Humidity sensor with heating and drying functions and processing method thereof

Abstract

The invention relates to the technical field of humidity sensors, and discloses a humidity sensor with heating and drying functions and a processing method thereof, and the humidity sensor comprises a humidity sensitive layer, a first interdigital electrode, a substrate layer, a heat insulation film, a heating circuit, a water absorption layer and a moisture conduction hole. The water absorption layer is arranged to be matched with the moisture guide hole structure, surplus water vapor accumulated on the upper surface of the humidity sensor can be absorbed, and the problem of performance reduction caused by water vapor accumulation due to long-term use of the humidity sensor is solved. The heating circuit is arranged and can be used for drying the water absorption layer, so that the water absorption layer can continuously play a role in absorbing water vapor gathered by the sensor. Meanwhile, by arranging the heat insulation film, heat generated by the heating circuit can be effectively prevented from diffusing to the outside of the sensor, it is ensured that the heat directionally acts on the water absorption layer to achieve efficient drying, meanwhile, it is avoided that temperature interferes with the detection precision of the humidity sensitive layer, and the sensor and the surrounding environment are not affected.

Description

Technical Field

[0001] The invention relates to the technical field of humidity sensors, and in particular to a humidity sensor with heating and drying functions and a processing method thereof. Background Art

[0002] Humidity is an important physical parameter to measure the water vapor content in the air. Its accurate detection plays an indispensable and key role in many fields such as meteorological monitoring, industrial production, medical and health care, agricultural cultivation, warehousing and logistics, and smart home. Among the various existing humidity detection methods, humidity sensors based on humidity-sensitive materials have become the most widely used detection method due to their simple structure, fast response, and moderate cost.

[0003] The working principle of the humidity sensor determines that it must complete the detection process through the direct contact of water molecules with the device's humidity-sensitive material. Specifically, the sensor's humidity-sensitive element needs to be completely exposed to the atmosphere of the environment to be tested, and no protective isolation layer can be set on the surface of the humidity-sensitive material. Although this open structure design ensures the detection sensitivity, it also brings significant usage problems: during long-term operation, water molecules in the environment will continue to adsorb and aggregate on the sensor surface, gradually forming a water molecule layer. This water molecule accumulation phenomenon will significantly change the surface properties and detection accuracy of the humidity-sensitive material, which is specifically manifested in the gradual slowing down of the sensor's response speed (typically, the response time may be extended by 30-50% after half a year of use), and the detection sensitivity is significantly reduced (sensitivity attenuation can reach more than 20%), which ultimately causes the measurement accuracy to deviate seriously from the actual ambient humidity value.

[0004] In response to this common problem in the industry, the mainstream solution on the market is to directly heat the sensor periodically. This method is usually implemented by integrating a heating resistor inside the sensor, and evaporating and desorbing the accumulated water molecules through short-term high temperature (usually 150-200°C). However, this solution has obvious limitations: first, in special application scenarios such as petrochemicals, flammable and explosive materials, high-temperature operation poses serious safety hazards; second, the local temperature rise generated by the heating process will affect the actual humidity distribution of the surrounding environment, resulting in a decrease in the accuracy of the measured humidity value; third, frequent thermal cycles will accelerate the aging of the humidity-sensing material, and the number of heating regenerations of a typical commercial sensor generally does not exceed 5,000 times. These inherent defects make traditional heated humidity sensors face severe challenges in precision measurement and special environmental applications.

[0005] SUMMARY OF THE INVENTION

[0006] The technical problem solved by the present invention is: how to prevent the performance degradation of the humidity sensor caused by the accumulation of water vapor due to long-term use.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A humidity sensor with a heating and drying function, comprising:

[0009] A substrate layer;

[0010] A first interdigital electrode, the first interdigital electrode is fixedly arranged on one side of the substrate layer, and the first comb structure of the first interdigital electrode is connected to the data acquisition device through a pad;

[0011] A humidity sensitive layer, the humidity sensitive layer is fixedly attached to the substrate layer and is located outside the first interdigital electrode, covering the area where the first comb structure is located;

[0012] A heat insulation film, the heat insulation film is located on the side of the substrate layer away from the humidity sensitive layer and is fixedly attached to the substrate layer conformally;

[0013] A heating circuit, the heating circuit is fixedly arranged on the side of the heat insulation film away from the substrate layer, and includes a heating resistor and a pad for connecting to a power supply;

[0014] A water absorption layer, the water absorption layer is fixedly attached to the heat insulation film and is located outside the heating resistor;

[0015] Wherein, a plurality of moisture-conducting holes are provided through the humidity sensitive layer, the substrate layer and the heat insulation film, and the heating resistor is bent around the moisture-conducting holes.

