Nanosilk fiber membrane with directional water transport and preparation method thereof

Abstract

The present invention discloses a nano-silk fibroin membrane with directional water transport and its preparation method. Renewable pure silk fibroin protein is extracted from natural silkworm cocoons and electrospun to form a nanofiber-like silk fibroin membrane. The membrane is then treated with methanol to induce a secondary structural transformation, resulting in hydrophilic and hygroscopic properties. Octadecyltrichlorosilane (OTS) is then sprayed onto the membrane, depositing a uniformly arranged, reticulated hydrophobic inner layer and reticulated water transport channels on one side. The resulting OTS-coated membrane exhibits excellent directional water transport, with a directional water transport index (R) as high as 978%. The preparation method achieves directional water transport while maintaining the mechanical and radiant cooling properties of the original silk fibroin membrane. Furthermore, the preparation method is environmentally friendly, simple, and scalable.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber membranes, and in particular to a nano-silk fiber membrane with directional water transport and a preparation method thereof. Background Art

[0002] With the development of science and technology, functional textiles and wearable materials are becoming hot research topics to improve human physiological comfort without consuming excess energy to manage the temperature of the entire environment.

[0003] Functional textiles or wearable materials are generally made of fiber membranes. The moisture transport properties of fiber membranes greatly affect the physiological comfort of the human body. Water transport in traditional fiber membranes is bidirectional, resulting in an undesirable wet and sticky feeling. Therefore, there is an urgent need to develop new fiber membranes with directional water transport to achieve more effective moisture and heat management. Summary of the Invention

[0004] This embodiment of the present application provides a nano-silk fiber membrane with directional water transport and a preparation method thereof. The silk fiber membrane, prepared by electrospinning and subjected to secondary structural treatment, possesses hydrophilic, moisture-absorbing, and radiative cooling properties. OTS is then sprayed onto this silk fiber membrane in a single layer to form a network of water transport channels and a hydrophobic coating, achieving directional water transport while maintaining the original mechanical properties of the silk fiber membrane. Furthermore, the preparation method is environmentally friendly, simple, and scalable.

[0005] An embodiment of the present application provides a nanosilk fiber membrane with directional water transport, wherein the nanosilk fiber membrane is prepared by electrospinning, and a layer of uniformly and regularly arranged mesh hydrophobic coating is deposited on the surface of the single layer, and a mesh hydrophilic channel is formed on the surface of the single layer.

[0006] Preferably, the mesh hydrophobic coating is octadecyltrichlorosilane, and the coating area is 55% to 65%, specifically 60% of the hydrophobic coating.

[0007] The present invention also provides a method for preparing a nanosilk fiber membrane with directional water transport, which specifically includes the following steps:

[0008] S1 Preparation of hydrophilic silk fiber membrane

[0009] First, renewable pure silk fibroin is extracted from natural silk cocoons, and a silk fibroin film with a nanofiber structure is prepared by electrospinning. The secondary structure transformation is induced by methanol treatment to prepare a hydrophilic and hygroscopic silk fibroin fiber membrane.

[0010] Preparation of S2 mesh hydrophobic inner layer

[0011] Octadecyltrichlorosilane (OTS) was dissolved in n-hexane for later use, with the volume ratio of OTS to n-hexane being 1:20.

[0012] The surface of the nanosilk fiber membrane prepared in S1 is covered with a mesh glass fiber as a mask, and the pore density of the glass fiber mask is 55%~65%. A uniform layer of OTS is deposited on one side of the nanosilk fiber membrane as a hydrophobic coating by spraying.

[0013] After the OTS solution evaporates and dries, the mask is removed, and a network of hydrophilic channels is formed on the surface of the nanosilk fiber membrane, thereby preparing a silk fiber membrane with specific directional water transport.

[0014] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0015] 1. The present invention prepares a silk fibroin film with a nanofiber structure through electrospinning and induces a secondary structural transformation using methanol treatment, resulting in hydrophilic, hygroscopic, radiative cooling, and mechanical strength properties. Octadecyltrichlorosilane (OTS) is then sprayed onto the silk fibroin membrane using a spraying process, depositing a uniformly arranged, reticulated hydrophobic inner layer and reticulated water transport channels on one side. The resulting OTS-coated silk fibroin membrane exhibits directional water transport, with a directional water transport index (R) as high as 978%. It also retains the radiative cooling and mechanical strength properties of the original silk fibroin membrane, meeting the mechanical strength and other durability requirements required for practical applications.

[0016] 2. The preparation method provided by the present invention has simple process, mild reaction conditions, easy post-processing process, easy control, and is suitable for large-scale production.

[0017] 3. A homemade silk fiber membrane is used as the base membrane to prepare a fiber membrane with directional water transmission. No inorganic particles that increase reflectivity are added to the silk fiber membrane, and it is safe and comfortable for the human body.

