Smart Dust & Its Applications

1. Smart Dust &Its Applications By PANKAJ SHARMA

2. OUTLINE • INTRODUCTION • ARCHITECTURE • MANUFACTURING • COMM. INTERFACE • SENSOR NETWORKS • APPLICATIONS • THE DARK SIDE • RESEARCH AREAS • CONCLUSION

3. INTRODUCTION • Technology developed at UCLA Berkeley college of Engg. • Small wireless devices designed to monitor all types of physical quantities such as: • Temperature • Humidity • Motion • Light Levels • Pollution etc. • Commercial name coined for dust size smart sensors.

4. INTRODUCTION POWER SUPPLY RECEIVER PROCESSOR TRANSMITTER • Level of Integration: Integrates • Transducers • Processors • Memories • Solar powered Batteries • Communication Interfaces on a single micro miniscule silicon chip. • Uses MEMS technology for its fabrication SENSORS

5. INTRODUCTION : Questions • What Are Sensors? A device that responds to a physical stimulus for eg. Heat Light, sound, pressure, motion, flow etc and produces a measurable Corresponding electrical signal is called a sensor. • What Are Smart Sensors? Sensors which not only have the capability to respond to a physical stimulus but also the ability to decide whether the data is useful or not.

6. Smart Sensors Programmable Decision Making Capability Self Calibrating Plug-n-Play Operation Sophisticated & Complex sensor systems are easy to design Traditional Sensors Not Programmable No processing power Custom Calibration Custom design Very difficult with traditional methods INTRODUCTION : Questions Why Smart Sensors?

7. Smart Sensors Distributed Measurements Possible Low Cost & Wide Availability Less Maintenance Cost Traditional Sensors Only Lumped measurements possible Relatively High Cost Requires skilled Professionals for repair job INTRODUCTION : Questions Why Smart Sensors?

8. ARCHITECTURE

9. Thin Film Battery • Size = 1x1x1mm^3 • Storage = 1 Joule • Material = Lithium ion • Low o/p resistance for sub milli-amp current

10. Power Capacitor • Size = 0.25x0.25x0.25mm^3 • Capacity = 1 micro joule • Material = Ceramic • Used to provide high current when needed for eg. For laser pulses

11. Solar Cell • Size = 1x1x0.1mm^3 • Generation Cap. = 1 joule/day/mm • Material = Photosensitive compounds • Used to power the smart dust unit

12. Controller • Size = 1x1x0.1mm^3 • Uses CMOS technology • Analog cum digital controller • Gives the dust mote the decision making capability

13. Sensors • Size = 0.5x0.5x0.1mm^3 • Incorporates many sensors on one interface • Micromachining techniques used for fabrication

14. Passive Transmitter Interrogating Laser Beam • Called Corner Cube Retro-reflector (CCR) • Size = 0.5x0.5x0.1mm^3 • Range =1Km • Speed = 100kbps • Modulates interrogating laser beam with the help of movable mirrors & transmits it

15. Active Transmitter • Size = 1x0.5x0.1mm^3 • Range = 10Km • Speed = 10Mbps • Uses laser diode to produce carrier beam.

16. Receiver • Size = 1x0.5x0.1mm^3 • Consists of photodetector and receiver circuitry • Demodulates the incoming signal and separates the useful information from carrier & noise

17. MANUFACTURING:Introduction to MEMS • These dust size particles are fabricated using MEMS technology. • MEMS devices dates way back to 1958 • 1st application was a Strain Gauge • Uses silicon as base material and etching techniques to generate pattern therein

18. MANUFACTURING:Introduction to MEMS • Combines two Technologies • IC fabrication Technology • Micromachining Technology • IC Fabrication :- used to etch electronic circuits on the silicon substrate • Micromachining :-used to etch mechanical patterns on the silicon substrate

19. MANUFACTURING: FabricationProcess MEMS Generic Process

20. MANUFACTURING: • Includes Two Types of Micromachining Processes • BULK MICROMACHINING • SURFACE MICROMACHINING

21. MANUFACTURING: • Bulk Micromachining • Wet chemicals are used to etch the pattern on silicon substrate. • Etchants used:- • Non Acidic:- • Potassium hydroxide (KOH) • Tetra methyl ammonium hydroxide (TMAH) • Ethylene Diamene Pyrocatechol (EDP) • Acidic:- • Hydroflouric Acidic • Nitric Acid

