Printing ink, preparation method thereof and gas sensor

Abstract

The invention provides printing ink, a preparation method thereof and a gas sensor, the printing ink comprises tin oxide and an alkali metal aluminosilicate molecular sieve, and the mass ratio of the tin oxide to the alkali metal aluminosilicate molecular sieve is (10-20): (1-2); the alkali metal aluminosilicate molecular sieve in the ink disclosed by the invention can absorb water vapor in the environment, enhance the moisture resistance of the ink and reduce the influence of humidity on a gas sensitive mechanism, and the alkali metal aluminosilicate molecular sieve enables a gas sensor to provide more accurate and more reliable readings by reducing interference caused by humidity to the greatest extent; therefore, the gas sensor can keep stable performance under various environmental conditions (including a high-humidity environment); the humidity interference on tin oxide is reduced, and the sensitivity of the gas sensor is improved; the service life of the sensor is prolonged, the effectiveness can be kept for a long time, the replacement frequency of the gas sensor is reduced, the maintenance cost is reduced, and the cost effectiveness of users is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas sensors, and in particular to ink and a preparation method thereof, and a gas sensor. Background Art

[0002] Gas sensors are essential in various industrial, environmental and health-related applications due to their ability to detect and monitor a wide range of gases; microelectromechanical system (MEMS) gas sensors are favored due to their small size, low power consumption and high sensitivity. Among MEMS gas sensors, tin oxide has become a widely recognized material due to its excellent performance. Tin oxide sensors work by detecting changes in resistance when exposed to different gases.

[0003] However, a significant challenge facing tin oxide gas sensors is their sensitivity to humidity. Since water vapor in the air can interfere with the gas sensing mechanism, resulting in inaccurate readings and reduced reliability, humidity affects the adsorption and desorption process of gas molecules on the sensor surface, which is critical for accurate gas detection.

[0004] Therefore, how to overcome the above-mentioned technical problems and defects becomes a problem that needs to be solved urgently. Summary of the invention

[0005] In view of the problem that tin oxide gas sensors have poor humidity sensitivity, the present invention provides an ink and a preparation method thereof, and a gas sensor.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows: A first aspect of the present invention provides an ink, which includes tin oxide and alkali metal aluminosilicate molecular sieve, wherein the mass ratio of the tin oxide to the alkali metal aluminosilicate molecular sieve is (10-20): (1-2).

[0007] Optionally, based on the total mass of the ink as 100%, the mass percentage of the tin oxide is 5%-10%, and the mass percentage of the alkali metal aluminosilicate molecular sieve is 1%-10%.

[0008] Optionally, the porosity of the alkali metal aluminosilicate molecular sieve is 3-5 nm, and / or the particle size of the tin oxide is 5-50 nm, and / or the particle size of the alkali metal aluminosilicate molecular sieve is 50-500 nm.

[0009] Optionally, the ink further comprises a solvent, and the solvent comprises one or more of ethanolamine, ethanol, and propionic acid.

[0010] A second aspect of the present invention provides a method for preparing an ink, comprising the following preparation process: Step S1: preparing tin oxide ink; Step S2: adding alkali metal aluminosilicate molecular sieve into tin oxide ink and stirring to form a uniform ink.

[0011] Optionally, in step S1, preparing tin oxide ink comprises the following steps: Step S101: mixing tin chloride dihydrate and ethanolamine evenly to obtain a tin oxide precursor sol; Step S102: Evenly mix the tin oxide precursor sol and propionic acid to obtain tin oxide ink.

[0012] Optionally, in step S101, the mass ratio of tin chloride dihydrate to ethanolamine is (1-1.1):(12-13.2), and the purity of ethanolamine is 95%-100%.

[0013] Optionally, “mixing tin chloride dihydrate and ethanolamine uniformly to obtain a tin oxide precursor sol” comprises the following steps: Tin chloride dihydrate and ethanolamine were mixed, ultrasonicated for 30 to 40 minutes, and the tin oxide precursor sol was stirred at 65-80° C. in an inert atmosphere.

[0014] A third aspect of the present invention provides a gas sensor, comprising a MEMS device and a coating disposed on the MEMS device, wherein the coating is prepared from the above-mentioned ink, or is prepared from the ink prepared by the above-mentioned ink preparation method.

