Structure and Method of Electrostatic Printing Nozzle for Micro / Nano Structures on Insulating Substrate Assisted by Ion Wind

Abstract

An ion wind-assisted electrostatic printing nozzle structure and method for micro / nano structures on insulating substrate surfaces includes an electrostatic printing nozzle, with an ion wind generating module coaxially connected to the outer side of the nozzle. The inlet at the top of the nozzle is connected to a driving air pressure source, and the nozzle at the bottom is connected to a high-voltage power supply. The ion wind generating module has a built-in ionization electrode that generates positive and negative ions upon applying a high voltage. These ions are then driven by airflow to form an ion wind, which is focused on the printing area below the nozzle, keeping the insulating substrate surface in a near-zero potential state, thus forming a virtual grounding electrode. This invention utilizes ion wind to construct a virtual grounding electrode on the insulating surface, solving the problem of unstable electric field during printing caused by variations in printing height and charge accumulation on the insulating surface, thereby improving the applicability of electrostatic printing to insulating substrates.

Description

Technical Field

[0001] This invention relates to the field of electrostatic printing technology, specifically to an ion wind-assisted electrostatic printing nozzle structure and method for micro / nano structures on the surface of an insulating substrate. Background Technology

[0002] Electrostatic printing is a micro-nano additive manufacturing technology based on electrohydrodynamic traction ink jet deposition. By applying a high voltage of thousands of volts to the nozzle, a strong electric field is formed between the nozzle and the grounded receiving substrate. The electric field force "pulls" the ink out of the nozzle to form a Taylor cone, generating a jet much smaller than the nozzle diameter. It can print micro-nano structures with high resolution and controllability, and has broad application prospects in micro-nano electronics, biological tissue engineering and other fields.

[0003] In existing electrostatic printing technologies, methods such as applying periodic pulsed AC voltage and introducing electrode rings (see patent application titled "Inline Electrostatic Printing Nozzle and Printing Method for Suppressing Jet Interference," publication number: CN112644178B) and electrostatic lenses (see patent application titled "An Electrostatic Focusing Electrostatic Printing Device and Method," publication number: CN109532242B) to form a gradient electric field are commonly used to enhance the electric field strength between the nozzle and the receiving substrate, thereby improving the stability of electrostatic printing. However, this method is difficult to implement on insulating curved substrates with large thickness variations. Another patent (see patent application titled "An Electrostatic Printing Method and Device with Electric Field-Flow Field Hybrid Control," publication number: CN108340681B) forms a focused, stable fluid flow field below the printhead to overcome the problem of conventional electrostatic printing failing to print on insulating or free-form substrates. However, this method does not fundamentally eliminate the influence of residual charge. Other patents (named "A Sheet Plasma-Driven Arrayed Electrostatic Printing Device and Method", publication number: CN116198221B; and "A Plasma-Based Anti-Crosstalk Arrayed Electrostatic Printing Device and Method", publication number: CN115972769B) propose a plasma-driven electrostatic printing method. This method utilizes alternating positive and negative plasma generated by applying pulse voltage to bombard the target surface, charging the insulating substrate to form an electric field, thereby achieving electrostatic printing on the insulating substrate. This method effectively avoids the problem of residual charge generation, but the alternating changes in positive and negative voltages can cause fluctuations in the electric field strength, affecting the stability of the Taylor cone.

