HOF-SA humidity-sensitive ion fiber, preparation method and self-powered humidity sensor

Abstract

The invention discloses an HOF-SA humidity-sensitive ion fiber, a preparation method and a self-powered humidity sensor. The preparation method comprises the following steps: preparing an HOF solution; preparing a spinning solution; preparing a solidification liquid; preparing an HOF (at) SA humidity-sensitive fiber; and preparing the HOF (at) SA humidity-sensitive ion fiber. The self-powered humidity sensor disclosed by the invention is small in size and can be made into a dimension specification of 3mm * 1mm * 1mm under a limiting condition; corresponding voltage can be output in an all-weather and static mode according to environment humidity; the preparation process is simple, low in cost and suitable for batch production; use is flexible, series connection and parallel connection are facilitated, and the circuit board can be directly mounted on a PCB in a surface mounting manner; the method has the advantage of short response / recovery time.

Description

Technical Field

[0001] The present invention relates to a HOF@SA humidity-sensitive ionic fiber, a preparation method thereof, and a self-powered humidity sensor, belonging to the technical field of humidity sensors. Background Art

[0002] Currently, when most humidity sensors work, they all require an external power supply to power the sensor. This mode requires a lot of external equipment. Additionally, some self-powered humidity sensors utilize the piezoelectric effect to generate an output voltage (the self-power generation mechanism all uses a nanogenerator, which is a micro generator manufactured using nanotechnology and can convert tiny mechanical motion or energy into electrical energy). This mode requires the conversion of mechanical energy into electrical energy and is easily affected by environmental sounds, vibrations, etc.

[0003] When the above two types of humidity sensors work, they require a lot of external additional equipment, increasing costs, or are easily affected by factors such as environmental sounds and vibrations. When used in large numbers for networking, it brings problems such as hardware redundancy, increased costs, complex wiring, and demanding requirements. Summary of the Invention

[0004] Aiming at the problems existing in the above-mentioned prior art, the present invention provides a HOF@SA humidity-sensitive ionic fiber, a preparation method thereof, and a self-powered humidity sensor, which can directly provide a corresponding output voltage to the outside according to the humidity level in the environment, and the voltage is not affected by other factors in the environment, and has good compatibility, universality, and long-term reliability.

[0005] In order to achieve the above object, a preparation method of a HOF@SA humidity-sensitive ionic fiber adopted by the present invention includes the following steps:

[0006] S1. Prepare a HOF solution: Ultrasonically dissolve 1,2,4,5-tetrakis(4-carboxyphenyl)benzene in a solvent, stir to obtain a uniform HOF-B colloidal suspension, and centrifuge to obtain a HOF solution;

[0007] S2. Prepare a spinning solution: Uniformly mix the HOF solution and the SA dispersion, stir, remove air bubbles by the vacuum method, and fill the HOF / SA mixture into a syringe;

[0008] S3. Prepare a coagulation solution: Prepare a calcium chloride solution, maintain it at 25°C, and keep it in a static state;

[0009] S4. Prepare HOF@SA humidity-sensitive fibers: Place the syringe filled with the spinning solution in step S2 in an injection pump, let it stand and remove air bubbles, maintain at 25°C, uniformly extrude the spinning solution into the calcium chloride solution, soak to obtain HOF@SA humidity-sensitive fibers, wash with water and dry;

[0010] S5. Preparation of HOF@SA humidity-sensitive ionic fiber: Immerse the dried HOF@SA humidity-sensitive fiber in a KCl solution and repeat the processes of soaking and air-drying multiple times to obtain the HOF@SA humidity-sensitive ionic fiber.

[0011] As an improvement, in step S1, the solvent is DMF, and the molar volume ratio of 1,2,4,5-tetrakis(4-carboxyphenyl)benzene to DMF is 0.1 mmol:(5 - 10 ml);

[0012] The molar ratio of 1,2,4,5-tetrakis(4-carboxyphenyl)benzene to water is 0.0001:(8 - 10).

[0013] As an improvement, in step S2, after the HOF solution and SA (sodium alginate) dispersion are uniformly mixed, the mass fraction of SA is 1 - 5%.

[0014] As an improvement, in step S3, the concentration of the calcium chloride solution is 0.1 - 0.3 mol / L.

[0015] As an improvement, in step S4, the spinning solution is extruded into the calcium chloride solution at a rate of 10 mL / min and soaked for 10 min.

