Preparation method and application of humidity color-changing super-hydrophilic electrostatic spinning membrane

Abstract

The invention discloses a preparation method and application of a humidity color-changing super-hydrophilic electrostatic spinning membrane, the preparation method comprises the following steps: adding acetone into cellulose diacetate (CDA), polyvinylpyrrolidone (PVP) and cobalt chloride hydrate (CoCl2. 6H2O), and uniformly mixing to prepare a CDA / PVP / CoCl2. 6H2O mixed solution; adding acetone into hydrophilic bacterial cellulose BC, carrying out ultrasonic treatment, adding the dispersion liquid into the mixed solution, and continuously stirring to prepare a CDA / PVP / BC coated CoCl2. 6H2O electrostatic spinning solution; stretching the electrostatic spinning solution into filaments under the action of high pressure through an electrostatic spinning machine to prepare a super-hydrophilic electrostatic spinning membrane; according to the invention, the modification effect of PVP and BC enables the hydrophilicity of the CDA electrostatic spinning membrane to be greatly improved; the super-hydrophilic flexible capacitive humidity sensor which is high in sensitivity, stable and quick in response is successfully prepared through the electrostatic spinning film.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible wearable sensing devices, and particularly relates to a preparation method and application of a humidity-responsive color-changing superhydrophilic electrospun membrane. Background Art

[0002] With the rapid development of wearable electronic devices, the demand for flexible, efficient, and intelligent sensors is increasing continuously. Among these devices, humidity sensors, as a key tool for monitoring environmental parameters, are widely used in fields such as health monitoring, environmental detection, and industrial control. However, common humidity sensors on the current market still have certain limitations in terms of sensitivity, response speed, and stability, especially in terms of flexibility and wearability. Therefore, it is particularly important to develop a new type of humidity sensor with high sensitivity, fast response, color indication for humidity change, and easy combination onto a flexible substrate.

[0003] Electrospinning technology has attracted much attention because it can prepare fiber networks with high specific surface area and porosity. At the same time, this technology can achieve uniform distribution of materials. Superhydrophilic thin films prepared based on electrospinning technology show great potential in the field of humidity sensing due to their excellent hydrophilicity and water absorption ability.

[0004] Since the application fields of flexible wearable humidity sensors involve intelligent robots, medical monitoring, daily exercise monitoring, etc., although great efforts have been made in improving sensitivity, fast response, and selection of flexible substrate materials for flexible wearable sensors, it is still necessary to make improvements according to the specific situation to meet various application scenarios.

[0005] Therefore, for flexible wearable humidity sensors to truly be applied in various fields, it is necessary to continuously improve their performance. Summary of the Invention

[0006] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title, but such simplifications or omissions shall not be used to limit the scope of the present invention.

[0007] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0008] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a preparation method for a superhydrophilic electrospun membrane.

[0009] To solve the above technical problems, the present invention provides the following technical solution: A preparation method for a superhydrophilic electrospun membrane, characterized in that it includes:

[0010] Acetone was added to cellulose diacetate (CDA), polyvinylpyrrolidone (PVP), and cobalt chloride hexahydrate (CoCl₂·6H₂O), and the mixture was stirred evenly to obtain a CDA / PVP@CoCl₂·6H₂O mixed solution.

[0011] Acetone was added to hydrophilic bacterial cellulose (BC), and after ultrasonic treatment, the dispersion was added to the above mixed solution, and stirring was continued to obtain a CDA / PVP / BC@CoCl₂·6H₂O electrospinning solution.

[0012] The CDA / PVP / BC@CoCl₂·6H₂O mixed solution was stretched into fine filaments under high pressure by an electrospinning machine to prepare a CDA / PVP / BC@CoCl₂·6H₂O superhydrophilic electrospun membrane.

[0013] As a preferred embodiment of the preparation method of the present invention, in the CDA / PVP@CoCl₂·6H₂O mixed solution, the mass ratio of CDA, PVP, and CoCl₂·6H₂O is 4 - 8:2 - 4:0.5 - 1.