[0016] In one aspect of the present invention: a second interdigital electrode is further provided on the heat insulation film, and the second interdigital electrode is used to detect the humidity data of the water absorption layer.

[0017] In one aspect of the present invention: the substrate layer is made of a thermoplastic polymer material with a thickness of 20-250 μm.

[0018] In one aspect of the present invention: the first comb structure of the first interdigital electrode includes 10-50 pairs of comb tooth structures arranged alternately, the electrode line width is 10-100 μm and the thickness is 200-800 nm, and the ratio of the comb tooth spacing to the line width ranges from 1:1 to 5:1.

[0019] In one aspect of the present invention: the heat insulation film is made of a flexible dielectric material with a thermal conductivity ≤ 0.5 W / (m·K).

[0020] In one aspect of the present invention: the diameter of the moisture-conducting holes is 10-500 μm, the moisture-conducting holes are arranged staggered with the comb teeth of the first interdigital electrode, wherein the ratio of the adjacent micropore spacing to the pore diameter is 2:1 to 10:1.

[0021] In one embodiment of the present invention: The heating circuit is made of a metal material, integrated in a serpentine structure on the surface of the heat insulation film. The line width of the heating circuit is 20 - 200 μm, the adjacent trace spacing is 1 - 5 times the line width, and the thickness is 200 - 800 nm. The heating resistance traces of the heating circuit are arranged to bypass the moisture guiding holes, and each serpentine loop wraps 5 - 15 micropores. The pads of the heating circuit are arranged in the non - working area at the edge of the heat insulation film, and the minimum distance between the pads and the moisture guiding holes is ≥ 3 times the line width.

[0022] In one embodiment of the present invention: The water - absorbing layer is composed of a hygroscopic polymer material, with a heat resistance ≥ 100 °C and a moisture absorption rate ≥ 500% (under the condition of 90% RH).

[0023] In one embodiment of the present invention: The water - absorbing layer is coated on the surfaces of the heat insulation film, the heating circuit, and the second interdigital electrode through a conformal coating process, and is in close contact with the moisture guiding holes. The water - absorbing layer is provided with an avoidance structure in the pad area, and the avoidance width is 50 - 200 μm to ensure circuit conductivity.

[0024] A processing method of a humidity sensor with a heating and drying function

[0025] comprises the following steps:

[0026] S1. Substrate layer treatment: Form a first interdigital electrode on the upper surface of the substrate layer through a photolithography or laser patterning process. The electrode material is a metal or a composite conductive thin film.

[0027] S2. Humidity - sensitive layer preparation: Coat a humidity - sensitive material dispersion liquid containing a polymer matrix and a nano - dopant on the surface of the first interdigital electrode, and form a humidity - sensitive layer after drying. The drying conditions are a vacuum or an inert gas environment, a temperature of 40 - 80 °C, and a time of 0.5 - 2 h.

[0028] S3. Heat insulation film integration: Form a heat insulation film on the lower surface of the substrate layer through a spin - coating, spraying, or hot - pressing process. Its thermal conductivity ≤ 0.1 W / (m·K), and the thickness is 10 - 100 μm.

[0029] S4. Moisture guiding hole processing: Use a laser processing, ion etching, or mechanical punching process to form a micropore array penetrating the substrate layer, the heat insulation film, and the humidity - sensitive layer between the teeth of the first interdigital electrode. The pore diameter is 5 - 200 μm, and the pore density is 100 - 1000 holes / cm 2 ;

[0030] S5. Fabrication of the heating circuit and the second interdigital electrode: Simultaneously form the heating circuit and the second interdigital electrode on the surface of the heat insulation film through a sputtering, printing, or electroplating process, where:

[0031] The heating circuit is a spiral or grid-shaped resistive structure, and the resistive material is nickel-chromium alloy, platinum or doped oxide semiconductor;

[0032] The right fork-shaped electrode of the second interdigital electrode is connected to the heating circuit through coplanar wiring and shares the same pad;

[0033] S6. Water-absorbing layer encapsulation: A water-absorbing layer is formed on the surfaces of the heat-insulating film, heating circuit and second interdigital electrode through impregnation, inkjet printing or vapor deposition processes, and selective coverage is achieved in the pad area through a masking or laser removal process.

