A biomimetic flexible humidity sensing composite material and a preparation method and application thereof

Abstract

The application provides a kind of bionic flexible humidity sensing composite material and its preparation method and application.The bionic flexible humidity sensing composite material is composed of flexible substrate, conductive doped layer and surface active modification layer; wherein, the flexible substrate is polyvinyl alcohol as base material, formed by electrospinning into micron fiber network; conductive material is added in the electrospinning process to form the conductive doped layer, and surfactant is added to form the surface active modification layer.The preparation method is simple, and the main steps only involve electrospinning process, and the material preparation has strong repeatability; and the raw materials used are mainly water-soluble polyvinyl alcohol, without introducing organic solvent, more environmentally friendly.The pore channels distributed on the bionic flexible humidity sensing composite material prepared by the application are antler-like porous structure, the pore channel plane size is 0.5-2 μm, near elliptical, and multiple pore channels form micron-level breathable network, thereby improving the humidity permeation efficiency and realizing high-efficiency air permeation function.

Description

Technical Field

[0001] This invention relates to the field of humidity sensing at human-machine interfaces, and more particularly to a biomimetic flexible humidity sensing composite material and its preparation method, which can be used for the diagnosis and monitoring of respiratory diseases. Background Technology

[0002] In the diagnosis and treatment of respiratory diseases, accurately assessing the moisture level of the airway mucosa is crucial for understanding respiratory health, and changes in the humidity of exhaled gases are a key indirect indicator. Therefore, developing sensing technologies that can comfortably and continuously monitor the humidity of exhaled gases has significant clinical significance and application value for early warning, disease assessment, and monitoring of treatment effects for respiratory diseases such as asthma, chronic obstructive pulmonary disease, and sleep apnea.

[0003] In the field of human-machine interface applications (such as wearable devices and integrated sensors in breathing masks), humidity sensing technology is crucial for monitoring exhaled gases. Current research mainly relies on flexible humidity sensors based on polymers or nanomaterials. However, existing flexible humidity sensors have many shortcomings in the low to high humidity range (30%-90% RH). For example, traditional hydrogel-based sensors have significant drawbacks: they are complex to fabricate and their performance is easily affected by fluctuations in ambient temperature and humidity; moisture evaporation at high temperatures leads to a decline in mechanical and electrical properties; under high humidity conditions, internal inorganic salts (such as LiCl) easily dissolve and leach out, damaging the sensing layer structure and causing a significant reduction in response in the low humidity range (<40% RH). Simultaneously, some materials have poor mechanical flexibility and deformation stability, making it difficult to adapt to repeated bending during human activity or breathing mask use. Their biocompatibility and long-term contact comfort are also limited, failing to meet the clinical needs of both high-precision humidity response and wearability reliability.

[0004] Therefore, developing a novel flexible humidity sensing material and its preparation method that combines rapid response, excellent air permeability, good biocompatibility and environmental stability, and is simple and controllable in preparation, has become an urgent problem to be solved. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a biomimetic flexible humidity sensing composite material, its preparation method, and its application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a biomimetic flexible humidity sensing composite material, which is composed of a flexible substrate, a conductive doped layer, and a surface-active modification layer. The flexible substrate is formed by electrospinning a micron-fiber network using polyvinyl alcohol as the substrate. During the electrospinning process, a conductive material is incorporated to form the conductive doped layer, and a surfactant is added to form the surface-active modification layer.

[0008] Furthermore, the surface of the biomimetic flexible humidity sensing composite material is distributed with multiple biomimetic channels of 0.5 to 2 μm in size, and the inner wall of the biomimetic channels is provided with several derived nanopores; the minimum thickness of the biomimetic flexible humidity sensing composite material is 5 μm.

[0009] Furthermore, the conductive material includes one or more of carbon black, single-walled / multi-walled carbon nanotubes, MXene, and graphene; the surfactant includes one or more of polyvinylpyrrolidone, polyethylene glycol, polyacrylamide, and hydroxyethyl cellulose.

[0010] The present invention also provides a method for preparing the above-mentioned biomimetic flexible humidity sensing composite material, characterized in that the preparation method includes: mixing polyvinyl alcohol, carbon black and polyvinylpyrrolidone to obtain a homogeneous spinning composite solution; electrospinning the spinning composite solution to obtain a composite spinning film; and impregnating the composite spinning film with ethanol to obtain the biomimetic flexible humidity sensing composite material.

