Miniature humidity sensor based on two-dimensional material and preparation method and application thereof

Abstract

The invention discloses a miniature humidity sensor based on a two-dimensional material and a preparation method and application thereof, and belongs to the technical field of sensors. The micro humidity sensor based on the two-dimensional material comprises a two-dimensional material-based Cu-CuOx-PEDOT electrode assembly, a telescopic metal wire, a needle cap and a detection device which are mounted in a microneedle, the telescopic metal wire penetrates through the interior of the microneedle, the needle cap is located at the tip end of the microneedle and connected to the telescopic metal wire, and the detection device is connected with the two-dimensional material-based Cu-CuOx-PEDOT electrode assembly. The invention further discloses a preparation method and application of the miniature humidity sensor based on the two-dimensional material. The miniature humidity sensor can solve the problems that an existing miniature humidity sensor is poor in stability and sensitivity and complex in sensor integration.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to a micro humidity sensor based on two-dimensional materials, and a preparation method and application thereof. Background Art

[0002] Humidity sensing technology plays a vital role in agricultural irrigation management, biological science research, and a wide range of environmental monitoring activities. It can provide critical moisture data to help researchers and practitioners precisely control environmental conditions, optimize resource utilization, and promote ecological balance. However, although traditional humidity sensors perform well in many application scenarios, their inherent limitations limit their application potential in specific environments. One of the main drawbacks of traditional humidity sensors is their size and design inadaptability. These sensors are often large and difficult to embed into fragile or confined spaces such as inside plant stems or around tiny biological samples. This physical mismatch not only limits the accuracy of monitoring, but may also cause unnecessary interference or damage to the monitored objects, thereby affecting the accuracy and reliability of the data.

[0003] The micro humidity sensor derived from this can be used for humidity measurement in micro-nano space. However, existing micro humidity sensors, especially microneedle humidity sensors, also face many challenges in the process of preparation and application. Material stability is one of the major problems. The sensing material or membrane used at the tip of the microneedle needs to have good humidity responsiveness, and it is also necessary to maintain structural integrity and stable performance during long-term use. Existing materials often find it difficult to meet these requirements at the same time, resulting in sensor performance degradation or even failure after a period of use. In terms of sensitivity, although microneedle sensors have the potential advantage of high sensitivity due to their tiny size, in actual operation, this advantage is often not fully utilized due to deficiencies in material selection, structural design or manufacturing process, resulting in the sensor responding slowly when detecting small humidity changes and failing to meet the needs of high-precision monitoring. The complexity of sensor integration is also a major challenge facing existing micro humidity sensors. Effectively integrating microneedle sensors with other monitoring devices or systems to achieve real-time data transmission, processing and analysis requires solving a series of technical problems, including but not limited to the stability of signal transmission, the accuracy of data processing, and the reliability and durability of the system as a whole.

[0004] The defects of traditional humidity sensors and existing micro humidity sensors in terms of material stability, sensitivity and complexity of sensor integration have seriously restricted their wide application in the fields of agriculture, biology and environmental monitoring. Therefore, developing new humidity sensor technology to overcome these defects and improve the comprehensive performance of sensors is an important issue to be solved in the current humidity sensing field. Summary of the invention

[0005] The purpose of the present invention is to provide a micro humidity sensor based on two-dimensional materials and a preparation method and application thereof, so as to solve the problems of poor stability and sensitivity of the micro humidity sensor and complex sensor integration.

[0006] The technical solution adopted to achieve the above purpose is to provide a micro humidity sensor based on two-dimensional materials, including a two-dimensional material-based Cu-CuO installed in a microneedle. x -PEDOT electrode assembly, retractable metal wire, needle cap and detection device; the retractable metal wire runs through the inside of the microneedle, the needle cap is located at the tip of the microneedle and connected to the retractable metal wire, and the detection device is connected to the two-dimensional material-based Cu-CuO x -PEDOT electrode assembly.

