Distributed Microsystems Laboratory: Developing Microsystems that Make Sense

1
Distributed Microsystems LaboratoryDeveloping
Microsystems that Make Sense
Portable Chemical Sensing Systems
Development Sponsoring Agency National Science
Foundation CAREER Award ECS-9996263 Period
of Award 6/97-5/01 PI D. Wilson Research
Assistants Sam McKennoch, Sean
Hoyt Collaborators Nate Lewis, Caltech Jiri
Janata, Georgia Tech
2
Distributed Microsystems LaboratoryDeveloping
Microsystems that Make Sense

• Goals To develop a proof-of-concept portable
  chemical sensing instrument that provides field
  portable, continuous monitoring of vapor-phase
  chemicals with the following features
• On-board sampling/airflow control
• Low power
• Use of human pattern recognition capability to
  decrease system power and false alarm rates
• small size, portable deployment
• self-diagnostic capability
• multi-stimulus detection
• without sacrificing stimulus recognition
  capability

3
Distributed Microsystems Laboratory Portable
Chemical Sensing Systems Development
Metal-oxide or Polymer (Maximally Diverse Broad
Selectivity Low-to-Moderate Precision
Vapor Sample
Incoming Airflow
Pre-concentrator
Heater Chemically Sensitive Coating
Incoming Airflow
Vapor Sample
Microcontroller Streamlined Pattern Recognition
(low-power)
4
Distributed Microsystems Laboratory Portable
Chemical Sensing Systems Development
Recovery Path
Response Path

• Array of 6 sensors is projected onto principal
  component space with on-board noise reduction.
• User can observe path that an unknown analyte
  travels to determine which analyte is present in
  the sensing environment.
• User-visual intervention reduces false alarms and
  provides more powerful pattern recognition in a
  low-power envelope.

Methanol Calibration Point
5
Distributed Microsystems Laboratory Portable
Chemical Sensing Systems Development

• Proof-of-concept Instrument
• (Interface)
• Discrete Sensors
• Discrete Processing Circuits
• PIC Microcontroller
• 4 9V Batteries
• Discrete version consumes a total system power of
  15W integrated version will reduce power
  consumption by one order of magnitude or more

6
Distributed Microsystems Laboratory Portable
Chemical Sensing Systems Development

• Proof-of-concept Instrument
• (Sensor Array)
• 6 metal-oxide sensors (discrete)
• Heater control circuits
• Sampling flow chamber
• Discrete version consumes a total system power of
  15W integrated version will reduce power
  consumption by one order of magnitude or more.

7
Distributed Microsystems Laboratory Portable
Chemical Sensing Systems Development

• Modular Sensor Interface Boards
• metal-oxide sensors (discrete)
• ChemFET sensors or
• composite Polymer sensors
• Up to 8 different types of sensors (16 total
  sensors) can be accommodated by the interface
  electronics
• Information from 2-8 sensors is projected onto
  two-dimensional space and calibration points for
  up to 24 analytes can be plotted on the user
  display.