US20090294284A1

US20090294284A1 - Reference electrode

Info

Publication number: US20090294284A1
Application number: US12/128,063
Authority: US
Inventors: Shen-Kan Hsiung; Jung-Chuan Chou; Tai-Ping Sun; Nien-Hsuan Chou; Tza-Wei Huang
Original assignee: Chung Yuan Christian University
Current assignee: Chung Yuan Christian University
Priority date: 2008-05-28
Filing date: 2008-05-28
Publication date: 2009-12-03

Abstract

A reference electrode is disclosed. The reference electrode is developed by spreading an aqueous KCl gelling agar solid gel/poly(vinyl chloride)carboxylated (PVC—COOH) double layer on a screen-printing Ag/AgCl electrode body. Such polymer double layer can maintain ion concentration and keep stable chemical capacitance potential during measurement. The reference electrode of the present invention provides fast response time and high stability for major ions detection measurements in a wide range.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to reference electrodes.
2. Description of the Prior Art
Propelled by the advances in technology and human need, electrical and chemical measuring elements are becoming smaller. As such, manufacturing methods and tools are being developed and improved on to meet the needs for ever smaller elements.
Currently, reference electrodes are primarily made of glass or ceramic enclosing an electrolyte solution. However, due to the bulk size of the material such as glass or ceramic, the resulting reference electrodes cannot be reduced beyond a certain limit. Moreover, problems such as challenging manufacturing processes, fragile structure and high cost still exist.

SUMMARY OF THE INVENTION

In view of the prior art and the needs of the related industries, the present invention provides a reference electrode that solves the abovementioned shortcomings of the conventional.
One objective of the present invention is to provide a reference electrode, which is a layered structure that may include an insulating substrate, a conductive layer, an electrode layer, a solid electrolytic layer, a polymer protective film, an anti-oxidation layer and an insulating layer. More particularly, the solid electrolytic layer is solidified on the electrode layer by mixing an agar gel and an electrolyte solution under a high temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the disclosure. In the drawings:

FIG. 1 is a flowchart illustrating a method for manufacturing a reference electrode according to one embodiment of the present invention; and