[0007] The beneficial effects of the above technical solution of the present invention are as follows: x The microfilaments are integrated with poly (3,4-ethylenedioxythiophene) (PEDOT) to form a microcapacitive sensor that is not easily swollen and degraded due to water absorption, and has good mechanical integrity and long-term stability during use. The micro humidity sensor of the present invention allows highly sensitive and stable humidity detection while avoiding the limitations of liquid sensors. In addition, the two-dimensional material-based Cu-CuO x -PEDOT electrode assembly is encapsulated in a microneedle structure, which can be sealed or exposed to the environment as needed. The retractable metal wire drives the needle cap to open or close the microneedle tip, ensuring accurate measurement of humidity in confined spaces, making it an ideal solution for applications with limited access or when precise control of environmental conditions is required. Compared with existing technologies, this microsensor design improves sensitivity, stability and reliability due to the solid-state nature of the sensor, avoiding problems such as leakage, evaporation or degradation common in liquid-based systems.

[0008] Preferably, the material of the microneedle is glass or ceramic; the material of the needle cap is ethyl 2-cyanoacrylate.

[0009] The present invention also provides a method for preparing the micro humidity sensor, comprising the following steps:

[0010] S1, take two copper wires, clean them, and then peel off the insulation coating of the copper wires to obtain pretreated copper wires;

[0011] S2, oxidizing the end of the pretreated copper wire to obtain a copper wire with copper oxide on the surface;

[0012] S3, coating the copper oxide surface of the copper wire obtained in S2 with a two-dimensional atomic thick functional material, and polymerizing poly(3,4-ethylenedioxythiophene) by chemical polymerization and drying to obtain Cu-CuO containing active edge x -PEDOT / 2D;

[0013] S4, two Cu-CuO x -PEDOT / 2D active edge is assembled with electrolyte to obtain two-dimensional material based Cu-CuO x -PEDOT electrode assembly;

[0014] S5, placing a retractable metal wire in the microneedle, and setting a needle cap on the retractable metal wire at the tip of the microneedle;

[0015] S6. Two-dimensional material based Cu-CuO x The -PEDOT electrode assembly is placed inside the microneedle and connected to a detection device to obtain a micro humidity sensor based on two-dimensional materials.

[0016] The beneficial effects of the technical solution adopted in the present invention are as follows: the present invention adopts a chemical polymerization method to polymerize poly(3,4-ethylenedioxythiophene) to deposit poly(3,4-ethylenedioxythiophene) on the copper wire, and there is no need to directly immerse the copper wire containing copper oxide in an acidic electrolyte or apply voltage, thereby avoiding corrosion and dissolution of the thin copper wire; the copper oxide part of the copper wire containing copper oxide coated with a two-dimensional atomic thick functional material is placed in a prepared monomer solution for polymerization to achieve an ideal coating effect. This method produces a uniform and stable poly(3,4-ethylenedioxythiophene) film with a thickness of 0.01 to 1 μm, which is well attached to the surface of the copper wire containing copper oxide, maintaining the structural and functional integrity of the microneedle sensor.

[0017] Preferably, the diameter of the copper wire in S1 is 5 to 1000 μm; the inner diameter of the microneedle tip in S5 is more than twice the diameter of the copper wire in S1; and the cleaning is performed sequentially with isopropyl alcohol and deionized water for 1 to 3 times.

[0018] The beneficial effect of the above technical solution adopted in the present invention is that the inner diameter of the microneedle tip in S5 is more than twice the diameter of the copper wire in S1, so as to facilitate the entry and exit of the copper wire during use.

[0019] More preferably, the diameter of the copper wire in S1 is 10-100 μm.

[0020] More preferably, the inner diameter of the microneedle tip in S5 is 11 to 2500 μm.

[0021] More preferably, the inner diameter of the microneedle tip in S5 is 20 to 200 μm.

[0022] Preferably, S2 comprises the following steps: immersing the end of the pretreated copper wire in a methyl ethyl ketone solution with a mass concentration of 10 to 70% for oxidation for 1 to 600 minutes.

[0023] Preferably, the two-dimensional atomic thick functional material in S3 is graphene, chalcogenide or Mxene material.

