Miniature dry-method reference electrode as well as preparation method and application thereof

Abstract

The invention provides a miniature dry-method reference electrode and a preparation method and application thereof, and relates to the technical field of reference electrodes, and the preparation method comprises the following steps: sequentially preparing a conductive layer, a silver paste layer and an electrolyte layer on a substrate in a laminated manner; the electrolyte layer is prepared by the following steps: applying electrolyte slurry on a silver slurry layer to form a prefabricated electrolyte layer; the electrolyte slurry comprises potassium chloride and sodium alginate; and applying a calcium ion-containing solution on the prefabricated electrolyte layer to obtain the electrolyte layer. Electrolyte slurry containing potassium chloride and sodium alginate is adopted to prepare a prefabricated electrolyte layer, a stable dry electrolyte layer is formed through cross-linking and curing of a calcium ion solution, sodium alginate forms hydrogel with a three-dimensional cross-linked network structure under the action of calcium ions, the release rate of potassium chloride can be effectively regulated and controlled through the pore structure of the hydrogel, and the stability of the hydrogel is improved. The concentration of Cl <-> can still be kept stable for a long time after the Cl <-> is in contact with a sample, and the reference electrode prepared by adopting the preparation method has good electrochemical stability.

Description

Technical Field

[0001] This invention relates to the field of reference electrode technology, and in particular to a micro dry reference electrode, its preparation method, and its application. Background Technology

[0002] In the field of electrochemical sensing, the reference electrode is a key component that ensures the stability of the working electrode potential and the accuracy of measurement results. Traditional Ag / AgCl reference electrodes are widely used in various electrochemical sensors.

[0003] However, traditional Ag / AgCl reference electrodes still have the following drawbacks:

[0004] First, it is highly dependent on saturated electrolytes. In traditional Ag / AgCl reference electrodes, the reference electrode will respond to different concentrations of Cl. - The spontaneous reassembly and decomposition of AgCl occurs, affecting Cl. - To generate a Nernst response, conventional commercial integrated electrochemical sensing products typically have a saturated electrolyte and a polymer film sequentially coated on top of the reference electrode Ag / AgCl to maintain a stable Cl concentration in the reference electrode Ag / AgCl, thus maintaining a stable reference potential. However, even so, after the intermediate saturated electrolyte absorbs the sample, its saturated Cl ion concentration is still rapidly diluted by the sample, thereby affecting the entire reference electrode potential.

[0005] Secondly, their complex structure hinders miniaturization and integration. Existing reference electrodes often require liquid junction structures (such as ceramic cores or microporous membranes) to control ion exchange between the electrolyte and the sample. Such structures are not only complex to manufacture, but also prone to clogging under long-term use or continuous flow conditions, affecting electrode stability, increasing maintenance costs, and making them difficult to integrate into microfluidic chips.

[0006] Secondly, its electrode stability is poor. If the saturated electrolyte protective layer is omitted and only the bare Ag / AgCl structure reference electrode is used, the bare Ag / AgCl will directly respond to the chloride ions in the sample. However, researchers do not want Ag / AgCl to respond to the sample, but only want it to remain stable.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] One of the objectives of this invention is to provide a method for preparing a micro dry reference electrode, so as to at least solve one of the technical problems existing in the prior art.

[0009] The second objective of this invention is to provide a miniature dry reference electrode.

[0010] The third objective of this invention is to provide an application of a miniature dry reference electrode in the fabrication of electrochemical sensors.

[0011] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0012] In a first aspect, the present invention provides a method for preparing a micro dry reference electrode, comprising the following steps: sequentially stacking a conductive layer, a silver paste layer and an electrolyte layer on a substrate;

[0013] The electrolyte layer is prepared by the following method:

[0014] (a) An electrolyte slurry is applied to the silver paste layer to form a pre-prepared electrolyte layer; wherein the electrolyte slurry comprises potassium chloride and sodium alginate.

