Flexible humidity sensor based on graphene oxide-high-molecular polymer-titanium carbide compound and preparation method of flexible humidity sensor

Abstract

The invention discloses a flexible humidity sensor based on a graphene oxide-high-molecular polymer-titanium carbide compound and a preparation method thereof, and belongs to the technical field of flexible sensors, and the preparation method comprises the following steps: 1) directly engraving on a polyimide PI flexible substrate by using laser to form a laser-induced graphene interdigital electrode; (2) preparing a GO / PEDOT: PSS / Ti < 3 > C < 2 > TX humidity-sensitive material prepared from graphene oxide, poly (3, 4-ethylenedioxythiophene): polystyrene sulfonate and titanium carbide; 3) coating a humidity-sensitive material on a graphene electrode to complete manufacturing of the flexible humidity sensor, the sensor has excellent flexibility, so that the sensor can be easily attached to irregular surfaces such as a mask or human skin, and the sensor shows fast response / recovery time and a wide linear detection range, so that the flexible humidity sensor can be widely applied to the field of humidity sensors. And stable capacitance and resistance response and high sensitivity are realized. The sensor not only can effectively detect the breathing condition of a human body, but also can carry out finger non-contact interaction test, and is widely applied to the fields of human health monitoring and non-contact man-machine interaction.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible sensors, and in particular relates to a flexible humidity sensor based on a graphene oxide-high molecular polymer-titanium carbide composite and a preparation method thereof. Background Art

[0002] Skin-like electronics that mimic the properties of human skin are rapidly emerging as a key technology in healthcare monitoring, human-machine interfaces, and intelligent robotics. With their flexibility and conformability, these devices can perfectly fit the human body or complex curved surfaces, achieving accurate perception of their own state and surrounding environment. Among them, flexible humidity sensors play a key role in promoting health, ensuring safety, and improving social productivity due to their non-contact sensing capabilities. Flexible humidity sensors detect changes in moisture caused by skin, fingers, sweat, and even breath, and can obtain information without physical contact. It is particularly noteworthy that as the demand for contactless operation grows, the development of this field is crucial to building a safer and more reliable social system.

[0003] According to the working mechanism, the current sensors are mainly divided into four types of humidity sensors: resistive, capacitive, impedance and voltage. The working mechanism of most flexible humidity sensors can be explained by the Grotthuss chain reaction, which is usually simplified as a proton hopping process. It usually refers to the dynamic charge transfer process between active materials under a certain relative humidity (RH). Since the signal intensity of the humidity sensor reflects the number of water molecules on the surface of the sensing material, the hydrophilicity of the active material plays a vital role in the sensing performance.

[0004] Commonly used sensitive materials include metal oxides, polymers, and carbon-based materials. In particular, in the field of flexible humidity sensors, PEDOT:PSS is widely used due to its flexibility, stretchability, and skin affinity; graphene and its derivatives (such as graphene oxide (GO) and reduced graphene oxide (rGO)) are also of great interest due to their large surface area, low toxicity, and mechanical compliance; in addition, titanium carbide (Ti3C2T X ) Due to its oxidation resistance and high melting point, it can still maintain good stability in high temperature or high humidity environment, thus improving the service life and reliability of the sensor.

[0005] Although the above materials and technologies have achieved remarkable achievements, they still face many challenges in practical applications. For example, problems such as complex preparation process, limited effective measurement range, poor bending performance, and long response / recovery time limit the application scope and performance of traditional humidity sensors. The present invention aims to overcome the limitations of the existing technology by introducing innovative designs and technical means to provide a more efficient, stable and adaptable flexible humidity sensor solution. Specifically, the present invention solves the following problems: (1) fast and efficient technology for manufacturing humidity-sensitive materials; (2) expanding the effective humidity measurement range; (3) improving the bending performance of the sensor to adapt to complex curved surfaces; (4) reducing hysteresis and accelerating response / recovery time; (5) ensuring long-term stable humidity detection performance.

