Apparatus for sensing volatile organic chemicals in fluids
First Claim
1. An apparatus for sensing an analyte in a fluid, comprising:
- (a) a chemical preconcentrator further comprising a substrate, a sorptive material and a heating element both located on a thinned portion of the substrate, with the sorptive material acting to absorb or adsorb the analyte from the fluid over time, and with the heating element upon electrical activation releasing the analyte from the sorptive material in concentrated form; and
(b) at least one chemiresistor located proximate to the chemical preconcentrator and spatially separated therefrom and having an electrical resistance that changes in response to exposure to the concentrated analyte, thereby sensing the analyte.
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Accused Products
Abstract
A chemical-sensing apparatus is formed from the combination of a chemical preconcentrator which sorbs and concentrates particular volatile organic chemicals (VOCs) and one or more chemiresistors that sense the VOCs after the preconcentrator has been triggered to release them in concentrated form. Use of the preconcentrator and chemiresistor(s) in combination allows the VOCs to be detected at lower concentration than would be possible using the chemiresistor(s) alone and further allows measurements to be made in a variety of fluids, including liquids (e.g. groundwater). Additionally, the apparatus provides a new mode of operation for sensing VOCs based on the measurement of decay time constants, and a method for background correction to improve measurement precision.
85 Citations
33 Claims
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1. An apparatus for sensing an analyte in a fluid, comprising:
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(a) a chemical preconcentrator further comprising a substrate, a sorptive material and a heating element both located on a thinned portion of the substrate, with the sorptive material acting to absorb or adsorb the analyte from the fluid over time, and with the heating element upon electrical activation releasing the analyte from the sorptive material in concentrated form; and
(b) at least one chemiresistor located proximate to the chemical preconcentrator and spatially separated therefrom and having an electrical resistance that changes in response to exposure to the concentrated analyte, thereby sensing the analyte. - View Dependent Claims (2, 3, 4, 5, 10, 11, 13, 14, 15)
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6. An apparatus for sensing an analyte in a fluid, comprising:
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(a) a chemical preconcentrator formed on a substrate and further comprising, a sorptive material and a heating element both located on a thinned portion of the substrate, with the sorptive material acting to absorb or adsorb the analyte from the fluid over time, and with the heating element upon electrical activation releasing the analyte from the sorptive material in concentrated form; and
(b) at least one chemiresistor formed on the same substrate proximate to the chemical preconcentrator and spatially separated therefrom and having an electrical resistance that changes in response to exposure to the concentrated analyte, thereby sensing the analyte.
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7. An apparatus for sensing an analyte in a fluid, comprising:
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(a) a chemical preconcentrator further comprising a substrate, a sorptive material and a heating element both located on a thinned portion of the substrate, with the sorptive material acting to absorb or adsorb the analyte from the fluid over time, and with the heating element upon electrical activation releasing the analyte from the sorptive material in concentrated form; and
(b) at least one chemiresistor located proximate to the chemical preconcentrator on another substrate and having an electrical resistance that changes in response to exposure to the concentrated analyte, thereby sensing the analyte. - View Dependent Claims (8, 9)
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12. An apparatus for sensing an analyte in a fluid, comprising:
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(a) a chemical preconcentrator further comprising a substrate, a sorptive material and a heating element both located on a thinned portion of the substrate, with the sorptive material acting to absorb or adsorb the analyte from the fluid over time, and with the heating element upon electrical activation releasing the analyte from the sorptive material in concentrated form; and
(b) at least one chemiresistor located proximate to the chemical preconcentrator, with each chemiresistor comprising a chemiresistive material disposed between at least one pair of spaced-apart electrodes, with the chemiresistive material further comprising a plurality of electrically-conductive particles suspended in a polymer host material, with the electrically-conductive particles comprising 20-40 percent by volume of the chemiresistive material, and with each chemiresistor having an electrical resistance that chances in response to exposure to the concentrated analyte, thereby sensing the analyte.
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16. A chemical-sensing apparatus, comprising:
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(a) a chemical preconcentrator further comprising a substrate with a sorptive material being located on a thinned portion of the substrate for sorbing a chemical species of interest from a fluid over time and subsequently releasing the chemical species of interest upon heating of the sorptive material; and
(b) at least one chemiresistor located proximate to the chemical preconcentrator and spatially separated therefrom for sensing the chemical species upon heating of the sorptive material. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A method for increasing the sensitivity for detection of an analyte in a fluid using at least one chemiresistor, comprising steps for:
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(a) providing a sorptive material on a thinned portion of a substrate and sorbing the analyte from the fluid into the sorptive material; and
(b) heating the sorptive material in the proximity of the chemiresistor which is located on another substrate or beside the sorptive material on the same substrate and thereby generating a concentrated whiff of the analyte for detection by the chemiresistor. - View Dependent Claims (27, 28, 29, 30, 31, 32)
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33. A chemical-sensing apparatus, comprising:
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(a) a chemical preconcentrator having a sorptive material further comprising a polymer or sol-gel host material wherein activated charcoal or a carbon molecular sieve material is embedded, with the sorptive material sorbing a chemical species of interest from a fluid over time and subsequently releasing the chemical species of interest upon heating of the sorptive material; and
(b) at least one chemiresistor located proximate to the chemical preconcentrator for sensing the chemical species of interest upon heating of the sorptive material.
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Specification