Core sheath fiber preparation method based on conical cavity microflow constraint

Abstract

The invention discloses a core-sheath fiber preparation method based on conical cavity microflow constraint, and belongs to the technical field of functional fiber material preparation. Aiming at the technical defects of Rayleigh instability of an existing dip coating method, edge effect and parameter sensitivity of a spraying method, dependence of a coaxial electrostatic spinning technology on a high-voltage electric field and an organic solvent and the like, a solid fiber core layer axially penetrates through a conical cavity filled with a hydrogel precursor solution; the conical cavity is used for physically constraining a micro-flow field, viscous force and pressure gradient are dominated, and Rayleigh instability is effectively inhibited, so that a stable and continuous liquid film is formed on the surface of the fiber; and cooling and solidifying the liquid film to finally obtain the core-sheath structure fiber with a uniform sheath layer. The thickness of the hydrogel sheath layer can be flexibly and accurately controlled by adjusting preparation parameters, and a reliable preparation way is provided for application of the high-performance core-sheath fiber in the fields of biomedicine and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fiber material preparation, and particularly relates to a preparation method of core-sheath fiber based on a conical cavity microflow constraint. BACKGROUND

[0002] Core-sheath structure fibers have broad application prospects in the fields of tissue engineering, drug release, intelligent sensing and separation and purification due to their unique rigid-flexible combination and adjustable functional characteristics. Among them, the configuration of taking hydrogel as a sheath layer and solid fiber as a core layer can perfectly combine the excellent mechanical properties of the core layer and the high specific surface area, biocompatibility and responsiveness of the sheath layer, and has become a research hotspot in recent years. However, it is still a technical problem that has not been solved to efficiently and controllably build a continuous and uniform hydrogel sheath layer on the surface of the solid fiber, especially to achieve this goal in a pure aqueous system without using organic solvents.

[0003] At present, the preparation of core-sheath fibers mainly depends on conventional processes such as dip-coating, spraying and coaxial electrospinning, but these methods all have obvious limitations. Although the dip-coating method is simple to operate, it only needs to immerse the core fiber into the coating solution and pull it out, but this process is easily affected by Rayleigh instability. When the fiber is pulled out of the solution, the liquid film attached to the surface will spontaneously shrink and break under the action of surface tension, forming a beaded or discontinuous droplet structure, which is difficult to obtain a uniform and continuous coating, resulting in poor quality and low reproducibility of the sheath layer, and it is difficult to meet the requirements of high-performance applications. The spraying method is a non-contact coating method, which atomizes the coating solution by air pressure and deposits it on the fiber surface, but the film formation effect is highly sensitive to operation parameters such as air pressure, spraying distance and flow rate, and the thickness of the coating is difficult to accurately control. In addition, the mist droplets hitting the curved surface of the fiber easily produce edge effects, causing uneven distribution of the sheath layer in the axial and circumferential directions, and it is difficult to obtain an ideal smooth structure. Although the coaxial electrospinning technology can realize the continuous preparation of micron or nanometer scale core-sheath fibers, it depends on a high-voltage electric field and usually requires volatile organic solvents as the system medium, which is not suitable for aqueous material systems.

[0004] Therefore, there is an urgent need in the art for a new preparation method that is non-electric field driven, aqueous compatible and can effectively suppress Rayleigh instability, so as to realize the accurate control of the thickness and morphology of the sheath layer of the core-sheath fiber, and meet the strict requirements of the biomedical and high-end functional material fields for structural fineness and performance stability. SUMMARY

[0005] The present application aims to overcome the shortcomings of the existing nuclear sheath fiber preparation technology, and proposes a nuclear sheath fiber preparation method based on conical cavity microflow constraint, to realize a fiber construction strategy with high uniformity, high continuity and friendliness to biological systems. The traditional dip coating method often leads to the formation of discontinuous and beaded structure defects in the sheath layer due to the influence of Rayleigh instability, which is difficult to meet the requirements of fiber structure integrity and fine control. The spraying method is extremely sensitive to process parameters and is disturbed by edge effects, making it difficult to stably control and uniform the thickness of the sheath layer, which limits its application in precise fiber construction. In addition, existing technologies such as coaxial electrospinning rely on high-voltage electric field and organic solvents, which not only have strict requirements on equipment conditions, but also are difficult to apply to water phase systems sensitive to biologically active ingredients. Therefore, the present application proposes a mild preparation scheme without electric field driving and fully compatible with water phase systems, which realizes the stable construction of nuclear sheath structure at the fluid interface through the microscale constraint of fluid generated by the conical mold, and is especially suitable for application scenarios involving the maintenance of biological activity or cell compatibility requirements.

