A high-frequency jet printing method and system based on micro-droplet generation

Abstract

The present application belongs to the field of inkjet printing technology, and particularly relates to a high-frequency inkjet printing method and system based on micro-droplet generation, which comprises: applying a high-voltage high-frequency time-varying electric signal to a micro-nozzle assembly to form a high-frequency time-varying electric field between the nozzle outlet and a grounded substrate; adjusting the electric signal parameters and the output of an ink supply device to generate a Taylor cone / jet at the nozzle outlet, and then stably breaking and fragmenting the Taylor cone / jet at the end to generate uniform micro-droplets; wherein the distance between the nozzle outlet and the surface of the moving substrate is greater than the critical distance required for the Taylor cone or jet to stably break and fragment in the air; the frequency of the high-voltage high-frequency time-varying electric signal is an integer multiple of the inherent frequency of the Taylor cone or jet breaking into droplets; and the ink supply rate of the ink supply device meets: matching the parameters of the high-voltage high-frequency time-varying electric signal to ensure stable breaking and fragmentation by inducing Taylor cone or jet resonance. The present application improves the frequency of electrohydrodynamic jetting while breaking through the characteristic frequency limit.

Description

Technical Field

[0001] This invention belongs to the field of inkjet printing technology, and more specifically, relates to a high-frequency inkjet printing method and system based on microdroplet generation. Background Technology

[0002] Electrohydraulic inkjet printing technology uses an electric field to induce the ejection of functional ink from a nozzle onto a substrate, forming patterned functional structures. Unlike traditional inkjet printing, which "push" ink droplets out of the nozzle, electrohydraulic inkjet printing, in principle, uses a "pulling" method, employing an electric field to draw the ink out of the nozzle, resulting in high resolution. ), wide range of ink viscosity adaptability ( With advantages such as customizable high-precision pattern printing, it has wide applications in flexible electronics manufacturing and even bio-manufacturing.

[0003] However, existing conical jet printing processes mainly form droplets by having the jet directly contact the substrate. This involves the jet directly contacting the substrate and then rebounding to form a meniscus, with some of the jet remaining on the substrate to form deposited droplets. This method of droplet formation through substrate rebound, due to the oscillation and stabilization of the meniscus and the long-range effect of the conical jet, prevents the printing frequency from exceeding the characteristic frequency limit of the meniscus. This significantly restricts the jetting frequency and reduces production efficiency.

[0004] Kim et al. discovered a correlation between voltage pulse frequency and jet frequency, but the jet frequency remained consistently lower than the characteristic frequency. An et al. improved the jet frequency by altering solution properties, such as reducing viscosity, increasing conductivity, and decreasing surface tension. Yang et al. improved the characteristic frequency through high-order jetting modes. Even though existing technologies can increase the jet frequency and even the characteristic frequency (depending on ink properties and printhead structure), the printing frequency of electrofluid jetting remains limited to below the characteristic frequency. Therefore, further improving the electrofluid jetting frequency while simultaneously overcoming its characteristic frequency limitation is a critical technical problem that urgently needs to be solved. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a high-frequency inkjet printing method and system based on microdroplet generation, which aims to improve the electrofluid jetting frequency and break through its characteristic frequency limitation.

[0006] To achieve the above objectives, according to one aspect of the present invention, a high-frequency inkjet printing method based on microdroplet generation is provided, comprising: The inkjet ink is delivered to the nozzle outlet of the micro-nozzle assembly via an ink supply device, forming an ink meniscus at the nozzle outlet. The inner diameter of the nozzle in the micro-nozzle assembly is based on the jetting frequency. Satisfying the inner diameter of the nozzle The relevant relationships are determined based on actual needs; A high-voltage, high-frequency, time-varying electrical signal is applied to the micro-nozzle assembly, forming a high-frequency, time-varying electric field between the nozzle outlet and the grounding substrate. The parameters of the high-voltage, high-frequency, time-varying electrical signal and the ink supply rate of the ink supply device are adjusted so that the ink meniscus at the nozzle outlet overcomes surface tension under the influence of the electric field, generating a Taylor cone. This cone then stably breaks and fragments at its tip, generating uniform microdroplets. Alternatively, a jet can be generated below the Taylor cone simultaneously with its formation, and the jet then breaks and generates uniform microdroplets at its tip. The distance between the nozzle outlet and the surface of the moving substrate is specified. The distance greater than the critical distance required for a Taylor cone or jet to stably fracture and break apart in air. The frequency of high-voltage, high-frequency time-varying electrical signals The natural frequency of Taylor cone or jet break-off droplet formation Integer multiples of; the ink supply rate of the ink supply device satisfies: matching the parameters of the high-voltage, high-frequency time-varying electrical signal, and ensuring stable fracture and breakage by inducing Taylor cone or jet resonance; The control substrate moves along a preset trajectory, and the generated microdroplets can be precisely deposited on the surface of the moving substrate to form a preset pattern, thus completing high-frequency electrohydraulic inkjet printing.

