Chemical selective sensors utilizing admittance modulated membranes

Claim 2

An electrochemical sensor for selectively sensing chemical species in a fluid, said sensor comprising a base substrate, a first layer of material attached to the base substrate for producing electrical current in response to transport of ions to the layer, where the magnitude of the electronic current produced is equal to the ionic current, 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 to the first layer, an electrode coupled to the other terminal of the alternating current source, and means coupled to the first layer for detecting the electrical current produced by the first layer.

Claim 3

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.

Claim 4

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.

Claim 5

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

Claim 6

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

Claim 7

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

Claim 8

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.

Claim 9

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 the material of which the ions are composed.

Claim 10

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.

Claim 11

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

Claim 12

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.

Claim 13

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

Claim 14

The above and other objects, features and advantages of the invention will become apparent from a consideration of the following detailed description presented in connection with the accompanying drawings in which: FIG. 1 shows a schematic view of a chemical selective sensor system including an amplifier circuit, made in accordance with the principles of the present invention; FIG. 2 shows a side, cross-sectional view of the active sensor electrode of the FIG. 1 schematic; FIG. 3 is a perspective, representational view of a multisensor embodiment made in accordance with the principles of the present invention; and FIG. 4 is a perspective, representational view of a different multisensor embodiment.

Claim 15

The above and other objects, features and advantages of the invention will become apparent from a consideration of the following detailed description presented in connection with the accompanying drawings in which: FIG. 1 shows a schematic view of a chemical selective sensor system including an amplifier circuit, made in accordance with the principles of the present invention; FIG. 2 shows a side, cross-sectional view of the active sensor electrode of the FIG. 1 schematic; FIG. 3 is a perspective, representational view of a multisensor embodiment made in accordance with the principles of the present invention; and FIG. 4 is a perspective, representational view of a different multisensor embodiment.

Claim 16

Referring now to the drawings:

Claim 17

Referring now to the drawings:

Claim 18

Referring to FIG. 1, there is shown a chemical selective sensor system which includes an active sensor electrode 4 and a reference sensor electrode 8, both coupled to the inputs of a differential amplifier 12. The active sensor electrode 4, which will be discussed in detail later, develops a change in electrical current in response to the presence of certain materials or chemical species in a fluid 16 (held. in a container 18) into which the sensor electrode is immersed. The reference electrode 8 develops a current (which may be substantially zero) as a reference against which the current developed by the active sensor electrode may be compared. Although the two electrodes 4 and 8 are shown as being separate, it should be understood that they could be constructed on the same solid state substrate as could the associated circuitry.

Claim 19

Referring to FIG. 1, there is shown a chemical selective sensor system which includes an active sensor electrode 4 and a reference sensor electrode 8, both coupled to the inputs of a differential amplifier 12. The active sensor electrode 4, which will be discussed in detail later, develops a change in electrical current in response to the presence of certain materials or chemical species in a fluid 16 (held. in a container 18) into which the sensor electrode is immersed. The reference electrode 8 develops a current (which may be substantially zero) as a reference against which the current developed by the active sensor electrode may be compared. Although the two electrodes 4 and 8 are shown as being separate, it should be understood that they could be constructed on the same solid state substrate as could the associated circuitry.

Claim 20

The active sensor electrode input of the differential amplifier 12 is also coupled by way of a variable resistor 20 to one side of an alternating current source 24. The reference electrode input of the differential amplifier 12 is coupled by way of a resistor 28 also to the one side of the alternating current source 24. This configuration is a well known bridge differential amplifier circuit. The output of the differential amplifier 12 is coupled to a detection circuit 32 for detecting the level of the output of the amplifier. For example, the detection circuit 32 could be any conventional voltmeter.

Claim 21

The active sensor electrode input of the differential amplifier 12 is also coupled by way of a variable resistor 20 to one side of an alternating current source 24. The reference electrode input of the differential amplifier 12 is coupled by way of a resistor 28 also to the one side of the alternating current source 24. This configuration is a well known bridge differential amplifier circuit. The output of the differential amplifier 12 is coupled to a detection circuit 32 for detecting the level of the output of the amplifier. For example, the detection circuit 32 could be any conventional voltmeter.

