Shekhar Bhansali
bhansali@eng.usf.edu
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.
Shekhar Bhansali
bhansali@eng.usf.edu
Sensors in our body
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Mechanoreceptors (feel)
Auditory system
Visual System
Olfactory System (Nose)
Shekhar Bhansali
bhansali@eng.usf.edu
What can be sensed?
Almost Everything!!!
Commonly sensed parameters are :
• Pressure
• Temperature
• Flow rate
• Radiation
• Chemicals
• Pathogens
Shekhar Bhansali
bhansali@eng.usf.edu
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 !!!!
Shekhar Bhansali
bhansali@eng.usf.edu
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 !!
Shekhar Bhansali
bhansali@eng.usf.edu
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.
Shekhar Bhansali
bhansali@eng.usf.edu
Same game, different names
• USA – MEMS
• Europe – Microsystem technology
• Japan - Micromachines
Shekhar Bhansali
bhansali@eng.usf.edu
But why mems for sensors?
Sensors made using MEMS are better than
their conventional counterparts because they are :
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•
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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 !!!!
Shekhar Bhansali
bhansali@eng.usf.edu
Projected MEMS Market Share 2006
Consumer 3%
Medical 11%
Industrial 22%
Automotive 17%
Communictions
21%
Computer 26%
http://www.memsindustrygroup.org/industy_statistics.asp
Shekhar Bhansali
bhansali@eng.usf.edu
MEMS Revenue
http://www.memsindustrygroup.org/industy_statistics.asp
Shekhar Bhansali
bhansali@eng.usf.edu
Market for Sensors
• Auto Industry
• Medical industry
• Department of Defense
Shekhar Bhansali
bhansali@eng.usf.edu
Types of Sensors
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Mechanical Sensors
Optical Sensors
Thermal Sensors
Chemical and Biological Sensors
Shekhar Bhansali
bhansali@eng.usf.edu
Mechanical Micro sensors
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Strain Gauges
Accelerometers
Gyroscopes (Rotation rate)
Pressure Sensors
Microphones
Tactile Sensors (sensory feedback)
Biological Sensors (cochlear implants)
Shekhar Bhansali
bhansali@eng.usf.edu
ACCELEROMETERS
Used in deploying airbags, navigation,
activity detection for pacemakers
Shekhar Bhansali
bhansali@eng.usf.edu
Sensors in automobiles
http://mems.colorado.edu/c1.res.ppt/ppt/g.tutorial/ppt.htm
Shekhar Bhansali
bhansali@eng.usf.edu
Size is important in
automotive industry
Accelerometer
www.kineticceramics.com/products/ new_products.htm
Shekhar Bhansali
bhansali@eng.usf.edu
Comparison between conventional
and MEMS based inertial sensor
Mass
Size
Power
Cost
Conventional
1587.5 gm
15x8x5 cm
35 W
$20,000
MEMS based
10 gm
2x2x0.5 cm
~1mW
$500
Adapted from : http://mems.colorado.edu/c1.res.ppt/ppt/g.tutorial/ppt.htm
Shekhar Bhansali
bhansali@eng.usf.edu
MEMS based cochlear implant
http://www.accessexcellence.org/AB/BA/biochip3.html
Shekhar Bhansali
bhansali@eng.usf.edu
Optical Sensors
• Direct Sensors
(Light → Electronic Signal)
– Photoemissive
– Photoconductive
• Indirect Sensors
(Light → Intermediate energy → Electronic signal)
– Pyroelectric detectors
– Bolometers
• Biological Light Sensors
Shekhar Bhansali
bhansali@eng.usf.edu
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/2002/mat-hem/blindsee.html
Shekhar Bhansali
bhansali@eng.usf.edu
Thermal Sensors
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Thermo mechanical (dimension)
Thermo resistive (resistance)
Acoustic (sound)
Biological
Shekhar Bhansali
bhansali@eng.usf.edu
Features of MEMS thermal
sensors
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Waterproof
Contact free (wireless)
Find use in household appliances (iron)
Can be used in tight ends
Shekhar Bhansali
bhansali@eng.usf.edu
Chem Bio Sensors
• Electronic nose can
sense a large
number of gases
http://www.estcal.com/Products.html
• Electronic tongue
can sense a variety
of liquids
http://www.alpha-mos.com/proframe.htm
Shekhar Bhansali
bhansali@eng.usf.edu
Chemical lab on a chip
Used to detect chemicals in gas, liquids and
DNA
http://www.sandia.gov/media/NewsRel/NR2000/labchip.htm
Shekhar Bhansali
