A needleless electrospinning device with local laser heating

Abstract

The application relates to the technical field of spinning, in particular to a laser local heating needleless electrostatic spinning device, which comprises a high-voltage generator, a laser generator, a solution tank, a fiber generator, a liquid supply device, a driving assembly and a collector, the fiber generator is rotationally connected in the solution tank, the high-voltage generator is connected to the driving assembly, the driving assembly is drivingly connected to the fiber generator, the laser generator is used for emitting a laser beam, the collector corresponds to the fiber generator, and the liquid supply device is communicated with the solution tank. The laser beam of the laser generator is fixedly or scanningly irradiated on a limited area at the edge of the fiber generator, the rotation of the fiber generator is utilized, liquid films successively experience a cold area without heating, a hot area irradiated by the laser beam and a cooling area after leaving the irradiation, so that a time-space temperature gradient of 'cold-hot-cold' is constructed, the control effect on the temperature is improved, and the forming quality of spinning is improved.

Description

Technical Field

[0001] This invention relates to the field of spinning technology, and more particularly to a needleless electrospinning device with laser local heating. Background Technology

[0002] Electrospinning is a common method for preparing nanofiber membranes with high specific surface area, and it has been widely used in biomedicine, filtration and separation, self-cleaning and other fields. Traditional electrospinning often uses a single-needle or multi-needle nozzle structure, in which the polymer solution at the nozzle tip is stretched into a jet and deposited into a film under the action of a high voltage electric field.

[0003] While needle-based electrospinning readily yields nanoscale fibers, a single needle only forms a single jet, resulting in low production volume and difficulty in scaling up. Parallel multi-needle configurations can lead to mutual electric field interference, causing jet deflection, mutual attraction, and other unstable phenomena, making it difficult to achieve stable, large-area uniform deposition. Furthermore, high-concentration solution nozzles are prone to clogging and require complex maintenance, necessitating frequent cleaning or replacement, resulting in poor continuous production capabilities.

[0004] To address the issues of nozzle clogging and low output, needleless electrospinning technology has emerged, using free liquid surfaces such as rotating disks and rotating cylinders as fiber generators. Taking a rotating disk as an example, the solution forms a thin liquid film at the edge of the disk, which can simultaneously generate multiple jets under the action of an electric field, thereby significantly increasing the output per unit time and improving continuity.

[0005] However, existing needleless electrospinning methods generally suffer from problems such as high critical starting voltage, high energy consumption, and narrow process window. A relatively high voltage is often required on the free liquid surface to form stable multi-jet sprays; even a slight decrease in voltage can lead to difficulty in starting the spin or a significant drop in yield. To reduce solution viscosity and improve starting, current technologies often use electric heating plates, hot air, or infrared lamps to heat the entire solution or metal components as a whole. However, this overall heating makes it difficult to achieve precise temperature control in the critical region where the jet initially forms, both spatially and temporally, and may also disrupt the system's stability.

[0006] From a process mechanism perspective, the thin liquid film at the edge of the rotating disk needs to form a controllable "cold zone-hot zone-cold zone" cyclical temperature process along the rotation trajectory. This involves maintaining overall solution stability before entering the hot zone; instantaneously reducing viscosity and promoting jet generation and stretching in the hot zone; and rapidly cooling after leaving the hot zone to facilitate fiber solidification and shaping. Existing overall heating methods struggle to spatially distinguish these zones and also fail to achieve precise synchronous control of rapid heating and cooling processes over time.

[0007] Existing heating methods for needle-free electrospinning have at least the following key drawbacks in practical applications:

[0008] (1) Uncontrollable local temperature gradient: It is difficult to establish a stable and repeatable local temperature gradient in the initial region of the jet when the whole heating is used, which can easily lead to uneven distribution of liquid film viscosity and surface tension; in water-based systems, it may cause the overall viscosity to be too low and induce spray or droplets; in high-boiling-point organic solvent systems, it may cause local over-concentration or even the formation of a "skin", resulting in coarser fibers and deterioration of morphology.

[0009] (2) Slow thermal response and long parameter adjustment cycle: The overall heating has a large thermal inertia. When it is necessary to adjust the temperature to adapt to different materials or process parameters, it is often necessary to wait for the temperature of the entire solution tank or the environment to stabilize, making it difficult to achieve rapid process switching.

[0010] (3) Low energy utilization: The only area that actually needs temperature adjustment is the thin liquid film at the edge of the fiber generator, while overall heating requires heating the entire solution or environment. A large amount of heat is consumed in the non-spinning area, resulting in high energy consumption costs.

[0011] (4) It is detrimental to solution stability and material compatibility: Some polymer solutions are sensitive to temperature. Overall heating can easily cause thermal degradation or abnormal viscosity fluctuations, which can damage the spinnability of the solution and limit the material system and long-term continuous operation.

[0012] Laser heating features non-contact operation, rapid response, and strong spatial selectivity, enabling rapid heating of limited areas and coupling with the motion of rotating devices to form periodic local thermal processes. Therefore, there is an urgent need for a rapid and controllable local temperature control method for the initial generation region of needle-free electrospinning jets, to reduce the critical starting voltage, broaden the process window, and improve yield and fiber uniformity without significantly altering the overall solution state.

