Capacitive humidity sensor based on chitosan / sodium chloride / silica composite humidity-sensitive material and preparation method thereof

Abstract

The application belongs to the technical field of humidity sensing, and particularly relates to a capacitive humidity sensor based on a chitosan / sodium chloride / silicon dioxide composite humidity-sensitive material and a preparation method thereof. The humidity sensor comprises, from bottom to top, a silicon substrate, a silicon dioxide insulating layer, a platinum interdigital electrode and a composite humidity-sensitive material layer, and the composite humidity-sensitive material layer is a chitosan / sodium chloride / silicon dioxide composite material. The interdigital electrode is prepared by a stripping process, the chitosan-based composite humidity-sensitive film is prepared by a drop coating method, and a humidity response test is performed by using a humidity test system. The capacitive humidity sensor based on the chitosan / sodium chloride / silicon dioxide composite humidity-sensitive material has the characteristics of high sensitivity and fast response, is low in cost, green and environmentally friendly, simple in preparation process, and is expected to realize real-time monitoring of humidity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of humidity sensing, and particularly relates to a capacitive humidity sensor based on a chitosan / sodium chloride / silicon dioxide composite humidity-sensitive material and a preparation method thereof. BACKGROUND

[0002] It is well known that humidity monitoring is one of the important components of environmental monitoring, and plays a vital role in many fields such as automobiles, electronics manufacturing, food processing, agriculture, structural health monitoring and medical services. A humidity sensor can convert the humidity in the air into a measurable electric, optical, thermal, magnetic, force, etc. signal, and the principle is that the humidity-sensitive medium on the humidity-sensitive element is in contact with the water molecules in the air after adsorption or desorption, and the humidity-sensitive characteristic quantity is changed.

[0003] In recent years, various types of humidity sensors have been proposed, such as resistive, capacitive, quartz crystal microbalance (QCM), field effect transistor, optical fiber humidity sensor, etc. Among them, the capacitive humidity sensor has high sensitivity, good linearity, good stability, simple structure and other advantages, and occupies a dominant position in the market. However, the humidity in the environment changes dynamically, and real-time monitoring and accurate measurement are difficult to achieve, and the humidity sensor has the problems of low sensitivity, large humidity hysteresis and poor stability, so improving the performance of the sensor has been a hot topic. A humidity sensor generally consists of a humidity-sensitive material and a test electrode, and the quality of the humidity-sensitive material directly affects the performance of the sensor. At present, various materials such as synthetic polymers, ceramics, carbon-based materials and metal oxides have been used to make humidity sensors. However, there are still some challenges in preparing low-cost, biodegradable and environmentally friendly high-performance humidity sensors.

[0004] Chitosan (CS), as a renewable and biodegradable natural polymer, plays an important role in mitigating the harm of overuse of fossil fuels and synthetic polymers to the environment. Chitosan has the characteristics of rich natural sources, low cost, non-toxicity and good film-forming ability, and contains rich hydroxyl and amino groups, and has good hydrophilicity, so it is a good humidity-sensitive material. However, in the pure chitosan humidity sensor, chitosan as a polymer has poor long-term stability and slow response speed, so it is necessary to modify chitosan to further improve its sensing performance. SUMMARY

[0005] The present application relates to the technical field of humidity sensing, and particularly relates to a capacitive humidity sensor based on a chitosan / sodium chloride / silicon dioxide composite humidity-sensitive material and a preparation method thereof.

[0006] The capacitive humidity sensor based on the chitosan / sodium chloride / silicon dioxide composite humidity-sensitive material comprises, from bottom to top, a silicon substrate, a silicon dioxide insulation layer, a platinum interdigital electrode and a composite humidity-sensitive material layer, and the composite humidity-sensitive material layer is a chitosan / sodium chloride / silicon dioxide composite material.

[0007] In the technical scheme, the sodium chloride as an ionic crystal can improve the ionic mobility of the composite material, improve the dielectric property of the composite material, improve the sensitivity of the sensor, the nano silicon dioxide can support the structure of the composite material, increase the specific surface area of the composite material, improve the response speed and stability of the sensor, and the humidity sensor based on the chitosan / sodium chloride / silicon dioxide composite humidity-sensitive material can realize high sensitivity and fast response.

[0008] Correspondingly, the application further provides a preparation method of the capacitive humidity sensor based on the chitosan / sodium chloride / silicon dioxide composite humidity-sensitive material.

