An electrohydrodynamic near-field direct-write jetting method

Abstract

The application relates to a method for electrohydrodynamic near-field direct writing jet initiation, comprising an electrohydrodynamic direct writing device, and the method comprises the following steps: step one, far-field direct writing is carried out by using the direct writing device, and under the premise of not generating discharge breakdown, a critical value of jet initiation voltage at a minimum height and a minimum liquid supply flow is determined by adjusting a direct writing parameter, and far-field jet initiation is realized; step two, step one is repeated for multiple times, the height parameter is changed under the premise of ensuring a steady jet, and multiple groups of the height, voltage and liquid supply flow and the like are recorded for program editing, so that synchronous adjustment of the height, voltage and liquid supply flow is obtained; and step three, after far-field jet initiation under the minimum voltage according to the parameters obtained in step one, the height distance between the injection pump needle tip and the collection plate, the applied voltage and the liquid supply flow are reduced by program editing, the liquid column is ensured to be stable, and near-field direct writing jet initiation without interruption and breakdown is realized.

Description

Technical Field

[0001] This application relates to the technical field of direct writing of electrofluids, and more particularly to a method for initiating near-field direct writing jets of electrofluids. Background Technology

[0002] Electrospinning is a micro / nano additive manufacturing technology. Its typical setup consists of a syringe, a high-voltage DC power supply, a conductive collecting plate, and a solution (usually a polymer). Under certain process parameters, by applying a high-voltage electric field to the syringe containing the polymer solution and grounding the conductive collecting plate, disordered nanofiber films can be obtained on the collecting plate. In 2006, the discovery of near-field spinning provided a method for ordered nanoadditive manufacturing. It reduces the distance from the needle tip to the collecting plate to the hundreds of micrometers level, allowing the jet to fall onto the collecting plate before whipping, and utilizes the ordered segment of the jet for direct writing. Compared to traditional electrospinning, near-field direct writing applies voltages in the hundreds of volts range, and the substrate-needle tip distance is in the hundreds of micrometers range, resulting in more precise, ordered, and micro / nano-scale fiber deposition. Combined with a two-dimensional moving platform, near-field direct writing technology can achieve directional deposition of micro / nano films; by controlling the movement path of the two-dimensional moving platform, point deposition or deposition along a predetermined trajectory of micro / nano films can be achieved in a two-dimensional plane.

[0003] To date, current fluid direct writing technology still faces the following technical challenges:

[0004] Technical Issue 1: Electrofluid far-field direct writing can induce current emission simply by increasing the voltage, but the applied voltage must reach over 3000 volts. This means the induced jet velocity is extremely high, making it unsuitable for direct writing of micro / nano films using low- to medium-speed motion platforms. When the jet deposition velocity exceeds the collecting plate's moving speed, it can lead to fiber aggregation or yielding. For direct writing along straight trajectories, the motion platform's moving speed needs to be increased to match the jet velocity; for direct writing along corners or curved trajectories, it is often impossible to achieve this by adjusting the motion platform's performance. This indicates that electrofluid far-field direct writing technology requires high motion platform performance to directionally deposit micro / nanofibers.

[0005] Technical Issue 2: Compared to far-field direct writing of current-current fluid, near-field direct writing of current-current fluid achieves high-precision, low-speed direct writing by reducing the distance between the tip and the collector plate and the voltage. However, as the distance between the tip and the collector plate decreases, the air is easily broken down, and the electric field strength near the meniscus will be momentarily reduced, thus preventing the jet from being directly initiated. This is a major obstacle to the application of this technology. Summary of the Invention

[0006] To address the aforementioned problems and achieve high-precision, narrow-linewidth, low-speed near-field direct writing with no air breakdown and uninterrupted jet flow, this application provides a method for near-field direct writing jet initiation using a current-carrying fluid. The technical solution is as follows:

[0007] A method for initiating near-field direct-write jet in electrofluid includes an electrofluid direct-write device, wherein the electrofluid direct-write device includes a collection plate, a micro-injector, a precision injection pump, a temperature control device, a humidity control device, a two-dimensional motion platform, and a high-voltage power supply.