[0024] More preferably, the two-dimensional atomic thick functional material in S3 is graphene nanosheets, graphene oxide nanosheets, MXene nanosheets, molybdenum disulfide nanosheets, tungsten disulfide nanosheets, bismuth sulfide nanosheets, bismuth selenide nanosheets, copper sulfide nanosheets, iron sulfur phosphide nanosheets, iron selenium phosphide nanosheets, hafnium disulfide nanosheets, hafnium diselenide nanosheets, hafnium ditelluride nanosheets, indium selenide nanosheets, manganese sulfur phosphide nanosheets, molybdenum ditelluride nanosheets, tungsten molybdenum sulfide nanosheets, tungsten molybdenum selenide nanosheets, niobium disulfide nanosheets, and diselenide nanosheets. At least one of niobium nanosheets, rhenium disulfide nanosheets, rhenium diselenide nanosheets, rhenium telluride nanosheets, tin sulfide nanosheets, tin disulfide nanosheets, nickel tantalum sulfide nanosheets, nickel tantalum selenide nanosheets, nickel tantalum telluride nanosheets, tantalum diselenide nanosheets, tantalum ditelluride nanosheets, titanium disulfide nanosheets, titanium diselenide nanosheets, vanadium diselenide nanosheets, tungsten diselenide nanosheets, tantalum sulfide nanosheets, tungsten ditelluride nanosheets, zirconium disulfide nanosheets, zirconium trisulfide nanosheets, zirconium diselenide nanosheets and zirconium triselenide nanosheets.

[0025] Preferably, the monomer solution used in the chemical polymerization method in S3 includes 3,4-ethylenedioxythiophene, sodium dodecyl sulfate, sulfuric acid and water; the volume ratio of 3,4-ethylenedioxythiophene, sodium dodecyl sulfate, sulfuric acid and water is (0.15-0.25):(0.0005-0.05):(0.1-5):20.

[0026] The beneficial effects of the technical solution adopted in the present invention are as follows: in the process of polymerizing poly(3,4-ethylenedioxythiophene) by the chemical polymerization method in the present invention, the use of a surfactant - sodium dodecyl sulfate can improve the compatibility of 3,4-ethylenedioxythiophene with water, and sulfuric acid is added to reduce the pH value of the overall monomer solution, thereby promoting efficient polymerization.

[0027] Preferably, the electrolyte in S4 is PVA / LiCl electrolyte.

[0028] The present invention also provides the application of the above-mentioned micro humidity sensor based on two-dimensional materials in humidity measurement in micro-nano space; the micro-nano space is the microenvironment inside plant tissues, inside biological structures, and in semi-closed or closed systems.

[0029] Preferably, the micro-nano space is inside plant tissue.

[0030] The beneficial effects of the present invention using the above technical solution are as follows: the micro humidity sensor of the present invention is small in size and non-invasive in design, and is suitable for monitoring plant transpiration, water transport and stress response in plant physiology research. In addition, the device is highly sensitive, durable, and can be calibrated to ensure repeatability.

[0031] Preferably, the application of the micro humidity sensor in micro-nano space humidity measurement comprises the following steps:

[0032] The micro humidity sensor based on two-dimensional materials is inserted into the micro-nano space, and the retractable metal wire is pushed to open the needle cap, so that the two-dimensional material-based Cu-CuO x -PEDOT electrode assembly is exposed in the micro-nano space, and the humidity level is recorded based on the changes in capacitance and conductivity detected by the detection device.

[0033] More preferably, the micro humidity sensor based on two-dimensional materials is operated by a micro manipulator.

[0034] More preferably, the detection device includes an electrochemical workstation and a data acquisition system.