[0016] As an improvement, in step S5, a 2 mol / L KCl solution is used, and after each soaking for 1 h, it is air-dried.

[0017] In the second aspect of the present invention, a HOF@SA humidity-sensitive ionic fiber prepared by the described preparation method is also provided.

[0018] In the third aspect of the present invention, a self-powered humidity sensor is also provided, which includes the HOF@SA humidity-sensitive ionic fiber prepared by the described preparation method or the HOF@SA humidity-sensitive ionic fiber, a Cu electrode, a Zn electrode, and a substrate. One end of the HOF@SA humidity-sensitive ionic fiber is connected to the Cu electrode, and the other end is connected to the Zn electrode. The Cu electrode and the Zn electrode are respectively placed on the substrate.

[0019] As an improvement, both the Cu electrode and the Zn electrode are made of metal wires with a diameter of 200 µm - 500 µm. The ends of each metal wire are folded at 3 mm. The two ends of the HOF@SA humidity-sensitive ionic fiber are placed into the folded parts of the two metal wires and pressed together.

[0020] As an improvement, the substrate is made of flexible nylon cloth, PE film, PU film, or insulating rigid substrate.

[0021] The mechanism of the present invention:

[0022] Since HOF@SA humidity-sensitive ion fibers have hydroxyl (—OH) and carboxyl (—COOH) functional groups that have good adsorption properties for water molecules, when the sensor is in a dry state, the ions are adsorbed and fixed by the functional groups due to the functional groups with negative charge characteristics of the device material, and are scattered all over the fiber. At this time, there is no channel for ion movement. This adsorption greatly limits the mobility of ions, resulting in a relatively low ion mobility. When moisture comes into contact with the sensor, the negative electrical properties of the material will attract water molecules. This attraction causes the ions previously adsorbed by the molecules to desorb, and the originally bound ions are converted into free-moving ions. These free-moving ions, driven by the copper electrode and the zinc electrode, generate a positively correlated output voltage at both ends of the copper electrode and the zinc electrode corresponding to the ambient humidity. Moreover, the higher the ambient humidity, the more water molecules cause the originally bound ions to desorb, and the more free-moving ions there are inside the HOF@SA humidity-sensitive ion fiber, resulting in a higher voltage at both ends of the copper electrode and the zinc electrode. The lower the humidity, the fewer ions can move freely inside the HOF@SA humidity-sensitive ion fiber, resulting in a smaller voltage across the copper and zinc electrodes.

[0023] Compared with the prior art, the self-powered humidity sensor of the present invention is tiny in size and can be made into a size of 3mm*1mm*1mm under extreme conditions; it can output a corresponding voltage according to the ambient humidity in a static manner (no mechanical movement and energy are required) in all weather conditions (the self-powered humidity sensor of the present invention only needs water molecules in the ambient humidity, and the amount of water molecules and the type of ions selected determine the output voltage of the sensor); the preparation process is simple, the cost is low, and it is suitable for mass production; it is flexible to use, easy to use in series or parallel, and can also be directly surface mounted on a PCB; it has the advantages of fast response / recovery time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The XRD graph and SEM graph of Example 1 of the present invention; Figure (a) is the XRD graph of SA, HOF, and HOF@SA humidity-sensitive ion fibers, and Figure (b) is the SEM graph of HOF@SA humidity-sensitive ion fibers;

[0025] Figure 2 Fourier transform infrared spectra of SA, HOF, and HOF@SA humidity-sensitive ion fibers according to Example 1 of the present invention;

[0026] Figure 3 This is a schematic diagram of the assembly of the self-powered humidity sensor according to Embodiment 3 of the present invention;

[0027] Figure 4 This is a schematic diagram of the application of the self-powered humidity sensor according to Embodiment 3 of the present invention;

[0028] Figure 5Range test and accuracy of the self-powered humidity sensor of Embodiment 3 of the present invention;

[0029] Figure 6 Response / recovery time test diagram of the self-powered humidity sensor of Embodiment 3 of the present invention;

[0030] Figure 7 Repeatability test of the self-powered humidity sensor of Embodiment 3 of the present invention under different humidity conditions;

[0031] Figure 8 Stability curve of the self-powered humidity sensor of Embodiment 3 of the present invention; Figure (a) is the 300-second long-term stability curve of the humidity sensor at 36%RH, 67%RH, and 82%RH, and (b) is the 1000-second long-term stability curve of the humidity sensor at 93%RH. Detailed implementation mode

[0032] The following embodiments are further descriptions of the content of the present invention to illustrate the technical content of the present invention. However, the substantial content of the present invention is not limited to what is described in the following embodiments. Those of ordinary skill in the art can and should know that any simple changes or substitutions based on the substantial spirit of the present invention should fall within the protection scope required by the present invention.