[0008] The temperature control device and humidity control device are used to regulate the direct writing inlet temperature and relative humidity; the micro-syringe is used to calculate and set the liquid supply flow rate and control the liquid flow rate provided by the precision injection pump; the high-voltage power supply is used to provide a stable DC voltage.

[0009] The near-field direct-write jet initiation method includes the following steps:

[0010] Step 1: Far-field direct writing is performed using an electrohydrodynamic direct writing device. The height distance between the collection plate and the tip of the precision injection pump is adjusted by the motion platform. The micro-syringe controls the precision injection pump to provide a minimum liquid supply flow rate to form a stable liquid droplet and sets parameters. The stable liquid droplet is formed when the liquid droplet at the tip of the precision injection pump forms a meniscus shape without applying voltage. The high-voltage power supply applies voltage, which is increased from zero until the air is broken down or a jet is generated. When a jet is generated, the liquid droplet at the tip of the precision injection pump changes from a meniscus shape to a cone shape. The height distance, voltage, and liquid supply flow rate parameters are adjusted multiple times to obtain the minimum height distance for far-field direct writing jet initiation and the critical value of the jet initiation voltage at the minimum height distance, thereby achieving far-field direct writing jet initiation at the minimum voltage.

[0011] Step 2: Repeat Step 1 multiple times. Under the premise of ensuring steady-state jet, change the height distance and record multiple sets of height distance, voltage and liquid supply flow rate parameters for program editing to achieve synchronous adjustment of height distance, voltage and liquid supply flow rate.

[0012] Step 3: After initiating far-field direct-write jet at the minimum voltage based on the parameters obtained in Step 1, the height distance between the precision injection pump needle tip and the collection plate, the applied voltage, and the liquid supply flow rate are simultaneously reduced by editing the program to ensure the stability of the liquid drop and achieve uninterrupted and non-breakdown initiation of near-field direct-write jet.

[0013] Optionally, the height distance induced by the far-field direct-write jet is in the range of 1000-2300 micrometers;

[0014] The initial jet height induced by the near-field direct-write jet is at least 100 micrometers;

[0015] The initial jet diameter induced by the near-field direct-write jet is within 3 micrometers;

[0016] The fiber width deposited by the near-field direct-write jet initiation method is in the range of 200-300 nanometers, and the thickness is within 100 nanometers.

[0017] Optionally, step one includes:

[0018] Step a: Place the collection plate on the motion platform, set the ambient temperature and relative humidity, and prepare the viscous PEO aqueous solution into the precision injection pump;

[0019] Step b: Adjust the height distance between the collection plate and the tip of the precision injection pump through the motion platform, set the initial height distance, control the precision injection pump to provide the minimum liquid supply flow rate and set the parameters, wait for the liquid to drip from the tip of the precision injection pump to form a meniscus shape, and then stop the liquid supply.

[0020] Step c: Adjust the height distance between the collection plate and the precision injection pump needle tip to a certain height distance value, start applying voltage to the precision injection pump needle tip, and observe the meniscus morphology under different voltages using an industrial camera.

[0021] Step d: Record the height, voltage, and liquid supply flow rate parameters when the air is broken down or a jet is generated;

[0022] Step e: Change the height distance value in step c, and repeat steps b, c, and d to obtain the minimum height distance induced by the far-field direct-write jet and the critical value of the jet-induced voltage at the minimum height distance.

[0023] Optionally, in step a, the ambient temperature is set to 25℃-30℃, and the relative humidity is set to 35%.

[0024] The viscous PEO aqueous solution is composed of 0.5g of PEO powder and 9.5g of deionized water.

[0025] Optionally, the collecting plate includes a metal receiving plate and conductive glass laid flat and fixed on the receiving plate.

[0026] Optionally, step c includes the following steps:

[0027] (1) Identify the deformation characteristics of the sagging meniscus, increase the voltage value until a jet or breakdown phenomenon is generated;

[0028] (2) If a jet is generated, identify the geometric characteristics of the meniscus and control the flow rate until the shape and size of the meniscus are stable.