[0013] On the other hand, most of the existing publicly available laser-assisted electrospinning methods focus on needle-shaped nozzle structures and often require the doping of photothermal materials or rely on specific solution systems. Systematic research on the laser effect and process window in needleless electrospinning is still relatively insufficient, and there is a lack of parameter control methods that can be extended to different polymer / solvent systems. Summary of the Invention

[0014] This invention aims to at least solve one of the technical problems existing in related technologies. To this end, this invention provides a needleless electrospinning device with laser local heating, which solves the technical problems of high difficulty and low precision in controlling spinning temperature in the prior art. By fixing or scanning the laser beam of the laser generator onto a limited area at the edge of the fiber generator, and utilizing the rotation of the fiber generator, the liquid film sequentially experiences an unheated cold zone, a hot zone irradiated by the laser beam, and a recooling zone after leaving the irradiation zone. This naturally constructs a "cold-hot-cold" spatiotemporal temperature gradient at the edge of the fiber generator, improving the temperature control effect and the spinning quality.

[0015] This invention provides a needleless electrospinning device with localized laser heating, comprising a high-voltage generator, a laser generator, a solution tank, a fiber generator, a liquid supply device, a drive assembly, and a collector. The fiber generator is rotatably connected to the solution tank, the drive assembly is driven and connected to the fiber generator, the high-voltage generator is connected to the solution tank, the laser generator is used to emit a laser beam that can irradiate the fiber generator, the collector corresponds to the fiber generator, and the liquid supply device is connected to the solution tank.

[0016] The spinning process includes the following steps:

[0017] Prepare a polymer solution and add it to a solution tank and a liquid supply device; immerse the fiber generator in the polymer solution.

[0018] Adjust the collection distance between the top of the collector and the top of the fiber generator and set the rotation speed of the fiber generator;

[0019] The laser generator is turned on, and the laser beam emitted by the laser generator irradiates the fiber generator. The drive component is turned on, and the drive component drives the fiber generator to rotate, so as to bring the polymer solution to the edge of the fiber generator to form a liquid film. Under the combined action of the laser beam and the high voltage electric field generated by the high voltage generator, the liquid film generates multiple polymer jets. The polymer jets are collected on the surface of the collector to form a nanofiber membrane.

[0020] The polymer solution is replenished to the solution tank in real time by a liquid supply device.

[0021] A further improvement of the laser-heated needleless electrospinning device of the present invention is that the polymer solution is a water-soluble polymer solution and / or an organic solvent-based polymer solution.

[0022] A further improvement of the laser-heated needleless electrospinning device of the present invention is that the water-soluble polymer solution is a polyvinyl alcohol aqueous solution with a mass fraction of 1-30%.

[0023] A further improvement of the laser-heated needleless electrospinning device of the present invention is that the solvent of the organic solvent-based polymer solution is N,N-dimethylformamide, the solute of the organic solvent-based polymer solution is polyacrylonitrile, and the mass fraction of the organic solvent-based polymer solution is 8~12%.

[0024] A further improvement of the laser-heated needleless electrospinning device of the present invention is that the fiber generator is made of a conductive and thermally conductive metal material, the fiber generator has a spoke-type structure, the diameter of the fiber generator is 30~80mm, and the thickness of the fiber generator is 1~3mm.

[0025] A further improvement of the laser-heated needleless electrospinning device of the present invention is that the high voltage generator outputs a voltage of 40~75kV.

[0026] A further improvement of the laser-heated needleless electrospinning device of the present invention is that the solution tank is a polytetrafluoroethylene tank.

[0027] A further improvement of the laser-heated needleless electrospinning device of the present invention is that the spinning process is carried out under environmental conditions of temperature 21~90℃ and relative humidity 1~50%.

[0028] A further improvement of the needleless electrospinning device with localized laser heating of the present invention is that the laser generator is a fiber laser or a CO2 laser, the laser beam emitted by the laser generator has a wavelength of 1064nm or 10.6μm, the output power of the laser generator is 1~70W, and the laser beam emitted by the laser generator is focused on the fiber generator with a spot diameter of 1~3mm.

[0029] A further improvement of the laser-heated needleless electrospinning device of the present invention is that the collector is a flat plate or a roller, and the collection distance is 10~20cm.

[0030] This invention focuses a laser onto a segment of an arc at the edge of the fiber generator, causing the liquid film of the needleless spinning device to sequentially experience a cold-hot-cold time / space gradient during rotation: an unirradiated cold zone, a laser-irradiated hot zone, and a cooled zone after laser removal. This localized heating does not significantly increase the overall solution temperature, but it can significantly reduce the liquid film viscosity and increase the charge density in the spinning zone, thereby lowering the critical spinning voltage, increasing the number of jets, and improving fiber stretching.

