Electrostatic spinning method and device for airflow-assisted constraint jet flow

Abstract

The invention discloses an airflow-assisted constraint jet electrostatic spinning method and device, the airflow-assisted constraint jet electrostatic spinning device comprises a jet device, a receiving device, a high-voltage electrostatic generator and an airflow assisting device, and the airflow assisting device comprises an air path system and an auxiliary nozzle coaxially sleeving the outer side of a spray head of the jet device; an annular airflow channel is formed between the auxiliary nozzle and the spray head; constraint airflow coaxially wrapping the periphery of jet flow ejected from the spray head is output through the airflow channel so as to restrain swing of the jet flow. When the jet flow is ejected from the tail end of the spray head, constraint airflow coaxially wrapping the periphery of the jet flow is applied; the airflow direction of the constraint airflow is consistent with the initial movement direction of the jet flow, and the flow of the constraint airflow can generate continuous radial constraint force on non-axial swing of the jet flow, so that unstable swing of the jet flow under the action of electric field force is actively inhibited. The coaxial laminar flow constraint air sheath is applied to form a composite field with an electrostatic field, jet flow swing is actively inhibited, and stable controlled stretching is achieved.

Description

Technical Field

[0001] This invention belongs to the field of electrospinning technology, and particularly relates to an electrospinning method and apparatus for airflow-assisted constrained jet. Background Technology

[0002] In electrospinning technology, polymer jets driven by high-voltage electrostatic fields experience severe whipping instability. While this instability helps to stretch and refine the jet, it also severely leads to the uncontrollability of the jet trajectory and the final deposited fibers. This directly causes problems such as wide pore size distribution, uneven fiber diameter, and excessively large material deposition area in the fiber membrane, restricting its application in fields requiring precise structures, such as tissue engineering scaffolds and high-efficiency filtration membranes. Existing technologies sometimes improve stability by changing the shape of the receiving device, controlling the ambient atmosphere, or designing multi-field coupling. However, most of these methods have limited effectiveness and fail to provide effective and direct intervention and control over the core region of jet instability: the initial stage to the onset of oscillation instability. Summary of the Invention

[0003] Purpose of the invention: In order to overcome the shortcomings of the prior art, the present invention provides an electrospinning method and apparatus for airflow-assisted constrained jets. By applying a coaxial laminar flow constrained air sheath, a composite field is formed with the electrostatic field, which actively suppresses jet oscillation and achieves stable and controlled stretching.

[0004] Technical solution: To achieve the above objectives, the present invention provides an electrospinning method for airflow-assisted constrained jets, comprising the following steps:

[0005] S1: Provide at least one jetting device and at least one receiving device, and establish a high-voltage electrostatic field between the corresponding jetting device and the receiving device;

[0006] S2: The spinning solution is driven to be ejected from the nozzle end of the jet device to form a jet, and the jet moves toward the receiving device and is stretched and refined under the action of the high voltage electrostatic field.

[0007] S3: At the same time as the jet is ejected from the nozzle end, a constraining airflow is applied coaxially around the jet; the airflow direction of the constraining airflow is consistent with the initial motion direction of the jet, and its flow energy generates a continuous radial constraining force on the non-axial oscillation of the jet, so as to actively suppress the unstable oscillation of the jet under the action of electric field force.

[0008] Furthermore, the constrained airflow is a laminar flow constrained air sheath that is coaxial with and tightly wrapped around the jet, applied through an airflow channel surrounding the nozzle. This laminar flow constrained air sheath and the high-voltage electrostatic field together constitute a composite field for stabilizing the jet.

[0009] The laminar confined gas sheath, through its hydrodynamic action, applies a radial focusing force pointing towards the axis to the jet that is unstable under the action of the electric field and attempts to generate non-axial oscillation. This radial focusing force is opposite to the oscillation displacement trend of the jet, so as to form a dynamically stable guiding zone between the initial section of the jet and the starting section of the oscillation instability, which is used to suppress the instability of jet whipping and realize the controlled stable stretching of the jet in the composite field.