[0035] The beneficial effect of the above technical solution adopted in the present invention is: a micromanipulator is used to insert the tip of a micro humidity sensor based on a two-dimensional material into a plant stem for operation. The top of the sensor is equipped with a needle cap, which can be opened or closed by pushing a hard retractable metal wire. When opened, the air can interact with the sensor to achieve humidity measurement. The consistency and repeatability of the sensor are ensured by precise control of the insertion and retraction process. The micromanipulator moves the sensor in calibrated small steps to maintain the accuracy of multiple readings. The sensor is repeatedly inserted and retracted, and the cover is opened and closed to capture dynamic humidity data, which is crucial for evaluating the long-term performance of the sensor. The data is extracted through the conductive end connected to the workstation (AutolabPGSTAT302N), which will give the change of the current signal according to the humidity change, including analyzing the capacitance change caused by the humidity change to ensure accurate and reliable measurement. The data acquisition system collects and stores this information and connects to the software for real-time monitoring and analysis. The working principle of the micro humidity sensor is that the two-dimensional material based Cu-CuO x The PEDOT layer of the -PEDOT electrode assembly is hygroscopic and changes conductivity with water vapor. The capacitance changes with humidity, thus measuring the humidity in the confined space. The device is calibrated before and after measurement to ensure consistency and accuracy. The calibration data is used to adjust the output signal to ensure reliable data for each measurement.

[0036] The present invention has the following beneficial effects:

[0037] The two-dimensional material based Cu-CuO of the present invention x -PEDOT electrode assembly has good mechanical integrity and long-term stability during use. The prepared micro humidity sensor allows high-sensitivity and stable humidity detection, and can be used under conditions with limited access or precise control of the environment, with strong reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1The schematic diagram of the structure of a micro humidity sensor based on two-dimensional materials; (a) is a Cu-CuO x -PEDOT / 2D and needle cap structure diagram; (b) is the two-dimensional material Cu-CuO in the microneedle x -Schematic diagram of the PEDOT electrode assembly, retractable metal wire and needle cap structure; (c) is a microscope image of the microneedle tip;

[0039] Figure 2 This is a schematic diagram of the application of a micro humidity sensor based on two-dimensional materials in measuring the humidity in plant stem tissue;

[0040] Figure 3 It is a humidity response diagram of the micro humidity sensor prepared in Example 1 and Comparative Example 1 measuring the humidity inside the plant stem tissue;

[0041] Figure 4 It is a humidity response diagram of the micro humidity sensor prepared in Example 1 under a humidity environment. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments.

[0043] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0044] The features and performance of the present invention are further described in detail below in conjunction with embodiments.

[0045] The electrochemical workstation used in the detection device in the embodiment is an Autolab electrochemical workstation PGSTAT302N, and the detection device also includes a data acquisition system.

[0046] Example 1

[0047] A micro humidity sensor based on two-dimensional materials, comprising a two-dimensional material-based Cu-CuO installed in a glass microneedle x -PEDOT electrode assembly, retractable metal wire, needle cap made of 2-ethyl cyanoacrylate and detection device; the retractable metal wire runs through the inside of the microneedle, the needle cap is located at the tip of the microneedle and connected to the retractable metal wire, and the detection device is connected to the two-dimensional material-based Cu-CuO x-PEDOT electrode assembly.

[0048] This embodiment also provides a method for preparing the above-mentioned micro humidity sensor based on two-dimensional materials, comprising the following steps:

[0049] S1. Take two copper wires with a diameter of 30 μm, wash them twice with isopropyl alcohol and deionized water in sequence, and then peel off the insulation coating at the edge of the copper wire by heating to expose 2 mm of copper wire. After peeling, wipe the exposed copper wire with isopropyl alcohol to obtain pretreated copper wire;

[0050] S2, immersing the end of the pretreated copper wire in a methyl ethyl ketone solution with a mass concentration of 30% for oxidation, taking it out after oxidation for 600 minutes and rinsing it with deionized water for 3 times to obtain a copper wire with copper oxide on the surface;

[0051] S3, coating the copper oxide surface of the copper wire obtained in S2 with a 10 nm thick graphene two-dimensional material ink, and polymerizing poly(3,4-ethylenedioxythiophene) by chemical polymerization and air drying to obtain Cu-CuO x -PEDOT / 2D; wherein the monomer solution used in the chemical polymerization method is obtained by dissolving 200 μL of 3,4-ethylenedioxythiophene in 20 mL of deionized water, adding 10 μL of sodium dodecyl sulfate and 1 mL of concentrated sulfuric acid with a mass concentration of 98%, and mixing well;