[0014] As a preferred embodiment of the preparation method of the present invention, in the CDA / PVP@CoCl₂·6H₂O mixed solution, the mass ratio of CDA, PVP, and CoCl₂·6H₂O is 4:2:0.5.

[0015] As a preferred embodiment of the preparation method of the present invention, acetone was added to hydrophilic bacterial cellulose (BC), and the concentration of hydrophilic bacterial cellulose (BC) in the dispersion was 2 - 3 g / L, and a dispersion was obtained after ultrasonic treatment.

[0016] As a preferred embodiment of the preparation method of the present invention, the ultrasonic time is 0.5 - 2.0 h.

[0017] As a preferred embodiment of the preparation method of the present invention, the voltage of the electrospinning machine is 17.00 - 21.00 kV.

[0018] As a preferred embodiment of the preparation method of the present invention, the feeding speed of the electrospinning machine is 0.003 - 0.01 mm / s, and the speed of the pusher moving uniformly left and right is set to 1.0 - 3.0 mm / min.

[0019] Another object of the present invention is to provide a superhydrophilic electrospun membrane.

[0020] Another object of the present invention is to provide the application of the superhydrophilic electrospun membrane in the preparation of a flexible capacitive humidity - color - changing sensor.

[0021] As a preferred embodiment of the application of the present invention, when the environmental humidity is 33 - 86% RH, the electrospun membrane absorbs water molecules, the dielectric constant changes, and the sensor presents a red color; when the environmental humidity is 12 - 33% RH, the electrospun membrane dehydrates water molecules, and the sensor presents a blue color.

[0022] Advantages of the present invention:

[0023] (1) The present invention prepares a CDA / PVP / BC@CoCl2·6H2O electrospun film with humidity - color - changing super - hydrophilicity;

[0024] (2) In the present invention, the modification effect of PVP and BC greatly improves the hydrophilicity of the CDA electrospun membrane;

[0025] (3) Based on the CDA / PVP / BC electrospun film, the present invention successfully prepares a super - hydrophilic flexible capacitive humidity sensor with high sensitivity, stability, and fast response. Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0027] Figure 1 It is the preparation flow chart of the humidity - color - changing super - hydrophilic CDA / PVP / BC@CoCl2·6H2O electrospun film in Embodiment 1 of the present invention.

[0028] Figure 2 It is the morphology diagram of the humidity - color - changing super - hydrophilic CDA / PVP / BC@CoCl2·6H2O electrospun film prepared in Embodiment 1 of the present invention.

[0029] Figure 3 It is the FTIR diagram of the humidity - color - changing super - hydrophilic CDA / PVP / BC@CoCl2·6H2O electrospun film prepared in Embodiment 1 of the present invention.

[0030] Figure 4 It is the water contact angle test diagram of the humidity - color - changing super - hydrophilic CDA / PVP / BC@CoCl2·6H2O electrospun film prepared in Embodiment 2 of the present invention.

[0031] Figure 5 It is the water absorption ratio curve of the humidity - color - changing super - hydrophilic CDA / PVP / BC@CoCl2·6H2O electrospun film in Embodiment 4 of the present invention.

[0032] Figure 6 This is the humidity-capacitance change curve, i.e., the sensitivity curve; the fast response curve; the cyclic response / recovery curve, i.e., the stability curve, of the CDA / PVP / BC@CoCl2·6H2O flexible capacitive humidity sensor in Example 4 of the present invention.

[0033] Figure 7 This is the capacitance change rate-humidity relationship curve of the superhydrophilic CDA / PVP / BC@CoCl2·6H2O electrospun film sensor in Example 4 of the present invention, which is fixed on the palm of the human body to monitor the change of human skin humidity under static, walking, and running conditions.

[0034] Figure 8 This is the color performance test chart of the superhydrophilic CDA / PVP / BC@CoCl2·6H2O electrospun film in the dry / wet states in Example 4 of the present invention. The CDA / PVP / BC@CoCl2·6H2O electrospun film is blue after dehydration and turns red after moisture absorption.