[0031] The needleless electrospinning method of the present invention is applicable to a variety of polymers, including water-soluble polymers such as PVA, organic solvent systems such as PAN, and blended solution systems. For systems with different solvent evaporation rates and viscosity-temperature characteristics, the corresponding optimal window can be obtained by adjusting parameters such as laser power, device structure, laser irradiation point position, collection distance, and voltage.

[0032] The laser local heating method of the present invention does not require additional nozzle structure, making it easy to scale up to wide width, multi-fiber generator or multi-row arrangement; by rationally designing laser scanning or multi-spot array, the output per unit time can be further improved, realizing continuous industrial production.

[0033] The fiber generator is a device with good electrical and thermal conductivity. Under the action of a high-voltage electric field, it forms multiple jets to achieve needle-free electrospinning. The geometry of the fiber generator is not limited to a disc, but includes, but is not limited to, the following configurations: disc type or flat wheel type (single or multiple discs arranged coaxially); linear, rod-shaped or string-shaped fiber generating components, such as tensioning metal wires, wire frames, etc.; cylindrical roller type fiber generating components, such as solid or hollow conductive rollers; gear type, comb type, sawtooth edge type, etc. with protrusions on the edges.

[0034] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of a needleless electrospinning device with laser local heating provided by the present invention.

[0037] Figure 2 This is a test illustration of a laser-heated needleless electrospinning device provided by the present invention performing a spinning method. Figure 1 .

[0038] Figure 3 This is a test illustration of a laser-heated needleless electrospinning device provided by the present invention performing a spinning method. Figure 2 .

[0039] Figure 4 This is a test illustration of a laser-heated needleless electrospinning device provided by the present invention performing a spinning method. Figure 3 .

[0040] Figure 5 This is a test illustration of a laser-heated needleless electrospinning device provided by the present invention performing a spinning method. Figure 4 .

[0041] Figure 6 This is a test illustration of a laser-heated needleless electrospinning device provided by the present invention performing a spinning method. Figure 5 .

[0042] Figure 7 This is a schematic diagram showing the temperature changes of a fiber generator using different laser powers during the spinning process.

[0043] Figure 8 This is a comparison chart of PVA fiber diameters with and without laser treatment.

[0044] Figure 9 These are thermal images of spinning without and with laser.

[0045] Figure 10 These are scanning electron microscope (SEM) images of nanofiber membranes with and without laser.

[0046] Figure 11 This is a histogram of fiber diameter distribution with and without laser.

[0047] Figure label:

[0048] 1. High-pressure generator; 2. Solution tank; 3. Fiber generator; 4. Collector; 5. Laser beam; 6. Liquid supply device. Detailed Implementation

[0049] 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. The following embodiments are used to illustrate this invention but should not be used to limit the scope of this invention.

[0050] The following is combined with Figure 1 The present invention describes a needleless electrospinning device with laser local heating, comprising a high-voltage generator 1, a laser generator, a solution tank 2, a fiber generator 3, a liquid supply device 6, a drive assembly, and a collector 4. The fiber generator 3 is rotatably connected to the solution tank 2, the drive assembly is driven to the fiber generator 3, the high-voltage generator 1 is connected to the solution tank 2, the laser generator is used to emit a laser beam 5, the laser beam 5 can irradiate the fiber generator 3, the collector 4 corresponds to the fiber generator 3, and the liquid supply device 6 is connected to the solution tank 2.

[0051] The spinning process includes the following steps:

[0052] A polymer solution is prepared and added to solution tank 2 and liquid supply device 6, and fiber generator 3 is immersed in the polymer solution;

[0053] Adjust the collection distance between the top of the collector 4 and the fiber generator 3 and set the rotation speed of the fiber generator 3;

[0054] The laser generator is turned on, and the laser generator emits a laser beam 5 to irradiate the fiber generator 3. The drive assembly is turned on, and the drive assembly drives the fiber generator 3 to rotate, so as to bring the polymer solution to the edge of the fiber generator 3 to form a liquid film. Under the combined action of the laser beam 5 and the high voltage electric field generated by the high voltage generator 1, the liquid film generates multiple polymer jets. The polymer jets are collected on the surface of the collector 4 to form a nanofiber membrane.

[0055] The polymer solution is replenished to the solution tank 2 in real time by the liquid supply device 6.

[0056] Preferably, during the spinning process, the parameters of the laser generator can be adjusted according to the specific characteristics of the desired nanofiber membrane. Changing the power of the laser beam 5 affects the temperature and fluidity of the liquid film, thereby influencing the formation of the polymer jet and the diameter of the nanofibers. When finer nanofibers are required, the laser power can be appropriately increased to enhance the fluidity of the liquid film, making it easier to form fine jets under the action of a high-voltage electric field. By controlling the intensity of the high-voltage electric field generated by the high-voltage generator 1, the stretching degree and flight trajectory of the polymer jet can be adjusted. A higher electric field intensity can subject the jet to greater stretching force, resulting in finer and more uniformly distributed nanofibers. The spinning effect can be adjusted by regulating the rotation speed of the fiber generator 3. The faster the rotation speed of the fiber generator 3, the more polymer solution is brought to the edge of the fiber generator 3 per unit time, and the thickness of the formed liquid film will increase accordingly. During the spinning process, the properties of the polymer solution and the drying process of the jet can be adjusted by regulating the ambient temperature and humidity. Lower humidity is conducive to the rapid drying of the jet, thereby improving the forming quality of the nanofiber membrane.