[0052] S4, two Cu-CuO x The active edge of PEDOT / 2D is assembled with PVA / LiCl electrolyte to obtain the two-dimensional material based Cu-CuO x -PEDOT electrode assembly;

[0053] S5, placing a retractable metal wire inside the microneedle and passing through both ends of the microneedle, and setting a needle cap made of 2-ethyl cyanoacrylate on the retractable metal wire at the tip of the microneedle; wherein the inner diameter of the microneedle tip is 70 μm;

[0054] S6. Two-dimensional material based Cu-CuO x The -PEDOT electrode assembly is placed inside the microneedle and connected to a detection device to obtain a micro humidity sensor based on two-dimensional materials.

[0055] This embodiment also provides an application of the above-mentioned two-dimensional material-based micro humidity sensor in measuring the internal humidity of plant stem tissue, including the following steps:

[0056] The tip of the micro humidity sensor based on two-dimensional materials was inserted into the plant stem using a micro-manipulator, and the retractable wire was pushed open by the micro-manipulator to open the needle cap, so that the Cu-CuO-based two-dimensional material x-PEDOT electrode assembly exposed to two-dimensional material based Cu-CuO in plant stem tissue x The humidity data captured by the PEDOT electrode assembly is extracted through the conductive end of the connected detection device electrochemical workstation and recorded through the data acquisition system, and further the current signal change is given according to the humidity change to realize data collection and storage.

[0057] Example 2

[0058] A micro humidity sensor based on two-dimensional materials, comprising a two-dimensional material-based Cu-CuO installed in a ceramic microneedle x -PEDOT electrode assembly, retractable metal wire, needle cap made of 2-ethyl cyanoacrylate and detection device; the retractable metal wire runs through the inside of the microneedle, the needle cap is located at the tip of the microneedle and connected to the retractable metal wire, and the detection device is connected to the two-dimensional material-based Cu-CuO x -PEDOT electrode assembly.

[0059] This embodiment also provides a method for preparing the above-mentioned micro humidity sensor based on two-dimensional materials, comprising the following steps:

[0060] S1. Take two copper wires with a diameter of 35 μm, wash them three times with isopropyl alcohol and deionized water in sequence, and then peel off the insulation coating at the edge of the copper wire by heating to expose 5 mm of copper wire. After peeling, wipe the exposed copper wire with isopropyl alcohol to obtain pretreated copper wire;

[0061] S2, immersing the end of the pretreated copper wire in a methyl ethyl ketone solution with a mass concentration of 50% for oxidation, taking it out after oxidation for 120 minutes and rinsing it with deionized water for 3 times to obtain a copper wire with copper oxide on the surface;

[0062] S3, coating the copper oxide surface of the copper wire obtained in S2 with a 10 nm thick two-dimensional material ink of molybdenum disulfide, and polymerizing poly(3,4-ethylenedioxythiophene) by chemical polymerization and air drying to obtain Cu-CuO containing active edge x -PEDOT / 2D; wherein the monomer solution used in the chemical polymerization method is obtained by dissolving 150 μL of 3,4-ethylenedioxythiophene in 20 mL of deionized water, adding 5 μL of sodium dodecyl sulfate and 1 mL of concentrated sulfuric acid with a mass concentration of 98%, and mixing well;

[0063] S4, two Cu-CuO x The active edge of PEDOT / 2D is assembled with PVA / LiCl electrolyte to obtain the two-dimensional material based Cu-CuO x -PEDOT electrode assembly;

[0064] S5, placing a retractable metal wire inside the microneedle and passing through both ends of the microneedle, and setting a needle cap made of 2-ethyl cyanoacrylate on the retractable metal wire at the tip of the microneedle; wherein the inner diameter of the microneedle tip is 80 μm;

[0065] S6. Two-dimensional material based Cu-CuO x The -PEDOT electrode assembly is placed inside the microneedle and connected to a detection device to obtain a micro humidity sensor based on two-dimensional materials.