[0035] Figure 9 This is the water contact angle test chart of the humidity-responsive color-changing superhydrophilic CDA electrospun film prepared in Comparative Example 1 of the present invention.

[0036] Figure 10 This is the water contact angle test chart of the humidity-responsive color-changing superhydrophilic CDA / PVP electrospun film prepared in Comparative Example 2 of the present invention.

[0037] Figure 11 This is the color performance test chart of the superhydrophilic CDA / PVP / BC@CoCl2·6H2O electrospun film in the dry / wet states in Comparative Example 3 of the present invention. Detailed Embodiments

[0038] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given in conjunction with the embodiments of the specification.

[0039] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0040] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that can be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that excludes other embodiments.

[0041] Raw materials and reagents used in the present invention: cellulose diacetate (CDA, purchased from Shanghai Vita Chemical Reagent Co., Ltd.), polyvinylpyrrolidone (PVP, purchased from Shanghai Macklin Biochemical Co., Ltd.), bacterial cellulose (BC, purchased from Guilin Qihong Technology Co., Ltd.), CoCl2·6H2O purchased from Shanghai Macklin Biochemical Co., Ltd., and acetone purchased from Shanghai Vita Chemical Reagent Co., Ltd.

[0042] Experimental methods used in the present invention:

[0043] Hydrophilicity test:

[0044] Take a CDA / PVP / BC@CoCl2·6H2O electrospun membrane with a length of 0.5 cm and a width of 0.2 cm, and place it flat on the standard piece of the water contact angle test bench. The video acquisition system records the dynamic change process of the contact angle of the water droplet on the electrospun membrane. The contact time is the time length for measuring the contact angle after the water droplet contacts the membrane surface.

[0045] Refer to the following:

[0046] Water contact angle > 90° - Hydrophobicity

[0047] Water contact angle < 90° - Hydrophilicity

[0048] Water contact angle = 90° - Hydrophilic-hydrophobic balance

[0049] For the convenience of more intuitively comparing the hydrophilicity of the electrospun membranes in this example and the comparative example, the hydrophilicity of the electrospun membranes is now distinguished and described as follows:

[0050] Water contact angle 80 - 90° - Very low hydrophilicity

[0051] Water contact angle 40 - 80° - Low hydrophilicity

[0052] Water contact angle 10 - 40° - High hydrophilicity

[0053] Water contact angle 0 - 10° - Extremely high hydrophilicity

[0054] Water absorption performance test:

[0055] Take a CDA / PVP / BC@CoCl2·6H2O electrospun membrane with a length of 3.0 cm and a width of 2.0 cm. After drying for 2.0 h, record the initial mass (m0), and record the mass (m t ) of the electrospun membrane after soaking in pure water for 2.0 h. Record it every 7 minutes. The water absorption ratio (ε) is calculated according to the following formula: ε = (m t - m0) / m0 × 100%.

[0056] Example 1

[0057] This embodiment provides a method for preparing a humidity-responsive color-changing superhydrophilic electrospun membrane

[0058] 1. Preparation of hydrophilic electrospinning solution

[0059] Take 4.0 g of CDA, 2.0 g of PVP, and 0.5 g of CoCl₂·6H₂O and add them to 70 mL of acetone. Stir magnetically at 40 °C for 1.0 h to mix evenly to obtain a CDA / PVP@CoCl₂·6H₂O mixed solution; take 0.025 g of BC and add it to 10 mL of acetone, sonicate for 1.0 h, and add the BC ultrasonic dispersion to the CDA / PVP@CoCl₂·6H₂O mixed solution, then continue to stir magnetically for 1.0 h to prepare a CDA / PVP / BC@CoCl₂·6H₂O electrospinning solution

[0060] 2. Preparation method of humidity-responsive color-changing superhydrophilic CDA / PVP / BC@CoCl₂·6H₂O electrospun film

