A kind of dissolved hydrogen sensor in water and preparation method thereof

Abstract

The invention discloses a water-dissolved hydrogen sensor and a preparation method thereof. The water-dissolved hydrogen sensor comprises a PI flexible substrate and two hydrogen-sensitive chips. The hydrogen-sensitive chips comprise a substrate, a plurality of hydrogen-sensitive resistor elements with the same electrochemical characteristics arranged on the substrate, and metal electrode bumps. The hydrogen-sensitive resistor elements of the two hydrogen-sensitive chips form a Wheatstone bridge structure. The PI flexible substrate is partially perforated, and the two hydrogen-sensitive chips are respectively flip-connected at the perforated and non-perforated portions of the PI flexible substrate, and the metal electrode bumps are connected to the PI flexible substrate. Sealant is sprayed on the backs and surroundings of the two hydrogen-sensitive chips, and a nano-alumina particle layer and a graphene layer are sprayed on the front and surroundings of the hydrogen-sensitive chip at the perforated portion of the PI flexible substrate in sequence, and the hydrogen-sensitive chip at the non-perforated portion of the PI flexible substrate is located in a closed chamber between the PI flexible substrate and the sealant. The water-dissolved hydrogen sensor of the invention has a simple structure, excellent hydrophobicity, good insulation, and can work stably in water for a long time.

Description

Technical Field

[0001] The invention belongs to the field of hydrogen sensors, and in particular relates to a sensor for dissolved hydrogen in water and a preparation method thereof. Background Art

[0002] Hydrogen is a major industrial raw material and the most important industrial gas and specialty gas. It is widely used in petrochemical, metallurgical, semiconductor and power industries.

[0003] Compared with conventional gases, hydrogen has many properties that are not conducive to safety. Hydrogen has a wider explosion range of 4% to 75% vol in the air, lower ignition energy (0.019mJ), is more likely to leak, has a higher flame propagation speed, etc. Therefore, the use of hydrogen sensors to monitor hydrogen concentration and leakage in hydrogen use environments has been very widespread. However, in some special industrial fields, the detection of hydrogen is not entirely in the form of gas, but also in the form of hydrogen dissolved in transformer oil and hydrogen dissolved in water. Because transformer oil has certain electrical insulation properties, it is feasible to directly measure the concentration of dissolved hydrogen in oil with palladium alloy thin film resistors, and it has been widely used in the power industry in recent years. However, water has weak conductivity, and conventional hydrogen sensors cannot be directly inserted into water to directly measure the hydrogen concentration.

[0004] The high hydrogen content in cooling water of large generators will cause aging of the insulation materials of the generators, seriously affecting the insulation performance, and easily causing short circuits or even power failures of the machines. In addition, the hydrogen-containing gas overflowing and accumulating in the cooling water with high hydrogen content is easy to produce corona discharge inside the machine, causing motor failure and even burning of the motor. Hydrogen-containing gas also has an adverse effect on the mechanical strength and conductivity of the contact points, which can easily cause arc burns and aggravate equipment failures. Therefore, the generator has very high requirements for the detection and trend monitoring of the dissolved hydrogen concentration in its cooling water, and the industry currently adopts the method of regular water sampling and offline laboratory testing. This detection method takes a long time, has many steps, and cannot achieve real-time continuous monitoring, so there are certain shortcomings in measurement accuracy and timeliness. In addition, because the solubility of hydrogen in water is very low, there are also high requirements for the sensitivity and measurement accuracy of the detection technology.

[0005] Patent application CN116380986A proposes a device for measuring dissolved hydrogen and resistivity in pure water, which uses a palladium alloy hydrogen sensor to directly detect the concentration of dissolved hydrogen in water. The sensor chip integrates a heater and a temperature sensor. There is no device for isolating pure water on the surface of the hydrogen sensor chip, and the hydrogen-sensitive resistor and heater of the chip have a large current. Water is a conductive medium. When the sensor chip works in pure water for a long time, its poor electrical insulation performance will cause damage to the sensor. The patent application does not elaborate on its insulation protection method for solving the problem of hydrogen sensor chip working in water.

