Role of MEMS in sensors

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Role of MEMS in sensors
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First things first, what is a Sensor ?

• A device used to measure a physical quantity
  such as temperature and convert it into an
  electronic signal of some kind (e.g a voltage),
  without modifying the environment.

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Sensors in our body

• Mechanoreceptors (feel)
• Auditory system
• Visual System
• Olfactory System (Nose)

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What can be sensed?

• Almost Everything!!!
• Commonly sensed parameters are
• Pressure
• Temperature
• Flow rate
• Radiation
• Chemicals
• Pathogens

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What is MEMS ?

• MEMS or Micro Electro Mechanical Systems is a
  technique of combining Electrical and Mechanical
  components together on a chip, to produce a
  system of miniature dimensions ..
• By miniature, we mean dimensions less than the
  thickness of human hair !!!!

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The wonder called nanotechnology

• Nanotechnology is the technology of arranging
  atoms and molecules in a material.
• This allows to alter the properties of a material
  and build structures of desired features.
• A nanometer is one-billionth of a meter.
• Nanotechnology makes it possible to manufacture
  devices 80,000 times smaller than the thickness
  of human hair !!

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A simple analogy..

• The atoms in an object can be compared to the
  blocks in a building game.
• In a building game, the blocks can be arranged to
  create different looking structures.
• Similarly, atoms can be arranged differently to
  produce a multitude of devices. This forms the
  basis of nanotechnology.

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Same game, different names

• USA MEMS
• Europe Microsystem technology
• Japan - Micromachines

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But why mems for sensors?

• Sensors made using MEMS are better than
• their conventional counterparts because they are
  
• Smaller in size
• Have lower power consumption
• More sensitive to input variations
• Cheaper due to mass production
• Less invasive than larger devices
• So good things do come in small
• packages !!!!

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Projected MEMS Market Share 2006
http//www.memsindustrygroup.org/industy_statistic
s.asp
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MEMS Revenue
http//www.memsindustrygroup.org/industy_statistic
s.asp
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Market for Sensors

• Auto Industry
• Medical industry
• Department of Defense

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Types of Sensors

• Mechanical Sensors
• Optical Sensors
• Thermal Sensors
• Chemical and Biological Sensors

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Mechanical Micro sensors

• Strain Gauges
• Accelerometers
• Gyroscopes (Rotation rate)
• Pressure Sensors
• Microphones
• Tactile Sensors (sensory feedback)
• Biological Sensors (cochlear implants)

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ACCELEROMETERS

• Used in deploying airbags, navigation,
  activity detection for pacemakers

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Sensors in automobiles
http//mems.colorado.edu/c1.res.ppt/ppt/g.tutorial
/ppt.htm
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Size is important in automotive industry
Accelerometer
www.kineticceramics.com/products/
new_products.htm
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Comparison between conventional and MEMS based
inertial sensor
Conventional MEMS
based Mass 1587.5 gm 10 gm Size 15x8x5
cm 2x2x0.5 cm Power 35 W 1mW Cost
20,000 500
Adapted from http//mems.colorado.edu/c1.res.ppt
/ppt/g.tutorial/ppt.htm
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MEMS based cochlear implant
http//www.accessexcellence.org/AB/BA/biochip3.htm
l
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Optical Sensors

• Direct Sensors
• (Light ? Electronic Signal)
• Photoemissive
• Photoconductive
• Indirect Sensors
• (Light ? Intermediate energy ? Electronic
  signal)
• Pyroelectric detectors
• Bolometers
• Biological Light Sensors

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Sight for the blind

• MEMS based array that may be inserted in the
  retina of a blind person to provide partial sight

http//www.sandia.gov/news-center/news-releases/20
02/mat-hem/blindsee.html
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Thermal Sensors

• Thermo mechanical (dimension)
• Thermo resistive (resistance)
• Acoustic (sound)
• Biological

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Features of MEMS thermal sensors

• Waterproof
• Contact free (wireless)
• Find use in household appliances (iron)
• Can be used in tight ends

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Chem Bio Sensors

• Electronic nose can sense a large number of gases
• Electronic tongue can sense a variety of liquids

http//www.estcal.com/Products.html
http//www.alpha-mos.com/proframe.htm
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Chemical lab on a chip

• Used to detect chemicals in gas, liquids and
  DNA

http//www.sandia.gov/media/NewsRel/NR2000/labchip
.htm
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Medical and homeland security applications

• Biocavity laser
• Decontamination foam
• Smart pill
• Sensors for missile systems

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Biocavity laser

• This device distinguishes cancerous from non
  cancerous cells thus aiding the surgeons in
  operations

http//www.sandia.gov/media/NewsRel/NR2000/candete
c.htm
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Decontamination foam

• It can neutralize both chemical and biological
  agents (anthrax) and help in homeland security
• Not harmful to people, hence can be dispensed
  freely

Source Sandia Labs
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Smart PILL

• Implanted in the body
• Automatic drug delivery (on demand)

http//mmadou.eng.uci.edu/
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MEMS and Marine Science
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Need for sensors in marine science

• Sensing in marine environment maybe done for
  various
• reasons
• Oil exploration and related applications
• Global weather predictions
• Monitor water quality for any contamination
• Measure parameters detrimental to the health of
  structures in the sea ( like oil rigs and ships )
• Study of aquatic plants and animals
• In military operations

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Parameters monitored in marine science

• Temperature,
• pressure, light
• transmission,
• tidal and current
• velocity
• Plant pigments
• (chlorophyll),
• plankton cells

• Dissolved gases
• (like oxygen),
• pH, metals,
• pesticides
• Seabed
• characteristics,
• Seismic signal

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Why measure these quantities after all ?