[0061] Take 5 mL of the CDA / PVP / BC@CoCl₂·6H₂O electrospinning solution, place it in an electrospinning machine, connect a voltage of 17.28 kV, set the feeding speed to 0.005 mm / s, and set the speed of the reciprocating movement of the pusher to 2 mm / min. The preparation process of the humidity-responsive color-changing superhydrophilic CDA / PVP / BC@CoCl₂·6H₂O electrospun film is as Figure 1 shown. The SEM image of the humidity-responsive color-changing superhydrophilic CDA / PVP / BC@CoCl₂·6H₂O electrospun film (as Figure 2 shown), the FTIR image of the humidity-responsive color-changing superhydrophilic CDA / PVP / BC@CoCl₂·6H₂O electrospun film (as Figure 3 shown).

[0062] The results show that the surface of pure CDA fibers is smooth and dense. After modification with PVP and BC, PVP and BC are attached to the surface of CDA fibers in the form of microspheres or fibrous structures, and the surface of CDA fibers becomes rough, forming a denser cross-linked network( Figure 2 ); the hydroxyl groups on the surfaces of CDA and BC interact with the carbonyl groups of PVP in the form of hydrogen bonds, playing a role in cross-linking and strengthening( Figure 3 ).

[0063] Example 2

[0064] This embodiment provides a method for testing the hydrophilicity and water absorption of a superhydrophilic electrospun film

[0065] 1. Hydrophilicity test:

[0066] The results are as Figure 4As shown, the water droplet quickly spreads on the surface of the CDA / PVP / BC@CoCl2·6H2O electrospun membrane in 0.76 s, and the water contact angle is close to 0°, showing excellent hydrophilic performance, indicating that the hydrophilic performance of the CDA electrospun membrane modified by PVP and BC has been significantly improved.

[0067] 2. Water absorption performance test:

[0068] The results are as Figure 5 shown. The water absorption ratio of the CDA / PVP / BC@CoCl2·6H2O electrospun membrane reaches 2000% at 20 min. Subsequently, the water absorption rate slows down. The water absorption ratio of the CDA / PVP / BC@CoCl2·6H2O electrospun membrane is 2816% at 120 min, and there is no obvious deformation before and after the electrospun membrane absorbs moisture, showing excellent hydrophilic and water-resistant properties.

[0069] Example 3

[0070] This example provides a humidity-responsive color-changing superhydrophilic CDA / PVP / BC@CoCl2·6H2O flexible capacitive humidity sensor.

[0071] 1. Preparation method of the humidity-responsive color-changing superhydrophilic CDA / PVP / BC@CoCl2·6H2O flexible capacitive humidity sensor:

[0072] First, paste the interdigital electrodes on the receiver of the electrospinning machine.

[0073] Subsequently, take 5 mL of the CDA / PVP / BC@CoCl2·6H2O electrospinning solution, place it on the syringe pump of the electrospinning machine, connect a voltage of 17.28 kV, set the feeding speed to 0.005 mm / s, and directly electrospin the CDA / PVP / BC@CoCl2·6H2O mixed solution onto the interdigital electrodes through electrospinning technology to make the CDA / PVP / BC@CoCl2·6H2O electrospun film tightly combine with the interdigital electrodes.

[0074] Finally, connect the interdigital electrodes covered with the CDA / PVP / BC electrospun film to an LCR digital bridge to test the sensing performance of the CDA / PVP / BC@CoCl2·6H2O flexible capacitive humidity sensor.

[0075] 2. Applications of the humidity-responsive color-changing superhydrophilic CDA / PVP / BC@CoCl2·6H2O flexible capacitive humidity sensor, including:

[0076] Step 1: Mask breathing humidity-capacitance response test

[0077] The CDA / PVP / BC@CoCl2·6H2O electrospun membrane was implanted into a mask to sense the change in respiratory humidity. During the exhalation / inhalation cycle, the humidity-capacitance response was tested. The change in capacitance under actual breathing conditions was verified; the humidity-capacitance response curve was plotted for the inhalation-exhalation states.