[0029] In summary, this application has the following beneficial effects:

[0030] 1. On the one hand, this invention adjusts the far-field direct-write jet initiation parameters of the electrofluid, including solution concentration, applied voltage, liquid supply flow rate, distance between the syringe pump needle tip and the collecting plate, to obtain the critical parameters for meniscus deformation, so that the jet can be initiated at the minimum height and minimum voltage.

[0031] 2. In another aspect, based on the far-field direct writing parameters, the present invention reduces the applied voltage and spacing, and adjusts the liquid supply flow rate, thereby achieving high-precision narrow-linewidth near-field direct writing without air breakdown and without jet interruption.

[0032] 3. This invention effectively improves jet stability and deposition accuracy by regulating and acquiring far-field direct writing parameters. By regularly adjusting process parameters and observing the morphology and size of the meniscus, the initiation of far-field direct writing jets is investigated, and the optimal values ​​for far-field direct writing initiation jets are determined, reducing the difficulty of near-field jet generation. At the same time, the near-field jet is maintained, solving the problems of near-field breakdown and jet cessation, and improving the smoothness and continuity of high-precision printing. Attached Figure Description

[0033] Figure 1 This is a simplified experimental diagram of the current-fluid direct-write device in this embodiment;

[0034] Figure 2 This is a schematic diagram of the meniscus formed by the plumb line in this embodiment;

[0035] Figure 3 This is a schematic diagram of the cone-shaped droplet formation in this embodiment;

[0036] Figure 4 This is a diagram of the cone-shaped vertical liquid jet in this embodiment;

[0037] Figure 5 This is a diagram of the meniscus vertical fluid jet in this embodiment;

[0038] Figure 6 This is a diagram of PEO fibers with nanoline width in this embodiment.

[0039] Explanation of reference numerals in the attached diagram: 1. Microsyringe; 2. Collection plate. Detailed Implementation

[0040] The following is in conjunction with the appendix Figure 1-6 This application will be described in further detail.

[0041] This application discloses a method for initiating near-field direct-write jets of electrofluid. The method involves a high-precision, narrow-linewidth electrofluid direct-write device, which includes a collection plate 2, a micro-injector 1, a precision injection pump, a temperature control device, a humidity control device, a two-dimensional motion platform, and a high-voltage power supply. The equipment and instruments involved are assembled and used using existing electrofluid direct-write devices, and will not be described in detail here.

[0042] The instruments used in this electrohydrodynamic direct writing device include a temperature control device and a relative humidity device for adjusting the two most important environmental parameters for direct writing. The micro-syringe 1 is used to calculate and set the liquid supply flow rate. The precision injection pump, in conjunction with the micro-syringe 1, can provide a small liquid supply flow rate. The voltage source can provide a stable DC voltage.

[0043] The near-field direct-write jet initiation method includes the following steps:

[0044] Step 1: Use a current-current direct writing device for far-field direct writing. By adjusting the printing parameters, determine the critical values ​​of the jet initiation voltage under the minimum height and minimum voltage, and realize the initiation of far-field jet under the minimum voltage.

[0045] Step 2: Repeat Step 1 multiple times. Under the premise of ensuring steady-state jet, change the height parameter and record multiple sets of parameters such as height, voltage and flow rate for program editing to obtain synchronous adjustment of height, voltage and liquid supply flow rate.

[0046] Step 3: After performing far-field jet injection at minimum voltage based on the parameters obtained in Step 1, the height distance between the injection pump needle tip and the collecting plate, the applied voltage, and the liquid supply flow rate are adjusted and reduced by editing the program to ensure the stability of the liquid drop, ensure that the air is not broken down and the jet is not interrupted, and achieve high-precision narrow-linewidth current fluid near-field direct writing.

[0047] In step one, the control of printing parameters includes the motion platform adjusting the height distance between the collection plate 2 and the syringe pump tip, the micro-syringe 1 controlling the syringe pump to provide the minimum liquid supply flow rate, and the high-voltage power supply applying the voltage parameter.