[0006] In summary, the new flexible humidity sensor provided by the present invention not only solves the problems existing in the prior art, but also further improves the practicality and reliability of the equipment, laying a solid foundation for the development of more innovative skin-like electronic products in the future. Summary of the invention

[0007] The present invention aims to simplify the manufacturing process and proposes an innovative solution to the problems of traditional humidity sensors, such as narrow linear range, inability to adapt to complex surfaces, slow response speed, poor stability, etc. Specifically, the present invention designs a flexible humidity sensor based on graphene oxide-polymer-titanium carbide composite. The sensor not only has a streamlined manufacturing process, but also has a wide detection range for humidity, and also has a short response / recovery time, excellent repetitive stability and good anti-interference. This makes the humidity sensor have broad application prospects in the fields of humidity detection, respiratory monitoring and non-contact human-computer interaction.

[0008] To achieve the above object, the technical scheme of the present invention is as follows: a flexible humidity sensor based on graphene oxide-polymer-titanium carbide composite, comprising a flexible substrate, graphene interdigital electrodes laser engraved on the substrate, and a humidity sensitive coating coated on the graphene electrodes, wherein the humidity sensitive coating is composed of GO / PEDOT:PSS / Ti3C2T X It is composed of (graphene oxide / polymer / titanium carbide) humidity-sensitive materials, and the flexible substrate is polyimide PI.

[0009] Preferably, the graphene electrode is a laser induced graphene LIG interdigitated electrode engraved on a PI film by laser direct writing technology.

[0010] Preferably, a method for preparing a flexible humidity sensor based on graphene oxide-polymer-titanium carbide composite comprises the following steps: Step 1, preparing LIG interdigital electrodes, including: fixing a flexible PI film on a substrate; importing a designed electrode pattern into an operating software, and setting engraving parameters of a laser direct writing system to laser-induce engraving of LIG interdigital electrodes; Step 2: preparing a humidity-sensitive material, including: mixing graphene oxide GO and titanium carbide Ti3C2T X The dispersion was uniformly mixed with the polymer PEDOT:PSS solution at a certain volume ratio to obtain GO / PEDOT:PSS / Ti3C2T X Composite solution; Step 3: Making a flexible humidity sensor, including: X The composite solution was evenly drop-coated on the LIG interdigital electrode and dried to make GO / PEDOT:PSS / Ti3C2T X The humidity-sensitive material is firmly attached; metal wires are led out from both ends of the LIG interdigital electrodes to complete the production of the flexible humidity sensor.

[0011] Preferably, step 1 includes: preparing graphene interdigitated electrodes: first, fixing a PI film with a thickness of 75 μm on a substrate, and then placing it in a laser engraving machine. Under atmospheric conditions, a CO2 laser direct writing system (wavelength of 10.6 μm) is used to laser-induce graphene electrodes on the PI film at an engraving speed of 90 mm / s and a laser power of 17.3 W.

[0012] Preferably, the interdigital width of the electrode and the gap spacing between adjacent interdigital fingers are both 600 μm, and the number of interdigital electrode finger pairs is 6.

[0013] Preferably, step 2 comprises: preparing GO / PEDOT:PSS / Ti3C2T X Composite solution: PEDOT:PSS solution was diluted with deionized water at a volume ratio of 1:10. Then, GO dispersion with a concentration of 2 mg / mL and Ti3C2T X The dispersion was mixed with the diluted PEDOT:PSS solution in a volume ratio of 1:1:10. Then, the components were treated by water bath ultrasound for 10 min to ensure uniform mixing of the components, and GO / PEDOT:PSS / Ti3C2T X Compound solution.

[0014] Preferably, step three includes: coating the moisture-sensitive material: taking the prepared GO / PEDOT:PSS / Ti3C2T X The composite solution is evenly dripped on one electrode with a volume of 0.2 mL of solution per electrode. After the dripping is completed, the humidity sensor is carefully placed in a drying oven and baked at 100°C for 30 minutes to solidify the humidity sensitive material.

[0015] Preferably, step three includes: installing copper wires: using silver paste to fix copper tapes on both ends of the electrode, and then putting it in a drying oven and baking it at 100°C for 20 minutes to ensure that the copper wires are firmly installed. Finally, the sensor is cut from the PI film and connected to the test system for detection.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: the sensor of the present invention is relatively small in size, with an overall area of ​​about 2 cm². Due to the use of a PI substrate, it has good flexibility and biocompatibility and can be adhered to any curved surface. In addition, the humidity sensitive material used in the sensor has a fast response speed to humidity, with a response time and recovery time of 1.5 and 12 seconds respectively, and has a wide linear range. This makes the flexible humidity sensor very suitable for responding to rapid humidity changes in the outside world and detection needs in various humidity environments.

