High resolution spiral electrohydrodynamic jet printing device and method based on sheath liquid focusing

Abstract

This invention discloses a method for fabricating high-resolution helical electrofluid printed lines based on sheath fluid focusing. It constructs an electrofluid jet printing system consisting of a printing nozzle, a micro-injection pump, a power module, a precision motion platform, and a stretchable flexible substrate. Using a functional material solution as the core fluid and a removable material solution as the sheath fluid, the method utilizes the buckling phenomenon caused by the high-speed impact of the jet printed by the electrofluid onto the substrate under the influence of an electric field, thereby generating a stable helical flexible micro / nano structure. Electrofluid printing experiments were conducted, and the influence of jet voltage, internal and external phase flow rates of the nozzle, nozzle-substrate distance, and substrate speed on the morphology of the helical electrofluid jet printed lines was systematically investigated by adjusting the electric field parameters and the relative motion trajectory of the receiving substrate. The parameter ranges of each influencing factor were determined, and multiple sets of experimental samples of helical electrofluid jet printed lines encapsulated by a double-layer solution were obtained. Finally, the outermost sacrificial layer solution of the lines was removed using a solution method, leaving the inner functional helical lines on the flexible substrate. This invention overcomes the limitations of traditional printing nozzle aperture on line accuracy, achieving the fabrication of ultra-high resolution lines at the micro / nano level.

Description

Technical Field

[0001] This invention belongs to the field of advanced manufacturing technology, specifically relating to a high-resolution spiral electrohydrodynamic jet printing method based on sheath fluid focusing. Background Technology

[0002] Electrohydrodynamic jet printing (EHD) is a high-precision printing technology that utilizes an electric field to control the generation and deposition of jets. Traditional inkjet printing uses an extrusion method to force the solution out of the nozzle, while EHD uses a strong electric field between the nozzle and the substrate to drive the solution to be deposited onto the substrate surface along a predetermined trajectory, thus achieving the printing of micro- and nano-structures. This technology effectively overcomes the resolution limitations imposed by nozzle size in inkjet and extrusion printing. Compared to traditional photolithography and screen printing, EHD offers advantages such as maskless operation, digitalization, low processing temperature, and good compatibility with substrates and ink systems. It is particularly suitable for processing conductive lines, electrodes, and functional thin films on flexible and polymer substrates, and has been widely applied in flexible electronic devices, stretchable sensors, micro-energy devices, and bioelectronics.

[0003] In the fabrication of flexible electronic devices, conductive interconnects are typically distributed on the surface of flexible / elastic substrates in the form of straight lines or broken lines. When the device is subjected to deformations such as bending and stretching, straight conductors inevitably bear large axial tensile strains, which easily lead to microcrack propagation and fatigue damage, resulting in a rapid increase in resistance or even failure, and a significant shortening of device lifespan. To alleviate strain concentration, existing technologies propose designing conductors as "spring-like" structures such as helical or serpentine shapes, allowing external macroscopic deformations to be absorbed through the winding, rotation, and unfolding of the helical units, thereby significantly improving the stretchability and cycle stability of the conductive lines. Helical electrojet structures combine micro-nano-scale fiber diameters with three-dimensional spring geometry, achieving a large deformable space within a small footprint, making them one of the effective ways to construct highly flexible conductive interconnects. Existing helical conductors or fibers mostly rely on methods such as ink buckling upon contact with the substrate and self-organizing templates, and their feature dimensions often fail to meet the high-resolution and high-consistency patterning requirements of highly integrated flexible electronic devices.

[0004] Therefore, it is necessary to propose a high-resolution helical electrofluid jet printing method based on sheath fluid focusing. By introducing multi-fluid coordinated control through the printing nozzle, the movement trajectory of the core layer and shell layer can be precisely controlled, and regular and orderly high-resolution helical electrofluid structures can be constructed at the micro-nano scale. This type of structure can not only maintain a stable conductive path under complex conditions such as stretching and bending, significantly improving the fatigue resistance and service life of flexible electronic devices, but also provide a manufacturing method with both high resolution and high reliability for high-density flexible interconnects and wearable sensing systems. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a spiral electrohydraulic jet printing apparatus and method with improved resolution.

[0006] To achieve the above objectives, some embodiments of this application propose a high-resolution spiral electrohydrodynamic jet printing device based on sheath fluid focusing, including an electrohydrodynamic sheath fluid focusing module, a printing control module, a fluid supply module, a power supply module 9, and a sheath fluid removal module;

[0007] The electrohydrodynamic sheath fluid focusing module includes a printhead with a nozzle at its lower part. The nozzle includes an inner nozzle and an outer nozzle arranged coaxially. The printhead has an ink channel and a sheath fluid channel. The inner nozzle communicates with the ink channel, and the outer nozzle communicates with the sheath fluid channel. The inner nozzle communicates with a first input port of the printhead. The first input port is connected to a first micro-injection pump of the liquid supply module via a first micro-channel for supplying functional ink as ink to the nozzle. The outer nozzle communicates with a second input port of the printhead. The second input port is connected to a second micro-injection pump of the liquid supply module via a second micro-channel for supplying sheath fluid as sheath fluid to the nozzle. The power supply module is directly electrically connected to the nozzle.

[0008] The liquid supply module includes a first micro-injection pump, a second micro-injection pump, a first syringe, and a second syringe. The first syringe stores functional material ink, and the first micro-injection pump applies pressure to the first syringe, delivering the functional material ink through a first microchannel to the first input port. The second syringe stores sheath fluid, and the second micro-injection pump applies pressure to the second syringe, delivering the sheath fluid through a second microchannel to the second input port. The sheath fluid then flows out as coaxial ink through the coaxially arranged inner and outer nozzles, wherein the sheath fluid laterally coats the functional material ink.

[0009] The printing control module includes a host computer, a planar motion unit for setting the negative electrode plate of the flexible substrate, and a positioning camera and an observation camera; the negative electrode plate is fixed on the planar motion unit and connected to the ground wire, thereby generating a printing electric field between the nozzle and the metal plate;

[0010] The host computer is connected to the first micro-injection pump, the second micro-injection pump, and the power module, and is configured to control the pressure provided by the first micro-injection pump to adjust the flow rate of the functional material ink, control the pressure provided by the second micro-injection pump to adjust the flow rate of the sheath fluid, and control the printing electric field between the nozzle and the negative electrode plate of the power module so that the coaxial ink forms a Taylor cone and a coaxial ink jet at the end of the nozzle.

