Self-powered humidity sensor based on carboxylated nanofiber as well as preparation method and application of self-powered humidity sensor

Abstract

The invention discloses a self-powered humidity sensor based on carboxylated nanofibers as well as a preparation method and application of the self-powered humidity sensor. The self-powered humidity sensor comprises a PVA (at) CNF-C electrolyte membrane loaded with ions as well as a positive electrode and a negative electrode which are respectively attached to two sides of the PVA (at) CNF-C electrolyte membrane, and the PVA (at) CNF-C electrolyte membrane is internally provided with a channel for directional migration of ions. According to the self-powered humidity sensor based on the carboxylated nanofibers, rapid transportation of ions in a channel is realized by constructing the channel for directional migration of the ions, so that the self-powered humidity sensor has the characteristics of high sensitivity and low hysteresis, the response time is only 0.62 s, the recovery time is only 0.497 s, and the self-powered humidity sensor still keeps stable performance after more than 100 cycle tests; the problems that a traditional sensor is slow in response and poor in stability are effectively solved.

Description

Technical Field

[0001] This invention relates to a self-powered humidity sensor based on carboxylated nanofibers, its preparation method and application, belonging to the field of humidity sensors. Background Technology

[0002] Traditional humidity sensors generally rely on external power supplies, which not only requires more auxiliary equipment but also limits their application in scenarios without power. At the same time, these sensors are mostly made of metal or metal oxides, which results in complex manufacturing processes, high production costs, and significant environmental pollution during production and disposal. These shortcomings severely restrict their widespread use.

[0003] The core working principle of mainstream humidity sensors is to convert humidity signals into detectable electrical signals by regulating the adsorption and desorption of water molecules on the surface of humidity-sensitive materials, thereby controlling their conductivity or capacitance characteristics. Based on different conduction mechanisms, they can be divided into two categories: one uses electrons or holes as the main charge carriers, leveraging water molecules to regulate the semiconductor band structure or built-in electric field to achieve signal output; the other relies on water-induced ion migration (such as H⁺, Na⁺, K⁺, etc.), generating stable electrical signals through the directional movement of ions within the material.

[0004] For ion-conductive humidity sensors, water molecule adsorption causes ions within the material to migrate directionally under the influence of an electric field or concentration gradient, thereby generating an electrical signal. In this process, the strength of the material's hydrophilicity and the efficiency of ion transport directly determine the sensor's key performance characteristics, such as response speed and sensitivity. However, existing ion-conductive humidity sensors still suffer from problems such as long response recovery time, low on / off ratio, and insufficient stability under high humidity conditions. Improving their stability and on / off ratio has become a pressing technical challenge that needs to be addressed. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a self-powered humidity sensor based on carboxylated nanofibers, its preparation method, and its application. The sensor can quickly respond to the humidity level of the external environment and provide a corresponding output voltage, exhibiting good stability and compatibility.

[0006] To achieve the above objectives, the present invention employs a self-powered humidity sensor based on carboxylated nanofibers, comprising a PVA@CNF-C electrolyte membrane loaded with ions, and a positive electrode and a negative electrode respectively attached to both sides of the PVA@CNF-C electrolyte membrane; the PVA@CNF-C electrolyte membrane has channels inside for directional migration of ions.

[0007] Preferably, the negative electrode is Ti3C2T. x-MXene electrode; the positive electrode is a CT electrode, made of a mixture of CuFe-TBA, PVDF, and ACET;

[0008] The PVA@CNF-C electrolyte membrane is prepared by mixing PVA and CNF-C, followed by directional freezing, freeze-drying, and ion loading by immersion in an ion solution.

[0009] A second aspect of the present invention also provides a method for preparing the self-powered humidity sensor based on carboxylated nanofibers, comprising the following steps:

[0010] (1) Mix PVA and CNF-C, heat and stir to dissolve, and obtain a homogeneous PVA@CNF-C solution;

[0011] (2) PVA@CNF-C solution was added to a freezing mold and subjected to liquid nitrogen directional freezing treatment to obtain PVA@CNF-C solid with channels for directional migration of ions inside;

[0012] (3) Freeze-dry PVA@CNF-C solid to obtain PVA@CNF-C aerogel, and slice it to obtain PVA@CNF-C aerogel film;

[0013] (4) PVA@CNF-C aerogel film is immersed in ionic solution, and after repeated immersion and air drying operations, PVA@CNF-C electrolyte film is obtained;

[0014] (5) The positive and negative electrode slurries are coated on both sides of the PVA@CNF-C electrolyte membrane, and the self-powered humidity sensor is obtained after vacuum drying.