[0011] Furthermore, the preparation method specifically includes the following steps: S1, dissolving polyvinyl alcohol, carbon black, and polyvinylpyrrolidone in a mixed solution of deionized water and acetic acid, and then ultrasonically stirring for 5–30 min to obtain a composite solution; treating the composite solution in a 90°C oil bath for 4–6 h, and then naturally cooling to obtain a spinning composite solution; S2, electrospinning the spinning composite solution, and then drying it at 80°C for 4 h to obtain a composite spun membrane; S3, immersing the composite spun membrane in an ethanol solution for 10–60 s, then removing it and air-drying it to obtain the biomimetic flexible humidity sensing composite material. In this process, polyvinyl alcohol undergoes a recrystallization process to obtain a flexible humidity sensing composite material with a porous structure.

[0012] Furthermore, in S1, the mass ratio of deionized water to acetic acid in the mixed solution of deionized water and acetic acid is 1:1 to 3:7.

[0013] Furthermore, in S1, in the mixed solution of deionized water and acetic acid, the mass fraction of polyvinyl alcohol is 5% to 20%, the mass fraction of carbon black is 0.1% to 4%, and the mass fraction of polyvinylpyrrolidone is 0.05% to 0.5%.

[0014] Furthermore, in S2, the parameters for the electrospinning treatment are as follows: a 22G spinning needle is used; the spinning needle is perpendicular to the sample stage covered with oil paper and the distance between them is 10–25 cm; the flow rate of the spinning composite solution is set to 0.1–2 mL / h. -1 The moving speed is 50-200 mm / min. -1 The voltage for electrospinning is 10–40 kV.

[0015] Furthermore, the preparation method also includes: before S1, pre-treating the container and stirring element used to prepare the spinning composite solution; the pre-treatment includes ultrasonically washing the container and stirring element twice each with ethanol and deionized water, with each washing time being 15 min, and then drying them at 80°C for 2 h.

[0016] The present invention also provides an application of the above-described biomimetic flexible humidity sensing composite material in the field of respiratory disease diagnosis and monitoring.

[0017] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages:

[0018] This invention provides a biomimetic flexible humidity sensing composite material, its preparation method, and its application. The preparation method is simple, with the main steps involving only electrospinning, and the material preparation is highly repeatable. Furthermore, the raw material used is mainly water-soluble polyvinyl alcohol, without the introduction of organic solvents, making it more environmentally friendly.

[0019] The biomimetic flexible humidity sensing composite material prepared by this invention has a porous structure that mimics the antennae of ants. The planar size of the pores is 0.5-2μm and nearly elliptical. Multiple pores form a micron-level breathable network, thereby improving the moisture permeability and achieving a highly efficient breathable function.

[0020] In addition, the biomimetic flexible humidity sensing composite material prepared by this invention can exhibit different resistance response effects to different breathing behaviors, thus meeting application requirements. Attached Figure Description

[0021] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments, and unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0022] Figure 1 SEM image of the antennae of the Japanese carpenter ant;

[0023] Figure 2 The images show photographs and planar microscopic schematic diagrams of the biomimetic flexible humidity sensing composite material obtained in Example 1 of this invention.

[0024] Figure 3The images show the cross-section and planar SEM images of the biomimetic flexible humidity sensing composite material obtained in Example 1 of this invention.

[0025] Figure 4 The infrared spectrum of the biomimetic flexible humidity sensing composite material obtained in Example 2 of this invention is shown.

[0026] Figure 5 The resistance change of the biomimetic flexible humidity sensing composite material obtained in Example 3 of the present invention was tested by nasal breathing (normal and rapid breathing).

[0027] Figure 6 The resistance change of the biomimetic flexible humidity sensing composite material obtained in Example 4 of the present invention was tested by mouth breathing (normal and rapid breathing).

[0028] Figure 7 The resistance change of the biomimetic flexible humidity sensing composite material obtained in Example 5 of the present invention was tested by mouth breathing (normal).