[0033] Embodiment 1

[0034] A preparation method of HOF@SA humidity-sensitive ion fiber, comprising the following steps:

[0035] S1. Prepare HOF solution: Dissolve 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (0.1 mmol) in 7.5 ml of N,N-dimethylformamide (DMF), stir and dissolve, obtain a clear solution through an ultrasonic machine for 10 minutes, then add 9 mol of water to the above clear solution, stir at room temperature for 45 min, obtain a uniform HOF-B colloid suspension, and finally centrifuge at 8000 rpm for 5 min to separate and obtain the HOF solution;

[0036] S2. Prepare spinning solution: Uniformly mix the HOF solution separated in step S1 and the SA (sodium alginate) dispersion (the mass fraction of SA after mixing is 3%), stir vigorously for 2 h, remove the bubbles in the mixed solution by the vacuum method, and then add the well-dispersed HOF / SA mixture to a syringe equipped with a 22G head (outer diameter 0.7 mm, inner diameter 0.4 mm, length 150 mm);

[0037] S3. Preparation of coagulating liquid: Weigh 22.2 g of analytical pure calcium chloride. Slowly add the weighed calcium chloride to an appropriate amount of deionized pure water in a fume hood while stirring until it is completely dissolved. Transfer the dissolved calcium chloride solution to a 1000 mL volumetric flask and dilute it to the scale line with deionized pure water, and shake well to prepare a 0.2 mol / L calcium chloride solution. When performing wet spinning, it is necessary to keep the temperature of the coagulation bath at 25 °C and keep the coagulation bath in a static state, which is beneficial to the uniformity of the fiber prepared by wet spinning and the integrity of the external morphology;

[0038] S4. Preparation of HOF@SA humidity-sensitive fiber: Place the syringe filled with the spinning solution in step S2 in an injection pump, let it stand for 30 min to remove air bubbles, set the temperature of the coagulation bath (0.2 mol / L CaCl 2 )at 25 °C. Under the condition that the injection pump drives at a constant speed, extrude the spinning solution into the CaCl 2 solution at a rate of 10 mL / min and soak it in the coagulation bath for 10 minutes. Then, roll the obtained continuous wet-spun fiber onto a roller, and place the collected HOF@SA humidity-sensitive fiber in deionized pure water to remove excess Ca ions and dry it;

[0039] S5. Preparation of HOF@SA humidity-sensitive ion fiber: Soak the obtained HOF@SA humidity-sensitive fiber in a 2 mol / L KCl solution for 1 hour, and then air-dry it. This process is repeated 3 times to obtain an ion fiber with sufficient carriers (K + )to obtain the HOF@SA humidity-sensitive ion fiber.

[0040] XRD and Fourier transform infrared spectroscopy analysis were respectively carried out on SA, HOF, and HOF@SA humidity-sensitive ion fiber in Example 1. The results are as Figure 1 、 Figure 2 shown. It can be analyzed that the HOF@SA humidity-sensitive ion fiber is composed of two components, HOF and SA, without other extra impurity peaks. The characteristic peaks of SA appear at 3403 cm -1 and 1612 cm -1 , corresponding to the functional groups of —OH and —COOH. The characteristic peak of HOF at 1701 cm -1 has a carboxyl group (—COOH) functional group. As HOF complexes with SA, their functional groups interact with each other. By cleverly combining these two polymers, stable hydrogen bonds are formed, enhancing the ion transport ability and performance of the fiber.

[0041] In addition, SEM analysis was carried out on the HOF@SA humidity-sensitive ion fiber in Example 1, as Figure 1As shown, analysis reveals that the diameter of the HOF@SA humidity-sensitive ionic fiber is approximately 500 µm. The fiber diameter is relatively uniform, the cross-section is approximately circular, there are no obvious defects in diameter mutation, the fiber surface is relatively smooth, continuous without beads, and there are no obvious defects such as delamination and laminar cracking.