[0011] The printing control module includes a host computer, a planar motion unit for setting the negative electrode plate of the flexible substrate, and a positioning camera and an observation camera. The negative electrode plate is fixed on the planar motion unit and connected to the ground wire, thereby generating a printing electric field between the nozzle and the metal plate. The host computer is connected to the positioning camera and the observation camera through wires to provide control feedback. The host computer is also connected to the planar motion unit, so that the planar motion unit receives printing motion parameter data from the host computer and drives the negative electrode plate and the flexible substrate on it to move according to the motion trajectory provided by the printing motion parameter data and at a speed less than the coaxial ink jet deposition speed to form a uniform spiral current fluid core-sheath structure with a core structure formed by functional material ink and a sheath structure formed by sheath fluid covering the outside of the core structure.

[0012] The system includes a sheath fluid removal module, a container for carrying a substrate having the uniform helical electrofluid core-sheath structure, and an application structure for applying a dissolving liquid to the container to dissolve the sheath fluid structure while retaining the core structure, thereby obtaining a functional material ink structure with improved resolution.

[0013] In some embodiments, the sheath fluid removal module further includes a heating unit disposed below the container to heat the flexible substrate 18 to a desired temperature so as to solidify the helical electrofluid core structure in situ after the sheath structure is removed.

[0014] In some embodiments, the container body may provide a drain hole to facilitate the discharge of the solution that has dissolved the sheath structure.

[0015] In some embodiments, the negative electrode plate is a metal plate.

[0016] In some embodiments, the first microchannel and the second microchannel are corrosion-resistant conduits.

[0017] Furthermore, the functional material ink contains piezoelectric materials and organic solvents, including terpineol, ethylene glycol ethers (such as ethylene glycol monobutyl ether), diethylene glycol butyl ether, N-methylpyrrolidone (NMP), and dimethylformamide (DMF); the functional material is a semiconductor polymer material and the solvent is an aromatic hydrocarbon: chlorobenzene, o-dichlorobenzene, xylene, and mesitylene; the functional material is silver sol and the solvent is terpineol; the sacrificial solution is silicone oil.

[0018] Furthermore, the inner diameter of the inner nozzle is 60~200μm, the inner diameter of the outer nozzle is 400~800μm, and the inner nozzle and the outer nozzle are coaxially arranged.

[0019] Furthermore, the syringe has a volume range of 5 mL and a flow rate of 1~5 μL / min.

[0020] Furthermore, the motion speed range of the planar motion module is 0.1~50mm / s, and the power supply module provides 1000~3000V voltage to the print head.

[0021] A high-resolution spiral electrohydrodynamic jet printing device based on sheath fluid focusing: including an electrohydrodynamic sheath fluid focusing module, a printing control module, a fluid supply module, and a power supply module;

[0022] The electrohydrodynamic sheath fluid focusing module includes a printhead with a nozzle at its lower part. The nozzle includes an inner nozzle and an outer nozzle arranged coaxially. The printhead has an ink channel and a sheath fluid channel. The inner nozzle communicates with the ink channel, and the outer nozzle communicates with the sheath fluid channel. The inner nozzle communicates with a first input port of the printhead. The first input port is connected to a first micro-injection pump of the liquid supply module via a first micro-channel for supplying functional ink as ink to the nozzle. The outer nozzle communicates with a second input port of the printhead. The second input port is connected to a second micro-injection pump of the liquid supply module via a second micro-channel for supplying sheath fluid as sheath fluid to the nozzle. The power supply module is directly electrically connected to the nozzle.

[0023] The liquid supply module includes a first micro-injection pump, a second micro-injection pump, a first syringe, and a second syringe. The first syringe stores functional material ink, and the first micro-injection pump applies pressure to the first syringe, delivering the functional material ink through a first microchannel to the first input port. The second syringe stores sheath fluid, and the second micro-injection pump applies pressure to the second syringe, delivering the sheath fluid through a second microchannel to the second input port. The sheath fluid then flows out as coaxial ink through the coaxially arranged inner and outer nozzles, wherein the sheath fluid laterally coats the functional material ink.

[0024] The printing control module includes a host computer, a planar motion unit for setting the negative electrode plate of the flexible substrate, and a positioning camera and an observation camera; the negative electrode plate is fixed on the planar motion unit and connected to the ground wire, thereby generating a printing electric field between the nozzle and the metal plate;

[0025] The host computer is connected to the first micro-injection pump, the second micro-injection pump, and the power module, and is configured to control the pressure provided by the first micro-injection pump to adjust the flow rate of the functional material ink, control the pressure provided by the second micro-injection pump to adjust the flow rate of the sheath fluid, and control the printing electric field between the nozzle and the negative electrode plate of the power module so that the coaxial ink forms a Taylor cone and a coaxial ink jet at the end of the nozzle.

[0026] The printing control module includes a host computer, a planar motion unit for setting the negative electrode plate of the flexible substrate, and a positioning camera and an observation camera. The negative electrode plate is fixed on the planar motion unit and connected to the ground wire, thereby generating a printing electric field between the nozzle and the metal plate. The host computer is connected to the positioning camera and the observation camera through wires to provide control feedback. The host computer is also connected to the planar motion unit, so that the planar motion unit receives printing motion parameter data from the host computer and drives the negative electrode plate and the flexible substrate on it to move according to the motion trajectory provided by the printing motion parameter data and a speed less than the deposition speed of the coaxial ink jet to form a uniform spiral current fluid core-sheath structure with a core structure formed by functional material ink and a sheath structure formed by sheath fluid covering the outside of the core structure.

[0027] A printing method for a high-resolution helical electrohydrodynamic jet printing device based on sheath fluid focusing includes the following steps: S1, providing a high-resolution helical electrohydrodynamic jet printing device based on sheath fluid focusing; S2, starting the first micro-injection pump and the second micro-injection pump to begin filling the print head with the functional material ink and the sheath fluid, thereby ejecting coaxial ink from the nozzle; the power module applies a certain bias voltage, so that the bias voltage works in coordination with the flow rate of the functional material ink and the sheath fluid, so that the coaxial ink forms a stable Taylor cone to form a coaxial ink jet; S3, based on stored experimental data or through multiple experiments, ensuring that the deposition rate of the coaxial ink jet on the flexible substrate is greater than the movement speed of the platform motion unit supporting the flexible substrate, thereby printing a helical uniform core-sheath electrohydrodynamic structure on the substrate; S4, removing the sheath portion of the uniform core-sheath electrohydrodynamic structure using a dissolving method, leaving the core structure on the substrate.