[0007] Furthermore, the formation control method of the high-frequency time-varying electric field is as follows: A high-frequency time-varying electrical signal is output by a signal generator. This signal is then fed into a high-voltage amplifier to form a high-voltage high-frequency time-varying electrical signal. This high-voltage high-frequency time-varying electrical signal is applied to the micro-nozzle assembly. With the high-precision moving platform grounded, a high-frequency time-varying electric field is formed between the nozzle outlet and the grounding substrate.

[0008] Furthermore, the ink supply rate of the ink supply device satisfies the following requirements: matching the parameters of the high-voltage, high-frequency time-varying electrical signal, and ensuring the formation of a single microdroplet within each voltage cycle of the high-voltage, high-frequency time-varying electrical signal by inducing Taylor cone or jet resonance.

[0009] Furthermore, frequency is used Peak-to-peak voltage Bias voltage The high-voltage, high-frequency, time-varying electrical signal is characterized by both the high-level duty cycle D and the high-level duty cycle D. During the formation of microdroplets, the method further includes dynamically adjusting the high-voltage, high-frequency, time-varying electrical signal by monitoring the fracture state of the Taylor cone or jet. , , At least one parameter in D is used to keep the high-voltage, high-frequency time-varying electrical signal matched with the ink supply frequency, thereby maintaining a stable air break.

[0010] Furthermore, the printing frequency is characterized by DC voltage-induced jetting under the same bias conditions. The following experimental methods were used to determine The bias voltage applied to the micro-nozzle assembly is the same as the current bias voltage of the high-voltage, high-frequency time-varying electrical signal. A DC voltage is applied to induce the formation of a stable jet or Taylor cone; the fracture process of the jet or Taylor cone is observed, and the timing signal of microdroplet generation is recorded; the fundamental frequency is extracted by performing spectral analysis on the timing signal, which is the natural frequency. .

[0011] Furthermore, critical distance It can be determined directly through experiments or through a combination of theoretical calculations and experiments; where the method of determination through a combination of theoretical calculations and experiments is as follows: the theoretical formula is... ,in, For ink dynamic viscosity, A constant determined experimentally. Expressed as follows:

[0012] In the formula, This represents the surface tension coefficient at the gas-liquid interface. Represents the vacuum dielectric constant. This indicates the ink flow rate through the nozzle. Indicates the conductivity of the ink. Indicates ink density.

[0013] Furthermore, temperature control is used to maintain the temperature of the micro-nozzle assembly, substrate, and cavity environment. Adjusting the viscosity of the inkjet printing ink to maintain... Greater than .

[0014] Furthermore, the nozzle inner diameter is on the micrometer scale.

[0015] According to another aspect of the present invention, a high-frequency inkjet printing system based on microdroplet generation is provided for performing the high-frequency inkjet printing method as described above, comprising: a high-frequency time-varying power supply module, a micro-nozzle assembly, an inkjet state monitoring module, an ink supply device, a moving platform, and a control module; The ink supply unit delivers printing ink to the nozzle outlet of the micro-nozzle assembly, forming an ink meniscus at the nozzle outlet. The inner diameter of the nozzle in the micro-nozzle assembly is based on the jetting frequency. Satisfying the inner diameter of the nozzle The relevant relationships are determined according to actual needs; the high-frequency time-varying power supply module is used to apply high-voltage high-frequency time-varying electrical signals to the micro-nozzle assembly to form a high-frequency time-varying electric field between the nozzle outlet and the grounding substrate; The control module is used to adjust the parameters of the high-voltage, high-frequency time-varying electrical signal and the ink supply rate of the ink supply device, so that the ink meniscus at the nozzle exit overcomes surface tension under the action of the electric field, generating a Taylor cone, which then stably breaks and fragments at the end of the Taylor cone to generate uniform microdroplets, or simultaneously generates a jet below the Taylor cone, which then breaks and generates uniform microdroplets at the end of the jet; wherein, the distance between the nozzle exit and the surface of the moving substrate is... The distance greater than the critical distance required for a Taylor cone or jet to stably fracture and break apart in air. The frequency of high-voltage, high-frequency time-varying electrical signals The natural frequency of Taylor cone or jet break-off droplet formation The ink supply rate of the ink supply device meets the following requirements: it matches the parameters of the high-voltage, high-frequency time-varying electrical signal, and ensures stable fracture and breakage by inducing Taylor cone or jet resonance; it also controls the high-precision moving platform so that the substrate on it moves according to the preset trajectory, and the generated microdroplets can be accurately deposited on the surface of the moving substrate to form a preset pattern.