[0015] Preferably, in step (1), the mass ratio of PVA to CNF-C is (1-10):(1-10), and the mixture is heated and stirred at 200 rpm in a water bath at 90-95℃ until completely dissolved.

[0016] Preferably, in step (3), the freeze-drying temperature is -80 ℃ to -40 ℃, and the drying time is 72 h; the thickness of the PVA@CNF-C aerogel film is 2-3 mm, the length is 1.9-2.1 cm, and the width is 0.9-1.1 cm.

[0017] Preferably, in step (4), the ionic solution is a KCl solution with a concentration of 1-3 mol / L; the PVA@CNF-C aerogel film is soaked in KCl solution for 20-40 min and then air-dried for 3-5 h, and the soaking and air-drying operation is repeated 2-5 times.

[0018] Preferably, the negative electrode slurry in step (5) is Ti3C2T.x -MXene electrode paste, the positive electrode paste is CT electrode paste, which is prepared by mixing CuFe-TBA, PVDF and ACET in NMP solution at a mass ratio of (6-10):1:1.

[0019] Preferably, in step (5), the PVA@CNF-C electrolyte membrane is adhered to the PET substrate, and the Ti3C2T... x -MXene electrode paste and CT electrode paste are evenly coated on both sides of the PVA@CNF-C electrolyte membrane, and the spacing between the electrodes is controlled at 4-7 mm.

[0020] A third aspect of the present invention also provides a self-powered humidity sensor based on carboxylated nanofibers, or a self-powered humidity sensor based on carboxylated nanofibers prepared by the preparation method, in at least one of the following applications:

[0021] (1) Application in human respiratory status monitoring devices;

[0022] (2) Application in non-contact human body monitoring devices;

[0023] (3) Application in humidity power generation devices;

[0024] (4) Application in environmental humidity monitoring devices.

[0025] To facilitate a more detailed understanding of the present invention, the mechanism of the present invention is explained below:

[0026] This invention relates to a self-powered humidity sensor fabricated from carboxylated nanofibers. The construction of its directional ion channels relies on the temperature-differential controlled growth direction of ice crystals: by freezing the material from the bottom, ice crystals grow along the temperature gradient towards higher temperatures. This process compresses the carboxylated nanofibers, causing them to align in an orderly manner along the same direction, ultimately forming channels for directional ion migration, thus laying the structural foundation for the sensitivity of humidity response. In low-humidity environments, due to the limited number of water molecules, ions (such as Na+)... + Zn 2+ K⁺, Li + The ions (such as PVA@CNF-C electrolyte membrane) are mainly adsorbed on the surface of the membrane. When the ambient humidity increases, thanks to the excellent hydrophilicity of the PVA@CNF-C electrolyte membrane, a large number of water molecules are adsorbed into the membrane, causing ions to desorb from the membrane surface. Driven by the potential difference between the positive and negative electrodes, the desorbed ions migrate directionally along the directional channel, thereby generating a detectable electrical signal. It is precisely because this invention designs a highly efficient ion migration channel that the sensor's response speed to humidity changes is significantly accelerated.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] (1) The self-powered humidity sensor based on carboxylated nanofibers of the present invention enables rapid transport of ions within the channel by constructing a channel for directional migration, thereby possessing high sensitivity and low hysteresis characteristics. Its response time is only 0.62s and its recovery time is only 0.497s. Moreover, it maintains stable performance after more than 100 cycles of testing, effectively solving the problems of slow response and poor stability of traditional sensors.

[0029] (2) This invention selects Ti3C2T x The combination of the MXene negative electrode and the CT positive electrode enables the sensor to not only function as a high-sensitivity humidity sensor for humidity detection, but also as a humidity power generation device to output a stable electrical signal without relying on an external power source, thus expanding the functional application scenarios of the device.

[0030] (3) The sensor of the present invention can accurately identify the human breathing state (such as distinguishing oral / nasal breathing and monitoring breathing rate) and realize non-contact human body monitoring. At the same time, its raw material cost is low, the preparation process is environmentally friendly, and it has good flexibility based on flexible PET substrate, which can be directly used to develop wearable smart electronic devices to meet the needs of people's livelihood such as health monitoring.

