JPH07167834A - Solid oxygen sensor - Google Patents

Abstract

PURPOSE:To make the prolongation of a storage life possible, by filling up gaps between a plurality of metal electrodes and gaps between them and gas penetration films with a dried residue of a hydrophilic high polymer in which a electrolyte is dispersed. CONSTITUTION:Silicon dioxide 2 is formed on a silicon substrate 1, and thereon a platinum cathode 3 and a silver anode 4 are formed in fixed shapes by using phtoolithography. A hydrophilic high polymer and an electrolyte are dissolved in a solvent, the cathode 3 and the anode 4 are covered, the evaporation thereof to dryness is made, and a dried solid high polymer film 5 is made. A gas penetration film 16 is formed by covering the high polymer film 5 and fixed by epoxy resins 7. As the hydrophilic high polymer for the high polymer film 5, for example, polyvinyl alcohol, agarose or polyacrylamide is used, and as the electrolyte, a halide of alkali metal and a buffer solution are used. Thus, the sensor can be made easier than a sensor using an electrolytic solution and electrolytic gel, because the solid high polymer film 5, in which the electrolyte is dispersed, is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen sensor for measuring oxygen partial pressure in blood, and more particularly to a small solid oxygen sensor which can be manufactured at low cost and has excellent stability and shelf life.

[0002]

2. Description of the Related Art An oxygen sensor in which a cathode and an anode are formed by using a photolithography technique and coated with a gas permeable film of silicon rubber together with an internal electrolyte is disclosed in "Sensors and Actuators, 9 (1986), p. 258 (Sensors and Actuators, 9 (1986) pp249
-258) ". This oxygen sensor is a two-electrode type sensor including a silver cathode and a silver / silver chloride anode (reference electrode), and includes a hydrophilic polymer gel layer and a silicone rubber layer. Since the water content in the electrolytic solution of the polymer gel layer evaporates during storage, the polymer gel in which the electrolytic solution is immersed is filled at the time of use. Therefore, it cannot be stored in a measurable state for a long time. In the state filled with polymer gel,
Withstands continuous use for several days.

[0003]

In the above-mentioned prior art, since the polymer gel in which the electrolytic solution is immersed is used, it is difficult to miniaturize it, and the gas permeable membrane formation method, the polymer gel encapsulation method, etc. Since the manufacturing method is difficult, no consideration was given to price reduction. Further, when the oxygen sensor according to the above conventional technique is stored, there is a problem that the storage life is short because water is evaporated through the gas permeable film. The purpose of the present invention is to
An object of the present invention is to provide a small oxygen sensor that solves such problems, has a long shelf life, and can be manufactured at low cost.

[0004]

In order to achieve the above object, the solid oxygen sensor of the present invention has a hydrophilic property in which an electrolyte is dispersed between a plurality of metal electrodes, and between the plurality of metal electrodes and a gas permeable membrane. It is characterized by filling with a dry residue of the polymer (5 in FIG. 1).

[0005]

In the present invention, when the standard solution or the sample solution is brought into contact with the gas permeable membrane, moisture is diffused in the gas permeable membrane and absorbed by the dry residue of the hydrophilic polymer. The hydrophilic polymer that has absorbed water is gelated, and the dispersed electrolyte is ionized to increase the conductivity. On the other hand, when a constant voltage is applied between the metal electrodes, oxygen molecules diffused in the gas permeable membrane and the hydrophilic polymer layer from the sample are reduced on the metal electrodes and a reduction current flows to operate the oxygen sensor. . When additives such as ethylene glycol, polyethylene glycol, and glycerin are added to the above hydrophilic polymer, the water retention capacity increases, and the time for the hydrophilic polymer to equilibrate with water is shortened. It becomes possible. The hydrophilic polymer is in a dry state until the sample solution or standard solution comes into contact with the gas permeable membrane, and can be handled as a solid polymer membrane. Therefore, the structure of the oxygen sensor can be simplified and a sensor having an arbitrary shape can be easily manufactured, which is effective in reducing the cost of the sensor and can be disposable. In particular, it is suitable for manufacturing a small oxygen sensor by semiconductor technology. Further, since the hydrophilic polymer is in a dry state before the sensor is used, the water content in the electrolytic solution does not evaporate during storage unlike the prior art, and the storage life can be dramatically improved.