[0010] Furthermore, the laminar flow confinement sheath is generated through an annular air gap surrounding the nozzle.

[0011] Furthermore, the ratio of the equivalent diameter of the annular air gap to the outer diameter of the nozzle is 1.5:1 to 5:1.

[0012] Furthermore, the flow rate and / or pressure of the constrained airflow can be independently adjusted according to at least one of the physicochemical properties of the spinning solution, namely viscosity, surface tension, or conductivity.

[0013] An electrospinning apparatus for airflow-assisted confined jet, comprising:

[0014] A jetting device for storing and pumping spinning solution;

[0015] A receiving device, disposed opposite to the jet device, is used to collect the fibers formed by the jet;

[0016] A high-voltage electrostatic generator, whose positive and negative poles are electrically connected to the jet device and the receiving device respectively, is used to establish a high-voltage electrostatic field between the two.

[0017] The device includes an airflow assist device, which comprises an air path system and an auxiliary nozzle coaxially sleeved on the outside of the nozzle of the jet device; the auxiliary nozzle and the nozzle form an annular airflow channel; the air path system is used to provide a stable air source and output a constrained airflow coaxially wrapped around the jet ejected from the nozzle through the airflow channel to suppress the oscillation of the jet.

[0018] Furthermore, the end outlet of the auxiliary nozzle is flush with or protrudes from the end of the nozzle.

[0019] Furthermore, the annular outlet at the end of the airflow channel forms an annular air gap; the ratio of the equivalent diameter of the annular air gap to the outer diameter of the nozzle is 1.5:1 to 5:1.

[0020] Furthermore, the airflow assist device also includes an airflow rectification structure, which is used to make the flowing airflow tend to be laminar, so as to form a laminar confined air sheath at the outlet of the airflow channel;

[0021] The airflow rectification structure is fixedly installed inside the auxiliary nozzle and located upstream of the airflow channel; the airflow rectification structure includes at least one layer of honeycomb and / or at least one layer of rectification screen.

[0022] Furthermore, the gas path system is equipped with a flow and pressure regulating mechanism, which can independently regulate the flow rate and / or pressure of the constrained airflow;

[0023] The flow and pressure regulating mechanism is integrated into the gas path system, which includes a pressure regulating valve and a precision throttle valve connected in sequence along the airflow direction; the pressure regulating valve is used to set and stabilize the base pressure of the gas source, and the precision throttle valve is used to precisely regulate the volumetric flow rate of the constrained airflow; the gas path system is also equipped with a metering instrument for monitoring airflow parameters.

[0024] Beneficial effects: This invention forms a dynamically stable guiding zone in the critical initial stage of jet instability through the combined action of coaxial laminar flow confinement sheath and high-voltage electrostatic field. It applies a radial focusing force to the jet pointing towards the axis, thereby directly and actively suppressing its non-axial oscillation, significantly improving the stability and predictability of the jet trajectory, and thus enabling the production of fiber products with more uniform diameter distribution and more precise deposition. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the electrospinning method of the present invention;

[0026] Figure 2 This is a schematic diagram of the electrospinning apparatus of the present invention. Detailed Implementation

[0027] The invention will now be further described with reference to the accompanying drawings.

[0028] like Figure 1 As shown, an electrospinning method for airflow-assisted constrained jet includes the following steps:

[0029] S1: Provide at least one jet device 1 and at least one receiving device 2, and establish a high-voltage electrostatic field between the corresponding jet device 1 and the receiving device 2.

[0030] S2: The spinning solution is driven to be ejected from the end of the nozzle 11 of the jet device 1 to form a jet 31. The jet 31 moves toward the receiving device 2 under the action of the high voltage electrostatic field and is stretched and refined.

