Addressable arrayed electrohydrodynamic jet control device having top-mounted control electrode and method

Abstract

Disclosed is an addressable arrayed electrohydrodynamic jet control device having a top-mounted control electrode, comprising an ink cartridge used for storing ink, a nozzle plate arranged at the bottom of the ink cartridge, a control electrode, a nozzle array and a high-voltage module. The nozzle plate is a flat plate having through holes, and the control electrode and the nozzle array are arranged on the lower surface of the nozzle plate. The high-voltage module comprises a first high-voltage power supply connected to the ink cartridge and used for applying a working voltage to all nozzles, and a second high-voltage power supply or a third high-voltage power supply connected to the control electrode by means of a high-voltage switch and used for applying a corresponding voltage to the control electrode. The control electrode controls the electric field distribution near the nozzles, and controls the electric field intensity borne by menisci at the tips of the nozzles, so as to achieve regulation between electric field force and surface tension, thus controlling independent jetting of each jet hole. Also disclosed is a jet control method.

Description

Addressable arrayed electrofluid injection control device and method with control electrode positioned above

Technical field

[0001] The present invention belongs to the technical field of inkjet printing, and more particularly, relates to an addressable arrayed electro-fluid jetting control device and method with a control electrode positioned thereon. [Background Technology]

[0002] Inkjet printing, a maskless, additive manufacturing technology, boasts high material utilization and low cost, and holds promising application prospects in many industrial manufacturing fields, such as printed displays and flexible electronics. Currently, traditional inkjet printing technologies, primarily piezoelectric and thermal bubble printing, use extrusion force as the driving force, squeezing droplets from the nozzle orifice through the vibration of piezoelectric ceramics or the expansion of thermal bubbles. This extrusion force makes inkjet printing highly sensitive to ink viscosity, and the extruded droplets are generally larger than the diameter of the nozzle. This results in low printing resolution (>20μm) and a narrow viscosity range (1-20cP), making it difficult to meet the demands of printing multiple materials and higher resolutions. Electrohydrodynamic printing applies a high voltage between the nozzle and substrate, using the electric field to overcome surface tension and "pull" the ink out of the nozzle, producing fine droplets. Electrohydrodynamic printing offers ultra-high resolution, wide ink compatibility (1-10,000cP), and a variety of jetting modes, promising broad application prospects.

[0003] Arrayed electrofluidic printheads are key to the industrialization of electrofluidic inkjet printing. Currently, independently controllable jetting in arrayed electrofluidic printheads is achieved through a bottom-mounted electrode. However, due to the asymmetry of the nozzles, the electric field between the multiple nozzles and the substrate is distorted, causing the jet to deflect onto the external electrode ring, leading to nozzle failure and complicating the assembly, cleaning, and maintenance of the printhead.

[0004] Patent CN201410289239.5 proposes a method for achieving independently controllable printing with a nozzle, but this requires an external extraction electrode below the nozzle, which can easily cause ink to deflect onto the extraction electrode and damage the nozzle. Patent CN202111078207.7 proposes an electrofluidic nozzle for independently controllable printing, but this has significant limitations on the conductivity of the solution.

[0005] [Summary of the invention]

[0006] In response to the defects of the existing technology and the need for improvement, the present invention provides an addressable arrayed electro-fluid injection control device and method with an upper control electrode. The electric field at the nozzle tip is regulated by using an upper control electrode, and the electric field force at the tip of the curved liquid surface is changed by changing the control electrode voltage, thereby controlling the independent and controllable injection of each nozzle hole.

[0007] To achieve the above objectives, in a first aspect, the present invention provides an addressable arrayed electro-fluid injection control device with a control electrode disposed thereon, comprising: an ink cartridge, a nozzle plate, a control electrode, a nozzle array, and a high-voltage module;

[0008] The ink cartridge is used to store ink; the nozzle plate is a flat plate with a through hole and is arranged at the bottom of the ink cartridge, and the through hole is used to guide the ink to flow into the nozzle;

[0009] The lower surface of the nozzle plate is provided with a control electrode and a nozzle array, and the through holes correspond to the control electrodes and the nozzles one by one;

[0010] The high-voltage module includes three high-voltage power supplies and a multi-way high-voltage switch; the first high-voltage power supply is connected to the ink cartridge and is used to apply an operating voltage to all nozzles; the second high-voltage power supply or the third high-voltage power supply is connected to the control electrode through the high-voltage switch and is used to apply a corresponding voltage to the control electrode to control the electric field strength of the curved liquid surface at the nozzle tip, wherein the voltages applied to the control electrode by the second high-voltage power supply and the third high-voltage power supply are different.

