Sensor and sensor array having improved selectivity

• US 6,977,511 B2
• Filed: 03/08/2005
• Issued: 12/20/2005
• Est. Priority Date: 06/20/2002
• Status: Expired due to Term

• Current Assignee: Xsilogy, Inc. (Kratos Defense & Security Solutions Incorporated)
• Original Assignee: Xsilogy, Inc. (Kratos Defense & Security Solutions Incorporated)
• Inventors: Warmack, Robert J., Klaassen, Erno, Patel, Sanjay V., Mlsna, Todd E., Baselt, David R., Fruhberger, Bernd
• Primary Examiner(s): DEB, ANJAN K
• Application Number:
  US11/082,634
• Publication Number:
  US 20050164285A1
• Time in Patent Office: 287 Days
• Field of Search: 324658-664, 324/403.01, 324/403.02, 324/403.03, 324/403.04, 324/403.05, 324/403.06, 73/233.1, 73/310.2, 361/278, 361/280
• US Class Current: 324/661
• CPC Class Codes: G01N 27/227 Sensors changing capacitance upon adsorption or absorption of fluid components, e.g. electrolyte-insulator-semiconductor sensors, MOS capacitors G01N27/225 takes precedence

Abstract

A sensor for determining the presence of an analyte is disclosed comprising a reactive layer disposed between a base plate and a movable plate. The reactive layer is configured to interact with an analyte effecting a change in capacitance between the base plate and movable plate. When the analyte has a polarity or overall Hildebrand solubility parameter that is similar to the reactive layer, the change in capacitance is caused by a swelling of the reactive layer as analyte is absorbed into the reactive layer. This results in a decrease in capacitance. When the analyte has a solubility parameter not near the reactive layer, the absorbed analyte causes the reactive layer'"'"'s total polarity to increase, an effect that dominates swelling. This causes an increase in capacitance. A capacitive sensing circuit is included for measuring the change in capacitance which is indicative of the analyte exposed to the sensor.

Claims

1. A sensor array for sensing an airborne analyte, the sensor array comprising at least a first sensor and a second sensor, wherein at least the first sensor comprises:

a first conductive plate, which first conductive plate serves as a base plate;

a second conductive plate disposed in spaced relation to and in electrical communication with the first conductive plate, wherein at least a portion of the second conductive plate is moveable in relation to the first conductive plate;

a reactive layer disposed between at least a portion of the second conductive plate and the first conductive plate, the reactive layer being comprised of a polymer film comprised of at least one polymer species and configured to effect a change in capacitance between the second conductive plate and the first conductive plate when the reactive layer is exposed to the analyte; and

a capacitance sensing circuit for detecting a change in capacitance between the first conductive plate and the second conductive plate indicative of the presence of the analyte.

2. A sensor array according to claim 1 wherein the reactive layer of the first sensor is configured to selectively and reversibly absorb the analyte.

3. A sensor array according to claim 1 wherein the change in capacitance in the first sensor is due at least in part to a change in dielectric properties of the reactive layer caused by the analyte being absorbed into the reactive layer.

4. A sensor array according to claim 1 wherein the change in capacitance in the first sensor is due at least in part to a swelling of the reactive layer caused by the analyte being absorbed into the reactive layer.

5. A sensor array according to claim 1 wherein the reactive layer of the first sensor comprises a sol gel.

6. A sensor array according to claim 1 further comprising a readout circuit for displaying results from the sensor array.

7. A sensor array according to claim 1 further comprising a transmitter for transmitting data from the sensor array to a receiver positioned at a location remote from the sensor.

8. A sensor array according to claim 1 wherein the second conductive plate of the first sensor comprises a structure selected from the group consisting of a cantilever, a tethered moveable plate, and a flexible membrane.

9. A sensor array according to claim 8 wherein the second conductive plate of the first sensor is perforated to facilitate access of the analyte to the reactive layer.

10. A sensor array according to claim 1 wherein the analyte is selected from the group consisting of a volatile organic compound, a chemical warfare agent, and a biological warfare agent.

11. A sensor array according to claim 1 wherein the analyte is an emission gas.

12. A sensor array according to claim 1 wherein the polymer species of the first sensor that comprises the polymer film is a compound selected from the group consisting of polycarbonate, polyethylene, polyisobutylene, polypropylene, polystyrene, polyether urethane, ethyl cellulose, polydimethyl siloxane, silicone epoxy, polymethyl methacrylate, a polyamide, polyvinyl chloride, cellulose acteate, polyurethane, polyvinyl acetate, a polyimide, siloxanefluoroalcohol, and polyethylene-co-vinylacetate.

13. A sensor array according to claim 1 wherein each of the sensors comprises:

a first conductive plate, which first conductive plate serves as a base plate;

a second conductive plate disposed in spaced relation to and in electrical communication with the first conductive plate, wherein at least a portion of the second conductive plate is moveable in relation to the first conductive plate;

a reactive layer disposed between at least a portion of the second conductive plate and the first conductive plate, the reactive layer being comprised of a polymer film comprised of at least one polymer species and configured to effect a change in capacitance between the second conductive plate and the first conductive plate when the reactive layer is exposed to the analyte; and

a capacitance sensing circuit for detecting a change in capacitance between the first conductive plate and the second conductive plate indicative of the presence of the analyte.

14. A sensor array according to claim 13 wherein the reactive layer of each sensor differs from the reactive layers of the other sensors.

15. A sensor array according to claim 13 capable of detecting a plurality of airborne analytes.