[0004] In summary, due to the limitations of the high-voltage electric field, electrostatic printing is difficult to achieve stable printing on thick insulating substrates or insulating substrates with large variations in surface contour height. On the one hand, the electric field strength decreases as the distance between the nozzle and the grounded substrate increases, failing to provide sufficient electric field traction for electrostatic printing. On the other hand, the charge induced by the high-voltage nozzle and the residual charge inside the deposited ink accumulate on the insulating surface and cannot be transferred, causing electrostatic repulsion of the ink in subsequent printing and affecting the continuity of electrostatic printing. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention aims to provide an electrostatic printing nozzle structure and method for micro-nano structures on insulating substrate surfaces assisted by ion wind. By utilizing ion wind to construct a virtual grounding electrode on the insulating surface, the problem of unstable electric field during printing caused by changes in printing height and charge accumulation on the insulating surface is solved, thereby improving the applicability of electrostatic printing to insulating substrates.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] An electrostatic printing nozzle structure for micro / nano structures on an insulating substrate surface assisted by ion wind includes an electrostatic printing nozzle 1, with an ion wind generating module 2 coaxially connected to the outside of the electrostatic printing nozzle 1; the upper inlet of the electrostatic printing nozzle 1 is connected to a driving air pressure source 101, and the nozzle 102 at the bottom of the electrostatic printing nozzle 1 is connected to a high-voltage power supply 103; the ion wind generating module 2 has an ionization electrode 201 built in it, which generates positive and negative ions after applying a high voltage, and is driven by airflow to form an ion wind, which is focused on the printing area below the nozzle 102, so that the surface of the insulating substrate 3 is always in a near-zero potential state, forming a virtual grounding electrode.

[0008] The nozzle 102 is a conductive nozzle, and a stainless steel needle or a gold-plated glass needle is selected. The outer layer of the nozzle 102 is coated with an insulating material, and the insulating material is selected as rubber or silicone.

[0009] The electrostatic printhead 1 is filled with functional ink 104, which is a conductive functional ink containing metal nanoparticles of gold, silver and copper, or a sensing functional ink containing nanomaterials of carbon nanotubes, silver nanowires and MXene.

[0010] The ion wind generating module 2 has an airflow inlet 202 at the top, with an ionization electrode 201 connected inside, and an airflow outlet 203 at the bottom. The ion wind generating module 2 has two or more ionization electrodes 201 connected inside, which are evenly distributed in a ring around the central electrostatic printing nozzle 1. The high voltage applied to them is AC or positive and negative DC, with an amplitude range of 1kV-50kV and an AC frequency of 1Hz-1000Hz. There is an airflow inlet 202 between every two ionization electrodes 201. The airflow enters the ion wind generating module 2 through the airflow inlet 202 and blows out the ion wind from the airflow outlet 203. The gas introduced is air, nitrogen or argon.

[0011] The airflow outlet 203 is inclined inward at an angle of 15°-75°, focusing on the nozzle 102 so that the blown ion air is gathered in the printing area; the airflow outlet 203 is at least 30mm away from the nozzle 102.

[0012] The insulating substrate 3 is a planar substrate or a curved substrate, and the material is glass, plastic, silicone rubber, paper or fabric. The height of the surface of the insulating substrate 3 from the bottom surface ranges from 1mm to 1m.

[0013] The electrostatic printing nozzle 1 and the ion wind generating module 2 are mounted on a three-axis or higher motion module or a multi-axis robotic arm.

[0014] The method for using an ion wind-assisted electrostatic printing nozzle structure for micro / nano structures on an insulating substrate surface includes the following steps:

[0015] 1) Adjust the position of the electrostatic printhead 1 along the Z direction so that the nozzle 102 is in the focusing area of ​​the ion wind, and fix the relative position of the electrostatic printhead 1 and the ion wind generating module 2.

[0016] 2) Turn on the ion wind generating module 2, introduce airflow, and blow out ion wind containing positive and negative ions to form a virtual grounding electrode in the printing area on the surface of the insulating substrate 3.

[0017] 3) Turn on the driving air pressure source 101, and the functional ink 104 is extruded from the nozzle 102. When the extrusion flow rate is stable, set the printing process parameters.

[0018] 4) Turn on the high voltage power supply 103. Apply high voltage to the nozzle 102 to make it a high potential state. A stable electric field is formed between the nozzle and the virtual grounding electrode on the surface of the insulating substrate 3. The functional ink 104 is pulled by the electric field force to form a Taylor cone and is deposited on the insulating substrate 3.