bhansali@eng.usf.edu
Medical and homeland
security applications
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Biocavity laser
Decontamination foam
Smart pill
Sensors for missile systems
Shekhar Bhansali
bhansali@eng.usf.edu
Biocavity laser
This device distinguishes cancerous from non
cancerous cells thus aiding the surgeons in
operations
http://www.sandia.gov/media/NewsRel/NR2000/candetec.htm
Shekhar Bhansali
bhansali@eng.usf.edu
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
Shekhar Bhansali
bhansali@eng.usf.edu
Smart PILL
• Implanted in the body
• Automatic drug delivery (on demand)
http://mmadou.eng.uci.edu/
Shekhar Bhansali
bhansali@eng.usf.edu
MEMS and Marine
Science
Shekhar Bhansali
bhansali@eng.usf.edu
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
Shekhar Bhansali
bhansali@eng.usf.edu
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
Shekhar Bhansali
bhansali@eng.usf.edu
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, water’s ability to hold dissolved oxygen
decreases as water temperature increases….
Now, this is really crucial for aquatic life !!
Shekhar Bhansali
bhansali@eng.usf.edu
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
Shekhar Bhansali
bhansali@eng.usf.edu
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
Shekhar Bhansali
bhansali@eng.usf.edu
AUV ( Autonomous underwater vehicle )
AUV
• 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.
http://isis2.admin.usf.edu/ur/usfmagazine/spring02/rip1.html
“ Lab on a Chip”
• These “Lab on a Chip” devices
can sense a large number of
chemical pollutants
simultaneously.
www.sandia.gov/media/ chemclue.htm
Shekhar Bhansali
bhansali@eng.usf.edu
Mems in oil exploration and related applications
• To find potential oil reserves
• To detect oil leakage from
pipelines
• In cases of unfortunate oil
spills
http://www.spiderstaging.com/rigging/images/offshore_oil.jpg
– 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.
Shekhar Bhansali
bhansali@eng.usf.edu
Finding potential oil and gas reserves
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MEMS geophones and accelerometers can
sense the vibrations sent up from the earth’s
belly.
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An array of MEMS geophones are planted over a
wide area on the seabed.
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Vibrations are intentionally produced on the
ground surface using some techniques.
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The MEMS devices measure the reflection of
these waves from different layers in the earth’s
belly.
MEMS Accelerometer
http://micron.me.dal.ca/CHIPS/penny_chip.jpg
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These readings are then used to create a
geological map, which indicates the size and
location of the oil/gas reservoir.
Shekhar Bhansali
bhansali@eng.usf.edu
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 earth’s
surface).
Shekhar Bhansali
bhansali@eng.usf.edu
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.
Shekhar Bhansali
bhansali@eng.usf.edu
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.
Shekhar Bhansali
bhansali@eng.usf.edu
MEMS in marine military operations
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An array of MEMS sensors spread on the ocean floor could detect the
presence of enemy submarines.
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MEMS sensors (pressure sensors, accelerometers etc.) are being used in
anti-torpedo weapons on submarines and ships.
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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
Shekhar Bhansali
bhansali@eng.usf.edu
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
Shekhar Bhansali
bhansali@eng.usf.edu
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.
Shekhar Bhansali
bhansali@eng.usf.edu
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
Shekhar Bhansali
bhansali@eng.usf.edu
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.
Shekhar Bhansali
bhansali@eng.usf.edu
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Shekhar Bhansali
bhansali@eng.usf.edu