[0028] In some embodiments, step S1 specifically includes: fixing the printhead above the substrate on the motion platform to ensure that the printhead prints within the effective range of the motion axis; the ink inlet of the printhead is connected to the first syringe on the first micro-injection pump through a first microchannel, and the sheath fluid inlet is connected to the second syringe on the second micro-injection pump through a second microchannel; in addition, the lower end of the nozzle is connected to the power module, and the printing resolution can be controlled by adjusting the voltage and the flow rate of ink and sheath fluid; the positioning camera, the observation camera, and the planar motion unit are connected to the host computer, and the movement of the substrate and the image display of the camera are controlled by the motion program; a grounded negative plate is fixed above the planar motion unit, forming a top-down electric field between the plate and the nozzle; a flexible substrate is fixed on the metal plate to receive the printed electrofluid structure.

[0029] In some embodiments, step S2 specifically includes: loading the prepared functional material ink and sheath fluid into a first syringe and a second syringe, respectively; starting the first micro-injection pump to allow the ink to enter the inner nozzle; then starting the second micro-injection pump to deliver the sheath fluid to the outer nozzle; then adjusting the voltage of the power module to make the coaxial ink extruded from the nozzle form a Taylor cone under the action of the electric field force, and flow out of the nozzle in the form of a coaxial ink jet; by coupling the pressure output of the first micro-injection pump and the second micro-injection pump to each other, the functional material ink and the sheath fluid have synchronous flow; by coupling the pressure output of the first micro-injection pump and the second micro-injection pump to each other and the output voltage of the power module to regulate the coaxial ink to form a coaxial ink jet.

[0030] In some embodiments, step S3 specifically includes: after the coaxial ink jet flows out of the nozzle normally, the planar motion unit is started to move at a preset motion speed and trajectory. By adjusting the flow rate of the functional material ink, the flow rate of the sheath fluid, and the voltage, and in conjunction with the nozzle height and the speed of the motion axis, the coaxial ink jet is subjected to pressure and buckling when it comes into contact with the flexible substrate, thereby printing the spiral-shaped uniform core-shell electrohydrodynamic structure.

[0031] In some embodiments, step S3 further includes conducting multiple parametric experiments to investigate the effects of adjustable factors such as voltage, flow rate, nozzle height, and substrate movement speed on the printed electrohydrodynamic structure, obtaining and recording the printing motion parameters for achieving a uniform core-shell electrohydrodynamic structure with a helical shape.

[0032] The beneficial effects of this invention are:

[0033] (1) This invention proposes a high-resolution helical electrohydrodynamic printing device and method based on sheath fluid focusing, which solves the resolution problem limited by the nozzle when electrohydrodynamic jet printing technology is used to prepare tensile-resistant helical wires on flexible substrates. By processing the printed helical core-sheath electrohydrodynamic structure, the sheath structure formed by the sheath fluid is eliminated by solution method, thereby improving the resolution of the printed structure, and further enhancing the electrohydrodynamic jet printing technology in the field of flexible manufacturing.

[0034] (2) This invention combines the manufacturing process of spiral jet to improve the performance of flexible electronics manufacturing. By printing spiral conductive lines, it can better absorb the integrated stress generated by the flexible device when stretched, effectively improve its tensile strength during operation, and meet the functional characteristics required by more flexible applications. Attached Figure Description

[0035] Figure 1 This is a schematic diagram illustrating the structural principle of a high-resolution spiral electrohydrodynamic printing apparatus based on sheath fluid focusing according to an embodiment of this application.

[0036] Figure 2 for Figure 1 A schematic diagram of the printhead structure in the image;

[0037] Figure 3 This is a schematic diagram showing the force situation of the sheath fluid jet during the printing process.

[0038] Figure 4 This is a schematic diagram of the process of eliminating the sheath structure using a solution method;

[0039] Figure 5 Comparison images before and after the removal of the sheath structure. Detailed Implementation

[0040] The specific embodiments of the present invention will be described in detail below with reference to the technical solutions and accompanying drawings.

[0041] This application proposes a high-resolution helical electrohydrodynamic jet printing apparatus and method based on sheath fluid focusing. Two different solutions are used as ink and sheath fluid for printing the structure, respectively. The ink is a functional material ink 21, and the sheath fluid 22, which is subsequently removed, is also called a sacrificial fluid. For example, the functional material in the functional material ink 21 can be a piezoelectric material, and the solvent can be an organic solvent, including terpineol, ethylene glycol ethers (such as ethylene glycol monobutyl ether), diethylene glycol butyl ether, N-methylpyrrolidone (NMP), and dimethylformamide (DMF); the functional material can be a semiconductor polymer material, and the solvent can be an aromatic hydrocarbon: chlorobenzene, o-dichlorobenzene, xylene, and mesitylene; the functional material can also be silver sol, and the solvent can be terpineol; the sheath fluid 22 can be silicone oil.

[0042] This application discloses a high-resolution spiral electrohydrodynamic jet printing device based on sheath fluid focusing. The printhead employs a customized nozzle, comprising an outer nozzle and an inner nozzle coaxially arranged. The inlet of the outer nozzle is connected to a sheath fluid channel providing sheath fluid, while the inlet of the inner nozzle is connected to an ink channel providing functional material ink. The flow rates of the functional material ink and the sheath fluid are controlled synchronously to form coaxial ink. Simultaneously, a bias voltage is applied between the nozzle and the negative electrode plate supporting the flexible substrate below to form a printing electric field. This electric field acts on the two liquids within the printhead, causing them to form a coaxial ink jet where the sheath fluid encapsulates the functional material ink. The sheath fluid jet, through hydrodynamic constraints and modulation by the printing electric field generated by the power module, focuses the functional material ink jet, performing a "compression-confinement-stabilization" process. When the printed coaxial ink jet is deposited on the flexible substrate driven by the planar motion unit 13, it will be subjected to upward pressure from the flexible substrate due to accumulation, which will cause the printed structure to buckle and form a spiral electrofluid structure, or a quasi-spiral or serpentine electrofluid structure. Finally, the sheath structure formed by the sheath fluid is removed by the solution method, leaving the core structure formed by the ink to improve the resolution of the electrofluid structure.