[0048] By repeatedly adjusting parameters such as height, voltage, and liquid supply flow rate, the minimum height induced by far-field direct writing jet under minimum voltage and the critical value of jet-induced voltage under minimum voltage are obtained.

[0049] In step one, when performing direct writing using a current-volume direct writing device, the critical parameters for far-field direct writing jet initiation at the minimum height are obtained. Two technical methods are employed: observing the morphology and size of the meniscus and adjusting relevant parameters. The specific operations are as follows:

[0050] Step a: Place the collection plate 2 on the motion platform, set the ambient temperature and relative humidity, and prepare the viscous PEO aqueous solution into the precision injection pump;

[0051] Step b: Adjust the distance between the collection plate 2 and the syringe pump tip using the motion platform, setting an initial distance (1000 micrometers). Calculate the minimum liquid flow rate the syringe pump can provide based on the standard parameters of the injector and set the parameters. The micro-syringe 1 controls the syringe pump to provide the minimum liquid flow rate. Without applying voltage, wait for the liquid to drip from the tip of the syringe pump tip to form a meniscus. Figure 2 Then the fluid supply was stopped;

[0052] Step c: Adjust the distance between the collection plate 2 and the syringe pump needle tip to a certain height value, start applying voltage to the syringe pump needle tip, and observe the meniscus morphology under different voltages using an industrial camera.

[0053] The voltage applied to the syringe pump needle tip is increased from zero until the air is broken down or the meniscus becomes conical, such as... Figure 3 .

[0054] Step d: Slowly increase the voltage and record parameters such as the height, voltage, and fluid flow rate of the jet that cause the breakdown phenomenon (the phenomenon of the liquid changing from a meniscus to a cone shape or being broken down can be observed).

[0055] Step e: Change the height parameter in step c, and repeat steps b, c, and d to obtain the minimum height induced by the far-field jet under the minimum voltage and the critical value of the jet-induced voltage under the minimum voltage.

[0056] In step a, the ambient temperature is 25℃-30℃ and the relative humidity is 35%.

[0057] Preparation of viscous PEO aqueous solution: Dissolve 0.5g of PEO powder in 9.5g of deionized water, and stir the prepared solution in a magnetic stirrer for 12h to obtain a viscous PEO aqueous solution; then let the solution stand for two hours, place it in a vacuum chamber and evacuate to -0.1MPa and maintain it for 15 minutes; use microsyringe 1 to extract 10 μL of solution according to standard method to ensure that the solution is continuous and free of bubbles;

[0058] The collecting plate 2 consists of a metal receiving plate and conductive glass laid flat and fixed on the receiving plate.

[0059] In step e, the height parameters from step c are changed. When the height of the syringe pump needle tip-collecting plate 2 is 1000 micrometers, the air breaks down when the voltage increases from 0 kV to 2.1 kV. When the height is increased to 1100 micrometers, the air breaks down when the voltage increases from 0 kV to 2.2 kV. Similarly, when the height is increased to 2300 micrometers and the voltage increases from 0 kV to 2.8 kV, the meniscus transforms into a cone shape. At this point, the height of 2300 micrometers is the critical minimum height, and the voltage of 2.8 kV is the critical minimum voltage.

[0060] Among them, at a critical minimum height of 2300 micrometers and a critical minimum voltage of 2.8 kV, adjusting the flow rate of the syringe pump to 100 nl / min transforms the cone shape into a meniscus shape, resulting in a cone-shaped vertical liquid jet (such as...). Figure 4 ) transforms into meniscus sagging fluid jet (e.g. Figure 5 ).

[0061] To obtain the critical parameters for far-field direct-write jet initiation at the minimum height, in step c, two techniques are used to observe the meniscus morphology and adjust related parameters, as follows:

[0062] (1) Identify the characteristics of meniscus sagging deformation, increase the voltage value until a jet or breakdown phenomenon is generated;

[0063] (2) If a jet is generated, identify the geometric characteristics of the meniscus dripping fluid and control the fluid supply flow rate until the shape and size of the meniscus are stable.