[0006] Patent application CN102037349A proposes to use the deposition technology of "molecular stacking" to prepare a composite coating of polytetrafluoroethylene and aluminum oxide on the surface of a solid-state sensor, and utilizes the hydrophobicity of polytetrafluoroethylene and the oxygen inhibition performance of aluminum oxide to enable the sensor to achieve water / oxygen molecule penetration. The thickness of polytetrafluoroethylene prepared by deposition technology such as "molecular stacking" is limited, and polytetrafluoroethylene is not super hydrophobic, so it can only be used as a short-term isolation of water vapor. If it is immersed in water or water vapor for a long time, water can still partially or completely penetrate, causing the sensor to work abnormally or even damaged. Summary of the invention

[0007] The present invention aims to address the deficiencies in the prior art and provide a dissolved hydrogen sensor in water and a method for preparing the same, thereby overcoming the problem that the hydrogen sensor is prone to work abnormally when measuring the concentration of dissolved hydrogen in water and improving the sensitivity and measurement accuracy of the hydrogen sensor.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A dissolved hydrogen sensor in water, comprising a PI flexible substrate and two hydrogen-sensitive chips, wherein the hydrogen-sensitive chips comprise a substrate, a plurality of hydrogen-sensitive resistor elements with the same electrochemical properties arranged on the substrate, and metal electrode bumps, wherein the hydrogen-sensitive resistor elements of the two hydrogen-sensitive chips form a Wheatstone bridge structure;

[0010] The PI flexible substrate is partially opened, the two hydrogen-sensitive chips are flip-chip connected at the opening and non-opening of the PI flexible substrate respectively, and the metal electrode bumps are connected to the PI flexible substrate;

[0011] The backs of the two hydrogen-sensitive chips and their surroundings are sprayed with sealant, and the front of the hydrogen-sensitive chip at the opening of the PI flexible substrate and its surroundings are sprayed with a nano-aluminum oxide particle layer and a graphene layer in sequence;

[0012] The hydrogen-sensitive chip at the unopened portion of the PI flexible substrate is located in a closed chamber between the PI flexible substrate and the sealant.

[0013] In order to ensure that the hydrogen-sensitive chip in a hydrogen environment has good electrical insulation performance after long-term water immersion, sealant is sprayed on the back and surrounding of the hydrogen-sensitive chip at the opening of the PI flexible substrate, so that the edge of the back of the hydrogen-sensitive chip is tightly combined with the PI flexible substrate to prevent water vapor from penetrating from the edge; the front of the hydrogen-sensitive chip is sprayed with a nano-alumina particle layer and a graphene layer, which can achieve electrical isolation of the medium water, while hydrogen molecules and hydrogen atoms can pass through. The hydrogen-sensitive resistor element produces a resistance change after contacting with hydrogen, thereby realizing the measurement of the concentration of dissolved hydrogen in water. By flipping another hydrogen-sensitive chip and spraying sealant to form a closed chamber, the hydrogen-sensitive resistor element is physically isolated from hydrogen, and no resistance change occurs after contacting with hydrogen.

[0014] The dissolved hydrogen sensor in water of the present invention has a simple structure, excellent hydrophobicity, good insulation, can work stably for a long time in the water of the medium, and has high sensor sensitivity and measurement accuracy.

[0015] Furthermore, the thickness of the nano-alumina particle layer is 0.2um to 2um. Preferably, the thickness of the nano-alumina particle layer is 0.5um to 1um.

[0016] Furthermore, the thickness of the graphene layer is 0.2 um to 5 um. Preferably, the thickness of the graphene layer is 1 um to 3 um.

[0017] Preferably, the graphene layer comprises graphene powder and anhydrous ethanol, and the mass ratio of the graphene powder to the anhydrous ethanol is 1:1.

[0018] Furthermore, the substrate is a silicon oxide wafer.

[0019] Furthermore, the hydrogen-sensitive resistor element is made of palladium-chromium alloy, palladium-gold alloy or palladium-nickel alloy.

[0020] Furthermore, the thickness of the hydrogen sensitive resistor element is 50nm to 500nm. Preferably, the thickness of the hydrogen sensitive resistor element is 100nm to 300nm.

[0021] Furthermore, the thickness of the metal electrode bump is 500nm to 2000nm. Preferably, the thickness of the metal electrode bump is 1000nm to 1500nm.

