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Role of MEMS in Sensors - MEMS _ Microsystems _ USF

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Role of MEMS in Sensors - MEMS _ Microsystems _ USF Powered By Docstoc
					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
•   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 :

•   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




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




                        Shekhar Bhansali   bhansali@eng.usf.edu
     Mechanical Micro sensors
•   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

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




                       Shekhar Bhansali   bhansali@eng.usf.edu
    Features of MEMS thermal
             sensors
•   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
•   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,
                                  Dissolved gases
pressure, light
                                  (like oxygen),
transmission,
                                  pH, metals,
tidal and current
                                  pesticides
velocity




                                  Seabed
Plant pigments
                                  characteristics,
(chlorophyll),
                                  Seismic signal
plankton cells


                    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        http://isis2.admin.usf.edu/ur/usfmagazine/spring02/rip1.html


  chip, using MEMS.
                                                    “ 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
                                                                   – MEMS sensors can help to
                                                                     sense information about the
                                                                     ocean currents.
                                                                   – Using this it is possible to
                                                                     predict how far the oil slick will
http://www.spiderstaging.com/rigging/images/offshore_oil.jpg         be transported.
                                                                   – This information can aid in
                                                                     clean up.


                                                                  Shekhar Bhansali     bhansali@eng.usf.edu
    Finding potential oil and gas reserves
•   MEMS geophones and accelerometers can                         MEMS Accelerometer
    sense the vibrations sent up from the earth’s
    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 earth’s
    belly.
                                                        http://micron.me.dal.ca/CHIPS/penny_chip.jpg

•   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




•   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

                                           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

				
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