TWI227779B - Manufacturing method of a differential potentiometric electrochemical sensor using conductive thin film and conductive polymer - Google Patents

Abstract

In this invention, a differential potentiometric electrochemical sensor was presented which was fabricated by using the conductive thin film and conductive polymer as the sensing membrane. This differential potentiometric electrochemical sensor is different from the conventional potentiometric electrochemical pH sensor, which this sensor is a solid-state planar pH sensor. The SnO2 is used as the pH sensor and the reference electrode in this differential device. And the conductive polymer is used as the contrast pH sensor. The SnO2 thin film has excellent pH sensitivity, which is about 57 mV/pH, and the polypyrrole has linear pH sensitivity, which is about 27 mV/pH. Hence, these two pH sensors have different pH sensitivity and can be fabricated a differential pH sensor. The pH sensitivity of this differential sensor is about 30 mV/pH and linear. Controlling its polymerization conditions can control the pH sensitivity of the conductive polymer. Thus, the pH sensitivity is easily changed to apply into the fabrication of the pH sensor or the biosensor. According to above descriptions, this invention presents a sensing device has such advantages as solid-state, dry storage, simple fabrication process.

Description

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————— J 玖 'Description of the invention: [Technical field to which the invention belongs] The present invention relates to a method for making a differential pair acid-base sensing element using a conductive polymer, in particular, a method for making a The characteristics of the special ion sensor '4 electric polymer can be produced by controlling its polymer ring to produce different π sensing parts, so it can be achieved when applied to the production of differential pair ion sensing π parts. Controls the characteristics of differential pair ion sensing elements. [Prior art] There are many shortcomings in the practical application of the conventional organic quantitative analysis method. 13] For example, the operation is complicated, the analysis time is too long, the equipment is expensive, and it cannot be applied to the detection with Hi & Therefore, the search for a kind of research that can make up for the shortcomings of traditional quantitative analysis has been carried out. The biosensor is designed by combining the science of biochemistry, electrical circuits, materials science, and optics to meet the needs of various fields: Sensor. The prototype of the biosensor is based on the theory proposed by Clark et al. [4] in 1962, and uses the theory of the specificity of enzymes and their substrates to establish an organic detection method. Then in 1967, uPdike and Hicks immobilized the oxidase and made the & thin film [5], and then combined with the dissolved oxygen electrode to form a grape 7 detector, which has since triggered a research boom in biosensors, including: 氢 hydrogen peroxide electrode , Hydrogen electrode, hydrogen ion electrode, ion electrode, 'root electrode—carbon oxide electrode, and ion sensing field effect transistor. / Ion-sensing field-effect transistor is a semiconductor plutonium sensor. The metal on the gate of the original second-class metal-oxide half-field-effect transistor is removed and placed in an aqueous solution to expose the exposed metal after the gate metal is removed. The silicon dioxide layer is in contact with the aqueous solution, and is used to sense the interface potential of the aqueous solution to the surface of the silicon dioxide layer, so as to achieve the purpose of measuring the #M ion concentration. Relevant research on ion-sensing field effect transistors, such as: material improvement [6_8], reference electrode research and miniaturization [9-11], structure improvement, etc. [12_13] have been discussed successively. With the advent of ion-sensing field-effect transistor elements, other applications have also been widely developed, such as detecting acid values in blood, m chloride, fluoride ions, and ions of various types of ions, etc. [14_19] The main principle of ion-sensing field effect transistor is mainly used. Extended ion-sensing field-effect transistor is an element developed from self-sensing field-effect transistor. It was first proposed by Spiegel [20], which is different from ion-sensing field-effect transistor. The field effect transistor retains the original metal gate in the metal-oxide half field effect transistor, and the sensing film is plated on the other end of the metal closed electrode extension. Extended ion-sensing field-effect transistor has the following advantages over ion-sensing field-effect transistor, including: ⑴ the electrostatic protection provided by the wire to the component; ⑺ the transistor's transistor can avoid direct contact with the aqueous solution; ⑺ can reduce light on the component Effect [21]. The multi-test electrode is an electrochemical sensing element. Its characteristics should be different for different solutions to be tested. The characteristics of quasi-potentials are used to establish standard reference potentials. The working principle is to use reference electrodes in different solutions. Characteristics' to avoid the sensing characteristics of the sensing element due to different solutions to be tested