[0034] A humidity sensor with a heating and drying function and a processing method thereof according to the present invention has at least one of the following technical effects:

[0035] By providing a water-absorbing layer and a moisture-conducting hole array penetrating through the humidity-sensitive layer, substrate layer and heat-insulating film, the water-absorbing layer can absorb the surplus water vapor accumulated on the upper surface of the flexible humidity sensor, avoiding the problem of performance degradation caused by the accumulation of water vapor on the humidity sensor due to long-term use. Ensure the response speed, detection accuracy and sensitivity of the humidity sensor.

[0036] A heating circuit is provided to dry the water-absorbing layer, enabling the water-absorbing layer to continuously play the role of absorbing the water vapor accumulated by the sensor. At the same time, by providing a heat-insulating film, the heat generated by the heating circuit can be effectively blocked from diffusing to the outside of the sensor, ensuring that the heat acts on the water-absorbing layer directionally for efficient drying, while avoiding temperature interference with the detection accuracy of the humidity-sensitive layer and not affecting the sensor and the surrounding environment.

[0037] An interdigital electrode is provided in cooperation with the heating circuit to detect the humidity of the water-absorbing layer, so as to timely start the heating circuit to heat and dry the water-absorbing layer when the humidity of the water-absorbing layer reaches a certain value, ensuring the continuous water absorption effect of the water-absorbing layer on water vapor.

[0038] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand in the description of the embodiments in conjunction with the following drawings. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. Among them:

[0040] Figure 1 is a schematic structural diagram of an overall humidity sensor with a heating and drying function according to the present invention;

[0041] Figure 2 is a humidity sensor with a heating and drying function according to the present invention Figure 1 a schematic top view structure diagram of the middle liner layer;

[0042] Figure 3 is a three-dimensional structure diagram of the heating circuit on the heat insulation film of a humidity sensor with a heating and drying function according to the present invention;

[0043] Figure 4 is a humidity sensor with a heating and drying function according to the present invention Figure 1 a schematic bottom view structure diagram of the heat insulation film;

[0044] Figure 5 is a flowchart of a processing method of a humidity sensor with a heating and drying function according to the present invention.

[0045] The reference numerals in the figure are:

[0046] 10, humidity sensitive layer;

[0047] 20, liner layer; 21, first electrode comb structure; 22, first electrode right pad; 23, first electrode left pad;

[0048] 30, heat insulation film; 31, heating resistor; 32, resistor left pad; 33, resistor right pad; 34, second electrode comb structure; 35, second electrode left pad;

[0049] 40, water absorption layer;

[0050] 50, moisture conduction hole. Detailed implementation manners

[0051] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0052] Please refer to Figures 1-4, the present invention is a humidity sensor with a heating and drying function, including (but not limited to) the following four parts. The first part includes a humidity-sensitive layer 10. The second part includes a first electrode comb structure 21 (first interdigital electrode), a first electrode right pad 22, a first electrode left pad 23, a moisture-conducting hole 50, and a substrate layer 20. The third part includes a heat-insulating film 30, a heating resistor 31, a resistor left pad 32, a second electrode comb structure 34 (second interdigital electrode), a second electrode left pad 35, and a resistor right pad 33 (right pad of the second interdigital electrode). The fourth part includes a water-absorbing layer 40. The humidity sensor described in this embodiment includes the above four parts, but is not limited to the above four parts. Those skilled in the art can also introduce other features existing in existing sensors during actual production and application, such as an external housing structure, a support structure, a connected circuit structure, and other necessary structural features.