[0078] The results are as Figure 7 (a) shown. The unique characteristics of the capacitance response in terms of period and amplitude can reflect the respiratory state. For 10 consecutive deep breathing tests over 312 s, the capacitance response time for each deep breath was 2.7 s for exhalation and 29.0 s for inhalation, and the capacitance response amplitude reached about 280, indicating a high water molecule content in the air exhaled from the nose and mouth. This demonstrated the high repeatability and reliability of the CDA / PVP / BC@CoCl2·6H2O flexible capacitive humidity sensor for respiratory monitoring.

[0079] Step 2: Human motion monitoring

[0080] The CDA / PVP / BC@CoCl2·6H2O electrospun membrane was adhered to the same part of the human body to monitor the change in human skin humidity when standing still, walking, and running, record the humidity-capacitance response; plot the humidity-capacitance response curve for different motion states.

[0081] The results are as Figure 7 (b) shown. When standing still, the metabolic rate is low, the demand for body temperature regulation is small, the sweat secretion is small, the skin humidity is low and stable, and the capacitance value is low with a low fluctuation amplitude (about 3.0); walking is a medium-intensity exercise, the metabolic rate increases, the body temperature rises, triggering sweat gland activity, the skin humidity gradually increases, the capacitance value slowly rises with time, and the fluctuation amplitude increases accordingly (about 4.0); running causes a sharp increase in sweating, a steep increase in humidity, a rapid increase in the capacitance value, and the fluctuation amplitude increases to the maximum (about 6.0).

[0082] Example 4

[0083] This example provides a performance test of a CDA / PVP / BC@CoCl2·6H2O flexible capacitive humidity sensor

[0084] Sensing performance test method:

[0085] Prepare saturated solutions of LiCl at 12% RH, MgCl2 at 33% RH, NaBr at 58% RH, and KCl at 86% RH, and use an LCR digital bridge for sensing performance testing. The electrodes of the CDA / PVP / BC@CoCl2·6H2O flexible capacitive humidity sensor are connected to the LCR digital bridge, and the flexible capacitive humidity sensor is placed in a saturated solution chamber with different humidities to measure the sensing performance of the humidity sensor, such asFigure 6 as shown in (a).

[0086] 1. Sensor sensitivity test:

[0087] Place the CDA / PVP / BC@CoCl2·6H2O flexible capacitive humidity sensor in a wide-mouth bottle capped with a saturated LiCl solution at 12% RH. After the capacitance stabilizes, quickly place the sensor in a wide-mouth bottle capped with a saturated KCl solution at 86% RH to test the capacitance change with humidity.

[0088] The results are as Figure 6 shown in (b). In the range of 12 - 86% RH, the capacitance-relative humidity response curve shows a linear relationship. The capacitance change rate of the sensor increases with the increase of relative humidity. In the low humidity range of 12 - 33% RH, its sensitivity is 34.8, with a relatively slow growth; in the range of 33 - 58% RH, the unit capacitance increases more and more with the increase of relative humidity, and the sensitivity reaches 340.2; in the high humidity range of 58 - 86% RH, the increasing speed slows down and finally flattens out, with a sensitivity of 185.5. The results show that the CDA / PVP / BC@CoCl2·6H2O flexible capacitive humidity sensor has high sensitivity. Therefore, this super-hydrophilic CDA / PVP / BC@CoCl2·6H2O electrospun membrane can be applied to humid environments with high humidity.

[0089] 2. Sensor repeatable response / recovery test:

[0090] Place the CDA / PVP / BC@CoCl2·6H2O flexible capacitive humidity sensor in a wide-mouth bottle capped with a saturated LiCl solution at 12% RH. After the capacitance stabilizes, place the sensor in a wide-mouth bottle capped with a saturated KCl solution at 86% RH. After the capacitance stabilizes, place the sensor back in the wide-mouth bottle capped with a saturated LiCl solution at 12% RH and repeat 6 times to characterize the response / recovery repeat stability of the capacitive humidity sensor.