[0042] Example 2

[0043] A preparation method of HOF@SA humidity-sensitive ionic fiber, comprising the following steps:

[0044] S1. Prepare HOF solution: Dissolve 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (0.1 mmol) in 8 ml of N,N-dimethylformamide (DMF), stir to dissolve, obtain a clear solution by ultrasonic treatment for 10 minutes, then add 10 mol of water to the above clear solution, stir at room temperature for 45 min to obtain a uniform HOF-B colloid suspension, and finally centrifuge at 7000 rpm for 10 min to separate and obtain the HOF solution;

[0045] S2. Prepare the spinning solution: Uniformly mix the HOF solution separated in step S1 and the SA dispersion (the mass fraction of SA after mixing is 4%), stir vigorously for 1.5 h, remove the bubbles in the mixed solution by the vacuum method, and then add the well-dispersed HOF / SA mixture to a syringe equipped with a 22G needle (outer diameter 0.7 mm, inner diameter 0.4 mm, length 150 mm);

[0046] S3. Prepare the coagulating bath solution: Weigh 22.2 g of analytical pure calcium chloride, slowly add the weighed calcium chloride to an appropriate amount of deionized pure water in a fume hood while stirring until completely dissolved, transfer the dissolved calcium chloride solution to a 1000 mL volumetric flask, and dilute it to the scale line with deionized pure water, shake well to prepare a 0.2 mol / L calcium chloride solution. When performing wet spinning, it is necessary to keep the temperature of the coagulating bath at 25 °C and keep the coagulating bath in a static state, which is beneficial to the uniformity of fiber preparation by wet spinning and the integrity of the external morphology;

[0047] S4. Prepare HOF@SA humidity-sensitive fiber: Place the syringe filled with the spinning solution in step S2 in an injection pump, let it stand for 20 min to remove air bubbles, set the temperature of the coagulating bath (0.2 mol / L CaCl 2 ) to 25 °C. Under the condition that the injection pump drives at a constant speed, extrude the spinning solution into the CaCl 2 solution at a rate of 10 mL / min, soak in the coagulating bath for 10 minutes, then wind the obtained continuous wet-spun fiber onto a roller, and place the collected HOF@SA humidity-sensitive fiber in deionized pure water to remove excess Ca ions and dry;

[0048] S5. Preparation of HOF@SA humidity-sensitive ionic fiber: Immerse the obtained HOF@SA humidity-sensitive fiber in a 2 mol / L KCl solution for 1 hour, and then air-dry it. This process is repeated 4 times to obtain an ionic fiber with sufficient carriers (K + ), and the HOF@SA humidity-sensitive ionic fiber is obtained.

[0049] Example 3

[0050] As Figure 3 , Figure 4 shown, a self-powered humidity sensor uses the HOF@SA humidity-sensitive ionic fiber, Cu electrode, Zn electrode, and substrate prepared in Example 1;

[0051] Cut a HOF@SA humidity-sensitive ionic fiber with a length ≥ 5 mm and a diameter of 400 µm. Both the Cu electrode and the Zn electrode are made of metal wires with a diameter of 400 µm. Fold the ends of the Cu electrode and Zn electrode wires at 3 mm into loops. Place the middle part (about 3 mm) of the HOF@SA humidity-sensitive ionic fiber in the middle position between the two metal wires, and place the two ends of the HOF@SA humidity-sensitive ionic fiber in the folded loops of the metal wires (leave 1 mm each; as Figure 3 shown), and press the Cu and Zn metal wires against the HOF@SA humidity-sensitive ionic fiber by external force.

[0052] Among them, the substrate material can be a flexible nylon cloth, PE film, PU film, etc., or a rigid substrate made of an insulating material.

[0053] Perform relevant tests on the self-powered humidity sensor prepared in Example 3.

[0054] Test methods and steps: Use a standard humidity generating device as a humidity calibration point to provide different relative humidity environments, and use a high-precision voltmeter to test the voltage output of the sensor.

[0055] Figure 5 For the range test and accuracy of the self-powered humidity sensor, it shows that in an environment of 25 °C, when the humidity range is from 23%RH to 65%RH, the voltage value increases by about 5.94 mV for every 1%RH change. When the humidity range is from 65%RH to 87%RH, the voltage value increases by about 16.04 mV for every 1%RH change. It can be analyzed that this humidity sensor has a good detection range and test accuracy, and a good output dynamic range. In addition, under the condition of 93% RH humidity, the sensor output voltage can reach an output capacity of 0.72 V.