[0015] (b) A calcium-containing solution is applied to the pre-prepared electrolyte layer to obtain the electrolyte layer. Further, the electrolyte slurry comprises a saturated potassium chloride solution and sodium alginate;

[0016] Preferably, the electrolyte slurry contains 34.7g KCl and 1-3g sodium alginate per 100g of water;

[0017] Preferably, the electrolyte slurry further comprises a hydrogel;

[0018] Preferably, the electrolyte slurry contains 34.7g KCl, 1-3g sodium alginate and 1-3g hydrogel per 100g of water.

[0019] Furthermore, the calcium-containing solution includes one or more of calcium chloride solution and / or calcium sulfate solution;

[0020] Preferably, the mass concentration of the calcium ion-containing solution is 2%-4%.

[0021] Furthermore, the thickness of the electrolyte layer is 15-50 μm.

[0022] Furthermore, the thickness of the conductive layer is 20-50 μm;

[0023] Preferably, the preparation process of the conductive layer includes: applying the raw materials for preparing the conductive layer onto the substrate, followed by a curing process to obtain the conductive layer;

[0024] Preferably, the raw materials for preparing the conductive layer include one or more of carbon, gold, and platinum;

[0025] Preferably, the conductive layer paste is applied by one or more of the following methods: screen printing, chemical deposition, electroplating, vacuum sputtering, and spray coating.

[0026] Preferably, the temperature of the first curing treatment is 100-150℃, and the time of the first curing treatment is 10-20 minutes.

[0027] Furthermore, the thickness of the silver paste layer is 10-40 μm;

[0028] Preferably, the preparation process of the silver paste layer includes: applying silver paste to the conductive layer, followed by a secondary curing process to obtain the silver paste layer;

[0029] Preferably, the silver paste layer comprises Ag / AgCl paste;

[0030] Preferably, the silver paste layer is applied by spraying or dispensing and / or screen printing.

[0031] Preferably, the temperature of the secondary curing treatment is 100-150℃, and the time of the secondary curing treatment is 5-15 minutes.

[0032] Furthermore, the preparation method further includes: preparing a protective film layer on the electrolyte layer;

[0033] Preferably, the thickness of the protective film layer is 5-60 μm;

[0034] Preferably, the preparation process of the protective film layer includes: applying a protective film layer slurry onto the electrolyte layer to obtain the protective film layer;

[0035] Preferably, the components of the protective film slurry include: PDMS, curing agent, and cyclohexane;

[0036] Preferably, the protective film slurry comprises, by mass percentage: 15%-20% PDMS, 1%-3% curing agent, and the balance cyclohexane.

[0037] Furthermore, the substrate includes one or more of PCB substrates, ceramic substrates, PVC and flexible polyester substrates.

[0038] Secondly, the present invention provides a miniature dry reference electrode, which is prepared using the aforementioned preparation method.

[0039] Thirdly, the present invention provides an application of a miniature dry reference electrode in the fabrication of electrochemical sensors.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The present invention provides a method for fabricating a miniature dry reference electrode by sequentially forming a conductive layer, a silver paste layer, and an electrolyte layer on a substrate. Specifically, a pre-prepared electrolyte layer is prepared using an electrolyte slurry containing potassium chloride and sodium alginate. Subsequently, a stable dry electrolyte layer is formed through cross-linking and curing with a calcium ion solution. This method eliminates the need for traditional liquid saturated electrolytes and complex liquid junction structures, effectively solving the technical problems of existing reference electrodes in miniaturized applications, such as strong dependence on saturated electrolytes, complex structures, and poor stability. Specifically, sodium alginate forms a hydrogel with a three-dimensional cross-linked network structure under the action of calcium ions. Its pore structure can effectively regulate the release rate of potassium chloride, allowing Cl... - The concentration remains stable for a relatively long time after contact with the sample.

[0042] The preparation method is simple and low-cost, and is suitable for mass production methods such as screen printing. The obtained reference electrode not only has good long-term electrochemical stability, but also has a compact structure and requires no maintenance. It is particularly suitable for integration into disposable electrochemical sensor strips and microfluidic chip systems, and has good application prospects. Attached Figure Description

[0043] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0044] Figure 1 A cross-sectional view of a micro dry reference electrode provided in an embodiment of the present invention.