[0019] 5) The electrostatic printing nozzle 1 and the ion wind generating module 2 move along the preset printing trajectory. At the same time, the ion wind generating module 2 continuously blows out ion wind to maintain the virtual grounding state of the target surface of the insulating substrate 3, ensuring stable electrostatic printing on the insulating surface.

[0020] The printing process parameters in step 3) include the applied voltage, platform moving speed, printing receiving distance, driving air pressure, and ion wind speed.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] 1. This invention overcomes the limitation of electrostatic printing on the height of the insulating substrate. It allows for the construction of a virtual grounding electrode on the surface of an insulating substrate of any height using ion wind assistance. This creates a stable electric field between the insulating substrate surface and the nozzle, the intensity of which depends on the voltage applied at the nozzle, eliminating the need for dynamic voltage adjustment based on the substrate height. The virtual grounding electrode can be formed on target surfaces of any shape, significantly improving the stability and printing resolution of electrostatic printing on curved insulating surfaces.

[0023] 2. This invention reduces the voltage requirements for electrostatic printing on insulating substrates, effectively eliminating residual charges. Compared to conventional electrostatic printing, which requires thousands of volts to create a strong electric field and provide sufficient electric attraction, this invention reduces the required voltage to 1 / 4 to 1 / 3 of that required in conventional electrostatic printing, significantly improving safety during the printing process. Simultaneously, the reduced voltage also decreases the residual charges induced or accumulated on the insulating substrate surface, helping to minimize charge repulsion during electrostatic printing.

[0024] 3. The coaxial design of the ion wind generator of the present invention ensures the consistency of the virtual grounding state of the printing area near the nozzle. Especially for electrostatic printing on curved surfaces, it can make the ion wind blow evenly on the insulating curved surface of any shape, while minimizing motion interference during the printing process. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of an electrostatic printing nozzle structure for micro / nano structures on an insulating substrate surface assisted by ion wind, according to the present invention.

[0026] Figure 2 This is a schematic diagram of the ion wind generating module of the present invention.

[0027] Figure 3 This is a comparison of actual wires printed on a planar insulating surface with a height of 50mm using the ion wind-assisted electrostatic printing method of this invention and the conventional electrostatic printing method.

[0028] Figure 4This is a photograph of the actual printing effect of the ion wind-assisted electrostatic printing method of this invention on a planar insulating surface with a height of 100mm.

[0029] Figure 5 This is a physical image showing the conductivity effect of printing wires on the surface of a planar insulating substrate according to an embodiment of the present invention.

[0030] Figure 6 This is a physical image of a spiral wire printed on the surface of a curved insulating substrate according to an embodiment of the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0032] Reference Figure 1 , Figure 2 An electrostatic printing nozzle structure for micro / nano structures on an insulating substrate surface assisted by ion wind includes an electrostatic printing nozzle 1, with an ion wind generating module 2 coaxially connected to the outside of the electrostatic printing nozzle 1 and fixed by the ion wind generating module 2; the upper inlet of the electrostatic printing nozzle 1 is connected to a driving air pressure source 101, and the nozzle 102 at the bottom of the electrostatic printing nozzle 1 is connected to a high-voltage power supply 103; the ion wind generating module 2 has an ionization electrode 201 built in it, which generates positive and negative ions after applying a high voltage, and forms an ion wind driven by the airflow, which is focused on the printing area below the nozzle 102, so that the surface of the insulating substrate 3 is always in a near-zero potential state, forming a virtual grounding electrode.

[0033] The nozzle 102 is a conductive nozzle, which can be made of stainless steel needles, gold-plated glass needles, etc. Its excellent conductivity ensures that all parts of the nozzle 102 are at the same potential. The outer layer of the nozzle 102 is coated with an insulating material, such as rubber or silicone, to prevent the nozzle 102 from adsorbing too many charged ions. When a positive or negative high voltage is applied, the nozzle 102 provides an electric field driving force for electrostatic printing, which pulls the functional ink to form a Taylor cone. The high voltage amplitude can be selected in the range of 0.5-5kV.

