An independent injection control method and injection device for an arrayed electrohydrodynamic nozzle

Abstract

The present invention discloses an independent injection control method and injection device for an arrayed electrohydrodynamic nozzle, belonging to the technical field of inkjet printing. The injection device includes an electrohydrodynamic nozzle, a high-voltage power supply, a laser module, and a control module. The electrohydrodynamic nozzle is composed of an ink cartridge, a nozzle plate, and a nozzle. The high-voltage power supply is used to provide high voltage electricity to form an electric field driving force to eject the solution. The laser module generates laser for regulating the temperature of the liquid meniscus of the solution. The control module controls the opening and closing of the high-voltage power supply and the laser. The present invention regulates the temperature of the liquid meniscus at the tip of the nozzle by using a laser-induced method, changes the surface tension coefficient of the solution at the tip of the liquid meniscus through the change of temperature, realizes the adjustment between the electric field force and the surface tension, and further controls the independent injection of each nozzle. In this way, the present invention can realize the independent injection of each nozzle without changing the nozzle structure, and has the advantages of simple nozzle structure and convenient maintenance.

Description

Technical Field

[0001] The present invention belongs to the technical field of inkjet printing, and more specifically, relates to an independent injection control method and injection device for an arrayed electrohydrodynamic printhead. Background Art

[0002] As a maskless and additive manufacturing technology, inkjet printing has the characteristics of high material utilization rate and low cost, and has good application prospects in many industrial manufacturing fields, such as printed display, flexible electronics, etc. At present, traditional printing technologies such as piezoelectric / thermal bubble mainly represented by piezoelectric printing and thermal bubble printing use extrusion force as the driving force, and extrude liquid droplets from the nozzle holes through the vibration of piezoelectric ceramics or the expansion of thermal bubbles. Using extrusion force as the driving force makes the printing very sensitive to the ink viscosity, and the extruded ink droplets are generally larger than the diameter of the nozzle hole, having deficiencies such as low printing resolution (>20μm) and narrow ink viscosity range (1-20cP), and it is difficult to meet the printing requirements of various materials and higher resolution. Electrohydrodynamic printing applies a high voltage between the nozzle and the substrate, and uses the electric field force to overcome the surface tension to "pull" the ink out of the nozzle to generate fine droplets. Electrohydrodynamic printing has ultra-high resolution, wide ink (1-10000cP) compatibility and multiple injection modes, and has broad application prospects.

[0003] The arrayed electrohydrodynamic printhead is the key to realizing the industrialization of electrohydrodynamic inkjet printing. At present, the independent controllable injection of the arrayed electrohydrodynamic printhead is realized through an externally connected electrode ring. However, due to the asymmetry of the nozzle, the electric field between multiple nozzles and the substrate will be distorted, and the jet is easily deflected onto the externally connected electrode ring, causing nozzle failure. In addition, because the radius of the electrode should be larger than the nozzle diameter, the extraction ring greatly limits the integration of the printhead, and at the same time brings difficulties to the assembly, cleaning and maintenance of the printhead.

[0004] Patent CN201410289239.5 proposed a method for realizing independent controllable printing of the printhead, but an extraction electrode needs to be added in front of the nozzle hole, and the ink liquid is easily deflected onto the extraction electrode, causing damage to the printhead, and the structure is complex and difficult to manufacture. Patent CN201510299992.7 proposed a micro electrospray chip device and manufacturing method, but its spray chip cannot independently regulate the printing state of each nozzle hole. Patent CN202111078207.7 proposed an electrohydrodynamic printhead with independent controllable printing, but it also increases the complexity of the nozzle structure. Summary of the Invention

[0005] In view of the deficiencies of the prior art and the improvement requirements, the present invention provides an independent injection control method and injection device for an arrayed electrohydrodynamic nozzle. By using a laser-induced method to regulate the temperature of the meniscus at the tip of the nozzle, the surface tension coefficient of the solution at the tip of the meniscus is changed through the temperature change, so as to realize the adjustment between the electric field force and the surface tension, and further control the independent injection of each nozzle.