[0029] Figure 8 The resistance change of the biomimetic flexible humidity sensing composite material obtained in Example 6 of the present invention is shown in the test of mouth breathing (normal). Detailed Implementation

[0030] The inventors discovered that the unique tactile humidity sensing mechanism of ants' antennae inspired humidity sensing technology. Applying this technology to the monitoring of humidity in human exhaled breath is expected to break through technical bottlenecks and achieve accurate and efficient monitoring. This invention is proposed for this purpose.

[0031] Inspired by the porous humidity sensing mechanism of ant antennae, this invention aims to overcome the problems of slow response, poor air permeability and biocompatibility of flexible humidity sensing films, and provides a simple process and a high application value of biomimetic flexible humidity sensing composite material and its preparation method.

[0032] The present invention will now be described in detail with reference to specific embodiments.

[0033] Example 1:

[0034] This embodiment describes a method for preparing a biomimetic flexible humidity sensing composite material, which is completed according to the following steps:

[0035] First, pre-treat a 50mL glass beaker, a 50mL graduated cylinder, and a 1cm magnetic rotor. Place them in an ultrasonic cleaner and ultrasonically clean them with anhydrous ethanol for 15 minutes each time. Then pour out the waste liquid and ultrasonically clean them with deionized water for 15 minutes each time. Repeat this process twice. Finally, place them in an 80℃ oven to dry for 2 hours before taking them out for use.

[0036] Next, a spinning composite solution was prepared. 9g of deionized water and 9g of acetic acid (mass ratio 1:1) were added to a pretreatment beaker and a magnetic rotor was placed inside. Then, 2g of ethylene alcohol (mass fraction approximately 9.8%), 0.4g of carbon black (mass fraction approximately 2%), and 0.05g of polyvinylpyrrolidone were weighed and added to the mixed solution (mass fraction 0.24%). The mixture was ultrasonically stirred (power 300W) for 30 minutes until it was evenly dispersed to obtain a black composite solution. The beaker was then transferred to a 90℃ oil bath and magnetically stirred (speed 500rpm) for 5 hours. Heating was then stopped and the mixture was allowed to cool naturally to room temperature to obtain a homogeneous spinning solution.

[0037] Then, a composite spun film was prepared. 10 mL of the above solution was drawn using a 12 mL plastic syringe, and a 22G needle was attached. The sample stage, covered with oil paper, was placed in an electrospinning machine (model: NF-500). The vertical distance between the needle and the sample stage was adjusted to 15 cm, and the solution flow rate was set to 0.5 mL / h. -1 Sample stage moving speed 100 mm·min -1 The spinning voltage is 25kV. The equipment is started and spinning is carried out for 1 hour to form a uniform composite spinning film on the oil paper. Then, it is transferred to a forced-air drying oven and heat-treated at 80℃ for 4 hours to solidify the fiber structure.

[0038] Finally, a flexible composite humidity sensing film was prepared by immersing the dried spun film in anhydrous ethanol solution until it was completely wetted. After standing for 30 minutes, it was taken out and naturally air-dried at room temperature of 25°C for 24 hours to complete the polyvinyl alcohol recrystallization process and form a porous flexible humidity sensing composite material.

[0039] The macroscopic structure of the biomimetic flexible porous composite material obtained is as follows: Figure 2 As shown, the surface exhibits porous characteristics, and the cross-section displays a layered structure containing microstructured pores. For example... Figure 3 As shown, SEM testing revealed that the material surface forms a porous structure of 0.5–2 μm through a renucleation mechanism, similar to... Figure 1 The ant antennae shown are highly biomimetic; the cross-section is constructed by electrospinning to create a micron-scale fiber network, which is then optimized for density by ethanol impregnation. Each layer is an ultra-thin vertical layered structure of 5μm. The layered structure here refers to the layered structure that appears by increasing the product thickness as needed through electrospinning. The function of each layer is completely consistent. The surface of the pore wall is derived with nanopores to form a micron-nano cross-scale composite system, which reproduces the antennae's humidity sensing mechanism and realizes the reproduction of humidity sensing performance.

