320 likes | 449 Vues
CHE5480 Summer 2005. Dendrimers and Nanofluidics. Nanostructured Materials:. Carbon nanotubes Aerogels Zeolites Dendrimers Self-assembled monolayers Nanoparticles Nanowires NEMS, etc. Example of Nanostructures : Starburst Dendrimers.
E N D
CHE5480 Summer 2005 Dendrimers and Nanofluidics
Nanostructured Materials: • Carbon nanotubes • Aerogels • Zeolites • Dendrimers • Self-assembled monolayers • Nanoparticles • Nanowires • NEMS, etc.
What is a dendrimer? Branched polymers(dendron = tree in Greek)Functionality= 3 (Nitrogen)
Generations of Dendrimers Your Text Here
Generations of Dendrimers 2nd gen. 5th gen. 4th gen.
PAMAM Dendrimer (polyamidoamine) • Alternating (B)-AB-AB-AB-... • Ethylenediamine (B) • H2N-C-C-NH2 • Methylacrylate (A) • C=C-CO-OCH3
PAMAM Moieties: Diamine Acrylate NH3 or Diamine
Size of PAMAM DendrimersGeneration M.W. Angstrom (dia.) End Gps (1 nm = 10 Angstroms)
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
Nanofluidics :Examples of MEMS & NEMS: (Micro- & Nano-electromechanical systems) Lieber (Harvard)
(“Laboratory-on-a chip”) Lieber (Harvard) MEMS
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) • Sound—acoustic • Centrifuge (rotation)
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.
(1) Make a mold of channels (PDMS-polydimethylsiloxane). (2) Disperse nanowires (GaP, InP, Si) in ethanol, the carrier solvent. (3) Flow the suspension through the nanochannels.
SEM images of aligned nanowires.Charles Lieber (Harvard)--2 SEM: bar = 2 μm bar = 50 μm
Nanocircuitries :Examples of NEMS Lieber (Harvard)
hydrophobic surfaces OTS Harvard
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.