[0031] (4) The preparation process does not require complex equipment and precision operation. From the preparation of PVA@CNF-C solution and directional freeze molding to electrode coating and drying, each step is a mature process that is easy to scale up and replicate, effectively reducing the production operation threshold. The core raw materials are CNF-C (carboxylated nanofibers) and PVA (polyvinyl alcohol), which are widely available and inexpensive. No rare metals or high-cost special materials are required. At the same time, the simplified preparation process reduces equipment investment and energy consumption, further reducing the overall production cost, making it suitable for mass production and commercial application. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of the self-powered humidity sensor according to Embodiment 1 of the present invention;

[0033] Figure 2 This is a scanning electron microscope image of the PVA@CNF-C directional ion channel in the self-powered humidity sensor of Embodiment 1 of the present invention;

[0034] Figure 3 This is a schematic diagram of ion transport using a PVA@CNF-C directional ion channel in the self-powered humidity sensor of Embodiment 1 of the present invention;

[0035] Figure 4 The graph shows the response recovery time of the self-powered humidity sensor of the present invention at a relative humidity of 82% RH.

[0036] Figure 5The humidity response curve of the self-powered humidity sensor of the present invention in an environment of 12% RH ~ 93% RH;

[0037] Figure 6 The humidity response curves of the self-powered humidity sensor of the present invention after 100 cycles in 12% RH and 58% RH humidity environments are shown.

[0038] Figure 7 The self-powered humidity sensor of the present invention generates response curves with different response signals at different distances when used as a non-contact switch;

[0039] Figure 8 The figure shows the respiratory detection curve of the self-powered humidity sensor of the present invention for human breathing; Figure (a) shows rapid breathing, and (b) shows normal breathing.

[0040] Figure 9 A photograph of the self-powered humidity sensor of the present invention as a humidity power generation device to power an LED light;

[0041] Figure 10 The VT curve of the self-powered humidity sensor of the present invention as a humidity power generation device. Detailed Implementation

[0042] The following embodiments are further illustrations of the present invention and serve as explanations of the technical content of the present invention. However, the essence of the present invention is not limited to the embodiments described below. Those skilled in the art can and should know that any simple changes or substitutions based on the spirit of the present invention should fall within the protection scope claimed by the present invention.

[0043] Example 1

[0044] A method for fabricating a self-powered humidity sensor based on carboxylated nanofibers includes the following steps:

[0045] (1) Mix PVA and CNF-C at a mass ratio of 5:1, add to 20 ml of deionized water, heat and stir at 200 rpm in a 93℃ water bath until completely dissolved to obtain a homogeneous PVA@CNF-C solution;

[0046] (2) PVA@CNF-C solution was slowly injected into a freezing mold and frozen from the bottom of the material with liquid nitrogen (the temperature of liquid nitrogen is -196℃) for 20 minutes to obtain PVA@CNF-C solid with directional ion channels (channels for directional ion migration);

[0047] (3) Place the PVA@CNF-C solid in a freeze dryer and vacuum dry it for 72 hours at -60°C in a cold trap to obtain PVA@CNF-C aerogel. Slice it into a PVA@CNF-C aerogel film with a thickness of 3 mm, a length of 2 cm and a width of 1 cm.

[0048] (4) The PVA@CNF-C aerogel film was immersed in 2 mol / L KCl solution for 30 min, and then air-dried for 4 h. The immersion-air-drying operation was repeated 3 times to obtain a PVA@CNF-C electrolyte membrane with directional ion channels.

[0049] (5) Take Ti3C2T x -MXene solution was centrifuged and the concentration was adjusted to 5 mg / ml to prepare negative electrode slurry;

[0050] (6) Weigh 80mg CuFe-TBA (Prussian blue analogue), 10mg PVDF (polyvinylidene fluoride), and 10mg ACET (acetylene black) in a mass ratio of 8:1:1, add them to 1ml NMP (N-methylpyrrolidone) solution and mix thoroughly to prepare CT positive electrode slurry;

[0051] (7) The PVA@CNF-C electrolyte membrane is attached to a 2cm×1cm PET substrate, and MXene negative electrode paste and CT positive electrode paste are evenly coated on both sides, and the electrode spacing is controlled to be 4-7mm.

[0052] (8) The device coated with positive and negative electrode pastes is placed in a vacuum drying oven and dried at 60°C for 2 hours to obtain the self-powered humidity sensor. Figure 1 As shown.