[0016] In summary, compared with the prior art, the technical solutions conceived by this invention have the following main advantages: 1. This invention proposes a high-frequency inkjet printing method based on microdroplet generation, employing a micro-nozzle assembly, wherein the inner diameter of the nozzle in the micro-nozzle assembly is based on the jetting frequency. Satisfying the inner diameter of the nozzle The relevant relationships are determined according to actual needs. Based on this, by adjusting parameters such as the distance between the nozzle outlet and the grounded moving substrate, the high-frequency time-varying electrical signal parameters, and the output of the ink supply device, the jet / Taylor cone is made to stably break and shatter in the air. Considering that the oscillation and stabilization of the meniscus and the long-range effect of the cone jet are the main reasons why the printing frequency can never break through the characteristic frequency limit of the meniscus, this invention proposes to break the jet or Taylor cone at the end to generate uniform microdroplets before falling onto the substrate. This avoids the oscillation and stabilization of the meniscus and the long-range effect of the cone jet in traditional cone jet printing, thereby breaking through the characteristic frequency limit of traditional electrohydraulic printing and effectively improving the manufacturing efficiency of electrohydraulic printing. This invention proposes an adjustment strategy where the frequency of the high-frequency electrical signal is an integer multiple of the inherent frequency of the jet / Taylor cone breakage droplet formation. This strategy can significantly enhance the resonance effect during the jetting process, avoid the generation of defects such as satellite droplets during jetting, and improve the consistency of the jetting droplet frequency. In addition, it proposes a principle that the ink supply rate of the ink supply device should match the output of the high-frequency time-varying electrical signal. By inducing Taylor cone or jet resonance, stable breakage can be ensured, which can effectively ensure that the ink supply meets the ink amount required for droplet formation, while avoiding the situation where the breakage phenomenon does not occur due to excessive ink supply. Attached Figure Description

[0017] Figure 1 A flowchart of a high-frequency inkjet printing method based on microdroplet generation is provided for an embodiment of the present invention; Figure 2 This is a schematic diagram of the nozzle spraying state provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of microdroplet generation provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a high-frequency inkjet printing system based on microdroplet generation, provided as an embodiment of the present invention.

[0018] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1. High-frequency time-varying power supply module; 2. Micro-nozzle assembly; 3. Injection status monitoring module; 4. Ink supply device; 5. High-precision moving platform; 11. Signal generator; 12. High-voltage amplifier; 31. Laser light source; 32. High-speed camera. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be 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 illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0020] Example 1 A high-frequency inkjet printing method based on microdroplet generation, such as Figure 1 As shown, it includes: The inkjet ink is delivered to the nozzle outlet of the micro-nozzle assembly via an ink supply device, forming an ink meniscus at the nozzle outlet. The inner diameter of the nozzle in the micro-nozzle assembly is based on the jetting frequency. Satisfying the inner diameter of the nozzle The relevant relationships are determined based on actual needs; A high-voltage, high-frequency, time-varying electrical signal is applied to the micro-nozzle assembly, forming a high-frequency, time-varying electric field between the nozzle outlet and the grounding substrate. The parameters of the high-voltage, high-frequency, time-varying electrical signal and the ink supply rate of the ink supply device are adjusted so that the ink meniscus at the nozzle outlet overcomes surface tension under the influence of the electric field, generating a Taylor cone. This cone then stably breaks and fragments at its tip, generating uniform microdroplets. Alternatively, a jet can be generated below the Taylor cone simultaneously with its formation, and the jet then breaks and generates uniform microdroplets at its tip. The distance between the nozzle outlet and the surface of the moving substrate is specified. The distance greater than the critical distance required for a Taylor cone or jet to stably fracture and break apart in air. The frequency of high-voltage, high-frequency time-varying electrical signals The natural frequency of Taylor cone or jet break-off droplet formation Integer multiples of; the ink supply rate of the ink supply device satisfies: matching the parameters of the high-voltage, high-frequency time-varying electrical signal, and ensuring stable fracture and breakage by inducing Taylor cone or jet resonance; The control substrate moves along a preset trajectory, and the generated microdroplets can be precisely deposited on the surface of the moving substrate to form a preset pattern, thus completing high-frequency electrohydraulic inkjet printing.

