A confined liquid surface steady electrospinning device and method

Abstract

The application relates to a limited liquid surface steady flow electrospinning device and method, which comprises a limited nozzle, a liquid supply system, a receiving device and a high-voltage generator. The limited nozzle comprises a sintered metal porous plate and a shell covering the sintered metal porous plate, the sintered metal porous plate has a three-dimensional mesh micro-pore structure communicating with each other in the inside, and the shell is a sleeve structure with an upper opening and a lower opening. The liquid supply system is connected with the sintered metal porous plate through a liquid guide pipe. The receiving device is located directly below the sintered metal porous plate. The positive electrode of the high-voltage generator is electrically connected with the sintered metal porous plate. The steady flow pneumatic system comprises an air source, a suction port and a ring-shaped air knife connected with the air source through a gas conveying pipeline. The application solves the fluid instability problem of the existing needleless electrospinning from the root of fluid dynamics by deep cooperation of the porous static capillary limitation and the dynamic reverse steady flow, and realizes the stable batch preparation of the micro-nano fiber with no dripping, high orientation and high uniformity.

Description

Technical Field

[0001] This invention belongs to the field of electrospinning technology, and in particular relates to a confined liquid surface stabilizing electrospinning device and method. Background Technology

[0002] Electrospinning is one of the most direct and effective methods for preparing micro / nano continuous fibers. Traditional single-capillary needle electrospinning suffers from extremely low production capacity due to the limited number of jets per orifice, severely restricting its industrial application. To address this, needle-free electrospinning technology has been developed. Its key feature is the use of rotating rollers, metal wires, or disc nozzles as generators to spontaneously form multiple Taylor cones on a broad surface of the polymer solution, thereby significantly increasing fiber yield.

[0003] However, while pursuing high throughput, existing needleless electrospinning devices introduce the fatal flaw of a "free liquid surface," making the spinning process highly susceptible to instability. First, the lack of physical confinement in the open, large liquid surface makes solvent evaporation extremely uncontrollable, resulting in drastic local viscosity fluctuations and highly random, non-uniform Taylor cone formation. Second, in mainstream top-down or lateral liquid supply layouts, the lack of an effective fluid stabilization mechanism allows high-viscosity spinning solutions to easily accumulate macroscopically at the nozzle tip under gravity or centrifugal force. This uncontrolled fluid inevitably forms large droplets that drip downwards, not only wasting raw materials and contaminating the fiber membrane but also potentially triggering partial discharges, completely disrupting the continuity of spinning.