[0015] Optionally, the method for preparing the coating from the ink includes: applying the ink to the surface of the MEMS device, and further sintering to obtain the coating, the ink sintering temperature is 400-500° C., and the sintering time is 9-10 hours.

[0016] The alkali metal aluminosilicate molecular sieve in the ink of the present application can absorb water vapor in the environment, enhance the moisture resistance of the ink, reduce the influence of humidity on the gas-sensitive mechanism, and minimize the interference caused by humidity through the alkali metal aluminosilicate molecular sieve, so that the gas sensor can provide more accurate and reliable readings; thereby, the gas sensor can maintain stable performance under various environmental conditions (including high humidity environments); secondly, it can reduce humidity interference with tin oxide, and the response of tin oxide to target gas molecules is clearer, so that the gas sensor can more accurately detect target gases with lower concentrations; improve the sensitivity of the gas sensor; at the same time, it can also enhance the ability to distinguish various gases, reduce false alarms and improve the overall detection capability, so that the gas sensor has better selectivity; at the same time, it can also extend the service life of the sensor: the alkali metal aluminosilicate molecular sieve protects tin oxide from long-term exposure to humid environments, extends the service life of the gas sensor, and can maintain its effectiveness for a long time, reduces the frequency of replacement of gas sensors, can reduce maintenance costs, and improve the cost-effectiveness of users. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 is a schematic diagram of the synthesis of tin oxide ink provided by one embodiment of the present invention; Figure 2 It is a schematic diagram of a method for preparing an alkali metal-doped aluminosilicate molecular sieve provided in one embodiment of the present invention; DETAILED DESCRIPTION In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0019] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the materials and reagents used are reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0020] In one embodiment, the first aspect of the present invention provides an ink, which includes tin oxide and alkali metal aluminosilicate molecular sieve, and the mass ratio of the tin oxide to the alkali metal aluminosilicate molecular sieve is (10-20): (1-2).

[0021] Specifically, the mass ratio of the tin oxide to the alkali metal aluminosilicate molecular sieve is any ratio of 20:1, 15:1, 20:1.5, 10:1, 15:2, 10:1.5 or 5:1, or a range consisting of any two ratios.

[0022] In a preferred embodiment, the mass ratio of the tin oxide to the alkali metal aluminosilicate molecular sieve is 10:1.5, which is equivalent to 15 mg of alkali metal aluminosilicate molecular sieve in 100 µL of tin oxide ink.

[0023] When the mass ratio of tin oxide to alkali metal aluminosilicate molecular sieve is between (10-20): (1-2), the ink of the present application has the effect of optimizing the gas sensitivity of the gas sensor, while also enabling the gas sensor to maintain a technical effect of sufficient humidity control. This balanced ratio is very suitable for gas sensing applications that require accuracy and environmental stability; when the mass ratio of tin oxide to alkali metal aluminosilicate molecular sieve is less than 5:1, although it has a technical effect of improving humidity control, it will reduce the gas sensitivity of the gas sensor. The higher the molecular sieve content, the better the hygroscopicity, making the sensor more resistant to high humidity environments, but at the cost of reducing the sensitivity to gas detection; when the mass ratio of tin oxide to the alkali metal aluminosilicate molecular sieve is greater than 20:1, although it has the effect of improving the gas sensitivity of the gas sensor, it will reduce the gas sensor's control of humidity. In this case, the gas sensor is more sensitive to gas in a dry environment, but under humid conditions, due to the lack of sufficient hygroscopic effect, inaccurate detection or performance drift may occur.

[0024] The alkali metal aluminosilicate molecular sieve in the ink of the present application can absorb water vapor in the environment, enhance the moisture resistance of the ink, and reduce the influence of humidity on the gas-sensitive mechanism. The alkali metal aluminosilicate molecular sieve minimizes the interference caused by humidity, so that the gas sensor can provide more accurate and reliable readings; thereby, the gas sensor can maintain stable performance under various environmental conditions (including high humidity environments).