deviation. For general electrochemical sensing elements, the electrode or silver / gas-cut H❿ This 4-electrode is a Gancai electrode, so its reference electrode cannot be used for m test. Most of it is a wet reference, RH is miniaturized, and it requires long-term operation. Soaking in the buffer solution of the mesh is inconvenient in use and storage. Therefore, in recent years, for the purpose of miniaturizing the f-sensing element and drying storage, the reference electrode: design is an important research topic. Related papers explore this aspect. With reference to related research papers on acid-sensing ion-sensing field-effect transistors, the current research trend of the development of sensing elements in miniaturized reference electrode systems can be: the current production methods include: micro-electro-mechanical processing, silver / gasified silver thin film Deposition, differential pair circuit design, etc. [22-25]. The conventional technology has been patented as follows: (-) Byung Ki Sohn, USP 5,309,085; Date of Patent: May 3, 1994 "Measuring circuit with a bi〇sens〇r added-sensitive field effect transistors", This patent is proposed as a readout circuit of an ion sensing field effect transistor biosensor. This circuit has the advantages of simple structure and easy integration. The circuit consists of two ion sensing field effect transistors as input terminals. Two field-effect transistors, one is an enzyme field-effect transistor, and the other is a reference field-effect transistor. The enzyme field-effect transistor is composed of an enzyme fixed on an ion-sensing field-effect transistor sensing gate, and this circuit It has different amplification functions in order to amplify the output of the sensing element. The voltage phenomenon of the ion-sensing field-effect transistor is caused by the use of an unstable semi-reference electrode that is affected by temperature changes. Therefore, the gain of the readout circuit can be adjusted to adjust the operation of the device. 7 The characteristics of this ion-sensing field-effect transistor The biosensor can be combined with the measurement circuit on a single chip to achieve miniaturization of the sensing element. (2) Teruaki Katsube, Shuichiro Yamaguchi, Naoto Uchida, Takeshi Shimomura, USP 5,296, 122; Date of Patent: March 22, 1994 "Apparatus for forming thin Him", this patent makes a hydrophobic film as an ion sensing field effect The reference electrode of the transistor. This hydrophobic film can be grown on the substrate by using the dry material of the hydrophobic film in a neutral plasma or splatter method. This instrument includes a vacuum cavity, an atomic beam generator, and a target base. Shields for controlling growth, etc. This film is suitable for the use of ion sensors, such as ion-sensing field effect transistors and enzyme sensors. (3) Barry W. Benton, USP 5,833,824; Date of Patent ·· Nov. 10, 1998 "Dorsal substrate guarded ISFET sensor", this patent proposes an ion-sensing field effect transistor sensor to detect ions in solution The activity of this sensor includes a semiconductor wafer with a substrate and an ion-sensing field effect transistor. The surface of the substrate is in contact with the solution, the back surface is opposite to the substrate surface, and a hole is connected to the surface and the back of the substrate. The field-effect transistor has an ion sensing region in the gate region, the ion sensing region is in contact with the back surface, and the gate region is brought into contact with the solution by using a hole. (4) James G. Connery, Jr. Shaffer, W. Earl, USP 4,879,517; Date of Patent · · Nov. 7, 1989 "Temperature compensation for potentiometrically operated ISFETS", this patent is an ion-sensing field effect transistor Temperature compensation circuit, the source-drain voltage and the drain current of the ion-sensing field-effect transistor are fixed, according to the Nernst temperature effect on the output effect of the ion-sensing field-effect transistor. Measure the zero potential point of the probe, modify the working condition of the sensing element to zero temperature potential, to reduce the effect of temperature on the sensing element, and make a set of ion sensing field effect transistor and field