[0021] This embodiment proposes a high-frequency inkjet printing method based on microdroplet generation, employing a micro-nozzle assembly. The inner diameter of the nozzle in the micro-nozzle assembly is based on the jetting frequency. Satisfying the inner diameter of the nozzle The relevant relationships are determined according to actual needs. Based on this, by adjusting parameters such as the distance between the nozzle outlet and the grounded moving substrate, the high-frequency time-varying electrical signal parameters, and the output of the ink supply device, the jet / Taylor cone is made to stably break apart in the air. Considering that the oscillation and stabilization of the meniscus and the long-range effect of the cone jet are the main reasons why the printing frequency can never break through the characteristic frequency limit of the meniscus, the method of this embodiment proposes to break the jet or Taylor cone at the end to generate uniform microdroplets before falling onto the substrate. This avoids the oscillation and stabilization of the meniscus and the long-range effect of the cone jet in traditional cone jet printing, thereby breaking through the characteristic frequency limit of traditional electrohydraulic printing and effectively improving the manufacturing efficiency of electrohydraulic printing. In this embodiment, a method is proposed to adjust the frequency of the high-frequency electrical signal to be an integer multiple of the natural frequency of the jet / Taylor cone breakage droplet formation. This can significantly enhance the resonance effect during the jetting process, avoid the generation of defects such as satellite droplets during jetting, and improve the consistency of the jetting droplet frequency. In addition, the principle of matching the ink supply rate of the ink supply device with the output of the high-frequency time-varying electrical signal is proposed. By inducing Taylor cone or jet resonance, stable breakage is ensured, which can effectively ensure that the ink supply amount meets the ink amount required for droplet formation, while avoiding the situation where the breakage phenomenon does not occur due to excessive ink supply.

[0022] In this embodiment, the inner diameter of the nozzle of the micro-nozzle assembly is... R 0. To ensure the system's high-frequency injection capability, the nozzle inner diameter should be... Reduce to a suitable size to increase the injection frequency. Based on the capillary fragmentation mechanism of electrohydrodynamic jet, the injection frequency... The nozzle inner diameter satisfies The scaling law relationship. By reducing the nozzle inner diameter. R 0 can effectively increase the injection frequency. .

[0023] As a preferred embodiment, the nozzle inner diameter is on the micrometer scale. For example, the micro-nozzle assembly adopts a flat-bottom design with a nozzle inner diameter of 10 μm. The nozzle is made of silicon carbide and integrally fabricated using MEMS technology, thus possessing high structural precision. On the other hand, micrometer-scale small-diameter nozzles fabricated using MEMS technology can further increase the spray frequency due to the correlation between smaller nozzle inner diameter and higher spray frequency. Silicon carbide is used here because its low electrical conductivity effectively prevents electrical breakdown between the printhead and the substrate, avoiding printing defects and device damage.

[0024] Distance between nozzle outlet and moving substrate surface Set to a distance greater than the critical distance required for the jet / Taylor cone to stably break in air. That is, The method in this embodiment uses a high-voltage, high-frequency time-varying electrical signal to adjust the droplet generation frequency; otherwise, if a direct current is used, the droplet generation frequency would be fixed.

[0025] As a preferred implementation method, the critical distance Determined directly through experiments or through a combination of theoretical calculations and experiments. The method of determining through a combination of theoretical calculations and experiments is as follows: ,in Indicates the critical distance of the fracture. For ink dynamic viscosity, A constant determined experimentally. It can be expressed as follows:

[0026] In the formula, This represents the surface tension coefficient at the gas-liquid interface. Represents the vacuum dielectric constant. This indicates the ink flow rate through the nozzle. Indicates the conductivity of the ink. Indicates ink density.

[0027] As a preferred implementation method, the formation control method of the high-frequency time-varying electric field is as follows: A high-frequency time-varying electrical signal is output by a signal generator. This signal is then fed into a high-voltage amplifier to form a high-voltage high-frequency time-varying electrical signal. This high-voltage high-frequency time-varying electrical signal is applied to the micro-nozzle assembly. With the high-precision moving platform grounded, a high-frequency time-varying electric field is formed between the nozzle outlet and the grounding substrate.