[0025] Secondly, alkali metal aluminosilicate molecular sieves can absorb water vapor in the environment and reduce humidity interference on tin oxide, so that tin oxide responds more clearly to target gas molecules. As a result, gas sensors can more accurately detect target gases with lower concentrations and improve the sensitivity of gas sensors. At the same time, they can also enhance the ability to distinguish various gases, reduce false alarms and improve overall detection capabilities, making gas sensors more selective.

[0026] In addition, alkali metal aluminosilicate molecular sieves can protect tin oxide from long-term exposure to humid environments, extend the service life of gas sensors, maintain their effectiveness for a long time, reduce the frequency of gas sensor replacement, thereby reducing maintenance costs and improving cost-effectiveness for users.

[0027] In one embodiment, based on the total mass of the ink being 100%, the mass percentage of the tin oxide is 5%-10%.

[0028] Specifically, the mass percentage of the tin oxide is any point value of 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10%, or a range value consisting of any two point values; in a preferred embodiment, the mass percentage of the tin oxide is 6%-7%.

[0029] In one embodiment, based on the total mass of the ink being 100%, the mass percentage of the alkali metal aluminosilicate molecular sieve is 1%-10%.

[0030] Specifically, the mass percentage of the alkali metal aluminosilicate molecular sieve is any point value of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, or a range value consisting of any two point values; in a preferred embodiment, the mass percentage of the alkali metal aluminosilicate molecular sieve is 3%-7%.

[0031] In one embodiment, the porosity of the alkali metal aluminosilicate molecular sieve is 3-5 nm.

[0032] Specifically, the porosity of the alkali metal aluminosilicate molecular sieve is any point value among 3nm, 3.2nm, 3.4nm, 3.6nm, 3.8nm, 4nm, 4.2nm, 4.4nm, 4.6nm, 4.8nm or 5nm, or a range value consisting of any two point values; in a preferred embodiment, the porosity of the alkali metal aluminosilicate molecular sieve is 3.6nm-4.4nm.

[0033] When the porosity of the alkali metal aluminosilicate molecular sieve is 3nm-5nm, it has the technical effect of effectively adsorbing gas molecules while controlling humidity, thereby improving the sensitivity and stability of gas sensing.

[0034] When the porosity of the alkali metal aluminosilicate molecular sieve is less than 3nm, the gas adsorption capacity is limited, reducing the sensor's ability to detect smaller gas molecules and impairing its overall performance in gas sensing applications; when the porosity of the alkali metal aluminosilicate molecular sieve is greater than 5nm, it will excessively adsorb moisture, leading to potential interference with gas sensing accuracy and reducing the sensor's selectivity.

[0035] In one embodiment, the particle size of tin oxide is 5 nm to 50 nm, and / or the particle size of alkali metal aluminosilicate molecular sieve is 50 nm to 500 nm.

[0036] Specifically, the particle size of the tin oxide is any point value of 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm or 50nm, or a range of any two point values; in a preferred embodiment, the particle size of the tin oxide is 20nm-30nm. When the particle size of the tin oxide is 5nm-50nm, it is ensured that the tin oxide has appropriate dispersibility and surface area for interaction with gas, further improving the performance of the gas sensor.

[0037] Specifically, the particle size of the alkali metal aluminosilicate molecular sieve is any point value of 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm or 500nm, or a range value consisting of any two point values; in a preferred embodiment, the particle size of the alkali metal aluminosilicate molecular sieve is 200nm-300nm.

[0038] In one embodiment, the ink further comprises a solvent, and the solvent comprises one or more of ethanolamine, ethanol, and propionic acid. The above solvents have the advantage of less toxicity and can improve the safety of the synthesis process; at the same time, these solvents can dissolve tin oxide and facilitate the combination of alkali metal aluminum silicate molecular sieves, and can also ensure that the ink has suitable viscosity and stability for printing applications.

[0039] like Figure 1-Figure 2 As shown, in one embodiment, the second aspect of the present invention provides a method for preparing ink, comprising the following preparation process: Step S1: preparing tin oxide ink; Step S2: adding alkali metal aluminosilicate molecular sieve into tin oxide ink and stirring to form a uniform ink.

[0040] Specifically, in step S2, the alkali metal aluminosilicate molecular sieve is added to the tin oxide ink, and stirred for 2 hours with a magnetic stirrer to form a uniform mixed solution.