[0006] To achieve the above object, the present application provides the following technical scheme: A nuclear sheath fiber preparation method based on conical mold microflow constraint, comprising the following steps: (1) providing a solid fiber as a core layer; (2) providing a mold, the mold having a conical cavity, the conical cavity containing a thermoreversible hydrogel precursor solution, the bottom diameter of the conical cavity being smaller than the top diameter, and an outlet being provided at the center of the bottom of the conical cavity for the fiber to pass out; the thermoreversible hydrogel precursor solution is in a flowing state when the temperature is higher than the phase transition temperature; (3) making the solid fiber pass through the inside of the conical cavity along the axial direction of the conical cavity; wherein the structure of the conical cavity is configured such that when the solid fiber passes through, the viscous force and pressure gradient generated by the conical structure of the solid fiber to the hydrogel precursor solution are sufficient to suppress Rayleigh instability, thereby forming a uniform and continuous liquid film on the surface of the solid fiber; (4) cooling the fiber covered with a uniform liquid film to make the temperature of the liquid film below the phase transition temperature to solidify, thereby forming a hydrogel sheath layer on the surface of the solid fiber, and obtaining a nuclear sheath fiber.

[0007] Further, the thickness of the hydrogel sheath layer can be flexibly and accurately controlled by the following process parameters: 1) the concentration of the thermoreversible hydrogel precursor solution; 2) the temperature of the thermoreversible hydrogel precursor solution; 3) the drawing speed of the solid fiber; 4) the size parameters of the conical cavity, including the outlet diameter, the taper, and the length of the cone.

[0008] Furthermore, the mold is preferably a conical capillary, such as a conical glass capillary.

[0009] Furthermore, the solid fiber can be any material, and can be selected according to the subsequent application scenario. For example, the material of the solid fiber can be polyethylene terephthalate, polybutylene terephthalate, polypropylene, polyethylene, nylon, polyurethane, polyacrylonitrile, polystyrene, silk protein, collagen, bovine serum albumin, cotton, or linen.

[0010] Further, the thermally reversible hydrogel precursor solution is an aqueous solution of at least one of agarose, carrageenan, gellan gum, gelatin, or derivatives thereof. Further, to ensure that the viscous force and pressure gradient generated by the conical structure on the hydrogel precursor solution are sufficient to suppress Rayleigh instability and form a uniform and continuous liquid film on the surface of the solid fiber, the concentration range of the thermally reversible hydrogel precursor solution is 2 wt%-60 wt%, its temperature within the conical cavity is the phase transition temperature of the hydrogel precursor up to 100°C, and its viscosity is maintained at no less than 40 mPa·s by adjusting the concentration and temperature.

[0011] Furthermore, the outlet diameter of the conical cavity is not less than the diameter of the solid fiber; the taper is not less than 19:50; and the cone length of the conical cavity is not less than 2 mm. The drawing speed of the solid fiber is 0.4 m / min-8 m / min.

[0012] The present invention further provides an apparatus for carrying out the method, comprising: The mold is configured to have a conical cavity for containing a thermally reversible hydrogel precursor solution, the bottom diameter of the conical cavity being smaller than its top diameter, and an outlet for fiber passage is provided at the center of the bottom of the conical cavity, allowing solid fibers to pass through axially. A feeding system is used to supply the thermally reversible hydrogel precursor solution to the mold; A heating and temperature control system is used to maintain the thermally reversible hydrogel precursor solution at a temperature above its phase transition temperature. A drawing system is used to guide and control the solid fibers to pass axially through the conical cavity at a set speed.

[0013] The present invention further provides a nuclear sheath fiber, which is prepared by the aforementioned method.