[0006]

EXAMPLES The present invention will be described in detail below with reference to examples. FIG. 1 is a configuration diagram of a two-electrode type solid oxygen sensor according to the first embodiment of the present invention. In FIG. 1, (a)
Is a perspective view of the sensor before the hydrophilic polymer and the gas permeable film are formed, (b) is a perspective view of the sensor after the hydrophilic polymer and the gas permeable film are formed, and (c) is ll of (b). It is a sectional view taken along the line '. In this example, silicon dioxide 2 was formed on a silicon substrate 1, a platinum cathode 3 and a silver anode 4 were formed on the silicon dioxide, and processed into a predetermined shape by a photolithography technique. A hydrophilic polymer and an electrolyte dissolved in a solvent are formed by coating the cathode 3 and the anode 4, and the solvent is evaporated to form a dry solid polymer film 5. A gas permeable film 6 is formed by covering the solid polymer film 5 and fixed with an epoxy resin 7. In addition, the electrodes 3 and 4 of the present embodiment
Although platinum and silver were used, two or three may be selected from platinum, gold, silver, and lead. As a processing method, a method of processing into a rod shape, or vacuum deposition, sputtering, or a screen printing method may be used depending on a formation location to form a film. The hydrophilic polymer used for the dry solid polymer film 5 may be selected from the group consisting of polyvinyl alcohol, agarose, polyacrylamide, hydroxyethyl polymethacrylate, and polyethylene oxide. In this case, ethylene glycol for moisturizing,
It is only necessary that polyethylene glycol and glycerin can be added. The electrolyte used for the dry solid polymer membrane 5 is an alkali metal halide (for example, sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide, potassium iodide) and a buffer solution (for example, phosphoric acid). It may be a phosphate such as sodium, potassium phosphate, sodium hydrogen phosphate, potassium hydrogen phosphate, or a hydroxide such as sodium hydroxide or potassium hydroxide). The gas permeable membrane 6 may be, for example, polyvinyl chloride, plasticized polyvinyl chloride, Teflon, polyethylene, or polypropylene. Since the oxygen sensor of this embodiment uses a solid polymer in which an electrolyte is dispersed, it is easier to manufacture than a sensor using a conventional electrolytic solution or electrolytic gel. Further, it is possible to apply a thin film forming technique such as plasma polymerization or sputtering to the formation of the gas permeable film 6, and the compatibility with the semiconductor manufacturing technique is good.

FIG. 2 shows a third embodiment of the present invention.
It is a block diagram of an electrode type solid oxygen sensor. In FIG. 2, (a) is a perspective view and (b) is a cross-sectional view taken along line mm ′ of (a). In this embodiment, three electrodes are used. That is, one platinum electrode 8 was used as a working electrode, the other platinum electrode 9 was used as a counter electrode, and the silver / silver chloride electrode 10 was used as the remaining electrode as a reference electrode. An electric current was passed between the working electrode 8 and the counter electrode 9, and the reference electrode (silver / silver chloride electrode) 10 was used to keep the potential of the hydrophilic polymer constant. This three-electrode type oxygen sensor does not consume the electrode material and can be an oxygen sensor having excellent stability. The material of each part, the manufacturing method, and the like are the same as described above.