[0057] Further, the polymer solution is a water-soluble polymer solution and / or an organic solvent-based polymer solution. In one embodiment, the polymer solution may be a water-soluble polymer solution; in another embodiment, the polymer solution may be an organic solvent-based polymer solution; in yet another embodiment, the polymer solution may be a blended solution system formed by mixing a water-soluble polymer solution and an organic solvent-based polymer solution.

[0058] The water-soluble polymer solution is an aqueous solution of polyvinyl alcohol (PVA), with a mass fraction of 1-30%. The solute is PVA, with a degree of alcoholysis of 87-99 mol% and a number-average molecular weight of 8 × 10⁻⁶. 4 ~15×10 4 During the preparation process, PVA is weighed at a mass fraction of 1-30% and added to deionized water. The mixture is heated in a water bath at 60-90℃ and magnetically stirred for 2-6 hours until it is completely dissolved to obtain a transparent and homogeneous solution. The solution is then cooled to room temperature and allowed to stand to remove bubbles, forming a water-soluble polymer solution.

[0059] Preferably, the mass fraction of the polyvinyl alcohol aqueous solution can be selected as 1%, 5%, 10%, 15%, 20%, 25%, or 30%.

[0060] The solvent for the organic solvent-based polymer solution is N,N-dimethylformamide (DMF), and the solute is polyacrylonitrile (PAN). The mass fraction of the organic solvent-based polymer solution is 8-12%. During preparation, PAN is weighed at 8-12% by mass and added to DMF. The solution is magnetically stirred at 50-80°C for 4-6 hours until it is completely dissolved to obtain a transparent and homogeneous solution. The solution is then cooled to room temperature and allowed to stand to remove bubbles, thus forming the organic solvent-based polymer solution.

[0061] Preferably, the mass fraction of the organic solvent-based polymer solution can be selected as 8%, 9%, 10%, 11%, or 12%.

[0062] The solute of the organic solvent-based polymer solution is one or more of flexible polymers, elastic polymers, and rigid polymers; the flexible polymer may be selected from polyaniline, polyvinylpyrrolidone, polyvinyl alcohol, polyvinylidene fluoride, and polyacrylonitrile; the solvent of the organic solvent-based polymer solution may be selected from dimethylacetamide, dimethylformamide, N-methylpyrrolidone, acetone, ethanol, or water.

[0063] Specifically, the fiber generator 3 is made of a conductive and thermally conductive metal material, the fiber generator 3 has a spoke-type structure, the diameter of the fiber generator 3 is 30~80mm, and the thickness of the fiber generator 3 is 1~3mm.

[0064] Preferably, the diameter of the fiber generator 3 can be selected as 30mm, 40mm, 50mm, 60mm, 70mm, or 80mm. The thickness of the fiber generator 3 can be selected as 1mm, 1.5mm, 2mm, 2.5mm, or 3mm.

[0065] Preferably, the conductive and thermally conductive metal material can be selected from copper, stainless steel, aluminum, or iron.

[0066] Preferably, the drive component is a speed-regulating motor, and the fiber generator 3 is connected to the speed-regulating motor via an insulated shaft.

[0067] Specifically, the high-voltage generator 1 outputs a voltage of 40~75kV. A metal electrode is inserted into the solution tank 2 and connected to the high-voltage output terminal of the high-voltage generator 1 to apply a high voltage of 40~75kV to the polymer solution.

[0068] Specifically, the solution tank 2 is a polytetrafluoroethylene (PTFE) tank. PTFE tanks have good chemical stability and corrosion resistance, effectively preventing chemical reactions with the polymer solution and ensuring the stability of the solution's properties.

[0069] Specifically, the spinning process is carried out under environmental conditions of 21~90℃ and 1~50% relative humidity.

[0070] Preferably, the temperature of the spinning process can be selected as 21℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, or 90℃; the relative humidity of the spinning process can be selected as 1%, 10%, 20%, 30%, 40%, or 50%.

[0071] Specifically, the laser generator is a fiber laser or a CO2 laser. The laser beam 5 emitted by the laser generator has a wavelength of 1064 nm or 10.6 μm, and the output power of the laser generator is 1~70 W. The laser beam 5 emitted by the laser generator is focused onto the fiber generator 3, and the spot diameter is 1~3 mm. The spot position is located at the upper end of the fiber generator 3 when it is placed vertically, where the electric field intensity is the highest, or at the lower end of the fiber generator 3 when it is placed vertically, i.e., a relatively lower circumferential position.

[0072] Specifically, the collector 4 is a flat plate or a roller, and the collection distance is 10~20cm.