[0034] The electrostatic printhead 1 is filled with functional ink 104, which can be conductive functional ink containing metal nanoparticles such as gold, silver, and copper, or sensing functional ink containing nanomaterials such as carbon nanotubes, silver nanowires, and MXene, for printing electronic circuits; in this embodiment, conductive ink containing silver nanoparticles is selected.

[0035] Reference Figure 2 The ion wind generating module 2 is provided with an airflow inlet 202 at the top, an ionization electrode 201 connected inside, and an airflow outlet 203 at the bottom.

[0036] In this embodiment, the ion wind generating module 2 has eight built-in ionization electrodes 201, which are evenly distributed in a ring around the central electrostatic printing nozzle 1. The number and arrangement of the ionization electrodes 201 can be flexibly selected as needed. After applying 15kV AC current, the tips of the ionization electrodes 201 undergo corona discharge, generating air ions with positive and negative charges. There is an airflow inlet 202 between every two ionization electrodes 201. The airflow enters the ion wind generating module 2 to form ion wind. The gas introduced can be air, nitrogen, argon, etc. The position of the ionization electrodes 201 is close to the airflow outlet 203 at the bottom of the ion wind generating module 2, which can reduce the kinetic energy loss and positive and negative ion volume of the ion wind along the flow channel.

[0037] The airflow outlet 203 is inclined inward at an angle of 15°-75°, focusing on the nozzle 102 so that the blown ion air is gathered in the printing area; the airflow outlet 203 is at least 30mm away from the nozzle 102.

[0038] The insulating substrate 3 is a planar substrate or a curved substrate with varying height. The substrate material can be glass, plastic, silicone rubber, paper, fabric, etc. The height of the surface of the insulating substrate 3 from the bottom surface ranges from 1mm to 1m.

[0039] The electrostatic printing nozzle 1 and the ion wind generating module 2 are mounted on a three-axis motion module. Alternatively, a three-axis or higher motion module or a multi-axis robotic arm can be selected according to printing requirements.

[0040] The method for using an ion wind-assisted electrostatic printing nozzle structure for micro / nano structures on an insulating substrate surface includes the following steps:

[0041] 1) Adjust the position of the electrostatic printing nozzle 1 along the Z direction up and down so that its nozzle 102 is in the focusing area of ​​the ion wind, ensuring that the target printing area is within the range reached by the ion wind. Then fix the relative position of the electrostatic printing nozzle 1 and the ion wind generating module 2.

[0042] 2) Turn on the ion wind generating module 2. The ionization electrodes 201 distributed in a ring ionize the air inside the ion wind generating module 2 into air ions with positive and negative charges through corona discharge. When air is introduced, the ion wind containing positive and negative ions is blown out evenly from the air outlet 203. The ion wind can neutralize the surface of the insulating substrate 3 with positive or negative electrostatic charges to a state close to zero potential, thereby forming a virtual grounding electrode in the target printing area.

[0043] In this embodiment, the planar insulating substrate is a plastic cube with a height of 50mm and 100mm. The cube is 3D printed using PLA filament and then immersed in polishing solution to remove surface texture. The curved insulating substrate in this embodiment is a hollow hemisphere model with a diameter of 65mm, corresponding to a curvature of 30.85m. -1 The hemispherical model was manufactured using a photopolymer printer and the material was resin.

[0044] 3) Turn on the driving air pressure source 101. The functional ink 104 filled in the electrostatic printing nozzle 1 is extruded from the nozzle 102 under air pressure. When the extrusion flow rate is stable, set the printing process parameters, including the applied voltage of 1500V, the platform moving speed of 5mm / s, the printing receiving distance of 400μm, the driving air pressure of 1500mbar, and the ion wind speed of 0.2m / s.