FIG. 3 is a configuration diagram of a flow cell type solid oxygen sensor according to a third embodiment of the present invention. In FIG. 3, (a) is a perspective view of a flow cell type solid oxygen sensor. In this embodiment, through holes (flow paths) 12 are formed in a pair of surfaces of a rectangular parallelepiped polyvinyl chloride sensor body 11 to form a flow path through which a standard solution or a sample solution flows. Further, when a plurality of the present sensor bodies are stacked and used, a cylindrical convex portion 13 is provided on one of the surfaces where the through holes are formed in order to facilitate the alignment of the flow paths. An O-ring 14 was installed on the upper surface of the protrusion 13 to prevent liquid leakage. A terminal 15 for connecting the cathode and anode of the oxygen sensor to an external measurement circuit was provided on a part of the side surface of the flow cell. Further, (b) is a cross-sectional view taken along the line nn ′ of (a). In this embodiment, a cavity 16 is provided in a part of the inside of the sensor body 11, an inner curved surface 17 of the cavity 16 intersects with the flow channel 12, and a small hole 18 is formed on the side surface of the flow channel. ing. The gas permeable membrane 6 is formed along the curved surface 17 so as to be convex toward the flow path so as to completely close the small hole 18. A hydrophilic polymer film 5 and a substrate 19 having electrodes formed thereon were laminated on the side of the gas permeable film 6 opposite to the flow path. Further, when a plurality of the present sensor bodies are stacked and used, in order to facilitate the alignment of the flow path, the concave portion 2 that fits the cylindrical convex portion 13 is formed.
0 was provided on the surface opposite to the surface on which the convex portion was formed. Also,
(C) is an enlarged view of the electrode substrate 19. In this embodiment,
Insulating substrate 21 made of epoxy resin, polyimide, etc. (b)
The cathode platinum wire 22 and the anode silver wire 23 were embedded by bending so as to fit the curved surface 17. On the concave side of the insulating substrate 21,
A signal line 24 was connected to the platinum cathode and the silver anode. Also,
(D) is a plan view seen from the concave surface side of the electrode substrate 19 of (c). In this embodiment, the platinum wire 2 is placed at the center of the insulating substrate 21.
2, the silver wire 23 is arranged and embedded so as to surround it. Since the plurality of silver wires 23 are used at the same potential, they are connected by the metal wires 25 on the concave surface side of the electrode substrate 19. With such a configuration, the sample solution or the standard solution can be successively introduced into the flow channel 12 to continuously measure the gas partial pressure.

FIG. 4 is a schematic diagram of an oxygen partial pressure analysis system according to a fourth embodiment of the present invention. In this embodiment, the standard solution 26 and the standard solution 27 are introduced into the solid oxygen sensor 31 of the present invention by the ironing pump 30 via the on / off valve 28 and the switching valve 29, and are discarded in the waste solution bottle 32. A sample such as blood is introduced into the flow path by the sample introduction unit 33. After the sample measurement, the cleaning liquid 34 is introduced into the channel to wash the channel to prepare for the next measurement. The current value of the solid oxygen sensor 31 is measured by the potentiostat 35, and the data processing unit 3
In step 6, calculation such as concentration conversion is performed, sample information, measurement results, etc. are displayed on the display unit 37 and recorded in the recording unit 38. Further, it is stored in the storage unit 39 as needed. The oxygen partial pressure in the sample can be continuously and rapidly measured by the device of this configuration.

The effects of the above embodiment will be specifically described below.
FIG. 5 is a diagram showing a calibration curve of the solid oxygen sensor when the third and fourth embodiments of the present invention are used. In this embodiment, the flow cell type solid oxygen sensor shown in the third embodiment (FIG. 3) is applied to the oxygen partial pressure analysis system shown in the fourth embodiment (FIG. 4) to calibrate the solid oxygen sensor. The line was measured. In the solid oxygen sensor, polyvinyl alcohol was used as the hydrophilic polymer, potassium chloride was used as the electrolyte, and polyethylene glycol having a molecular weight of 600 was used as the moisturizing additive. A voltage of 0.7 V was applied between the cathode and the anode. As a result of the measurement, a calibration curve with good linearity was obtained in the oxygen partial pressure range of 0 mmHg to 600 mmHg.

FIG. 6 is a diagram showing the shelf life of the solid oxygen ion sensor of the present invention. Twenty-four solid oxygen sensors of the above-described example were manufactured and stored at room temperature, and the calibration curve of one sensor was measured every month to examine the shelf life. In addition,
In FIG. 6, the current value of the oxygen sensor with respect to the oxygen partial pressure of 100 mmHg is shown as sensitivity on the vertical axis. From this, it can be seen that even after 24 months from the time of manufacture, the same sensitivity as the initial sensitivity can be obtained and the product can be stored for a long period of time.