[0053] Please refer to Figures 1-4 , in one embodiment of the present invention, the first electrode comb structure 21, the first electrode right pad 22, the first electrode left pad 23, and the humidity-sensitive layer 10 are located on one side of the upper surface of the substrate layer 20. The heat-insulating film 30, the heating resistor 31, the resistor left pad 32, the resistor right pad 33, the second electrode comb structure 34, the second electrode left pad 35, and the water-absorbing layer 40 are located on one side of the lower surface of the substrate layer 20. The first interdigital electrode is in a comb shape on the surface of the substrate layer 20, and the humidity-sensitive layer 10 covers the first electrode comb structure 21, without covering the first electrode right pad 22 and the first electrode left pad 23. The heat-insulating film 30 is located on the lower surface of the substrate layer 20 with the same size as the substrate layer 20. The moisture-conducting hole 50 is located between the first electrode comb structures 21 and penetrates through the substrate layer 20, the humidity-sensitive layer 10, and the heat-insulating film 30. The heating resistor 31 is arranged in a serpentine shape around the moisture-conducting hole 50 on the heat-insulating film 30. The second interdigital electrode is in a comb shape on the lower surface of the heat-insulating film 30 (i.e., on the side of the heat-insulating film 30 away from the humidity-sensitive layer 10, on the same side as the heating resistor 31) and is connected to the heating resistor 31. The water-absorbing layer 40 covers the heating resistor 31 and the second interdigital electrode of the heating circuit, without covering the resistor left pad 32, the resistor right pad 33, and the second electrode left pad 35.

[0054] Please refer to Figures 1-4, in one embodiment of the present invention, the porous flexible humidity sensor with a heating and drying function provided in this embodiment has a simple structure, a relatively simple technical route for the manufacturing method, and a low processing difficulty. Among them, when the humidity sensor is working, the humidity-sensitive layer 10 adsorbs or releases water molecules. When the concentration of water molecules in the space changes, the number of water molecules adsorbed by the humidity-sensitive layer 10 also changes accordingly, causing a change in the dielectric constant of the humidity-sensitive layer 10, resulting in a change in the ability to impede the movement of charges. Therefore, the charge storage amount on the first interdigital electrode will change with the change in the amount of water molecules adsorbed by the humidity-sensitive layer 10, leading to a change in the final capacitance value. The first interdigital electrode is welded to the data acquisition device through pads, and humidity detection is performed by measuring the change in the capacitance value between the capacitance electrodes. Due to the structure of the moisture-conducting holes 50 penetrating through the humidity-sensitive layer 10, the substrate layer 20, and the heat-insulating film 30, and the water-absorbing layer 40 that can contact the end of the moisture-conducting hole 50 structure is provided, the accumulated water vapor can penetrate through the moisture-conducting holes 50 and be absorbed by the water-absorbing layer 40 in a timely manner. The water-absorbing layer 40 can absorb the water vapor accumulated on the surface of the humidity sensor, avoiding the influence of the excess accumulated water vapor on the performance of the humidity sensor. Among them, the second interdigital electrode is used to detect the humidity of the water-absorbing layer 40, and its detection process is the same as that of the first interdigital electrode. When the humidity of the water-absorbing layer 40 is detected to be high (or reaches a certain preset threshold) through the second interdigital electrode, the heating circuit is activated to dry the water-absorbing layer 40. When the heating circuit is working, a voltage is applied to the pads of the heating resistor 31 (the left pad 32 and the right pad 33 of the resistor). When the current passes through the serpentine heating resistor 31, the heating resistor 31 generates heat by itself, and the heat is transferred to the entire area of the water-absorbing layer 40 to heat the water-absorbing layer 40. Furthermore, the water-absorbing layer 40 is heated and dried through the heating resistor 31 of the heating circuit to ensure that the water-absorbing layer 40 can continuously absorb the water vapor accumulated on the surface of the humidity sensor, thereby improving the response speed and sensitivity of the sensor and ensuring that the humidity sensor is not easily affected by water vapor accumulation and cause performance degradation. At the same time, due to the heat-insulating film 30 being provided, it can effectively block the heat generated by the heating circuit from diffusing to the outside of the sensor, ensuring that the heat acts on the water-absorbing layer 40 directionally to achieve efficient drying, and at the same time avoiding the heating temperature from interfering with the detection accuracy of the humidity-sensitive layer 10.

[0055] Please refer to Figures 1-4 , in one embodiment of the present invention, the substrate layer 20 of the humidity sensor is selected as a flexible substrate. Specifically, the flexible substrate is selected from thermoplastic polymer materials, including but not limited to polyimide and polyethylene terephthalate, with a thickness of 20 - 250 μm. The substrate layer 20 has excellent mechanical flexibility, enabling the humidity sensor to adapt to various curved and deformed surfaces, and enabling the humidity sensor to have high measurement accuracy, short response time, high sensitivity, and good stability.

