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رابطة المبعوثين العائدين من الخارج برعاية ا.د /.فرحة الشناوي الندوة المجمعة األولى تكنولوجيا النانو 1 د/عبد الكريم أبو الوفا كلية العلوم Nano wires 2 ا.د/.محمد نبيل صبري كلية الهندسة Nano devices What is nanotechnology? 0.1n 1n 10n 100n 1m 10m 100m H2O DNA Virus 1cm 1m White blood cell Human hair NEMS/MEMS Nano devices Nano tubes Nano transistors 100m Quantum dots ... No sharp Frontiers! Why is it special? Ability to act on phenomena previously uncontrolled: Physical properties Chemical reactions Biological transformations This lecture is mainly about: Potentials AND Risks How is it fabricated? Two approaches Top – down Bottom – up Cutting a nano piece out of a bulk (used in microelectronics) (self ) Assembling tiny objects into Nano devices H-bond DNA-like molecules Assembles to: Top – Down main processes Lithography Photolithography Electron beam lith. Ion implantation Thermal treatment Etching Wet etching Dry etching Deposition Chemical Vapor Dep. CVD Physical Vapor Dep. PVD … Top – Down example: a nano-switch 1 1-LPCVD Si3N4-125n Patterning 2-Photolithography Photo-resist Si-125m Exposing 3-Reactive Ion Etching RIE (He + SF6) 4- Wet Etching (KOH) Top – Down example: a nano-switch 2 5-Patterning 6-Resist + Deposition of Cr (60n) + Electron beam lithography 1m 7- Deposition of Cr (5n) + Au (70n) 8-RIE Carbon Nano Tubes (CNT) Take a sheet of carbon atoms … Roll it! Carbon Nano Tube: Strength = 100 x Steel; Weight = 1/6 x Steel You still need to assemble many of them to be useful! Prof. Richard Smalley (Rice U.): “it would take a single nanoscopic machine millions of years to assemble a meaningful amount of material.!” Eric Drexler believes assemblers could replicate themselves, resulting in exponential growth. http://science.howstuffworks.com/nanotechnology4.htm Bottom – Up example: a cantilever Cantilever beam material Fe2O3 nano Polyelectrolyte particles CNT Creating cantilever structure Biomedical Applications Lab on a chip Manipulating drops (micro-fluidic) (video) Detecting Molecules “Artificial nose”! Drug delivery systems Nano devices are smaller than cells Nano devices can easily enter in cells for early detection of cancer In vivo Cell size: 1 – 2 m National Cancer Institute More efficient cancer test National Each cantilever can capture one specific type of molecules Cancer Institute Cantilever bending: electronically detected Nano-pores help reading DNA code Nano-pores: DNA passes through one strand at a time, DNA sequencing more efficient. Monitor shape & electrical properties of each base, or letter, Hence, decipher the encoded information, including errors associated with cancer. National Cancer Institute Nano-pores in Aluminum 100 n Using CNT to detect DNA defects National Cancer Institute A Nano-tube (sharp edged pin) Traces the shape of DNA, making a map Using quantum dots to detect cancer Quantum dots: Crystals (few nm) with size dependent optical properties UV stimulus: They glow (size dependent color) National Can be designed to bind to specific DNA sequences. Cancer (to detect and treat cancer cells) Institute Dendrimers: the complete solution! Cancer Cell Drug Cancer detector Dendrimers Cancer detector Cell death Monitor Man-made molecules (~ a protein). Shape gives vast amounts of surface area Can attach therapeutic agents or other biologically active molecules. Programmable nano – robots! A near future dream! Patients will drink fluids containing nano-robots programmed to attack and reconstruct the molecular structure of cancer cells. Nanorobots could also perform delicate surgeries more precise than the sharpest scalpel [source: International Journal of Surgery] Nano for Energy 4th Generation Solar Cells Fuel Cells Energy Harvesting Solar Energy World electric power demand: ~ 14 TW Incident Solar power: 120, 000 TW!! Consider 10% efficiency, & exclude oceans and cities: 600 TW Average extractable power from Egyptian