[0004] To overcome the process defects caused by free liquid surfaces and fluid instability, researchers have attempted to intervene technically by introducing physical fields such as gas fields. However, existing solutions have failed to address the root cause of the problem in fluid dynamics. For example, Chinese Patent 202511192383.1 discloses a needleless disc nozzle combined with airflow assistance. Although it has an airflow assistance device, it still relies on the free liquid surface at the edge of the disc. The airflow is only used for fiber stretching at the end and cannot confine or stabilize the liquid flowing at the edge, resulting in severe dripping problems. Chinese Patent 202411712068.2 discloses a hot airflow-assisted slit-type bubble electrospinning device, including a hot airflow channel, a slit-type metal solution channel, a bubble tube, and an electrostatic generator. The slit-type metal solution channel passes through and is fixed to the hot airflow channel, and the bubble tube is fixed inside the solution channel. This device attempts to improve the fluid by utilizing the slit channel, but the bubble surface itself is an extremely active dynamic free liquid surface, making size and flow state control extremely difficult and prone to rupture and instability. Chinese Patent 202511121996.6 discloses an atmosphere-controllable needleless electrospinning device, including electrode wires, a brush liquid tank, a DC high-voltage power supply, a metal plate, an air inlet, a slide rail, an air outlet, and a sealed outer cover; the air inlet can reciprocate on the slide rail. This device achieves controllable spinning atmosphere through the sealed outer cover, allowing the introduction of gases with different temperatures, humidity levels, and compositions, and even adjusting the air pressure. Its advantages include providing a stable spinning environment for hygroscopic materials or non-volatile solvents, reducing beading defects, and enabling one-step preparation of porous fibers; however, the device requires a precise sealing and gas control system, resulting in higher costs and complex process stability control. Chinese Patent 202511687917.8 discloses an ion gun-assisted needleless electrospinning device and method, including electrode wires, a brush liquid tank, a DC high-voltage power supply, a metal plate, and an ion gun; the ionization head inside the ion gun is connected to the high-voltage power supply, and the nozzle is connected to compressed air. This method generates positive and negative ions by ionizing air with an ion gun, neutralizing the surface charge of the fibers and suppressing jet instability. Its advantage lies in effectively solving the problems of uneven fiber deposition and poor adhesion caused by charge accumulation, without requiring chemical modification; however, it adds ion generation equipment, requiring precise matching of ion density and air velocity, which may affect fiber uniformity under certain conditions. Furthermore, Chinese patents 202511121996.6 and 202511687917.8 only modify the external environment or electrostatic field, without physically confining the fluid on the generator surface. In addition, although existing electrostatic melt-blown spinning technology introduces co-directional airflow stretching, its top-down, coarse liquid supply also lacks a microscopic confinement structure, easily leading to frequent droplet defects at high liquid supply rates; moreover, the abrupt intervention of high-speed co-directional airflow exacerbates the flow field disturbance at the interface, resulting in violent jet whipping, difficulty in stabilizing the flow, poor fiber orientation, and complex process control.

[0005] In summary, how to improve spinning efficiency while achieving effective confinement of the liquid surface, stable control of the fluid, and precise regulation of the jet are the core technical challenges that urgently need to be solved in this field. Summary of the Invention

[0006] The main objective of this invention is to address the aforementioned deficiencies in the prior art by providing a confined liquid surface stabilizing electrospinning device and method. Through the deep synergy of porous static capillary confinement and dynamic reverse flow stabilization, the fluid instability problem in existing needleless electrospinning is solved from the root of fluid dynamics, thereby achieving stable mass production of drip-free, highly oriented, and highly uniform micro / nano fibers.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A confined liquid surface stabilizing electrospinning device, comprising:

[0009] A confined nozzle, comprising a sintered metal porous plate and a shell covering the sintered metal porous plate, wherein the sintered metal porous plate has an interconnected three-dimensional mesh microporous structure inside, and the shell is a sleeve structure with openings at the top and bottom to expose the micropores on the upper and lower surfaces of the sintered metal porous plate.

[0010] The liquid supply system is connected to the sintered metal porous plate through a liquid guide pipe and is used to inject spinning solution into the three-dimensional mesh microporous structure inside the sintered metal porous plate.

[0011] A receiving device, located directly below the sintered metal porous plate, is used to receive nanofibers formed by electrospinning.

[0012] A high-voltage generator, the positive terminal of which is electrically connected to the sintered metal porous plate, and the negative terminal is grounded or electrically connected to the receiving device;

[0013] The steady-flow pneumatic system includes an air source and a suction port and an annular air knife connected to it via an air supply pipe. The suction port is located directly above the sintered metal porous plate and connected to the upper part of the outer shell. The annular air knife is located directly below the sintered metal porous plate, and the air outlet of the annular air knife faces the lower surface of the sintered metal porous plate.

[0014] Preferably, the average pore size of the sintered metal porous plate is 25-50 nm, and the porosity is 30%-70%.

[0015] Preferably, the angle between the airflow direction at the outlet of the annular air knife and the vertical direction is 0°-30°, and the airflow pressure during operation is 0.1-0.8MPa.

[0016] Preferably, the working negative pressure adjustment range of the suction port is -0.6 to 0 MPa.

[0017] Preferably, the liquid supply system has a liquid supply rate adjustable range of 5-30 ml / h.