[0011] Furthermore, there is an insulating base layer between the control electrode and the nozzle plate, and the greater the thickness of the insulating base layer, the smaller the vertical distance between the control electrode and the nozzle tip, and the greater the impact of the voltage applied to the control electrode on the electric field strength of the curved liquid surface at the nozzle tip.

[0012] Furthermore, an insulating protective layer is provided under the control electrode to prevent conduction between the solution at the nozzle tip and the control electrode.

[0013] Furthermore, the control electrode is prepared on the lower surface of the nozzle plate by an evaporation or sputtering process.

[0014] Furthermore, the nozzle is a boss structure, and the center of each nozzle is collinear with the center of each through hole.

[0015] To achieve the above-mentioned object, in a second aspect, the present invention provides an injection control method implemented by using the addressable arrayed electrofluid injection control device with the control electrode disposed on the first aspect, comprising the following steps:

[0016] In the non-working state, the same working voltage U0 is applied to all nozzles through the first high-voltage power supply, so that the electric field force on the meniscus at the nozzle tip is smaller than the surface tension, and all nozzles do not spray;

[0017] In the working state, a voltage U2 is applied to the control electrode corresponding to the ignition nozzle through the second high-voltage power supply, so that the electric field force on the curved liquid surface at the tip of the ignition nozzle is greater than the surface tension, thereby causing injection; a voltage U1 is applied to the control electrode corresponding to the non-ignition nozzle through the third high-voltage power supply, so that the electric field force on the curved liquid surface at the tip of the non-ignition nozzle is less than the surface tension, thereby preventing injection, and weakening the electric field crosstalk between the ignition / non-ignition nozzles to prevent the injection jet from tilting due to the electric field crosstalk;

[0018] The operating voltage U0 is less than the nozzle opening voltage, U1>U2.

[0019] To achieve the above-mentioned object, in a third aspect, the present invention provides another method for controlling an injection of an electric fluid using the addressable arrayed electro-fluid injection control device with a control electrode disposed on the first aspect, comprising the following steps:

[0020] In the non-working state, the same working voltage U0 is applied to all nozzles through the first high-voltage power supply, so that the electric field force on the meniscus at the nozzle tip is greater than the surface tension, and all nozzles spray;

[0021] In the working state, a voltage U1 is applied to the control electrode corresponding to the non-ignition nozzle through the third high-voltage power supply, so that the electric field force on the curved liquid surface at the tip of the non-ignition nozzle is smaller than the surface tension, thereby preventing injection; a voltage U2 is applied to the control electrode corresponding to the ignition nozzle through the second high-voltage power supply, so that the electric field force on the curved liquid surface at the tip of the ignition nozzle is larger than the surface tension, thereby causing injection, and weakening the electric field crosstalk between the ignition / non-ignition nozzles to prevent the injection jet from tilting due to the electric field crosstalk;

[0022] The operating voltage U0 is greater than the nozzle opening voltage, U1>U2.

[0023] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0024] The present invention controls the electric field distribution near the nozzle by using an upper electrode, controls the electric field strength of the curved liquid surface at the nozzle tip, achieves regulation between the electric field force and the surface tension, and further controls the independent injection of each nozzle hole, with the advantages of good stability, high reliability and easy maintenance.

Brief Description of the Drawings

[0025] FIG1 is a schematic diagram of an addressable array-based electrofluid injection control device with control electrodes provided in an embodiment of the present invention;

[0026] FIG2 is a schematic diagram showing the influence of the control electrode voltage on the field strength at the nozzle tip when the thickness h of the insulating base layer is different according to an embodiment of the present invention;

[0027] FIG3 is a schematic diagram showing the variation of the field intensity at the nozzle tip with the control electrode voltage according to an embodiment of the present invention. [Specific implementation method]

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0029] In the present invention, the terms "first", "second", etc. (if any) in the present invention and the drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0030] In the present invention, an ignition nozzle refers to a nozzle that needs to spray, and a non-ignition nozzle refers to a nozzle that does not need to spray.