[0045] 4) Turn on the high voltage power supply 103. Apply high voltage to the nozzle 102 to make it a high potential state. A stable electric field is formed between the nozzle and the virtual grounding electrode on the surface of the insulating substrate 3. The functional ink 104 is pulled by the electric field force in the electric field to form a Taylor cone and is deposited downward on the insulating substrate 3.

[0046] 5) According to the preset printing path, the electrostatic printing nozzle 1 and the ion wind generating module 2 will move along the set trajectory. In this embodiment, the selected printing trajectory is a planar Peano curve. During the movement, the functional ink 104 is continuously deposited downwards by the electric field force to form a conductive line. At the same time, the ion wind generating module 2 continuously blows out ion wind to eliminate the residual charge generated on the target surface of the insulating substrate 3 and maintain its virtual grounding state, so that the potential difference between the surface of the insulating substrate 3 and the nozzle 102 is kept in dynamic balance, thereby achieving a stable electrostatic printing effect.

[0047] Reference Figure 3 , Figure 3 This is a comparison of the electrostatic printing method of this embodiment and the conventional electrostatic printing method (ionless printing) on ​​a planar insulating substrate with a height of 50mm. It can be seen that, with the assistance of ion wind, the Peano wires printed on the planar insulating substrate are uniform and continuous. This indicates that the electric field constructed between the nozzle 102 and the virtual grounding electrode on the surface of the insulating substrate 3 using the electrostatic printing method of this invention is very stable and can achieve the expected printing effect. In contrast, under the condition of no ion wind assistance and other process parameters being the same, electrostatic printing cannot maintain stability on the planar insulating substrate, and the printed Peano wires show large-area severe breaks or material failure to deposit. Therefore, it can be seen that the electrostatic printing method of this invention can effectively solve the problem of unstable electrostatic printing on insulating surfaces.

[0048] Reference Figure 4, Figure 4 This is a photograph of the printing effect of the ion wind-assisted electrostatic printing method for micro-nano structures in this embodiment on a planar insulating substrate with a height of 100 mm. It can be seen that the electrostatic printing method of this invention can stably print complex Peano wires on a planar insulating substrate with a large height. This shows that the method of this invention can effectively overcome the limitation of substrate height on electrostatic printing and achieve continuous and stable electrostatic printing on a large insulating surface.

[0049] Reference Figure 5 , Figure 5 This is a physical image of the conductivity effect of the printed wire on the surface of the planar insulating substrate in this embodiment. The conductivity of the Peano wire printed on the surface of the planar insulating substrate with a height of 50mm was tested. The wire is continuous and conductive, and the resistance was measured to be 1.05kΩ.

[0050] Reference Figure 6 , Figure 6 This embodiment shows a spiral wire printed on a curved insulating substrate. As can be seen, the electrostatic printing method of the present invention can stably print microscale conformal circuit structures on a hollow hemisphere. From the microscopic image, it can be seen that the spiral lines printed at different heights on the hemisphere can maintain good continuity. Therefore, the electrostatic printing method of the present invention can be effectively extended to the scope of curved insulating surfaces.

[0051] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features therein. These modifications or substitutions do not cause the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