[0018] Preferably, the output voltage adjustment range of the high voltage generator is 0-100kV.

[0019] Preferably, the receiving device is a metal collecting plate or a collecting roller, and the vertical receiving distance between the receiving device and the sintered metal porous plate is 10-50cm.

[0020] The present invention also provides a method for confined liquid surface steady-flow electrospinning, which is implemented using the above-mentioned confined liquid surface steady-flow electrospinning device, and includes the following steps:

[0021] S1: Prepare polymer spinning solution;

[0022] S2: The prepared polymer spinning solution is delivered to the sintered metal porous plate through the liquid supply system, so that the spinning solution is distributed in the three-dimensional network microporous structure of the sintered metal porous plate under capillary action.

[0023] S3: Turn on the high voltage generator to form a high voltage electrostatic field between the sintered metal porous plate and the receiving device;

[0024] S4: Activate the steady flow pneumatic system, generate a reverse airflow from bottom to top through the annular air knife, and at the same time form a reverse steady flow gas field through the suction port to penetrate the sintered metal porous plate.

[0025] S5: Under the synergistic effect of high-voltage electrostatic field and reverse steady-flow gas field, the spinning solution forms Taylor cones at the micropores on the lower surface of the sintered metal porous plate and generates multiple jets. After the jets are stretched and refined and the solvent evaporates and solidifies, they form nanofibers and are finally deposited on the receiving device.

[0026] This invention provides a confined liquid surface stabilization electrospinning device and method, which has the following beneficial effects:

[0027] 1. The sintered metal porous plate of this invention has an interconnected three-dimensional network microporous structure inside. Under the action of a strong electric field, each micropore on the lower surface of the sintered metal porous plate can form an independent spinning site, realizing true arrayed multi-jet spinning and significantly improving fiber production capacity. At the same time, the physical confinement effect of the micropores makes the formation position of the Taylor cone fixed and the number controllable, avoiding the random generation of Taylor cones in open liquid surfaces. This ensures the uniformity of the initial state of each jet from the source, so that the final prepared fiber has high uniformity, thereby realizing the stable batch preparation of highly uniform nanofibers.

[0028] 2. This invention constructs a dual anti-drip system through the deep synergy of "static capillary confinement + dynamic reverse flow stabilization". The dual mechanism completely blocks the dripping of liquid under high-throughput liquid supply, solves the pain point of fluid instability in the top-down spinning system, and realizes the long-term continuous and stable operation of the spinning process.

[0029] 3. The bottom-up counter-current stable airflow force constructed by the annular air knife and suction port of this invention can also apply a uniform axial reverse tensile force to the primary jet, which is coaxial with the tensile direction of the electric field force. This avoids flow field disturbances caused by lateral airflow or high-speed airflow in the same direction, and effectively suppresses uncontrolled whipping of the jet during flight. At the same time, the axial tensile effect can further refine the fiber diameter, accelerate solvent evaporation, reduce fiber stranding and adhesion, significantly improve fiber orientation and forming quality, and can prepare highly oriented nanofibers. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the electrospinning apparatus for confined liquid surface stabilization of the present invention.

[0031] Figure 2 This is a cross-sectional view of the electrospinning apparatus for confined liquid surface stabilization according to the present invention.

[0032] Figure 3 This is a schematic diagram of the sintered metal porous plate of the present invention.

[0033] In the diagram: 1. High-pressure generator; 2. Gas pipeline; 3. Gas source; 4. Spinning direction; 5. Receiving device; 6. Suction port; 7. Sintered metal porous plate; 8. Liquid supply system; 9. Annular air knife; 10. Airflow direction. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0035] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] Reference Figures 1-3 The present invention provides a confined liquid surface stabilizing electrospinning device, comprising:

[0038] The confined nozzle includes a sintered metal porous plate 7 and a shell covering the sintered metal porous plate 7. The sintered metal porous plate 7 has an interconnected three-dimensional network microporous structure inside (i.e., the sintered metal porous plate 7 has several interconnected nanoscale capillary channels inside, and several uniformly distributed micropores are formed on the surface of the sintered metal porous plate 7). The shell is a sleeve structure with openings at the top and bottom to expose the micropores on the upper and lower surfaces of the sintered metal porous plate 7.