[0091] The capacitance-relative humidity response curves of two-cycle tests in the range of 12 - 86% RH are as Figure 6 shown in (c). The sensitivity amplitudes of the two-cycle tests are similar, with the sensitivity value around 560.5. In the ranges of 12 - 33% RH, 12 - 58% RH, and 12 - 86% RH, the sensitivities of 6-cycle tests within 1200 s gradually increase with a stable amplitude. It shows that the CDA / PVP / BC@CoCl2·6H2O flexible capacitive humidity sensor has excellent sensitivity and stability.

[0092] Figure 8This is the color performance test chart of the dry / wet two states of the 4-superhydrophilic CDA / PVP / BC@CoCl2·6H2O electrospun film in the embodiments of the present invention. When the environmental humidity is 12 - 33%RH, the electrospun film dehydrates and presents blue. When the environmental humidity is 33 - 86%RH, the electrospun film absorbs water molecules, the dielectric constant changes, and it presents red;

[0093] Comparative Example 1

[0094] The difference between this example and Example 1 is that in Step 1, PVP, CoCl2·6H2O, and BC are not added.

[0095] The remaining process steps are all referred to Example 1 to obtain the CDA film of this example, and the contact angle test is as Figure 9 shown.

[0096] The results show that the contact angle of the CDA film is 81.09°, showing relatively low hydrophilicity.

[0097] Comparative Example 2

[0098] The difference between this example and Example 1 is that in Step 1, CoCl2·6H2O and BC are not added.

[0099] The remaining process steps are all referred to Example 1 to obtain the CDA / PVP film of this example, and the contact angle test is as Figure 10 shown.

[0100] The results show that the contact angle of the CDA / PVP film is 11.75°, showing excellent hydrophilic performance, indicating that PVP has a good effect on the hydrophilic modification of CDA.

[0101] Comparative Example 3

[0102] The difference between this example and Example 1 is that in Step 1, CoCl2·6H2O is not added.

[0103] The remaining process steps are all referred to Example 1 to obtain the CDA / PVP / BC film of this example, and the contact angle test is as Figure 11 shown.

[0104] The results show that the contact angle of the CDA / PVP / BC film is 8.44°. Since the hydrophilic PVP and BC adhere to the surface of the CDA fibers, the CDA / PVP / BC film exhibits extremely excellent hydrophilicity, indicating that PVP and BC have a good synergistic enhancement effect on the hydrophilic modification of CDA.

[0105] The hydrophilicity of Example 1 and Comparative Examples 1 - 3 was measured, and the results are shown in Table 1.

[0106] Table 1 Hydrophilicity of Example and Each Comparative Example

[0107]

[0108] As can be seen from Table 1, the water contact angle of the pure CDA film is 81.09°, and the contact time is 0.96 s. The CDA film has extremely low hydrophilicity. After modifying the CDA film with PVP, the water contact angle is increased to 11.75°, and the contact time becomes 3.79 s, which takes longer, but shows high hydrophilicity. After modifying CDA with PVP and BC, the water contact angle is increased to 8.44°, and the time used is 0.76 s. The hydrophilicity is significantly improved, showing extremely high hydrophilicity. By introducing CoCl·6H2O into the CDA film modified with PVP and BC, the CDA / PVP / BC@CoCl2·6H2O electrospun film is prepared. Its water contact angle approaches 0°, and the contact time is 0.76 s, showing extremely high hydrophilicity.

[0109] Comparative Example 4

[0110] The difference between this example and Example 1 is that: in Step 1, 4.0 g of cellulose diacetate CDA is replaced with 8.0 g of cellulose diacetate CDA.

[0111] The processes of the remaining steps are all referred to Example 1 to obtain the CDA / PVP / BC@CoCl2·6H2O film of this example.

[0112] Comparative Example 5

[0113] The difference between this example and Example 1 is that: in Step 1, 4.0 g of cellulose diacetate CDA is replaced with 6.0 g of cellulose diacetate CDA.

