Preparation process of resistance type humidity sensor with quick response and high sensitivity

Abstract

A preparation process of a resistance type humidity sensor with quick response and high sensitivity is characterized in that a mixed dispersion liquid of tungsten disulfide and graphene oxide quantum dots is used as a humidity sensitive film, and optimal response recovery time and high sensitivity are obtained by controlling the volume ratio of the tungsten disulfide to the graphene oxide quantum dots. The sensitive material is connected with the interdigital electrode on the substrate, when the external humidity condition changes, the sensitive material can generate corresponding resistance change, and the change of the external humidity can be correspondingly detected by detecting the corresponding resistance change. The preparation technology is simple, and unattended operation can be achieved in the preparation process; in addition, the electrode preparation method can be widely applied to substrates of various different materials, including flexible and hard substrates; and meanwhile, the integration technology is rapid, simple and convenient, is compatible with a traditional humidity sensor preparation process, is relatively high in yield and yield, and has potential to realize planning manufacturing.

Description

Technical Field

[0001] The present invention relates to the fields of two-dimensional materials, quantum dots and sensors, and in particular to a fast-response and highly sensitive quantum dot and two-dimensional material composite thin film resistance humidity sensor and a preparation process. Background Art

[0002] Humidity sensors can measure the water vapor content in the air and are widely used in many fields such as industrial production, health care, environmental monitoring, aerospace, etc. Flexible humidity sensors can be attached to the surface of the skin for humidity sensing and respiratory monitoring, and have the advantages of flexible stretching, foldable and portable, good stability, and high sensitivity.

[0003] The existing types of humidity sensors mainly include resistive, capacitive, piezoresistive, etc. With the development of the Internet and artificial intelligence in my country, sensors, as the most advanced signal acquisition part in robots, have always been the most important research direction. Most of the existing humidity sensors are difficult to have the characteristics of fast response and high sensitivity at the same time, and there are problems such as complex preparation process and poor stability. Therefore, it is of great significance to study and prepare a flexible humidity sensor with simple process, high sensitivity and fast response.

[0004] Two-dimensional materials are materials in which electrons can move freely (planar motion) only in two dimensions at the nanoscale (1-100nm). Their electronic and thermal motion mainly occurs in one plane, thus exhibiting unique physical and chemical properties. These materials usually have high surface area, excellent mechanical strength, high electron mobility and special optical properties. Due to their limited dimensions, two-dimensional materials exhibit quantum confinement effects, which lead to significant differences in their electrical, optical and thermal properties from traditional three-dimensional materials. These properties make two-dimensional materials have broad application potential in nanoelectronics, optoelectronics, energy storage, catalysis and biomedical engineering. Due to their ultra-thin thickness and excellent and unique mechanical and electrical properties, two-dimensional materials are very suitable for use as sensitive films in ultra-small-scale nanoelectromechanical sensors. Compared with traditional sensitive films, two-dimensional materials have higher sensitivity and can maintain stable detection performance under extreme environments such as ultra-low pressure, high temperature or low temperature. They have a wide range of applications, including but not limited to pressure sensors, accelerometers, humidity sensors, carbon dioxide gas sensors, resonators and microphones.

[0005] However, the current preparation process for two-dimensional materials and their devices is relatively complicated, and there are problems such as low production rate and poor yield, which makes it impossible to carry out large-scale standardized production. It is difficult for a single two-dimensional material to simultaneously meet multiple different performance requirements, such as fast response and high sensitivity, and unprocessed two-dimensional materials may have poor repeatability and stability.

[0006] As a two-dimensional material, tungsten disulfide has high electron mobility and current switching rate. At the same time, due to its abundant surface active sites, it has good response performance to humidity. However, the repeatability of untreated pure molybdenum disulfide to humidity response is poor. This is because pure tungsten disulfide easily reaches saturation in a rapidly changing humidity environment.

[0007] Graphene oxide quantum dots are a material based on graphene oxide with a size of about 10nm. They have a high specific surface area and a large number of oxygen-containing groups, which can improve the humidity sensing properties of two-dimensional materials. However, the humidity sensor made of pure graphene oxide has a high resistance, which may be related to the poor conductivity of graphene oxide quantum dots.