[0031] S3: At the same time as the jet 31 is ejected from the end of the nozzle 11, a constraining airflow 32 is applied coaxially around the jet 31; the airflow direction of the constraining airflow 32 is consistent with the initial motion direction of the jet 31, and its flow energy generates a continuous radial constraining force on the non-axial oscillation of the jet 31, so as to actively suppress the unstable oscillation of the jet under the action of the electric field force.

[0032] The deeper principle of electrospinning in this invention lies in establishing a stable gas boundary layer between the jet 31 and its surrounding environment by introducing a confined airflow 32 precisely coaxial with the jet 31. When the jet 31 exhibits a radial oscillation tendency due to charge repulsion and external disturbances in a high-voltage electrostatic field, the confined airflow 32 provides stabilization through two main mechanisms: first, a viscous drag mechanism, where the viscous force generated by the velocity gradient between the high-speed airflow and the low-speed (or stationary) ambient air carries surrounding air downstream, forming a radial supplementary flow pointing towards the axis; second, the Bernoulli effect, where the static pressure in the high-speed airflow region decreases, creating a low-pressure zone around the jet 31 and generating a centripetal pressure difference for the jet deviating from its axis. These two mechanisms work together to form a continuous radial confining force, directly counteracting the non-axial oscillation tendency of the jet 31, thereby actively suppressing the instability of the jet.

[0033] The constrained airflow 32 is a laminar flow constrained air sheath that is coaxial with and tightly wraps around the jet 31, applied through an airflow channel surrounding the nozzle 11. The laminar flow constrained air sheath and the high-voltage electrostatic field together form a composite field for stabilizing the jet. The laminar flow constrained air sheath, through its hydrodynamic action, applies a radial focusing force e pointing towards the axis to the jet that is unstable under the action of the electric field force and attempts to generate non-axial oscillation. The radial focusing force e is opposite to the oscillation displacement trend of the jet 31, so as to form a dynamically stable guiding zone c between the initial section a of the jet and the oscillation instability initiation section b, which is used to suppress the instability of jet whipping and realize the controlled stable stretching of the jet 31 in the composite field.

[0034] A laminar confined gas sheath is a gas structure with a specific geometry. It begins at the annular air gap outlet and extends downstream, forming a cone-shaped or trumpet-shaped laminar gas envelope that gradually expands outwards from the outlet. At the outlet, the gas sheath adheres tightly to the surface of the jet 31. As it moves downstream, its outer boundary continues to expand outwards due to the shearing and mixing action between the gas sheath and the surrounding air until energy is dissipated. The effective area of ​​the gas sheath covers the jet 31 from its initial straight section to the unstable initiation section where it begins to oscillate; this area is crucial for controlling the subsequent trajectory of the jet. The laminar confined gas sheath and the high-voltage electrostatic field together constitute a composite field. The electrostatic field primarily provides the axial tensile force to drive the jet 31, while the gas sheath specifically provides the radial stabilizing force to suppress oscillation. When the jet 31 becomes unstable under the influence of the electric field and exhibits a radial displacement tendency, the laminar characteristics of the gas sheath ensure the uniformity and stability of the force, forming a radially converging force e pointing towards the axis through the combined action of viscous drag and pressure difference. The radial focusing force e is opposite to the displacement trend of the jet 31, forming a dynamic negative feedback mechanism. This creates an effective guiding zone c in the most sensitive unstable initial segment of the jet, fundamentally improving the initial conditions of the jet and achieving controlled and stable stretching of the jet in the composite field.

[0035] More specifically, the laminar flow confinement sheath is generated by an annular air gap surrounding the nozzle. The annular air gap is formed between the auxiliary nozzle 42, coaxially fitted around the outside of the nozzle 11, and the outer wall of the nozzle 11. This geometry generates a naturally axisymmetric annular airflow, ensuring uniform envelopment of the jet 31. The dimensional accuracy and concentricity of the annular air gap directly determine the quality of the confinement sheath. A precisely machined annular air gap can generate a stable and symmetrical laminar flow sheath, avoiding the introduction of additional disturbances due to airflow asymmetry.