[0045] Icons: 1 - First groove; 2 - Second groove; 3 - Third groove. Detailed Implementation

[0046] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0047] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] The first aspect of the present invention provides a method for fabricating a micro dry reference electrode, comprising the following steps: sequentially stacking a conductive layer, a silver paste layer and an electrolyte layer on a substrate;

[0049] The electrolyte layer is prepared by the following method:

[0050] (a) An electrolyte slurry is applied to the silver paste layer to form a pre-prepared electrolyte layer; wherein the electrolyte slurry comprises potassium chloride and sodium alginate.

[0051] (b) Apply a calcium ion-containing solution to the pre-prepared electrolyte layer to obtain the electrolyte layer.

[0052] In some preferred embodiments, the electrolyte slurry comprises a saturated potassium chloride solution and sodium alginate;

[0053] Preferably, the electrolyte slurry contains 34.7g KCl and 1-3g sodium alginate per 100g of water. Sodium alginate is preferably 2g.

[0054] "1-3g" can be, for example, 1g, 1.5g, 2g, 2.5g, 3g, etc.

[0055] Preferably, the electrolyte slurry further comprises a hydrogel;

[0056] Preferably, the electrolyte slurry contains 34.7g KCl, 1-3g sodium alginate, and 1-3g hydrogel per 100g of water. The hydrogel is preferably 2g; more preferably, it is a D5 hydrogel, a low-viscosity ether-containing polyurethane hydrogel.

[0057] "1-3g" can be, for example, 1g, 1.5g, 2g, 2.5g, 3g, etc.

[0058] In this invention, adding D5 hydrogel to the electrolyte slurry can promote better cross-linking of the electrolyte layer and give it superior water absorption properties.

[0059] In some preferred embodiments, the calcium-containing solution includes one or more of calcium chloride solution and / or calcium sulfate solution;

[0060] Preferably, the mass concentration of the calcium ion-containing solution is 2%-4%, for example, it can be 2%, 2.5%, 3%, 3.5%, 4%, etc.

[0061] In some preferred embodiments, the thickness of the electrolyte layer is 15-50 μm, for example, it can be 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc.

[0062] In this invention, the electrolyte layer is a dry electrolyte layer (KCl-sodium alginate complex), which is formed by Ca... 2+ Cross-linking and curing, no liquid electrolyte required.

[0063] In some preferred embodiments, the thickness of the conductive layer is 20-50 μm, for example, it can be 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc.

[0064] Preferably, the preparation process of the conductive layer includes: applying the raw materials for preparing the conductive layer onto the substrate, followed by a curing process to obtain the conductive layer;

[0065] Preferably, the raw materials for preparing the conductive layer include one or more of carbon, gold, and platinum;

[0066] Preferably, the conductive layer paste is applied by one or more of the following methods: screen printing, chemical deposition, electroplating, vacuum sputtering, and spray coating.

[0067] Preferably, the temperature of the first curing treatment is 100-150℃, for example, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, etc.; the time of the first curing treatment is 10-20 minutes, for example, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, etc.

[0068] In some preferred embodiments, the thickness of the silver paste layer (also known as the reference electrode layer) is 10-40 μm, for example, it can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, etc.; the thickness of the silver paste layer is preferably 20 μm.

[0069] Preferably, the preparation process of the silver paste layer includes: applying silver paste to the conductive layer, followed by a secondary curing process to obtain the silver paste layer;

[0070] Preferably, the silver paste layer comprises Ag / AgCl paste;

[0071] Preferably, the silver paste layer is applied by spraying or dispensing and / or screen printing; screen printing is preferred.

[0072] Preferably, the temperature of the secondary curing treatment is 100-150℃, for example, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, etc.; the time of the secondary curing treatment is 5-15 minutes, for example, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, etc.