[0073] Figure 2 Figure (a) shows the effect of laser application on the diameter of PVA nanofiber films under different applied voltages. It can be seen that without laser, the fiber diameter decreases monotonically with increasing voltage from 40 kV to 75 kV, with a diameter of approximately 1 μm at 40 kV and decreasing to approximately 280 nm at 75 kV. With the introduction of a 17 W laser, the fiber diameter further decreases across the entire voltage range, decreasing from 990 nm to approximately 740 nm at 40 kV and from approximately 280 nm to approximately 230 nm at 75 kV, indicating that localized laser heating can achieve a more thorough stretching and refining effect at the same voltage.

[0074] Figure 2 (b) shows the effect of laser addition on fiber yield at different voltages. Without laser, 40kV is close to the critical spinning voltage, and the yield per unit time is only about 0.012g / h; as the voltage increases to 75kV, the yield slowly increases to about 1.44g / 10min. Under the same conditions, adding laser significantly increases the yield at all voltages. At 40kV, a considerable yield of about 0.27g / h can still be obtained, indicating that the laser increases the effective jet number by an order of magnitude near the critical voltage; at 75kV, the yield increases to about 2.922g / h, with an increase of about 70%~100%, indicating that local laser heating can both lower the spinning threshold and significantly increase the yield per unit time within the working voltage range.

[0075] Figure 3 (a) shows the effect of different laser powers on the diameter of PVA nanofiber membranes; Figure 3Figure (b) shows the effect of different laser powers on the yield of PVA nanofibers (critical voltage 40 kV, fiber generator 3 rotation speed 30 r / min, spinning distance 20 cm).

[0076] Figure 3 Figure (a) shows the effect of different laser powers on the diameter of PVA fibers at a critical voltage of 40 kV. As the laser power increases from 0 to 17 W, the fiber diameter decreases significantly, showing a trend of first decreasing and then increasing: at low power (2.3–5.7 W), the diameter decreases slightly; when the power is in the range of 11.3–17 W, the fiber diameter drops to the lowest value in this experiment; when the power is further increased to 22.6–28.3 W, the fiber diameter increases again. This indicates that there is an optimal laser power window at the critical voltage; too low a power cannot significantly change the liquid film viscosity, while too high a power leads to overheating, which is detrimental to fiber refinement. Figure 3 Figure (b) shows the effect of different laser powers on the yield of PVA nanofibers under 40kV conditions. As the laser power increases from 0 to 17-22.6W, the yield per unit time increases rapidly, reaching a maximum around 17W, at which point stable multi-jetting is achieved without severe droplet jetting. When the power continues to increase to 28.3W, the yield decreases slightly. (Summary) Figure 3 (a) and Figure 3 (b) It can be considered that about 17W is the optimal laser power that balances fiber refinement and yield improvement under the critical voltage.

[0077] Figure 4 (a) shows the effect of polymer concentration and laser power on the diameter of PVA nanofiber membranes; Figure 4 Figure (b) shows the effect of polymer concentration and laser power on the yield of PVA nanofiber membranes; test conditions: voltage 75 kV, fiber generator speed 30 r / min, spinning distance 20 cm.

[0078] Figure 4 Figures (a) and (b) show that under the conditions of 75 kV and 30 r / min, the fiber diameter is mainly controlled by the PVA concentration, while the laser power further regulates the fiber stretching and curing process; overall, the higher the PVA concentration, the larger the fiber diameter.

[0079] Figure 4Algebra (a) shows that the fiber diameter prepared from 14 wt% PVA is significantly higher than that from 6 wt% and 10 wt%. The fiber diameters from 6 wt% and 10 wt% are generally smaller, mainly concentrated around 200-350 nm. This phenomenon is caused by the increased viscosity and molecular chain entanglement of the system as the solution concentration increases, making it more difficult for the jet to be thinned under the action of electric field and rotational stretching, thus forming thicker fibers. Regarding the effect of laser power, all three concentrations show a certain trend of first decreasing and then increasing, or a trough and then rising. For the 6 wt% and 10 wt% samples, the fiber diameter decreases slightly as the laser power increases from low to medium power, indicating that appropriate laser heating may reduce solution viscosity, promote solvent evaporation, and enhance jet stretching, making the fibers thinner. However, when the power continues to increase, the fiber diameter gradually increases again, especially in the higher power range. This may be due to excessively rapid solvent evaporation, premature jet solidification leading to insufficient subsequent stretching, or increased thermal disturbance causing decreased jet stability. The changes were more pronounced in the 14wt% sample: at low to medium laser power, the fiber diameter decreased from a high value to a minimum, and then increased significantly with increasing power. This indicates that the high-concentration PVA system is more sensitive to laser power. Since the 14wt% solution itself has a high viscosity, moderate heating is beneficial to reduce viscosity and improve drawing. However, excessive power will cause the high-viscosity jet to solidify rapidly, limiting further thinning. Therefore, the fiber diameter increases rapidly instead.