[0012]

According to the present invention, an oxygen sensor can be manufactured by using a solid polymer membrane without using an electrolytic solution or an electrolyte gel. Therefore, the structure of the oxygen sensor can be simplified.
A sensor having an arbitrary shape can be easily manufactured. Therefore, it is effective in reducing the cost of the sensor and can be disposable, so maintenance work such as replacement of the gas permeable membrane and replenishment of the electrolytic solution is unnecessary, and usability can be greatly improved. Further, in the present invention, since the hydrophilic polymer is in a dry state before the sensor is used, the water content in the electrolytic solution does not evaporate during storage unlike the prior art, and the storage life can be dramatically improved. it can.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a two-electrode type solid oxygen sensor according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a three-electrode type solid oxygen sensor according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a flow cell type solid oxygen sensor according to a third embodiment of the present invention.

FIG. 4 is a schematic diagram of an oxygen gas partial pressure analysis system according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a calibration curve of a solid oxygen sensor when the third and fourth embodiments of the present invention are used.

FIG. 6 is a diagram showing the shelf life of the solid oxygen ion sensor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Silicon dioxide 3 Cathode 4 Anode 5 Hydrophilic polymer 6 Gas permeable film 7 Epoxy resin 8 Working electrode 9 Counter electrode 10 Silver / silver chloride electrode 11 Sensor body 12 Through hole 13 Convex part 14 O-ring 15 Terminal 16 Cavity 17 Curved surface 18 Small hole 19 Electrode substrate 20 Recess 21 Insulating substrate 22 Platinum wire 23 Silver wire 24 Signal line 25 Metal wire 26 Standard solution 27 Standard solution 28 On / off valve 29 Switching valve 30 Pump 31 Solid oxygen sensor 32 Waste solution 33 Sample introduction Part 34 Cleaning Solution 35 Potentiostat 36 Data Processing Part 37 Display Part 38 Storage Part 39 Recording Part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshio Watanabe 1-280, Higashi-Kengokubo, Kokubunji, Tokyo

Claims (10)

[Claims] 1. An electric current measuring oxygen sensor utilizing an oxygen reduction reaction, characterized in that a space between a plurality of metal electrodes and a gas permeable membrane is filled with a dry residue of a hydrophilic polymer in which an electrolyte is dispersed. Solid oxygen sensor. 2. A current-measuring oxygen sensor in which a plurality of metal electrodes and oxygen acceptors are coated with a gas permeable film, wherein the oxygen acceptor is a hydrophilic polymer in which an electrolyte is dispersed. Oxygen sensor. 3. The solid oxygen sensor according to claim 1, wherein the plurality of metal electrodes, the dry residue of the hydrophilic polymer, and the gas permeable film are laminated in this order on a flat plate from the bottom. 4. The gas permeable film is formed on a side surface of a channel having a circular cross section with a curvature so that the gas permeable film is convex toward an inner surface of the channel. Two
The solid oxygen sensor described. 5. The metal electrode is selected from two or three of platinum, gold, silver, and lead, and is formed in a rod shape or a film shape. The solid oxygen sensor described. 6. The hydrophilic polymer is selected from the group consisting of polyvinyl alcohol, agarose, polyacrylamide, hydroxyethyl polymethacrylate, and polyethylene oxide, and ethylene glycol, polyethylene glycol, or glycerin can be added. The solid oxygen sensor according to claim 1 or 2, characterized in that. 7. The solid oxygen sensor according to claim 1, wherein the electrolyte is a halide of an alkali metal and a buffer solution. 8. The electrolyte is any of sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide and potassium iodide, and sodium phosphate, potassium phosphate, sodium hydrogen phosphate, potassium hydrogen phosphate,
3. The solid oxygen sensor according to claim 1, which is either sodium hydroxide or potassium hydroxide. 9. The gas permeable membrane is polyvinyl chloride,
The solid oxygen sensor according to claim 1, which is made of any one of plasticized polyvinyl chloride, Teflon, polyethylene, and polypropylene. 10. A flow path for flowing a biological sample containing a standard solution, a washing solution, blood, and urine, and the flow path is provided in the flow path.
The solid oxygen sensor described, a means for introducing a biological sample into the flow path, an ammeter for measuring the current flowing between the metal electrodes of the solid oxygen sensor, and data for calculating and displaying the partial pressure of oxygen contained in the sample An oxygen partial pressure measuring device comprising a processing means.