CN110018215B - Fick diffusion law-based miniature chloride ion sensor and method thereof - Google Patents

Abstract

The invention discloses a micro chloride ion sensor based on Fick's diffusion law and a method thereof. The chloride ion sensor prepared by the method of the invention is a thin-sheet, all-solid-state micro chloride ion sensor, which has small size and good structural stability. It has the advantages of high reliability and good sealing. It can be placed in any testing part of the instrument and equipment, and is less affected by external factors. It is especially suitable for real-time monitoring of aircraft corrosion conditions in high-salt and high-humidity micro-liquid film environments. This invention can make up for the shortcomings of previous passive measurement methods such as weak signal, poor stability, short life, and long response time. It can also measure the chloride ion concentration in the micro-liquid film state, and can be applied to aircraft salt spray corrosion and protection, and improve the service life of aircraft. .

Description

Micro chloride ion sensor and method based on Fick's diffusion law

Technical field

The invention relates to the field of chloride ion sensors, and in particular to a miniature chloride ion sensor based on Fick's diffusion law and a method thereof.

Background technique

Corrosion is one of the main forms of aircraft structural damage, accounting for 20% of all structural damage. Aircraft structural corrosion is the cumulative chemical loss and damage of components through chemical or electrochemical effects in an atmospheric corrosive micro-liquid film environment. In the early stages of corrosion, it is difficult to detect the corrosion site. If it is not controlled after its initiation, it will develop faster and more seriously than other damages. Corrosion damage to aircraft directly affects the aircraft's availability, and more seriously affects the pilot's life safety. Therefore, active protective measures must be taken to predict the degree of aircraft corrosion in advance to reduce aircraft maintenance costs and avoid tragedies.

Whether it is a civilian or military aircraft in the eastern coastal areas of my country, due to long-term flight missions in harsh and complex environments such as high salt spray and high humidity, the surface of the aircraft and even the interior of the cockpit are subject to various corrosions all the time. These corrosions are generally invisible to the naked eye in the early stages of occurrence. By the time they are discovered, the surface of the aircraft has already suffered severe corrosion, which will greatly reduce the service life of the aircraft and seriously threaten the safety of pilots.

At present, my country's corrosion protection for aircraft is mainly based on water sealing and regular inspection of the aircraft body. Traditional detection methods are inefficient and costly. Although there are also reports of using ultrasound, infrared imaging and other technologies to evaluate the corrosion status of aircraft, etc. However, these methods only detect the corroded parts when the aircraft has been severely corroded, which is inefficient and costly. At present, domestic corrosion inspections of aircraft are mainly based on pH. Since the corrosion rate of chlorine ions on aircraft is lower than the corrosion rate of hydrogen ions on aircraft, research on chloride ion corrosion protection has not been started at home and abroad. However, in coastal environments, In a high-salt, high-humidity, weakly acidic environment such as an island environment, the corrosion rate of chloride ions on aircraft almost doubles. There is an urgent need for a sensor to monitor chloride ion concentration in aircraft.

Contents of the invention

The technical problem to be solved by the present invention is to provide a miniature chloride ion sensor and method based on Fick's diffusion law in view of the defects involved in the background technology.

The present invention adopts the following technical solutions to solve the above technical problems:

A miniature chloride ion sensor based on Fick's diffusion law, including a polyimide sheet substrate, auxiliary electrode, sensing electrode, reference electrode and counter electrode;

The auxiliary electrode, sensing electrode, reference electrode, and counter electrode are all arranged on the polyimide sheet substrate, and each includes a sensitive element, a wire, and a solder joint connected to the sensitive element through the wire;

The sensing element of the sensing electrode is interdigitated; the sensing element of the auxiliary electrode is rectangular, with a groove for placing the sensing element of the sensing electrode; the sensing element of the sensing electrode is placed on the sensitive element of the auxiliary electrode inside the groove;

The sensitive elements of the reference electrode and the counter electrode are all in the shape of long strips, which are respectively arranged on both sides of the auxiliary electrode sensitive element and parallel to the sides of the auxiliary electrode sensitive element, and are the same as the interdigital length of the sensing element of the stand-alone machine. Orientation vertical;

The sensitive elements of the auxiliary electrode, the sensitive element of the sensing electrode, and the sensitive elements of the reference electrode all include Ti adhesion layer, Pt electrode layer and Au film layer from bottom to top; the sensitive elements of the counter electrode all include from bottom to top. Ti adhesion layer and Pt electrode layer;

The sensitive element of the auxiliary electrode, the sensitive element of the sensing electrode, and the sensitive element of the reference electrode are plated with an Ag thin film layer, and the Ag thin film layer is plated with an AgCl thin film layer;

There is no contact between the auxiliary electrode, the sensing electrode, the reference electrode and the counter electrode.