[0073] In some preferred embodiments, the preparation method further includes: preparing a protective film layer on the electrolyte layer;

[0074] Preferably, the thickness of the protective film layer is 5um-60um, for example, it can be 5um, 10um, 15um, 20um, 25um, 30um, 35um, 40um, 45um, 50um, 55um, or 60um;

[0075] Preferably, the preparation process of the protective film layer includes: applying a protective film layer slurry onto the electrolyte layer to obtain the protective film layer;

[0076] Preferably, the components of the protective film slurry include: PDMS (polydimethylsiloxane), curing agent, and cyclohexane;

[0077] Preferably, the protective film slurry comprises, by mass percentage: 15%-20% PDMS, 1%-3% curing agent, and the balance cyclohexane.

[0078] Among them, based on the total mass of the protective film slurry as 100%, the amount of PDMS added is 15%-20%, for example, it can be 15%, 16%, 17%, 18%, 19%, 20%, etc.;

[0079] The amount of curing agent added is 1%-3%, based on the total mass of the protective film slurry as 100%, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0080] In some preferred embodiments, the substrate includes one or more of a PCB substrate, a ceramic substrate, a PVC substrate, and a flexible polyester substrate.

[0081] A second aspect of the present invention provides a miniature dry reference electrode, which is prepared using the aforementioned preparation method.

[0082] The working principle of the reference electrode is as follows: The Ag / AgCl reference electrode is based on the core principle of reversible electrochemical reaction, which can maintain a relatively constant potential. The chemical reaction is as follows:

[0083]

[0084] Its electrode potential (E) is determined by the Nernst equation:

[0085]

[0086] Where: E 0 This is the standard electrode potential; a Cl - For Cl - The activity of the gas; R is the gas constant, T is the temperature (K), and F is the Faraday constant.

[0087] In other words, the stability of the reference electrode potential depends critically on Cl. - In this invention, the electrolyte layer consists of sodium alginate gel and saturated KCl, which, after drying, forms a solid but hydrated matrix. When the test solution comes into contact with the gel, the gel absorbs water and swells, releasing the internally fixed KCl, forming a locally high Cl concentration on the Ag / AgCl electrode surface. - Concentration environment (near saturation).

[0088] This invention successfully fabricates a precise, disposable planar Ag / AgCl reference electrode with an internal electrolyte using a screen printing process. The internal electrolyte layer is printed using a sodium alginate electrolyte slurry containing KCl, and the sodium alginate is processed through Ca... 2 Cross-linking forms a three-dimensional network structure, the pore size of which restricts the rapid diffusion of KCl. Experiments show that the release rate of KCl from the gelled electrolyte layer is slow (significant dilution only occurs after 20 minutes), thus delaying the release of Cl. - Changes in activity. The ion exchange selectivity of the gel preferentially retains Cl-. - This further stabilizes the local ion environment.

[0089] Experimental results from this invention demonstrate that the electrode exhibits long-term potential stability (approximately 20 minutes), and its performance is unaffected by Cl. - Concentration effect. This electrode can be used in disposable strip-based sensing technology and has broad application prospects.

[0090] Furthermore, the miniature dry reference electrode provided by this invention has the following advantages:

[0091] (1) No saturated electrolyte solution required: The electrolyte layer in this invention is a cross-linked layer, and the reference electrode of this invention is an all-solid-state electrode. The dry electrolyte layer avoids the traditional liquid junction blockage problem and is suitable for microfluidic integration.

[0092] (2) Miniaturization and low cost: Screen printing process simplifies the structure and is suitable for mass production of disposable sensor strips.

[0093] (3) Long-term stability: The degradation rate of Ag / AgCl decreased and the potential drift was significantly improved.

[0094] In a preferred embodiment of the present invention, the method for fabricating the micro dry reference electrode includes the following steps:

[0095] Step 1: Prepare the conductive layer: Print carbon paste on the substrate, then perform a curing treatment at 100-150℃ for 10-20 minutes to form a graphite conductive layer. The substrate thickness is 0.5-1.6 mm.