[0043] The inner diameter of the inner nozzle 19 can be 60~200μm, and the inner diameter of the outer nozzle 20 can be 400~800μm.

[0044] The motion speed range of the planar motion unit 13 can be 0.1~50mm / s.

[0045] The power module 9 can provide 1000~3000V voltage to the print head 11.

[0046] Functional material ink and sheath fluid are respectively loaded into two micro-injection pumps. Under mechanical pressure, the functional material ink and sheath fluid simultaneously flow out from the ink channel and sheath fluid channel of the nozzle, respectively. By adjusting the pressure, the two liquids flow out at the nozzle in the form of sheath fluid focusing. At the same time, under the action of the electric field force between the nozzle and the flexible substrate, a Taylor cone and a stable coaxial ink jet are formed. Meanwhile, the flexible substrate is fixed and moves along a preset trajectory after the biaxial motion begins. When the high-speed jet hits the substrate, because the speed of the flexible substrate is less than the deposition speed of the coaxial ink jet, the coaxial ink jet cannot be "straightened" near the contact point. The excess length can only be released by lateral bending or coiling, thereby generating axial compressive stress, buckling, and further torsion, producing a stable spiral coiling phenomenon. At this time, under the combined action of mechanical pressure, gravity, electric field force, etc., the high-speed, fine coaxial ink jet formed after the coaxial ink flows out of the nozzle mainly consists of two parts: a long straight jet part and a very short coiled jet part near the substrate. The former is mainly affected by the electric field tension, while the latter is dominated by bending and torsion. By adjusting the moving speed of the flexible substrate, various spiral-shaped electrofluid structures, also known as lines, are printed on the flexible substrate. After post-processing, the sheath fluid of the printed electrofluid structures is removed using a solution removal method, ultimately leaving only the core structure formed by the functional material ink on the flexible substrate. This printed structure reduces stress in stretchable flexible devices during operation and also improves the resolution of the printed electrofluid structure.

[0047] Example 1:

[0048] like Figure 1 , Figure 2 As shown, some embodiments of this application provide a high-resolution spiral electrohydrodynamic printing device based on sheath fluid focusing, including an electrohydrodynamic sheath fluid focusing module, a printing control module, a fluid supply module, and a power supply module.

[0049] The electrohydrodynamic sheath fluid focusing module mainly includes a printhead 11 with two microchannels, an inner and an outer one. The printhead contains an ink channel 19 and a sheath fluid channel 20. Functional material ink 21, such as piezoelectric material-based functional material ink, flows into the ink channel 19 from the inlet 7. Sheath fluid 22, such as silicone oil, flows into the sheath fluid channel 20 from the inlet 8. The printhead 11 also includes a nozzle 10, which includes an inner nozzle 101 and an outer nozzle 102 coaxially arranged. The inner nozzle 101 is connected to the ink channel 19, and the outer nozzle 102 is connected to the sheath fluid channel 20, thus coaxially providing coaxial ink composed of functional material ink and sheath fluid. The bottom of the nozzle 10 is connected to the power module 9. Under the action of an electric field, the coaxial ink forms a coaxial ink jet in the form of a Taylor cone 17 at the nozzle 10 and is printed out in the form of sheath fluid focusing. The ink inlet 7 is connected to the first syringe 3 on the first micro-injection pump 1 via the first microchannel 5, and the sheath fluid inlet 8 is connected to the second syringe 4 on the second micro-injection pump 2 via the second microchannel 6. The flow rates of the functional material ink and the sheath fluid ink can be synchronized by adjusting the pressure output of the first micro-injection pump 1 and the second micro-injection pump 2.

[0050] The printing control module includes a host computer 16, a planar motion unit 13 with multiple motion axes, and a negative electrode plate, such as a negative electrode plate 12, fixed on the planar motion module 13, with a substrate 18 fixed on the negative electrode plate 12. The printing control program deployed on the host computer 16 can generate structural data for the desired printed electrofluid structure and control the motion speed and trajectory of the planar motion unit based on this structural data, ensuring the accuracy of the printed electrofluid structure. Simultaneously, the substrate 18 is grounded via a metal plate or connected to the negative terminal of the power module 9 to ensure the coordination between the printing electric field and the liquid flow during the printing process.

[0051] The printing control module may also include a positioning camera 15 and an observation camera 14. The planar motion unit 13 is connected to the host computer, and the motion control program deployed on the host computer 16 controls the motion speed and trajectory path of the motion axis of the planar motion unit 13. The positioning camera 15 is connected to the host computer 16 and is used to observe the morphological effect of the electrofluid structure printed on the substrate 18. The observation camera 14 is connected to the host computer 16 and is used to observe the changes of the Taylor cone 17 at the nozzle 10 and the state of the coaxial ink jet falling in the air in real time. The images captured by the positioning camera 15 and the observation camera 14 are configured to be transmitted to the host computer 16 in real time as feedback for the host computer to generate control signals. It is worth noting that the host computer 16 is preferably configured to control the positioning camera 15 to move synchronously with the motion module to observe the electrofluid structure printed on the substrate 18 in real time. The host computer 16 controls the observation camera 14 to move synchronously with the nozzle 10 to observe the morphological changes of the Taylor cone 17 formed by the coaxial ink at the nozzle 10 in static observation.

[0052] The liquid supply module includes a first micro-injection pump 1 and a second micro-injection pump 2. Both pumps can be pressure pumps. The power module 9 is connected to the corresponding part of the print head 11, providing the appropriate flow rate and voltage. The first micro-injection pump 1 and the second micro-injection pump 2 are respectively equipped with a first syringe 3 and a second syringe 4. The first syringe 3 contains the functional material ink (hereinafter referred to as ink), and the second syringe 4 contains the sheath fluid. The first syringe 3 and the second syringe 4 are then connected to the ink inlet 7 and the sheath fluid inlet 8 of the print head 11 via a first microchannel 5 and a second microchannel 6, respectively. Under the propulsion of the first micro-injection pump 1 and the second micro-injection pump 2, the ink and sheath fluid are slowly injected into the print head 11. Adjusting the flow rate ensures coordinated outflow of the ink and sheath fluid, forming coaxial ink with the sheath fluid encapsulating the ink. Simultaneously, under the electric field force of the printing electric field generated by the power module 9, a Taylor cone 17 is formed, thus creating a coaxial ink jet.