[0009] (1) Preparing the platinum interdigital electrode: cleaning the silicon wafer with acetone, ethanol and deionized water in sequence, drying after cleaning, depositing a 200-nm silicon dioxide insulation layer on the silicon substrate by the method of plasma chemical vapor deposition, then performing photoetching and developing, drying with nitrogen blowing, then sputtering a 10-nm titanium layer and a 300-nm platinum layer on the substrate in sequence by the method of magnetron sputtering, then immersing the sputtered silicon wafer in acetone, and finally performing peeling, drying and slicing to obtain the interdigital electrode, which is cleaned and dried for standby use;

[0010] (2) Preparing the film-forming solution: measuring a certain amount of 3% acetic acid aqueous solution, adding chitosan and sodium chloride in a certain proportion, then adding a proper amount of glycerol after magnetic stirring for 1 h, then stirring for 14 h, then adding a proper amount of nano silicon dioxide, and then ultrasonicating for 15 min to obtain the chitosan / sodium chloride / silicon dioxide mixed solution for standby use;

[0011] (3) Preparing the humidity-sensitive film: using a micropipette to suck a proper amount of the prepared solution, adopting the method of drop coating to drop the solution to the central region of the interdigital electrode to make it uniformly distributed, then placing it on a heating table to heat at 60 DEG C for 4 h to ensure complete evaporation of the solvent, and then standing the prepared humidity-sensitive film for standby use;

[0012] (4) Welding the test lead: pasting the silicon substrate with the prepared humidity-sensitive film on the designed PCB board, connecting the Pad on the electrode with the land on the PCB board by the method of gold wire welding, then leading out the lead from the land to facilitate the test by the humidity test system, and finally preparing the chitosan-based humidity sensor.

[0013] Preferably, in the interdigital electrode, the interdigital width and the interdigital spacing are both 10 mu m, and the number of interdigital electrodes is 100.

[0014] More preferably, the mass fraction of chitosan in the solution is 1wt%, the mass fraction of sodium chloride is 0.1-1wt%, and the mass fraction of silicon dioxide is 0.1-1wt%.

[0015] Further, the humidity test system comprises an air generator, a syringe pump, a cavity, a humidity sensor probe, an LCR digital bridge and a computer, and the components are connected to form the humidity test system.

[0016] The above technical solution has the following beneficial effects:

[0017] (1) Chitosan is a natural high molecular polymer with good hydrophilicity. Compared with synthetic polymers, chitosan has the advantages of abundant natural sources, low cost, non-toxicity and biodegradability, and is an environmentally friendly material.

[0018] (2) Sodium chloride (NaCl) can improve the ion mobility of the composite material, improve the ion polarization and interface polarization, improve the dielectric properties of the chitosan-based film, increase the dielectric constant, and increase the capacitance of the sensor, thereby greatly improving the sensitivity of the sensor.

[0019] (3) The silica (SiO2) nanoparticles support the structure of the composite material, can increase the adsorption sites for water molecules, increase the specific surface area of the composite material, and is beneficial to the adsorption and desorption of water molecules, thereby improving the response speed and stability of the sensor.

[0020] (4) The CS / NaCl / SiO2 humidity sensor is prepared by drop coating method, which has simple preparation process, is green and environmentally friendly, and has low cost.

[0021] (5) The capacitive humidity sensor based on the CS / NaCl / SiO2 composite humidity-sensitive material has high sensitivity and fast response, and can realize dynamic response. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a preparation flowchart of interdigital electrodes;

[0023] Figure 2 is a preparation schematic diagram of the CS / NaCl / SiO2 composite film;

[0024] Figure 3 is a schematic diagram of a humidity test system;

[0025] Figure 4 is a curve diagram of the capacitance of the CS humidity sensor varying with relative humidity under different test frequencies;

[0026] Figure 5 is a response curve of CS and CS / NaCl / SiO2 humidity sensor to humidity;

[0027] Figure 6 is a response curve of CS and CS / NaCl / SiO2 under 6%RH and 62%RH. DETAILED DESCRIPTION

[0028] To make the technical content, structural features, purposes and effects of the technical scheme clear, the following will be described in detail in conjunction with specific embodiments and the accompanying drawings.