[0022] Based on the same inventive concept, the present invention also provides a method for preparing a dissolved hydrogen sensor in water, which comprises the following steps:

[0023] S1: Make hydrogen sensitive chip;

[0024] S2: Flip-chip connection is performed between a pre-processed PI flexible substrate and two hydrogen-sensitive chips, wherein one hydrogen-sensitive chip is located at the opening of the PI flexible substrate, and the other hydrogen-sensitive chip is located at the non-opening of the PI flexible substrate; the hydrogen-sensitive resistor elements of the two hydrogen-sensitive chips form a Wheatstone bridge structure;

[0025] S3: Spray sealant on the back of the two hydrogen-sensitive chips and around them;

[0026] S4: spraying a nano-aluminum oxide particle layer and a graphene layer on the front side and around the hydrogen-sensitive chip at the opening of the PI flexible substrate in sequence;

[0027] S5: Prepare a dissolved hydrogen sensor in water.

[0028] The water-dissolved hydrogen sensor of the present invention can be used for detecting the concentration of dissolved hydrogen in water and monitoring hydrogen leakage, etc. The measurable range of hydrogen concentration is from 2ppm to 20000ppm (volume fraction).

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) The hydrogen sensor of the present invention has a simple structure. The hydrogen-sensitive resistor element forms a Wheatstone bridge structure, and does not require a heating element or a temperature measuring element. The sensor has a small operating current and low power consumption, and is conducive to long-term operation in water, a weakly conductive medium.

[0031] 2) The present invention uses a flip-chip connection method to package the hydrogen-sensitive chip, and applies a sealant. Compared with ordinary metal lead packaging, the present invention eliminates the phenomenon of short circuit or poor insulation performance of exposed metal leads and metal pads in weakly conductive medium water, and can ensure normal operation under long-term immersion in weakly conductive media.

[0032] 3) The present invention adopts a super hydrophobic coating composed of nano-aluminum oxide particles and a graphene coating, which has excellent hydrophobic properties and enables the sensor to work directly immersed in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the cross-sectional structure of the dissolved hydrogen sensor in water of the present invention;

[0034] Figure 2 This is a schematic diagram of the packaging of the dissolved hydrogen sensor in water of the present invention;

[0035] Figure 3 is a schematic diagram of the hydrogen-sensitive chip of the present invention;

[0036] Figure 4 is a schematic diagram of a PI flexible substrate of the present invention;

[0037] Figure 5This is a test result diagram of the dissolved hydrogen concentration in water measured by the dissolved hydrogen sensor of the present invention.

[0038] In the figure: 1-hydrogen sensitive chip, 11-hydrogen sensitive resistor element, 12-metal electrode bump, 13-substrate, 2-PI flexible substrate, 21-PI flexible substrate opening, 3-nano alumina particle layer, 4-graphene layer, 5-sealant. DETAILED DESCRIPTION

[0039] The present invention will be described in detail below in conjunction with the embodiments. It should be noted that the embodiments and features of the embodiments of the present invention can be combined with each other without conflict. For the convenience of description, if the words "upper", "lower", "left" and "right" appear in the following, they only indicate that the upper, lower, left and right directions are consistent with the drawings themselves, and do not limit the structure.

[0040] Example 1

[0041] like Figure 1-Figure 4 The dissolved hydrogen sensor in water of this embodiment is composed of two identical hydrogen-sensitive chips 1 and a partially open electrically connected PI (polyimide) flexible substrate 2; the hydrogen-sensitive chip 1 includes a substrate 13, two palladium alloy thin film hydrogen-sensitive resistor elements 11 with the same geometric dimensions and electrochemical properties, and a metal electrode bump 12; the hydrogen-sensitive chip 1 and the PI flexible substrate 2 are electrically connected by flip-chip welding, and the metal electrode bump 12 is connected to the PI flexible substrate 2; the four hydrogen-sensitive resistor elements 11 in the two hydrogen-sensitive chips 1 form a Wheatstone bridge structure. The Wheatstone bridge structure is composed of two hydrogen-sensitive resistor elements 11 located at the opening 21 of the PI flexible substrate and two hydrogen-sensitive resistor elements 11 isolated by a hydrogen-free environment. The hydrogen-sensitive resistor element 11 isolated by a hydrogen-free environment is located in a micron-thick cavity between the sealant 5 and the PI flexible substrate 2 (in a hydrogen-free environment, after the hydrogen-sensitive chip 1 and the PI flexible substrate 2 are flip-chip welded, a layer of sealant 5 is sprayed on the back and around the hydrogen-sensitive chip 1, and a closed chamber is formed after completion), so that it is physically isolated from hydrogen.