[0008] In the existing technology, most of the improvements of sensitive materials are made by introducing graphene derivatives into two-dimensional materials. Jha et al. (JHA RK, BURMAN D, SANTRA S, et al. WS2 / GO Nanohybrids for EnhancedRelative Humidity Sensing at RoomTemperature[J]. IEEE Sensors Journal, 2017,17(22): 7340–7347.) developed a WS2 / GO Nanohybrid for EnhancedRelative Humidity Sensing at RoomTemperature[J]. IEEE Sensors Journal, 2017,17(22): 7340–7347.) 2 The high-sensitivity resistive humidity sensor based on the GO / GO composite film is shown in Figure 1. GO has more defect sites and oxygen-rich groups, which can enhance the performance of the humidity sensor. Its response time is 25s and its recovery time is 29s in a 60% relative humidity environment.

[0009] However, sensors made in this way have long response time and recovery time, which makes it difficult to meet the needs of rapid humidity detection.

[0010] Zhang et al. (ZHANG L, TAN Q, WANG Y, et al. Wirelessly powered multi-functional wearable humidity sensor based on RGO-WS 2 heterojunctions[J].Sensors and Actuators B: Chemical, 2021, 329: 129077.) proposed a humidity sensor based on reduced graphene oxide (RGO) and tungsten disulfide heterojunctions, but its stability was poor.

[0011] Patent application number 2024104436051 entitled "A fast-response and high-sensitivity resistive humidity sensor and its preparation method" discloses a resistive humidity sensor based on graphene oxide and molybdenum disulfide composite film. The sensitivity is as low as 98%, but it still cannot meet the requirements of high-precision measurement.

[0012] Therefore, it is necessary to design a new humidity sensor that can take into account the performance of fast response and high sensitivity to meet higher requirements. Summary of the invention

[0013] The purpose of the present invention is to overcome the defects of the prior art and provide a humidity sensor with fast response, high sensitivity and simple process.

[0014] The present invention provides a preparation process of a fast-response and high-sensitivity resistive humidity sensor, which is characterized in that a mixed dispersion of tungsten disulfide and graphene oxide quantum dots is used as a humidity-sensitive film, and the optimal response recovery time and high sensitivity are obtained by controlling the volume ratio of tungsten disulfide and graphene oxide quantum dots. The sensitive material is connected to the interdigital electrodes on the substrate, and when the external humidity conditions change (such as humidity increases), the sensitive material will undergo a corresponding resistance change (such as resistance decreases), and the change in external humidity can be detected by detecting the corresponding resistance change.

[0015] Furthermore, the sensitive material includes molybdenum disulfide (MoS 2 ), graphene and its derivatives, molybdenum diselenide (MoSe 2 ), hexagonal boron nitride (h-BN), tungsten diselenide (WSe 2 ), tungsten disulfide (WS 2 ), platinum diselenide (PtSe 2 )、Molybdenum ditelluride(MoTe 2 ), tungsten ditelluride (WTe 2 )、vanadium diselenide(VSe 2 ), chromium disulfide (CrS 2 ), chromium diselenide (CrSe 2 ), transition metal dichalcogenides (TMDC), black phosphorus (P), MXene, and quantum dot materials such as graphene quantum dots, graphene oxide quantum dots, reduced graphene quantum dots, boron nitride quantum dots, silicon quantum dots, carbon quantum dots, sulfur quantum dots, C 3 N quantum dots, phosphorus quantum dots, transition metal dichalcogenide quantum dots (such as tungsten disulfide quantum dots, molybdenum disulfide quantum dots, molybdenum selenide quantum dots, tungsten selenide quantum dots, titanium disulfide quantum dots, tantalum disulfide quantum dots, zirconium disulfide quantum dots, ternary alloy TMDCs quantum dots, etc.).

[0016] Furthermore, the substrate of the interdigital electrode includes an oxide substrate, a PET / PI flexible substrate, a silicon substrate, an SOI substrate, and a carbon material substrate.

[0017] Furthermore, the interdigital electrode material includes gold, silver, copper, aluminum, titanium and a composite thereof.

[0018] Furthermore, the number of the interdigital pairs of the interdigital electrodes may be one to ten pairs.