[0018] 4. The staggered arrangement of the hydrophobic coating of octadecyltrichlorosilane of the present invention forms a network of water channels on the surface of the single layer of the silk fiber membrane, which can effectively conduct sweat secreted by the skin. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the structure of the nanosilk fiber membrane with directional water transport in this application;

[0020] Figure 2 Schematic diagram of directional water transport of the nanosilk fiber membrane with directional water transport in this application;

[0021] Figure 3This is the spectrum of the nanosilk fiber membrane in the 0.3-15μm band of this application;

[0022] Figure 4 This is a graph showing the test results of the one-way transmission index R value of 55% silk fibroin fiber membrane, 60% silk fibroin fiber membrane and 65% silk fibroin fiber membrane in this application.

[0023] 1-Nanosilk fiber membrane; 2-Hydrophobic coating; 3-Network hydrophilic channel. DETAILED DESCRIPTION

[0024] This embodiment of the present application provides a nano-silk fiber membrane with directional water transport and its preparation method. The silk fiber membrane, prepared by electrospinning and subjected to secondary structural treatment, possesses hydrophilic, moisture-absorbing, and radiative cooling properties. OTS is then sprayed onto this silk fiber membrane in a single layer to form a network of water transport channels, achieving directional water transport while maintaining the original mechanical properties of the silk fiber membrane. Furthermore, the preparation method is environmentally friendly, simple, and scalable.

[0025] The technical solution in the embodiments of the present application is to solve the above problems, and the overall idea is as follows:

[0026] Pure, renewable silk fibroin is extracted from natural silkworm cocoons and electrospun to create a nanofiber-like silk film. Methanol treatment is then used to induce a secondary structural transformation, resulting in hydrophilic and hygroscopic properties. Octadecyltrichlorosilane (OTS) is then sprayed onto the silk fibroin membrane, depositing a uniform, regularly arranged, hydrophobic inner layer on one side. The resulting OTS-coated silk fibroin membrane exhibits excellent directional water transport, with a directional water transport index (R) as high as 978%.

[0027] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods. Example 1

[0028] (1) Preparation of hydrophilic silk fiber membrane

[0029] ① Preparation of silk

[0030] 10 g of natural silk cocoons were cut into pieces, placed in a Na2CO3 solution with a concentration of 0.5 wt%, heated to 100°C for degumming, with a bath ratio of 70:1 and a degumming time of 40 min to 45 min; the degummed natural silk was repeatedly washed with distilled water and dried in an oven at 60°C to obtain degummed silk.

[0031] ② Preparation of pure silk fibroin

[0032] The degummed silk was dissolved in a formic acid (FA) / CaCl₂ solution (5 wt% CaCl₂, with the degummed silk accounting for 5 wt% of the total mixed solution). The mixed solution was then poured into a Petri dish and dried to form a film. The resulting film was then immersed in distilled water for 2 days and oven-dried at 60°C to obtain pure silk fibroin (SF).

[0033] ③ Preparation of nanosilk fiber membrane

[0034] The pure silk fibroin in step ② was dissolved in a formic acid FA solution to obtain a SF / FA electrospinning solution with a silk fibroin SF content of 15 wt%.

[0035] The electrospinning voltage was 20 kV, the spinning distance was 12 cm, the pushing speed was 2 mL / h, the drum speed was 110 rpm, the ambient temperature was 25°C, the spinning time was 24 h, and a spinning membrane was made. The spinning membrane was removed and immersed in a methanol solution for 10 min to obtain a nanosilk fiber membrane.

[0036] (2) Preparation of the mesh hydrophobic inner layer

[0037] Octadecyltrichlorosilane (OTS) was dissolved in n-hexane for later use, with the volume ratio of OTS to n-hexane being 1:20.

[0038] The surface of the nano-silk fiber membrane was covered with a mesh of glass fibers as a mask. The glass fiber mask had a pore density of 55%. A uniform layer of OTS was spray-coated on one side of the nano-silk fiber membrane 1 as a hydrophobic coating 2. After the OTS solution evaporated and dried, the mask was removed, forming a mesh of hydrophilic channels 3 on the surface of the nano-silk fiber membrane. This produced a silk fiber membrane with specific directional water transport, with the hydrophobic coating covering 55% of the membrane area.

[0039] Example 2

[0040] The pore density of the glass fiber mask in Example 1 was changed to 60%, and other conditions were the same as in Example 1, to obtain a silk fiber membrane with a hydrophobic coating area of ​​60%. Example 3

[0041] The pore density of the glass fiber mask in Example 1 was changed to 65%, and other conditions were the same as in Example 1, to obtain a silk fiber membrane with a hydrophobic coating area of ​​65%.

[0042] Infrared performance test of nanosilk fiber membrane products

[0043] Please refer to Figure 3The spectrum of the nanosilk fiber membrane in the 0.3-15μm band shows that the average reflectivity of the nanosilk fiber membrane to sunlight in the 0.3-2.5μm band reaches 95%, and the average emissivity at the 8-13μm "transparent atmospheric window" reaches 95%, which has excellent passive cooling properties.

[0044] Test of the one-way transmission index R value of 55% silk fibroin fiber membrane, 60% silk fibroin fiber membrane and 65% silk fibroin fiber membrane

[0045] Please refer to Figure 4 The R values ​​of 55% silk fiber membrane, 60% silk fiber membrane and 65% silk fiber membrane are 965%, 978% and 960% respectively, and the R values ​​are all above 600%, showing good one-way water transport capacity. This is because the network hydrophilic channels play a drainage role, allowing the liquid to be quickly transferred to the hydrophilic layer. This also shows that the existence of the network hydrophilic channels is more conducive to achieving ultra-fast one-way water transport.