[0042] In order to ensure the electrical insulation performance of the electrodes between the two hydrogen-sensitive resistor elements 11 in the hydrogen-sensitive chip 1 after long-term water blistering, a layer of sealant 5 is sprayed on the back and surrounding of the hydrogen-sensitive chip 1 flip-chip soldered at the opening 21 of the PI flexible substrate, so that the back edge of the hydrogen-sensitive chip 1 is tightly combined with the PI flexible substrate 2 to prevent water vapor from penetrating from the edge. A super-hydrophobic layer composed of a nano-aluminum oxide layer 3 and a graphene layer 4 is sprayed on the front and surrounding of the hydrogen-sensitive chip 1 located in the opening 21 of the PI flexible substrate.

[0043] The PI flexible substrate 2 is pre-processed with openings and electrode bumps, and the metal electrode bumps 12 are connected to the electrode bumps on the PI flexible substrate 2.

[0044] The substrate 13 is a silicon oxide wafer, and the hydrogen sensitive resistor material is preferably a metal material having a catalytic effect on hydrogen, preferably palladium-chromium, palladium-gold, or palladium-nickel alloy.

[0045] The two hydrogen-sensitive resistor elements in the Wheatstone bridge structure produce resistance changes when in contact with hydrogen, thereby achieving the purpose of detecting hydrogen; the other two hydrogen-sensitive resistor elements in the Wheatstone bridge structure are physically isolated from hydrogen through a closed chamber, and will not produce resistance changes when in contact with hydrogen.

[0046] The super-hydrophobic layer on the surface of the hydrogen-sensitive resistor element is preferably made of nano-aluminum oxide particles and graphene materials with excellent hydrophobic properties. In order to improve the insulation and water-proof properties of the sensor chip, in this embodiment, nano-aluminum oxide particles and graphene are sprayed on the surface of the hydrogen-sensitive chip located at the opening of the PI flexible substrate to form a super-hydrophobic composite coating. The graphene material is a new type of carbon-based two-dimensional material with very excellent super-hydrophobic properties. The hydrophobic properties of the composite coating are significantly improved compared to the hydrophobic layers of other materials.

[0047] This embodiment uses the design concept of Wheatstone bridge, without the need for a temperature control unit, so that the operating current of the sensor chip is very small, and the minimum can be controlled at 1mA, which is conducive to working in the medium water. The sensor chip does not need to be heated, and the medium temperature is the chip operating temperature.

[0048] This embodiment uses flip-chip welding to package the hydrogen-sensitive chip, and applies sealant. Compared with ordinary metal lead packaging, it eliminates the phenomenon of short circuit or poor insulation performance of exposed metal leads and metal pads in weakly conductive medium water, and can ensure normal operation under long-term immersion in weakly conductive media.

[0049] The thin film hydrogen sensor of this embodiment can be used to detect the concentration of dissolved hydrogen in water. The measurable range of hydrogen concentration is from 2ppm to 20000ppm (volume fraction).

[0050] Example 2

[0051] A method for preparing a dissolved hydrogen sensor in water comprises the following steps:

[0052] (1) Preparing a hydrogen-sensitive resistor element for hydrogen measurement on the upper surface of a silicon oxide substrate;

[0053] (2) Making metal electrode bumps on the hydrogen-sensitive resistor element and slicing to obtain a hydrogen-sensitive chip;

[0054] (3) A PI flexible substrate with pre-processed openings and metal electrode bumps and two hydrogen-sensitive chips are flip-chip soldered, wherein one hydrogen-sensitive chip is located at the opening position of the PI flexible substrate;

[0055] (4) Spray a layer of sealant on the back and around the two hydrogen-sensitive chips, so that the hydrogen-sensitive chips that are not located at the opening position of the PI flexible substrate form a closed chamber;

[0056] (5) mixing graphene powder and anhydrous ethanol in a mass ratio of 1:1, and preparing a graphene dispersion after ultrasonic treatment;

[0057] (6) spraying a layer of nano-aluminum oxide particles on the front side of the hydrogen-sensitive chip at the opening position of the PI flexible substrate, and then spraying a graphene dispersion on the surface of the nano-aluminum oxide particle coating to obtain a graphene layer to constitute the super-hydrophobic layer.