Claims

1. An electrostatic printing nozzle structure for micro / nano structures on an insulating substrate surface assisted by ion wind, characterized in that: It includes an electrostatic printing nozzle (1), the outer side of the electrostatic printing nozzle (1) and the ion wind generating module (2) are coaxially connected; the upper inlet of the electrostatic printing nozzle (1) is connected to the driving air pressure source (101), and the nozzle (102) at the bottom of the electrostatic printing nozzle (1) is connected to the high voltage power supply (103); the ion wind generating module (2) has a built-in ionization electrode (201), which generates positive and negative ions after applying high voltage, and forms an ion wind driven by the airflow, which is focused on the printing area below the nozzle (102), so that the surface of the insulating substrate (3) is always in a near-zero potential state, forming a virtual grounding electrode; The ion wind generating module (2) is provided with an airflow inlet (202) at the top and an airflow outlet (203) at the bottom. It is connected to two or more ionization electrodes (201) inside. The ionization electrodes (201) are evenly distributed in a ring around the central electrostatic printing nozzle (1). The airflow outlet (203) is inclined inward at an angle of 15°-75° and focused on the nozzle (102) so that the blown ion wind is gathered in the printing area. The airflow outlet (203) is at least 30mm away from the nozzle (102). The insulating substrate (3) is a planar substrate or a curved substrate, and the material is glass, plastic, silicone rubber, paper or fabric. The height of the surface of the insulating substrate (3) from the bottom surface ranges from 1mm to 1m. The method for using an ion wind-assisted electrostatic printing nozzle structure for micro / nano structures on an insulating substrate surface includes the following steps: 1) Adjust the position of the electrostatic printing nozzle (1) along the Z direction so that the nozzle (102) is in the focusing area of ​​the ion wind, and fix the relative position of the electrostatic printing nozzle (1) and the ion wind generating module (2); 2) Turn on the ion wind generating module (2), introduce airflow, blow out ion wind containing positive and negative ions, so that a virtual grounding electrode is formed in the printing area on the surface of the insulating substrate (3); 3) Turn on the driving air pressure source (101), and the functional ink (104) is extruded from the nozzle (102). When the extrusion flow rate is stable, set the printing process parameters; 4) Turn on the high voltage power supply (103), apply high voltage to the nozzle (102) and it is in a high potential state. A stable electric field is formed between the nozzle and the virtual grounding electrode on the surface of the insulating substrate (3). The functional ink (104) is pulled by the electric field force to form a Taylor cone and is deposited on the insulating substrate (3). 5) The electrostatic printing nozzle (1) and the ion wind generating module (2) move along the preset printing trajectory. At the same time, the ion wind generating module (2) continuously blows out ion wind to maintain the virtual grounding state of the target surface of the insulating substrate (3) and ensure stable electrostatic printing on the insulating surface.

2. The electrostatic printing nozzle structure for micro / nano structures on an insulating substrate surface assisted by ion wind according to claim 1, characterized in that: The nozzle (102) is a conductive nozzle, and a stainless steel needle or a gold-plated glass needle is selected; the outer layer of the nozzle (102) is coated with an insulating material, and the insulating material is selected as rubber or silicone.

3. The electrostatic printing nozzle structure for micro / nano structures on an insulating substrate surface assisted by ion wind according to claim 1, characterized in that: The electrostatic printing nozzle (1) is filled with functional ink (104), which is a conductive functional ink containing metal nanoparticles of gold, silver and copper, or a sensing functional ink containing nanomaterials of carbon nanotubes, silver nanowires and MXene.

4. The electrostatic printing nozzle structure for ion wind-assisted insulating substrate surface micro / nano structure according to claim 1, characterized in that: The ionizing electrode (201) is subjected to a high voltage in the form of AC or positive and negative DC, with an amplitude range of 1kV-50kV and an AC frequency of 1Hz-1000Hz; there is a gas flow inlet (202) between every two ionizing electrodes (201), and the gas flow is introduced into the ion wind generating module (2) from the gas flow inlet (202) and blown out from the gas flow outlet (203). The introduced gas is air, nitrogen or argon.

5. The electrostatic printing nozzle structure for micro / nano structures on an insulating substrate surface assisted by ion wind according to claim 1, characterized in that: The electrostatic printing nozzle (1) and the ion wind generating module (2) are installed on a motion module with three or more axes or a multi-axis robotic arm.

6. The electrostatic printing nozzle structure for micro / nano structures on an insulating substrate surface assisted by ion wind according to claim 1, characterized in that: The printing process parameters in step 3) include the applied voltage, platform moving speed, printing receiving distance, driving air pressure, and ion wind speed.

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