FIGS. 2A and 2B are schematic diagrams depicting the structure of a reference electrode according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to a reference electrode. Detailed steps and constituents are given below to assist in the understanding the present invention. Obviously, the implementations of the present invention are not limited to the specific details known by those skilled in the art of reference electrode. On the other hand, well-known steps or constituents are not described in details in order not to unnecessarily limit the present invention. Detailed embodiments of the present invention will be provided as follow. However, apart from these detailed descriptions, the present invention may be generally applied to other embodiments, and the scope of the present invention is thus limited only by the appended claims.
The present invention proposes a reference electrode, which includes an insulating substrate, a conductive layer on the insulating substrate, an electrode layer on the conductive layer, a solid electrolytic layer on the electrode layer, a PVC—COOH protective film on the solid electrolytic layer, an anti-oxidation layer around the periphery of the conductive layer, an insulating layer around the periphery of the anti-oxidation layer. The solid electrolytic layer is formed by solidifying an electrolyte solution on the electrode layer using an agar gel.
Referring to FIG. 1, a schematic diagram depicting a method of constructing a reference electrode according to the above embodiment is shown. First, in step 110, a conductive layer is formed on a substrate. In step 120, an electrode layer is then formed on the above conductive layer. In step 130, a solid electrolytic layer is formed on the electrode layer. Then, in step 140, an anti-oxidation layer is formed on the portion of the conductive layer not covered by the electrode layer. In step 150, an insulating layer is formed at the periphery of the anti-oxidation layer. Finally, in step 160, a polymer protective film is formed on the solid electrolytic layer.
In addition, the step of forming a solid electrolytic layer further includes the following steps. In step 132, an agar gel powder is mixed with an electrolyte solution to form a mixture. Then, in step 134, the mixture is stirred under high temperature. Finally, in step 136, the mixture is cooled and thus solidified on the electrode layer at a low temperature. The above high temperature may be in a range between about 100° C. and about 150° C., while the low temperature may be in a range between about 0° C. and about 40° C.
Next, referring to FIGS. 2A and 2B, schematic diagrams depicting the reference electrode constructed according to the above embodiment are shown. The reference electrode includes an insulating substrate 210, a conductive layer 220, an electrode layer 230, a solid electrolytic layer 240, a polymer protective film 250, an anti-oxidation layer 260 and an insulating layer 270, wherein the solid electrolytic layer 240 is solidified on the electrode layer 230 by mixing an agar gel and an electrolyte solution under a high temperature. FIG. 2A is a cross-sectional view of the reference electrode, while FIG. 2B is a front cross-sectional view of the same reference electrode along X axis.
As shown in FIG. 2A, the electrode layer 230 is formed on a portion of the conductive layer 220. The anti-oxidation layer 260 is formed on the conductive layer 220 not covered by the electrode layer 230, so as to prevent oxidation of the electrode layer. The electrode layer 230 having an area of 8 mm×3 mm is preferred. Further, the conductive layer 220 may be connected with a line conductor for passing signals measured by the reference electrode. In addition, the insulating layer 270 may be formed on the conductive layer 220 to cover the sides of the electrode layer 230 and the solid electrolytic layer 240.
The polymer protective film 250 may be one selected from PVC—COOH, polycarbonate, polyester, polyether, polyamide, polyurethane, polyimide, poly (vinyl chloride) (PVC), polyethylene or a combination thereof. Since PVC—COOH has a stronger polarity than traditional PVC materials, thus when the reference electrode is immersed into a test solution, a PVC—COOH protective film can attract more electrolytes in the test solution. In addition, due to high permeability of the PVC—COOH protective film, reaction time between the electrolytes and the solid electrolytic layer can be greatly reduced, thereby enhancing response time of the reference electrode. Furthermore, the PVC—COOH protective film is better at keeping moisture than traditional PVC materials, such that it gives the solid electrolytic layer a better protection and a more stable ion concentration at the surface of the electrode layer, thereby achieving a more ideal reference electrode. Compared to a traditional reference electrode that employs electrolyte solution, the reference electrode proposed by present invention not only provides a fast response time and stable output voltage, but can be easily manufactured and miniaturized at a cheaper cost.
The substrate can be an insulating material selected from polycarbonate, polyester, polyether, polyamide, polyurethane, polyimide, poly (vinyl chloride) (PVC), glass, glass fiber, ceramic, PET or a combination thereof. In addition, the electrolyte solution can be a saturated potassium chloride solution, wherein the weight ratio of the agar gel powder and the saturated potassium chloride solution is 4%:96%.
In a preferred embodiment of the present invention, the electrode layer includes silver (Ag) and silver chloride (AgCl) with a mix ratio of 1:2. Ag/AgCl is baked on the conductive layer at a temperature range of about 40° C. to 120° C. The conductive layer can be a silver paste or ITO (Indium Tin Oxide) film to enhance conduction. The anti-oxidation layer enclosing the periphery of the silver paste can be a conductive carbon paste, which enhances electrical conduction while preventing the silver paste from oxidation due to exposure. The conductive layer, the electrode layer, the anti-oxidation layer and the insulating layer can for example be formed by screen printing technique. In addition, the insulating layer could comprise UV curing gel to avoid that the test solution and the solid electrolytic layer contact to each other directly, and could fix the solid electrolytic layer more strongly for providing against the damage from external force.
The foregoing description is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obvious modifications or variations are possible in light of the above teachings. In this regard, the embodiment or embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the inventions as determined by the appended claims when interpreted in accordance with the breath to which they are fairly and legally entitled.
It is understood that several modifications, changes, and substitutions are intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.

Claims

1. A reference electrode, comprising:

a insulating substrate;

a conductive layer, placed on said insulating substrate;

an electrode layer, placed on said conductive layer;

a solid electrolytic layer, solidified from an electrolyte by an agar gel and formed onto said electrode layer;

a polymer protective film, placed on said solid electrolytic layer, wherein said polymer protective film comprises at least one or any combination of the following: PVC—COOH, PC (Polycarbonate), Polyester, Polyether, Poly Amide, Polyurethane resin adhesive, Polyimide, PVC (Polyvinyl chloride polymer), PET (Polyrthylene Terephthalate);

an anti-oxidation layer, placed on said conductive layer; and

a insulating layer, placed on said anti-oxidation layer.