[0096] Step 2: Prepare the silver paste layer: Print the silver paste onto the conductive layer, and then perform a secondary curing treatment at a temperature of 100-150℃ for 5-15 minutes to form the silver paste layer.

[0097] Step 3: Prepare electrolyte layer: Print electrolyte paste on silver paste layer to form pre-electrolyte layer, then spray 2%-4% CaCl2 solution on the surface of pre-electrolyte layer for gelation. After cross-linking reaction, electrolyte layer is transformed into hydrogel. Finally, dry at room temperature for 24 hours.

[0098] The preparation process of the electrolyte slurry is as follows: sodium alginate is added to a saturated KCl solution at room temperature (25℃), and stirred at room temperature for 0.5h. Then D5 hydrogel is added and stirred at room temperature for 24h to form a mixed slurry. The electrolyte slurry formula is: 34.7g KCl, 1-3g sodium alginate and 1-3g hydrogel per 100g of water.

[0099] Step 4: Prepare the protective film layer: such as Figure 1 As shown, the protective film slurry is applied onto the electrolyte layer via a dispensing process to form a coating structure; wherein, the protective film slurry composition is preferably 18% PDMS, 2% curing agent and 80% cyclohexane by mass percentage.

[0100] It should be noted that, regarding the structure of the micro dry reference electrode, specifically, before fabricating the micro dry reference electrode, it is necessary to groove the substrate (either circular or square grooves are acceptable), and the subsequent conductive layer, silver paste layer, electrolyte layer, and film layer are all disposed in the above-mentioned grooves.

[0101] Optionally, such as Figure 1As shown, a first groove 1 is formed on the substrate; a second groove 2 is formed by continuing to groove downwards on the bottom of the first groove 1; a third groove 3 is formed by continuing to groove downwards on the bottom of the second groove 2; wherein the groove diameters of the first groove 1, the second groove 2, and the third groove 3 decrease sequentially. A conductive layer and a silver paste layer are prepared in the third groove 3, an electrolyte layer is prepared in the second groove 2, and a film layer is prepared in the first groove 1. The following embodiments and comparative examples use this micro dry reference electrode structure, and the grooves are preferably circular.

[0102] Furthermore, it should be noted that the depth of each groove is set according to the thickness of the corresponding functional layer to accommodate the conductive layer, reference electrode layer, electrolyte layer, and protective film layer. The specific depth parameters are determined according to process requirements. Optionally, the depth of the third groove 3 is not less than the sum of the thicknesses of the conductive layer and the reference electrode silver paste layer, the depth of the second groove 2 further accommodates the electrolyte layer, and the first groove 1 is adapted to the overall height of the protective film layer (or, depending on actual needs, the protective film layer may protrude slightly beyond the first groove 1), thereby achieving a multi-layer stepped embedded packaging structure.

[0103] A third aspect of the present invention provides an application of a miniature dry reference electrode in the fabrication of an electrochemical sensor.

[0104] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0105] The Ag / AgCl slurry used in the following examples and comparative examples is Ag / AgCl slurry from Shanghai Julong Electronics Technology Co., Ltd., model: JLL11; the D5 hydrogel is the D5 model hydrogel produced by HnG Medical Technology Co., Ltd. of Canada; and the substrate is a ceramic substrate with a thickness of 1mm.

[0106] The reference electrode structure in the following embodiments and comparative examples is as follows: a circular groove is formed on the substrate, wherein the diameter of the first groove 1 is 1500 μm, the diameter of the second groove 2 is 1200 μm, and the diameter of the third groove 3 is 800 μm. The conductive layer and the silver paste layer are prepared in the third groove 3, the electrolyte layer is prepared in the second groove 2, and the protective film layer is prepared in the first groove 1.

[0107] Example 1

[0108] This embodiment provides a miniature dry reference electrode, the preparation method of which includes the following steps:

[0109] Step 1: Prepare the conductive layer: Print carbon paste on the substrate, and then cure it at 120°C for 15 minutes to form a graphite conductive layer with a thickness of 35µm.