[0006] To achieve the above object, in a first aspect, the present invention provides an independent injection control method for an arrayed electrohydrodynamic nozzle, including:

[0007] Apply the same working voltage to all nozzles, so that the electric field force received by the meniscus at the tip of the nozzle is less than the surface tension. At this time, all nozzles do not inject;

[0008] Irradiate the meniscus at the tip of the ignition nozzle with a laser to raise its temperature to a point where its surface tension is less than the electric field force, thereby causing injection.

[0009] Further, the working voltage is less than the nozzle opening voltage, and the temperature range regulated by the laser is lower than the boiling point of the solution.

[0010] To achieve the above object, in a second aspect, the present invention provides another independent injection control method for an arrayed electrohydrodynamic nozzle, including:

[0011] Apply the same working voltage to all nozzles, so that the electric field force received by the meniscus at the tip of the nozzle is greater than the surface tension. At this time, all nozzles inject;

[0012] Irradiate the meniscus at the tip of the non-ignition nozzle with a laser to lower its temperature to a point where its surface tension is greater than the electric field force, thereby preventing injection.

[0013] Further, the working voltage is 1 to 1.2 times the nozzle opening voltage, and the temperature range regulated by the laser is higher than the melting point of the solution.

[0014] To achieve the above object, in a third aspect, the present invention provides an arrayed electrohydrodynamic printing device for implementing the method described in the first aspect or the second aspect, including an arrayed electrohydrodynamic nozzle, a high-voltage power supply, a laser module, and a control module;

[0015] The arrayed electrohydrodynamic nozzle includes an ink cartridge, a nozzle plate, and a plurality of nozzles;

[0016] The high-voltage power supply is used to generate a working voltage;

[0017] The laser module is used to generate multiple laser beams corresponding to each nozzle one by one to change the temperature of the meniscus at the tip of each nozzle;

[0018] The control module is used to control the high-voltage power supply and the laser module to regulate the voltage signal output by the high-voltage power supply and independently control the on / off of each laser beam.

[0019] Further, the laser module is composed of a laser plus a laser beam splitter, or composed of multiple lasers.

[0020] Further, the multiple laser beams generated by the laser module are arranged according to design requirements, and the number thereof matches the number of nozzles.

[0021] Further, the laser module adjusts the power of the laser or the pulse duration of the laser through the control module to control the temperature of the liquid meniscus at the tip of the nozzle, and further control the independent ejection of the nozzle.

[0022] Further, the orifice plate is made of an adiabatic material or has an adiabatic material interlayer.

[0023] Further, the nozzle is prepared from a heat-conducting material.

[0024] Generally speaking, through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0025] Compared with the prior art, the independent ejection of each nozzle is achieved by changing the electric field force; the present invention innovatively proposes to achieve the independent ejection of each nozzle by changing the surface tension, specifically: by using a laser-induced method to regulate the temperature of the liquid meniscus at the tip of the nozzle, changing the surface tension coefficient of the solution at the tip of the liquid meniscus through the change of temperature, realizing the adjustment between the electric field force and the surface tension, and further controlling the independent ejection of each nozzle. In this way, the present invention can achieve the independent ejection of each nozzle without changing the nozzle structure, and has the advantages of simple nozzle structure and easy maintenance. Description of the Drawings

[0026] Figure 1 It is a schematic diagram of the principle of independent ejection control of an arrayed electrohydrodynamic nozzle provided by an embodiment of the present invention;

[0027] Figure 2 It is a schematic diagram of the structure of an electrohydrodynamic nozzle provided by an embodiment of the present invention;

[0028] Figure 3 It is a control block diagram of an arrayed electrohydrodynamic printing device provided by an embodiment of the present invention. Detailed Embodiments

[0029] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] In the present invention, terms such as "first" and "second" in the present invention and the accompanying drawings (if any) are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence.

[0031] In the present invention, the ignition nozzle refers to the nozzle that needs to spray, and the non-ignition nozzle refers to the nozzle that does not need to spray.