As a further optimization solution of the present invention's miniature chloride ion sensor based on Fick's diffusion law, the interdigital index of the sensing element of the sensing electrode is 3, the interdigital width is 5μm, the interdigital spacing is 1mm, and the interdigital length is 3mm; The wire width of the sensing electrode is 70 μm, and the solder joint of the sensing electrode is a rectangle of 1*1.5mm;

The sensitive element of the auxiliary electrode is a rectangle of 8*4mm; the distance between the sensitive element of the auxiliary electrode and the sensitive element of the sensing electrode is 5μm; the wire width of the auxiliary electrode is 70μm, and the soldering point of the auxiliary electrode is 1*1.5 mm rectangle;

The sensitive element of the reference electrode is a rectangle of 70*3000 μm; the distance between the sensitive element of the reference electrode and the sensitive element of the auxiliary electrode is 70 μm; the line width of the reference electrode wire is 70 μm, and the soldering point of the reference electrode It is a rectangle of 1*1.5mm;

The sensitive element of the counter electrode is a rectangle of 70*3000 μm; the distance between the sensitive element of the counter electrode and the sensitive element of the auxiliary electrode is 70 μm; the line width of the counter electrode wire is 70 μm, and the soldering point of the counter electrode is 1 *1.5mm rectangle.

As a further optimization solution of the present invention's miniature chloride ion sensor based on Fick's diffusion law, it also includes first to fourth connectors;

One end of the first to fourth connectors is connected to the solder joints of the auxiliary electrode, the sensing electrode, the reference electrode, and the Pt counter electrode respectively, and the other ends are used to connect to the outside world;

Insulating layers are provided on the wires and solder joints of the auxiliary electrode, sensing electrode, reference electrode, and Pt counter electrode.

The present invention also discloses a measurement method using the miniature chloride ion sensor based on Fick's diffusion law, which includes the following steps:

Step 1), set up a current source, a function generator and a potential measuring device. The control terminal of the current source is connected to the function generator, and a constant pulse constant current is generated through the function generator. The positive electrode of the current source is connected to the solder joint of the counter electrode, and the current The negative electrode of the source is connected to the solder joint of the auxiliary electrode; the positive electrode of the potential measuring device is connected to the solder joint of the receiving electrode, and the negative electrode of the potential measuring device is connected to the solder joint of the reference electrode;

Step 2), measure the potential curve of the sensing electrode in the miniature chloride ion sensor through a potential measuring device;

Step 3): Derive the potential curve to obtain the derivative curve of the potential curve, and let the time corresponding to the peak value of the derivative curve be the transition time τ;

Step 4), calculate the chloride ion concentration C ^* _O measured by the micro chloride ion sensor according to the following formula:

In the formula, _DO is the chloride ion diffusion coefficient, A is the surface area of the auxiliary electrode, F is the Faraday coefficient, and I is the current applied by the current source.

The invention also discloses a preparation method of the miniature chloride ion sensor based on Fick's diffusion law, which includes the following steps:

Step A), using the magnetron sputtering method to sequentially sputter the Ti adhesion layer and the Pt electrode layer on the polyimide sheet substrate;

Step B), use photolithography technology to transfer the circuit pattern on the polyimide sheet substrate after sputtering the Ti adhesion layer and the Pt electrode layer to form the reference electrode, the sensing electrode, the auxiliary electrode, and the counter electrode on the Ti Patterns on the adhesion layer and Pt electrode layer;

Step C), electroplating Au on the Pt electrode layer of the pattern of the reference electrode, sensing electrode, and auxiliary electrode using an electroplating method to form an Au thin film layer;

Step D), electroplating Ag on the Au thin film layers of the reference electrode, sensing electrode, and auxiliary electrode using an electroplating method to form an Ag thin film layer;

Step E), electroplating AgCl on the Ag thin film layers of the reference electrode, the sensing electrode, and the auxiliary electrode by electroplating to form an AgCl thin film layer.