[0039] The liquid supply system 8 is connected to the sintered metal porous plate 7 through a liquid guide pipe and is used to inject spinning solution into the three-dimensional mesh microporous structure inside the sintered metal porous plate 7.

[0040] The receiving device 5 is located directly below the sintered metal porous plate 7 and is used to receive nanofibers formed by electrospinning.

[0041] The high-voltage generator 1 has its positive terminal electrically connected to the sintered metal porous plate 7, and its negative terminal grounded or electrically connected to the receiving device 5.

[0042] The steady-flow pneumatic system includes an air source 3 and a suction port 6 and an annular air knife 9 connected to it via an air supply pipe 2. The suction port 6 is located directly above the sintered metal porous plate 7 and is connected to the upper part of the outer shell. The annular air knife 9 is located directly below the sintered metal porous plate 7, and the air outlet of the annular air knife 9 faces the lower surface of the sintered metal porous plate 7.

[0043] In use, the liquid supply system 8 injects polymer spinning solution into the three-dimensional network microporous structure inside the sintered metal porous plate 7 through the liquid guide tube. The spinning solution is uniformly distributed in the nanoscale capillary channels within the sintered metal porous plate 7 under capillary action. Since the positive electrode of the high-voltage generator 1 is electrically connected to the sintered metal porous plate 7, and the negative electrode is grounded or electrically connected to the receiving device 5, a strong electric field is formed between the sintered metal porous plate 7 and the receiving device 5. The spinning solution at the micropores on the lower surface of the sintered metal porous plate 7 is subjected to electric field force in this strong electric field. When the electric field force overcomes the surface tension of the solution, Taylor cones are formed at numerous micropores, generating multiple jets. During their downward movement, the jets evaporate and solidify to form nanofibers, which are ultimately received by the receiving device 5. Figure 1 In the diagram, number 4 indicates the spinning direction, and number 10 indicates the airflow direction.

[0044] The sintered metal porous plate 7 of this invention has an interconnected three-dimensional network microporous structure inside. Under the action of a strong electric field, each micropore on the lower surface of the sintered metal porous plate 7 can form an independent spinning site, realizing true arrayed multi-jet spinning and significantly improving fiber production capacity. At the same time, the physical confinement effect of the micropores makes the formation position of the Taylor cone fixed and the number controllable, avoiding the random generation of Taylor cones in open liquid surfaces. This ensures the uniformity of the initial state of each jet from the source, so that the final prepared fiber has high uniformity, thereby realizing the stable batch preparation of highly uniform nanofibers.

[0045] Furthermore, the three-dimensional network microporous structure of the sintered metal porous plate 7 generates strong capillary pressure, which can confine the spinning solution within the micropores, balancing the liquid column pressure generated by gravity and constructing a static confinement interface to prevent the spinning solution from dripping freely under gravity. Specifically, according to the Yang-Laplace equation, capillary pressure is inversely proportional to the micropore radius and directly proportional to the solution surface tension and the cosine of the contact angle. When the micropore diameter of the sintered metal porous plate 7 is sufficiently small, the generated capillary pressure is sufficient to balance the liquid column pressure caused by gravity, thus allowing the spinning solution to remain stably within the micropores even in the absence of an electric field or fluctuations in the liquid supply, preventing it from dripping freely.