[0036] The ratio of the equivalent diameter of the annular air gap to the outer diameter of the nozzle is between 1.5:1 and 5:1. The equivalent diameter of the annular air gap is defined as the hydraulic diameter of the air gap; for annular gaps, its equivalent diameter is equal to the difference between the outer and inner diameters. This ratio is within a preferred range. When the ratio is too small (<1.5), the airflow channel is too narrow, easily generating high-speed turbulence, and the constraint range is limited; when the ratio is too large (>5), the airflow is too divergent, unable to form a tightly enveloping gas sheath, and the constraint effect is significantly reduced. Within this preferred range, the airflow can maintain a stable laminar flow state, forming a tight and effective gas enveloping layer, achieving the best constraint effect on the jet.

[0037] The flow rate and / or pressure of the confining gas flow can be independently adjusted based on at least one of the physicochemical properties of the spinning solution, namely viscosity, surface tension, or conductivity. Spinning solutions with different physicochemical properties exhibit different rheological and electrical characteristics during electrospinning, leading to significant differences in their instability behavior. High-viscosity solutions typically require stronger confining forces to suppress their oscillations, while low-surface-tension solutions may be more sensitive to airflow disturbances. By independently adjusting the flow rate and pressure of the confining gas flow, the momentum and intensity of the confining gas sheath can be precisely controlled, thereby optimizing the configuration for the characteristics of different solutions.

[0038] like Figure 2 As shown, an electrospinning device with airflow-assisted constrained jet includes: a jet device 1 for storing and pumping a spinning solution; a receiving device 2, disposed opposite to the jet device 1, for collecting fibers formed by the jet; a high-voltage electrostatic generator 3, whose positive and negative poles are electrically connected to the jet device 1 and the receiving device 2 respectively, for establishing a high-voltage electrostatic field between them; and an airflow assist device 4, which includes an air path system 41 and an auxiliary nozzle 42 coaxially sleeved outside the nozzle 11 of the jet device 1; an annular airflow channel 43 is formed between the auxiliary nozzle 42 and the nozzle 11; the air path system 41 provides a stable air source and outputs a constrained airflow coaxially surrounding the jet ejected from the nozzle 11 through the airflow channel 43 to suppress the oscillation of the jet. The coaxial sleeve design of the auxiliary nozzle 42 and the nozzle 11 ensures the precise alignment of the constrained airflow 32 with the jet 31, which is a prerequisite for achieving uniform wrapping. When the air supply system 41 supplies air, the annular airflow channel 43 can generate a stable and symmetrical airflow field, thereby combining airflow control with electric field control to form a composite field control that suppresses jet oscillation and achieves stable and controlled stretching of the jet.

[0039] The end outlet of the auxiliary nozzle 42 is flush with the end of the nozzle 11. When they are flush, the constrained airflow 32 begins to act the instant the jet 31 is formed, ensuring that the jet 31 is under control from the beginning. In another embodiment, the auxiliary nozzle 42 may protrude from the end of the nozzle 11. When the auxiliary nozzle 42 protrudes, a longer pre-constraint region can be formed, further enhancing the stabilizing effect on the initial stage of the jet.

[0040] It is important to note that in embodiments where the auxiliary nozzle 42 protrudes from the end of the nozzle 11, the preferred protrusion length is between 0.1 mm and 5 mm. This is because: the lower limit (0.1 mm) ensures that the constrained airflow contacts the ambient air before the jet, forming a pre-flow guidance zone. If the protrusion is too short (e.g., less than 0.1 mm), the establishment of the air sheath will be slightly delayed, failing to provide the most effective constraint at the moment the jet leaves the outlet, thus weakening the stabilizing effect on the initial and most sensitive section of the jet. The upper limit (5 mm) prevents a series of adverse effects caused by an excessively long protrusion. First, an excessively long protrusion will significantly distort the electric field distribution at the annular air gap outlet, potentially interfering with the normal initiation of the jet. Second, when the airflow flows within a longer protrusion section, its momentum and stability will decrease, and it may mix with the ambient air prematurely, resulting in a decrease in airflow quality and weakened constraint force upon reaching the jet surface. Therefore, a protrusion range of 0.1 mm to 5 mm can achieve a better balance between ensuring effective pre-guidance, not affecting the electric field distribution, and maintaining airflow quality and structural strength.