Compared with the existing technology, the present invention adopts the above technical solution and has the following technical effects:

The invention has high stability, good sensitivity, and can perform real-time monitoring of chloride ions in a weakly acidic salt spray environment. It solves the problem that the current atmospheric monitoring is mainly based on traditional monitoring sites, with few sites, small coverage area, poor real-time data update, and inconsistency. It can truly reflect the real air quality information that people are exposed to around them.

Description of the drawings

Figure 1 is a schematic diagram of the overall structure of the micro chloride ion sensor provided by the present invention.

Figure 2 is a partial enlarged view of point A in Figure 1;

Figure 3 is a diagram of the sputtering and photolithography scheme of the micro chloride ion sensor provided by the present invention;

Figure 4 is a connection diagram of the chloride ion sensor test circuit provided by the present invention;

Figure 5 is a pulse current function diagram of the micro chloride ion sensor provided by the present invention;

Figure 6 is a Nernst theoretical potential curve diagram of the miniature chloride ion sensor provided by the present invention;

Figure 7 is a graph showing the relationship between potential value and time obtained after signal processing of the micro-chloride ion sensor according to the embodiment of the present invention under micro-liquid membrane conditions with chloride ion concentrations of 0.1, 0.3, 0.5, 0.7 and 1 mol/L respectively;

Figure 8 is a derivative diagram of the test results of the micro-chloride ion sensor according to the embodiment of the present invention under micro-liquid membrane conditions with chloride ion concentrations of 0.1, 0.3, 0.5, 0.7, and 1 mol/L;

Figure 9 is a comparison diagram of the transition time calibration curve and the theoretical equation obtained by conducting ten tests on the micro-liquid membrane conditions of chloride ion concentrations of 0.1, 0.3, 0.5, 0.7, and 1 mol/L according to the embodiment of the present invention.

In the figure, 1 - the sensitive element of the counter electrode, 2 - the wire of the counter electrode, 3 - the solder joint of the counter electrode, 4 - the sensitive element of the auxiliary electrode, 5 - the wire of the auxiliary electrode, 6 - the solder joint of the auxiliary electrode, 7 - The sensitive element of the sensing electrode, 8 - The wire of the sensing electrode, 9 - The solder joint of the sensing electrode, 10 - The sensitive element of the reference electrode, 11 - The wire of the reference electrode, 12 - The solder joint of the reference electrode, 13 - Polyimide sheet substrate.

Detailed ways

The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings:

The invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, components are exaggerated for clarity.

As shown in Figure 1, the present invention discloses a miniature chloride ion sensor based on Fick's diffusion law, which includes a polyimide sheet substrate, an auxiliary electrode, a sensing electrode, a reference electrode and a counter electrode;

The auxiliary electrode, sensing electrode, reference electrode, and counter electrode are all arranged on the polyimide sheet substrate, and each includes a sensitive element, a wire, and a solder joint connected to the sensitive element through the wire;

As shown in Figure 2, the sensing element of the sensing electrode is interdigitated; the sensing element of the auxiliary electrode is rectangular, with a groove for placing the sensing electrode sensing element; the sensing element of the sensing electrode is placed In the groove of the auxiliary electrode sensitive element;

The sensitive elements of the reference electrode and the counter electrode are all in the shape of long strips, which are respectively arranged on both sides of the auxiliary electrode sensitive element and parallel to the sides of the auxiliary electrode sensitive element, and are the same as the interdigital length of the sensing element of the stand-alone machine. Orientation vertical;

The sensitive elements of the auxiliary electrode, the sensitive element of the sensing electrode, and the sensitive elements of the reference electrode all include Ti adhesion layer, Pt electrode layer and Au film layer from bottom to top; the sensitive elements of the counter electrode all include from bottom to top. Ti adhesion layer and Pt electrode layer;

The sensitive element of the auxiliary electrode, the sensitive element of the sensing electrode, and the sensitive element of the reference electrode are plated with an Ag thin film layer, and the Ag thin film layer is plated with an AgCl thin film layer;

There is no contact between the auxiliary electrode, the sensing electrode, the reference electrode and the counter electrode.