[0019] Furthermore, the sensitive material may be located between the electrode and the substrate, or may be located above the electrode and the substrate.

[0020] Furthermore, the sensitive material may be integrated by a drip coating method or a spraying method.

[0021] Furthermore, the number of the humidity sensors includes one, several or more, such as several humidity sensors connected in series or in parallel. The humidity sensor includes the integration of its sensitive structure and interface test circuit board, and also includes the sensitive structure of the humidity sensor and high-performance interface circuit (such as ASIC or CMOS).

[0022] The beneficial effects of the present invention are: 1. Compared with the traditional method, the preparation process of the sensitive material of the present invention is simple, and the preparation process can be unattended; and the electrode preparation method of the present invention can be generally applied to substrates of various materials, including flexible and hard substrates; at the same time, the integration technology of the present invention is fast and simple, compatible with the traditional humidity sensor preparation process, with high yield and high yield, and has the potential to realize planned manufacturing; 2. The sensitive materials that can be prepared include not only tungsten disulfide and graphene oxide quantum dots, but also other two-dimensional materials that are sensitive to humidity, such as MXene, graphene, tungsten diselenide and other transition metal dichalcogenides (TMDC) and other quantum dot solutions, which can reflect the universality of this preparation process and improve the sensitivity and response performance of resistive sensors; 3. The humidity sensor of the present invention has a wide range of applications. Thanks to its high sensitivity, fast response and recovery time, and wide humidity detection range, it can be used in many different fields such as military, commercial, civilian, and scientific exploration. 4. The cost of the sensitive material described in the present invention is extremely low. Calculated based on the usage of 0.05mL / cm² of sensitive material, the usage of a single humidity sensor (based on a sensitive area of ​​1cm²) is only 0.05mL of sensitive material; 5. The introduction of graphene oxide quantum dots as the sensing layer can greatly improve the performance of humidity sensors made of pure two-dimensional materials. For example, pure tungsten disulfide humidity sensors have poor stability and repeatability, low sensitivity, slow response / recovery time, and the resistance change curve is accompanied by spikes, so they do not have good humidity sensing performance. However, after adding graphene oxide quantum dots, the sensitivity is greatly improved to 99.57%, and the response / recovery time is also greatly reduced. The response time is 25 times faster than before, and the recovery time is 4 times faster than before. Therefore, mixing and dispersing tungsten disulfide and graphene oxide quantum dots can significantly improve the sensitivity, response recovery performance and repeatability of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. The drawings described in the following part are only some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained based on these drawings without creative work.

[0024] Figure 1 A top view of a humidity sensor provided by an embodiment of the present invention; Figure 2 A three-dimensional exploded view of a humidity sensor provided by an embodiment of the present invention; Figure 3 The process flow chart of interdigital electrode preparation is shown in FIG. Figure 4 This is a process flow chart for the preparation of resistive sensors.

[0025] Where (1) represents the substrate, (2) represents the interdigitated electrodes, and (3) represents the sensitive material.

[0026] Examples of specific steps that can be implemented: The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiment is only one embodiment of the present invention rather than all embodiments. Based on this embodiment, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0027] like Figure 3 The interdigital electrodes used in the embodiment of the present invention are defined by a custom patterned screen template to define the number of pairs and area size of the interdigital electrodes. After the screen template is pressed on the insulating substrate, a conductive material (such as silver paste) is dripped on the screen template, and the conductive material is evenly scraped on the substrate using a scraper. Then, the interdigital electrodes in a slurry state and the substrate are transferred to a heating table together, and heated at 120°C for 20 minutes to achieve complete curing.

[0028] like Figure 4 The sensitive material used in the embodiment of the present invention is a mixture of tungsten disulfide and graphene oxide quantum dots in a volume ratio of 1:3. The dispersion of the sensitive material is prepared by ultrasonication with a cell crusher at a power of 10W for 10 minutes. The substrate and the interdigital electrode are placed on a heating table, and 0.05 mL of the prepared sensitive material is evenly dripped on the interdigital area of ​​the interdigital electrode by drip coating, and heated at 95°C until the sensitive material is completely evaporated. The humidity sensor with a dry surface is removed from the heating table and naturally cooled to room temperature to complete the preparation of the humidity sensor.