[0110] Step 2: Prepare the silver paste layer: Print the Ag / AgCl silver paste onto the conductive layer, and then cure it at 120°C for 10 minutes to form the silver paste layer. The thickness of the Ag / AgCl silver paste layer is 20 μm.

[0111] Step 3: Preparation of electrolyte layer: Electrolyte paste is printed on the silver paste layer to form a pre-electrolyte layer. Then, a 3% CaCl2 solution is sprayed onto the surface of the pre-electrolyte layer for gelation. The amount of CaCl2 solution used is 0.5 μL (it should be noted that 0.5 μL is a fixed amount, and 0.5 μL of CaCl2 solution is sprayed on each sensor). After the cross-linking reaction occurs, the electrolyte layer is transformed into a hydrogel. Finally, it is dried at room temperature for 24 hours, and the thickness of the electrolyte layer is 20 μm.

[0112] The preparation process of the electrolyte slurry is as follows: at room temperature (25℃), 0.2g of sodium alginate is added to a saturated KCl solution (10g of water and 3.47g of KCl), and stirred at room temperature for 0.5h. Then, 0.2g of D5 hydrogel is added, and stirred at room temperature for 24h to form a mixed slurry.

[0113] Step 4: Preparation of protective film layer: The protective film slurry is applied onto the saturated electrolyte using a dispensing process to form a coating structure. The thickness of the protective film layer is 20 μm. The protective film slurry consists of 18% PDMS, 2% curing agent, and 80% cyclohexane by mass percentage. The preparation process of the protective film slurry is as follows: The above-mentioned protective film slurry components are mixed to obtain the protective film slurry.

[0114] Example 2

[0115] This embodiment provides a miniature dry reference electrode, which differs from Embodiment 1 in that:

[0116] In step 3, the amount of sodium alginate added is 0.1g, the amount of D5 hydrogel added is 0.3g, the mass concentration of CaCl2 aqueous solution is 2%, and the thickness of the electrolyte layer is 50um.

[0117] Example 3

[0118] This embodiment provides a miniature dry reference electrode, which differs from Embodiment 1 in that:

[0119] In step 3, the amount of sodium alginate added is 0.3g, the amount of D5 hydrogel added is 0.1g, the mass concentration of CaCl2 aqueous solution is 4%, and the thickness of the electrolyte layer is 15um.

[0120] Example 4

[0121] This embodiment provides a miniature dry reference electrode, which differs from Embodiment 1 in that:

[0122] In step 1, the curing temperature is 100℃, the time is 20 minutes, and the thickness of the graphite conductive layer is 20um.

[0123] In step 2, the curing temperature is 100℃, the time is 15 minutes, and the Ag / AgCl silver paste layer thickness is 40um.

[0124] In step 4, the protective film slurry consists of 15% PDMS, 3% curing agent and 82% cyclohexane by mass percentage, and the thickness of the protective film is 5 μm.

[0125] Example 5

[0126] This embodiment provides a miniature dry reference electrode, which differs from Embodiment 1 in that:

[0127] In step 1, the curing temperature is 150℃, the time is 20 minutes, and the thickness of the graphite conductive layer is 50um.

[0128] In step 2, the curing temperature is 150℃, the curing time is 5 minutes, and the Ag / AgCl silver paste layer thickness is 10µm.

[0129] In step 4, the protective film slurry consists of 20% PDMS, 1% curing agent and 79% cyclohexane by mass percentage, and the thickness of the protective film is 60 μm.

[0130] Example 6

[0131] This embodiment provides a miniature dry reference electrode, which differs from Embodiment 1 in that:

[0132] In step 3, the amount of sodium alginate added is 0.05g, the amount of D5 hydrogel added is 0.35g, and the mass concentration of CaCl2 aqueous solution is 1.5%.

[0133] Example 7

[0134] This embodiment provides a miniature dry reference electrode, which differs from Embodiment 1 in that:

[0135] In step 3, the amount of sodium alginate added is 0.35g, the amount of D5 hydrogel added is 0.05g, and the mass concentration of CaCl2 aqueous solution is 4.5%.