[0028] A signal generator is used to produce a low-voltage, time-varying electrical signal. This signal has five characteristics: waveform, bias, peak-to-peak value, high-level duty cycle, and frequency. The waveform can be a square wave, triangle wave, sine wave, pulse wave, trapezoidal wave, etc. The low-voltage, high-frequency time-varying electrical signal generated by the signal generator is amplified in a high-voltage amplifier, becoming a high-voltage, high-frequency time-varying electrical signal. Finally, through the circuit, the time-varying signal acts on the micro-nozzle assembly, while the high-precision motion platform is constantly grounded, thereby forming a high-frequency, time-varying electric field between the nozzle outlet and the grounding substrate.

[0029] The ink supply device is a micro-injection pump or a pressure-type ink supply system. The ink supply rate of the ink supply device needs to be effectively controlled to match the output of the high-frequency time-varying electrical signal. As a preferred embodiment, the ink supply rate of the ink supply device satisfies the following: matching the parameters of the high-voltage high-frequency time-varying electrical signal, and ensuring the formation of a single microdroplet in each voltage cycle of the high-voltage high-frequency time-varying electrical signal by inducing Taylor cone or jet resonance.

[0030] As a preferred implementation method, frequency can be used. Peak-to-peak voltage Bias voltage The high-voltage, high-frequency, time-varying electrical signal is characterized by both the high-level duty cycle D and the signal itself. Considering the instability of the electrical signal, the method further includes, during the formation of microdroplets, dynamically adjusting the high-voltage, high-frequency, time-varying electrical signal by monitoring the fracture state of the Taylor cone or jet. , , At least one parameter in D is used to keep the high-voltage, high-frequency time-varying electrical signal matched with the ink supply frequency, thereby maintaining a stable air break.

[0031] For example, the frequency of a high-frequency electrical signal The range is 1kHz to 1MHz, peak-to-peak value. The range is 0kV~5kV, bias The range is 0kV to 5kV.

[0032] To ensure efficient synchronization between the driving signal and the jet fracture process, the frequency of the high-frequency electrical signal ( f s ) should be set to f c Integer multiples of, i.e. This integer multiple relationship can significantly enhance the resonance effect during the jetting process, avoid the generation of defects such as satellite droplets, and improve the consistency of droplet generation size / frequency. (Natural frequency) f cThese are key parameters for Taylor cone / jet breakup and droplet formation, and can be used as preferred implementation methods. Their specific values ​​can be directly determined through experimental observation, characterized by the printing frequency of DC voltage-induced jetting under the same bias conditions. The bias voltage applied to the micro-nozzle assembly is the same as the current bias voltage of the high-voltage, high-frequency time-varying electrical signal. A DC voltage is applied to induce the formation of a stable jet or Taylor cone; the fracture process of this jet or Taylor cone is observed, and the timing signal of microdroplet generation is recorded; by performing spectral analysis on the timing signal, its fundamental frequency is extracted, which is the natural frequency. .

[0033] The natural frequency f c It is a key parameter for Taylor cone / jet breakup and droplet formation, and its specific value can be directly determined through experimental observation. f c With ink charge relaxation coefficient , Onezog number Oh and the Weber number of ink flowing through the nozzle We The following piecewise scaling law relationship exists:

[0034] As a preferred embodiment, temperature control can be used to maintain the temperature of the micro-nozzle assembly, the substrate, and the cavity environment. Adjusting the viscosity of the inkjet ink improves printing characteristics in order to maintain... Greater than .

[0035] For example, The temperature should be controlled between 5℃ and 80℃. The temperature of the micro-nozzle assembly, movable substrate, and cavity environment should be lower than the boiling point of the ink and higher than the melting point of the ink.

[0036] Real-time monitoring of the electrofluid injection status, such as Figure 2 As shown, the states include: State 1, where the jet directly contacts the substrate; State 2, where the long jet breaks off in mid-air; and State 3, where the short jet breaks off in mid-air or directly at the Taylor cone tip. State 1 is an abnormal state, while states 2 and 3 are operating states. Adjusting the jetting state to states 2 or 3 can be achieved by increasing the temperature of the area in contact with the ink or the object, decreasing the printing voltage bias / peak-to-peak / high-level duty cycle, or increasing the distance between the nozzle exit and the movable substrate.