effect transistor to eliminate the element production error. (i) Hendrik H. vd Vlekkert, Nicolaas F. de Rooy, USP 4,691,167; Date of Patent: Sep. 1,1987 "Apparatus for Chun determining the activity of an ion (plon) in a liquid", this patent system A device for measuring the ion activity of a solution is proposed. The device includes a measurement circuit. The circuit includes: an ion-sensing field effect transistor, a reference electrode, and a temperature sensor. The amplifier includes: an ion-sensing field effect transistor. Crystal, temperature sensor and control, calculation, memory circuit, and can operate VGS, VDS, IDS and other three parameters at a constant value. Using the control of these three parameters will detect the activity of ions, and the ion sensing characteristics have temperature variation. Characteristics, and IDS has a functional relationship with respect to temperature, so the function stored in memory can be used to control VGS to achieve compensation of temperature characteristics. (6) Mathias Krauss, Beate Hildebrandt, Christian Kunath, Eberhard Kurth, USP 5,602,467; Date of Patent · · Feb. 11, 1997 "Circuit for measuring ion concentrations in solutions", this patent proposes the use of ion sensing field effect transistors The structure of the circuit layout measures the concentration of ions in the solution. This circuit layout enables the ion sensing of the gate voltage difference of the 9 field effect transistor, the parameter deviation and the environment due to operating factors, and the difference can be displayed. This circuit layout includes two measurement and test amplifiers, and two ion-sensing field-effect transistors and the same field-effect transistor. This ion-sensing field-effect transistor is connected to the field-effect transistor. The output shows the change in the gate dust of the two-ion sensing field-effect transistor and the field-effect transistor, and the second one shows the output difference between the two-ion sensing field-effect transistor. The reference electrode connected to the ground terminal of the four reference electrodes can detect the ion concentration with this architecture. According to related research, it can be found that the solid-state dry reference electrode and the planar sensing π component architecture are both related problems to be solved at present. According to the structure proposed by the present invention, the dry storage and planar architecture of the sensing element can be achieved. . It can be seen that there are still many shortcomings in the above-mentioned conventional techniques, and they are not a good designer, and need to be improved. In view of the various shortcomings derived from the above-mentioned sensing device, the inventor of this case is eager to improve and innovate, and after years of painstaking research, he successfully researched "70 Cost Parts to Make Differential Pairs with Conductive Polymers" Method for acid-base sensing element. [Summary of the Invention] The purpose of this Maoming is to provide a method for making a differential acid proof sensing element using a conductive polymer, which is a planar ion sensor, which combines a semiconductor process with a conductive polymer Aggregation to make. The present invention uses conductive polymers to make ... Ion sensors with "sensing characteristics, the characteristics of which are conductive rooms can be controlled by controlling 1 ^^ # A /, Λ σ The measuring element is used in the production of differential wire 斟 η ㈣ ion m pieces. It can achieve the control of the special test electrode and reference electrode of the differential pair ion sensing element made of tin dioxide, which are made of solid semiconductors. The flat structure. Therefore, the sensor of this invention, U-shaped parts, flat structure, dry storage, easy to manufacture and so on. To achieve the above purpose, the conductive polymer is used to make differential acid-base sensing ^ ^ The method is to use semiconductor ore film technology to deposit a solid sensing conductive sub-film on a substrate. In order to use electropolymerization technology, conductive polymer is polymerized and fixed on the conductive solid film. The process steps are as follows: Step 1: Prepare for cleaning Clean indium tin oxide glass; Step 2 Step 3 Step 4 Step 5 Sputterer deposit tin oxide thin film; component wire; use epoxy resin to package appropriate sensing area; In the electropolymerization solution, the electropolymerization of a conductive polymer, that is, the fabrication of a differential pair ion sensing element. [Embodiment] Please refer to FIG. 1 (a) and FIG. 1 (b) for the month. As shown in the figure, the manufacturing flow chart of a method for making a differential acid-base sensing element by a molecule and a conductive polymer sensor is shown in the figure.