2. A reference electrode of claim 1, wherein the ratio of Ag to AgCl in said electrode layer is 1:2.

3. A reference electrode of claim 1, wherein said electrolyte could be a saturated solution of KCl.

4. A reference electrode of claim 1, wherein a mixture of said agar gel and said electrolyte at high temperature is cooled to form said solid electrolytic layer on said electrode layer.

5. A reference electrode of claim 1, wherein said conductive layer and said electrode layer are formed by screen printing method.

6. A reference electrode of claim 1, wherein, by screen printing method, said anti-oxidation layer is formed on the region of said conductive layer which is not covered by said electrode layer.

7. A reference electrode of claim 1, wherein, by screen printing method, said insulating layer is formed on said anti-oxidation layer and said conductive layer to wrap flanks of said electrode layer and said solid electrolytic layer.

8. A reference electrode of claim 1, wherein said insulating layer comprises UV curing gel.

9. A reference electrode of claim 1, wherein said conductive layer comprises Ag paste or ITO (Indium Tin Oxide) conductive film.

10. A reference electrode, comprising:

a insulating substrate;

a conductive layer, formed on said insulating substrate;

an electrode layer, formed on said conductive layer;

a solid electrolytic layer, formed on said electrode layer, wherein a mixture of an agar gel and an electrolyte at high temperature is cooled to form said solid electrolytic layer on said electrode layer;

a polymer protective film, smeared over said solid electrolytic layer for protecting said solid electrolytic layer;

an anti-oxidation layer, formed on said conductive layer for preventing the oxidation at said conductive layer; and

a insulating layer, formed on said anti-oxidation layer.

11. A reference electrode of claim 10, wherein the ratio of Ag to AgCl in said electrode layer is 1:2.

12. A reference electrode of claim 10, wherein said polymer protective film comprises at least one or any combination of the following: PVC—COOH, PC (Polycarbonate), Polyester, Polyether, Poly Amide, Polyurethane resin adhesive, Polyimide, PVC (Polyvinyl chloride polymer), PET (Polyrthylene Terephthalate).

13. A reference electrode of claim 10, wherein said insulating layer comprises UV curing gel, and said conductive layer comprises Ag paste or ITO (Indium Tin Oxide) conductive film.

14. A reference electrode of claim 10, wherein said conductive layer, said electrode layer, said anti-oxidation layer, and insulating layer are formed by screen printing method.

15. A reference electrode fabrication method, comprising the following steps of:

providing a substrate;

forming a conductive layer on said substrate;

forming an electrode layer on said conductive layer;

forming a solid electrolytic layer on said electrode layer, wherein the forming method of said solid electrolytic layer comprises the following steps of:

forming a mixture by mixing an agar gel powder and an electrolyte;

stirring and mixing said mixture at high temperature; and

cooling said mixture at low temperature to solidify said mixture onto said electrode layer;

forming an anti-oxidation layer on said conductive layer for preventing the oxidation at said conductive layer;

forming a insulating layer on said anti-oxidation layer;

forming a polymer protective film on said solid electrolytic layer for protecting said solid electrolytic layer.

16. A reference electrode fabrication method of claim 15, wherein said high temperature is in a range between about 100° C. and about 150° C., and said low temperature is in a range between about 0° C. and about 40° C.

17. A reference electrode fabrication method of claim 15, wherein the ratio of Ag and AgCl in said electrode layer is 1:2.

18. A reference electrode fabrication method of claim 17, wherein Ag and AgCl in said electrode layer are baked at a temperature range of about 40° C. to 120° C.

19. A reference electrode fabrication method of claim 15, wherein said electrolyte could be a saturated solution of KCl, and the weight ratio of said agar gel powder and said saturated potassium chloride solution is 4%:96%.

20. A reference electrode fabrication method of claim 15, wherein said conductive layer, said electrode layer, said anti-oxidation layer, and insulating layer are formed by screen printing method.