[0064] Step two involves repeating step one, while maintaining a steady-state jet, by changing the height parameter and recording multiple sets of parameters such as height, voltage, and liquid supply flow rate for program editing, in order to achieve synchronous adjustment of the height, voltage, and liquid supply flow rate.

[0065] In step three, among the parameters obtained in steps one and two, the optimal parameters for jet initiation are selected, namely, the minimum receiving distance from the syringe pump tip to the collecting plate 2, the minimum flow rate that the syringe pump can provide in conjunction with the syringe, and the minimum voltage applied to the syringe pump tip. When initiating near-field jet according to the parameters obtained in step one, the program is edited to make the same adjustments based on the voltage, syringe pump tip-collecting plate 2 height, and flow rate balance obtained in step two, ensuring the stability of the plume and achieving uninterrupted and non-breakdown initiation of near-field direct-write jet.

[0066] Step two is performed as follows:

[0067] 1. Achieve far-field jet initiation under the conditions of a height of 2300 micrometers, a voltage of 2.8 kV, and a syringe pump flow rate of 100 nl / min. 2. Lower the height of the syringe pump needle tip-collector plate 2 to 2200 micrometers, and decrease the voltage at this point. Record the critical values ​​for jet termination and hold voltage, as well as the flow rate. Repeat the experiment multiple times, recording the obtained height-voltage-flow rate values.

[0068] The experimental data parameters are as follows:

[0069] Height (μm) 2200 2100 2000 1900 1800 1700 1600 1500 1400 Voltage (kV) 1.25 1.25 1.25 1.25 1.15 1.15 1.15 1.15 1.10 Flow rate (nl / min) 100 80 50 45 40 35 30 25 20

[0070] Height (μm) 1300 1200 1100 1000 900 800 700 600 500 Voltage (kV) 1.05 1.00 1.03 0.94 0.90 0.84 0.80 0.75 0.85 Flow rate (nl / min) 15 10 5 1 0.5 0.2 0.1 0.05 0.06

[0071] Step three is performed as follows:

[0072] 1. Edit the program based on the parameters obtained in Step 1 and Step 2. First, generate the far-field jet at a height of 2300 micrometers. Then, adjust the height, voltage, and liquid supply flow rate to meet the requirements of uninterrupted jet flow and no air breakdown. This achieves high-precision, narrow-linewidth, low-speed near-field direct writing at a height of 500 micrometers, a voltage of 850V, and a liquid supply flow rate of 0.06nl / min.

[0073] 2. Based on the jetting conditions provided in section 1, directly write multiple PEO fibers with linewidths of 200 nm to 300 nm, such as... Figure 5 .

[0074] It is worth noting that the height of the far-field direct-write jet in this application ranges from 1000 to 2300 micrometers, the initial jet height of the near-field direct-write jet initiation can be as low as 100 micrometers, the initial jet diameter of the near-field direct-write jet initiation is within 3 micrometers, and the fiber width deposited by the near-field direct-write jet initiation method ranges from 200 to 300 nanometers, and the thickness ranges within 100 nanometers.

[0075] The program controls the reduction of the height and voltage of the syringe pump needle-collecting plate 2, and the height and voltage are optimized as a function of time.

[0076] Adjust the flow rate of the syringe pump to maintain the stability of the plume or the formed meniscus and cone, ensuring that the air is not broken down and the jet is not interrupted, so as to achieve near-field direct writing of the electrofluid.