....... £ L The method of making a differential pair of acid-sensing sensing elements is based on the use of semiconductor keying film technology in the base & sinking_state_film with high conductivity. The molecular film 'is the use of electropolymerization technology to polymerize and fix conductive polymers on conductive rhenium films. The process steps are as follows: Step-. Prepare various types of mu substrates (such as insulating substrates, conductive substrates, etc.)' The selection of the substrate is mainly to select a suitable substrate 1 considering the solid-state sensing material and the detection environment; Step 2 ·· Clean the substrate 2; Step 3: Deposit the solid-state sensing material on the substrate (such as tin dioxide sensing material, etc.) 3; Step 4: Component cable 4; Step 5: Encapsulate the material with epoxy resin and fix the sensing window area 5; ^ Step 8: Put the element into the electropolymerization solution, and the electropolymerized conductive polymer will be ' Fabrication of Wucheng Differential Pair Ion Sensing Element 6. The detailed process steps of polymerizing the conductive polymer in the above step 6 are as follows: · Step A: Prepare the finished conductive substrate (such as: tin dioxide / tin oxide glass) substrate selection mainly considering the surface conductive material conductivity 61; Step B: cleaning the substrate 62; step V. preparing an electropolymerization solution, the electropolymerization solution contains monomers such as a buffer solution, an electrolyte, and a conductive polymer (such as: a light salt solution, potassium gas, poly_stone ratio ( Polypyrrole)) 63; 12 .. 丄 i—! ».! Π i Step D: Connect the substrate to the positive + of the power supply, and connect the platinum electrode to the negative of the power supply. Road-Negative U shout, the power supply provides a constant potential higher than the oxidation potential of the conductive plutonium molecule by 15 males ... Potential of 15 knives (eg, 4V when electropolymerized polyfluorene), which can polymerize conductive polymers on the substrate 64; Step E: Put the conductive polymer sensor to clean the conductive polymer sensor 65; Place the sensor in deionized water for 10 minutes. Step F: Take out the sensing element and place it to dry test. 70% of the conductive polymer The production of sensor 66. Please refer to FIG. 2 (b) and FIG. 2 (b), which are a plan view and a cross-sectional view of the method for manufacturing a differential acid proof sensing element using a conductive polymer. As can be seen from the figure, the differential acid proof sensing of the present invention Element 7, which is a tin oxide residue 73 deposited on a glass-breaking substrate 71 with indium tin oxide 72, is in the form of a coin state ion sensor, and then the acid value of the solution is measured, and the conductive wire% is used as a signal transmission wheel. Zhuang encapsulates the non-sensing area with epoxy resin vinegar 75 and other packaging materials, and uses packaging technology to define the sensing element sensing compensation to make acid-base sensors and incoming electrodes; Put some of the manufactured parts into the conductive polymer polymerization solution, and polymerize polyfluorene 76 on -Tongwu class # ,,, and tin reduction sensor 73 to complete the sensor molecule acid detection sensor; Two 〇_ ㈡〒—a sensing window 81, 82, 83, respectively representing different electrodes, one for the φ and the reference potential electrode, which is achieved by using one of the tin sensing windows. Phantom horse for the standard potential of the sensing element; another sensing window for tritium oxide #work; ^ A is regarded as & alkali sensor, using its high sensing characteristics, 13 as the main acid-base sensor; and the conductive polymer sensor has the characteristics of controlling acid detection, in the present invention will Control its sensing characteristics to be stable and low sensing. Using the characteristics of these three electrodes, the differential pair electrochemical ion sensing element 7 of the present invention is composed. Please refer to Figure 3, which is the intention of measuring the electropolymerization potential of the conductive polymer. From the figure, it can be seen that the component is placed in an electropolymerization buffer solution. This electropolymerization solution contains buffer solutions, salts, conductive polymers and other substances. The buffer solution provides a stable polymerization environment, such as: _salt solution, co-test solution, etc., and adjusts the conductive characteristics of the electropolymerization solution with salts, such as potassium chloride, sodium gasification, etc. Conductive polymer polymerization, such as polyfluorene, polyaniline, etc., to make a conductive polymer sensor, because the acid-base sensing characteristics of the conductive polymer will change with the electropolymerization environment, so it can be adjusted The ratio of the electropolymerized solution is used to control the sensing characteristics of the conductive polymer, so as to make a stable differential pair structure ion sensor. Please refer to Figure 4 for the measurement of the oxidation potential of the conductive polymer polymer. From the figure, we can know that in order to know whether the electropolymerization environment of the conductive polymer is appropriate and to choose the best electropolymerization potential, the cyclic voltammetry is used to measure Measurement of conductive high score: the oxidation potential 'measurement architecture diagram, the auxiliary electrode is a platinum electrode, the guard electrode is a tin dioxide film, and the reference electrode is a silver / silver chloride electrode. Refer to Figure 5 'for the electropolymerization architecture diagram of the conductive polymer ion sensing