Chemical selective sensors utilizing admittance modulated membranes

• US 4,776,944 A
• Filed: 09/01/1987
• Issued: 10/11/1988
• Est. Priority Date: 03/20/1986
• Status: Expired due to Fees

• Current Assignee: Janata, Jiri, Michael Thompson, Robert J. Huber
• Original Assignee: Janata, Jiri, Michael Thompson, Robert J. Huber
• Inventors: Thompson, Michael, Janata, Jiri, Huber, Robert J.
• Primary Examiner(s): Niebling, John F.
• Assistant Examiner(s): Nguyen, Nam X.
• Application Number:
  US07/092,159
• Time in Patent Office: 406 Days
• Field of Search: 204/403, 204/435, 204/412, 204/415, 204/416, 204/418, 357/25, 435/817
• US Class Current: 204/403.08
• CPC Class Codes: G01N 27/4035 Combination of a single ion-sensing electrode and a single reference electrode G01N27/406 and G01N27/413 take precedence

Abstract

A chemical selective sensor system utilizes admittance modulated to detect the presence of chemicals or chemical species in a fluid. The sensor system includes a film or membrane adapted to pass ions when selected chemicals which are to be detected are present at the membrane surface. The membrane is attached to a hydrophilic layer of material which, in turn, is attached to a transformed layer which is deposited on a base substrate. When the selected chamicals are present in the fluid, the membrane interacts with the chemicals to allow ions, also in the fluid, to permeate the membrane. This ion current in the membrane is transformed or converted by the transformer layer to an electronic current which is measured by an electrical circuit coupled to the transformer layer of material. An alternating current source is coupled at one terminal to the transformer layer and to the measuring circuit, and at another terminal to a circuit return electrode.

Claims

1. An electrochemical sensor for selectively sensing chemical species of a fluid, said sensor consisting essentially of

a base substrate,

a conductor carried by the base substrate,

a first layer of material attached to the base substrate for producing and supplying electrical current across the boundary between the layer and the base substrate to the conductor in response to transport of ions of a certain species to the layer, where the magnitude of the electrical current produced is equal to the ionic current, said layer being comprised of a compound which includes said certain species,

a membrane attached to the first layer for transporting ions to the layer, said membrane including gating molecules which selectively interact with the chemical species which is to be detected to thereby allow ions in the fluid to permeate the membrane,

an alternating current source, one terminal of which is coupled by way of said conductor to the first layer,

an electrode coupled to the other terminal of the alternating current source, and

means coupled by way of said conductor to the first layer for detecting the electrical current produced by the first layer.

2. A sensor as in claim 1 further including a fluid impervious material formed about the first layer to prevent contact of the layer with fluid to which the sensor is exposed.

3. A sensor as in claim 1 further including an intermediate layer formed between the first layer and the membrane and comprised of a hydrophilic material.

4. A sensor as in claim 3 wherein said intermediate layer is comprised of a hydrogel material.

5. A sensor as in claim 4 wherein said intermediate layer is comprised of polyhema.

6. A sensor as in claim 4 wherein said intermediate layer is comprised of polyacrylamide.

7. A sensor as in claim 3 wherein said first layer is from about 4000 to 10,000 angstroms in thickness, and wherein said intermediate layer is about 10,000 angstroms in thickness.

8. A sensor as in claim 1 wherein said first layer comprises two sublayers of material, one of which is attached to the membrane and the other of which is electrically coupled to the alternating current source, said one sublayer including said compound.

9. A sensor as in claim 8 wherein said one sublayer is from about 2000 to 5000 angstroms in thickness, and wherein said other sublayer is from about 2000 to 5000 angstroms in thickness.

10. A sensor as in claim 8 wherein said one sublayer is comprised of silver chloride, and said other sublayer is comprised of silver.

11. A sensor as in claim 8 wherein said one sublayer is comprised of sodium tungsten bronze, and said other sublayer is comprised of a metal.

12. A sensor as in claim 11 wherein said electrode and said membrane are disposed adjacent to one another on the base substrate.

13. A sensor as in claim 1 wherein said membrane comprises a phospholipid Langmuir - Blodgett film made of phosphatidyl choline.

14. A sensor as in claim 1 wherein said membrane film is made of fatty acid.

15. A sensor as in claim 1 wherein said electrode and said detecting means are disposed on said base substrate.

16. A sensor as in claim 1 wherein said detecting means comprises

a differential current amplifier having first and second inputs, the first input being coupled to the first layer,

first impedance means coupled between said one terminal of the alternating current source and said first input of the differential current amplifier,

a reference sensor means for producing a reference electrical current and coupled to said second input of the differential current amplifier, and

second impedance means coupled between said one terminal of the alternating current source and said second input of the differential current amplifier.

17. A sensor as in claim 16 wherein said first impedance means comprises a variable resistor, and said second impedance means comprises a resistor.

18. A sensor as in claim 16 wherein said reference sensor means comprises

a second layer of material attached to the base substrate at a location spaced from the location of attachment of the first layer, said first and second layers being made of the same material, and

a second membrane attached to the second layer of material, said first mentioned membrane and said second membrane being made of the same material.

19. A solid state electrochemical sensor for selectively sensing chemical species in a fluid consisting essentially of

a base substrate,

a transformer layer of material attached to the base substrate for transforming ionic current received at the layer into electronic current for application across the boundary between the layer and the base substrate, said layer being comprised of a compound which includes said chemical species,

a plurality of membranes attached to the transformer layer and spatially separated from one another, each for transporting ions to the transformer layer and each including different gating molecules which selectively bind to different chemicals to be detected to thereby allow ions in the fluid to permeate the respective membrane.

an alternating current source, one terminals of which is coupled to the transformer layer,

an electrode coupled to the other terminal of the alternating current source, and

means coupled to the transformer layer for detecting the electronic current developed in the layer.

20. A solid state electrochemical sensor for selectively sensing chemical species in a fluid consisting essentially of

a base substrate,

a transformer layer of material attached to the base substrate for transforming ionic current of a certain species received at the layer into electronic current, said layer comprising a compound which includes said species,

a membrane attached to the transformer layer for transporting ions to the layer, said membrane including gating molecules at a plurality of spaced-apart locations on the membrane, where the gating molecules at each location selectively bind to different chemicals to be detected to thereby allow ions in the fluid to permeate the membrane at the respective location,

an alternating current source, one terminal of which is coupled to the transformer layer,

an electrode coupled to the other terminal of the alternating current source, and

means coupled to the transformer layer for receiving and detecting the electronic current developed in the layer.