[0029] The embodiment produced by the preparation process described in the present invention has a response time and a recovery time of 1.55 seconds and 41.1 seconds respectively, and has high sensitivity (sensitivity of 99.57% at relative humidity of 11% to 98%). At the same time, the preparation process is simple, the cost is low, and it has the potential for large-scale production.

[0030] The above shows and describes the basic principles, main features and advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0031] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A preparation process of a fast-response and high-sensitivity resistive humidity sensor, wherein the humidity sensor comprises a humidity sensor sensitive structure based on a sensitive film and an integrated high-performance interface circuit. The process flow of the humidity sensor requires the preparation of a sensitive film and an interdigital electrode respectively, and finally the humidity sensor is made. The interdigital electrode is defined by a custom patterned screen template, and the number and area of ​​the interdigital electrodes are defined. A scraper is used to evenly scrape the conductive material on the substrate, and the substrate is heated at 120°C for 20 minutes on a heating table and then cured. The process flow of the humidity sensor comprises: The sensitive film is a mixture of two-dimensional material and quantum dot solution, and is prepared by the following steps: S1. Mixing a graphene oxide quantum dot solution and a tungsten disulfide solution of the same mass concentration in a volume ratio of 1:3 to prepare a mixed solution; S2, sonicate the mixed solution with a cell crusher at 30W for 10 minutes; Finally, the mixed solution is coated on the prepared interdigital electrodes and heated at 95° C. until the water is completely evaporated to obtain the resistive humidity sensor.

2. The process for preparing a fast-response and high-sensitivity resistive humidity sensor according to claim 1, characterized in that: The sensitive film is prepared in step S2 by ultrasonic dispersion at a constant temperature of 35° C. for 60 minutes.

3. The process for preparing a fast-response and high-sensitivity resistive humidity sensor according to claim 1, characterized in that The two-dimensional materials of the sensitive film include molybdenum disulfide (MoS2), graphene and its derivatives, molybdenum diselenide (MoSe2), hexagonal boron nitride (h-BN), tungsten diselenide (WSe2), tungsten disulfide (WS2), platinum diselenide (PtSe2), molybdenum ditelluride (MoTe2), tungsten ditelluride (WTe2), vanadium diselenide (VSe2), chromium disulfide (CrS2), chromium diselenide (CrSe2), transition metal dichalcogenides (TMDC), black phosphorus (P), and MXene.

4. The process for preparing a fast-response and high-sensitivity resistive humidity sensor according to claim 3, characterized in that The quantum dot solution material of the sensitive film includes graphene quantum dots, graphene oxide quantum dots, reduced graphene quantum dots, boron nitride quantum dots, silicon quantum dots, carbon quantum dots, sulfur quantum dots, C3N quantum dots, phosphorus quantum dots, and transition metal dichalcogenide quantum dots.

5. The process for preparing a fast-response and high-sensitivity resistive humidity sensor according to claim 4, characterized in that The transition metal dichalcogenide quantum dots include tungsten disulfide quantum dots, molybdenum disulfide quantum dots, molybdenum selenide quantum dots, tungsten selenide quantum dots, titanium disulfide quantum dots, tantalum disulfide quantum dots, zirconium disulfide quantum dots, and ternary alloy TMDCs quantum dots.

6. The process for preparing a fast-response and high-sensitivity resistive humidity sensor according to claim 1, characterized in that The electrode materials of the humidity sensor include gold, silver, copper, aluminum, titanium and composites thereof; the substrates of the interdigitated electrodes include oxide substrates, PET / PI flexible substrates, silicon substrates, SOI substrates and carbon material substrates.

7. The process for preparing a fast-response and high-sensitivity resistance-type humidity sensor according to claim 1, characterized in that The interdigital electrode has at least one pair of interdigital pairs; the sensitive film material may be located between the electrode and the substrate, or may be located above the electrode and the substrate; the sensitive material of the humidity sensor may be integrated by a drop coating method or a spraying method.

8. A fast-response and high-sensitivity resistance-type humidity sensor according to claim 1, characterized in that The number of the humidity sensor is at least one, and multiple sensor functional structures can be connected in series or in parallel.

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