As a further optimization solution of the present invention's miniature chloride ion sensor based on Fick's diffusion law, the interdigital index of the sensing element of the sensing electrode is 3, the interdigital width is 5μm, the interdigital spacing is 1mm, and the interdigital length is 3mm; The wire width of the sensing electrode is 70 μm, and the solder joint of the sensing electrode is a rectangle of 1*1.5mm;

The sensitive element of the auxiliary electrode is a rectangle of 8*4mm; the distance between the sensitive element of the auxiliary electrode and the sensitive element of the sensing electrode is 5μm; the wire width of the auxiliary electrode is 70μm, and the soldering point of the auxiliary electrode is 1*1.5 mm rectangle;

The sensitive element of the reference electrode is a rectangle of 70*3000 μm; the distance between the sensitive element of the reference electrode and the sensitive element of the auxiliary electrode is 70 μm; the line width of the reference electrode wire is 70 μm, and the soldering point of the reference electrode It is a rectangle of 1*1.5mm;

The sensitive element of the counter electrode is a rectangle of 70*3000 μm; the distance between the sensitive element of the counter electrode and the sensitive element of the auxiliary electrode is 70 μm; the line width of the counter electrode wire is 70 μm, and the soldering point of the counter electrode is 1 *1.5mm rectangle.

As a further optimization solution of the present invention's miniature chloride ion sensor based on Fick's diffusion law, it also includes first to fourth connectors;

One end of the first to fourth connectors is connected to the solder joints of the auxiliary electrode, the sensing electrode, the reference electrode, and the Pt counter electrode respectively, and the other ends are used to connect to the outside world;

Insulating layers are provided on the wires and solder joints of the auxiliary electrode, sensing electrode, reference electrode, and Pt counter electrode.

The invention also discloses a preparation method of the miniature chloride ion sensor based on Fick's diffusion law, which includes the following steps:

Step A), using the magnetron sputtering method to sequentially sputter the Ti adhesion layer and the Pt electrode layer on the polyimide sheet substrate;

Step B), use photolithography technology to transfer the circuit pattern on the polyimide sheet substrate after sputtering the Ti adhesion layer and the Pt electrode layer to form the reference electrode, the sensing electrode, the auxiliary electrode, and the counter electrode on the Ti Patterns on the adhesion layer and Pt electrode layer;

Step C), electroplating Au on the Pt electrode layer of the pattern of the reference electrode, sensing electrode, and auxiliary electrode using an electroplating method to form an Au thin film layer;

Step D), electroplating Ag on the Au thin film layers of the reference electrode, sensing electrode, and auxiliary electrode using an electroplating method to form an Ag thin film layer;

Step E), electroplating AgCl on the Ag thin film layers of the reference electrode, the sensing electrode, and the auxiliary electrode by electroplating to form an AgCl thin film layer.

The polyimide sheet substrate is a 15*10*1mm rectangular parallelepiped substrate. The material used for the polyimide sheet substrate is polyimide (PI). Polyimide (PI) has high temperature resistance (up to 400°C), excellent mechanical properties, high radiation resistance, and good Excellent acid and alkali chemical stability and flexibility. Using polyimide as the substrate material of the chloride ion sensor can increase the temperature range of the sensor, reduce the impact of the external corrosive environment on the chloride ion sensor, and improve the stability and reliability of the sensor in complex environments. In addition, polyimide is a flexible material that can broaden the application field and scope of chloride ion sensors.

Figure 3 is a diagram of the sputtering and photolithography scheme of the micro chloride ion sensor provided by the present invention.

The present invention also discloses a measurement method using the miniature chloride ion sensor based on Fick's diffusion law, which includes the following steps:

Step 1), as shown in Figure 4, set up a current source, a function generator and a potential measuring device. The control terminal of the current source is connected to the function generator, and a constant pulse constant current is generated through the function generator. The positive electrode of the current source is connected to the The solder joint of the electrode, the negative electrode of the current source is connected to the solder joint of the auxiliary electrode; the positive electrode of the potential measuring device is connected to the solder joint of the receiving electrode, and the negative electrode of the potential measuring device is connected to the solder joint of the reference electrode;

Step 2), measure the potential curve of the sensing electrode in the miniature chloride ion sensor through a potential measuring device;

Step 3): Derive the potential curve to obtain the derivative curve of the potential curve, and let the time corresponding to the peak value of the derivative curve be the transition time τ;

Step 4), calculate the chloride ion concentration C ^* _O measured by the micro chloride ion sensor according to the following formula:

In the formula, _DO is the chloride ion diffusion coefficient, A is the surface area of the auxiliary electrode, F is the Faraday coefficient, and I is the current applied by the current source.