[0032] The present invention provides an independent injection control method for an arrayed electrohydrodynamic nozzle, including:

[0033] Method 1: Apply the same working voltage to all nozzles so that the electric field force on the meniscus at the tip of the nozzle is less than the surface tension. At this time, all nozzles do not spray; irradiate the meniscus at the tip of the ignition nozzle with a laser to raise its temperature to a level where its surface tension is less than the electric field force, thereby causing spraying.

[0034] Method 2: Apply the same working voltage to all nozzles so that the electric field force on the meniscus at the tip of the nozzle is greater than the surface tension. At this time, all nozzles spray; irradiate the meniscus at the tip of the non-ignition nozzle with a laser to lower its temperature to a level where its surface tension is greater than the electric field force, thereby preventing spraying.

[0035] Taking Method 1 as an example, when not spraying, the solution temperature is T0, the surface tension coefficient is γ0, and for a nozzle with a diameter of d N , the surface tension on the meniscus at the tip is F γ0 = 4γ0 / d N . At this time, apply the working voltage U0 to all nozzles, and the electric field force on the meniscus at the tip of the nozzle where E0 = 4U0 / (d N ln8H / d N ), ε0 is the vacuum permittivity, and H is the distance from the nozzle to the substrate. At this time, F γ0 > F E , and all nozzles do not spray. By irradiating the meniscus at the tip of the ignition nozzle with a laser to raise its temperature to T1, the surface tension of the meniscus at the tip of the ignition nozzle is reduced to F γ1 , F γ1 < F E , and the ignition nozzle sprays. At this time, the surface tension of the meniscus at the tip of the non-ignition nozzle remains F γ0 unchanged and does not spray.

[0036] Furthermore, the working voltage applied to all nozzles should be less than the nozzle opening voltage, and the temperature range regulated by the laser is lower than the boiling point of the solution.

[0037] Taking Method 2 as an example, at this time, the working voltage is 1 to 1.2 times the nozzle opening voltage, and all the spray holes eject. By irradiating the liquid meniscus at the tip of the non-ignition nozzle with a laser, the surface tension thereof is increased. At this time, the surface tension of the liquid meniscus at the tip of the non-ignition nozzle is greater than the electric field force, and no ejection occurs, while the other ignition nozzles continue to eject. Among them, the temperature range regulated by the laser is higher than the melting point of the solution.

[0038] The present invention also provides an array electrohydrodynamic printing device for implementing the method as described in the first embodiment, as Figure 1 shown, which includes an array electrohydrodynamic print head, a high-voltage power supply, a laser module, and a control module.

[0039] 1) The array electrohydrodynamic print head includes an ink cartridge, a nozzle plate, and a plurality of nozzles.

[0040] Specifically, as Figure 2 shown, the ink cartridge includes an ink inlet, an ink outlet, and mounting holes; the ink inlet and the ink outlet are provided at the upper end of the ink cartridge, the ink inlet is used for filling the ink, and the ink outlet is used for discharging the excess ink and air bubbles; the mounting holes are provided on both sides of the ink cartridge for installing and fixing the position of the print head.

[0041] The nozzle plate is arranged at the bottom of the ink cartridge and is a flat plate with holes.

[0042] As a further preference, the nozzle plate can be processed by processes such as laser ablation, photolithography, sandblasting, etc. on an adiabatic flat plate (or a flat plate with an adiabatic material sandwich layer). The nozzle plate prepared from the adiabatic material is beneficial to preventing heat transfer between different nozzles, avoiding thermal crosstalk, and improving the independent control effect. The through holes are used to guide the solution into the nozzles.

[0043] The nozzles are arranged at the bottom of the nozzle plate and are of a hollow boss structure, and correspond to the through holes of the nozzle plate one by one. The solution flows from the ink cartridge through the through holes of the nozzle plate, enters the nozzles, and finally ejects from the tips of the nozzles.

[0044] As a further preference, the nozzles are prepared from a heat-conducting material, which is beneficial to the diffusion of heat from the solution to the air, enabling the nozzles to quickly return to room temperature after ejection and achieving a fast response.

[0045] 2) The high-voltage power supply is used to generate a working voltage.