• Water temperature effects a lot of processes
  directly viz.
• Solubility of substances in water
• Feeding and reproduction of aquatic organisms
• Also, waters ability to hold dissolved oxygen
  decreases as water temperature increases. Now,
  this is really crucial for aquatic life !!

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Importance of measuring light penetration

• Indicates algal growth
• Indicates presence of silt in estuaries
  (confluence of river and the sea).
• Sediments if present in water in large amounts
• May block sunlight to submerged plants
• Can carry pesticides and other pollutants through
  the water

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Where are these mems devices attached ?

• The MEMS devices, in marine
• sensing maybe attached to
• Ships
• Floating devices (buoys) in the sea
• Fixed sea structures (like oil rigs)
• Sea bed using links
• AUVs

• http//www.oceanor.no/images/oc-buoys.gif

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AUV ( Autonomous underwater vehicle )

• AUV
• http//isis2.admin.usf.edu/ur/usfmagazine/spring02
  /rip1.html
• Lab on a Chip

• AUVs are unmanned underwater vehicles for real
  time monitoring in the oceans.
• AUVs can be equipped with Lab on a Chip, a set
  of sensors developed on a single chip, using
  MEMS.
• These Lab on a Chip devices can sense a large
  number of chemical pollutants simultaneously.

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Mems in oil exploration and related applications

• To find potential oil reserves
• To detect oil leakage from pipelines
• In cases of unfortunate oil spills
• MEMS sensors can help to sense information about
  the ocean currents.
• Using this it is possible to predict how far the
  oil slick will be transported.
• This information can aid in clean up.

http//www.spiderstaging.com/rigging/images/offsho
re_oil.jpg
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Finding potential oil and gas reserves

• MEMS geophones and accelerometers can sense the
  vibrations sent up from the earths belly.
• An array of MEMS geophones are planted over a
  wide area on the seabed.
• Vibrations are intentionally produced on the
  ground surface using some techniques.
• The MEMS devices measure the reflection of these
  waves from different layers in the earths belly.
• These readings are then used to create a
  geological map, which indicates the size and
  location of the oil/gas reservoir.

• MEMS Accelerometer
• http//micron.me.dal.ca/CHIPS/penny_chip.jpg

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Role of mems in coastal weather monitoring

• MEMS sensors can provide vital information about
  wave pressure, temperature, tidal and current
  velocity (using devices like the MEMS Doppler
  current profiler).
• The information obtained can be used to develop
  maps indicating the distribution of these
  parameters throughout the ocean.
• These maps can provide accurate data, regarding
  any imminent sea storms, tsunamis (large sea
  waves caused due to large scale movements inside
  the earths surface).

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Hydrophones ))))

• Just as microphones collect sounds in air,
  hydrophones are small devices that detect sounds
  in water.
• The sources of sounds in water maybe ships,
  earthquakes, waves or marine animals.

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Digital mammal tags

• These are tiny devices attached to animals like
  whales, sharks, dolphins etc..
• Provides vital data about the animal and its
  surroundings
• A tag houses
• Pressure sensor(s)
• Temperature sensor(s)
• Hydrophone (sound sensor)
• Radio transmitter for data collection at remote
  locations.

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MEMS in marine military operations

• An array of MEMS sensors spread on the ocean
  floor could detect the presence of enemy
  submarines.
• MEMS sensors (pressure sensors, accelerometers
  etc.) are being used in anti-torpedo weapons on
  submarines and ships.
• MEMS sensors in torpedoes are responsible for
• Detonating the torpedo at the right time
• Hitting the target in a crowded environment
• Prevent any premature explosion

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Challenges for MEMS sensors in marine environment

• Complex nature of marine environment
• Fouling of sensor surfaces
• Selecting one out of several species
• Should be able to detect extremely low levels of
  chemical concentrations
• Resist drifting along with the currents

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Future of mems in marine science

• MEMS promises to be an effective technique of
  producing marine sensors of high quality, at
  lower costs.
• The use of fiber optics in marine science offers
  several avenues in fabrication and packaging of
  sensors.
• The use of sensor dust in the oceans in the
  coming years, would be the best that this
  technology could offer.

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The BIG question

• Is MEMS really necessary?
• Still in nascent stage to be applied
  commercially
• Research in this area is important, as it
  probably is the future

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Acknowledgements

• This effort is based upon work partially
  supported by the National Science Foundation
  under Grant No. 0239262 and The Florida Hi-Tech
  Corridor Workforce Training grant
• Any opinions, findings, and conclusions or
  recommendations expressed in this material are
  those of the author(s) and do not necessarily
  reflect the views of the National Science
  Foundation or the Florida HiTech Corridor
  Workforce Training Grant.

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