[0056] Please refer to Figures 1-4 , in one embodiment of the present invention, the first interdigital electrode is a comb-shaped conductive electrode (as shown in Figure 1 ), the electrode comb structure and the pad material are selected from gold, silver, copper or their alloys. The high conductivity of these materials reduces signal delay, is suitable for scenarios requiring rapid humidity response, and has good ductility. It can be prepared into a thin film electrode with a micron-level thickness through sputtering, electroplating or printing processes. The electrode line width is 10 - 100 μm and the thickness is 200 - 800 nm. The ratio range of the comb tooth spacing to the line width is 1:1 to 5:1. The larger electrode spacing is to provide sufficient space for the moisture conduction holes 50, increase the contact area between the water-absorbing material and the moisture conduction holes 50, and thus improve the water absorption efficiency of the water-absorbing material.

[0057] Please refer to Figures 1-4 , in one embodiment of the present invention, the material used for the humidity-sensitive layer 10 is a polymer matrix and two-dimensional nanomaterials and their composites. The humidity-sensitive material dispersion is coated on the surface of the first interdigital electrode and dried in a vacuum or inert gas environment to form the humidity-sensitive layer 10. The polymer provides flexibility and film-forming properties. Two-dimensional materials (such as h-BN, MoS2) significantly improve the humidity response sensitivity, stability and dynamic range through high specific surface area and interface synergistic effects. The above are only examples, and the humidity-sensitive layer 10 can also use other optional materials in existing humidity sensors, which are not limited here.

[0058] Please refer to Figures 1-4 , in one embodiment of the present invention, the diameter of the moisture conduction holes 50 penetrating through the heat insulation film 30, the substrate layer 20 and the humidity-sensitive layer 10 (the moisture conduction holes on the humidity-sensitive layer 10 are not shown in the figure) is 10 - 500 μm, and they are arranged periodically. As one preferred example, its arrangement structure is as shown in the attached drawing. However, it is only a specific example of the arrangement structure of the moisture conduction holes 50, and other arrangement methods can also be selected, which are not limited here.

[0059] Please refer to Figures 1-4, in one embodiment of the present invention, the heat insulation film 30 is made of a flexible dielectric material with a thermal conductivity ≤ 0.5 W / (m·K), including but not limited to polyether ether ketone or ceramic-filled polymer composite materials. It combines low thermal conductivity and flexible adaptability. The low thermal conductivity can effectively block the heat generated by the heating circuit from diffusing outside the sensor, ensuring that the heat acts directionally on the water absorption layer 40 to achieve efficient drying, while avoiding temperature interference with the detection accuracy of the humidity-sensitive layer 10. Its preparation process is relatively mature, and a uniform and dense film can be prepared by methods such as the sol-gel method. Moreover, the thickness and pore structure of the film can be adjusted to meet the heat insulation requirements of different sensors. The moisture-conducting holes 50 on the heat insulation film 30 penetrate through the heat insulation film 30, the substrate layer 20, and the humidity-sensitive layer 10 at the same time, and the moisture-conducting holes 50 are arranged orderly between the first interdigital electrodes. The moisture-conducting holes 50 are drilled by laser drilling technology, which has the advantages of generating smaller pore diameters, avoiding material cracking, being non-contact and non-abrasive, and adjusting the pore size and position through software.

[0060] Please refer to Figures 1-4 , in one embodiment of the present invention, the heating circuit is arranged on the heat insulation film 30 and is serpentinely wound around the moisture-conducting holes 50 on the heat insulation film 30, which can enable the heating circuit to contact the water-absorbing material to the greatest extent and increase the drying efficiency of the water absorption layer 40. A resistance pad (resistance left pad 32, resistance right pad 33) is respectively connected to both ends of the heating circuit for input and output, so that the heating circuit forms a loop to energize and heat the heating resistor 31. The pads of the heating circuit are located in the non-working area at the edge of the heat insulation film 30, which is more conducive to leading out leads from the pads for resistance measurement. Among them, the heating resistor 31 and the resistance pads are both made of metal materials, with a line width of 20 - 200 μm and an adjacent trace spacing of 1 - 5 times the line width, and a thickness of 200 - 800 nm. The surrounding degree of the heating resistor 31 around the periphery of the moisture-conducting hole 50 can be 90% etc., and can also be adjusted according to the actual situation.