[0053] The microstructure of the directional ion channel of the self-powered humidity sensor prepared in Example 1 can be obtained by SEM image (…). Figure 2 As can be seen from the figure, the channels exhibit a clear lateral arrangement, directly confirming that the present invention has successfully prepared directional ion channels.

[0054] The working mechanism of this self-powered humidity sensor is as follows: Figure 3 As shown: In low humidity environments, potassium ion transport is hindered; when humidity increases, the PVA@CNF-C electrolyte membrane adsorbs water molecules due to its excellent hydrophilicity, and its internal directional ion channels provide pathways for ion transport, promoting the rapid directional migration of potassium ions under the action of electrode potential difference, thereby achieving highly sensitive response and recovery.

[0055] Example 2

[0056] The mass ratio of PVA to CNF-C in step (1) of Example 1 was adjusted from 5:1 to 2:1, and the remaining steps were the same as in Example 1.

[0057] Example 3

[0058] The mass ratio of PVA to CNF-C in step (1) of Example 1 was adjusted from 5:1 to 10:1, and the remaining steps were the same as in Example 1.

[0059] Example 4

[0060] The mass ratio of PVA to CNF-C in step (1) of Example 1 was adjusted from 5:1 to 1:2, and the remaining steps were the same as in Example 1.

[0061] Example 5

[0062] The mass ratio of PVA to CNF-C in step (1) of Example 1 was adjusted from 5:1 to 1:10, and the remaining steps were the same as in Example 1.

[0063] Example 6

[0064] The self-powered humidity sensor of this invention exhibits excellent humidity-sensitive performance, including a high on / off ratio and fast response recovery speed. Taking the sensor prepared in Example 1 as an example, its response performance was tested within a humidity range of 12% RH to 93% RH:

[0065] like Figure 4 As shown, the self-powered humidity sensor has a response time of only 0.62s and a recovery time of 0.497s under a relative humidity of 82% RH, demonstrating fast humidity response / recovery performance. This performance stems from the PVA@CNF-C electrolyte membrane containing directional ion channels: its excellent hydrophilicity allows it to rapidly adsorb moisture when humidity changes, altering the ion migration state within the membrane. Combined with the directional channels, this accelerates ion transport, thereby quickly triggering changes in the electrical signal, achieving rapid response and recovery to humidity.

[0066] like Figure 5 As shown, this self-powered humidity sensor responds to humidity ranges from 12% RH to 93% RH and exhibits good differentiation between different humidity levels. When ambient humidity changes, water molecules enter the electrolyte membrane and alter the migration rate of ions, thereby causing changes in the electrical signal. This ensures that the sensor can sensitively capture humidity fluctuations across a range from low to high humidity.

[0067] like Figure 6 As shown, the self-powered humidity sensor has undergone more than 100 cycle tests, and its performance remains stable without any performance degradation due to the increase in the number of cycles, which fully demonstrates that it has the reliability and durability required for practical applications.

[0068] Example 7

[0069] Using the self-powered humidity sensor prepared in Example 1 as a humidity power generation device, it can continuously output a voltage of 1.1 V for 40,000 s, demonstrating excellent humidity power generation capability (its voltage-time curve is shown in Figure 1). Figure 10 (As shown).

[0070] Example 8

[0071] The self-powered humidity sensor of this invention possesses good biocompatibility, wearability, and excellent sensing performance, and has application potential in the fields of human respiratory status monitoring and non-contact human body monitoring. Taking the self-powered humidity sensor prepared in Example 1 as an example:

[0072] like Figure 7 As shown, when the distance between a human finger and the sensor is 1-6 mm, the sensor can output different response signals according to different distances, indicating that the sensor has high sensitivity and can detect minute humidity changes within a short distance. It can accurately sense the fluctuations of the humidity field around the human body without direct contact, and is therefore suitable for non-contact human-computer interaction monitoring scenarios, providing technical support for non-contact control and monitoring.

[0073] like Figure 8 As shown, this sensor can identify different breathing methods and rates, including oral breathing and nasal breathing. During respiration, each inhalation and exhalation significantly alters the local air humidity. This sensor can quickly capture these humidity changes and distinguish different breathing states by analyzing differences in electrical signals. This functionality expands the application of wearable devices in the field of human health monitoring.

[0074] Example 9

[0075] The self-powered humidity sensor prepared in Example 1, when used as a humidity power generation device, can continuously output 1.1 V voltage for 40,000 s and has independent power supply capability.