[0041] The annular outlet at the end of the airflow channel 43 forms an annular air gap; the ratio of the equivalent diameter of the annular air gap to the outer diameter of the nozzle 11 is 1.5:1 to 5:1. Under this preferred ratio, the airflow channel can ensure sufficient flow capacity while maintaining a stable laminar flow state, ensuring that the confined air sheath has appropriate thickness and velocity distribution.

[0042] The airflow assist device 4 also includes an airflow rectification structure 44, which is used to laminate the flowing air to form a laminar confined air sheath at the outlet of the airflow channel 43. The airflow rectification structure 44 is fixedly installed inside the auxiliary nozzle 42 and located upstream of the airflow channel 43. The airflow rectification structure 44 includes at least one layer of honeycomb and / or at least one layer of rectifying screen. The airflow rectification structure 44 is a key component to ensure airflow quality. The honeycomb consists of a large number of parallel small channels, which can effectively break up large-scale vortices and initially order the airflow; the rectifying screen further eliminates small-scale turbulence through its fine mesh, making the airflow velocity distribution more uniform. This combined rectification scheme can fully develop the turbulence from the air source into laminar flow, providing the necessary preconditions for forming a stable confined air sheath.

[0043] The gas path system 41 is equipped with a flow and pressure regulating mechanism 45, which can independently regulate the flow rate and / or pressure of the constrained airflow. The flow and pressure regulating mechanism 45 is integrated into the gas path system 41 and includes a pressure regulating valve 45a and a precision throttle valve 45b connected sequentially along the airflow direction. The pressure regulating valve 45a is used to set and stabilize the base pressure of the gas source, and the precision throttle valve 45b is used to precisely regulate the volumetric flow rate of the constrained airflow. The gas path system 41 is also equipped with a metering instrument 45c for monitoring airflow parameters. The flow and pressure regulating mechanism 45 constitutes a complete airflow parameter control system. The pressure regulating valve 45a first regulates the unstable gas source pressure to a set stable value, providing a basis for subsequent precise control. The precision throttle valve 45b achieves fine control of the volumetric flow rate by finely adjusting the flow channel area. The metering instrument 45c provides real-time pressure and flow monitoring, enabling the operator to accurately grasp the airflow status and make timely adjustments.

[0044] In summary, this invention, through the combined action of a coaxial laminar flow confined gas sheath and a high-voltage electrostatic field, forms a dynamically stable guiding zone in the critical initial stage of jet instability. This zone applies a radial focusing force pointing towards the axis to the jet, thereby directly and actively suppressing its non-axial oscillation, significantly improving the stability and predictability of the jet trajectory, and ultimately enabling the production of fiber products with more uniform diameter distribution and more precise deposition.

[0045] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An electrospinning method of airflow assisted constricted jet, characterized in that: The method comprises the following steps: S1: providing at least one jet device and at least one receiving device, and establishing a high-voltage electrostatic field between the corresponding jet device and the receiving device; S2: driving the spinning solution to be ejected from the nozzle end of the jet device to form a jet, which moves to the receiving device under the action of the high-voltage electrostatic field and is stretched and refined; S3: while the jet is ejected from the nozzle end, a restraining gas flow coaxially wrapped around the periphery of the jet is applied; the gas flow direction of the restraining gas flow is consistent with the initial movement direction of the jet, and the flow energy thereof generates a continuous radial restraining force on the non-axial swing of the jet to actively suppress the unstable swing of the jet under the action of the electric field force.