22. MANUFACTURING: • Bulk Micromachining • Process involves:- • Depositing masking Layers of:- • Silicon nitride or • Silicon dioxide or any • Metal like Au, Ti, etc. • Patterning these using Lithography

23. MANUFACTURING: • Bulk Micromachining • Pressure sensors & Accelerometers are fabricated using these technologies. • These devices include fabrication of peizo-resistors on one side of wafer and machining on the other side to form diaphragm or suspended mass in the case of pressure sensor or accelerometers respectively.

24. MANUFACTURING: Peizo-electric material • Bulk Micromachining • Pressure Sensor: • Accelerometer:

25. MANUFACTURING: 2. Surface Micromachining • More advanced technique to make Novel structures on surface of silicon wafer • Involves deposition of certain layers and patterning these using Lithographic And etching techniques.

26. MANUFACTURING: 2. Surface Micromachining • Mainly Three layers are employed: • Electrical layer: Conducts electrical signals to and from MEMS structure. • Structural layer: Forms The mechanical Body of MEMS. • Sacrificial layer: Serve the purpose of releasing the structural layers.

27. COMMUNICATION INTERFACE • System Design Options: • Must support half- or full-duplex, bi-directional communication between a central transceiver and up to 1000 dust motes. • The downlink (central transceiver to dust motes) must broadcast to all of the dust motes at a bit rate of several kbps. • The uplink (dust motes to central transceiver) must permit each of 1000 dust motes to convey about 1 kb of data within 1 s, an aggregate throughput of 1 Mbps.

28. COMMUNICATION INTERFACE • System Design Options: • Options for uplink multiplexing include time-, frequency-, code- and space-division multiplexing. • The central transceiver must be able to resolve the position of each dust mote with an angular resolution of the order of 1/100 of the field of view. • The link should operate over a range of at least several hundred meters.

29. COMMUNICATION INTERFACE • System Design Options: • The dust mote transceiver must occupy a volume of the order of 1 mm^3, and consume an average power not exceeding 1 mW. • If possible, the uplink and downlink should afford a low probability of interception

30. COMMUNICATION INTERFACE:Types • Radio Frequency Transmission (RFT) • Time Division MUX (TDMA) • Frequency Division MUX (FDMA) • Code Division MUX (CDMA) • Space Division MUX (SDMA) • Free Space Optical Transmission (FSOT) • Passive Transmission • Active Transmission

31. COMMUNICATION INTERFACE Why FSOT is preferred? • Pitfalls of RFT: • Problems with TDMA: • Requires each dust mote to coordinate its transmission with all the other dust motes. • Problems with FDMA: • requires accurate control of the dust-mote oscillator frequency

32. COMMUNICATION INTERFACE Why FSOT is preferred? • Pitfalls of RFT: • Problems with CDMA: • Requires high-speed digital circuitry to operate for a relatively extended time interval, potentially consuming excessive power. • In order to avoid coordination between dust motes, both FDMA and CDMA require individual dust motes to be preprogrammed with unique frequencies or codes

33. COMMUNICATION INTERFACE Why FSOT is preferred? • Pitfalls of RFT: • Problems with SDMA: • In SDMA, the central transceiver employs an antenna array to separate transmissions from different dust motes. Given the limited size of the central transceiver it would be difficult for SDMA to achieve the required spatial resolution.

34. COMMUNICATION INTERFACE Why FSOT is preferred? • Advantages of FSOT • Free-space optical transmission at visible or near-infrared wavelengths (400-1600 nm) represents an attractive alternative for the downlink and uplink. • In downlinking:- • A single laser transmitter can broadcast an on off-keyed signal to the collection of dust motes. • Each dust mote would be equipped with a very simple receiver consisting of a band pass optical filter, a photodiode, a preamplifier and a slicer. • This receiver would involve only low-speed base-band electronics, making it far simpler than its RF counterpart.