[0037] State 2 and State 3 can be further classified into several stability modes, such as Figure 3As shown: Mode I, stable droplet generation; Mode II, stable droplet generation with satellite droplets; Mode III, droplet generation with increased droplet size; Mode IV, droplet generation with decreased droplet size. Mode I is the operating mode; all other modes are abnormal modes. The occurrence of Mode II is due to the frequency of the high-frequency electrical signal. f s Natural frequency of jet / Taylor cone fracture droplet f c The reason for Mode III not being an integer multiple is that the ink supply system provides too much ink, while the reason for Mode IV is that the ink supply system provides too little ink. Adjusting the jetting mode to Mode I can be achieved by adjusting the printing voltage frequency and the ink supply rate of the ink supply device.

[0038] By monitoring the jetting state in real time and using a fuzzy neural network control algorithm, the distance between the nozzle outlet and the movable substrate, the parameters of the high-frequency time-varying electrical signal, the ink supply rate of the ink supply device, and the temperature of the area or object in contact with the ink can be changed online. This ensures that the jetting state is stable in mode I of state 2 or 3, so as to obtain high-frequency stable droplets.

[0039] The inkjet printing ink is a functional ink, including metal nanoparticle ink, polymer ink, bioactive ink, or quantum dot ink. The viscosity range of the inkjet printing ink is 0.1 μL. ~1000m In this embodiment, the physical properties of the ink used and the ambient air are shown in Table 1 below.

[0040] Table 1

[0041] In summary, the method in this embodiment adjusts parameters such as the distance between the nozzle outlet and the grounded moving substrate, the high-frequency time-varying electrical signal, the back pressure / flow rate of the ink supply device, and the ink viscosity to cause the jet / Taylor cone to break in the air. This avoids the meniscus oscillation stabilization and long-range effect of the conical jet in traditional conical jet printing, breaks through the characteristic frequency limitation of traditional electrohydraulic printing, and effectively improves the manufacturing efficiency of electrohydraulic printing.

[0042] Example 2 A high-frequency inkjet printing system based on microdroplet generation, characterized in that, for executing the high-frequency inkjet printing method as described in Example 1, includes: a high-frequency time-varying power supply module, a micro-nozzle assembly, an ink jetting state monitoring module, an ink supply device, a moving platform, and a control module; The ink supply unit delivers printing ink to the nozzle outlet of the micro-nozzle assembly, forming an ink meniscus at the nozzle outlet. The inner diameter of the nozzle in the micro-nozzle assembly is based on the jetting frequency. Satisfying the inner diameter of the nozzle The relevant relationships are determined according to actual needs; the high-frequency time-varying power supply module is used to apply high-voltage high-frequency time-varying electrical signals to the micro-nozzle assembly to form a high-frequency time-varying electric field between the nozzle outlet and the grounding substrate; The control module is used to adjust the parameters of the high-voltage, high-frequency time-varying electrical signal and the ink supply rate of the ink supply device, so that the ink meniscus at the nozzle exit overcomes surface tension under the action of the electric field, generating a Taylor cone, which then stably breaks and fragments at the end of the Taylor cone to generate uniform microdroplets, or simultaneously generates a jet below the Taylor cone, which then breaks and generates uniform microdroplets at the end of the jet; wherein, the distance between the nozzle exit and the surface of the moving substrate is... The distance greater than the critical distance required for a Taylor cone or jet to stably fracture and break apart in air. The frequency of high-voltage, high-frequency time-varying electrical signals The natural frequency of Taylor cone or jet break-off droplet formation The ink supply rate of the ink supply device meets the following requirements: it matches the parameters of the high-voltage, high-frequency time-varying electrical signal, and ensures stable fracture and breakage by inducing Taylor cone or jet resonance; it also controls the high-precision moving platform so that the substrate on it moves according to the preset trajectory, and the generated microdroplets can be accurately deposited on the surface of the moving substrate to form a preset pattern.

[0043] In practical implementation, the following process can be followed: Build a printing system, including a high-frequency time-varying power supply module, micro-nozzle assembly, jetting status monitoring module, ink supply device, and high-precision moving platform; deliver printing ink to the nozzle outlet of the micro-nozzle assembly via the ink supply device; activate the signal generator and high-voltage amplifier to create a high-frequency time-varying electric field between the nozzle outlet and the grounding substrate; adjust the parameters of the high-frequency electrical signal and the output of the ink supply device to allow the ink meniscus at the nozzle outlet to overcome surface tension under the action of the electric field, generating a Taylor cone and long / short jets, which then break at the end of the Taylor cone / jet to generate uniform microdroplets; control the high-precision moving platform to move the substrate on it according to a preset trajectory, so that the generated microdroplets can be accurately deposited on the surface of the moving substrate to form a preset pattern, ultimately completing high-frequency electrohydraulic printing.