[0136] Example 8

[0137] This embodiment provides a miniature dry reference electrode, which differs from Embodiment 1 in that:

[0138] In step 3, D5 hydrogel is not added.

[0139] Comparative Example 1

[0140] This comparative example provides a miniature dry reference electrode, which differs from Example 1 in that:

[0141] In step 3, the CaCl2 solution is not sprayed.

[0142] Comparative Example 2

[0143] This comparative example provides a commercial reference electrode, the CH111 reference electrode from Shanghai Chenhua Instrument Co., Ltd.

[0144] Test case

[0145] Test samples: The reference electrodes prepared in Examples 1-8, as well as the reference electrodes prepared in Comparative Example 1 and Comparative Example 2, were used as samples for testing.

[0146] Test method:

[0147] Test 1, Potential stability: A commercial reference electrode and a prepared test sample reference electrode were placed in the same test cell. The test solution was 100mM KCl. The open circuit potential between the two electrodes was measured, and the potential drift values ​​at 20 min and 10 min were calculated respectively.

[0148] Test 2, Resistance to chloride ion interference: Calibration solutions containing 102mM, 61.3mM and 137mM Cl ions were used to prepare reference electrode surfaces. The potential difference between the prepared reference electrode and the commercial reference electrode was tested using the open-circuit potential method, and the maximum drift of the reference electrode was calculated.

[0149] The test results are shown in Table 1.

[0150] Table 1

[0151]

[0152]

[0153] As shown in Table 1, regarding potential stability, the reference electrodes of Examples 1 to 8 all exhibited potential drift below 0.89 mV within 20 minutes, significantly better than Comparative Example 1 (1.96 mV) and Comparative Example 2 (1.76 mV). This demonstrates that the sodium alginate-Ca... 2+The cross-linking mechanism for constructing a dry electrolyte layer effectively improves the long-term electrochemical stability of the reference electrode. Example 1 exhibited the best performance, with a potential drift of only 0.29 mV within 20 minutes and only 0.12 mV within 10 minutes, indicating that its electrolyte layer had the most stable KCl release rate and the strongest Cl- activity maintenance ability. In contrast, Comparative Example 1, without calcium ion cross-linking treatment, could not form a stable three-dimensional hydrogel network, leading to rapid electrolyte loss; Comparative Example 2 used a traditional saturated electrolyte slurry, lacking a slow-release regulation mechanism, and was easily diluted rapidly after contact with the sample, resulting in large potential drift and poor stability.

[0154] Regarding resistance to chloride ion interference, compared to Comparative Examples 1-2, the reference electrodes of Examples 1 to 8 exhibited significantly better stability than the comparative examples under different Cl- concentrations (102 mM, 61.3 mM, and 137 mM). The potential changes in Comparative Example 1 (without CaCl2 solution) and Comparative Example 2 (using conventional saturated electrolyte slurry) were as high as 1.17 mV and 0.97 mV, respectively, indicating that the electrolyte layer lacking calcium ion cross-linking cannot form an effective diffusion barrier, allowing external ions to freely penetrate and making the reference electrode susceptible to interference from the sample Cl- concentration, thus losing its stable reference capability. Among them, Example 1 showed the smallest potential change, only 0.11 mV, indicating that its electrolyte layer could effectively shield the influence of external Cl- concentration fluctuations on the electrochemical equilibrium of the Ag / AgCl interface, maintaining a stable reference potential. The potential changes in Examples 2 to 5 ranged from 0.23 to 0.32 mV, slightly higher than in Example 1, but still much lower than the comparative example. This indicates that within a reasonable ratio range, the cross-linked structure formed by sodium alginate and D5 hydrogel still possesses good ion-selective barrier function. Examples 1 and 6-7 show that when the formulation deviates from the preferred parameter range of this invention, the anti-interference ability significantly decreases: the potential changes in Example 6 (too little sodium alginate, too much D5) and Example 7 (too much sodium alginate, too little D5) reached 0.49 mV and 0.53 mV, respectively, suggesting that the gel network structure is uneven or insufficiently dense, leading to easier penetration of external Cl- to the electrode interface and triggering a Nernst response. Example 8, without the addition of D5 hydrogel, showed further deterioration in anti-interference performance (0.44 mV), indicating that D5 hydrogel plays an important role in enhancing gel absorbency and structural integrity.