[0058] Among them, step (1) is to prepare the graphic structure of the hydrogen-sensitive resistor element on the substrate by photolithography technology, deposit the palladium-chromium alloy hydrogen-sensitive film by thermal evaporation, sputtering and other technologies, and obtain the hydrogen-sensitive resistor element by stripping and cleaning.

[0059] Step (2) is to prepare a metal electrode bump pattern structure on a substrate by photolithography technology, and deposit a Ti-Au film by thermal evaporation, sputtering and other technologies, wherein Ti serves as a transition layer to improve the adhesion of the Au layer, and the metal electrode bump can be obtained by stripping and cleaning.

[0060] Step (3) is to perform flip-chip welding on a PI flexible substrate with pre-processed openings and electrode bumps and two hydrogen-sensitive chips, so that the four hydrogen-sensitive resistor elements in the two hydrogen-sensitive chips form a Wheatstone bridge structure. After step (4) of spraying the sealant, the two hydrogen-sensitive resistor elements in the Wheatstone bridge structure are physically isolated from hydrogen through a closed chamber, so they are not sensitive to hydrogen.

[0061] Step (6) is to spray nano-alumina particles and graphene dispersion on two hydrogen-sensitive resistor elements at the opening position of the PI flexible substrate to obtain a super-hydrophobic layer. The hydrogen-sensitive resistor element can be completely immersed in water to work, and hydrogen molecules and hydrogen atoms in the water can penetrate through the composite coating and reach the surface of the hydrogen-sensitive resistor element.

[0062] Example 3

[0063] A method for preparing a dissolved hydrogen sensor in water comprises the following steps:

[0064] (1) Cleaning the silicon oxide substrate to remove oil stains and impurities from the polished surface of the substrate;

[0065] (2) preparing a hydrogen sensitive resistor element pattern on the substrate surface by photolithography to form a photoresist mask;

[0066] (3) using sputtering deposition technology or thermal evaporation process to deposit a palladium-chromium alloy film with a film thickness of 200 nm, and then stripping and cleaning the hydrogen-sensitive resistor element;

[0067] (4) fabricating a metal electrode bump photoresist mask pattern by photolithography;

[0068] (5) Using thermal evaporation process, first deposit a Ti film as a transition layer with a thickness of 50 nm; then deposit an Au film as an electrode bump with a thickness of 1000 nm;

[0069] (6) forming a hydrogen-sensitive chip by dicing;

[0070] (7) Using a PI flexible substrate with pre-processed vias and two hydrogen-sensitive chips for flip-chip bonding to form an electrical connection;

[0071] (8) Spray sealant on the back and around the two hydrogen-sensitive chips so that the two hydrogen-sensitive resistor elements in one of the hydrogen-sensitive chips are in a closed chamber;

[0072] (9) Using ultrasonic spraying equipment, spray a layer of nano-aluminum oxide particles with a thickness of 1 μm on the front of the hydrogen-sensitive chip located at the opening position of the PI flexible substrate;

[0073] (10) Graphene powder and anhydrous ethanol are mixed in a mass ratio of 1:1, and a graphene dispersion is prepared after ultrasonic treatment; a layer of graphene dispersion is further sprayed on the surface of the nano-alumina particles using an ultrasonic spraying device, and a graphene layer with a thickness of 1.5 μm is obtained after drying.

[0074] Example 4

[0075] A method for preparing a dissolved hydrogen sensor in water comprises the following steps:

[0076] (1) Cleaning the silicon oxide substrate to remove oil stains and impurities from the polished surface of the substrate;

[0077] (2) preparing a hydrogen sensitive resistor element pattern on the substrate surface by photolithography to form a photoresist mask;

[0078] (3) using sputtering deposition technology or thermal evaporation process to deposit a palladium-chromium alloy film with a film thickness of 300 nm, and then stripping and cleaning the hydrogen-sensitive resistor element;

[0079] (4) fabricating a metal electrode bump photoresist mask pattern by photolithography;

[0080] (5) Using thermal evaporation process, first deposit a Ti film as a transition layer with a thickness of 100 nm; then deposit an Au film as an electrode bump with a thickness of 1500 nm;

[0081] (6) forming a hydrogen-sensitive chip by dicing;

[0082] (7) Using a PI flexible substrate with pre-processed vias and two hydrogen-sensitive chips for flip-chip bonding to form an electrical connection;

[0083] (8) Spray sealant on the back and around the two hydrogen-sensitive chips so that the two hydrogen-sensitive resistor elements in one of the hydrogen-sensitive chips are in a closed chamber;

[0084] (9) Using ultrasonic spraying equipment, spray a layer of nano-aluminum oxide particles with a thickness of 2 μm on the front of the hydrogen-sensitive chip located at the opening position of the PI flexible substrate;

[0085] (10) Graphene powder and anhydrous ethanol are mixed in a mass ratio of 1:1, and a graphene dispersion is prepared after ultrasonic treatment; a layer of graphene dispersion is further sprayed on the surface of the nano-alumina particles using an ultrasonic spraying device, and a graphene layer with a thickness of 3 μm is obtained after drying.