[0041] like Figure 1 As shown, in one embodiment, in step S1, preparing tin oxide ink includes the following steps: Step S101: mixing tin chloride dihydrate and ethanolamine evenly to obtain a tin oxide precursor sol; Step S102: Evenly mix the tin oxide precursor sol and propionic acid to obtain tin oxide ink.

[0042] Specifically, in step S101, using ethanolamine, a solvent with less toxicity, can improve the safety of the synthesis process; ethanolamine, as a bidentate ligand, helps to provide two lone pairs of electrons for the tin ion.

[0043] The reaction mechanism of tin chloride dihydrate and ethanolamine includes: (1) Hydrolysis of tin chloride dihydrate: Reaction: SnCl2·2H2O→Sn 2+ +2Cl - +2H2O Tin chloride dihydrate decomposes in solution to form Sn 2+ and Cl − ions, and free water molecules; (2) Protonation of ethanolamine: Reaction: HOCH2CH2NH2+H2O→HOCH2CH2NH3 + +OH - (3) Nucleophilic attack and intermediate complex formation: Reaction: Sn 2+ +4[HOCH2CH2NH3] + →[Sn(HOCH2CH2NH3 + )4] 2+ Tin(II) ion (Sn 2+ ) can coordinate with four ethanolammonium ions to form a complex; (4) Formation of tin dioxide: Reaction: [Sn(HOCH2CH2NH3 + )4] 2+ +4Cl - +2H2O→SnO2+4HOCH2CH2NH3Cl+4H + The complex undergoes hydrolysis and oxidation to form tin dioxide (SnO2) and release four ethanolammonium chlorides (HOCH2CH2NH3Cl).

[0044] Overall reaction: 4HOCH2CH2NH2+2(SnCl2·2H2O)→2SnO2+4HOCH2CH2NH3Cl+4H + Specifically, in step S102, propionic acid is slowly added to the tin oxide precursor sol through a syringe, and the dripping rate is controlled by a TJ1A single-channel syringe pump (Hebei Lange Pump Industry Co., Ltd.), and the stirring time is 2 hours, and the final brown tin oxide ink product is obtained. By dripping propionic acid into the tin oxide precursor sol, using propionic acid as a pH buffer can achieve precise control and improve consistency and repeatability. Replacing hazardous solvents with safer alternatives such as ethanolamine and propionic acid can reduce health risks.

[0045] The present application obtains a tin oxide precursor sol by uniformly mixing tin oxide and ethanolamine; and then uniformly mixing the tin oxide precursor sol with propionic acid to obtain tin oxide ink. The preparation method of the tin oxide ink of the present application is simple, efficient, and convenient for large-scale production.

[0046] In one embodiment, in step S101, the mass ratio of tin chloride dihydrate to ethanolamine is (1-1.1): (12-13.2).

[0047] Specifically, the mass ratio of tin chloride dihydrate to ethanolamine is any point value among 1:13.2, 1:12.6, 1:12, 1.1:12.6, 1.1:12, or a range value consisting of any two point values.

[0048] In a preferred embodiment, the mass ratio of tin chloride dihydrate to ethanolamine is 1:12.

[0049] When the mass ratio of tin chloride dihydrate to ethanolamine is between (1-1.1): (12-13.2), it optimizes the dissolution and complexation of tin chloride dihydrate, ensures smooth reaction kinetics, and provides a consistent and stable tin oxide precursor sol. This balance also helps the ink achieve optimal viscosity, surface tension, and flow properties, which is critical for achieving compatibility with MEMS printer inkjet systems. The ink will flow smoothly through the printer nozzle and deposit evenly on the MEMS device without clogging; when the mass ratio of tin chloride dihydrate to ethanolamine is less than 1:13.2, there will be an excess of ethanolamine, resulting in reduced viscosity and surface tension of the tin oxide precursor sol. While this may improve the flow of the ink through the printer nozzle, too low a viscosity may reduce the ink's ability to properly adhere to the MEMS substrate, resulting in poor deposition and weak layer formation. This may also cause excessive ink diffusion, thereby reducing the precision and accuracy of the printed structure; when the mass ratio of tin chloride dihydrate to ethanolamine is greater than 1.1:12, the tin chloride dihydrate may not be completely dissolved, resulting in an uneven solution, increasing the viscosity and surface tension of the tin oxide precursor sol, which has a negative impact on the flow of ink during printing. Higher viscosity may cause the printer nozzle to clog, and increased surface tension may prevent the ink from being evenly distributed on the MEMS surface, thereby reducing the printing quality. By balancing the mass ratio, it is possible to ensure that the ink maintains appropriate viscosity, surface tension, and flow properties, which is critical to achieving high-quality MEMS gas sensor printing.