Claim 22

To complete the circuit from the alternating current source 24 through the fluid 16 to the active sensor electrode 4, a return electrode 36 is provided and this electrode is coupled to the other side of the alternating current source 24. The return electrode 36 could be made of any type of electrical conductive material such as platinum, a silver/silver chloride compound, etc.

Claim 23

To complete the circuit from the alternating current source 24 through the fluid 16 to the active sensor electrode 4, a return electrode 36 is provided and this electrode is coupled to the other side of the alternating current source 24. The return electrode 36 could be made of any type of electrical conductive material such as platinum, a silver/silver chloride compound, etc.

Claim 24

The active sensor electrode 4 and reference electrode 8 are both encapsulated in a fluid impervious coat 40 and 44 respectively so that the fluid 16 contacts the electrodes only through exposed windows 48 and 52. That is, only the outermost layer of each of the electrodes is exposed to the fluid 16.

Claim 25

The active sensor electrode 4 and reference electrode 8 are both encapsulated in a fluid impervious coat 40 and 44 respectively so that the fluid 16 contacts the electrodes only through exposed windows 48 and 52. That is, only the outermost layer of each of the electrodes is exposed to the fluid 16.

Claim 26

The active sensor electrode 4 of FIG. 1 is shown in a side, cross-sectional view in FIG. 2 in a representative fashion. That is, the thicknesses shown for the different layers is exaggerated for purposes of illustration. The active sensor electrode includes a base substrate 60 upon which the other layers of the sensor are deposited and upon which the electrical components are placed. Attached to the base substrate 60 is a transformer or convertor double layer 64 . including an electronic conductor layer of material 64a and a second layer of material 64b. The function of the transformer layer 64 is to convert ionic current, i.e., ions received at the outer surface of the second layer 64b, into electronic current which is applied to an electrical conductor 76 which extends through the base substrate 60 to the metal layer 64a. The layer 64b is a compound capable of both ionic and electronic conduction and capable of exchanging ions with adjacent layers. For example, layer 64a could be silver and layer 64b could be silver chloride. Alternatively, layer 64a could be lead and layer 64b could be lead chloride. It should be mentioned at this point that the chemical or material to be detected is not the ion which will be transported to layer 64b. Rather, such ions are simply the mechanism for determining when the material to be detected is present in the fluid 16. Such material triggers the active sensor electrode to allow the ions in the solution to be transported to the layer 64b. This will be further explained later.

Claim 27

The active sensor electrode 4 of FIG. 1 is shown in a side, cross-sectional view in FIG. 2 in a representative fashion. That is, the thicknesses shown for the different layers is exaggerated for purposes of illustration. The active sensor electrode includes a base substrate 60 upon which the other layers of the sensor are deposited and upon which the electrical components are placed. Attached to the base substrate 60 is a transformer or convertor double layer 64 . including an electronic conductor layer of material 64a and a second layer of material 64b. The function of the transformer layer 64 is to convert ionic current, i.e., ions received at the outer surface of the second layer 64b, into electronic current which is applied to an electrical conductor 76 which extends through the base substrate 60 to the metal layer 64a. The layer 64b is a compound capable of both ionic and electronic conduction and capable of exchanging ions with adjacent layers. For example, layer 64a could be silver and layer 64b could be silver chloride. Alternatively, layer 64a could be lead and layer 64b could be lead chloride. It should be mentioned at this point that the chemical or material to be detected is not the ion which will be transported to layer 64b. Rather, such ions are simply the mechanism for determining when the material to be detected is present in the fluid 16. Such material triggers the active sensor electrode to allow the ions in the solution to be transported to the layer 64b. This will be further explained later.

Claim 28

Attached to the transformer layer 64 is a layer of hydrophilic material 68, such as a hydrogel material, e.g., polyhema (poly[hydroxyethyl methacrylate], polyacrylamide, etc. The function of this layer is to provide a stable hydration environment to enable

Claim 29

Attached to the transformer layer 64 is a layer of hydrophilic material 68, such as a hydrogel material, e.g., polyhema (poly[hydroxyethyl methacrylate], polyacrylamide, etc. The function of this layer is to provide a stable hydration environment to enable