[0014] The beneficial effects of this invention are as follows: (1) The method for preparing core sheath fibers based on microfluidic constraint of conical cavity provided by the present invention effectively suppresses Rayleigh instability by means of microfluidic constraint effect of conical cavity, with viscous force and pressure gradient as the main factors, fundamentally solving the problems of liquid film breakage and bead formation, and realizing the uniformity and stability of coating.

[0015] (2) The entire process does not require organic solvents and can be completed in a pure aqueous system, which is perfectly compatible with the loading of bioactive substances and opens up the way for biomedical applications.

[0016] (3) This method does not require complex high-voltage electrostatic field equipment and is simple and safe to operate. The thickness of the sheath can be precisely controlled by adjusting conventional parameters such as concentration, temperature and speed. It has good repeatability and is easy to scale up.

[0017] (4) The prepared core-sheath fiber combines the mechanical strength of a solid core layer with the high specific surface area and functional adjustability of a hydrogel sheath layer, providing an ideal material platform for achieving advanced functions such as drug sustained release and chromatographic separation. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the fabrication of nuclear sheath fibers based on conical cavity microfluidic constraint.

[0019] In the diagram: 1. Solid fiber, 2. Conical capillary, 3. Hydrogel sheath.

[0020] Figure 2 This is a graph showing the relationship between agarose solution concentration, stretching speed, and fiber sheath thickness.

[0021] Figure 3 These are optical microscope images of nuclear sheath fibers with different sheath thicknesses.

[0022] Figure 4 It is a graph showing the relationship between the inner diameter of the mold outlet, the length of the cone, the fiber diameter, and the thickness of the fiber sheath. Detailed Implementation

[0023] The present invention is illustrated by the following embodiments, but the present invention is not limited to the following embodiments.

[0024] See attached document Figure 1 The method of this invention is used to prepare core-sheath fibers with agarose hydrogel as the sheath layer and solid fibers as the core layer. The specific steps are as follows: (1) Provide a solid fiber as the core layer; (2) A mold is provided, the mold having a conical cavity containing a thermally reversible hydrogel precursor solution, the bottom diameter of the conical cavity being smaller than its top diameter, and an outlet for fibers to pass through being provided at the center of the bottom of the conical cavity; the thermally reversible hydrogel precursor solution is in a flowing state when it is above its phase transition temperature. (3) The solid fiber passes through the interior of the conical cavity along the axial direction; wherein the structure of the conical cavity is configured such that when the solid fiber passes through, the viscous force and pressure gradient generated by its conical structure on the hydrogel precursor solution are sufficient to suppress Rayleigh instability, thereby forming a uniform and continuous liquid film on the surface of the solid fiber. (4) After the fiber with a uniform liquid film on its surface leaves the mold, the fiber covered with a uniform liquid film is cooled (immersed in a cooling medium, which can be air, cooling oil, or cooling water) so that the temperature of the liquid film drops below its phase transition temperature before it deforms due to unstable environmental factors, thereby solidifying to form a hydrogel sheath layer, and finally obtaining a core-sheath fiber with a uniform structure.

[0025] Example 1: (1) Polyethylene terephthalate (PET) fiber with a diameter of 20 μm is used as the core layer; (2) Add agarose powder to deionized water and heat and stir at 90°C for 6 hours to obtain a 6 wt% agarose aqueous solution; (3) An agarose aqueous solution was added to a conical glass capillary with an outlet inner diameter of 100 μm, a cone length of 3 mm, and a taper of 43:100, and the temperature was maintained at 80°C. PET fibers were passed through the conical glass capillary at a speed of 3 m / min to obtain PET fibers with an agarose liquid film. The liquid film gradually cooled and solidified in the air to form a uniform agarose hydrogel sheath layer, which was then collected by a collecting roller to obtain agarose-PET core-sheath fibers with a 7 μm agarose hydrogel as the sheath layer and PET fibers as the core layer.