[0053] The printhead 11 is fixed above the substrate 18 above the motion module 13, ensuring that the printhead prints within the effective range of the motion axis of the planar motion unit. The ink inlet 7 of the printhead 11 is connected to the syringe 3 on the first micro-injection pump 1 through the first microchannel 5, and the sheath fluid inlet 8 is connected to the syringe 4 on the second micro-injection pump 2 through the second microchannel 6. In addition, the lower end 10 of the nozzle is connected to the power module 9. By adjusting the jet control parameters, including the voltage of the power module 9, the flow rate of the coaxial ink jet and the printing resolution can be controlled. Other positioning cameras 15 and observation cameras 14, as well as the planar motion unit 13, are connected to the host computer 16. The motion control program controls the movement of the substrate and the image display of the cameras. A negative electrode plate 12 is fixedly connected above the planar motion unit 13. The metal plate can be grounded or connected to the negative terminal of the power module 9, thereby forming a top-down electric field between the plate and the nozzle 10 connected to the power module 9. A flexible substrate 18 is fixed on the negative electrode plate 12 to print electrofluid structures, such as electrofluid lines.

[0054] For the same flexible substrate 18 and different functional material inks and sheath solutions, through multiple parametric experiments, the influence of two adjustable factors—the coaxial ink jet velocity and the substrate movement speed—on the morphology of the printed electrohydrodynamic structure was determined. This yielded a set of printing motion parameters for achieving a uniform spiral electrohydrodynamic core-sheath structure with a preset core structure linewidth. Saving this set of printing motion parameters allows for subsequent printing of uniform spiral core-sheath structures. The coaxial ink jet velocity is determined by one or more of the jet control parameters: the pressure of the two micro-injection pumps, the bias voltage, and the distance between the nozzle and the metal plate. Therefore, it is necessary to determine the set of coaxial ink jet control parameters. The substrate movement speed can be determined by the movement speed of the planar motion unit. Therefore, the printing motion parameter set can be determined by experimentally recording the relationship between the data set of the planar motion unit's movement speed and trajectory and the data set of the coaxial ink jet control parameters. The host computer of the printing control module can store the coaxial ink jet control parameter data set and / or the printing motion parameter data set corresponding to different electrofluid structure linewidths for different functional material inks and sheath fluids, which can be retrieved when needed. If the different electrofluid structure linewidths corresponding to the coaxial ink formed by the functional material inks and sheath fluids are not stored, experiments can be conducted first to obtain relevant data and add it to the coaxial ink jet control parameter data set and / or the printing motion parameter data set.

[0055] On one hand, electrohydraulic jet printing experiments can be conducted to obtain different functional material inks and sheath fluid materials to achieve a stable Taylor cone and coaxial ink jet control parameter set. The prepared functional material ink and sheath fluid are loaded into the first syringe 3 and the second syringe 4, respectively. The first micro-injection pump 1 is started to allow the internal liquid to enter the ink channel 19 of the print head 11. Then, the second micro-injection pump 2 is started to deliver the sheath fluid to the sheath fluid channel 20 in the print head 11. Then, the output voltage of the power module 9 is adjusted to adjust the magnitude of the bias voltage between the nozzle 10 and the negative electrode plate 12 to form a printing electric field. The coaxial ink extruded from the nozzle 10 is subjected to the electric field force of the printing electric field and flows out of the nozzle 10 in the form of a Taylor cone, thus forming a coaxial ink jet.

[0056] It is worth noting that after a stable coaxial ink jet is formed, the flow rates of the functional material ink and sheath fluid in the coaxial ink jet can be controlled by adjusting the pressure of the two micro-injection pumps, the bias voltage, and the nozzle height relative to the metal plate. This adjusts the shape of the Taylor cone and thus affects the final shape of the printed structure. For example, excessively high or low flow rates of the functional material ink, sheath fluid, and voltage will all affect the stability of the coaxial ink jet and thus the resolution of the printed spiral lines. Therefore, through multiple experiments, the set of coaxial ink jet control parameters, such as the pressure of the first and second micro-injection pumps, the bias voltage, and the nozzle height relative to the metal plate, can be obtained for different functional material inks and sheath fluids to achieve a stable Taylor cone.

[0057] On the other hand, the set of printing motion parameters for achieving uniform spiral electrohydrodynamic core-sheath structure printing using the high-resolution spiral electrohydrodynamic printing device based on sheath fluid focusing can be obtained through multiple experiments under different functional material ink and sheath fluid conditions. For example, after the coaxial ink jet can flow normally from the nozzle 10, the motion control program is started to control the motion axis of the planar motion unit to move along a preset motion trajectory. By adjusting the coaxial ink jet control parameters, the flow rate of the coaxial ink jet and the motion speed of the motion axis, such as the translation speed, can be adjusted so that the motion speed of the substrate 18 is less than the deposition speed of the coaxial ink jet. The flow rate of the sheath fluid is synchronized with the flow rate of the functional material ink, and also synchronized during deposition; the overall speed should be less than the substrate motion speed. The deposition speed is achieved by controlling the flow rate of the coaxial ink. The flow rate of coaxial ink formed by a certain functional material ink and a certain sheath fluid is determined by the thrust of the first micro-injection pump 1 and the second micro-injection pump 2. The moment when a spiral structure forms is recorded experimentally as the moment when the deposition rate is greater than the substrate movement speed. The magnitudes of the first micro-injection pump 1 and the second micro-injection pump 2 at this moment, along with the corresponding substrate movement speed, are recorded to determine the flow rate. Furthermore, the printing parameters for inks with similar properties are generally similar. This causes the printed lines to bend under pressure when in contact with the substrate 18, thus printing a spiral-shaped electrofluid core-sheath structure, referred to as a uniform spiral electrofluid core-sheath structure or a uniform quasi-spiral core-sheath structure. The ink forms the core structure 23, and the sheath fluid forms the sheath structure 24 outside the core structure. The applicant discovered that when the coaxial ink jet is deposited on the substrate, by adjusting the movement speed 30 of the substrate 18 to be less than the deposition speed 31 of the coaxial ink jet, the coaxial ink jet, upon contact with the substrate 18, is subjected to gravity 26, support force 25, and axial compression, resulting in lateral stresses 27, 28, and 29 at different contact positions with the substrate, i.e., the positions where the coaxial ink jet contacts the substrate. Figure 3 As shown, a spiral deposition trajectory can be gradually formed to deposit a spiral structure on the substrate 18.