[0046] The invention also includes a flow-stabilizing pneumatic system, comprising an air source 3 and a suction port 6 and an annular air knife 9 connected to it via an air supply pipe 2. The suction port 6 is located directly above the sintered metal porous plate 7 and connected to the upper part of the outer shell. The annular air knife 9 is located directly below the sintered metal porous plate 7, with its outlet facing the lower surface of the sintered metal porous plate 7. During the jet stretching process, the upward lifting effect of the annular air knife 9 and the upward adsorption effect of the suction port 6 combine to generate a reverse flow-stabilizing airflow force from bottom to top. This force applies an upward shear lifting force to the spinning solution on the lower surface of the sintered metal porous plate 7, thereby counteracting the dripping tendency caused by liquid accumulation or gravitational disturbance.

[0047] In summary, this invention constructs a dual anti-drip system through the deep synergy of "static capillary confinement + dynamic reverse flow stabilization". The dual mechanism completely blocks dripping under high-flux liquid supply, solves the pain point of fluid instability in top-down spinning system, and realizes long-term continuous and stable operation of the spinning process.

[0048] Furthermore, it should be noted that the bottom-up counter-current steady flow force constructed by the annular air knife 9 and the suction port 6 of this invention can also apply a uniform axial reverse tensile force to the primary jet, which is coaxial with the tensile direction of the electric field force. This avoids flow field disturbances caused by lateral airflow or high-speed airflow in the same direction, and effectively suppresses uncontrolled whipping of the jet during flight. At the same time, the axial tensile effect can further refine the fiber diameter, accelerate solvent evaporation, reduce fiber stranding and adhesion, significantly improve fiber orientation and forming quality, and can prepare highly oriented nanofibers.

[0049] Specifically, achieving the desired effect requires proper parameter control. The flow rate of the reverse steady-flow airflow is low and constant. This speed is sufficient to remove the solvent, but far from enough to overcome the traction force of the electric field on the molecules. During the spinning process, the flight of nanofibers in space is mainly affected by three forces: the downward electric field force F1, the downward gravity force F2, and the upward axial force F3 generated by the bottom-up airflow. The driving voltage of electrospinning is usually as high as tens of thousands of volts (e.g., 0-100kV). The electric field traction force on the charged jet is extremely large in value. In contrast, the bottom-up reverse steady-flow airflow we designed is a low-speed steady flow (usually 0.5-2m / s). The axial force F3 it generates is much smaller than the electric field force F1. As long as the system satisfies the condition that the net force is greater than zero (F1+F2-F3>0), the overall trend of the jet moving towards the collecting plate will not be reversed (i.e., it will not be blown away). The reverse steady-flow airflow exerts a uniform axial reverse tension on the high-speed flying fiber, causing solvent evaporation and secondary fiber stretching. The reverse airflow accelerates solvent evaporation, forcing the fiber to complete complete phase separation and solidification before reaching the collection plate. The fiber simply moves against the medium in the flow channel, and this additional stress field helps to further refine the fiber. Conversely, if the airflow is also from top to bottom (with the wind), the whipping of the jet may be intensified by local turbulence, resulting in extremely poor fiber directionality.

[0050] In this embodiment, a liquid inlet is provided on the side of the outer shell. The liquid inlet is connected to the liquid supply system 8 through a polytetrafluoroethylene (PTFE) liquid guiding pipe. After the spinning solution is injected from the side liquid inlet, the area near the inlet is saturated first, while the area further away remains dry, thus forming a capillary pressure gradient driven by the difference in saturation. Under the action of this gradient, the spinning solution permeates along the microporous network into the unsaturated area, and the wetting front gradually advances. When all the micropores on the entire plate surface are saturated with spinning solution, the radius of curvature of the meniscus of each micropore outlet on the lower surface of the sintered metal porous plate 7 tends to be consistent, achieving capillary equilibrium, and the spinning solution is spatially uniformly distributed. The realization of continuous spinning depends on dynamic equilibrium. The liquid supply system 8 continuously injects at a constant rate, and the spinning solution at the tip of the micropore outlet is continuously consumed under the action of electric field force and airflow shear force. When the liquid supply rate is equal to the sum of the consumption rates of all micropores, the system enters a steady state, the saturation of the spinning solution in the plate is constant, and the liquid level height of each micropore does not change with time. The capillary network of the sintered metal porous plate 7 can also buffer the minute pulsations of the injection pump, maintaining a dynamic balance between liquid supply and consumption. Of course, the liquid supply method can also be to pass through the middle of the suction port 6 and extend to the middle of the sintered metal porous plate 7, or other methods can be used. The choice of liquid supply method can be designed according to specific needs, which is not the focus of this invention, and therefore is not limited.