[0086] Example 5

[0087] The dissolved hydrogen sensor in water is directly inserted into water with different hydrogen concentrations for continuous measurement. The sensor can effectively characterize the dissolved hydrogen in water with different concentrations and has a high sensitivity. The test results are as follows: Figure 5 From the test results, it can be seen that the greater the concentration of dissolved hydrogen in water, the greater the sensor output, and the test results of two tests at the same concentration are consistent, indicating that the sensor has excellent repeatability and stability.

[0088] The contents explained in the above embodiments should be understood as these embodiments are only used to more clearly illustrate the present invention, and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

Claims

1. A dissolved hydrogen sensor in water, characterized in that: It comprises a PI flexible substrate (2) and two hydrogen-sensitive chips (1), wherein the hydrogen-sensitive chip (1) comprises a substrate (13), a plurality of hydrogen-sensitive resistor elements (11) having the same electrochemical characteristics and arranged on the substrate (13), and metal electrode bumps (12), wherein the hydrogen-sensitive resistor elements (11) of the two hydrogen-sensitive chips (1) form a Wheatstone bridge structure; The PI flexible substrate (2) is partially perforated, the two hydrogen-sensitive chips (1) are flip-chip connected at the perforated portion (21) and the non-perforated portion of the PI flexible substrate, respectively, and the metal electrode bumps (12) are connected to the PI flexible substrate (2); A sealant (5) is sprayed on the backs of the two hydrogen-sensitive chips (1) and their surroundings, and a nano-aluminum oxide particle layer (3) and a graphene layer (4) are sprayed on the fronts of the hydrogen-sensitive chips at the openings (21) of the PI flexible substrate and their surroundings in sequence; The hydrogen-sensitive chip (1) at the portion of the PI flexible substrate (2) where no hole is opened is located in a sealed chamber between the PI flexible substrate (2) and the sealant (5).

2. The dissolved hydrogen sensor in water according to claim 1, characterized in that: The thickness of the nano-alumina particle layer (3) is 0.2 um to 2 um.

3. The dissolved hydrogen sensor in water according to claim 2, characterized in that: The thickness of the nano-alumina particle layer (3) is 0.5 um to 1 um.

4. The dissolved hydrogen sensor in water according to claim 1, characterized in that: The thickness of the graphene layer (4) is 0.2 um to 5 um.

5. The dissolved hydrogen sensor in water according to claim 4, characterized in that: The thickness of the graphene layer (4) is 1 um to 3 um.

6. The dissolved hydrogen sensor in water according to claim 1, characterized in that: The graphene layer (4) comprises graphene powder and anhydrous ethanol, and the mass ratio of the graphene powder to the anhydrous ethanol is 1:

1.

7. The dissolved hydrogen sensor in water according to claim 1, characterized in that: The hydrogen-sensitive resistor element (11) is made of palladium-chromium alloy, palladium-gold alloy or palladium-nickel alloy.

8. The method for preparing a dissolved hydrogen sensor in water according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: making a hydrogen-sensitive chip (1); S2: Flip-chip connection is performed between a pre-processed PI flexible substrate (2) and two hydrogen-sensitive chips (1), wherein one hydrogen-sensitive chip is located at a hole (21) of the PI flexible substrate, and the other hydrogen-sensitive chip is located at a non-hole of the PI flexible substrate; the hydrogen-sensitive resistor elements (11) of the two hydrogen-sensitive chips form a Wheatstone bridge structure; S3: Spraying sealant (5) on the back of the two hydrogen-sensitive chips and around them; S4: spraying a nano-aluminum oxide particle layer (3) and a graphene layer (4) in sequence on the front side of the hydrogen-sensitive chip at the opening (21) of the PI flexible substrate and its surroundings; S5: Prepare a dissolved hydrogen sensor in water.

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