[0058] The functional material ink and sheath fluid for printing motion parameters have been collected. The values ​​in the set of printing motion parameters can be directly called to print a uniform spiral electrofluid core-sheath structure.

[0059] The high-resolution spiral electrohydrodynamic jet printing apparatus based on sheath fluid focusing of this application may further include a sheath fluid structure removal module to remove the sheath structure 24 in the uniform spiral core-sheath structure using a dissolving method, so that the linewidth of the core structure 23 formed by the functional material ink left on the substrate is smaller than the width of the uniform spiral electrohydrodynamic core-sheath structure formed by printing, thereby improving the printing resolution.

[0060] For example, the sheath fluid removal module may include a container 33 having a accommodating space provided by the container body to hold a flexible substrate 18 having uniform helical electrofluid core-sheath structures 23 and 24, and a dissolving liquid application device 35, such as a dropper, disposed above the container 33 for dripping a dissolving liquid 34, such as isopropanol, onto the uniform helical electrofluid core-sheath structure to dissolve the sheath structure 24 while retaining the functional material ink structure 23. It may also include a heating unit 32, such as a semiconductor heater, disposed below the container 33 to heat the flexible substrate 18 to a desired temperature, such as 80 degrees Celsius, to facilitate in-situ curing of the helical electrofluid core structure 23 after the sheath structure 24 is removed. In some embodiments, the container body 33 may provide a drain hole 36 to facilitate the drainage of the dissolving liquid 35 that has dissolved the sheath structure.

[0061] Based on the parameter values ​​obtained from step S3 for printing the uniform helical core-sheath structure proposed in this application, various helical or quasi-helical helical core-sheath structures can be printed on the substrate 18 by adjusting the movement speed of different substrates. Then, the sheath structure 24 is removed and cleaned using a solution that is compatible with the external liquid, resulting in a helical electrofluid core structure 23 made only of functional material ink, which greatly improves the resolution limited by the printhead in traditional printing.

[0062] Example 2:

[0063] A printing method using a high-resolution helical electrohydrodynamic jet printing device based on sheath fluid focusing comprises the following steps:

[0064] S1. Provides a high-resolution spiral electrohydrodynamic printing device based on sheath fluid focusing;

[0065] S2. Start the first micro-injection pump and the second micro-injection pump to start filling the print head with ink and sheath fluid. At the same time, the power module applies a certain bias voltage so that the bias voltage and the ink flow work in coordination to make the coaxial ink form a stable Taylor cone.

[0066] S3. Through multiple experiments, a uniform core-sheath spiral jet was printed to form a spiral electrohydrodynamic jet structure.

[0067] S4. The sheath portion of the spiral electrohydrodynamic structure is removed using a dissolving method, so that the linewidth of the inner layer solution remaining on the substrate is smaller than the width of the printed lines, thereby improving the printing resolution.

[0068] Furthermore, step S1 specifically includes:

[0069] The printhead 11 is fixed above the substrate 18 on the motion platform to ensure that the printhead prints within the effective range of the motion axis. The ink inlet 7 of the printhead is connected to the first syringe 3 on the first micro-injection pump 1 through the first microchannel 5. Similarly, the sheath fluid inlet 8 is connected to the second syringe 4 on the second micro-injection pump 2 through the second microchannel 6. In addition, the lower end of the nozzle 10 is connected to the power module 9. The printing resolution can be controlled by adjusting the voltage and the flow rate of ink and sheath fluid. The positioning camera 15, the observation camera 14, and the planar motion unit 13 are connected to the host computer 16. The movement of the substrate and the image display of the camera are controlled by the motion program. A grounded negative electrode plate 12 is fixed above the planar motion unit, forming a top-down electric field between it and the nozzle. A flexible substrate 18 is fixed on the metal plate to receive the printed electrofluid structure.

[0070] Furthermore, step S2 specifically includes:

[0071] The prepared ink and sheath fluid are loaded into the first syringe 3 and the second syringe 4, respectively. The first micro-injection pump 1 is activated, allowing the ink to enter the inner nozzle. Then, the second micro-injection pump 2 is activated to deliver the sheath fluid to the outer nozzle. The voltage of the power module 9 is then adjusted so that the coaxial ink extruded from the nozzle is subjected to an electric field, forming a Taylor cone and flowing out of the nozzle as a jet. It is worth noting that the pressure outputs of the first and second micro-injection pumps are coupled to ensure that the functional material ink and the sheath fluid flow synchronously, i.e., have the same flow rate. The coaxial ink jet is regulated by the pressure outputs of the first and second micro-injection pumps and the output voltage of the power module 9. Excessive or insufficient ink flow rate and voltage will affect the stability of the coaxial ink jet and the resolution of the printed lines.

[0072] Furthermore, step S3 specifically includes:

[0073] After the coaxial ink jet can flow out of the nozzle normally, the planar motion unit is started to move according to the preset motion speed and trajectory. By adjusting the flow rate of the functional material ink, the flow rate of the sheath liquid and the voltage, and in combination with the nozzle height and the speed of the motion axis, the printed lines are pressed and buckled when they come into contact with the substrate 18, thereby printing a spiral-shaped electrohydrodynamic structure, or a quasi-spiral-shaped electrohydrodynamic structure.

[0074] Preferably, step S3 further includes conducting multiple parametric experiments to investigate the effects of adjustable factors such as voltage, flow rate, nozzle height, and substrate movement speed on the printed electrofluid structure, obtaining and recording the printing motion parameters that can achieve a uniform spiral morphology core-shell electrofluid structure.

[0075] Preferably, step S3 further includes:

[0076] Using the jet parameters for printing a uniform spiral core-shell electrohydrodynamic structure obtained in step S3, various spiral core-shell structures are printed on substrate 18 by adjusting different substrate speeds.

[0077] In step S4, the sheath fluid structure 24 is removed and cleaned using a solution that is compatible with the sheath fluid, resulting in a uniform spiral current core structure 23 formed only by functional material ink, which greatly improves the resolution limited by the printhead in traditional printing.