[0040] Example 2:

[0041] This embodiment describes a method for preparing a biomimetic flexible humidity sensing composite material, which is completed according to the following steps: Based on Embodiment 1, this embodiment sets the electrospinning voltage to 30KV and adjusts the spinning time to 6 hours. The infrared spectrum of the prepared flexible humidity sensing composite material is as follows: Figure 4 As shown, approximately 3289cm -1 A broad peak is observed at this point, indicating the presence of strong O-H stretching vibration; 2911 cm⁻¹ -1 The presence of a peak nearby indicates a strong C-H bond in the alkane, suggesting that the carbon in the carbon black is well bonded to the polyvinyl alcohol; approximately 1711 cm⁻¹ -1 The peak at 1090 cm⁻¹ corresponds to a C-O bond; -1 The nearby peaks represent C-O-C bonds. These characteristics indicate that the infrared spectral features of this biomimetic flexible humidity sensing composite material are consistent with those of the polyvinyl alcohol / carbon black / polyvinylpyrrolidone composite material.

[0042] Example 3:

[0043] This embodiment describes a method for preparing a biomimetic flexible humidity sensing composite material, which is completed according to the following steps: Based on Example 2, this embodiment adjusts the vertical distance between the adjustment needle and the sample stage to 20 cm and the solution flow rate to 0.7 mL / h. -1 Finally, the samples prepared in Example 3 were subjected to nasal breathing sensor tests, such as... Figure 5 As shown, the flexible humidity sensing composite material exhibits varying resistance changes under different nasal breathing conditions due to variations in breathing frequency and depth. Under normal nasal breathing, the resistance change is uniform and slow, while under rapid breathing, the resistance change is chaotic and rapid. These results indicate that the humidity sensor can provide real-time feedback on respiratory status under different conditions and can provide early warning of potential risks related to respiratory diseases.

[0044] Example 4:

[0045] This embodiment describes a method for preparing a biomimetic flexible humidity sensing composite material, which is completed according to the following steps: Based on Embodiment 3, this embodiment increases the sample stage moving speed of Embodiment 3 to 150 mm / min. -1 Finally, the sample obtained in Example 4 was subjected to a mouth breathing test, such as... Figure 6 As shown, it can be seen that due to the different breathing depths, the resistance trend of the biomimetic flexible humidity sensing composite material is significantly different from that of nasal breathing. Furthermore, the resistance change is uniform and slow under normal mouth breathing, while the resistance change under rapid breathing is smaller in amplitude and higher in frequency.

[0046] Example 5:

[0047] This embodiment describes a method for preparing a biomimetic flexible humidity sensing composite material, which is completed according to the following steps: Based on Example 4, in the sample spinning solution treatment of Example 4, 12g of deionized water and 6g of acetic acid (mass ratio 2:1) are added respectively. The dried spun membrane is then immersed in anhydrous ethanol solution, and the immersion time is changed to 10 minutes before removal. Finally, the sample obtained in Example 5 is subjected to a mouth breathing test, such as... Figure 7 As shown, it can be seen that during normal breathing, the resistance change range of the humidity sensing composite material prepared in Example 5 is similar to that of the sample obtained in Example 4, but the response time is significantly slower than that of the sample obtained in Example 4. This is because insufficient renucleation time results in fewer porous structures being formed, and the response time is significantly slower.

[0048] Example 6:

[0049] This embodiment describes a method for preparing a biomimetic flexible humidity sensing composite material, which is completed according to the following steps: Based on Example 4, this embodiment changes the carbon black mass in the spinning solution treatment of the sample in Example 4 to 0.6 g (mass fraction approximately 3%). Finally, the sample obtained in Example 6 is subjected to a mouth breathing test, as shown... Figure 8 As shown, it can be seen that during normal breathing, the resistance change range of the humidity sensing composite material prepared in Example 6 is increased by an order of magnitude compared with the sample prepared in Example 4. The response time is slightly slower than that of the sample prepared in Example 4. This is because the increased carbon content can significantly enhance the conductivity of the composite material. However, excessive carbon doping causes some carbon to be unevenly doped into the composite material and instead cover the surface of the composite material, affecting the contact area between the composite material and water molecules in the air, thereby reducing the response time.