[0026] like Figure 2 As shown, by increasing the concentration of agarose solution, the thickness of the prepared core sheath fiber sheath layer gradually increases; by increasing the drawing speed of the collecting roller, the thickness of the prepared core sheath fiber sheath layer gradually increases, and the sheath layer thickness tends to stabilize when the drawing speed exceeds 5 m / min. Figure 3 As shown, agarose-PET core-sheath fibers with sheath thicknesses of 5 μm, 8 μm, and 12 μm were prepared using agarose solutions with concentrations of 4%, 5%, and 7%.

[0027] Example 2: (1) Polyethylene terephthalate (PET) fiber with a diameter of 20 μm is used as the core layer; (2) Add agarose powder to deionized water and heat and stir at 90°C for 6 hours to obtain a 6wt% agarose aqueous solution; (3) An agarose aqueous solution was added to a conical glass capillary with an outlet inner diameter of 100 μm, a cone length of 3 mm, and a taper of 21:50, and the temperature was maintained at 80°C. PET fibers were passed through the conical glass capillary at a speed of 3 m / min to obtain PET fibers with an agarose liquid film. The fibers were then immersed in cooling oil, and the liquid film gradually cooled and solidified in the cooling oil to form a uniform agarose hydrogel sheath. The fibers were then collected by a collecting roller to obtain agarose-PET core-sheath fibers with a 10 μm agarose hydrogel sheath and PET fibers as the core layer.

[0028] like Figure 4 As shown, by increasing the inner diameter of the mold outlet, the thickness of the prepared core sheath fiber sheath layer gradually increases; by increasing the length of the mold cone, the thickness of the prepared core sheath fiber sheath layer gradually decreases; when the inner diameter of the mold outlet is fixed at 100 μm, by increasing the diameter of the solid fiber, the thickness of the prepared core sheath fiber sheath layer gradually decreases.

[0029] Example 3: (1) Polyethylene terephthalate (PET) fiber with a diameter of 20 μm is used as the core layer; (2) Add gelatin particles to deionized water and heat and stir at 50°C for 4 hours to obtain a gelatin aqueous solution of 400 mg / mL; (3) A gelatin aqueous solution was added to a conical glass capillary with an outlet inner diameter of 100 μm, a cone length of 3 mm, and a taper of 43:100, and the temperature was maintained at 40°C. PET fibers were passed through the conical glass capillary at a speed of 1.6 m / min to obtain PET fibers with a gelatin liquid film. The liquid film gradually cooled and solidified in the air to form a uniform gelatin hydrogel sheath layer, which was then collected by a collecting roller to obtain gelatin-PET core-sheath fibers with a 35 μm gelatin hydrogel sheath layer and PET fibers as the core layer.

[0030] Example 4: (1) Collagen fibers with a diameter of 50 μm were used as the core layer; (2) Add gelatin particles to deionized water and heat and stir at 50°C for 4 hours to obtain a gelatin aqueous solution of 400 mg / mL; (3) A gelatin aqueous solution was added to a conical glass capillary with an outlet inner diameter of 200 μm, a cone length of 3 mm, and a taper of 38:100, and the temperature was maintained at 40°C. Collagen fibers were passed through the conical glass capillary at a speed of 1.6 m / min to obtain PET fibers with a gelatin liquid film. The fibers were then immersed in cooling water, and the liquid film gradually cooled and solidified in the cooling water to form a uniform gelatin hydrogel sheath. The fibers were then collected by a collecting roller to obtain gelatin-collagen core-sheath fibers with a 65 μm gelatin hydrogel sheath and collagen fibers as the core layer.

[0031] Example 5: (1) A nylon fiber with a diameter of 60 μm was used as the core layer; (2) Add agarose powder to deionized water and heat and stir at 90°C for 6 hours to obtain a 6 wt% agarose aqueous solution; (3) Add agarose aqueous solution to a conical glass capillary with an outlet inner diameter of 100 μm, a cone length of 3 mm, and a taper of 43:100, and maintain the temperature at 80°C. Pass nylon fibers through the conical glass capillary at a speed of 3 m / min to obtain nylon fibers with an agarose liquid film. The liquid film gradually cools and solidifies in the air to form a uniform agarose hydrogel sheath layer, which is then collected by a collecting roller to obtain agarose-nylon core-sheath fibers with a 5 μm agarose hydrogel sheath layer and a nylon fiber core layer.