[0080] Figure 4 Figure (b) shows the effect of different concentrations and laser power on yield. At 6 wt% and high laser power, the increase in mass is due to droplet jetting; at 14 wt%, the high viscosity makes multi-jet formation difficult, resulting in lower yield. A concentration of 10 wt% at 17-22.6 W maintains both high yield and the finest fibers, exhibiting the best overall performance. Therefore, for PVA aqueous solutions, the preferred concentration in this invention is approximately 10 wt%, used in conjunction with a medium-power laser.

[0081] Figure 5 (a), (b), and (c) show the effects of different rotation speeds of the fiber generator and laser parameters on the diameter of the PVA nanofiber membrane at different laser irradiation points (8 r / min, 30 r / min, 50 r / min); Figure 5 (d), (e), and (f) show the effects of different rotation speeds and laser parameters of the fiber generator on the yield of PVA nanofiber membranes at different laser irradiation points (8 r / min, 30 r / min, 50 r / min); test conditions: voltage 75 kV, spinning distance 20 cm.

[0082] Figure 5Figures (a), (b), and (c) show the changes in fiber diameter with laser power when the laser irradiates the upper and lower edges of the fiber generator at three rotational speeds of 8 r / min, 30 r / min, and 50 r / min, respectively. It can be seen that at all three rotational speeds, the fiber diameter exhibits a minimum value near the medium power, but the power and irradiation position corresponding to the minimum value differ slightly. At most laser powers, the fiber diameter obtained by irradiation at the upper edge is slightly smaller than that obtained by irradiation at the lower edge, indicating that placing the laser in the region with the strongest electric field and where the liquid film has just overflowed is more conducive to refining. As the fiber generator rotational speed increases from 8 r / min to 30 r / min, the overall fiber diameter decreases slightly. Further increasing to 50 r / min results in excessively rapid liquid film renewal and insufficient local heating time, leading to a decrease in the refining effect.

[0083] Figure 5 Figures (d), (e), and (f) show the changes in fiber yield under the same conditions. The results indicate that for the same rotational speed, the yield at the upper edge irradiation is generally higher than that at the lower edge irradiation, especially at medium power levels (e.g., 17–22.6 W). As the fiber generator rotational speed increases from 8 r / min to 30 r / min, the yield increases significantly, indicating that appropriately increasing the rotational speed is beneficial for increasing the effective jet number. When the rotational speed further increases to 50 r / min, the yield shows a decreasing trend, indicating that excessively high rotational speeds lead to an excessively thin liquid film and unstable jetting. In summary... Figure 5 It is evident that the present invention, under moderate laser power, upper edge irradiation, and moderate rotation speed (approximately 30 r / min), can achieve a better compromise between fiber diameter and yield.

[0084] Figure 6 (a) shows the effect of laser power on the diameter of PVA nanofiber membrane at different rotation speeds of the fiber generator (high-point irradiation). Figure 6 (b) shows the effect of laser power on the yield of PVA nanofiber membranes at different rotation speeds of the fiber generator (high-point irradiation). Figure 6 (c) shows the effect of laser power on the diameter of PVA nanofiber membrane at different rotation speeds of the fiber generator (low-point irradiation). Figure 6 The middle (d) shows the effect of different rotation speeds of the fiber generator and laser power on the yield of PVA nanofiber membranes (low-point irradiation). Test conditions: voltage 75kV, spinning distance 20cm.

[0085] Figure 6Figures (a) and (c) show that, under conditions of 75 kV voltage and 20 cm spinning distance, the fiber diameter of PVA nanofiber membranes at different spinning speeds generally shows a trend of first slightly decreasing and then increasing with laser power, with relatively smaller fiber diameters at medium laser power. Specifically, in the low to medium power range, laser heating reduces solution viscosity and promotes jet stretching, thus reducing fiber diameter. However, as laser power increases further, solvent evaporation accelerates, and the jet may solidify prematurely, leading to insufficient subsequent stretching and an increase in fiber diameter. The difference in fiber diameter at the three spinning speeds does not exhibit a consistent pattern of "maximum at 50 r / min and minimum at 30 r / min," but rather alternates between different power points. The fiber diameters obtained at 30 r / min and 50 r / min are mostly similar. At 8 r / min, especially near 67.8 W, the fiber diameter increases significantly, indicating that the combination of excessively high power and low spinning speed is not conducive to further fiber refinement.

[0086] Figure 6 Figures (b) and (d) show that fiber yield responds more significantly to laser power than fiber diameter. Under upper edge (high-point irradiation) and lower edge (low-point irradiation) conditions, yield at all three rotation speeds initially increases and then decreases with increasing laser power, reaching a relatively high value around 17W. At low power, insufficient laser heating results in high solution viscosity and a limited number of stable jets, leading to low yield. As power increases, solution fluidity improves, solvent evaporation and fiber curing processes are promoted, the jet becomes more stable, and yield increases significantly. However, when the power continues to increase above 28.3W, excessive heat may cause jet instability, excessively rapid solvent evaporation, or fiber breakage and scattering, thus reducing yield. Regarding the effect of rotation speed, yield does not always follow the pattern of "highest at 30 r / min, followed by 8 r / min, and lowest at 50 r / min." Figure 6 In (b), the output at 8 r / min and 30 r / min was significantly higher than that at 50 r / min, with 30 r / min reaching its highest value near 17 W, while 8 r / min maintained a high output in the lower to medium power range. Figure 6 In the middle (d) range, 8 r / min yielded the highest output around 11.3~17 W, followed by 30 r / min, while 50 r / min generally yielded the lowest. This indicates that lower or moderate rotational speeds are more conducive to forming stable jets, while excessively high rotational speeds may lead to excessively rapid liquid film renewal, insufficient heating time, or increased liquid surface disturbance, thereby reducing the number of effective jets and fiber output.