desert alone: 15 TW Solar energy economics Not only efficiency matters, but also cost! $ 0.1/ W $ 0.2/ W $ 0.5/ W 100 Thermodynamic Limit Efficiency (%) 80 60 $ 1.0/ W III 40 Theoretical Limit 20 IV 0 II 100 $ 3.5/ W I 200 300 Cost $ / m 2 400 500 Prof. Rastogi, Binghamton U. Expected grid parity: year 2012 – 2018 (depending on region) [source iSupply Applied Market Intelligence] Nano pillars for solar cells Radiation losses due to reflection 900n Anti Reflection Coating Using Nano Pillars Thin film solar cells Prof. Rastogi, Binghamton U. Thin film: small amount of Si (+amorphous Si) Low initial price Flexible: low installation cost Quantum dots for solar cells – 1 Conduction band Energy Band gap Donors level Electrons Valence band Incident Photons Losses for both too high and too low energy photons Need to have “adjustable” band gaps ?? Quantum dots for solar cells – 2 Conduction band Energy Band gap Valence band For Quantum dots: Band Gap is size dependent: Make many sizes to capture all incident photons Small size: Highly excited electron can share energy with another one Fuel cells Fuel can be H2 or other hydrocarbons Membrane (heart of the device) passes H ions only Platinum catalysts Heat (~85oC) Can power Handheld devices Up to trucks Environmental impact of burning fuel U.S. Nano improvements of fuel cells Higher efficiency membrane Higher surface area and lower quantity of catalyst (Platinum) New less expensive catalyst materials Energy harvesting: Thermo-ionic effects DV (open circuit) = S (Thot – Tcold) S: Seebeck Coefficient Materials A & B can be: - Two different metals - Semiconductors with different doping When connected to a load: W = h Qhot h < 1 – Tcold/Thot h increases with: S, s (elec cond) h decreases with k (thermal cond) Figure of merit Z = S2 s/k Metal/Semiconductor Nano composites: Very High Z Thot Heat Qhot (W) Material B Material B DV Power W (W) Material A Tcold Heat Qcold (W) Nanopiezotronics Energy harvesting: nano brush Zinc oxide nano wires 4-layer integrated nano generator: Output power: 0.11 µW/cm2 at a voltage of 62 mV. Nano Electronics is here since long! A transistor Gate Source Oxide thickness ~ 10n Drain Channel length < 45 nano Major problem: heat! The growing power density (measured in W/cm2) of Intel's microchip processor families. (Source: Intel) R&D issues in thermal effects Modeling & Simulation Multiple Physics (Mainly Electro-thermal) Multiple Scales (transistor data center ) Compact Thermal Models: New technology for multiple source problems: 3D – ICs, SoC … High performance simulation/optimization tools Micro-fluidics & micro heat transfer Micro-channels Micro effects in 2 phase: Electro wetting/micro-boiling Integrated micro/nano coolers TACS Temperature Aware Computer Systems Thermal aware layout Thermal aware operating systems (ex: scheduling …) Other R&D trends Flexible flat display panels using nanowires NEMS for high density memory (terabyte/ in2) Molecular sized transistors Self aligned nanostructures to build integrated circuits Nanotechnology impact on environment Pros: A high potential for new and renewable energies Less CO2 emission A high potential for pollution detection A high potential for water treatment: Composition detection Desalination Waste water treatment Solution of many health problems BUT …! Nanoparticles may accumulate in vital organs, creating a toxicity problem. Use of toxic, basic or acidic chemicals organic solvents 99% of materials used are not in final product Actual manufacturing of nanodevices is highly energy intensive Unknown impact of nanoparticles on natural cells Conclusion Nanotechnology is not the future, it is the present and the near future Nanotechnology has highly promising applications in almost all engineering, medical, environmental … issues. It is inherently multi-disciplinary Side effects, potentially harmful, are not yet quite well assessed. • app_micro_drop_merge.avi • app_micro_Tjunction3D.avi