Figure 5 is a pulse current function diagram of the micro chloride ion sensor provided by the present invention; see Figure 5, the pulse current is a DC signal, and the change pattern with time is the same; when the pulse current is positive, the sensor starts to measure a potential that changes with time S-shaped curve, the software calculates a corresponding transition time through the test interface. When the pulse current is negative, the sensor is in a stagnant state, and the potential gradually returns to zero value;

Figure 6 is a theoretical potential curve diagram of the micro chloride ion sensor Nernst provided by the present invention; referring to Figure 6, τ is the transition time of the chloride ion concentration. In theory, when t=τ, the potential is infinite, and the figure shows the potential threshold of the measuring equipment;

Figure 7 is a graph showing the relationship between potential value and time obtained after signal processing of the micro-chloride ion sensor according to the embodiment of the present invention under micro-liquid membrane conditions with chloride ion concentrations of 0.1, 0.3, 0.5, 0.7 and 1 mol/L respectively; see Figure 7. The potential time curve measured by the sensor in a micro-liquid film environment is an S-shaped curve, and as the concentration increases, the S-shaped curve gradually moves backward, and the higher the concentration, the smoother the curve, and the inflection point (transition) of the curve time) the clearer;

Figure 8 is a derivative diagram of the test results of the micro chloride ion sensor according to the embodiment of the present invention under the conditions of micro-liquid membrane with chloride ion concentrations of 0.1, 0.3, 0.5, 0.7 and 1 mol/L respectively. Referring to Figure 8, the sensor is measured at 0.1, 0.3, 0.3, 0.7 and 1 mol/L respectively. The peak value of the derivative curve of the test results under micro-liquid membrane conditions with chloride ion concentrations of 0.5, 0.7, and 1 mol/L is very obvious. The peak value of the derivative curve can be obtained through the automatic peak-finding function, and the peak value is the transition time value;

Figure 9 is a comparison diagram between the transition time calibration curve and the theoretical equation obtained by conducting ten tests on the micro-liquid membrane conditions of 0.1, 0.3, 0.5, 0.7, and 1 mol/L chloride ion concentration of the micro-chloride ion sensor according to the embodiment of the present invention; see Figure 9 , the transition time calibration curve obtained by multiple measurements of the sensor is consistent with the theoretical equation and has good stability.

It can be understood by one of ordinary skill in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It should also be understood that terms such as those defined in general dictionaries are to be understood to have meanings consistent with their meaning in the context of the prior art, and are not to be taken in an idealized or overly formal sense unless defined as herein. explain.

The above-mentioned specific embodiments further describe the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above-mentioned are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims (5)

