Nanotechnology projects

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Nanotechnology projects applications

• Lecture 5
• ???

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Frontiers of nanotechnology from Asia-Pacific
Nanotech Forum

• (Tsukuba, 2002)

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The vision and strategy of the US national
nanotechnology initiative

• M.C. Roco
• US national science foundation

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History

• 1981
• able to measure the size of an atom cluster on a
  surface (IBM, Zurich)
• 1991
• able to move atoms on surface (IBM, Almaden)
• 2002
• able to assemble the molecules by physically
  positioning the component atoms

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Nanotechnology

• National Nanotechnology Initiative (NNI)
• Long-term visionary program since 01/2000
• 22 departments and independent agencies
• 961 million (2004)
• Government investments worldwide 4 billion
• international collaborations and competitions

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NNI nanotechnology

• Definition
• Nanotechnology is working - measuring,
  manipulating and controlling - at the atomic,
  molecular and supramolecular levels, at a length
  scale of approximately 1 - 100 nm, in order to
  understand and create materials, devices, and
  systems with fundamentally new properties and
  functions because of their small structures.

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table 4.1
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Commercialization

• 1st generation (commercialized)
• passive nanostructure
• applied in coatings, nanoparticles, bulk
  materials (nanostructured metals, polymers and
  ceramics)
• towards systematic design method
• 2nd generation
• active nanostructure
• transistors, amplifier,targeted drugs and
  chemicals, and adaptive structures (2005)

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Commercialization

• 3rd generation
• systems of nanosystems
• 3D features, heterogeneous nanocomponents
• specific assembly techniques (such as
  bio-assembly, networking at the nanoscale, new
  architectures)
• 2010
• 4th generation
• molecular nanosystems
• nanodevices, biomimetics and new molecular
  designs (2020)

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Nanotechnology for the next generation

• T.Nakahara T. Imai
• Sumitomo Electric Industries Ltd.

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Policies

• Similar projects from
• Nanocarbon materials
• nanoelectronics
• nanobiomaterials
• Others?
• Diamond nanoemitter project

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Targets

• Size!

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Small size effect

• Compressed ferrous alloy powder
• due to resonance
• high electromagnetic wave adsorption in the
  microwave frequency region
• adjust particle shape and metal composition
• different absorption peak from 0.5 5G Hz
• For small and precise communication
• mobilephones, PC, etc.

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Nano size effect

• Nanomaterial diamond
• rigid atomic structure
• high hardness, high thermal conductivity and high
  acoustic velocity
• semiconductor properties
• apply as semiconductor devices, optical devices,
  electron emission devices
• fabrication and synthesis technology
• manufactured very precisely in a controlled manner

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Applications

• Triode vacuum tube (2000C) VS. micro vacuum
  triode (30C)

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Vacuum Microelectronic Device (VMD)
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Next generation applications for polymeric
nanofibres

• T.C. Lim and S.Ramakrishna
• National University of Singapore

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Polymeric fibres

• Targets
• high tensile modulus and tensile strength
• UV resistance, electrical conductivity,
  biodegradability
• typical 1-100 ?m in diameter
• Nanofibres
• decrease in pore size, a drop in structural
  defects, enhanced physical behaviour

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Nanofibres applications

• Polymer composite reinforcement
• the moduli and fracture resistance improvement in
  epoxy resin (300 nm PBI fibres)
• Electrical conductors
• electrochemical rxn rate ? electrodes surface
  area
• conductive nanofibrous membrane for electrostatic
  dissipation, corrosion protection,
  electromagnetic interface shielding
• Sensors
• huge surface area increases the sensitivity

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Biomedical applications

• Medical prostheses
• reduce stiffness mismatch / prevent fracture
• a gradient fibrous structure at the tissue/device
  interface
• Tissue engineering scaffolds
• biocompatible with the native tissue structure
• design 3D scaffold of synthetic biodegradable
  matrices that provide temporary templates for
  cell seeding, invasion, proliferation and
  differentiation

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Biomedical applications

• Drug delivery
• polymeric nanofibres (drug carrier)
• increase dissolution rate
• increase surface area
• Wound dressing
• biodegradable polymeric fibres spray
• aids the formation of normal skin growth
• prevent the formation of scar tissue
• non-woven nanofibrous membranes with pore
  (5001000 nm)