[0029] As shown in Figure 1 and Figure 2 , the present scheme provides a capacitive humidity sensor based on CS / NaCl / SiO2 composite humidity-sensitive material, which comprises from bottom to top a silicon substrate, a silicon dioxide insulation layer, a platinum interdigital electrode and a composite humidity-sensitive material layer, wherein the silicon dioxide insulation layer is obtained by deposition, the interdigital electrode is prepared by a stripping process, including photolithography, sputtering and stripping, etc., and the composite humidity-sensitive material layer is a chitosan / sodium chloride / silicon dioxide composite material prepared by a drop coating method.

[0030] Embodiment 1

[0031] The present embodiment provides a preparation method of a capacitive humidity sensor based on chitosan / sodium chloride / silicon dioxide composite humidity-sensitive material, comprising the following steps:

[0032] (1) Preparation of interdigital electrode: clean the silicon wafer with acetone, ethanol and deionized water in sequence, dry after cleaning, deposit a 200 nm silicon dioxide insulation layer on the silicon substrate by plasma chemical vapor deposition, then perform photolithography and development, dry with nitrogen blowing and then dry, then sputter a 10 nm thick titanium layer and a 300 nm thick platinum layer on the substrate by magnetron sputtering, then immerse the sputtered silicon wafer in acetone, and finally perform stripping, drying and slicing to obtain the interdigital electrode, which is cleaned and dried for standby;

[0033] (2) Preparation of film-forming solution: measure 10 ml of 3% acetic acid aqueous solution, add 0.1 g of chitosan and 0.01 g of sodium chloride, magnetically stir for 1 h, then add 0.5 ml of glycerol, stir for 14 h, add 0.01 g of nano-silicon dioxide, and then ultrasonic for 15 minutes to obtain a chitosan / sodium chloride / silicon dioxide mixed solution for standby;

[0034] (3) Preparation of humidity-sensitive film: use a micropipette to suck 3 μL of the prepared solution, drop the solution onto the center area of the interdigital electrode by drop coating, make it uniformly distributed, and then place it on a heating table at 60℃ for heating for 4 h to ensure complete evaporation of the solvent, and the prepared humidity-sensitive film is placed for standby;

[0035] (4) Welding test leads: The prepared humidity-sensitive film silicon substrate is attached to the designed PCB board, the Pad on the electrode is connected to the solder pad on the PCB board using gold wire welding, and then the leads are drawn out from the solder pad to facilitate testing with a humidity test system, and a chitosan / sodium chloride / silicon dioxide humidity sensor is prepared.

[0036] Example 2

[0037] The present embodiment provides a preparation method of a capacitive humidity sensor based on chitosan / sodium chloride / silicon dioxide composite humidity-sensitive material, comprising the following steps:

[0038] (1) Preparation of interdigital electrode: The silicon wafer is sequentially cleaned with acetone, ethanol and deionized water, and then dried. A 200 nm thick silicon dioxide insulation layer is deposited on the silicon substrate by plasma chemical vapor deposition, and then photoetching and development are performed. After drying with nitrogen, the substrate is dried, and then a 10 nm thick titanium layer and a 300 nm thick platinum layer are sputtered on the substrate by magnetron sputtering. Then the sputtered silicon wafer is soaked in acetone, and finally peeled off, dried and sliced to obtain the interdigital electrode, which is cleaned and dried for standby;

[0039] (2) Preparation of film solution: 10 ml of 3% acetic acid aqueous solution, 0.1 g of chitosan and 0.05 g of sodium chloride are added, and then stirred for 1 h. Then 0.5 ml of glycerol is added, and then stirred for 14 h. Then 0.01 g of nano-silicon dioxide is added, and then ultrasonic is performed for 15 minutes to obtain a chitosan / sodium chloride / silicon dioxide mixed solution for standby;

[0040] (3) Preparation of humidity-sensitive film: 3 μL of the prepared solution is taken by a micropipette, and then dropped on the center area of the interdigital electrode by drop coating to make it evenly distributed. Then it is placed on a heating table at 60°C for 4 h to ensure complete evaporation of the solvent. The prepared humidity-sensitive film is placed for standby;

[0041] (4) Welding test leads: The prepared humidity-sensitive film silicon substrate is attached to the designed PCB board, the Pad on the electrode is connected to the solder pad on the PCB board using gold wire welding, and then the leads are drawn out from the solder pad to facilitate testing with a humidity test system, and a chitosan / sodium chloride / silicon dioxide humidity sensor is prepared.