element. As can be seen from the figure, this characteristic curve is a schematic diagram of the conductive polymer current corresponding to the potential 14. According to the figure, the conductive volts can be judged, so when the electropolymerization If the potential is higher than 1.4, the resistance characteristics will increase, and the volts will polymerize the conductive polymer film and the electropolymer ion sensing element. The oxidation potential of the polymer is about 1.4 volts, so the conductive polymer is too high. Therefore, the present invention uses a higher potential 4 to make a guide with lower sensing characteristics (see Figure 6u) and Figure 6 (b). The characteristic measurement architecture diagrams of the ion sensing element and the differential pair structure sensing element are respectively shown in the figure. The single sensing element 'tin oxide sensing element and conductive polymer sensor can be seen in Figure 6_ ( 〇The readout circuit is used to capture the signal. This readout circuit can use circuits with high input impedance, such as metal oxide half field effect transistors, operational amplifiers, instrumentation amplifiers, etc. The surface potential of the sensing element varies with the acid of the solution to be measured. Different base values will change accordingly. 'Single detection of the sensing element can be obtained. The readout circuit architecture of the differential pair ion sensing element is shown in Figure 6 (b). Medium — For the tin dioxide sensing element, one is connected to the ground terminal and the other is connected to the negative input terminal of the instrumentation amplifier to form a reference potential electrode and an acid-base sensing electrode, and the molecular electrode is connected to Instrumentation amplifier positive input, this is The measurement structure of the differential pair of sensing elements. Please refer to Figure 7 for the calibration curve of the sensing characteristics of tin dioxide / indium tin oxide glass sensing elements. As can be seen from the figure, this characteristic curve is a single tin dioxide / Calibration curve of sensing characteristics of indium tin oxide glass sensing element. According to this figure, we can know that the characteristic of this sensing element is stable and has a high degree of sensitivity. It is 57 ”millivolts / 15

PH value, so it can be used as the main acid-base sensing element. Please refer to FIG. 8, which is a calibration curve of the sensing characteristics of polyfluorene / tin dioxide / indium tin oxide glass sensing elements. As can be seen from the figure, this characteristic curve is a polymer_ / tin oxide / indium tin oxide glass sensor. The calibration curve of the sensing characteristics of the measuring element. According to this figure, we can know that the characteristics of the sensing element are fixed. It has a low sensitivity and is 27.81 volts / acid value, so it can be used as a differential pair ion sensing element. Acid detection sensor. Please refer to FIG. 9, which is a sensing characteristic curve diagram of the method for making a differential pair acid-base sensing element using a conductive polymer. As can be seen from the figure, this characteristic curve is that the differential pair ion sensing element is placed in different When the acid-base solution is used, the output potential change curve of the sensing element within one minute. According to this figure, it can be found that the stability of the sensing element is good. When placed in different acid-base solutions, the output potential of the sensing element also varies with As a result, the sensing element is a good acid-base sensing element, which can be used to detect the pH value of the solution to be tested. Please refer to FIG. 10, which is a calibration curve of the sensing characteristics of the method of making a differential pair of acid-base sensing elements using conductive polymers. As can be seen from the figure, in order to discuss the stability of the sensing child process, Differential pair-type acid-base sensing elements, measure their sensing characteristics separately. It is known from the figure that the sensing element has good sensing linearity, and each sensor's characteristic error is small, which is a good acid test.测 ELECTRONICS. The above detailed description is a specific description of one of the feasible embodiments of the present invention, but this embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or change without departing from the technical spirit of the present invention, All should be included in the patent scope of this case. In summary, this case is not only innovative in terms of technical ideas, but also can be compared. The use of articles to enhance the above-mentioned multiple effects should have fully met the novelty and progressiveness-the statutory invention patent elements, and applied in accordance with the law. The Bureau approves this patent application for invention to encourage invention and it is a matter of virtue. [Brief description of the figure] Figure 1 (a) is a process flow chart of a method for making a differential pair acid-base sensing element using conductive polymers according to the present invention; Figure 1 (b) is a schematic view of the conductive polymer sensor Process flow chart; Figure 1 (a) is a top view of the method for manufacturing a differential acid-base sensing element using a conductive polymer; Figure 2 (b) is a method for manufacturing a differential acid-base sensing element using a conductive polymer Sectional view of the method; Figure 3 is a schematic diagram of the measurement of the electropolymerization potential of the conductive polymer; Figure 4 is a measurement diagram of the oxidation potential of the conductive polymer polyfluorene; Figure 5 is a schematic diagram of the electropolymerization structure of the conductive polymer ion sensing element; /, (A) is a characteristic measurement architecture diagram of an ion sensing element; Figure 6 u) a characteristic measurement architecture diagram of a differential pair architecture sensing element;