[0087] In conclusion, Figures 2 to 6The results systematically demonstrate that by adjusting the applied voltage, laser power, polymer concentration, fiber generator rotation speed, and laser irradiation position, a "low voltage, multi-jet, controllable refinement" process window can be established in needleless electrospinning of the fiber generator, thereby realizing the performance advantages of laser-assisted needleless electrospinning of the fiber generator in this invention.

[0088] Figure 7 This is a thermal imaging distribution diagram of the temperature change of the fiber generator during the spinning process of this invention under different laser powers (0W, 2.3W, 5.7W, 11.3W, 17W, 22.6W, 28.3W, 33.9W, 45.2W, 67.8W). Each sub-graph corresponds to the working condition of increasing laser power gradient. The center temperature, highest temperature and lowest temperature of the fiber generator under the corresponding working condition are marked in the sub-graph. The color scale on the left indicates the gradual temperature range from 30.0℃ to 100.0℃, which intuitively reflects the control effect of laser power on the temperature field distribution of the fiber generator. This invention introduces a laser power adjustment mechanism during the spinning process, achieving precise and controllable regulation of the temperature field of the fiber generator. Compared with traditional spinning temperature control methods, it has the following significant technical advantages: By linearly adjusting the laser power, the temperature of the fiber generator can be linearly controlled, enabling gradient and fine-tuning of the temperature during spinning. This meets the differentiated temperature requirements of various polymer materials and composite materials for spinning formation, effectively avoiding the problems of large temperature fluctuations and lag response in traditional temperature control methods. As the laser power increases, the range and intensity of the high-temperature region of the fiber generator are significantly enhanced, and the concentration and directionality of the temperature distribution are improved. This is beneficial to the stability and consistency of fiber formation during spinning, reducing fiber structural defects caused by uneven temperature distribution, and improving the yield and quality of the spun fiber.

[0089] Figure 8 The image shows a comparison of PVA fiber diameters with and without laser treatment. Figure 8 The results showed that under the same experimental conditions (75KV voltage, 20cm spinning distance), the average diameter of PVA nanofibers decreased significantly after the introduction of laser heating, and the diameter distribution became more concentrated and uniform. This directly demonstrated the controllable refining / homogenization effect. Local laser heating made the liquid film easier to stretch and refine in the spinning zone and improved the uniformity of fiber distribution.

[0090] Figure 9 Figure (a) is a thermal image of spinning without laser 0W (21.4℃). Figure 9 Figure (b) is a thermal image of spinning with a 17W laser (44.5℃). Figure 9The results show that without laser spinning, the center temperature of the thermal imaging image is only 21.4℃. After introducing the laser, the thermal imaging shows obvious "hot spots / localized heating zones," the locations of which correspond to the laser's point of action. This indicates that the laser establishes spatially selective localized hot zones at the edge of the fiber generator, which, when coupled with the rotation of the disk, can form a periodic localized thermal process. By fixing or scanning the laser beam onto a limited area at the edge, and coordinating with the disk rotation, the liquid film experiences a cold-hot-cold spatiotemporal temperature gradient of "cold zone-hot zone-cooling zone," thereby improving temperature control accuracy and fiber quality.

[0091] Figure 10 Figure (a) shows a scanning electron microscope (SEM) image of the nanofiber membrane without laser 0W. Figure 10 Figure (b) shows a scanning electron microscope (SEM) image of the nanofiber membrane under 17W laser illumination. The microstructure reveals that under traditional needle-free spinning, the resulting fibers are relatively coarse, with numerous agglomerated structures and poor fiber uniformity (corresponding to the subsequent fiber diameter distribution diagram). After introducing the laser, the localized hot zones significantly reduced the liquid film viscosity and increased the jet stretching, resulting in significantly finer and more refined nanofibers with superior morphology. Figure 10 The nanofibers obtained in Figure (b) are significantly finer and have better morphology, which proves that traditional needleless spinning relying solely on electric fields and rotation has an upper limit in improving fiber fineness and uniformity, and additional local temperature control methods are indeed needed to overcome the bottleneck.

[0092] Figure 11 Figure (a) shows the histogram of fiber diameter distribution without laser 0W. Figure 11 Figure (b) is a histogram of fiber diameter distribution under 17W laser illumination. Figure 11 The histogram showing the fiber diameter distribution without laser treatment indicates a relatively wide distribution with an average diameter of 281±78 nm. After laser treatment, the average diameter further decreases and the distribution becomes more concentrated (standard deviation decreases), with the average diameter dropping to 225±40 nm. With localized laser heating, within the same voltage range, the fiber diameter can be further reduced, effectively achieving a significant stretching and refining effect on the fiber diameter.