[0066] This embodiment also provides an application of the above-mentioned two-dimensional material-based micro humidity sensor in measuring the internal humidity of plant stem tissue, including the following steps:

[0067] The tip of the micro humidity sensor based on two-dimensional materials was inserted into the plant stem using a micro-manipulator, and the retractable wire was pushed open by the micro-manipulator to open the needle cap, so that the Cu-CuO-based two-dimensional material x -PEDOT electrode assembly exposed in plant stem tissue, two-dimensional material based Cu-CuO x The humidity data captured by the PEDOT electrode assembly is extracted through the conductive end of the connected detection device electrochemical workstation and recorded through the data acquisition system, and further the current signal change is given according to the humidity change to realize data collection and storage.

[0068] Example 3

[0069] A micro humidity sensor based on two-dimensional materials, comprising a two-dimensional material-based Cu-CuO installed in a ceramic microneedle x -PEDOT electrode assembly, retractable metal wire, needle cap made of 2-ethyl cyanoacrylate and detection device; the retractable metal wire runs through the inside of the microneedle, the needle cap is located at the tip of the microneedle and connected to the retractable metal wire, and the detection device is connected to the two-dimensional material-based Cu-CuO x -PEDOT electrode assembly.

[0070] This embodiment also provides a method for preparing the above-mentioned micro humidity sensor based on two-dimensional materials, comprising the following steps:

[0071] S1. Take two copper wires with a diameter of 40 μm, wash them three times with isopropyl alcohol and deionized water in sequence, and then peel off the insulation coating at the edge of the copper wire by heating to expose 3 mm of copper wire. After peeling, wipe the exposed copper wire with isopropyl alcohol to obtain pretreated copper wire;

[0072] S2, immersing the end of the pretreated copper wire in a methyl ethyl ketone solution with a mass concentration of 70% for oxidation, taking it out after oxidation for 60 minutes and rinsing it with deionized water for 3 times to obtain a copper wire with copper oxide on the surface;

[0073] S3, coating the copper oxide surface of the copper wire obtained in S2 with a 10 nm thick MXene two-dimensional material ink, and polymerizing poly(3,4-ethylenedioxythiophene) by chemical polymerization and air drying to obtain Cu-CuO containing active edge x -PEDOT / 2D; wherein the monomer solution used in the chemical polymerization method is obtained by dissolving 250 μL of 3,4-ethylenedioxythiophene in 20 mL of deionized water, adding 20 μL of sodium dodecyl sulfate and 0.2 mL of concentrated sulfuric acid with a mass concentration of 98%, and mixing well;

[0074] S4, two Cu-CuO x The active edge of PEDOT / 2D is assembled with PVA / LiCl electrolyte to obtain the two-dimensional material based Cu-CuO x -PEDOT electrode assembly;

[0075] S5, placing a retractable metal wire inside the microneedle and passing through both ends of the microneedle, and setting a needle cap made of 2-ethyl cyanoacrylate on the retractable metal wire at the tip of the microneedle; wherein the inner diameter of the microneedle tip is 100 μm;

[0076] S6. Two-dimensional material based Cu-CuO x The -PEDOT electrode assembly is placed inside the microneedle and connected to a detection device to obtain a micro humidity sensor based on two-dimensional materials.

[0077] This embodiment also provides an application of the above-mentioned two-dimensional material-based micro humidity sensor in measuring the internal humidity of plant stem tissue, including the following steps:

[0078] The tip of the micro humidity sensor based on two-dimensional materials was inserted into the plant stem using a micro-manipulator, and the retractable wire was pushed open by the micro-manipulator to open the needle cap, so that the Cu-CuO-based two-dimensional material x -PEDOT electrode assembly exposed in plant stem tissue, two-dimensional material based Cu-CuO x The humidity data captured by the PEDOT electrode assembly is extracted through the conductive end of the connected detection device electrochemical workstation and recorded through the data acquisition system, and further the current signal change is given according to the humidity change to realize data collection and storage.