[0050] In one embodiment, in step S101, the purity of ethanolamine is 95%-100%. Selecting ethanolamine with higher purity to react with tin chloride dihydrate can reduce impurities in the reaction process and improve the quality of tin oxide.

[0051] In one embodiment, in step S101, “mixing tin chloride dihydrate and ethanolamine uniformly to obtain a tin oxide precursor sol” includes the following steps: Tin chloride dihydrate and ethanolamine were mixed, ultrasonicated for 30 to 40 minutes, and the tin oxide precursor sol was stirred at 65-80° C. in an inert atmosphere.

[0052] Specifically, the tin oxide precursor sol is magnetically stirred at a stirring speed of 600 rpm for 2 hours. Finally, the tin oxide precursor sol presents a distinct light yellow color. In addition, the obtained tin oxide precursor sol is placed in a sealed container, not exposed to external moisture, and stored in a dry place at room temperature. Allowing the tin oxide precursor sol to stand for several months can improve the stability of the tin oxide precursor sol.

[0053] In one embodiment, in step S102, the volume ratio of the tin oxide precursor sol to propionic acid is (1-1.1):(3.8-4). Specifically, the volume ratio of the tin oxide precursor sol to propionic acid is any point value among 1:4, 1:3.9, 1:3.8, 1.1:4, 1.1:3.9 or 1.1:3.8, or a range value consisting of any two point values.

[0054] In a preferred embodiment, the volume ratio of the tin oxide precursor sol to propionic acid is 1:(3.8-3.9).

[0055] When the volume ratio of tin oxide precursor sol to propionic acid is between (1-1.1): (3.8-4), the consistency of particle size and morphology of tin oxide particles can be guaranteed. This ratio can achieve optimal reaction kinetics, ensuring uniform mixing of tin oxide precursor sol and propionic acid, thereby forming uniform and well-dispersed particles during the sol-gel process. This is critical to achieving consistent particle properties, which will directly affect gas sensing performance and the mechanical integrity of MEMS structures. When the volume ratio of tin oxide precursor sol to propionic acid is less than 1:4, particle agglomeration and inconsistent particle morphology will increase. Lower propionic acid content can lead to insufficient stability of the tin oxide sol, resulting in irregular particle size, which affects the repeatability of the sensing performance of MEMS devices and also leads to higher surface tension, making the ink less suitable for uniform printing during MEMS manufacturing; when the volume ratio of tin oxide precursor sol to propionic acid is greater than 1.1:3.8, the particle size is excessively reduced, which has a negative impact on the structural integrity of the tin oxide particles. Excessive propionic acid may also reduce the viscosity of the precursor ink, making it more difficult to control during the printing process, resulting in poor deposition and coverage on the MEMS substrate. By optimizing the volume ratio of tin oxide precursor sol to propionic acid, the formulation ensures uniform particle size distribution, stable ink performance, and high-quality MEMS printing for gas sensor applications.

[0056] In one embodiment, in step S2, the concentration of the mixed solution is 0.37-0.38 mol / L.

[0057] Specifically, the concentration of the mixed solution is any point value among 0.37mol / L, 0.371mol / L, 0.372mol / L, 0.373mol / L, 0.374mol / L, 0.375mol / L, 0.376mol / L, 0.377mol / L, 0.378mol / L, 0.379mol / L or 0.38mol / L, or a range value consisting of any two point values.

[0058] In a preferred embodiment, the concentration of the mixed solution is 0.376 mol / L.