[0093] This invention proposes a novel method for introducing localized laser heating in needleless electrospinning. By focusing a laser on an arc at the edge of the fiber generator, the liquid film of the needleless spinning device sequentially experiences a cold-hot-cold time / space gradient during rotation, consisting of an un-illuminated cold zone, a laser-illuminated hot zone, and a cooled zone after laser irradiation. This localized heating does not significantly increase the overall solution temperature, but it significantly reduces the liquid film viscosity and increases the charge density in the spinning zone, thereby lowering the critical spinning voltage, increasing the number of jets, and improving fiber stretching.

[0094] The needleless electrospinning method of the present invention is applicable to a variety of polymers, including water-soluble polymers such as PVA, organic solvent systems such as PAN, and blended solution systems. For systems with different solvent evaporation rates and viscosity-temperature characteristics, the corresponding optimal window can be obtained by adjusting parameters such as laser power, device structure, laser irradiation point position, collection distance, and voltage.

[0095] The laser local heating method of the present invention does not require additional nozzle structure, making it easy to scale up to wide width, multi-fiber generator or multi-row arrangement; by rationally designing laser scanning or multi-spot array, the output per unit time can be further improved, realizing continuous industrial production.

[0096] The fiber generator is a device with good electrical and thermal conductivity. Under the action of a high-voltage electric field, it forms multiple jets to achieve needle-free electrospinning. The geometry of the fiber generator is not limited to a disc, but includes, but is not limited to, the following configurations: disc type or flat wheel type (single or multiple discs arranged coaxially); linear, rod-shaped or string-shaped fiber generating components, such as tensioning metal wires, wire frames, etc.; cylindrical roller type fiber generating components, such as solid or hollow conductive rollers; gear type, comb type, sawtooth edge type and other configurations with raised edges.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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; and these 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 needleless electrospinning device with laser local heating, characterized in that, The device includes a high-voltage generator, a laser generator, a solution tank, a fiber generator, a liquid supply device, a drive assembly, and a collector. The fiber generator is rotatably connected to the solution tank, the drive assembly is driven to the fiber generator, the high-voltage generator is connected to the solution tank, the laser generator emits a laser beam that can irradiate the edge of the fiber generator, the collector corresponds to the fiber generator, and the liquid supply device is connected to the solution tank. The spinning process includes the following steps: Prepare a polymer solution and add it to a solution tank and a liquid supply device; immerse the fiber generator in the polymer solution. Adjust the collection distance between the top of the collector and the top of the fiber generator and set the rotation speed of the fiber generator; The laser generator is turned on, and the laser generator emits a laser beam that irradiates the edge of the fiber generator. The drive assembly is turned on, and the drive assembly drives the fiber generator to rotate, so as to bring the polymer solution to the edge of the fiber generator to form a liquid film. Under the combined action of the laser beam and the high voltage electric field generated by the high voltage generator, the liquid film generates multiple polymer jets. The polymer jets are collected on the surface of the collector to form a nanofiber membrane. The polymer solution is replenished to the solution tank in real time by a liquid supply device.

2. The needleless electrospinning device with laser local heating according to claim 1, characterized in that, The polymer solution is a water-soluble polymer solution and / or an organic solvent-based polymer solution.

3. The needleless electrospinning device with laser local heating according to claim 2, characterized in that, The water-soluble polymer solution is an aqueous solution of polyvinyl alcohol, with a mass fraction of 1-30%.

4. The needleless electrospinning device with laser local heating according to claim 2, characterized in that, The solvent of the organic solvent-based polymer solution is N,N-dimethylformamide, the solute of the organic solvent-based polymer solution is polyacrylonitrile, and the mass fraction of the organic solvent-based polymer solution is 8~12%.

5. The laser-heated needleless electrospinning device according to claim 1, characterized in that, The fiber generator is made of a conductive and thermally conductive metal material. The fiber generator has a spoke-type structure, a diameter of 30-80 mm, and a thickness of 1-3 mm.

6. The laser-heated needleless electrospinning device according to claim 1, characterized in that, The high-voltage generator outputs a voltage of 40~75kV.

7. The needleless electrospinning device with laser local heating according to claim 1, characterized in that, The solution tank is a polytetrafluoroethylene tank.

8. The laser-heated needleless electrospinning device according to claim 1, characterized in that, The spinning process is carried out under environmental conditions of 21~90℃ and 1~50% relative humidity.

9. The needleless electrospinning device with laser local heating according to claim 1, characterized in that, The laser generator is a fiber laser or a CO2 laser. The laser beam emitted by the laser generator has a wavelength of 1064nm or 10.6μm. The output power of the laser generator is 1~70W. The laser beam emitted by the laser generator is focused on the fiber laser generator with a spot diameter of 1~3mm.

10. The laser-heated needleless electrospinning device according to claim 1, characterized in that, The collector is a flat plate or a roller, and the collection distance is 10~20cm.

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