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why use mirosystem products?
- Less material usage
- ▪ Lower power requirements
- ▪ Greater functionality per unit space
- ▪ Accessibility to regions that are forbidden to larger
- products
- ▪ In most cases, smaller products should mean lower
- prices because less material is used
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what are microsystems typically made of? why?
silicon! Si!
- - microdevices have electronic circuits, so the circuit and device can be made on the same substrate
- - Si has good mechanical properties:▪ High strength and elasticity, good hardness,
- and relatively low density
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difference between microsensor and microactuator and microstructure and microcomponents
microsensor: A sensor is a device that detects or measures some physical phenomenon such as heat or pressure. Microsensors have been developed to measure force, pressure, position, speed, acceleration, temperature, flow, and various optical, chemical, environmental, and biological variables
microactuator: converts a physical variable of one type into another type, and the converted variable usually involves some mechanical action. Examples of microactuators: valves, positioners, switches, pumps, and rotational and linear motors
microstructure and microcomponents: other structures. Examples: microscopic lenses, mirrors, nozzles, gears, and beams ▪ These items must be combined with other components in order to provide a useful function
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difference between silicon, silicone, and silica
silicon - the element, Si. it is a semiconductor, metalloid
silicone - epoxy, PDMS, it is a polymer
silica - SiO2, sand and ceramic
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what is photolithography
this
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what is chemical milling
you can make undercuts!
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what is chemical machining
machining but with chemicals? idk. helps silicon processing
- Cleaning - to insure uniform etching
- 2. Masking - a maskant (resist, chemically resistant to
- etchant) is applied to portions of work surface not to
- be etched
- 3. Etching - part is exposed to etchant that chemically
- attacks those portions of work surface not masked
- 4. Demasking - maskant is removed
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MST often requires other materials in addition to
silicon to obtain a particular microdevice. what other microfabrication techniques are used?
LIGA
LIGMA BALLS
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what applications would be good for a low height to width ratio and a high height to width ratio
low h:w - integrated circuits bc flatter
high h:w - MEMS bc taller
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what is LIGA? how does it WORK
LIGA is a German acronym for Lithographie, Galvanoformung, Abformung (Lithography, Electroplating, and Molding) that describes a fabrication technology used to create high-aspect-ratio microstructures.
it is additive and works for high height :width ratio
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this is where i talk about polycrystalline vs single crystal Si
Polycrystalline uses chemical wet etching. The process is isotropic (one direction)
Single crystal Si, etching rate depends on the orientation of lattice (100, 110, 111) with wet etching. Process is anisotropic (multiple directions)
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how do you make a 1 direction silicon wafer
Czarkovski's/Czochralski method
- Silica purified to remove oxygen to be Silicon
- silicon is melted in crucible
- crystallization in direction of the seed crystal which is then pulled
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why 111
etching solutions have a low etching rate in the direction of the 111 crystal face so sharp edges and it lasts longer
good for bulk micromachining and surface micromachining
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how to machine for cantilever
sio2 layer on si, etched, add poly si, etch
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what is lift off technique? what is resist?
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what is soft lithography?
- for processes that use an elastomeric flat mold to
- create a pattern on a substrate surface
- A master pattern is fabricated on a silicon surface
- using lithography
- ▪ This pattern is then used to produce a flat mold of
- polydimethylsiloxane (PDMS)
BASICALLY master pattern made from lithography, PDMS mold is then made from pattern
used for microfluidic devices
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what are two types of soft lithography?
micro imprint lithography - pdms makes a smol imprint on the mold
micro contact printing
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What are buckyballs? how are they related to nanotechnology products?
buckyballs are related to the carbon nanostructures, a type of nanotech product
buckballs are a structure of a C60 molecule. electrical insulator but can be doped to be a conductor. good for medical use as well
we're mostly interested in them because of carbon nanotubes
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why are carbon nanotubes gr8
can have either conducting or semiconducting properties
the conductivity is superior to copper due to fewer defects
elastic modulus and tensile strength of carbon nanotubes are much greater than steel
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what are the two structures of carbon nanotubes?
armchair
zigzag
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types of nanofabrication processes
- Top-down approaches
- ▪ Adaptation of microfabrication techniques to make
- nanoscale objects
- Bottom-up approaches
- ▪ Atoms and molecules are manipulated and combined to form larger nanoscale structures
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what are types of top down processing approaches
- Mostly based on lithographic techniques
- ▪ Extreme UV – UV wavelengths down to 13 nm
- ▪ Electron-beam lithography – resolutions ~ 10 nm
- ▪ X-ray lithography - resolutions ~ 20 nm
- ▪ Micro-imprint lithography – uses flat mold with desired
- pattern that physically deforms resist surface to create
- regions that will be etched
- ▪ Nano-imprint lithography – same as micro-imprint but
- adapted to nanoscale
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what are types of bottom up processes
production of carbon nanotubes
nanofabrication by scanning probe techniques
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how do you make carbon nanotubes (3)
- Laser evaporation method - GRAPHITE in quartz tube filled w argon, laser beam on surface causes carbon atoms to evaporate from bulk graphite, argon moves C to cool copper. when condense, nanotubes
- Carbon arc techniques - CARBON ELECTRODES separates by 1 mm, 25 V applied and C atoms move from + to - electrode where they form nanotudes. 1-5 nm dia
- Chemical vapor deposition - HYDROCARBON gas heated to 1100 degrees Celsius, decomposing and releasing carbon atoms. Atoms condense on cool substrate to form nanotubes
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