[0031] As shown in FIG1 , the present invention provides an addressable arrayed electro-fluid injection control device with a control electrode placed on top, comprising: an ink cartridge, a nozzle plate, a control electrode, a nozzle array, and a high-voltage module.

[0032] Ink cartridges can be made from materials such as plexiglass, glass, and silicon. The ink inlet and outlet are located at the top of the cartridge body. The inlet is used for adding ink, while the outlet is used to remove excess ink and air bubbles. Cartridge mounting holes are located on both sides of the cartridge body for mounting and securing the printhead.

[0033] The orifice plate is a flat plate with through holes and is located at the bottom of the ink cartridge. It uses an insulating glass substrate with a length of approximately 15 mm, a width of 15 mm, and a thickness of 0.5 mm. Five circular through holes with a diameter of 30 μm and a spacing of 0.5 mm are then etched into the glass using laser-induced etching. The orifice plate is created by machining through holes in the insulating flat plate using processes such as laser ablation, photolithography, and sandblasting. These holes guide the solution in the ink cartridge into the nozzles. The insulating material of the orifice plate prevents electrical crosstalk between the control electrodes of different nozzles, thereby improving independent control.

[0034] The nozzle is located at the bottom of the orifice plate and has a hollow boss structure, corresponding one-to-one with the orifice plate through-holes. The solution flows from the ink cartridge through the orifice plate through-holes, enters the nozzle, and is finally sprayed out from the nozzle tip.

[0035] The control electrode is made of conductive material and can be in the shape of a ring, a rectangle, etc. The control electrodes of the same nozzle have the same potential after the electric potential is applied. The control electrodes of different nozzles should be insulated to avoid electrical crosstalk causing control failure.

[0036] Exemplarily, the control electrode is prepared on the lower surface of the nozzle plate by processes such as evaporation or magnetron sputtering, and includes an adhesion layer and a conductive layer. The adhesion layer is chromium with a thickness of 100nm, and the conductive layer is gold with a thickness of 70nm. The control electrode pattern is annular with an inner diameter of 200μm and an outer diameter of 280μm, and is provided with leads and pins for convenient access to the control voltage. Before sputtering the control electrode, a layer of photoresist can be prepared as an insulating base layer to reduce the vertical distance between the nozzle tip and the control electrode. As shown in Figure 2, the greater the thickness h of the insulating base layer, the closer the control electrode is to the nozzle tip, the greater the effect of changing the control electrode voltage on the electric field strength, and the better the control performance. In addition, the shape and size of the control electrode can be adjusted to enhance the performance of the control electrode in regulating the electric field at the nozzle tip.

[0037] The nozzle array is fabricated using SU8 photoresist on the lower surface of the nozzle plate, with an inner diameter of 40 μm and an outer diameter of 80 μm. A Teflon insulating layer is also evaporated as a protective insulating layer to prevent conduction between the control electrode and the solution at the nozzle tip.

[0038] Then glue the ink cartridge and the nozzle plate together, connect one end of the metal wire to the ink cartridge, seal it with glue, and connect the other end to a high-voltage power supply.

[0039] The high-voltage module includes three high-voltage power supplies and a multi-way high-voltage switch. The high-voltage power supply is a high-voltage signal generator that converts low-voltage input signals into high-voltage signals to generate driving force. The multi-way high-voltage switch is responsible for receiving print data and controlling the different high voltages input from multiple high-voltage power supplies to different control electrodes. This is used to regulate the electric field at the nozzle tip and control the ejection behavior of the nozzle array.

[0040] Specifically, the first high-voltage power supply is connected to the ink cartridge and is used to apply a working voltage to all nozzles; the second high-voltage power supply or the third high-voltage power supply is connected to the control electrode through a high-voltage switch and is used to apply a corresponding voltage to the control electrode to control the electric field strength of the curved liquid surface at the nozzle tip, wherein the voltages applied to the control electrode by the second high-voltage power supply and the third high-voltage power supply are different.

