CHE5480 Summer 2005

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CHE5480 Summer 2005

• Dendrimers and Nanofluidics

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Nanostructured Materials

• Carbon nanotubes
• Aerogels
• Zeolites
• Dendrimers
• Self-assembled monolayers
• Nanoparticles
• Nanowires
• NEMS, etc.

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Example of NanostructuresStarburst Dendrimers
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What is a dendrimer? Branched polymers
(dendron tree in Greek)Functionality 3
(Nitrogen)
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Generations of Dendrimers
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Generations of Dendrimers
2nd gen.
5th gen.
4th gen.
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PAMAM Dendrimer (polyamidoamine)

• Alternating
• (B)-AB-AB-AB-...
• Ethylenediamine (B)
• H2N-C-C-NH2
• Methylacrylate (A)
• CC-CO-OCH3

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PAMAM Moieties
Diamine
Acrylate
NH3 or Diamine
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Size of PAMAM DendrimersGeneration
M.W. Angstrom (dia.)
End Gps
(1 nm 10 Angstroms)
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Equivalent Sizes with Cells
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Applications of Dendrimers

• Gas and chemical sensors
• Catalysts
• Drug delivery and gene therapy
• Surface modifiers (tribology, and information
  storage)
• Bio compatible materials
• Electronic devices and antennae

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Nanofluidics Flows in channels of nanometer
dimension
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Nanofluidics Examples of MEMS NEMS (Micro-
Nano-electromechanical systems)
Lieber (Harvard)
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(Laboratory-on-a chip)
Lieber (Harvard)
MEMS
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Flow behavior in nanofluidics
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Flow behavior in nanofluidics (2)

• LOCOMOTION?
• difficult to make fluid flow in small
  channels.
• Driving forces
• Pressure
• Surface-capillary force
• Electric (electroosmotic, electrophoretic,
  electrohydrodynamic, electrowetting), and
  magnetic (magnetohydrodynamic)
• Soundacoustic
• Centrifuge (rotation)

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Making Circuitry by Nanofluidics(Lieber,
Harvard)

• Purpose using viscous flow in nanochannels.
• to orient and assemble nanowires (to make
  logical circuitries).
• Note at nanoscale, the surface effects are large
  (due to large surface-to-volume ratio). Thus
  viscous forces dominate in the flow.

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(1) Make a mold of channels (PDMS-polydimethylsilo
xane). (2) Disperse nanowires (GaP, InP, Si) in
ethanol, the carrier solvent. (3) Flow the
suspension through the nanochannels.
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SEM images of aligned nanowires.
Charles Lieber (Harvard)--2
SEM bar 2 µm
bar 50 µm
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Nanocircuitries Examples of NEMS
Lieber (Harvard)
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hydrophobic surfaces
OTS
Harvard
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What happens to the flow when the interface is
hydrophobic? --Slip
2002 Phys. Fluids
Velocity at wall is 10 of the center (NOT zero,
i.e. Slip). This increases the total volumetric
flow.
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On what theories to use for nanoscale flows?
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2. Nanostructured materials Gas adsorption in
dendrimers
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Dendrimer PAMAM
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2. Nanostructured materials Gas adsorption in
dendrimers