[0078] This invention enables the fabrication of high-resolution spiral electrohydrodynamic jet printing using sheath fluid focusing, solving the problem of reduced lifespan of fabricated flexible devices due to prolonged tensile stress, while also improving the resolution limited by nozzle size in traditional printing.

[0079] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A high-resolution helical electrohydrodynamic printing device based on sheath fluid focusing, characterized in that, It includes an electrohydrodynamic sheath fluid focusing module, a printing control module, a fluid supply module, a power supply module, and a sheath fluid removal module; The electrohydrodynamic sheath fluid focusing module includes a printhead, the lower part of which has a nozzle (10). The nozzle includes an inner nozzle and an outer nozzle arranged coaxially. The printhead has an ink channel and a sheath fluid channel. The inner nozzle is connected to the ink channel, and the outer nozzle is connected to the sheath fluid channel. The inner nozzle is connected to the first input port (7) of the printhead. The first input port (7) is connected to the first micro-injection pump (1) of the liquid supply module through a first micro-channel (5) for supplying functional ink as ink to the nozzle. The outer nozzle is connected to the second input port (8) of the printhead. The second input port (8) is connected to the second micro-injection pump (2) of the liquid supply module through a second micro-channel (6) for supplying sheath fluid as sheath fluid to the nozzle. The power module (9) is directly electrically connected to the nozzle (10). The liquid supply module includes a first micro-injection pump (1), a second micro-injection pump (2), a first syringe (3), and a second syringe (4). The first syringe stores functional material ink. The first micro-injection pump (1) applies pressure to the first syringe (3), and the functional material ink is delivered to the first input port (7) through the first microchannel (5). The second syringe stores sheath fluid. The second micro-injection pump (2) applies pressure to the second syringe (4), and the sheath fluid is delivered to the second input port (8) through the second microchannel (6). The fluid flows out in the form of coaxial ink through the coaxially arranged inner and outer nozzles, wherein the sheath fluid laterally covers the functional material ink. The printing control module includes a host computer (16), a planar motion unit (13), a negative electrode plate (12) for setting the flexible substrate (18), a positioning camera (15), and an observation camera (14); the negative electrode plate is fixed on the planar motion unit and connected to the ground wire, thereby generating a printing electric field between the nozzle and the metal plate; The host computer is connected to the first micro-injection pump (1), the second micro-injection pump (2) and the power module, and is configured to control the pressure provided by the first micro-injection pump (1) to adjust the flow rate of the functional material ink, control the pressure provided by the second micro-injection pump (2) to adjust the flow rate of the sheath fluid, and control the printing electric field between the nozzle and the negative electrode plate of the power module so that the coaxial ink forms a Taylor cone (17) and a coaxial ink jet at the end of the nozzle; The printing control module includes a host computer (16), a planar motion unit (13), a negative electrode plate (12) for setting the flexible substrate (18), a positioning camera (15), and an observation camera (14); the negative electrode plate is fixed on the planar motion unit and connected to the ground wire, thereby generating a printing electric field between the nozzle and the metal plate; the host computer (16) is connected to the positioning camera (15) and the observation camera (14) respectively through wires to provide control feedback, and the host computer (16) is also connected to the planar motion unit (13), so that the planar motion unit (13) receives printing motion parameter data from the host computer and drives the negative electrode plate (12) and the flexible substrate (18) on it to move according to the motion trajectory provided by the printing motion parameter data and a speed less than the coaxial ink jet deposition speed to form a uniform spiral current fluid core-sheath structure with a core structure formed by functional material ink and a sheath structure formed by sheath liquid covering the outside of the core structure; And a sheath fluid removal module, configured to carry a container of a substrate (18) having the uniform helical electrofluid core sheath structure, and an application structure (35) for applying a dissolving liquid (34) to the container to dissolve the sheath fluid structure (24) while retaining the core structure, thereby obtaining a functional material ink structure (23) with improved resolution.

2. A high-resolution helical electrohydrodynamic printing apparatus based on sheath fluid focusing according to claim 1, characterized in that, The sheath fluid removal module also includes a heating unit (32) disposed below the container (33) to heat the flexible substrate (18) to the desired temperature so as to solidify the spiral electrofluid core structure (23) in situ after the sheath structure (24) is removed; the container body (32) provides a drain hole to drain the solution (35) that has dissolved the sheath structure.

3. A high-resolution helical electrohydrodynamic printing apparatus based on sheath fluid focusing according to claim 1, characterized in that, The negative electrode plate (12) is a metal plate; the first microchannel (5) and the second microchannel (6) are corrosion-resistant conduits; the functional material ink (21) contains piezoelectric materials and organic solvents, including terpineol, ethylene glycol ethers (such as ethylene glycol monobutyl ether), diethylene glycol butyl ether, N-methylpyrrolidone (NMP), and dimethylformamide (DMF); the functional material is a semiconductor polymer material and the solvent is aromatic hydrocarbons: chlorobenzene, o-dichlorobenzene, xylene, and mesitylene; the functional material is silver sol and the solvent is terpineol; the sheath fluid (22) is silicone oil.

4. A high-resolution helical electrohydrodynamic printing apparatus based on sheath fluid focusing according to claim 1, characterized in that, The inner diameter of the inner nozzle (19) is 60~200μm, and the inner diameter of the outer nozzle (20) is 400~800μm. The inner nozzle (19) and the outer nozzle (20) are coaxially arranged. The motion speed range of the planar motion module (13) is 0.1~50mm / s, and the power module (9) provides 1000~3000V voltage to the print head (11).