[0051] In a preferred embodiment, the sintered metal porous plate 7 has an average pore size of 25-50 nm and a porosity of 30%-70%.

[0052] As a preferred embodiment, the angle between the airflow direction 10 at the outlet of the annular air knife 9 and the vertical direction is 0°-30°, and the airflow pressure during operation is 0.1-0.8MPa.

[0053] This invention sets the airflow angle θ of the annular air knife within the range of 0°-30°, which is the core mechanical design for achieving dynamic stabilization of the jet. Within this angular range, the upward axial force of the airflow, F3 = F cosθ, is absolutely dominant. Even at the extreme 30° state (cos30°≈0.866), 86.6% of the airflow energy is still converted into axial force, which fully guarantees the energy requirements to counteract the gravity of the droplets and the axial secondary stretching of the jet. At the same time, the radial component of the annular airflow pointing towards the central axis (F4 = F sinθ) is centrally symmetrical and the vector sum is zero (∑F4=0), which cleverly constructs an invisible "aerodynamic focusing funnel". This funnel forcibly constrains the radial diffusion of the jet, effectively suppresses the inherent bending instability in electrospinning, and ensures that the jet does not deviate from the axis. In addition, this small tilt angle design effectively avoids the backflow turbulence caused by the 0° vertical airflow blowing directly on the bottom surface of the perforated plate. By forming a gentle converging laminar flow below the orifice, it not only achieves the flexible support of the nascent Taylor cone, but also avoids the flow field interference caused by rigid impact.

[0054] As a preferred embodiment, the working negative pressure adjustment range of the suction port 6 is -0.6 to 0 MPa.

[0055] As a preferred embodiment, the liquid supply system 8 has a liquid supply rate adjustable range of 5-30 ml / h.

[0056] As a preferred embodiment, the output voltage adjustment range of the high voltage generator 1 is 0-100kV.

[0057] In a preferred embodiment, the receiving device 5 is a metal collecting plate or a collecting roller, and the vertical receiving distance between the receiving device 5 and the sintered metal porous plate 7 is 10-50cm.

[0058] The present invention also provides a method for confined liquid surface steady-flow electrospinning, which is implemented using the above-mentioned confined liquid surface steady-flow electrospinning device, and includes the following steps:

[0059] S1: Prepare polymer spinning solution;

[0060] S2: The prepared polymer spinning solution is delivered to the sintered metal porous plate 7 through the liquid supply system 8, so that the spinning solution is distributed in the three-dimensional network microporous structure of the sintered metal porous plate 7 under capillary action.

[0061] S3: Turn on the high voltage generator 1 to form a high voltage electrostatic field between the sintered metal porous plate 7 and the receiving device 5.

[0062] S4: Activate the steady flow pneumatic system, generate a reverse airflow from bottom to top through the annular air knife 9, and at the same time form a reverse steady flow air field through the suction port 6 to penetrate the sintered metal porous plate 7.

[0063] S5: Under the synergistic effect of high voltage electrostatic field and reverse steady flow gas field, the spinning solution forms Taylor cones at the micropores on the lower surface of sintered metal porous plate 7 and generates multiple jets. After the jets are stretched and refined and the solvent evaporates and solidifies, they form nanofibers and are finally deposited on receiving device 5.

[0064] The following description, in conjunction with specific embodiments, provides further details.