[0155] In summary, this invention achieves precise control over Cl- release behavior through a composite hydrogel structure formed by in-situ crosslinking of sodium alginate and calcium ions, significantly improving the potential stability and environmental adaptability of the micro dry reference electrode.

[0156] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a micro dry reference electrode, characterized in that, The method comprises the following steps: sequentially laminating a conductive layer, a silver paste layer and an electrolyte layer on a substrate; The electrolyte layer is prepared by the following steps: (a) applying an electrolyte paste on the silver paste layer to form a pre-prepared electrolyte layer; wherein the components of the electrolyte paste comprise potassium chloride and sodium alginate; (b) applying a solution containing calcium ions on the pre-prepared electrolyte layer to obtain the electrolyte layer.

2. The production method according to claim 1, characterized by, The components of the electrolyte paste comprise saturated potassium chloride solution and sodium alginate; Preferably, the electrolyte paste contains 34.7g KCl and 1-3g sodium alginate per 100g water; Preferably, the components of the electrolyte paste further comprise hydrogel; Preferably, the electrolyte paste contains 34.7g KCl, 1-3g sodium alginate and 1-3g hydrogel per 100g water.

3. The preparation method according to claim 1, characterized in that, The solution containing calcium ions comprises one or more of calcium chloride solution and / or calcium sulfate solution; Preferably, the mass concentration of the solution containing calcium ions is 2%-4%.

4. The method of claim 1, wherein, The thickness of the electrolyte layer is 15-50um.

5. The preparation method according to claim 1, characterized in that, The thickness of the conductive layer is 20-50um; Preferably, the preparation process of the conductive layer comprises: applying the preparation raw material of the conductive layer to the substrate, and then performing a first solidification treatment to obtain the conductive layer; Preferably, the preparation raw material of the conductive layer comprises one or more of carbon, gold and platinum; Preferably, the application method of the conductive layer paste comprises one or more of screen printing, chemical deposition, electroplating, vacuum sputtering and spray dispensing; Preferably, the temperature of the first solidification treatment is 100-150℃, and the time of the first solidification treatment is 10-20 minutes.

6. The method of claim 1, wherein, The thickness of the silver paste layer is 10-40um; Preferably, the preparation process of the silver paste layer comprises: applying a silver paste layer paste to the conductive layer, and then performing a second solidification treatment to obtain the silver paste layer; Preferably, the silver paste layer paste comprises Ag / AgCl paste; Preferably, the application method of the silver paste layer paste comprises spray dispensing and / or screen printing; Preferably, the temperature of the second solidification treatment is 100-150℃, and the time of the second solidification treatment is 5-15 minutes.

7. The production method according to claim 6, characterized by, The preparation method further comprises: preparing a protective film layer on the electrolyte layer; Preferably, the thickness of the protective film layer is 5-60um; Preferably, the preparation process of the protective film layer comprises: applying a protective film layer paste to the electrolyte layer to obtain the protective film layer; Preferably, the components of the protective film layer paste comprise: PDMS, a curing agent and cyclohexane; Preferably, the components of the protective film layer paste comprise: 15%-20% PDMS, 1%-3% curing agent and the balance of cyclohexane in terms of mass percentage.

8. The method of claim 1, wherein, The substrate comprises one or more of PCB substrate, ceramic substrate, PVC and flexible polyester substrate.

9. A micro dry-reference electrode characterized in that, The method is prepared by the preparation method of any one of claims 1-8.

10. The use of the micro dry reference electrode of claim 9 in the preparation of an electrochemical sensor.

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