[0041] A five-pin FPC circuit board is also prepared, one end of which is connected to the pins in the control electrode pattern on the nozzle plate, and the other end is connected to a multi-way high-voltage switch. The multi-way high-voltage switch is connected to multiple high-voltage power supplies via metal wires.

[0042] A personal computer is selected as the host computer to generate signals for controlling multiple high-voltage switches and low-voltage electrical signals. The generated low-voltage electrical signals are input into multiple high-voltage power supplies, and the high-voltage power supplies output different high-voltage electrical signals.

[0043] The present invention also provides two injection control methods implemented by using the above-mentioned addressable arrayed electrofluid injection control device with the control electrode positioned above:

[0044] Method 1: In the non-working state, the surface tension coefficient of the solution is γ0, and the surface tension of the solution curved surface is F γ0 , for diameter d N The surface tension of the solution interface is F γ0 =4γ0 / d N At this time, the same working voltage U0 is applied to all nozzles through the first high-voltage power supply, so that the electric field force F E0 Less than the surface tension F γ0 , at this time all nozzles do not spray;

[0045] In the working state, a voltage U2 is applied to the control electrode corresponding to the ignition nozzle through the second high-voltage power supply, so that the electric field force on the curved liquid surface at the tip of the ignition nozzle is greater than the surface tension, thereby causing injection; a voltage U1 is applied to the control electrode corresponding to the non-ignition nozzle through the third high-voltage power supply, so that the electric field force on the curved liquid surface at the tip of the non-ignition nozzle is less than the surface tension, thereby preventing injection, and weakening the electric field crosstalk between the ignition / non-ignition nozzles to prevent the injection jet from tilting due to the electric field crosstalk;

[0046] The operating voltage U0 is less than the nozzle opening voltage, U1>U2.

[0047] Mode 2: In the non-working state, the same working voltage U0 is applied to all nozzles through the first high-voltage power supply, so that the electric field force on the meniscus at the nozzle tip is greater than the surface tension, and all nozzles spray;

[0048] In the working state, a voltage U1 is applied to the control electrode corresponding to the non-ignition nozzle through the third high-voltage power supply, so that the electric field force on the curved liquid surface at the tip of the non-ignition nozzle is smaller than the surface tension, thereby preventing injection; a voltage U2 is applied to the control electrode corresponding to the ignition nozzle through the second high-voltage power supply, so that the electric field force on the curved liquid surface at the tip of the ignition nozzle is larger than the surface tension, thereby causing injection, and weakening the electric field crosstalk between the ignition / non-ignition nozzles to prevent the injection jet from tilting due to the electric field crosstalk;

[0049] The operating voltage U0 is greater than the nozzle opening voltage, U1>U2.

[0050] For example, before using the electrofluidic printhead, align the mounting holes on the ink cartridge with the threaded holes on the experimental platform. Secure the printhead to the experimental platform with bolts and adjust the printhead fixture to keep the nozzle parallel to the printing substrate. Then, use a flow pump to pump ethanol solution into the ink inlet and exhaust air from the ink cartridge through the ink outlet. Once the ink cartridge is fully filled with ethanol solution, adjust the printhead to the appropriate height.

[0051] The surface tension of ethanol is 22.32 mN / m. The printing height is controlled to be 0.2 mm and the ambient temperature is 20°C. In this embodiment, the opening field strength of the nozzle is 1.5×10 7 V / m.

[0052] When the electrofluid nozzle is in use, the voltage applied to the solution is controlled by a personal computer to be U0 = 1200V. At this time, the change of the field strength at the nozzle tip with the control electrode voltage is shown in Figure 3. During operation, the voltage applied to all control electrodes is U1 = 1200V. The electric field force on the liquid is less than the surface tension of the liquid, and all nozzles do not spray. Subsequently, the control electrode voltage of the ignition nozzle is reduced to U2 = 500V, so that the electric field at the tip of the ignition nozzle increases, the electric field force on the liquid is greater than the surface tension of the liquid, and the ignition nozzle sprays. By controlling different nozzles to spray in sequence, patterned printing is completed.

