Role of MEMS in sensors

1. Role of MEMS in sensors

2. 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.

3. Sensors in our body • Mechanoreceptors (feel) • Auditory system • Visual System • Olfactory System (Nose)

4. What can be sensed? Almost Everything!!! Commonly sensed parameters are : • Pressure • Temperature • Flow rate • Radiation • Chemicals • Pathogens

5. What is MEMS ? • MEMS orMicroElectro Mechanical Systemsis 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 !!!!

6. 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 !!

7. 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.

8. Same game, different names • USA – MEMS • Europe – Microsystem technology • Japan - Micromachines

9. 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 !!!!

10. Projected MEMS Market Share 2006 http://www.memsindustrygroup.org/industy_statistics.asp

11. MEMS Revenue http://www.memsindustrygroup.org/industy_statistics.asp

12. Market for Sensors • Auto Industry • Medical industry • Department of Defense

13. Types of Sensors • Mechanical Sensors • Optical Sensors • Thermal Sensors • Chemical and Biological Sensors

14. Mechanical Micro sensors • Strain Gauges • Accelerometers • Gyroscopes (Rotation rate) • Pressure Sensors • Microphones • Tactile Sensors (sensory feedback) • Biological Sensors (cochlear implants)

15. ACCELEROMETERS Used in deploying airbags, navigation, activity detection for pacemakers

16. Sensors in automobiles http://mems.colorado.edu/c1.res.ppt/ppt/g.tutorial/ppt.htm

17. Size is important in automotive industry Accelerometer www.kineticceramics.com/products/ new_products.htm

18. 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

19. MEMS based cochlear implant http://www.accessexcellence.org/AB/BA/biochip3.html

20. Optical Sensors • Direct Sensors (Light → Electronic Signal) • Photoemissive • Photoconductive • Indirect Sensors (Light → Intermediate energy → Electronic signal) • Pyroelectric detectors • Bolometers • Biological Light Sensors

21. 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

22. Thermal Sensors • Thermo mechanical (dimension) • Thermo resistive (resistance) • Acoustic (sound) • Biological

23. Features of MEMS thermal sensors • Waterproof • Contact free (wireless) • Find use in household appliances (iron) • Can be used in tight ends

24. 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

25. Chemical lab on a chip Used to detect chemicals in gas, liquids and DNA http://www.sandia.gov/media/NewsRel/NR2000/labchip.htm

26. Medical and homeland security applications • Biocavity laser • Decontamination foam • Smart pill • Sensors for missile systems

27. 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

28. 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

29. Smart PILL • Implanted in the body • Automatic drug delivery (on demand) http://mmadou.eng.uci.edu/

30. MEMS and Marine Science

31. 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

32. Temperature, pressure, light transmission, tidal and current velocity Plant pigments (chlorophyll), plankton cells Dissolved gases (like oxygen), pH, metals, pesticides Seabed characteristics, Seismic signal Parameters monitored in marine science

33. 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 !!

34. 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

35. Where are these mems devices attached ? http://www.oceanor.no/images/oc-buoys.gif 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

36. AUV ( Autonomous underwater vehicle ) • 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. AUV http://isis2.admin.usf.edu/ur/usfmagazine/spring02/rip1.html “ Lab on a Chip” www.sandia.gov/media/ chemclue.htm

37. 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/offshore_oil.jpg

38. Finding potential oil and gas reserves • MEMS geophones and accelerometers can 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. • 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

39. 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).

40. 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.

41. 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.

42. 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

43. 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

44. 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.

45. 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

46. 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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