Sensor and sensor array having improved selectivity

• US 20050164285A1
• Filed: 03/18/2005
• Published: 07/28/2005
• Est. Priority Date: 06/20/2002
• Status: Active Grant

• Current Assignee: Bernd Fruhberger, David R. Baselt, Erno Klaassen, Robert J. Warmack, Sanjay V. Patel, Todd E. Mlsna
• Original Assignee: Bernd Fruhberger, David R. Baselt, Erno Klaassen, Robert J. Warmack, Sanjay V. Patel, Todd E. Mlsna
• Inventors: Warmack, Robert J., Klaassen, Erno, Patel, Sanjay V., Mlsna, Todd E., Baselt, David R., Fruhberger, Bernd
• Granted Patent: US 6,977,511 B2
• Time in Patent Office: Days
• US Class Current: 435/6
• 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

1-32. -32. (canceled)

33. 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.

34. A sensor array according to claim 33 wherein the reactive layer of the first sensor is configured to selectively and reversibly absorb the analyte.

35. A sensor array according to claim 33 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.

36. A sensor array according to claim 33 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.

37. A sensor array according to claim 33 wherein the reactive layer of the first sensor comprises a sol gel.

38. A sensor array according to claim 33 further comprising a readout circuit for displaying results from the sensor array.

39. A sensor array according to claim 33 further comprising a transmitter for transmitting data from the sensor array to a receiver positioned at a location remote from the sensor.

40. A sensor array according to claim 33 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.

41. A sensor array according to claim 40 wherein the second conductive plate of the first sensor is perforated to facilitate access of the analyte to the reactive layer.

42. A sensor array according to claim 33 wherein the analyte is selected from the group consisting of a volatile organic compound, a chemical warfare agent, and a biological warfare agent.

43. A sensor array according to claim 33 wherein the analyte is an emission gas.

44. A sensor array according to claim 33 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.