2. The electrospinning method of a gas flow assisted constricted jet according to claim 1, wherein: The restraining gas flow is a laminar flow restraining gas sheath coaxially and tightly wrapped around the jet applied through a gas flow channel arranged around the periphery of the nozzle, and the laminar flow restraining gas sheath and the high-voltage electrostatic field jointly constitute a composite field for stabilizing the jet; Wherein, the laminar flow restraining gas sheath applies a radial bunching force to the jet that loses stability and tries to produce non-axial swing under the action of the electric field force, the radial bunching force is directed to the axial center and is opposite to the swing displacement trend direction of the jet, so as to form a dynamic stable guide zone between the initial segment and the swing instability starting segment of the jet, for suppressing the instability of the jet whipping and realizing the controlled stable stretching of the jet in the composite field.

3. The electrospinning method of a gas flow assisted constricted jet according to claim 2, wherein: The laminar flow restraining gas sheath is generated by a ring-shaped air gap arranged around the periphery of the nozzle.

4. The electrospinning method of flow-assisted constricted jet according to claim 3, wherein: The ratio of the equivalent diameter of the ring-shaped air gap to the outer diameter of the nozzle is 1.5:1 to 5:

1.

5. The electrospinning method of flow-assisted constricted jet according to claim 1, wherein: The flow rate and / or pressure of the restraining gas flow can be independently adjusted according to at least one physicochemical property of the spinning solution, such as viscosity, surface tension or electrical conductivity.

6. An electrospinning device for airflow-assisted constricted jet, characterized in that: It comprises: a jet device (1) for storing and pumping spinning solution; a receiving device (2) arranged opposite to the jet device (1) for collecting fibers formed by the jet; a high-voltage electrostatic generator (3) electrically connected to the jet device (1) and the receiving device (2) respectively for establishing a high-voltage electrostatic field therebetween; and a gas flow auxiliary device (4) comprising a gas path system (41) and an auxiliary nozzle (42) coaxially sleeved outside the nozzle (11) of the jet device (1); the auxiliary nozzle (42) and the nozzle (11) form a ring-shaped gas flow channel (43); the gas path system (41) is used to provide a stable gas source and output a restraining gas flow coaxially wrapped around the periphery of the jet ejected from the nozzle (11) through the gas flow channel (43) to suppress the swing of the jet.

7. The electrospinning device of claim 6, wherein: The end outlet of the auxiliary nozzle (42) is flush with or protrudes from the end of the nozzle (11).

8. The electrospinning device of claim 7, wherein: The ring-shaped outlet at the end of the gas flow channel (43) constitutes a ring-shaped air gap; the ratio of the equivalent diameter of the ring-shaped air gap to the outer diameter of the nozzle (11) is 1.5:1 to 5:

1.

9. The electrospinning device of claim 6, wherein: The airflow auxiliary device (4) further comprises an airflow rectifying structure (44) for tending to laminarize the airflow flowing therethrough to form a laminar flow-restricted gas sheath at the outlet of the airflow channel (43); The airflow rectifying structure (44) is fixedly installed inside the auxiliary nozzle (42) and located upstream of the airflow channel (43); the airflow rectifying structure (44) comprises at least one layer of honeycomb and / or at least one layer of rectifying screen.

10. The electrospinning device of claim 6, wherein: The gas path system (41) is provided with a flow rate and pressure adjusting mechanism (45) capable of independently adjusting the flow rate and / or pressure of the restricted airflow; The flow rate and pressure adjusting mechanism (45) is integrated in the gas path system (41) and comprises a pressure regulating valve (45a) and a precision throttle valve (45b) connected in sequence along the airflow direction; the pressure regulating valve (45a) is used for setting and stabilizing the basic pressure of the gas source, and the precision throttle valve (45b) is used for accurately adjusting the volume flow rate of the restricted airflow; the gas path system (41) is further provided with a metering instrument (45c) for monitoring the airflow parameters.

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