35. COMMUNICATION INTERFACE Why FSOT is preferred? • Advantages of FSOT • In uplinking:- • optics offers two alternatives for transmission. • Active laser-diode-based transmitter • Involves modulation of internally generated laser beam • Optically passive transmitter consisting of a corner-cube retro-reflector (CCR). • Involves modulation of external interrogating beam.

36. COMMUNICATION INTERFACE Lens Which One To Prefer? Adjustable Mirror Laser Diode • Active Transmitter: • Consumes a lot of power to generate the laser beam • Passive Transmitter: • Involves a corner cube retroreflector to modulate the interrogating beam from the central receiver. • Requires a lot less power than its active counterpart.

37. COMMUNICATION INTERFACE System Realization

38. DISTRIBUTED SENSOR NETWORKS • Consists of a Network backbone on which many nodes reside. • Nodes are classified as: • Sensor nodes:- tend to send data to the network • Controller nodes:- tend to gather data from the network • There can be more than one controller node. • Virtual network via internet can also be setup

39. DISTRIBUTED SENSOR NETWORKS Networked Smart Dust Sensors

40. DISTRIBUTED SENSOR NETWORKS • Controller Nodes: • Consists of: • Processor • Memory • Network Interface • I/O devices to communicate with the users • Used to: • Collect information from sensor nodes • Program the sensor nodes • Provide feedback to the user

41. DISTRIBUTED SENSOR NETWORKS • Advantages of Sensor Networks: • Plug-n-Play operation possible • No new wires to be routed to accommodate new nodes • Traditional sensors have varying gains, offsets, hysteresis, etc. which must be compensated for elsewhere in the system. A smart sensor node would store the physical attributes of the transducer and would compensate for non idealities locally in the processor.

42. DISTRIBUTED SENSOR NETWORKS THE IEEE 1451 PROTOCOL • It is an open standard that gives sensors makers a way to interface to different types of field buses • A standard transducer interface module (STIM) described by the standard includes: • sensor interface • signal conditioning and conversion • calibration • linearization and • basic communication rules

43. DISTRIBUTED SENSOR NETWORKS TEDS the Heart of IEEE 1451 Protocol • TEDS stands for Transducer Electronic Data Sheet. • Contains Technical information that: • identifies the sensor • specifies the sensor’s analog interface and • describes the sensor’s use • TEDS resides in the sensor in an inexpensive memory component, typically an EEPROM,

44. DISTRIBUTED SENSOR NETWORKS TEDS • Consists of four fields: • Basic TEDS • Standard TEDS • Calibration TEDS • User area • Contents vary according to the type of sensor

45. DISTRIBUTED SENSOR NETWORKS • Advantages of IEEE 1451 • Maximum Compatibility • Simple Adoption • Quicker, more automated system setup • Improved diagnostics and troubleshooting • Reduced downtime for sensor repair and replacement • Improved sensor data management, bookkeeping, and inventory management • Automated use of calibration data

46. APPLICATIONS • Military Applications • Battlefield surveillance • Detection • Classification & • Tracking of enemy vehicles. • Eg. DARPA SensIT Project

47. APPLICATIONS • Dust Particles can be spread by Unmanned Air Vehicles (UAVs) • Data can be collected by sending the same aircraft over that area

48. APPLICATIONS • VIRTUAL KEYBOARD • Glue some dust motes to your fingertips • Accelerometers will sense the orientation and motion of each of your fingertips, and talk to the computer in your watch • Then : • Sculpt 3D shapes in virtual clay • Play  the piano • Gesture in sign language and have the computer to translate • Combined with a MEMS augmented-reality heads-up display, your entire computer I/O would be invisible to the people around you. • Couple that with wireless access and you need never be bored in a meeting again!  Surf the web while the boss rambles on and on.

49. APPLICATIONS • INVENTORY CONTROL • The carton talks to the box • The box talks to the palette • The palette talks to the truck • The truck talks to the warehouse • and the truck and the warehouse talk to the internet. • Know where your products are and what shape they're in any time, anywhere.

50. APPLICATIONS • ENVIRONMENTAL APPLICATIONS • Habitat Monitoring • Eg ZebraNet(Princeton) • Weather sensing • Estuarine environmental and observation & forecasting system (EEOFS)