[0079] Comparative Example 1

[0080] A micro humidity sensor comprising Cu-CuO mounted in a glass microneedle x Electrode assembly, retractable metal wire, needle cap made of 2-ethyl cyanoacrylate and detection device; the retractable metal wire runs through the inside of the microneedle, the needle cap is located at the tip of the microneedle and connected to the retractable metal wire, and the detection device is connected to the Cu-CuO xElectrode assembly.

[0081] This comparative example also provides a method for preparing the above-mentioned micro humidity sensor, comprising the following steps:

[0082] S1. Take two copper wires with a diameter of 30 μm, wash them twice with isopropyl alcohol and deionized water in sequence, and then peel off the insulation coating at the edge of the copper wire by heating to expose 3 mm of the copper wire. After peeling, wipe the exposed copper end with isopropyl alcohol to obtain the pretreated copper wire;

[0083] S2, immersing the end of the pretreated copper wire in a methyl ethyl ketone solution with a mass concentration of 50% for oxidation, taking it out after oxidation for 60 minutes and rinsing it with deionized water for 3 times to obtain a copper wire with copper oxide on the surface;

[0084] S3, assembling the ends of two copper wires with copper oxide on the surface with PVA / LiCl electrolyte to obtain Cu-CuO x Electrode assembly;

[0085] S4, placing a retractable metal wire inside the microneedle and passing through both ends of the microneedle, and setting a needle cap made of 2-ethyl cyanoacrylate on the retractable metal wire at the tip of the microneedle; wherein the inner diameter of the microneedle tip is 70 μm;

[0086] S5, Cu-CuO x The electrode assembly is placed in the microneedle and connected to a detection device to obtain a micro humidity sensor.

[0087] This comparative example also provides an application of a micro humidity sensor in measuring the internal humidity of a plant stem tissue, comprising the following steps:

[0088] The tip of the micro humidity sensor was inserted into the plant stem using a micromanipulator, and the retractable wire was pushed open by the micromanipulator to open the needle cap, allowing the Cu-CuO x The electrode assembly was exposed in the plant stem tissue, Cu-CuO x The humidity data captured by the electrode assembly is extracted through the conductive end of the connected detection device electrochemical workstation and recorded through the data acquisition system, and further the current signal change is given according to the humidity change to realize data collection and storage.

[0089] Experimental example

[0090] The micro humidity sensors prepared in Example 1 and Comparative Example 1 were used to measure the humidity inside plant stem tissues and the signal responses of the detection devices were integrated. The results are as follows: Figure 3 shown.

[0091] Figure 3 In the figure, the light-colored line represents Cu-CuO, which was exposed to the same humidity environment for 5s. xHumidity response alone (Comparative Example 1), dark black line represents Cu-CuO x -Humidity response of PEDOT / 2D (Example 1); Cu-CuO x -The current signal and fast response / recovery time of PEDOT / 2D highlight the Cu-CuO x Advantages of combining with PEDOT / 2D; PEDOT as a sensing material and conductive interface stabilizes and amplifies Cu-CuO x The signal generated; Cu-CuO in the micro humidity sensor of the present invention x There is a complementary and synergistic effect between Cu-CuO and PEDOT / 2D. x and PEDOT / 2D as a combination of microneedle humidity sensors, Cu-CuO x The surface redox kinetics and water molecule adsorption show humidity sensitivity, thereby regulating its resistance; PEDOT / 2D further improves the conductivity of the system by changing the conductivity when exposed to water vapor, because water absorption affects its doping level and electronic properties. Therefore, the micro humidity sensor based on two-dimensional materials of the present invention has good sensitivity, stability and signal transduction ability, proving its superior performance in microneedle humidity sensing.

[0092] The micro humidity sensor prepared in Example 1 was exposed to a humidity environment for 18 seconds to detect the Cu-CuO x -Humidity response of PEDOT / 2D, the results are as follows Figure 4 As shown. Figure 4 It can be seen that the micro humidity sensor prepared by the present invention has high sensitivity to humidity response and good stability.