[0017] In terms of performance, the humidity sensor shows high sensitivity, with a capacitance sensitivity of 1433.7μF / %RH and a resistance sensitivity of 138.02Ω / %RH, which can achieve accurate humidity detection. At the same time, the sensor also has strong repeatability and good anti-interference, ensuring the stability and reliability of the detection results.

[0018] In the experiment, the present invention successfully achieved real-time monitoring of human breathing and finger distance testing, demonstrating great development potential in the fields of human health monitoring, wearable electronic devices and non-contact human-computer interaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Demonstrated the GO / PEDOT:PSS / Ti3C2T X Schematic diagram of the overall structure of the flexible humidity sensor made of humidity-sensitive material; Figure 2 The microstructural features of the humidity sensor are revealed, which can be seen through the scanning electron microscope (SEM) image; Figure 3 The results show that the doping ratio of Ti3C2T X Response curve of the solution humidity sensor in the range of 11-97%RH; Figure 4 Demonstrated the GO / PEDOT:PSS / Ti3C2T X Capacitance / resistance response curve of the flexible humidity sensor of the humidity-sensitive material in a dynamic humidity environment, where Figure 4 a depicts the response change from low humidity environment to high humidity environment; Figure 4 b shows the response change from high humidity environment to low humidity environment; Figure 5To demonstrate the response time and recovery time of the sensor under specific humidity conditions; Figure 6 Through two subgraphs ( Figure 6 a and Figure 6 b) shows the capacitance and resistance response curves of the sensor to human breathing; Figure 7 Then through two subgraphs ( Figure 7 a and Figure 7 b) shows the capacitance and resistance response curves of the sensor at 2 cm and 0.5 cm away from the finger. DETAILED DESCRIPTION

[0020] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0021] Example: Refer to Figure 1 , demonstrated the GO / PEDOT:PSS / Ti3C2T X Schematic diagram of the overall structure of the flexible humidity sensor made of hygroscopic materials. This figure clearly depicts the design layout of the sensor and provides a basic framework for subsequent analysis. X A flexible humidity sensor of a humidity-sensitive material, comprising: a flexible substrate, a graphene interdigitated electrode, and a humidity-sensitive coating coated on the graphene electrode; the humidity-sensitive coating is GO / PEDOT:PSS / Ti3C2T X Moisture sensitive material, the flexible substrate is PI.

[0022] Example 1: Preparation of graphene interdigitated electrodes: 1) Substrate pretreatment: Clean the glass substrate with glass cleaning liquid, rinse with deionized water, and then blow it clean with nitrogen for use. Then fix the 75μm PI film on the substrate with tape.

[0023] 2) Engraving graphene electrodes: Import the designed electrode pattern into the operating software, set the engraving speed of the laser direct writing system to 90 mm / s, and the engraving power to 17.3 W. Finally, perform laser-induced graphene electrode to obtain graphene interdigitated electrodes.

[0024] Example 2: GO / PEDOT:PSS / Ti3C2T X Preparation of humidity sensitive materials: 1) Dilute the PEDOT:PSS solution with deionized water at a volume ratio of 1:10, and then evenly mix the GO solution with a concentration of 2 mg / mL and the diluted PEDOT:PSS solution at a volume ratio of 1:10; 2) Ti3C2T with a concentration of 5 mg / mLX The dispersion was added into the GO / PEDOT:PSS composite solution in a volume ratio of 1:11 and ultrasonicated for 10 minutes to mix evenly. X The solution preparation is complete.

[0025] Example 3: Based on GO / PEDOT:PSS / Ti3C2T X Preparation of flexible humidity sensor made of moisture-sensitive materials: 1) Take 0.2mL of GO / PEDOT:PSS / Ti3C2T X The solution was evenly dropped on the electrode, which was then placed in a drying oven and baked at 100°C for 30 min to allow the moisture-sensitive material to adhere to the electrode.

[0026] 2) Use silver paste to connect the copper wire to the electrode, and then bake it in a drying oven at 100°C for 20 minutes to prevent the copper wire from falling off.