[0044] Configuration and setup of the inkjet printing system: such as Figure 4 As shown, the inkjet printing system includes a high-frequency time-varying power supply module 1, a micro-nozzle assembly 2, an inkjet status monitoring module 3, an ink supply device 4, and a high-precision moving platform 5. The high-frequency time-varying power supply module includes a signal generator 11 and a high-voltage amplifier 12. The high-frequency time-varying power supply module forms a path with the micro-nozzle assembly and the high-precision moving platform, respectively. The inkjet status monitoring module includes a laser light source 31 and a high-speed camera 32. The ink supply device is connected to the micro-nozzle assembly to deliver printing ink. The laser light source and the lens of the high-speed camera are placed coaxially to ensure that sufficient light intensity can be captured by the high-speed camera.

[0045] Ink delivery and meniscus formation: The inkjet ink is delivered to the nozzle outlet of the micro-nozzle assembly through the ink supply device, so that an ink meniscus is formed at the nozzle outlet.

[0046] High-frequency time-varying electric field excitation: Start the signal generator and high-voltage amplifier. The signal generator outputs a high-frequency time-varying electrical signal. This electrical signal is fed into the high-voltage amplifier to form a high-voltage high-frequency time-varying electrical signal. The high-voltage high-frequency time-varying electrical signal is applied between the micro-nozzle assembly and the high-precision moving platform, thereby forming a high-frequency time-varying electric field between the nozzle outlet and the grounding substrate.

[0047] Microdroplet generation: By adjusting the parameters of the high-frequency electrical signal and the output of the ink supply device, the ink meniscus at the nozzle exit overcomes the surface tension under the action of the electric field, generating Taylor cones and long / short jets, which then break at the end of the Taylor cone / jet to generate uniform microdroplets.

[0048] Droplet patterning deposition: Controlling a high-precision moving platform to make the substrate on it move along a preset trajectory, the generated microdroplets can be precisely deposited on the surface of the moving substrate to form a preset pattern, and finally complete the high-frequency electrohydraulic inkjet printing.

[0049] The relevant technical solutions are the same as above, and will not be repeated here.

[0050] In summary, this invention enables electro-inkjet printing to break through the upper limit of the characteristic frequency, effectively improving the jetting frequency and printing efficiency.

[0051] Those skilled in the art will readily understand 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 within the scope of protection of the present invention.

Claims

1. A high-frequency inkjet printing method based on microdroplet generation, characterized in that, include: The inkjet ink is delivered to the nozzle outlet of the micro-nozzle assembly via an ink supply device, forming an ink meniscus at the nozzle outlet. The inner diameter of the nozzle in the micro-nozzle assembly is based on the jetting frequency. Satisfying the inner diameter of the nozzle The relevant relationships are determined based on actual needs; A high-voltage, high-frequency, time-varying electrical signal is applied to the micro-nozzle assembly to form a high-frequency, time-varying electric field between the nozzle outlet and the grounding substrate; By adjusting the parameters of the high-voltage, high-frequency time-varying electrical signal and the ink supply rate of the ink supply device, the ink meniscus at the nozzle exit overcomes surface tension under the action of the electric field, generating a Taylor cone. This cone then stably breaks and fragments at its tip, generating uniform microdroplets. Alternatively, a jet can be generated below the Taylor cone simultaneously with its formation, and the jet then breaks and generates uniform microdroplets at its tip. The distance between the nozzle exit and the surface of the moving substrate is... The distance greater than the critical distance required for a Taylor cone or jet to stably fracture and break apart in air. The frequency of high-voltage, high-frequency time-varying electrical signals The natural frequency of Taylor cone or jet break-off droplet formation Integer multiples of; the ink supply rate of the ink supply device satisfies: matching the parameters of the high-voltage, high-frequency time-varying electrical signal, and ensuring stable fracture and breakage by inducing Taylor cone or jet resonance; The control substrate moves along a preset trajectory, and the generated microdroplets can be precisely deposited on the surface of the moving substrate to form a preset pattern, thus completing high-frequency electrohydraulic inkjet printing.

2. The high-frequency inkjet printing method as described in claim 1, characterized in that, The control method for the formation of high-frequency time-varying electric fields is as follows: A high-frequency time-varying electrical signal is output by a signal generator. This signal is then fed into a high-voltage amplifier to form a high-voltage high-frequency time-varying electrical signal. This high-voltage high-frequency time-varying electrical signal is applied to the micro-nozzle assembly. With the high-precision moving platform grounded, a high-frequency time-varying electric field is formed between the nozzle outlet and the grounding substrate.