[0042] Example 3

[0043] The present embodiment provides a preparation method of a capacitive humidity sensor based on chitosan / sodium chloride / silicon dioxide composite humidity-sensitive material, comprising the following steps:

[0044] (1) Preparation of interdigital electrode: the silicon wafer is sequentially cleaned with acetone, ethanol and deionized water, and then dried. A 200 nm thick silicon dioxide insulating layer is deposited on the silicon substrate by plasma chemical vapor deposition. Then, photoetching and development are performed, and the substrate is dried with nitrogen and then baked. Subsequently, a 10 nm thick titanium layer and a 300 nm thick platinum layer are sputtered on the substrate by magnetron sputtering. Then, the sputtered silicon wafer is soaked in acetone. Finally, peeling, drying and slicing are performed, and the obtained interdigital electrode is cleaned and dried for standby use.

[0045] (2) Preparation of film solution: 10 ml of 3% acetic acid aqueous solution is measured, 0.1 g of chitosan and 0.1 g of sodium chloride are added, and magnetic stirring is performed for 1 h. Then, 0.5 ml of glycerol is added, and stirring is performed for 14 h. Then, 0.01 g of nano-silicon dioxide is added, and ultrasonic treatment is performed for 15 min. Thus, a chitosan / sodium chloride / silicon dioxide mixed solution is obtained for standby use.

[0046] (3) Preparation of humidity-sensitive film: 3 μL of the prepared solution is taken by using a micropipette, and the solution is dropped onto the center region of the interdigital electrode by drop coating, so as to be uniformly distributed. Then, the substrate is placed on a heating table and heated at 60°C for 4 h to ensure complete evaporation of the solvent. The prepared humidity-sensitive film is allowed to stand for standby use.

[0047] (4) Soldering test lead: the silicon substrate with the prepared humidity-sensitive film is attached to the designed PCB board, and the Pad on the electrode is connected to the pad on the PCB board by using gold wire soldering. Then, the lead wire is drawn out from the pad to facilitate testing by using a humidity test system. Thus, a chitosan / sodium chloride / silicon dioxide humidity sensor is prepared.

[0048] Example 4

[0049] The present embodiment provides a preparation method of a capacitive humidity sensor based on a chitosan / sodium chloride / silicon dioxide composite humidity-sensitive material, which comprises the following steps:

[0050] (1) Preparation of interdigital electrode: the silicon wafer is sequentially cleaned with acetone, ethanol and deionized water, and then dried. A 200 nm thick silicon dioxide insulating layer is deposited on the silicon substrate by plasma chemical vapor deposition. Then, photoetching and development are performed, and the substrate is dried with nitrogen and then baked. Subsequently, a 10 nm thick titanium layer and a 300 nm thick platinum layer are sputtered on the substrate by magnetron sputtering. Then, the sputtered silicon wafer is soaked in acetone. Finally, peeling, drying and slicing are performed, and the obtained interdigital electrode is cleaned and dried for standby use.

[0051] (2) Preparation of film solution: take 10ml 3% acetic acid aqueous solution, add 0.1g chitosan and 0.05g sodium chloride, magnetic stirring for 1h, then add 0.5ml glycerol, then stirring for 14h, add 0.05g nanometer silicon dioxide, then ultrasonic for 15 minutes, get chitosan / sodium chloride / silicon dioxide mixed solution for standby;

[0052] (3) Preparation of humidity sensitive film: use micropipette to suck 3μL prepared solution, adopt drop coating method, drop solution to the center area of interdigital electrode, make it evenly distributed, then place on heating table at 60℃ for 4h, ensure complete evaporation of solvent, prepare humidity sensitive film for standby;

[0053] (4) Welding test lead: paste the silicon substrate with prepared humidity sensitive film on the designed PCB board, use gold wire welding method to connect the Pad on electrode and the pad on PCB board, then lead out the lead from the pad for easy testing with humidity test system, make chitosan / sodium chloride / silicon dioxide humidity sensor.