[0093] The present invention has been described according to the above embodiments. It should be understood that the above embodiments do not limit the present invention in any form. Any technical solutions obtained by equivalent replacement or equivalent transformation shall fall within the scope of the present invention.

Claims

1. A micro humidity sensor based on two-dimensional materials, characterized in that: Including two-dimensional material based Cu-CuO installed in microneedles x -PEDOT electrode assembly, retractable metal wire, needle cap and detection device; the retractable metal wire runs through the inside of the microneedle, the needle cap is located at the tip of the microneedle and connected to the retractable metal wire, and the detection device is connected to the two-dimensional material-based Cu-CuO x -PEDOT electrode assembly.

2. The micro humidity sensor based on two-dimensional material according to claim 1, characterized in that: The material of the microneedle is glass or ceramic; the material of the needle cap is 2-ethyl cyanoacrylate.

3. The method for preparing a micro humidity sensor based on a two-dimensional material according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1, take two copper wires, clean them, and then peel off the insulation coating of the copper wires to obtain pretreated copper wires; S2, oxidizing the end of the pretreated copper wire to obtain a copper wire with copper oxide on the surface; S3, coating the copper oxide surface of the copper wire obtained in S2 with a two-dimensional atomic thick functional material, and polymerizing poly(3,4-ethylenedioxythiophene) by chemical polymerization and drying to obtain Cu-CuO containing active edge x -PEDOT / 2D; S4, two Cu-CuO containing active edges x -PEDOT / 2D active edge is assembled with electrolyte to obtain two-dimensional material based Cu-CuO x -PEDOT electrode assembly; S5, placing a retractable metal wire in the microneedle, and setting a needle cap on the retractable metal wire at the tip of the microneedle; S6. Two-dimensional material based Cu-CuO x The -PEDOT electrode assembly is placed inside the microneedle and connected to a detection device to obtain a micro humidity sensor based on two-dimensional materials.

4. The method for preparing a micro humidity sensor based on two-dimensional materials according to claim 3, characterized in that: The diameter of the copper wire in S1 is 5 to 1000 μm; the inner diameter of the microneedle tip in S5 is more than twice the diameter of the copper wire in S1; the cleaning is performed sequentially with isopropyl alcohol and deionized water for 1 to 3 times.

5. The method for preparing a micro humidity sensor based on two-dimensional materials according to claim 3, characterized in that: The step S2 comprises the following steps: immersing the end of the pretreated copper wire in a methyl ethyl ketone solution with a mass concentration of 10 to 70% for oxidation for 1 to 600 minutes.

6. The method for preparing a micro humidity sensor based on two-dimensional materials according to claim 3, characterized in that: The two-dimensional atomic thick functional material in S3 is graphene, chalcogenide or Mxene material.

7. The method for preparing a micro humidity sensor based on two-dimensional materials according to claim 3, characterized in that: The monomer solution used in the chemical polymerization method in S3 includes 3,4-ethylenedioxythiophene, sodium dodecyl sulfate, sulfuric acid and water; the volume ratio of 3,4-ethylenedioxythiophene, sodium dodecyl sulfate, sulfuric acid and water is (0.15-0.25):(0.0005-0.05):(0.1-5):

20.

8. The method for preparing a micro humidity sensor based on two-dimensional materials according to claim 3, characterized in that: The electrolyte in S4 is PVA / LiCl electrolyte.

9. Application of the two-dimensional material-based micro humidity sensor described in any one of claims 1 to 2 in humidity measurement in micro-nano space; the micro-nano space is a microenvironment inside plant tissues, inside biological structures, and in semi-closed or closed systems.

10. The use according to claim 9, characterized in that The following steps are involved: The micro humidity sensor based on two-dimensional materials is inserted into the micro-nano space, and the retractable metal wire is pushed to open the needle cap, so that the two-dimensional material-based Cu-CuO x -PEDOT electrode assembly is exposed in the micro-nano space, and the humidity level is recorded based on the changes in capacitance and conductivity detected by the detection device.

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