3. The high-frequency inkjet printing method as described in claim 1, characterized in that, The ink supply rate of the ink supply device meets the following requirements: it matches the parameters of the high-voltage, high-frequency time-varying electrical signal, and ensures the formation of a single microdroplet in each voltage cycle of the high-voltage, high-frequency time-varying electrical signal by inducing Taylor cone or jet resonance.

4. The high-frequency inkjet printing method according to any one of claims 1 to 3, characterized in that, Frequency Peak-to-peak voltage Bias voltage Together with the high-level duty cycle D, it characterizes the high-voltage, high-frequency, time-varying electrical signal; The method also includes dynamically adjusting the high-voltage, high-frequency time-varying electrical signal by monitoring the fracture state of the Taylor cone or jet. , , At least one parameter in D is used to keep the high-voltage, high-frequency time-varying electrical signal matched with the ink supply frequency, thereby maintaining a stable air break.

5. The high-frequency inkjet printing method as described in claim 1, characterized in that, The printing frequency is characterized by DC voltage-induced jetting under the same bias conditions. ; Determined through the following experimental methods The bias voltage applied to the micro-nozzle assembly is the same as the current bias voltage of the high-voltage, high-frequency time-varying electrical signal. A DC voltage is applied to induce the formation of a stable jet or Taylor cone; the fracture process of the jet or Taylor cone is observed, and the timing signal of microdroplet generation is recorded; the fundamental frequency is extracted by performing spectral analysis on the timing signal, which is the natural frequency. .

6. The high-frequency inkjet printing method as described in claim 1, characterized in that, Critical distance It can be determined directly through experiments or through a combination of theoretical calculations and experiments; where the method of determination through a combination of theoretical calculations and experiments is as follows: the theoretical formula is... ,in, For ink dynamic viscosity, A constant determined experimentally. Expressed as follows: In the formula, This represents the surface tension coefficient at the gas-liquid interface. Represents the vacuum dielectric constant. This indicates the ink flow rate through the nozzle. Indicates the conductivity of the ink. Indicates ink density.

7. The high-frequency inkjet printing method as described in claim 1, characterized in that, Temperature control is used to maintain the temperature of the micro-nozzle assembly, substrate, and cavity environment. Adjusting the viscosity of the inkjet printing ink to maintain... Greater than .

8. The high-frequency inkjet printing method as described in claim 1, characterized in that, The nozzle's inner diameter is on the micrometer scale.

9. A high-frequency inkjet printing system based on microdroplet generation, characterized in that, The method for performing the high-frequency inkjet printing method as described in any one of claims 1 to 8 includes: a high-frequency time-varying power supply module, a micro-nozzle assembly, an inkjet status monitoring module, an ink supply device, a moving platform, and a control module; The ink supply unit delivers printing ink to the nozzle outlet of the micro-nozzle assembly, forming an ink meniscus at the nozzle outlet. The inner diameter of the nozzle in the micro-nozzle assembly is based on the jetting frequency. The nozzle inner diameter satisfies The relevant relationships are determined according to actual needs; the high-frequency time-varying power supply module is used to apply high-voltage high-frequency time-varying electrical signals to the micro-nozzle assembly to form a high-frequency time-varying electric field between the nozzle outlet and the grounding substrate; The control module is used to adjust the parameters of the high-voltage, high-frequency time-varying electrical signal and the ink supply rate of the ink supply device, so that the ink meniscus at the nozzle exit overcomes surface tension under the action of the electric field, generating a Taylor cone, which then stably breaks and fragments at the end of the Taylor cone to generate uniform microdroplets, or simultaneously generates a jet below the Taylor cone, which then breaks and generates uniform microdroplets at the end of the jet; wherein, the distance between the nozzle exit and the surface of the moving substrate is... The distance greater than the critical distance required for a Taylor cone or jet to stably fracture and break apart in air. The frequency of high-voltage, high-frequency time-varying electrical signals The natural frequency of Taylor cone or jet break-off droplet The ink supply rate of the ink supply device meets the following requirements: it matches the parameters of the high-voltage, high-frequency time-varying electrical signal, and ensures stable fracture and breakage by inducing Taylor cone or jet resonance; it also controls the high-precision moving platform so that the substrate on it moves according to the preset trajectory, and the generated microdroplets can be accurately deposited on the surface of the moving substrate to form a preset pattern.

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