[0059] When the concentration of the mixed solution is between 0.37-0.38 mol / L, the consistency of the particle size and morphology of the tin oxide particles can be guaranteed. At this concentration, the tin chloride dihydrate is fully dissolved, allowing uniform nucleation during the sol-gel process, resulting in uniform particle size and controllable morphology. This consistency is critical to the performance of the ink during the MEMS printing process, ensuring good fluidity, viscosity, and coverage; when the concentration of the mixed solution is less than 0.37 mol / L, larger or irregular tin oxide particles will be produced, resulting in a reduction in nucleation points, resulting in larger particles or particle agglomeration. This will have a negative impact on the performance of the printing process and MEMS devices, because the ink will exhibit higher viscosity and uneven deposition on the MEMS substrate; when the concentration of the mixed solution is greater than 0.38 mol / L, too small tin oxide particles will be produced, which will damage the mechanical strength of the particles and the stability of the ink, resulting in oversaturation, resulting in rapid nucleation and a more inconsistent particle size distribution. In addition, it may also reduce the viscosity of the ink, making it difficult to control during the printing process, resulting in layer uniformity and thickness issues.

[0060] In one embodiment, the third aspect of the present invention provides a gas sensor, including a MEMS device and a coating disposed on the MEMS device, wherein the coating is prepared from the above-mentioned ink, or is prepared from the ink prepared by the above-mentioned ink preparation method.

[0061] By printing the ink onto the MEMS substrate using standard printing technology, the alkali metal aluminosilicate molecular sieve is directly integrated into the sensing material, which simplifies the process, reduces production time and complexity, makes large-scale manufacturing more feasible, and improves manufacturing efficiency; moreover, the ink formulation of the present application can be easily adapted to different sensor designs and applications without major changes to the existing manufacturing infrastructure, and has strong compatibility.

[0062] The ink composition of the present application is suitable for various types of MEMS gas sensors, and this versatility makes it widely applicable to different industries, including environmental monitoring, industrial safety, healthcare and smart home systems. The adaptability of the ink composition of the present application to various gas sensor designs and environmental conditions makes it suitable for a wide range of applications and can be used in various fields such as environmental monitoring, industrial safety, healthcare and smart home systems.

[0063] In one embodiment, the method for preparing the coating from the ink includes: applying the ink to the surface of the MEMS device, and further sintering to obtain the coating.

[0064] Specifically, the ink is placed in a printer and printed on the surface of the MEMS device to print an ink coating on the surface of the MEMS device; the ink coating is then sintered in an oxygen-containing atmosphere to obtain powdered tin oxide containing an alkali metal aluminum silicate molecular sieve.

[0065] In one embodiment, the ink is sintered at a temperature of 400-500° C. and for a sintering time of 9-10 hours.

[0066] Specifically, the sintering temperature of the ink is any point value among 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C or 500°C, or a range value consisting of any two point values; in a preferred embodiment, the sintering temperature of the ink is 450°C.

[0067] Specifically, the ink sintering time is any point value among 9h, 9.1h, 9.2h, 9.3h, 9.4h, 9.5h, 9.6h, 9.7h, 9.8h, 9.9h or 10h, or a range value consisting of any two point values. In a preferred embodiment, the ink sintering time is 10h.

[0068] Sintering at 400-500℃ for 9-10 h produces high-quality tin oxide and alkali metal aluminosilicate molecular sieves. These conditions allow the tin oxide particles to be properly crystallized and stabilized, ensuring uniform particle size and morphology, which is critical for improving the performance of gas sensors; in addition, it ensures the best sintering state, resulting in well-shaped crystalline tin oxide, which contributes to the high sensitivity and stability of the final MEMS gas sensing device. When the temperature is lower than 400℃ or the time is less than 9 h, the sintering process may be insufficient, resulting in incomplete crystallization and poor bonding between tin oxide and molecular sieves, which will lead to reduced gas sensitivity and reduced structural integrity. When the temperature exceeds 500℃ or the time exceeds 10 h, the sintering process will lead to excessive crystallization or particle agglomeration, resulting in a reduction in surface area, which will degrade the performance of the molecular sieve and reduce its ability to control humidity.

[0069] By keeping the sintering temperature between 400-500°C and the sintering time between 9-10 h, the process can produce high-quality tin oxide particles with integrated molecular sieves, thereby optimizing the gas sensing performance and humidity control capabilities of MEMS devices.