[0114] The processes of the remaining steps are all referred to Example 1 to obtain the CDA / PVP / BC@CoCl2·6H2O film of this example.

[0115] Comparative Example 6

[0116] The difference between this example and Example 1 is that: in Step 1, 4.0 g of cellulose diacetate CDA is replaced with 2.0 g of cellulose diacetate CDA.

[0117] The processes of the remaining steps are all referred to Example 1 to obtain the CDA / PVP / BC@CoCl2·6H2O film of this example.

[0118] Comparative Example 7

[0119] The difference between this example and Example 1 is that: in Step 1, 2.0 g of polyvinylpyrrolidone PVP is replaced with 4.0 g of polyvinylpyrrolidone PVP.

[0120] For the remaining process steps, refer to Example 1 to obtain the CDA / PVP / BC@CoCl2·6H2O film of this example.

[0121] Comparative Example 8

[0122] The difference between this example and Example 1 is that: in Step 1, 2.0 g of polyvinylpyrrolidone PVP is replaced with 3.0 g of polyvinylpyrrolidone PVP.

[0123] For the remaining process steps, refer to Example 1 to obtain the CDA / PVP / BC@CoCl2·6H2O film of this example.

[0124] Comparative Example 9

[0125] The difference between this example and Example 1 is that: in Step 1, 2.0 g of polyvinylpyrrolidone PVP is replaced with 1.0 g of polyvinylpyrrolidone PVP.

[0126] For the remaining process steps, refer to Example 1 to obtain the CDA / PVP / BC@CoCl2·6H2O film of this example.

[0127] Comparative Example 10

[0128] The difference between this example and Example 1 is that: in Step 1, 0.5 g of cobalt chloride hexahydrate is replaced with 0.9 g of cobalt chloride hexahydrate.

[0129] For the remaining process steps, refer to Example 1 to obtain the CDA / PVP / BC@CoCl2·6H2O film of this example.

[0130] Comparative Example 11

[0131] The difference between this example and Example 1 is that: in Step 1, 0.5 g of cobalt chloride hexahydrate is replaced with 0.7 g of cobalt chloride hexahydrate.

[0132] For the remaining process steps, refer to Example 1 to obtain the CDA / PVP / BC@CoCl2·6H2O film of this example.

[0133] Comparative Example 12

[0134] The difference between this example and Example 1 is that: in Step 1, 0.5 g of cobalt chloride hexahydrate is replaced with 0.3 g of cobalt chloride hexahydrate.

[0135] For the remaining process steps, refer to Example 1 to obtain the CDA / PVP / BC@CoCl2·6H2O film of this example.

[0136] Comparative Example 13

[0137] The difference between this example and Example 1 is that: in Step 1, 0.025 g of BC is replaced with 0.045 g of BC.

[0138] The remaining process steps are all referred to Example 1 to obtain the CDA / PVP / BC@CoCl2·6H2O film of this example.

[0139] Comparative Example 14

[0140] The difference between this example and Example 1 is that 0.035 g of BC is replaced with 0.025 g of BC in Step 1.

[0141] The remaining process steps are all referred to Example 1 to obtain the CDA / PVP / BC@CoCl2·6H2O film of this example.

[0142] Comparative Example 15

[0143] The difference between this example and Example 1 is that 0.015 g of BC is replaced with 0.025 g of BC in Step 1.

[0144] The remaining process steps are all referred to Example 1 to obtain the CDA / PVP / BC@CoCl2·6H2O film of this example.

[0145] The performance results of Example 1 and Comparative Examples 4 to 15 are shown in Table 2.