[0027] Example 4: Based on GO / PEDOT:PSS / Ti3C2T X Characterization of flexible humidity sensors using hygroscopic materials, see Figure 2 , Figure 2 The microstructure characteristics of the humidity sensor are further revealed. The scanning electron microscope (SEM) image shows that the sensor surface presents a large number of wrinkles and pores. These structural characteristics give the sensor good water absorption and provide favorable conditions for humidity detection. According to the scanning electron microscope image of the sensor, it can be seen that the sensor's microstructure presents a large number of wrinkles and pores.

[0028] Example 5: Based on GO / PEDOT:PSS / Ti3C2T X Humidity performance test of humidity sensitive material flexible humidity sensor: 1) The humidity sensitivity of the sensor was examined by using different saturated salt solutions to create changes in the humidity environment. To produce relative humidity (RH) values ​​of 11%, 23%, 33%, 43%, 58%, 68%, 75%, 85% and 97%, supersaturated salt solutions (25°C) of LiCl, CH3COOK, MgCl2, K2CO3, NaBr, CuCl2, NaCl, KCl and K2SO4 were used, respectively.

[0029] 2) The test method is: place the humidity sensor above the salt solution, use a digital source meter to connect the sensor and record the capacitance response curve and resistance response curve of the sensor under different humidity.

[0030] 3) Figure 3 The focus is on the performance of humidity sensors, showing the performance of humidity sensors based on different doping ratios of Ti3C2T XThe response curve of the solution humidity sensor in the range of 11-97% RH. This chart intuitively reflects the response characteristics of the sensor under different humidity conditions and provides an important basis for evaluating its performance. Figure 3 Specifically, Ti3C2T X The resistance response curves of humidity sensors with humidity-sensitive materials whose dispersion volume ratios are 8%, 11%, and 15% respectively. The test results show that the resistance increases gradually as the humidity increases from 11% to 97%. X The test curve linearity of humidity sensor with dispersion volume ratio of 8% is better.

[0031] 4) Figure 4 Through two subgraphs ( Figure 4 a and Figure 4 b) Detailed demonstration of the GO / PEDOT:PSS / Ti3C2T X Capacitance / resistance response curve of flexible humidity sensor made of humidity-sensitive material in dynamic humidity environment. Figure 4 a depicts the response change from low humidity environment to high humidity environment, while Figure 4 Figure b shows the response change from high humidity environment to low humidity environment. These curves help to deeply understand the dynamic performance of the sensor under different humidity change conditions. The test results show that Figure a shows that the capacitance of the sensor decreases and the resistance increases from low relative humidity to high relative humidity, and Figure b shows that the capacitance of the sensor increases and the resistance decreases from high relative humidity to low relative humidity, and it shows good stability.

[0032] 5) Figure 5 The response time and recovery time of the sensor under specific humidity conditions are further shown. This figure takes the capacitance response of a sensor prepared in a preferred embodiment at 23% RH and 58% RH as an example to intuitively demonstrate the rapid response and recovery capabilities of the sensor. Figure 5 Then, the response time and recovery time were 1.5 and 12 s in the 11-97% RH range, respectively, proving that the GO / PEDOT:PSS / Ti3C2T X The moisture-sensitive material flexible humidity sensor has a good response speed.

[0033] Example 6: Detection of human breathing by humidity sensor and finger distance test: Figure 6 and Figure 7 The applications of sensors in human respiration detection and finger non-contact humidity detection are discussed respectively. Figure 6 Through two subgraphs ( Figure 6 a and Figure 6 b) shows the capacitance and resistance response curves of the sensor to human breathing, and Figure 7 Then through two subgraphs ( Figure 7 a and Figure 7 b) shows the capacitance and resistance response curves of the sensor at 2cm and 0.5cm from the finger. These graphs not only show the performance of the sensor in various application scenarios, but also provide strong support for its potential applications.

[0034] 1) Keep the sensor at a certain distance from the human mouth, connect it to the digital source meter to record the capacitance and resistance response curves, and use the sensor to monitor the breathing signal when the human body exhales and inhales. Figure 6 When a person exhales, the ambient humidity increases, the sensor capacitance decreases, and the resistance increases; when a person inhales, the ambient humidity decreases, the sensor capacitance increases, and the resistance decreases.