1. A miniature chloride ion sensor based on Fick's diffusion law, which is characterized by including a polyimide sheet substrate, an auxiliary electrode, a sensing electrode, a reference electrode and a counter electrode; The auxiliary electrode, sensing electrode, reference electrode, and counter electrode are all arranged on the polyimide sheet substrate, and each includes a sensitive element, a wire, and a solder joint connected to the sensitive element through the wire; The sensing element of the sensing electrode is interdigitated; the sensing element of the auxiliary electrode is rectangular, with a groove for placing the sensing element of the sensing electrode; the sensing element of the sensing electrode is placed on the sensitive element of the auxiliary electrode inside the groove; The sensitive elements of the reference electrode and the counter electrode are all in the shape of long strips, which are respectively arranged on both sides of the auxiliary electrode sensitive element and parallel to the sides of the auxiliary electrode sensitive element, and are the same as the interdigital length of the sensing element of the stand-alone machine. Orientation vertical; The sensitive elements of the auxiliary electrode, the sensitive element of the sensing electrode, and the sensitive elements of the reference electrode all include Ti adhesion layer, Pt electrode layer and Au film layer from bottom to top; the sensitive elements of the counter electrode all include from bottom to top. Ti adhesion layer and Pt electrode layer; The sensitive element of the auxiliary electrode, the sensitive element of the sensing electrode, and the sensitive element of the reference electrode are plated with an Ag thin film layer, and the Ag thin film layer is plated with an AgCl thin film layer; There is no contact between the auxiliary electrode, the sensing electrode, the reference electrode and the counter electrode. 2. The micro chloride ion sensor based on Fick's diffusion law according to claim 1, characterized in that the interdigital index of the sensitive element of the sensing electrode is 3, the interdigital width is 5 μm, the interdigital spacing is 1mm, and the interdigital distance is 1mm. The length is 3mm; the wire width of the sensing electrode is 70 μm, and the solder joint of the sensing electrode is a rectangle of 1*1.5mm; The sensitive element of the auxiliary electrode is a rectangle of 8*4mm; the distance between the sensitive element of the auxiliary electrode and the sensitive element of the sensing electrode is 5μm; the wire width of the auxiliary electrode is 70μm, and the soldering point of the auxiliary electrode is 1*1.5mm rectangle; The sensitive element of the reference electrode is a rectangle of 70*3000 μm; the distance between the sensitive element of the reference electrode and the sensitive element of the auxiliary electrode is 70 μm; the line width of the reference electrode wire is 70 μm, and the soldering point of the reference electrode It is a rectangle of 1*1.5mm; The sensitive element of the counter electrode is a rectangle of 70*3000 μm; the distance between the sensitive element of the counter electrode and the sensitive element of the auxiliary electrode is 70 μm; the line width of the counter electrode wire is 70 μm, and the soldering point of the counter electrode is 1 *1.5mm rectangle. 3. The micro chloride ion sensor based on Fick's diffusion law according to claim 1, characterized in that it also includes first to fourth connectors; One end of the first to fourth connectors is connected to the solder joints of the auxiliary electrode, the sensing electrode, the reference electrode, and the Pt counter electrode respectively, and the other ends are used to connect to the outside world; Insulating layers are provided on the wires and solder joints of the auxiliary electrode, sensing electrode, reference electrode, and Pt counter electrode. 4. The measuring method of the micro-chloride ion sensor based on Fick's diffusion law according to claim 1, characterized in that it includes the following steps: Step 1), set up a current source, a function generator and a potential measuring device. The control terminal of the current source is connected to the function generator, and a constant pulse constant current is generated through the function generator. The positive electrode of the current source is connected to the solder joint of the counter electrode, and the current The negative electrode of the source is connected to the solder joint of the auxiliary electrode; the positive electrode of the potential measuring device is connected to the solder joint of the receiving electrode, and the negative electrode of the potential measuring device is connected to the solder joint of the reference electrode; Step 2), measure the potential curve of the sensing electrode in the miniature chloride ion sensor through a potential measuring device; Step 3): Derive the potential curve to obtain the derivative curve of the potential curve, and let the time corresponding to the peak value of the derivative curve be the transition time τ; Step 4), calculate the chloride ion concentration C ^* _O measured by the micro chloride ion sensor according to the following formula: In the formula, _DO is the chloride ion diffusion coefficient, A is the surface area of the auxiliary electrode, F is the Faraday coefficient, and I is the current applied by the current source. 5. The preparation method of a miniature chloride ion sensor based on Fick's diffusion law according to claim 1, characterized in that it comprises the following steps: Step A), using the magnetron sputtering method to sequentially sputter the Ti adhesion layer and the Pt electrode layer on the polyimide sheet substrate; Step B), use photolithography technology to transfer the circuit pattern on the polyimide sheet substrate after sputtering the Ti adhesion layer and Pt electrode layer to form the reference electrode, sensing electrode, auxiliary electrode, and counter electrode on the Ti Patterns on the adhesion layer and Pt electrode layer; Step C), electroplating Au on the Pt electrode layer of the pattern of the reference electrode, sensing electrode, and auxiliary electrode using an electroplating method to form an Au thin film layer; Step D), electroplating Ag on the Au thin film layers of the reference electrode, sensing electrode, and auxiliary electrode using an electroplating method to form an Ag thin film layer; Step E), electroplating AgCl on the Ag thin film layers of the reference electrode, the sensing electrode, and the auxiliary electrode by electroplating to form an AgCl thin film layer.