[0056] Figure 6 For the response / recovery time test chart of the self-powered humidity sensor, under the test condition of a relative humidity of 82%RH, the response time is only 0.44 seconds, and the recovery time is 0.34 seconds, with a relatively fast humidity response / recovery time.

[0057] Figure 7 For the repeatability test of the self-powered humidity sensor under different humidity conditions, five cycles of repeatability tests were carried out at different humidity test points, and stable output could be obtained in all cases. Therefore, it has good performance of repeat detection.

[0058] Figure 8 The figure shows the stability curve of the self-powered humidity sensor. After tests with a duration of 300 seconds at three different humidities of 36%RH, 67%RH, and 82%RH and a duration of 1000 seconds at a high humidity of 93%RH, its output performance is not only stable but also has small fluctuations, and it has the ability to work stably with high reliability for a long time.

[0059] The above are only preferred embodiments and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing HOF@SA humidity-sensitive ion fiber, characterized in that: The following steps are involved: S1. Prepare HOF solution: dissolve 1,2,4,5-tetrakis(4-carboxyphenyl)benzene in a solvent by ultrasonication, stir to obtain a uniform HOF-B colloidal suspension, and centrifuge to obtain a HOF solution; S2. Prepare spinning solution: uniformly mix HOF solution and SA dispersion, stir, remove bubbles by vacuum method, and fill HOF / SA mixture into syringe; S3. Prepare coagulation solution: prepare calcium chloride solution, keep it at 25°C, and keep it static; S4, preparing HOF@SA moisture-sensitive fiber: placing the syringe filled with spinning solution in step S2 in a syringe pump, letting it stand, exhausting bubbles, maintaining 25°C, extruding the spinning solution into a calcium chloride solution at a uniform speed, soaking, obtaining HOF@SA moisture-sensitive fiber, washing with water, and drying; S5. Preparation of HOF@SA humidity-sensitive ion fiber: soaking the dried HOF@SA humidity-sensitive fiber in KCl solution for multiple times and air-drying to obtain HOF@SA humidity-sensitive ion fiber.

2. The method for preparing HOF@SA humidity-sensitive ion fiber according to claim 1, characterized in that: In the step S1, the solvent is DMF, and the molar volume ratio of 1,2,4,5-tetrakis(4-carboxyphenyl)benzene to DMF is 0.1mmol:(5-10ml); The molar ratio of the 1,2,4,5-tetrakis(4-carboxyphenyl)benzene to water is 0.0001:(8-10).

3. The method for preparing HOF@SA humidity-sensitive ion fiber according to claim 1, characterized in that: After the HOF solution and the SA dispersion are uniformly mixed in step S2, the mass fraction of SA is 1-5%.

4. The method for preparing HOF@SA humidity-sensitive ion fiber according to claim 1, characterized in that: The concentration of the calcium chloride solution in step S3 is 0.1-0.3 mol / L.

5. The method for preparing HOF@SA humidity-sensitive ion fiber according to claim 1, characterized in that: In step S4, the spinning solution is extruded into the calcium chloride solution at a rate of 10 mL / min and immersed for 10 minutes.

6. The method for preparing HOF@SA humidity-sensitive ion fiber according to claim 1, characterized in that: In step S5, a 2 mol / L KCl solution is used, and each time the mixture is immersed for 1 hour, it is then air-dried.

7. A HOF@SA humidity-sensitive ion fiber, characterized in that: The method is prepared by the preparation method according to any one of claims 1 to 6.

8. A self-powered humidity sensor, characterized in that: It comprises the HOF@SA humidity-sensitive ion fiber prepared by the preparation method according to any one of claims 1 to 6 or according to claim 7, a Cu electrode, a Zn electrode and a substrate, wherein one end of the HOF@SA humidity-sensitive ion fiber is connected to the Cu electrode, and the other end is connected to the Zn electrode, and the Cu electrode and the Zn electrode are respectively placed on the substrate.

9. A self-powered humidity sensor according to claim 8, characterized in that: The Cu electrode and the Zn electrode are both made of metal wires with a diameter of 200µm-500µm. The ends of each metal wire are folded in half at 3mm. The two ends of the HOF@SA humidity-sensitive ion fiber are placed in the folded parts of the two metal wires and pressed together.

10. A self-powered humidity sensor according to claim 8 or 9, characterized in that: The substrate is made of flexible nylon cloth, PE film, PU film or insulating hard substrate.

Images