[0065] Example 1

[0066] This embodiment provides a confined liquid surface steady-flow electrospinning device and its spinning method, with specific parameters and operating status as follows:

[0067] In this embodiment, the average pore size of the sintered metal porous plate 7 is 30 nm, the porosity is 50%, the angle between the airflow direction 10 of the annular air knife 9 and the vertical direction is optimally 15°, the airflow pressure during operation is 0.5 MPa, the working negative pressure adjustment range of the suction port 6 is -0.4 MPa, the liquid supply system 8 has a liquid supply speed adjustment range of 30 ml / h, the output voltage adjustment range of the high voltage generator 1 is 30 kV, the receiving device 5 is a metal collecting plate or collecting roller, and the vertical receiving distance between the receiving device 5 and the sintered metal porous plate 7 is 15 cm.

[0068] In this embodiment, the spinning solution is prepared as follows: a 10% (w / w) polyacrylonitrile (PAN) solution, with N,N-dimethylformamide (DMF) as the solvent. The polymer spinning solution is spun using the confined liquid surface steady-flow electrospinning method of the present invention.

[0069] Results: During 24 hours of continuous operation, thanks to the capillary confinement of the porous plate and the positive pressure support of the 15° countercurrent airflow, a stable and high-density Taylor cone array was formed on the nozzle bottom surface, with no macroscopic droplets falling throughout the entire process. The obtained PAN nanofibers exhibited extremely high uniformity and excellent orientation.

[0070] Conclusion: This embodiment fully verifies the perfect synergistic flow stabilization effect of porous static confinement and aerodynamic focusing headwind.

[0071] Example 2

[0072] This embodiment aims to verify the necessity of the outlet angle of the annular air knife for the jet flow stabilization effect. The specific parameters and operating status are as follows:

[0073] In this embodiment, the device structure and the PAN spinning solution system are the same as in Example 1. All other process parameters are kept completely consistent, except that the included angle of the annular air knife is adjusted to 0° (completely perpendicular) and 45° (out of range) for two independent tests.

[0074] Results: When the included angle is 0°, the airflow directly and perpendicularly impacts the bottom surface of the porous plate. Although no droplets fall, the backflow turbulence causes the micro Taylor cone at the orifice to vibrate.

[0075] When the included angle is 45°, due to the decrease in axial thrust and the excessive aerodynamic centripetal force, the jets at the edge of the perforated plate are excessively compressed to the central region. Macroscopically, this manifests as the jets entangled and forming "filament bundles," resulting in uneven fiber bundle defects on the collecting plate.

[0076] Conclusion: This embodiment demonstrates inversely that 0°-30° (especially the 10°-20° range) is the golden parameter range for balancing axial anti-gravity support and radial anti-disturbance flow stabilization in this invention.

[0077] Example 3

[0078] This embodiment aims to verify the device's limited anti-drip limit capability under harsh industrial expansion conditions.

[0079] In this embodiment, the device structure is the same as in Embodiment 1. Other process parameters are kept completely consistent, but the mass fraction of the PAN solution is reduced to 6%, while the pumping rate of the lateral supply is increased to three times that of Embodiment 1, i.e., 90 ml / h.

[0080] Result: Even with the assistance of a stable flow of gas at the bottom, no macroscopic droplets fell.

[0081] Conclusion: In traditional needleless spinning, the combination of low viscosity and high flux inevitably leads to fluid "pouring". However, in the tests of this invention, no macroscopic droplets fell, and the extremely high permeability damping (capillary confinement) of the three-dimensional intricate pores inside the sintered porous plate played a decisive role.

[0082] Comparative Example 1

[0083] This comparative example uses conventional techniques to reproduce the defects of an open free liquid surface, in order to highlight the inventiveness of this invention.

[0084] In this embodiment, the PAN spinning solution system is the same as in Example 1. All other device structures and process parameters are kept completely consistent, except that the sintered metal porous plate module of this invention is removed and replaced with a traditional open-type slit nozzle (free liquid surface) with macroscopic openings; simultaneously, the annular air knife below is shut off.