[0077] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for initiating near-field direct-write jet induction using a current-fluid system, comprising a current-fluid direct-write apparatus, characterized in that: The electrofluid direct writing device includes a collection plate, a micro-syringe, a precision injection pump, a temperature control device, a humidity control device, a two-dimensional motion platform, and a high-voltage power supply. The temperature control device and humidity control device are used to regulate the temperature and relative humidity of the direct writing environment; the micro-syringe is used to calculate and set the liquid supply flow rate and control the liquid supply of the precision injection pump; the high-voltage power supply is used to provide a stable DC voltage. The near-field direct-write jet initiation method includes the following steps: Step 1: Far-field direct writing is performed using an electrohydrodynamic direct writing device. The height distance between the collection plate and the tip of the precision injection pump is adjusted by the motion platform. The micro-syringe controls the precision injection pump to provide a minimum liquid supply flow rate to form a stable liquid droplet and sets parameters. The stable liquid droplet is formed when the liquid droplet at the tip of the precision injection pump forms a meniscus shape without applying voltage. The high-voltage power supply applies voltage, which is increased from zero until the air is broken down or a jet is generated. When a jet is generated, the liquid droplet at the tip of the precision injection pump changes from a meniscus shape to a cone shape. The height distance, voltage, and liquid supply flow rate parameters are adjusted multiple times to obtain the minimum height distance for far-field direct writing jet initiation and the critical value of the jet initiation voltage at the minimum height distance, thereby achieving far-field direct writing jet initiation at the minimum voltage. Step 2: Repeat Step 1 multiple times. Under the premise of ensuring steady-state jet, change the height distance and record multiple sets of height distance, voltage and liquid supply flow rate parameters for program editing to achieve synchronous adjustment of height distance, voltage and liquid supply flow rate. Step 3: After initiating far-field direct-write jet at the minimum voltage based on the parameters obtained in Step 1, the height distance between the precision injection pump needle tip and the collection plate, the applied voltage, and the liquid supply flow rate are simultaneously reduced by editing the program to ensure the stability of the liquid drop and achieve uninterrupted and non-breakdown initiation of near-field direct-write jet.

2. The method for initiating near-field direct-write jet induction of a current-carrying fluid according to claim 1, characterized in that: The height range induced by the far-field direct-write jet is 1000-2300 micrometers; The initial jet height induced by the near-field direct-write jet is at least 100 micrometers; The initial jet diameter induced by the near-field direct-write jet is within 3 micrometers; The fiber width deposited by the near-field direct-write jet initiation method is in the range of 200-300 nanometers, and the thickness is within 100 nanometers.

3. The method for initiating near-field direct-write jets of electrofluid according to claim 1, characterized in that: Step one includes: Step a: Place the collection plate on the motion platform, set the ambient temperature and relative humidity, and prepare the viscous PEO aqueous solution into the precision injection pump; Step b: Adjust the height distance between the collection plate and the tip of the precision injection pump through the motion platform, set the initial height distance, control the precision injection pump to provide the minimum liquid supply flow rate and set the parameters, wait for the liquid to drip from the tip of the precision injection pump to form a meniscus shape, and then stop the liquid supply. Step c: Adjust the height distance between the collection plate and the precision injection pump needle tip to a certain height distance value, start applying voltage to the precision injection pump needle tip, and observe the meniscus morphology under different voltages using an industrial camera. Step d: Record the height, voltage, and liquid supply flow rate parameters when the air is broken down or a jet is generated; Step e: Change the height distance value in step c, and repeat steps b, c, and d to obtain the minimum height distance induced by the far-field direct-write jet and the critical value of the jet-induced voltage at the minimum height distance.

4. The method for initiating near-field direct-write jets of electrofluid according to claim 3, characterized in that: In step a, the ambient temperature is set to 25℃-30℃, and the relative humidity is set to 35%. The viscous PEO aqueous solution is composed of 0.5g of PEO powder and 9.5g of deionized water.

5. The method for initiating near-field direct-write jet induction of a current-carrying fluid according to claim 4, characterized in that: The collecting plate includes a metal receiving plate and conductive glass laid flat and fixed on the receiving plate.

6. The method for initiating near-field direct-write jets of electrofluid according to claim 3, characterized in that: Step c includes the following steps: (1) Identify the deformation characteristics of the sagging meniscus, increase the voltage value until a jet or breakdown phenomenon is generated; (2) If a jet is generated, identify the geometric characteristics of the meniscus and control the flow rate until the shape and size of the meniscus are stable.

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