Nanotechnology where size matters J Emyr Macdonald
Overview Ways of seeing very small things What is nanotechnology and why is it important? Building nanostructures What we can do with nanotechnology? 1. Electromechanical Systems e.g. motors 2. Electronic circuits
Things just keep getting smaller Computers of the future may weigh no more than 1.5 tons Popular Mechanics, 1949 I think that there is a world market for about five computers Thomas J. Watson, IBM Director, 1943
Lengthscales White blood cell P4 feature size 1km 1m 1mm 1µm 1nm
Nanometer Lengthscale 1 nm on a football is equivalent to 4 cm on the surface of the earth (and one atom would be the size of a pea) 1 µm is equivalent to the radius of Cardiff
Probing matter... Optical microscope how small can we see? Magnification? 70 cm resolution image of San Francisco from satellite Magnification isn t a major problem
Probing matter... Optical microscope how small can we see? Magnification? Diffraction
Probing matter... X-ray diffraction 1-dimensional diffraction grating 3-dimensional grating
Probing matter... X-ray diffraction: large molecules Foot and mouth virus full molecular structure The European Synchrotron at Grenoble
Probing matter... Electron Microscope
Some electron microscopy images Porcupine quills are sharp as needles. Unlike needles, quills have backwards facing barbs that catch on the skin making them difficult to extract.
The claw of a Black Widow spider. The claw has three hooks, the middle one used to work the silk.
Cucumber: Lower large storage cells Upper the cucumber skin is composed of long columnar cells.
www.columbia.edu/.../vol21/vol21_iss6/ record2106.32c.gif The fossilized shell of a microscopic ocean animal. This ancient creature, called Radiolarian, lived in the waters off Antarctica and is now used to study such things as climate and ocean circulation.
Probing matter... Scanning Tunnelling Microscope (STM) na
Probing matter... Scanning Tunnelling Microscope (STM) STM image of an ultra-clean silicon surface http://www.geocities.com/capecanaveral/5702/stm_si7x7. jpg
Probing matter... Atomic Force Microscope (AFM) Dividing chromosomes Dr T McMaster, Bristol
Probing matter... Optical Microscope X-ray diffraction Electron Microscope Scanning Tunnelling Microscopy Atomic Force Microscopy Resolution limited to 500 nm 0.2 nm resolution but needs order Good imaging but needs intense sample preparation 0.2 nm resolution but needs conducting surface 0.5 nm resolution suitable for biological samples
There s plenty of room at the bottom What I want to talk about is the problem of manipulating and controlling things on a small scale What I have demonstrated is that there is room that you can decrease the size of things in a practical way. Richard Feynman Dec. 1959
So what is nanotechology? Development and application of structures smaller than 100nm Potential to produce new materials, devices, health treatments etc. Multi-discipline field aimed at materials, control and function
Two different areas Generating movement: motors and actuators Electronic devices & circuits Two lengthscales 0.1 10 µm 0.1-50 nm micro nano Two different approaches Top-down lithography & etching Bottom-up molecular self-assembly A working molecular nanotechnology: LIFE
Tools for nanotechnology Lithography: fabrication Optical tweezers: manipulation Scanning Probe Microscopies imaging (& manipulation & fabrication)
Photolithography (top-down approach) expose with UV light & remove exposed resist write mask & etch away
Photolithography - features Present technology gives feature sizes ~100nm Resolution limited by wavelength of light used For true nanostructures need to use X-rays (expensive, damage mask, optics difficult) Electron beams (expensive, very slow process)
Optical Tweezers: manipulation If the bead is off-centre then it refracts more light in one direction than the other. The bead experiences a force in the opposite direction by conservation of momentum.
Manipulation with STM Individual xenon atoms moved around a copper surfaces at low temperatures Don Eigler, IBM
Feynman s Challenge $1000 for first person to build an electrical motor smaller than 0.4mm William McLellan succeeded using tweezers and a microscope Very slow and tedious There must be better ways!!
Electromechanical devices (Motors) DC motor: Motor experiences a torque in a magnetic field. Direction of force needs to be reversed twice in each cycle.
Micro-electromechanical systems MEMS Motors at the µm-mm scale Fabricating gaps in structures
0.5 mm (500 µm) Sandia laboratories Distance between chain link centers = 50 µm. (Diameter of a human hair is 70 µm.) http://www.sandia.gov/media/newsrel/nr2002/chain.htm
Micromachines Sandia National Laboratories, Albuquerque Movies of rotating motor: http://www.sandia.gov/mstc/technologies/micromachines/movies/motors.html
Nano-electromechanical systems NEMS Molecular wheels These do not have bearings and as yet cannot perform useful work. J Gimzewski, IBM Zurich hexa-butyl decacyclene (HB-DC) molecules of 1.75 nanometer diameter
A self-assembled molecular motor: the bacterial flagellum Motor driven by protons rather than electrons. Has forward and reverse motion.
The flagellum: precision bearings Electron Microscopy images D J derosier Cell 93 (1998)17 Reconstruction
Flagellar filament: cross-section 50 proteins: 20 functional proteins in flagellum 30 proteins for construction and maintenance
Flagellum: assembly process Movie of Flagellum Assembly: http://stock.cabm.rutgers.edu/blast/#a Proceedings of 6 th Bacterial Locomotion and Signal Transduction (BLAST) Meeting held in January 2001 in Cuernavaca, Mexico
Microelectronics: transistor - Source reduced current - Gate + Drain In a field-effect transistor, the current to the drain is affected strongly by the voltage applied to the gate.
Nanoelectronics: Molecular Conductors and Devices Carbon Nanotubes (CNT) Graphite-like sheets rolled into long rod with capped ends. Conduction properties depend on rolling axis.
Measuring conduction in CNT Carbon Nanotubes between electrical contacts
Carbon Nanotube Transistor Source Gate Drain IBM Research, Yorktown Heights
Nanoelectronics: Molecular Conductors and Devices Carbon Nanotubes (CNT) DNA Semiconducting Polymers (Polythiophenes)
Self-assembly of DNA 4 bases: adenine (A), cytosine (C), guanine (G) thymine (T) A bonds to T and C bonds to G Specific binding is fundamental to molecular nanotechnology
Self-assembly of DNA structures Can structures be designed and self-assembled? The different strands are made by genetic engineering approaches. Good potential for future.
Summary Nanotechnology is developing at a very rapid pace Two approaches: top-down (lithography ) and bottom-up (molecular self-assembly) Two themes: mechanical displacement (motors etc) and electrical circuits and devices. Molecular assembly is more difficult involving physics and chemistry but arguably greater potential. Life is the only advanced molecular nanotechnology to date