5. A high-resolution spiral electrohydrodynamic jet printing device based on sheath fluid focusing: comprising an electrohydrodynamic sheath fluid focusing module, a printing control module, a liquid supply module and a power supply module (9); The electrohydrodynamic sheath fluid focusing module includes a printhead, the lower part of which has a nozzle (10). The nozzle includes an inner nozzle and an outer nozzle arranged coaxially. The printhead has an ink channel and a sheath fluid channel. The inner nozzle is connected to the ink channel, and the outer nozzle is connected to the sheath fluid channel. The inner nozzle is connected to the first input port (7) of the printhead. The first input port (7) is connected to the first micro-injection pump (1) of the liquid supply module through a first micro-channel (5) for supplying functional ink as ink to the nozzle. The outer nozzle is connected to the second input port (8) of the printhead. The second input port (8) is connected to the second micro-injection pump (2) of the liquid supply module through a second micro-channel (6) for supplying sheath fluid as sheath fluid to the nozzle. The power module (9) is directly electrically connected to the nozzle (10). The liquid supply module includes a first micro-injection pump (1), a second micro-injection pump (2), a first syringe (3), and a second syringe (4). The first syringe stores functional material ink, and the first micro-injection pump (1) applies pressure to the first syringe (3), delivering the functional material ink to the first input port (7) through a first microchannel (5). The second syringe stores sheath fluid, and the second micro-injection pump (2) applies pressure to the second syringe (4), delivering the sheath fluid to the second input port (8) through a second microchannel (6), and flowing out as coaxial ink through the coaxially arranged inner and outer nozzles. The sheath fluid laterally coats the functional material ink; The printing control module includes a host computer (16), a planar motion unit (13), a negative electrode plate (12) for setting the flexible substrate (18), a positioning camera (15), and an observation camera (14); the negative electrode plate is fixed on the planar motion unit and connected to the ground wire, thereby generating a printing electric field between the nozzle and the metal plate; The host computer is connected to the first micro-injection pump (1), the second micro-injection pump (2) and the power module, and is configured to control the pressure provided by the first micro-injection pump (1) to adjust the flow rate of the functional material ink, control the pressure provided by the second micro-injection pump (2) to adjust the flow rate of the sheath fluid, and control the printing electric field between the nozzle and the negative electrode plate of the power module so that the coaxial ink forms a Taylor cone (17) and a coaxial ink jet at the end of the nozzle; The printing control module includes a host computer (16), a planar motion unit (13), a negative electrode plate (12) for setting the flexible substrate (18), a positioning camera (15), and an observation camera (14); the negative electrode plate is fixed on the planar motion unit and connected to the ground wire, thereby generating a printing electric field between the nozzle and the metal plate; the host computer (16) is connected to the positioning camera (15) and the observation camera (14) respectively through wires to provide control feedback, and the host computer (16) is also connected to the planar motion unit (13), so that the planar motion unit (13) receives printing motion parameter data from the host computer and drives the negative electrode plate (12) and the flexible substrate (18) on it to move according to the motion trajectory provided by the printing motion parameter data and a speed less than the deposition speed of the coaxial ink jet to form a uniform spiral current fluid core-sheath structure with a core structure formed by functional material ink and a sheath structure formed by sheath fluid covering the outside of the core structure.

6. A printing method using the high-resolution helical electrohydrodynamic printing apparatus based on sheath fluid focusing according to any one of claims 1 to 4, characterized in that: Including the following steps: S1. Provides a high-resolution spiral electrohydrodynamic printing device based on sheath fluid focusing; S2. Start the first micro-injection pump and the second micro-injection pump to start filling the print head with the functional material ink and the sheath fluid, so that the nozzle ejects to form coaxial ink. The power module applies a certain bias voltage so that the bias voltage works in coordination with the flow rate of the functional material ink and the sheath fluid so that the coaxial ink forms a stable Taylor cone to form a coaxial ink jet. S3. Based on stored experimental data or through multiple experiments, the deposition rate of the coaxial ink jet on the flexible substrate is made greater than the movement speed of the platform motion unit supporting the flexible substrate, thereby printing a uniform core sheath current fluid structure in a spiral shape on the substrate. S4. Remove the sheath portion of the uniform nuclear sheath electrohydrodynamic structure using a dissolving solution method, leaving the nuclear structure on the substrate.

7. The printing method of the high-resolution helical electrohydrodynamic printing device based on sheath fluid focusing according to claim 6: characterized in that: Step S1 specifically includes: fixing the print head (11) above the substrate (18) on the motion platform to ensure that the print head prints within the effective range of the motion axis; the ink inlet (7) of the print head is connected to the first syringe (3) on the first micro-injection pump (1) through the first micro-channel (5), and the sheath fluid inlet (8) is connected to the second syringe (4) on the second micro-injection pump (2) through the second micro-channel (6); in addition, the lower end of the nozzle (10) is connected to the power module (9), and the printing resolution can be controlled by adjusting the voltage and the flow rate of ink and sheath fluid; the positioning camera (15), the observation camera (14), and the planar motion unit (13) are connected to the host computer (16), and the movement of the substrate and the image display of the camera are controlled by the motion program; a grounded negative plate (12) is fixed above the planar motion unit, forming an electric field from top to bottom between it and the nozzle; a flexible substrate (18) is fixed on the metal plate to receive the printed electrofluid structure.

8. The printing method of the high-resolution helical electrohydrodynamic printing device based on sheath fluid focusing according to claim 6: characterized in that: Step S2 specifically includes: loading the prepared functional material ink and sheath fluid into the first syringe (3) and the second syringe (4) respectively; starting the first micro-injection pump (1) to allow the ink to enter the inner nozzle; then starting the second micro-injection pump (2) to deliver the sheath fluid to the outer nozzle; then adjusting the voltage of the power module (9) to make the coaxial ink squeezed out at the nozzle form a Taylor cone under the action of the electric field force, and flow out from the nozzle in the form of a coaxial ink jet; by coupling the pressure output of the first micro-injection pump and the second micro-injection pump to make the functional material ink and the sheath fluid flow synchronously; by coupling the pressure output of the first micro-injection pump and the second micro-injection pump and the output voltage of the power module (9) to regulate the coaxial ink to form a coaxial ink jet.

9. The printing method of the high-resolution helical electrohydrodynamic printing device based on sheath fluid focusing according to claim 6: characterized in that: Step S3 specifically includes: after the coaxial ink jet flows out of the nozzle normally, the planar motion unit is started to move according to the preset motion speed and motion trajectory. By adjusting the flow rate of the functional material ink, the flow rate of the sheath liquid and the voltage, and in combination with the nozzle height and the speed of the motion axis, the coaxial ink jet is subjected to pressure and buckling phenomenon when it comes into contact with the flexible substrate (18), thereby printing the spiral-shaped uniform core-shell electrohydrodynamic structure.

10. The printing method of the high-resolution helical electrohydrodynamic printing device based on sheath fluid focusing according to claim 6: characterized in that: Step S3 further includes conducting multiple parametric experiments to investigate the effects of adjustable factors such as voltage, flow rate, nozzle height, and substrate movement speed on the printed electrohydrodynamic structure, obtaining and recording the printing motion parameters for a uniform core-shell electrohydrodynamic structure with a spiral morphology.

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