Figure 7 is a cross-sectional diagram of the sensing characteristics of tin dioxide / indium tin oxide glass sensing element; X 17 1227779 Calibration curve of sensing characteristics of tin / indium tin oxide glass sensing element; Figure 9 is the sensing characteristic curve of the method for making a differential pair acid-base sensing element using a conductive polymer; and-Figure 10 is the conductive A polymer-made differential / acid-based sensing characteristic correction curve diagram of an acid-base sensing element. [Representative symbols for main parts] 7 Differential pair of acid-base sensing elements 71 Glass substrate 72 Indium tin oxide 73 Tin dioxide sensing film 74 Conductive wire 75 Epoxy resin 76 Polycarbonate 81 Sensing window 82 Sensing Window 83 sensing window 18

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Claims (1)

1221779 ^ The scope of patent application: 1 _ — A method of making a differential pair acid-base sensing element based on the guide Legu v. Electricity as a sub, the process steps are as follows: less steps · Preparation of various solid-state substrates, the main choice of substrates In order to consider the solid state sense, the material and the detection environment are selected as appropriate substrates; Step 2 · Depositing solid sensing materials on the substrate; Step 3: Component wire; Step 4: Encapsulating and fixing the material with% oxygen resin Sensing window area; Step 5: Put the element into the electropolymerization solution and electropolymerize the conductive polymer to complete the fabrication of the differential acid-base sensing element. 2. If the scope of patent application is the first! The method for producing a differential acid-base sensing element using a conductive polymer as described in the above item, wherein the process steps of the electropolymerized conductive polymer are as follows: Step A: Prepare a completed conductive substrate; Step B ·· Prepare an electropolymer solution , This level person The electrolyte solution contains the positive electrode of the buffer solution, the platinum electrode is connected to the solution, and the power supply unit provides a position to polymerize the conductive high-electrolyte and conductive polymer monomers. Step D ·· Connect the substrate to the power supply of the power supply The negative electrode of the supplier is placed on the substrate with a fixed electron having an electropolymerization higher than the oxidation potential of the conductive polymer; Step E ·· The conductive polymer sensor is placed in the deionized water to clean 23 3 Step F of the sauce factory: Take out the sensing element and dry it, and then the conductive polymer sensor is completed. The method for manufacturing a differential pair acid-base sensing element using a conductive polymer as described in item 1 of the scope of the patent application, wherein the solid substrate may be composed of a silicon substrate, a glass substrate, a ceramic substrate, or a polymer polymer substrate. The method for manufacturing a differential pair acid-base sensing element using a conductive polymer as described in item 1 of the scope of the patent application, wherein the sensing material may be composed of tin dioxide or other solid conductive ion sensing membranes. S. The method for producing a differential acid-base sensing element using a conductive polymer as described in item 1 of the scope of the patent application, wherein the conductive polymer polymerization solution includes a buffer solution, salts, and a conductive polymer, such as The electropolymerization solution of phosphate solution, potassium chloride, and polymer materials can be used to change the composition of the polymer solution. It can be used to control the sensing characteristics of the polymer polymer sensor. In the future, this technology can be used to produce appropriate sensing characteristics. The opposite sensing electrodes are used to control the sensing characteristics of the differential pair of sensing elements. 6. A method for making a differential acid-base sensing element using a conductive polymer is to deposit a non-insulating solid-state ion sensing film on an insulating substrate or a non-insulating substrate, and use conductive wires as a reduction transmission line. The encapsulation materials such as vinegar cover the non- 封装 m-domain package, and the encapsulation technology defines the sensing area of the sensing element to make the acid-base sensor and the reference electrode; after that, the fabricated component is placed in a conductive polymer polymerization solution. The polymer batch 24 was polymerized on a tin dioxide film to make a conductive polymer sensor. The characteristics of the electrode formed by the three sensing windows, that is, the composition of the differential pair electrochemical ion sensing element. The method for manufacturing a differential acid-base sensing element using a conductive polymer as described in item 6 of the scope of the patent application, wherein the three sensing windows are a reference potential electrode, a conductive polymer sensor, and an acid-base sensor, respectively. Device. 8. As described in item 6 of the scope of the patent application, a method for manufacturing a differential acid-base sensing element using a conductive polymer, wherein the electrodes are all solid-state electrodes and = planar structure, and do not need to be immersed in a buffer solution for storage. Therefore, the characteristics of simple storage are not easily affected by environmental influences. 25