[0054] Example 5

[0055] The embodiment provides a preparation method of a capacitive humidity sensor based on chitosan / sodium chloride / silicon dioxide composite humidity sensitive material, including the following steps:

[0056] (1) Preparation of interdigital electrode: clean the silicon wafer with acetone, ethanol and deionized water in sequence, clean and dry, deposit a 200nm silicon dioxide insulation layer on the silicon substrate by plasma chemical vapor deposition method, then perform photoetching and developing, dry with nitrogen and dry, then sputter a 10nm thick titanium layer and a 300nm thick platinum layer on the substrate by magnetron sputtering method, then immerse the sputtered silicon wafer in acetone, finally perform peeling, drying and slicing, and the obtained interdigital electrode is cleaned and dried for standby;

[0057] (2) Preparation of film solution: take 10ml 3% acetic acid aqueous solution, add 0.1g chitosan and 0.05g sodium chloride, magnetic stirring for 1h, then add 0.5ml glycerol, then stirring for 14h, add 0.1g nanometer silicon dioxide, then ultrasonic for 15 minutes, get chitosan / sodium chloride / silicon dioxide mixed solution for standby;

[0058] (3) Preparation of humidity sensitive film: use micropipette to suck 3μL prepared solution, adopt drop coating method, drop solution to the center area of interdigital electrode, make it evenly distributed, then place on heating table at 60℃ for 4h, ensure complete evaporation of solvent, prepare humidity sensitive film for standby;

[0059] (4) welding test lead wire: the silicon substrate with prepared humidity sensitive membrane is pasted on the designed PCB board, the pad on the electrode is connected with the pad on the PCB board by using gold wire welding, then the lead wire is led out from the pad to facilitate the test by using the humidity test system, and the chitosan / sodium chloride / silicon dioxide humidity sensor is prepared.

[0060] Comparative Example 1

[0061] The embodiment provides a preparation method of a chitosan-based capacitive humidity sensor, and comprises the following steps:

[0062] (1) preparing an interdigital electrode: the silicon wafer is cleaned with acetone, ethanol and deionized water in sequence, and then dried; a 200 nm silicon dioxide insulation layer is deposited on the silicon substrate by plasma chemical vapor deposition; then photoetching and developing are performed, and the substrate is dried by blowing nitrogen and then baking; then a 10 nm thick titanium layer and a 300 nm thick platinum layer are sputtered on the substrate by magnetron sputtering; then the sputtered silicon wafer is soaked in acetone; finally, peeling, drying and slicing are performed, and the obtained interdigital electrode is cleaned and dried for standby;

[0063] (2) preparing a film-forming solution: 10 ml of 3% acetic acid aqueous solution is measured, 0.1 g of chitosan is added, and then the mixture is magnetically stirred for 1 h; then 0.5 ml of glycerol is added, and the mixture is stirred for 14 h to obtain a chitosan solution for standby;

[0064] (3) preparing a humidity sensitive membrane: 3 μL of the prepared solution is taken by using a micropipette, and the solution is dropped on the center region of the interdigital electrode by drop coating, so that the solution is uniformly distributed; then the humidity sensitive membrane is placed on a heating table and heated at 60℃ for 4 h to ensure that the solvent is completely volatilized; and finally, the prepared humidity sensitive membrane is placed for standby;

[0065] (4) welding test lead wire: the silicon substrate with prepared humidity sensitive membrane is pasted on the designed PCB board, the pad on the electrode is connected with the pad on the PCB board by using gold wire welding, then the lead wire is led out from the pad to facilitate the test by using the humidity test system, and the chitosan humidity sensor is prepared.

[0066] As shown in Figure 3 , the humidity sensor of the present application is tested by using the built humidity test system, the relative humidity of the gas is adjusted by controlling the dry air flow of the air generator (PGA-6L) and the deionized water flow of the injection pump (SPLAb01), and the sensor measurement is performed at different relative humidity levels. The capacitance of the sensor is measured by an LCR meter (TH2832), and the working voltage is 1V.

[0067] Figure 4For the curves of the capacitance of the CS humidity sensor versus relative humidity at different test frequencies 500Hz, 1kHz, 10kHz, 100kHz and 200kHz, it can be seen that the capacitance increases with the increase of humidity, and there is a clear humidity response. Moreover, the working frequency in the sensor measurement will affect the capacitance characteristics of the humidity sensor. It can be seen from the figure that the greater the test frequency, the smaller the capacitance. The linearity of the curves at 500Hz and 1kHz is better, while the low frequency is more affected by noise, so 1kHz is selected as the working frequency of the sensor.

