Measuring and testing – With fluid pressure – Porosity or permeability
Reexamination Certificate
2000-04-27
2002-08-20
Larkin, Daniel S. (Department: 2856)
Measuring and testing
With fluid pressure
Porosity or permeability
C073S031050
Reexamination Certificate
active
06435007
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sensor system that monitors agent breakthrough that occurs through what is otherwise intended to be a chemical barrier. This system detects and quantifies the occurrence of chemical breakthrough through a variety of analyte materials. Specific example applications include chemical suit materials and filter beds against chemical warfare agents. Military field deployments of this system can be imagined as well in the form of sensors in gas mask filter canisters. These “smart gas masks” may indicate imminent defeat of the mask as well as an all clear to indicate that it is safe to remove the mask again.
2. Description of the Prior Art
The most common system currently available for this detection purpose is a system designed to monitor fabric breakthrough using an impinger system as illustrated in a simplified view in
FIG. 1. A
piece of fabric is placed in a chamber so that it creates a seal. Carrier gas flows through the fabric when a pressure differential is created by a vacuum pump. A few drops of agent are placed on a piece of fabric. The agent eventually moves its way through the fabric carried by the carrier gas, where it is collected by mixing with a suitable solvent. A sample of the solvent is collected periodically and from the concentration of the agent in the solvent a breakthrough time can be calculated.
What is needed is a system that takes the guesswork out of the prior system and related technique by providing real time feedback on agent breakthrough.
SUMMARY OF THE INVENTION
The present invention is an agent breakthrough monitoring system that provides real-time feedback of when agent breakthrough occurs. The system operates around the performance of arrays of sensitive chemi-resistive semiconducting metal oxide (SMO) and/or polymer films. These films serve as the transduction media for the resistive and surface acoustic wave (SAW) sensor platforms. As the chemical compound that the material is being tested against breaks through the test material, it passes over the sensor elements in the array, resulting in changes in resistance (for the SMO sensors) and changes in frequency (for the polymer coated SAW sensors). The signatures from these changes will provide the information necessary to determine exposure levels as a function of time. Other types of suitable sensors include chemical field effect transistors, surface Plasmon resonance arrays, conducting polymer arrays, chemical hybrid sensor arrays, or any combination thereof. Such sensors must be reactive to changes in their surface conditions such that electrical signal outputs change with surface condition changes.
These and other advantages of the present invention will become apparent upon review of the following detailed description, the accompanying drawings, and the appended claims.
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Designation D 1776-98; “Standard Practice for Conditioning and Testing Textiles” American Society for Testing and materials, West Conshohocken, PA, 19428, reprinted from the Annual Book of ASTM Standards, Copyright ASTM.
Designation F1194-99; “Standard Guide for Documenting the Results of Chemical Permeation Testing of Materials Used in Protective Clothing”, American Society for Testing and materials, West Conshohocken, PA, 19428, reprinted from the Annual Book of ASTM Standards, Copyright ASTM.
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Designation F739-99a; “Standard Test Method for Resistance of Protective Clothing Materials to Permeation by Liquids or Gases Under Conditions of Continuous Contact”, American Society for Testing and materials, West Conshohocken, PA, 19428, reprinted from the Annual Book of ASTM Standards, Copyright ASTM.
F903-99a; “Standard Test Method for Resistance of Materials Used in Protective Clothing to Penetration by Liquids”, American Society for Testing and materials, West Conshohocken, PA, 19428, reprinted from the Annual Book of ASTM Standards, Copyright ASTM.
Hammond Jeremy
Mlsna Todd
Smith Dean
Atwood Pierce
Larkin Daniel S.
Sensor Research & Development Corporation
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