Description: The Naval Research Laboratory (NRL) has developed a microfabricated preconcentrator called the Cascade Avalanche Sorbent Plate ARray, or CASPAR, to augment trace detection of hazardous chemicals including explosives, chemical warfare agents, toxic industrial chemicals, and narcotics. At the heart of CASPAR is a microfabricated hotplate device, comprising a sorbent-coated perforated membrane supported across a silicon frame. The minimal pressure drop across the device enables high collection airflows. Typical operations are achieved at 0.5–2 l/min but flows in excess of 200 l/min have been demonstrated. The flow-through chip design maximizes contact between the target analyte and the sorbent surface. Multiple plates can be stacked to achieve greater collection efficiencies. After exposure/absorption, the device is rapidly heated (in tens of milliseconds) to deliver a concentrated pulse of analyte to a detector system. Temperature ramping of CASPAR can also be used to achieve simple separations of collected analytes. The device may be integrated with a detector to enhance sensitivity and selectivity in near real-time or used as a stand-alone device that can be connected to a detector for analysis later.

Advantages/Features Include:

  • Sensitive: Up to 3 orders of magnitude detector signal enhancement for chemical warfare agents and explosives
  • Selective: Ignores undesirable vapors, such as diesel fuels, for improved detector selectivity
  • High collection airflows: >200 l/min has been demonstrated
  • Low pressure differential: 0.15 mm Hg
  • Low power consumption: 0.03 Joules/analysis cycle
  • Rapid: Minimum desorption time with no purge cycle required
  • Robust operation: > 3 million thermal cycles has been demonstrated in ambient air

Applications Include:

  • Military
  • Environmental monitoring, including workplace
  • Homeland security
  • Law enforcement


  • "CASPAR, A Microfabricated Preconcentrator for Enhanced Detection of Chemical Agents and Explosives," Proceedings of Eurosensors XX (2006) T1A-03.
  • "Towards Enhanced Detection of Chemical Agents: Design and Development of a Microfabricated Preconcentrator," Proceedings of the 14th International Conference on Solid-State Sensors, Actuators, and Microsystems (2007) 2291-2294.

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