[0046] Test on the cooling capacity of 55% silk fibroin membrane, 60% silk fibroin membrane and 65% silk fibroin membrane

[0047] 55% silk fibroin fiber membrane, 60% silk fibroin fiber membrane and 65% silk fibroin fiber membrane were placed indoors under simulated sunlight, and the real-time temperature of the silk fibroin fiber membranes with different hydrophobic areas was recorded using an infrared thermal camera.

[0048] The specific operation involved rapidly heating the fiber membrane under steady, continuous sunlight. Once the fiber membrane maintained stable fluctuations under continuous sunlight, 0.1 mL of water was added to the bottom of the membrane. The evaporative drying process of the wet fiber membranes was analyzed, yielding the following results: The drying times for the 55% silk fibroin membrane, the 60% silk fibroin membrane, and the 65% silk fibroin membrane were 7.5 minutes, 6.5 minutes, and 8 minutes, respectively. The 60% silk fibroin membrane rapidly transferred water to the upper layer, resulting in the shortest drying time and exhibiting superior water evaporation rates. The results are shown in Table 1.

[0049] Table 1 Test results of cooling capacity of 55% silk fibroin membrane, 60% silk fibroin membrane and 65% silk fibroin membrane

[0050] time 55% silk fiber membrane 60% silk fiber membrane 65% silk fiber membrane 0min 28.2 28.1 28.2 1~3 minutes 35.2 33.1 35.6 3.5 min (start adding 0.1 mL of water) 28.9 26.7 29 4~9.5min 29.0 25.8 29.3 9.8min 29.4 26.5 28.3 10min 29.0 32.8 29.0 10.5min 29.3 33.2 28.2 11min 34.8 33.1 29.3 11.5min 34.9 32.6 35 12~14 minutes 35.1 25.5 35.5

[0051] The 60% silk fiber membrane and the nanosilk fiber membrane obtained in step 3 were then placed on a heating platform at 37°C to simulate the condition of covering the human body. A solar simulator operating at AM1.5G was used to simulate 1 sun (100 mW / cm²). The bottom temperature of the fiber membrane was recorded using a thermocouple. After 5 minutes, 0.1 mL of water was added to the bottom of the fiber membrane. The membrane temperature dropped rapidly upon the addition of water. After 6.5 minutes, the temperature of the 60% silk fiber membrane increased rapidly and reached the temperature before the water addition, indicating that the water in the membrane had completely evaporated. The temperature of the nanosilk fiber membrane began to drop 2 minutes after the water addition, but did not begin to rise until the 15th minute, and it took 13 minutes for the water to completely evaporate.

[0052] The test results show that the 60% silk fiber membrane has faster water transfer and volatilization ability than the nano silk fiber membrane obtained in step ③.

[0053] Overall, the nanosilk fibroin membrane with directional water transport has both radiative cooling and directional water transport capabilities. The preparation method of the present invention features a simple process, mild reaction conditions, and easy and controllable post-processing, making it suitable for large-scale production. The resulting silk fibroin membrane with directional water transport meets the durability requirements of practical applications, including mechanical strength, while also being relatively safe and comfortable for the human body. It can be used to manufacture textiles, particularly functional fabrics and wearable materials.

[0054] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0055] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing a nanosilk fiber membrane with directional water transport, characterized in that: The specific steps include: S1 Preparation of hydrophilic silk fiber membrane First, pure, renewable silk fibroin is extracted from natural silk cocoons. A silk film with a nanofiber structure is prepared by electrospinning. Methanol treatment is then used to induce a secondary structural transformation, resulting in a hydrophilic and hygroscopic silk fibroin membrane. Preparation of S2 mesh hydrophobic inner layer Dissolve octadecyltrichlorosilane in n-hexane for later use, wherein the volume ratio of the octadecyltrichlorosilane to the n-hexane is 1:20; The surface of the nano-silk fiber membrane prepared in S1 is covered with a mesh of glass fibers as a mask, and a uniform layer of octadecyltrichlorosilane as a hydrophobic coating is deposited on one side of the nano-silk fiber membrane by spraying; After the octadecyltrichlorosilane solution evaporates and dries, the mask is removed, and a network of hydrophilic channels is formed on the surface of the nanosilk fiber membrane.

2. The method for preparing a nanosilk fiber membrane with directional water transport according to claim 1, wherein the pore density of the glass fiber in step S2 is 55% to 65%.

3. A nanosilk fiber membrane with directional water transport, characterized in that: Prepared according to the preparation method of any one of claims 1 to 2.

4. The nanosilk fiber membrane with directional water transport according to claim 3, characterized in that: The nanosilk fiber membrane with directional water transport is used for preparing textiles.

5. The nanosilk fiber membrane with directional water transport according to claim 4, characterized in that: The nanosilk fiber membrane with directional water transport is used for the preparation of functional fabrics and wearable textiles.

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