[0070] The preparation method and application of the present invention will be further described in detail below in conjunction with specific examples. It should be understood that the following examples are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0071] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0072] Table 1: Ink compositions and some preparation parameters of Examples 1-3 and Comparative Examples 1-13 Example 1 An ink, comprising tin oxide and alkali metal aluminosilicate molecular sieve, wherein the mass ratio of the tin oxide to the alkali metal aluminosilicate molecular sieve is 6.67:1; A method for preparing ink, the specific steps of the method are as follows: (1) Preparation of tin oxide precursor sol 30 mL of pure ethanolamine was taken into a flask, and 2.55 g of tin chloride dihydrate was dissolved, and ultrasonic treatment was performed for 35 minutes to obtain a tin oxide precursor sol; then, the tin oxide precursor sol was magnetically stirred at 70°C and a stirring speed of 600 rpm for 2 hours in an inert atmosphere environment, and the obtained tin oxide precursor sol was placed in a sealed container and stored in a dry place at room temperature; (2) Preparation of tin oxide ink After the tin oxide precursor sol was cooled to room temperature, 3 mL of the tin oxide precursor sol was taken and 11.65 mL of concentrated propionic acid was slowly added through a syringe. The dripping rate was controlled by a TJ1A single-channel syringe pump and stirred for 2 h to obtain tin oxide ink. (3) Addition of alkali metal aluminosilicate molecular sieve Take 0.500 µL of tin oxide ink, add 15 mg of alkali metal aluminum silicate molecular sieve (nanoscale), stir with a magnetic stirrer for 2 hours to form a uniform mixture. Print this ink in a printer to print out ink for gas sensors.

[0073] (4) Sintering and application Printing and sintering: The prepared ink was printed using a MEMS-compatible printer, and the printed ink was then heated to 450°C and sintered in an oxygen-rich environment for 10 h to produce powdered nano-tin oxide integrated with the molecular sieve. The final ink was printed onto the surface of the MEMS device for gas sensing applications.

[0074] Example 2-3 Example 2-3 is used to illustrate an ink disclosed in the present invention, including most of the operating steps in Example 1, with the difference being that the tin oxide and alkali metal aluminum silicate molecular sieve content, the sintering temperature and sintering time of the ink used in Example 2-3 are as shown in Table 1.

[0075] Comparative Examples 1-13 Comparative Examples 1-13 are used to illustrate an ink disclosed in the present invention, including most of the operating steps in Example 1, except that the contents of tin oxide and alkali metal aluminum silicate molecular sieves, the sintering temperature and the sintering time of the ink used in Comparative Examples 1-13 are as shown in Table 1.

[0076] Performance Testing The ink prepared above was subjected to the following performance tests: Gas sensitivity test: The printed MEMS sensor, which contains tin oxide and molecular sieves, was prepared for testing by dispersing the sample in 200 μL of aqueous solution and evenly dispersing it in a heated chamber. A 10 μL aliquot was then applied to the designated sensing area of ​​the MEMS sensor, allowing the system to detect gas concentrations. After natural drying, it was loaded into the sensor test system for various gas sensing performance tests.

[0077] The total gas flow rate was controlled by a gas flow meter and maintained at a constant rate of 200 sccm (standard cubic centimeters per minute). The sensing tests were performed at room temperature to evaluate the performance of the sensor under ambient conditions.

[0078] Gas sensitivity (S) is calculated using the following formula: Where: R air is the resistance of the sensing material in air conditions, R gas is the resistance of the sensing material when exposed to the target gas.

[0079] The response time (T1) is the time required for the resistance to drop to 90% of the maximum difference after the sensing gas enters the chamber. The recovery time (T2) is the time required for the resistance to recover to 90% of the maximum difference after the target gas is turned off.

[0080] The performance test results are listed in Table 2; Table 2: Performance test results of Examples 1-3 and Comparative Examples 1-13 From the parameters in Table 1 and the test results in Table 2, we can see that: Comparison of Examples 1-3 with Comparative Example 5 shows that when alkali metal aluminosilicate molecular sieves are added to the ink, the humidity control of the gas sensor is significantly enhanced; Comparison between Examples 1-3 and Comparative Examples 6-7 shows that when the mass ratio of tin oxide to molecular sieve is maintained between (10-20): (1-2), the gas sensor has good gas sensitivity and can maintain adequate humidity control; when the mass ratio of tin oxide to molecular sieve is maintained between (6-7): 1, the gas sensor has excellent gas sensitivity and humidity control.