[0046] Specifically, the high-voltage power supply is a device for generating high-voltage signals, which can convert the input low-voltage signals into high-voltage signals and access the solution through leads to generate an electric field to drive the solution to eject. Its parameters can be adjusted manually or controlled by the low-voltage signals generated by the control module.

[0047] 3) The laser module is used to generate multiple laser beams corresponding to each nozzle one by one, so as to change the temperature of the liquid meniscus at the tip of each nozzle.

[0048] Specifically, the laser module is a device for generating laser. The generated laser irradiates the liquid meniscus of the solution, and the temperature of the solution can be adjusted. Its output power can be adjusted manually or through the control module.

[0049] The laser module can be composed of a laser plus a laser beam splitter, or composed of multiple lasers. And the multiple laser beams generated by the laser module are arranged according to the design requirements, and the number thereof matches the number of nozzles. Further, the laser module adjusts the power of the laser or the pulse duration of the laser through the control module to control the temperature of the liquid meniscus at the tip of the nozzle, and further control the independent ejection of the nozzle.

[0050] It should be noted that a heating laser or a cooling laser can be used to irradiate the liquid meniscus at the tip of the nozzle to increase or decrease the temperature of the liquid meniscus at the tip of the nozzle.

[0051] 4) The control module is used to control the high-voltage power supply and the laser module to regulate the voltage signal output by the high-voltage power supply and independently control the on / off of each laser beam.

[0052] Specifically, as Figure 3 shown, the control module consists of a host computer and a digital main controller.

[0053] The host computer is a human-computer interaction interface, which can mainly convert the pattern to be printed into print data and send it to the digital main controller, and can regulate the output parameters of the high-voltage power supply and the laser through software.

[0054] The digital main control module is a single-chip microcomputer, and can also be other forms of microcontrollers such as PLD or FPGA. It is mainly responsible for receiving, processing, caching, outputting and timing logic control of print data. After receiving the required print data, the digital main controller converts it into the logic control signals required for the high-voltage power supply and the switching actions of each laser beam, and then outputs it serially or in parallel to the high-voltage power supply and the laser module according to the given timing.

[0055] To better illustrate the present invention, the following examples are given:

[0056] In this example, the ink cartridge is processed and prepared using insulating materials such as plexiglass. The ink inlet of the ink cartridge is used to fill the ink, and the ink outlet is used to discharge the excess ink and air bubbles. The ink cartridge installation and positioning holes are used to install and fix the position of the nozzle.

[0057] The orifice plate uses an adiabatic glass material as the substrate, with a length of about 10 mm, a width of 10 mm, and a thickness of 1 mm. Subsequently, 3 circular through-holes with a diameter of 260 μm and a spacing of 1 mm are ablated on the glass using a laser.

[0058] The orifices use 34G stainless steel needles, with an inner diameter of 60 μm and an outer diameter of 230 μm. They are inserted into the through-holes of the orifice plate and bonded using UV curable glue.

[0059] Finally, a Teflon hydrophobic layer can be deposited on the surface of the protruding nozzle to prevent ink diffusion. Subsequently, the ink cartridge and the orifice plate are bonded using UV curable glue, and metal wires are used to introduce the electrodes from the high-voltage power supply into the ink cartridge, which is then sealed using UV curable glue.

[0060] The control module is selected as a personal computer PC as the host computer, and a single-chip microcomputer is used as the digital main control. Before using the electrohydrodynamic inkjet printhead, first align the mounting holes on the ink cartridge with the threaded holes on the experimental platform, and fix the electrohydrodynamic inkjet printhead to the experimental platform through bolts. Then adjust the electrohydrodynamic inkjet printhead fixture to keep the nozzle parallel to the printing substrate, ensuring that each nozzle receives the same magnitude of electric field force. Subsequently, use a flow pump to pump ethanol solution into the ink cartridge from the ink inlet and discharge the air bubbles in the ink cartridge from the ink outlet. When the ethanol solution fills the ink cartridge, adjust the printhead to an appropriate height.

[0061] The surface tension of ethanol is shown in Table 1, and its boiling point is 78.3 °C. When the printing height is controlled at 1 mm and the ambient temperature is 10 °C, the opening voltage of the nozzle is approximately 900 V.