[0032] Example 6: (1) Using nylon fibers with a diameter of 80 μm as the core layer; (2) Add gelatin particles to deionized water and heat and stir at 50°C for 4 hours to obtain a gelatin aqueous solution of 400 mg / mL; (3) A gelatin aqueous solution was added to a conical glass capillary with an outlet inner diameter of 200 μm, a cone length of 3 mm, and a taper of 38:100, and the temperature was maintained at 40°C. Nylon fibers were passed through the conical glass capillary at a speed of 3 m / min to obtain nylon fibers with a gelatin liquid film. The fibers were then immersed in cooling water, and the liquid film gradually cooled and solidified in the cooling water to form a uniform gelatin hydrogel sheath. The sheath was then collected by a collecting roller to obtain gelatin-nylon core-sheath fibers with a 50 μm gelatin hydrogel as the sheath and nylon fibers as the core.

[0033] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing core-sheath fibers based on conical cavity microfluidic constraint, characterized in that, Includes the following steps: (1) Provide a solid fiber as the core layer; (2) A mold is provided, the mold having a conical cavity containing a thermally reversible hydrogel precursor solution, the bottom diameter of the conical cavity being smaller than its top diameter, and an outlet for fibers to pass through being provided at the center of the bottom of the conical cavity; the thermally reversible hydrogel precursor solution is in a flowing state when it is above its phase transition temperature. (3) The solid fiber passes through the interior of the conical cavity along the axial direction; wherein the structure of the conical cavity is configured such that when the solid fiber passes through, the viscous force and pressure gradient generated by its conical structure on the hydrogel precursor solution are sufficient to suppress Rayleigh instability, thereby forming a uniform and continuous liquid film on the surface of the solid fiber. (4) Cool the fiber covered with a uniform liquid film to reduce the temperature of the liquid film to below the phase transition temperature and solidify it, thereby forming a hydrogel sheath layer on the surface of the solid fiber to obtain a core-sheath fiber.

2. The method according to claim 1, characterized in that, The thermally reversible hydrogel precursor solution is an aqueous solution of at least one of agarose, carrageenan, gellan gum, and gelatin; the concentration range of the thermally reversible hydrogel precursor solution is 2wt%-60wt%, its temperature in the conical cavity is from the phase transition temperature of the hydrogel precursor to 100℃, and the viscosity of the thermally reversible hydrogel precursor solution is not less than 40 mPa·s.

3. The method according to claim 1, characterized in that, The outlet diameter of the conical cavity is not less than the diameter of the solid fiber; the taper is not less than 19:50; and the cone length of the conical cavity is not less than 2 mm.

4. The method according to claim 1, characterized in that, The drawing speed of solid fibers is 0.4 m / min-8 m / min.

5. The method according to claim 1, characterized in that, As the solid fibers axially pass through the conical cavity, the thickness of the hydrogel sheath is controlled by adjusting process parameters; the process parameters include at least one of the following: 1) The concentration of the thermally reversible hydrogel precursor solution; 2) The temperature of the thermally reversible hydrogel precursor solution; 3) The drawing speed of the solid fiber; 4) The outlet diameter of the conical cavity; 5) The taper of the conical cavity; 6) The cone length of the cone-shaped cavity.

6. The method according to claim 1, characterized in that, The mold is a conical capillary tube.

7. An apparatus for carrying out the method as described in any one of claims 1-6, characterized in that, include: The mold is configured to have a conical cavity for containing a thermally reversible hydrogel precursor solution, the bottom diameter of the conical cavity being smaller than its top diameter, and an outlet for fiber passage is provided at the center of the bottom of the conical cavity, allowing solid fibers to pass through axially. A feeding system is used to supply the thermally reversible hydrogel precursor solution to the mold; A heating and temperature control system is used to maintain the thermally reversible hydrogel precursor solution at a temperature above its phase transition temperature. A drawing system is used to guide and control the solid fibers to pass axially through the conical cavity at a set speed.

8. The apparatus according to claim 7, characterized in that, The mold is a conical glass capillary.

9. A nuclear sheath fiber, characterized in that, The nuclear sheath fiber is prepared by any one of the methods described in claims 1-6.

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