential for greater versatility
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How LBL works?
Ariga et al., Phys. Chem. Chem. Phys., 9 (2319–2340), 2007
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Materials Used
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Polyions- PAH, PDDA, PSS, PVS, PAA, PPV
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Proteins, DNA, Charged polysaccharides
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Charged inorganic substances
 Colloidal nanoparticles
 Clay
 Nanosheets
 Modified zeolite crystals.
Charged supramolecular assemblies
 Bolaamphiphile monolayers
 Lipid bilayers
 LB films
 Stacked dye molecules
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Characterization
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Microscopy
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AFM
TEM
SEM
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Optical Spectroscopy
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Ellipsometry
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Quartz Crystal Microbalance (QCM)
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Ellipsometry
Quartz Crystal Microbalance
A. Tronin et al., Colloid Polym. Sci., 272, 1317, 1994
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Applications
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Anti-static coating for plastics
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Sensors
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Oxygen sensor
Glucose biosensor
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Light emitting diode
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Fuel Cells
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Polymer Capsules
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Micro-reactors
Targeted Drug delivery
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Fuel Cell Application
http://web.mit.edu/hammond/lab/ashcraft.htm
http://en.wikipedia.org/wiki/Image:Fuel_cell_still.gif
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Formation of Polymer Capsules
E.Donath et al., Angew. Chem. Int. Ed. 37, 16(2202-2205), 1998
www.coes.latech.edu/bme/research/reu/layer%20by%20layer%20assembly.htm
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Limitations
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Fuzzy internal architecture
Sensitive to working conditions
 Humidity
 Drying between cycles
Future Work
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Synergy with other techniques
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Top-down microfabrication
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Questions?
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