[0076] like Figure 9 As shown, the sensor can drive an LED light, indicating that it not only has a highly sensitive humidity response capability but also a self-powered function, capable of converting humidity changes into electrical energy to power external devices. This functionality further demonstrates that the sensor can operate continuously and provide a stable power supply to other electronic devices without requiring an external power source.

[0077] The voltage-time curve of the sensor is as follows: Figure 10 As shown, its voltage output characteristics under humidity changes are demonstrated. This characteristic not only significantly enhances the practical value of the sensor, but also provides key technical support for its application in self-powered scenarios (such as low-power electronic devices and portable monitoring devices).

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-powered humidity sensor based on carboxylated nanofibers, characterized in that, It includes a PVA@CNF-C electrolyte membrane loaded with ions, and a positive electrode and a negative electrode respectively attached to both sides of the PVA@CNF-C electrolyte membrane; the PVA@CNF-C electrolyte membrane has channels inside for directional migration of ions.

2. The self-powered humidity sensor based on carboxylated nanofibers according to claim 1, characterized in that, The negative electrode is Ti3C2T. x -MXene electrode; the positive electrode is a CT electrode, made of a mixture of CuFe-TBA, PVDF, and ACET; The PVA@CNF-C electrolyte membrane is prepared by mixing PVA and CNF-C, followed by directional freezing, freeze-drying, and ion loading by immersion in an ion solution.

3. A method for preparing a self-powered humidity sensor based on carboxylated nanofibers as described in any one of claims 1-2, characterized in that, Includes the following steps: (1) Mix PVA and CNF-C, heat and stir to dissolve, and obtain a homogeneous PVA@CNF-C solution; (2) PVA@CNF-C solution was added to a freezing mold and subjected to liquid nitrogen directional freezing treatment to obtain PVA@CNF-C solid with channels for directional migration of ions inside; (3) Freeze-dry PVA@CNF-C solid to obtain PVA@CNF-C aerogel, and slice it to obtain PVA@CNF-C aerogel film; (4) PVA@CNF-C aerogel film is immersed in ionic solution, and after repeated immersion and air drying operations, PVA@CNF-C electrolyte film is obtained; (5) The positive and negative electrode slurries are coated on both sides of the PVA@CNF-C electrolyte membrane, and the self-powered humidity sensor is obtained after vacuum drying.

4. The method for preparing a self-powered humidity sensor based on carboxylated nanofibers according to claim 3, characterized in that, In step (1), the mass ratio of PVA to CNF-C is (1-10):(1-10), and the mixture is heated and stirred at 200 rpm in a water bath at 90-95℃ until completely dissolved.

5. The method for preparing a self-powered humidity sensor based on carboxylated nanofibers according to claim 3, characterized in that, In step (3), the freeze-drying temperature is -80 ℃ to -40 ℃, and the drying time is 72 h; the thickness of the PVA@CNF-C aerogel film is 2-3 mm, the length is 1.9-2.1 cm, and the width is 0.9-1.1 cm.

6. The method for preparing a self-powered humidity sensor based on carboxylated nanofibers according to claim 3, characterized in that, In step (4), the ionic solution is a KCl solution with a concentration of 1-3 mol / L; the PVA@CNF-C aerogel film is soaked in KCl solution for 20-40 min and then air-dried for 3-5 h, and the soaking and air-drying operation is repeated 2-5 times.

7. The method for preparing a self-powered humidity sensor based on carboxylated nanofibers according to claim 3, characterized in that, In step (5), the negative electrode slurry is Ti3C2T. x -MXene electrode paste, the positive electrode paste is CT electrode paste, which is prepared by mixing CuFe-TBA, PVDF and ACET in NMP solution at a mass ratio of (6-10):1:

1.

8. The method for preparing a self-powered humidity sensor based on carboxylated nanofibers according to claim 7, characterized in that, In step (5), the PVA@CNF-C electrolyte membrane is adhered to the PET substrate, and the Ti3C2T... x -MXene electrode paste and CT electrode paste are evenly coated on both sides of the PVA@CNF-C electrolyte membrane, and the spacing between the electrodes is controlled at 4-7 mm.

9. A self-powered humidity sensor based on carboxylated nanofibers as described in any one of claims 1-2, or a self-powered humidity sensor based on carboxylated nanofibers prepared by the preparation method described in any one of claims 3-8, in at least one of the following applications: (1) Application in human respiratory status monitoring devices; (2) Application in non-contact human body monitoring devices; (3) Application in humidity power generation devices; (4) Application in environmental humidity monitoring devices.

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