[0050] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of the present invention. Any person skilled in the art can make their own modifications and alterations without departing from the spirit and scope of the present invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A biomimetic flexible humidity sensing composite material, characterized in that, The biomimetic flexible humidity sensing composite material is composed of a flexible substrate, a conductive doped layer, and a surface-active modification layer. The flexible substrate is formed by electrospinning polyvinyl alcohol to create a micron fiber network. During the electrospinning process, conductive materials are incorporated to form the conductive doped layer, and surfactants are added to form the surface-active modified layer. The surface of the biomimetic flexible humidity sensing composite material is distributed with multiple biomimetic channels with porous structures resembling ant antennae. The planar size of the biomimetic channels is 0.5~2 μm, and the inner wall of the biomimetic channels is provided with several derived nanopores. The multiple biomimetic channels form a micron-level breathable network. The biomimetic channels are formed by impregnating the composite spun film obtained by electrospinning with ethanol, thereby recrystallizing polyvinyl alcohol.

2. The biomimetic flexible humidity sensing composite material according to claim 1, characterized in that, The minimum thickness of the biomimetic flexible humidity sensing composite material is 5 μm.

3. The biomimetic flexible humidity sensing composite material according to claim 1, characterized in that, The conductive material includes one or more of carbon black, single-walled / multi-walled carbon nanotubes, MXene, and graphene; The surfactant includes one or more of polyvinylpyrrolidone, polyethylene glycol, polyacrylamide, and hydroxyethyl cellulose.

4. A method for preparing a biomimetic flexible humidity sensing composite material according to any one of claims 1 to 3, characterized in that, The preparation method includes: mixing polyvinyl alcohol, carbon black and polyvinylpyrrolidone to obtain a homogeneous spinning composite solution; electrospinning the spinning composite solution to obtain a composite spinning membrane; and impregnating the composite spinning membrane with ethanol to obtain the biomimetic flexible humidity sensing composite material.

5. The method for preparing the biomimetic flexible humidity sensing composite material according to claim 4, characterized in that, The preparation method specifically includes the following steps: S1. Polyvinyl alcohol, carbon black and polyvinylpyrrolidone are dissolved in a mixed solution of deionized water and acetic acid, and then ultrasonically stirred for 5-30 min to obtain a composite solution; the composite solution is treated in an oil bath at 90℃ for 4-6 h and then naturally cooled to obtain a spinning composite solution. S2. The spinning composite solution is subjected to electrospinning treatment, and then dried at 80°C for 4 h to obtain a composite spinning film. S3. After immersing the composite spun membrane in an ethanol solution for 10-60 seconds, remove it and air dry it naturally to obtain the biomimetic flexible humidity sensing composite material.

6. The method for preparing the biomimetic flexible humidity sensing composite material according to claim 5, characterized in that, In S1, the mass ratio of deionized water to acetic acid in the mixed solution of deionized water and acetic acid is 1:1 to 3:

7.

7. The method for preparing the biomimetic flexible humidity sensing composite material according to claim 6, characterized in that, In S1, in the mixed solution of deionized water and acetic acid, the mass fraction of polyvinyl alcohol is 5%~20%, the mass fraction of carbon black is 0.1%~4%, and the mass fraction of polyvinylpyrrolidone is 0.05~0.5%.

8. The method for preparing the biomimetic flexible humidity sensing composite material according to claim 5, characterized in that, In S2, the parameters for the electrospinning treatment are as follows: a 22G spinning needle is used; the spinning needle is perpendicular to the sample stage covered with oil paper and the distance between them is 10-25 cm; the flow rate of the spinning composite solution is set to 0.1-2 mL / h. -1 The moving speed is 50~200 mm / min -1 The voltage for electrospinning is 10~40 KV.

9. The method for preparing the biomimetic flexible humidity sensing composite material according to claim 5, characterized in that, The preparation method further includes: before S1, pre-treating the container and stirring device used to prepare the spinning composite solution; The pretreatment includes ultrasonically washing the container and stirring piece twice each with ethanol and deionized water, with each washing session lasting 15 minutes. After cleaning, the container and stirring piece are dried at 80°C for 2 hours.

10. The application of a biomimetic flexible humidity sensing composite material according to any one of claims 1 to 3 in the preparation of a humidity sensor that can provide early warning of potential dangers to respiratory-related diseases.

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