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Filtration applications

• Filter media
• Nano-fabrication of nano filter media
• higher filter efficiency at equal pressure drop
• NonWoven Technologies Inc. of Georgia
• thin-plate die technology for submicron fibres
• Electrospinning process

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Filtration applications

• Protective clothing
• lightweight, breathable fabric, permeable to air
  and water vapour, insoluble in solvents and
  highly reactive with nerve gases and other
  chemical agents
• military?
• electrospun nanofibres prevent lower impedance to
  moisture vapour diffusion and maximum efficiency
  in trapping aerosol particles as compared to
  conventional textiles

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Application of nanomaterials

• G.Z. Cao
• University of Washington, Seattle

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Nanomaterial application based on

• peculiar physical properties
• gold nanoparticles used as inorganic dye to
  introduce colors into glass and as low temp.
  catalyst
• huge surface area
• mesoporous titania for photoelectrochemical cells
  and nanoparticles for sensors
• small size
• offer extra possibilities for manipulation and
  room for accommodation multiple functionalities

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Catalysis by gold nanoparticles

• Catalyst
• Clean gold nanoparticles are extremely active in
  the oxidation of CO if deposited on partly
  reactive oxides (e.g. MnO2).
• Extraordinary high activity for partial oxidation
  of hydrocarbons, hydrogeneration of unsaturated
  hydrocarbons, and Nox.
• The 6s2 and 5d electrons helps!

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Gold catalysts

• Essential requirements
• small particle size (lt 4 nm)
• use of reactive support
• particles in intimate contact with the support
• carefully designed chemical functionality of the
  ligand shell (not the potential catalytic
  activity of a nanostructured clean metal surface)

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Band gap engineered quantum device

• Band gap engineering
• synthetic tailoring of band gaps with the intent
  to create unusual electronic transport and
  optical effects
• most of the devices based on semiconductor
  nanostructures are band gap engineered quantum
  devices

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Quantum well device

• Quantum well lasers
• III-V semiconductors
• GaAs or GaAsP
• lower threshold current
• lower spectra width
• single or multiple quantum wells
• allow the possibility of independently varying
  barriers and cladding layer compositions and
  widths
• higher threshold carrier and current densities
  for single quantum well lasers

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Quantum well device

• Light emitting diodes (LED)
• Based on nanostructures of wide-band gap
• quantum well heterostructure configuration
• II-VI semiconductor materials
• ZnSe or ZnTe
• direct energy band gap to achieve high internal
  radiative efficiency

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Quantum dot device

• The key parameter that controls the wavelength is
  the dot size
• large sized dots emit at longer wavelength
• quantum dot heterostructures synthesis
• molecular beam epitaxy (????) at the initial
  stages of strained heteroepitaxial growth via the
  laser-island or Stranski-Krastanov growth model

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Quantum dot device

• Quantum dot lasers
• ultralow-threshold current densities
• low sensitivity to temperature variations
• Quantum dot detectors
• not sensitive to normal-incident light

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Nanomechanics

• Cantilevers (???)
• a nanomechanical sensor device for detecting
  chemical interactions between binding partners on
  the cantilever surface and in its environment
• detection modes
• static, dynamic, heat
• AFM applications

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Photoelectrochemical cells

• Also photovoltaic cells or solar cells
• device
• need for higher conversion efficiency of solar
  energy to electrical power
• silicon-based p-n junction materials or other
  heterojunction materials
• InGaP/GaAs (20 efficiency)
• difficulties high cost of production, expensive
  equipment, necessary clean-room facilities

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Other photoelectrochemical cells

• ORegan and Grätzel, 1991
• dye-sensitized solar cell
• low product cost device with gt10 efficiency
• Sol-gel-derived titania films with a crystal
  structure of anatase and mesoporous structure
• porous nanocrystalline TiO2 film efficient
  light-absorbing dye

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dye-sensitized solar cell

• Mechanism
• TiO2 functions as a electron-capturing and
  electron-transporting material
• the dye adsorbed to TiO2 is exposed to a light
  source, absorbs photons upon exposure, and
  injects electrons into the conduction band of the
  TiO2 electrode
• Nanostructure
• large surface area

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TiO2 film

• Methods
• Chemical vapor deposition
• Gas-phase hydrothermal crystallization
• Powder compression
• Sol-Gel (coating?)
• efficiency
• lt10