[0053] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An addressable array electrohydrodynamic jet control device with a control electrode disposed above, characterized in that Comprising: An ink cartridge, a nozzle plate, a control electrode, a nozzle array, and a high-voltage module; The ink cartridge is used for storing ink liquid; The nozzle plate is a flat plate with through holes and is arranged at the bottom of the ink cartridge, and the through holes are used for guiding the ink liquid to flow into the nozzles; The lower surface of the nozzle plate is provided with a control electrode and a nozzle array, and the through holes correspond to the control electrode and the nozzles one by one; The high-voltage module includes three high-voltage power supplies and multiple high-voltage switches; the first high-voltage power supply is connected to the ink cartridge and is used for applying a working voltage to all nozzles; the second high-voltage power supply or the third high-voltage power supply is connected to the control electrode through a high-voltage switch and is used for applying a corresponding voltage to the control electrode to control the electric field strength received by the meniscus at the tip of the nozzle. Among them, the voltages applied by the second high-voltage power supply and the third high-voltage power supply to the control electrode are different.

2. The addressable array type electrohydrodynamic jet control device with a control electrode disposed thereon according to claim 1, wherein There is also an insulating base layer between the control electrode and the nozzle plate, and the greater the thickness of the insulating base layer, the smaller the vertical distance between the control electrode and the tip of the nozzle, and the greater the influence of the voltage applied to the control electrode on the electric field strength received by the meniscus at the tip of the nozzle.

3. The addressable arrayed electrohydrodynamic jet control device with a control electrode disposed thereon according to claim 1, wherein An insulating protective layer is arranged below the control electrode to avoid conduction between the solution at the tip of the nozzle and the control electrode.

4. The addressable array-type electrohydrodynamic jet control device with a control electrode disposed above, characterized in that The control electrode is prepared on the lower surface of the nozzle plate by evaporation or sputtering process.

5. The addressable arrayed electrohydrodynamic jet control device with a control electrode disposed above, characterized in that, The nozzle is a boss structure, and the centers of all nozzles are collinear with the centers of all the through holes.

6. A jet control method implemented by using the addressable array-type electrohydrodynamic jet control device with a control electrode disposed above as described in any one of claims 1 to 5, characterized in that, Including the following steps: In the non-working state, the same working voltage U0 is applied to all nozzles through the first high-voltage power supply, so that the electric field force received by the meniscus at the tip of the nozzle is less than the surface tension, and at this time all nozzles do not eject; In the working state, a voltage U2 is applied to the control electrode corresponding to the ignition nozzle through the second high-voltage power supply, so that the electric field force received by the meniscus at the tip of the ignition nozzle is greater than the surface tension, thereby ejecting; A voltage U1 is applied to the control electrode corresponding to the non-ignition nozzle through the third high-voltage power supply, so that the electric field force received by the meniscus at the tip of the non-ignition nozzle is less than the surface tension, thereby not ejecting, and weakening the electric field crosstalk between the ignition / non-ignition nozzles to prevent the ejection jet from tilting due to electric field crosstalk; Among them, the working voltage U0 is less than the nozzle opening voltage, and U1 > U2.

7. A jet control method implemented by an addressable array electrohydrodynamic jet control device with a control electrode disposed above, as described in any one of claims 1 to 5, characterized in that Including the following steps: In the non-working state, the same working voltage U0 is applied to all nozzles through the first high-voltage power supply, so that the electric field force received by the meniscus at the tip of the nozzle is greater than the surface tension, and at this time all nozzles eject; In the working state, a voltage U1 is applied to the control electrode corresponding to the non-ignition nozzle through the third high-voltage power supply, so that the electric field force received by the meniscus at the tip of the non-ignition nozzle is less than the surface tension, thereby not ejecting; a voltage U2 is applied to the control electrode corresponding to the ignition nozzle through the second high-voltage power supply, so that the electric field force received by the meniscus at the tip of the ignition nozzle is greater than the surface tension, thereby ejecting, and weakening the electric field crosstalk between the ignition / non-ignition nozzles to prevent the ejection jet from tilting due to electric field crosstalk; Among them, the working voltage U0 is greater than the nozzle opening voltage, and U1 > U2.

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