[0061] Please refer to Figures 1-4 , in one embodiment of the present invention, the second interdigital electrode is a comb-shaped conductive electrode, and the materials of the second electrode comb-shaped structure 34 and the second interdigital electrode pad are metal, alloy or composite conductive laminated materials, with a thickness of 200 - 800 nm. Among them, the right fork-shaped electrode of the second interdigital electrode is electrically connected to the heating circuit, and the right pad of the second interdigital electrode can share a pad position with the right pad of the heating resistor 31, so as to achieve circuit integration, save space to a greater extent, and avoid the heating circuit and the second interdigital electrode being too close to affect the performance.

[0062] Please refer to Figures 1-4In one embodiment of the present invention, the material used for the water absorption layer 40 is composed of a high temperature resistant hygroscopic polymer material with a thickness of 100μm-200μm. It can not only efficiently absorb and lock moisture through hydrophilic groups, but also maintain chemical stability and structural integrity during the heating and drying process (such as 40-120°C), avoiding thermal degradation or deformation, thereby ensuring the recycling ability and long-term reliability of the sensor. The water absorption layer 40 is coated on the surface of the thermal insulation film 30, the heating circuit and the second interdigital electrode through a conformal covering process, and forms a close contact with the end of the moisture-conducting hole 50 (the surface of the thermal insulation film 30), so that the water absorption layer 40 can absorb moisture more effectively and be dried by the heating circuit in time. However, the water absorption layer 40 avoids the pad area to ensure circuit conductivity.

[0063] like Figure 5 As shown, an embodiment of the present invention further provides a method for processing the humidity sensor with heating and drying function as described above, comprising the following steps:

[0064] S1. Forming first interdigital electrodes on the upper surface of the substrate layer 20 by photolithography or laser patterning.

[0065] Specifically, first, the photoresist is evenly spin-coated on the surface of the substrate layer 20 and pre-baked. The mask plate of the lower electrode of the capacitor is selected for exposure, moved to the developer for development, and then post-baked after rinsing with deionized water. Then, the metal layer is immediately sputtered by sputtering, printing or electroplating process, and the thickness is 200-800nm. Finally, the substrate layer 20 plated with the electrode metal layer is immersed in an acetone solution, and the photoresist is ultrasonically dissolved until the metal pattern is clear, and the photolithography stripping of the first electrode comb structure 21 and the first interdigitated electrode pad is completed.

[0066] S2 , coating the humidity sensitive material dispersion on the surface of the first interdigital electrode, and drying in a vacuum or inert gas environment to form the humidity sensitive layer 10 .

[0067] Specifically, hexagonal boron nitride nanosheets and polyvinyl pyrrolidone are mixed in a mass ratio of 1:9 to 1:19 (preferably 1:9), dissolved in anhydrous ethanol to prepare a dispersion, and uniformly dispersed by magnetic stirring and ultrasonic crushing. A microinjection pump is used to drop the dispersion onto the surface of the first interdigitated electrode at a rate of 0.1 to 0.3 ml / min, and then a humidity sensitive film is formed by a spin coating process. The coated device is placed in a vacuum drying oven or a nitrogen protection environment, and dried at a gradient temperature of 40 to 80 ° C for 1 to 3 hours, finally forming a porosity of 70% to 90% and a specific surface area of ​​≥ 200m 2The porous humidity-sensitive layer 10 of / g. Characterized by scanning electron microscopy, h-BN nanosheets are uniformly embedded in the PVP matrix to form a three-dimensional interconnected porous network. Electrical tests show that the sensitivity of this sensitive layer reaches 0.5 - 1.2 pF / %RH in the range of 30% - 90% RH, the response time (T 90 ) ≤ 10 s, and the capacitance drift ≤ 3% after 100 moisture absorption-drying cycles, which is significantly better than that of the pure PVP sensitive layer.

[0068] S3. A heat insulation film 30 of the same size is fabricated on the lower surface of the substrate layer 20 by spin coating, spraying or hot pressing processes.

[0069] Specifically, a silica (SiO2) mesoporous film is uniformly coated on the lower surface of the substrate layer 20 using a spin coater to ensure a uniform coating. The coated substrate layer 20 is placed in an oven for drying to remove the solvent. It is dried at a temperature of 100 - 150 °C for 30 minutes. It is cured at a temperature of 50 - 80 °C for 12 hours.