[0085] Results: Within minutes of starting the spinning process, due to the lack of physical confinement and pneumatic support, the polymer solution rapidly accumulated at the lower edge of the slit under gravity, forming huge droplets that frequently dripped onto the collection plate, severely contaminating the fiber membrane. Furthermore, the macroscopically open free liquid surface led to uncontrolled solvent evaporation. After a period of operation, a dense polymer crust formed on the nozzle surface, clogging the entire liquid supply channel and forcing a complete interruption of the spinning process.

[0086] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A confined liquid surface stabilizing electrospinning device, characterized in that, include: A confined nozzle, comprising a sintered metal porous plate and a shell covering the sintered metal porous plate, wherein the sintered metal porous plate has an interconnected three-dimensional mesh microporous structure inside, and the shell is a sleeve structure with openings at the top and bottom to expose the micropores on the upper and lower surfaces of the sintered metal porous plate. The liquid supply system is connected to the sintered metal porous plate through a liquid guide pipe and is used to inject spinning solution into the three-dimensional mesh microporous structure inside the sintered metal porous plate. A receiving device, located directly below the sintered metal porous plate, is used to receive nanofibers formed by electrospinning. A high-voltage generator, the positive terminal of which is electrically connected to the sintered metal porous plate, and the negative terminal is grounded or electrically connected to the receiving device; The steady-flow pneumatic system includes an air source and a suction port and an annular air knife connected to it via an air supply pipe. The suction port is located directly above the sintered metal porous plate and connected to the upper part of the outer shell. The annular air knife is located directly below the sintered metal porous plate, and the air outlet of the annular air knife faces the lower surface of the sintered metal porous plate.

2. The confined liquid surface stabilizing electrospinning device according to claim 1, characterized in that, The average pore size of the sintered metal porous plate is 25-50 nm, and the porosity is 30%-70%.

3. The confined liquid surface stabilizing electrospinning device according to claim 1, characterized in that, The angle between the airflow direction at the outlet of the annular air knife and the vertical direction is 0°-30°, and the airflow pressure during operation is 0.1-0.8MPa.

4. The confined liquid surface stabilizing electrospinning device according to claim 1, characterized in that, The working negative pressure adjustment range of the suction port is -0.6 to 0 MPa.

5. The confined liquid surface stabilizing electrospinning device according to claim 1, characterized in that, The liquid supply system has a liquid supply rate adjustable range of 5-30 ml / h.

6. The confined liquid surface stabilizing electrospinning device according to claim 1, characterized in that, The output voltage adjustment range of the high voltage generator is 0-100kV.

7. The confined liquid surface stabilizing electrospinning device according to claim 1, characterized in that, The receiving device is a metal collecting plate or a collecting roller, and the vertical receiving distance between the receiving device and the sintered metal porous plate is 10-50cm.

8. A method for confined liquid surface steady-flow electrospinning, implemented using the confined liquid surface steady-flow electrospinning apparatus according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Prepare polymer spinning solution; S2: The prepared polymer spinning solution is delivered to the sintered metal porous plate through the liquid supply system, so that the spinning solution is distributed in the three-dimensional network microporous structure of the sintered metal porous plate under capillary action. S3: Turn on the high voltage generator to form a high voltage electrostatic field between the sintered metal porous plate and the receiving device; S4: Activate the steady flow pneumatic system, generate a reverse airflow from bottom to top through the annular air knife, and at the same time form a reverse steady flow gas field through the suction port to penetrate the sintered metal porous plate. S5: Under the synergistic effect of high-voltage electrostatic field and reverse steady-flow gas field, the spinning solution forms Taylor cones at the micropores on the lower surface of the sintered metal porous plate and generates multiple jets. After the jets are stretched and refined and the solvent evaporates and solidifies, they form nanofibers and are finally deposited on the receiving device.

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