[0146] Table 2 Hydrophilicity of the Example and Each Comparative Example

[0147]

[0148] The results are shown in Table 2, indicating that with the increase in the dosage of CDA, the density of CDA fibers in the CDA / PVP / BC@CoCl2·6H2O electrospun membrane increases, and the hydrophilic rate of the membrane decreases. Due to the modification of PVP and BC on the surface of CDA fibers, the CDA / PVP / BC@CoCl2·6H2O electrospun membrane still exhibits good hydrophilicity. With the increase in the dosage of PVP, the hydrophilic rate of the CDA / PVP / BC@CoCl2·6H2O electrospun membrane is fast, and the contact angle approaches 0°, showing extremely high hydrophilicity. Since the surface of BC contains more hydroxyl groups, with the increase in the content of BC, the hydrophilic rate of the CDA / PVP / BC@CoCl2·6H2O electrospun membrane accelerates, and the contact angle approaches 0°, showing good hydrophilicity. CoCl2·6H2O has good hygroscopicity. Therefore, with the increase in its content, the hydrophilic rate of the CDA / PVP / BC@CoCl2·6H2O electrospun membrane slightly accelerates, and the color change and moisture absorption change are more obvious. The results of the examples and comparative examples show that PVP and BC have good hydrophilic modification effects on CDA. Under the synergistic enhancement of the two, the CDA / PVP / BC@CoCl2·6H2O electrospun membrane exhibits excellent hydrophilicity, laying a good foundation for the development of humidity-change color indicators and highly sensitive humidity sensors.

[0149] It should be noted that the above examples are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a super-hydrophilic electrospinning membrane, characterized in that: include, Acetone was added to cellulose diacetate CDA, polyvinyl pyrrolidone PVP and hydrated cobalt chloride CoCl2·6H2O, and the mixture was mixed uniformly to prepare a CDA / PVP@CoCl2·6H2O mixed solution; Acetone was added to the hydrophilic bacterial cellulose BC, and after ultrasonication, the dispersion was added to the above mixed solution and stirred continuously to obtain CDA / PVP / BC@CoCl2·6H2O electrospinning solution; The CDA / PVP / BC@CoCl2·6H2O mixed solution was stretched into filaments under high pressure using an electrospinning machine to prepare CDA / PVP / BC@CoCl2·6H2O superhydrophilic electrospinning membrane.

2. The method for preparing a super-hydrophilic electrospinning solution according to claim 1, characterized in that: In the CDA / PVP@CoCl2·6H2O mixed solution, the mass ratio of CDA, PVP and CoCl2·6H2O is 4-8:2-4:0.5-1.

3. The method for preparing a super-hydrophilic electrospinning solution according to claim 1, characterized in that: In the CDA / PVP@CoCl2·6H2O mixed solution, the mass ratio of CDA, PVP and CoCl2·6H2O is 4:2:0.

5.

4. The method for preparing the BC ultrasonic dispersion according to claim 1, characterized in that: Acetone is added to the hydrophilic bacterial cellulose BC, wherein the concentration of the hydrophilic bacterial cellulose BC in the dispersion is 2-3 g / L, and the dispersion is obtained after ultrasonic treatment.

5. The method for preparing a super-hydrophilic electrospinning solution as claimed in any one of claims 1 or 4, characterized in that: The ultrasonic time is 0.5 to 2.0 hours.

6. The method for preparing a super-hydrophilic electrospinning membrane according to claim 1, characterized in that: The voltage of the electrospinning machine is 17.00-21.00 kV.

7. The method for preparing a super-hydrophilic electrospinning membrane according to claim 1, characterized in that: The pushing speed of the electrospinning machine is 0.003-0.01 mm / s, and the left-right uniform moving speed of the propeller is set to 1.0-3.0 mm / min.

8. The CDA / PVP / BC@CoCl2·6H2O super-hydrophilic electrospinning membrane prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the super-hydrophilic electrospinning membrane according to claim 8 in the preparation of a flexible capacitive humidity color-changing sensor.

10. The use according to claim 9, characterized in that: When the ambient humidity is 33-86% RH, the electrospun membrane absorbs water molecules, the dielectric constant changes, and the sensor appears red; when the ambient humidity is 12-33% RH, the electrospun membrane dehydrates the molecules and the sensor appears blue.

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