[0070] S4. Holes are punched between the first interdigital electrodes by laser processing, ion etching or mechanical punching processes to form an array of moisture-conducting holes 50 that penetrate through the substrate layer 20, the heat insulation film 30 and the humidity-sensitive layer 10.

[0071] Specifically, according to the thickness of the material and the required diameter of the moisture-conducting holes 50, the parameters of laser drilling are set. A laser device is used to drill holes in the exposed area to form orderly arranged moisture-conducting holes 50. Ensure that the moisture-conducting holes 50 penetrate through the substrate layer 20, the heat insulation film 30 and the humidity-sensitive layer 10 simultaneously.

[0072] S5. A heating circuit and a second interdigital electrode are formed on the surface of the heat insulation film 30 by sputtering, printing or electroplating processes. The heating resistor 31 surrounds the moisture-conducting holes 50. The second interdigital electrode is formed on the surface of the heat insulation film 30 by photolithography or laser patterning processes. The second interdigital electrode and the heating circuit are connected by coplanar wiring and share the same right pad.

[0073] Specifically, a layer of photoresist is uniformly coated on the surface of the heat insulation film 30. The photoresist is exposed using a photolithography machine and a mask template to form the patterns of the heating circuit and the second interdigital electrode. The exposed photoresist is placed in a developer for development to remove the unexposed photoresist, exposing the area to be etched. An etching machine is used to etch the exposed heat insulation film 30 to form the patterns of the heating resistor 31 and the second interdigital electrode. A stripping solution is used to remove the remaining photoresist to ensure the surfaces of the heating resistor 31 and the second interdigital electrode are clean. The sensor is washed again to ensure there are no residues on the surface. The sensor is placed in an oven for drying to remove moisture.

[0074] S6. A water-absorbing layer 40 is formed on the surface of the heat-insulating film 30, the heating circuit and the second interdigital electrode through an impregnation, inkjet printing or vapor deposition process, and selective coverage is achieved in the pad area through a masking or laser removal process.

[0075] Specifically, a high-temperature resistant and highly water-absorbent resin is selected as the water-absorbing material. A cross-linking agent and an initiator are added to the neutralization reaction product of acrylic acid and alkali solution for cross-linking reaction, and the gel polymer obtained from the cross-linking reaction is granulated to obtain resin particles; then the resin particles are subjected to surface spraying treatment with a surfactant to prepare a highly water-absorbent resin. The prepared highly water-absorbent resin particles are dispersed in a suitable solvent, such as N-methylpyrrolidone (NMP) or deionized water, to prepare a uniform dispersion. The surfaces of the heat-insulating film 30, the heating circuit and the second interdigital electrode are ultrasonically washed in sequence with dishwashing liquid, deionized water, acetone and alcohol and then dried. The dispersion is dropped on the substrate, and then evenly distributed by natural drying or slight heating. The coated substrate is placed at a temperature of 50-80 °C and dried for 12 hours to remove the solvent and cure the water-absorbing layer 40.

[0076] The above has described in detail an embodiment of the present invention, but the content described is only a preferred embodiment of the present invention and cannot be considered as limiting the implementation scope of the present invention. All equivalent changes and improvements made according to the application scope of the present invention should still fall within the scope covered by the claims of the present invention.

[0077] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present invention is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0078] In the description of the present invention, unless otherwise clearly specified and defined, the first feature being "above" or "below" the second feature may include direct contact between the first and second features, or may include contact between the first and second features not being direct but through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the horizontal height of the first feature is less than that of the second feature.

[0079] In the description of the present invention, it should also be noted that, unless otherwise clearly specified and defined, the terms "arranged" and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention may be understood according to specific circumstances.

Claims

1. A humidity sensor with a heating and drying function, characterized in that, Comprising: A substrate layer; A first interdigital electrode, which is fixedly arranged on one side of the substrate layer, and the first comb-shaped structure of the first interdigital electrode is connected to a data acquisition device through a pad; A humidity-sensitive layer, which is fixedly attached to the substrate layer and is located outside the first interdigital electrode, covering the area where the first comb-shaped structure is located; A heat-insulating film, which is located on the side of the substrate layer away from the humidity-sensitive layer and is fixedly attached to the substrate layer conformally; A heating circuit, which is fixedly arranged on the side of the heat-insulating film away from the substrate layer, including a heating resistor and a pad for connecting to a power supply; An absorbent layer, which is fixedly attached to the heat-insulating film and is located outside the heating resistor; Wherein, a plurality of moisture-conducting holes are formed through the humidity-sensitive layer, the substrate layer and the heat-insulating film, and the heating resistor is arranged around the moisture-conducting holes.