[0062] When using the electrohydrodynamic inkjet printhead, a signal is output from the personal computer PC to the single-chip microcomputer to control the output of high voltage and laser. First, apply a voltage of 810 V to all nozzles. The electric field force acting on the meniscus at the tip of the nozzle is less than the surface tension acting on the meniscus at the tip of the nozzle, and no jetting occurs at all nozzles. At this time, irradiate the ignition nozzle with a laser to quickly raise the temperature of the ethanol solution to 70 °C. The electric field force acting on the liquid is greater than the surface tension acting on the liquid, and the ignition nozzle starts to jet. When jetting from this nozzle is no longer required, stop the laser irradiation, the temperature drops, and the jetting stops. By controlling the sequential jetting of different nozzles, patterned printing is completed.

[0063] Table 1 Surface tension coefficient of ethanol at different temperatures

[0064]

[0065] It is easy for those skilled in the art to understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An independent injection control method for an arrayed electrohydrodynamic nozzle, characterized in that, By using a laser-induced method to regulate the temperature of the meniscus at the tip of the nozzle, changing the surface tension coefficient of the solution at the tip of the meniscus through the temperature change, realizing the adjustment between the electric field force and the surface tension, and further controlling the independent ejection of each nozzle, including: Method 1: Apply the same working voltage to all nozzles, so that the electric field force on the meniscus at the tip of the nozzle is less than the surface tension. At this time, all nozzles do not eject; irradiate the meniscus at the tip of the ignition nozzle with a laser to raise its temperature to a point where its surface tension is less than the electric field force, thus causing ejection; Or, Method 2: Apply the same working voltage to all nozzles, so that the electric field force on the meniscus at the tip of the nozzle is greater than the surface tension. At this time, all nozzles eject; irradiate the meniscus at the tip of the non-ignition nozzle with a laser to lower its temperature to a point where its surface tension is greater than the electric field force, thus preventing ejection.

2. The independent injection control method for the arrayed electrohydrodynamic nozzle according to claim 1, wherein In Method 1, the working voltage is less than the nozzle opening voltage, and the temperature range regulated by the laser is lower than the boiling point of the solution.

3. The independent injection control method for the arrayed electrohydrodynamic nozzle according to claim 1, characterized in that, In Method 2, the working voltage is 1 to 1.2 times the nozzle opening voltage, and the temperature range regulated by the laser is higher than the melting point of the solution.

4. An array electrohydrodynamic inkjet printing device for implementing the method according to any one of claims 1 to 3, characterized in that, It includes an arrayed electrohydrodynamic inkjet printhead, a high-voltage power supply, a laser module, and a control module; The arrayed electrohydrodynamic inkjet printhead includes an ink cartridge, a nozzle plate, and multiple nozzles; The high-voltage power supply is used to generate the working voltage; The laser module is used to generate multiple laser beams corresponding one-to-one to each nozzle to change the temperature of the meniscus at the tip of each nozzle; The control module is used to control the high-voltage power supply and the laser module to regulate the voltage signal output by the high-voltage power supply and independently control the on / off of each laser beam.

5. The arrayed electrohydrodynamic inkjet printing device according to claim 4, wherein, The laser module consists of a single laser plus a laser beam splitter, or consists of multiple lasers.

6. The arrayed electrohydrodynamic inkjet printing device according to claim 4, wherein, The multiple laser beams generated by the laser module are arranged according to design requirements, and their number matches the number of nozzles.

7. The arrayed electrohydrodynamic inkjet printing device according to claim 4, wherein, The laser module adjusts the power of the laser or the pulse duration of the laser through the control module to achieve the control of the temperature of the meniscus at the tip of the nozzle, and further control the independent ejection of the nozzle.

8. The arrayed electrohydrodynamic inkjet printing device according to claim 4, wherein, The nozzle plate is made of an adiabatic material or has an adiabatic material sandwich layer.

9. The arrayed electrohydrodynamic printing device according to claim 4, wherein, The nozzle is prepared using a heat-conducting material.

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