[0068] Figure 5 For the sensitivity test graph of pure chitosan and chitosan / sodium chloride / silicon dioxide humidity sensor, it can be seen that both sensors have a clear humidity response and good linearity. The sensitivity of the pure chitosan humidity sensor is 0.26nF / %RH, and the sensitivity of the chitosan / sodium chloride / silicon dioxide humidity sensor is 0.64nF / %RH. The addition of sodium chloride and nanosilicon dioxide improves the sensitivity of the sensor by nearly 1.5 times. The capacitive humidity sensor based on chitosan / sodium chloride / silicon dioxide composite humidity-sensitive material has high sensitivity.

[0069] Figure 6 For the humidity response curves of CS and CS / NaCl / SiO2 under the change from 6%RH to 62%RH, it can be seen that both CS and CS / NaCl / SiO2 humidity sensors have a fast response.

[0070] It should be noted that in this text, relational terms such as first and second are used only to distinguish one entity or action from another, and do not necessarily require or imply that there is any such actual relationship or order between these entities or actions. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or terminal device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or terminal device. Without more limitations, the elements defined by the statement "include" or "contain" do not exclude the existence of other elements in the process, method, article or terminal device including the elements. In addition, in this text, "greater than", "less than", "exceed" and the like are understood as not including the number; "above", "below", "within" and the like are understood as including the number.

[0071] Although the above-mentioned embodiments have been described, those skilled in the art can make further changes and modifications to the embodiments once they know the basic inventive concept, and therefore the above-mentioned embodiments are only examples of the present application, and are not intended to limit the patent protection scope of the present application, and any equivalent structure or equivalent process transformation made by using the content of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A capacitive humidity sensor based on a chitosan / sodium chloride / silica composite humidity-sensitive material, the capacitive humidity sensor comprising, from bottom to top, a silicon substrate, a silica insulation layer, a platinum interdigital electrode, and a composite humidity-sensitive material layer, characterized in that, The composite humidity-sensitive material layer is a chitosan / sodium chloride / silicon dioxide composite material; The preparation method of the capacitive humidity sensor comprises the following steps: (1) preparing a platinum interdigital electrode: a silicon wafer is cleaned with acetone, ethanol and deionized water in sequence, and then dried; a 200 nm silicon dioxide insulation layer is deposited on the silicon substrate by plasma chemical vapor deposition; photoetching and developing are performed, and the substrate is dried with nitrogen and then baked; then, a 10 nm thick titanium layer and a 300 nm thick platinum layer are sputtered on the substrate in sequence by magnetron sputtering; then, the sputtered silicon wafer is soaked in acetone; finally, peeling, drying and slicing are performed, and the obtained interdigital electrode is cleaned and dried for standby; the interdigital width and the interdigital spacing are both 10 μm, and the number of interdigital electrodes is 100; (2) preparing a film solution: a certain amount of 3% acetic acid aqueous solution is measured, chitosan and sodium chloride are added at a certain ratio, and then the mixture is magnetically stirred for 1 h; then, a proper amount of glycerol is added, and the mixture is stirred for 14 h; then, a proper amount of nano-silicon dioxide is added, and the mixture is ultrasonically treated for 15 min to obtain a chitosan / sodium chloride / silicon dioxide mixed solution for standby; the mass fraction of chitosan is 1 wt%, the mass fraction of sodium chloride is 0.1-1 wt%, and the mass fraction of silicon dioxide is 0.1-1 wt%; (3) preparing a humidity-sensitive film: a proper amount of the prepared solution is taken by using a micropipette, and the solution is dropped on the center area of the interdigital electrode by drop coating, so that the solution is uniformly distributed; then, the humidity-sensitive film is prepared by heating the solution on a heating table at 60 ℃ for 4 h to ensure that the solvent is completely volatilized; and the prepared humidity-sensitive film is placed for standby; (4) welding test leads: the silicon substrate with the prepared humidity-sensitive film is attached to a designed PCB board, the pads on the electrode are connected to the pads on the PCB board by using gold wire welding, then the leads are drawn out from the pads to facilitate testing by using a humidity test system, and finally a chitosan-based humidity sensor is prepared.

2. The capacitive humidity sensor of claim 1, wherein, The humidity test system in step (4) comprises an air generator, a syringe pump, a cavity, a humidity sensor probe, an LCR digital bridge and a computer, and the components are connected to form a humidity test system, wherein the relative humidity of the mixed gas is adjusted by adjusting the dry gas flow of the air generator and the deionized water flow of the syringe pump.

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