2. The humidity sensor with a heating and drying function according to claim 1, characterized in that, A second interdigital electrode is further arranged on the heat-insulating film, and the second interdigital electrode is used to detect the humidity data of the absorbent layer.

3. The humidity sensor with a heating and drying function according to claim 1, wherein The substrate layer is a thermoplastic polymer material with a thickness of 20 - 250 μm.

4. A humidity sensor with a heating and drying function according to claim 1, characterized in that, The first comb-shaped structure of the first interdigital electrode comprises 10 - 50 pairs of comb-tooth structures arranged alternately, the electrode line width is 10 - 100 μm and the thickness is 200 - 800 nm, and the ratio of the comb-tooth pitch to the line width ranges from 1:1 to 5:

1.

5. A humidity sensor with a heating and drying function according to claim 1, characterized in that, The heat-insulating film is made of a flexible dielectric material with a thermal conductivity ≤ 0.5 W / (m·K).

6. The humidity sensor with a heating and drying function according to claim 1, characterized in that, The diameter of the moisture-conducting holes is 10 - 500 μm, and the moisture-conducting holes are arranged staggeredly with the comb teeth of the first interdigital electrode. Among them, the ratio of the adjacent micropore spacing to the pore diameter is 2:1 to 10:

1.

7. The humidity sensor with a heating and drying function according to claim 1, characterized in that, The heating circuit is made of a metal material and is integrated on the surface of the heat-insulating film in a serpentine structure. The line width of the heating circuit is 20 - 200 μm, the adjacent trace spacing is 1 - 5 times the line width, and the thickness is 200 - 800 nm; the heating resistor traces of the heating circuit are arranged to bypass the moisture-conducting holes, and each serpentine loop covers 5 - 15 micropores.

8. The humidity sensor with a heating and drying function according to claim 1, characterized in that, The absorbent layer is composed of a hygroscopic polymer material, with a heat resistance ≥ 100 °C and a moisture absorption rate ≥ 500%.

9. The humidity sensor with a heating and drying function according to claim 1, characterized in that, The absorbent layer is coated on the surfaces of the heat-insulating film, the heating circuit and the second interdigital electrode through a conformal coating process and is in close contact with the moisture-conducting holes.

10. A processing method of a humidity sensor with a heating and drying function, characterized in that, Including the following steps: S1. Substrate layer treatment: A first interdigital electrode is formed on the upper surface of the substrate layer through a photolithography or laser patterning process, and the electrode material is a metal or a composite conductive film; S2. Humidity-sensitive layer preparation: A humidity-sensitive material dispersion liquid containing a polymer matrix and a nano-dopant is coated on the surface of the first interdigital electrode, and after drying treatment, a humidity-sensitive layer is formed. The drying conditions are a vacuum or an inert gas environment, a temperature of 40 - 80 °C, and a time of 0.5 - 2 h; S3. Heat-insulating film integration: A heat-insulating film is formed on the lower surface of the substrate layer through a spin coating, spraying or hot pressing process, with a thermal conductivity ≤ 0.1 W / (m·K) and a thickness of 10 - 100 μm; S4. Moisture-conducting hole machining: By using laser machining, ion etching or mechanical punching process, a microporous array penetrating the substrate layer, the heat insulation film and the humidity-sensitive layer is formed between the teeth of the first interdigital electrode, with a pore diameter of 5 - 200 μm and a pore density of 100 - 1000 holes / cm 2 ; S5. Heating circuit and second interdigital electrode fabrication: A heating circuit and a second interdigital electrode are simultaneously formed on the surface of the heat-insulating film through a sputtering, printing or electroplating process, where: The heating circuit is a spiral or grid-shaped resistive structure, and the resistive material is nickel-chromium alloy, platinum, or doped oxide semiconductor; The right fork-shaped electrode of the second interdigital electrode is connected to the heating circuit through coplanar wiring and shares the same pad; S6. Water-absorbing layer encapsulation: A water-absorbing layer is formed on the surfaces of the thermal insulation film, heating circuit, and second interdigital electrode through impregnation, inkjet printing, or vapor deposition processes, and selective coverage is achieved in the pad area through a masking or laser removal process.

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