[0035] 2) Keep the sensor finger at a certain distance and connect it to the digital source meter to record the capacitance and resistance response curves, referring to Figure 7 When the finger is 0.5cm away from the humidity sensor, the ambient humidity increases, the sensor capacitance decreases, and the resistance increases; when the finger is 2cm away from the humidity sensor, the ambient humidity decreases, the sensor capacitance increases, and the resistance decreases.

[0036] It should be noted that the above content only illustrates the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.

Claims

1. A flexible humidity sensor based on graphene oxide-polymer-titanium carbide composite, characterized in that: The invention comprises a flexible substrate, a graphene interdigital electrode laser-engraved on the substrate, and a moisture-sensitive coating coated on the graphene electrode, wherein the moisture-sensitive coating is composed of GO / PEDOT:PSS / Ti3C2T X It is made of moisture-sensitive material and the flexible substrate is polyimide PI.

2. The flexible humidity sensor based on graphene oxide-polymer-titanium carbide composite according to claim 1, characterized in that: The graphene electrode is a laser-induced graphene LIG interdigitated electrode engraved on the PI film by laser direct writing technology.

3. A method for preparing a flexible humidity sensor based on graphene oxide-polymer-titanium carbide composite according to claims 1 to 2, characterized in that: The following steps are involved: Step 1, preparing LIG interdigitated electrodes, comprising: The flexible PI film is fixed on the substrate; the designed electrode pattern is imported into the operating software, and the engraving parameters of the laser direct writing system are set to laser-induce the engraving of LIG interdigital electrodes; Step 2, preparing a moisture-sensitive material, comprising: Graphene oxide GO and titanium carbide Ti3C2T X The dispersion was uniformly mixed with the polymer PEDOT:PSS solution at a certain volume ratio to obtain GO / PEDOT:PSS / Ti3C2T X Composite solution; Step 3: Make a flexible humidity sensor, including: GO / PEDOT:PSS / Ti3C2T X The composite solution was evenly drop-coated on the LIG interdigital electrode and dried to make GO / PEDOT:PSS / Ti3C2T X The humidity-sensitive material is firmly attached; metal wires are led out from both ends of the LIG interdigital electrodes to complete the production of the flexible humidity sensor.

4. The method for preparing a flexible humidity sensor based on graphene oxide-polymer-titanium carbide composite according to claim 3, characterized in that: Step one includes: Preparation of graphene interdigitated electrodes: First, the PI film is fixed on the substrate; It was then placed in a laser engraving machine, and under atmospheric conditions, a CO2 laser direct writing system was used to laser-induce the formation of graphene electrodes on the PI film.

5. The method for preparing a flexible humidity sensor based on graphene oxide-polymer-titanium carbide composite according to claim 4, characterized in that: The interdigital width of the electrode and the gap spacing between adjacent interdigital fingers are both 600 μm, and the number of interdigital electrode finger pairs is 6.

6. The method for preparing a flexible humidity sensor based on graphene oxide-polymer-titanium carbide composite according to claim 3, characterized in that: Step 2 includes: Dilute the PEDOT:PSS solution with deionized water in a volume ratio; Next, GO dispersion, Ti3C2T X The dispersion was mixed with the diluted PEDOT:PSS solution according to the volume ratio; Then, water bath ultrasonic treatment was performed to ensure uniform mixing of the components to obtain GO / PEDOT:PSS / Ti3C2T X Compound solution.

7. The method for preparing a flexible humidity sensor based on graphene oxide-polymer-titanium carbide composite according to claim 3, characterized in that: Step three includes: Take the prepared GO / PEDOT:PSS / Ti3C2T X The composite solution is evenly dropped on one electrode with an appropriate amount of solution for each electrode; After the dispensing is completed, carefully place the humidity sensor in a drying oven and bake it to solidify the humidity sensitive material.

8. The method for preparing a flexible humidity sensor based on graphene oxide-polymer-titanium carbide composite according to claim 3, characterized in that: Step three includes: Use silver paste to secure the copper tape to both ends of the electrode; Then put it in a drying oven and bake it to ensure that the copper wire is firmly installed; Finally, the sensor is cut from the PI film and connected to the test system for detection.

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