[0081] Comparison of Examples 1-3 with Comparative Examples 1-2 and Comparative Examples 8-9 shows that when the sintering temperature of the ink is 400-500°C, the particle size consistency of the ink is relatively high. When the sintering temperature of the ink is 450°C, the optimal sintering state can be ensured, thereby producing well-shaped crystalline tin oxide. When the sintering temperature of the ink is lower than 400°C or higher than 500°C, the gas sensitivity and particle size consistency of the gas sensor will be reduced.

[0082] Comparison of Examples 1-3 with Comparative Examples 3-4 and Comparative Examples 10-11 shows that when the ink sintering time is 9-10 hours, the particle size consistency of the ink is relatively high. When the ink sintering time is 10 hours, the optimal sintering state can be ensured, thereby producing well-shaped crystalline tin oxide. When the ink sintering time is less than 9 hours or more than 10 hours, the gas sensitivity and particle size consistency of the gas sensor will be reduced.

[0083] Comparison of Examples 1-3 with Comparative Examples 12-13 shows that when the sintering temperature of the ink is lower than 400°C or higher than 500°C, and the sintering time of the ink is lower than 9h or higher than 10h, the gas sensitivity and particle size consistency of the gas sensor are both low.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An ink, characterized in that: The ink comprises tin oxide and alkali metal aluminosilicate molecular sieve, and the mass ratio of the tin oxide to the alkali metal aluminosilicate molecular sieve is (10-20): (1-2).

2. The ink according to claim 1, characterized in that: Based on the total mass of the ink being 100%, the mass percentage of the tin oxide is 5%-10%, and the mass percentage of the alkali metal aluminosilicate molecular sieve is 1%-10%.

3. The ink according to claim 1, characterized in that: The porosity of the alkali metal aluminosilicate molecular sieve is 3-5 nm, and / or the particle size of the tin oxide is 5-50 nm, and / or the particle size of the alkali metal aluminosilicate molecular sieve is 50-500 nm.

4. The ink according to claim 1, characterized in that: The ink also includes a solvent, and the solvent includes one or more of ethanolamine, ethanol, and propionic acid.

5. The method for preparing the ink according to any one of claims 1 to 4, characterized in that: The preparation process includes the following: Step S1: preparing tin oxide ink; Step S2: adding alkali metal aluminosilicate molecular sieve into tin oxide ink and stirring to form a uniform ink.

6. The method for preparing ink according to claim 5, characterized in that: In step S1, preparing tin oxide ink comprises the following steps: Step S101: mixing tin chloride dihydrate and ethanolamine evenly to obtain a tin oxide precursor sol; Step S102: Evenly mix the tin oxide precursor sol and propionic acid to obtain tin oxide ink.

7. The method for preparing the ink according to claim 6, characterized in that: In step S101, the mass ratio of tin chloride dihydrate to ethanolamine is (1-1.1): (12-13.2), and the purity of ethanolamine is 95%-100%.

8. The method for preparing the ink according to claim 6, characterized in that: "Evenly mixing tin chloride dihydrate and ethanolamine to obtain a tin oxide precursor sol" comprises the following steps: Tin chloride dihydrate and ethanolamine were mixed, ultrasonicated for 30 to 40 minutes, and the tin oxide precursor sol was stirred at 65-80° C. in an inert atmosphere.

9. A gas sensor, characterized in that: The invention comprises a MEMS device and a coating arranged on the MEMS device, wherein the coating is prepared from the ink according to claims 1 to 4, or prepared from the ink prepared by the ink preparation method according to any one of claims 5 to 8.

10. The gas sensor according to claim 9, characterized in that: The method for preparing the coating from the ink comprises: applying the ink to the surface of the MEMS device, and further sintering to obtain the coating, the ink sintering temperature is 400-500° C., and the sintering time is 9-10 hours.

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