Simulation of Piezoelectric Inkjet Printing Using Fluid Structural Interaction

Simulation of Piezoelectric Inkjet Printing Using Fluid Structural Interaction | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Simulation of Piezoelectric Inkjet Printing Using Fluid Structural Interaction Dong Yeol Shin, Jaebum Jeong, Woo Jin Jeong, Seok Hwan Jang, Sung Wook Kang, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5264271/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract As inkjet printers have recently been used to manufacture organic/quantum dot light-emitting diode displays, stable ink drops and control have become important during the printing process. This paper proposes a combination simulation of Ansys Fluent and Ansys Mechanical to find the conditions of stable ink droplets. To confirm the feasibility of the simulation, a jetting simulation of Newtonian fluids with practically constant viscosity was performed, and the results were compared with experimental results. Next, we performed a simulation of commercial non-Newtonian ink whose viscosity changed with a change in shear rate and compared the results with the experimental results. The experimental and simulation outcomes differed under the same voltage conditions. The study findings show that inkjet simulation can be employed not only to find stable drop conditions but also to observe changes in pressure in the inkjet nozzle. inkjet printer Ansys Fluent Ansys Mechanical ink droplet inkjet simulation fluid structural interaction Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction Owing to the current organic light-emitting diode (OLED) technology based on the vacuum deposition process, OLED panels produced using fine metal masks and white OLED technologies have been commercialized. This is because low-molecular-weight organic materials can be selected and deposited into thin films with accurate thickness. However, the vacuum deposition process presents limitations, e.g., the impossibility of manufacturing a large-area display panel and the high cost and time required for the pump to keep the interior of the chamber in a vacuum state. The size of the mask for forming the red, green, blue (RGB) pattern should increase with an increase in the display panel. With an increase in the mask size, the center of the mask bends by gravity, and the precision of the RGB pattern decreases. The use of a thick mask can prevent sagging; however, dead pixels can occur because of thickness. As an alternative to the limited vacuum deposition technology, inkjet printing technology using a solution-type material has been proposed [ 1 ]. The manufacture of a display panel with inkjet printing technology presents the following advantages. (i) It is possible to manufacture a Quantum dot LED (QLED) for a high color gamut. QLEDs have been actively investigated with an external quantum efficiency of 20% or more [ 2 ]. However, quantum dots exist in the form of solutions, dissimilar to powder-type organic materials; thus, it is difficult to form thin films via vacuum deposition processes. Therefore, most QLED studies are conducted using spin coating-based solution processes rather than vacuum deposition [ 3 – 5 ]. Spin coating is an extremely simple process that can be employed to transform a solution-type material into a thin film; however, RGB patterning is impossible and difficult to apply to large-area substrates. Applications developed using spin coating are difficult to commercialize; however, inkjet printing technology can be used to perform the RGB patterning of solution-type materials. (ii) Considering that masks are not used, the amount of material wasted by the mask significantly reduces, and the cost of the process is reduced because it does not require a vacuum state. (iii) Finally, research on inkjet printing technology is actively ongoing because display panels can be printed in large quantities via this technology. The inkjet printing process involves various complex physics [ 6 ], such as piezoelectric elements [ 7 ], nozzle-shaped mechanical engineering [ 8 ], surface energy [ 9 ], kinetic energy of falling droplets [ 10 ], kinetic energy transfer of surface energy, dropping impact on substrates [ 11 – 12 ], effectiveness of surfactants [ 13 ], and absorption on substrates and profiles of thin films [ 14 ]. Owing to the disadvantages presented by the aforementioned physics, it is difficult for the inkjet printing process to stably control the solution dropped from nozzles; thus, the thickness of the thin film formed on the pixel is nonuniform. Sub-pixels are spaced several micrometers apart from each other. When droplets from the nozzle fall more than one drop at a time, the solution may penetrate other adjacent sub-pixels, causing device defects. Thus, the stable control of the solution in the nozzle is extremely important in the development of a display using inkjet printing technology. Currently, the inkjet printing system does not have a quantified standard of input waveforms for stable ink ejection. Considering that drop conditions are dependent on the rheological properties of each ink, the correlation of the input voltage waveform on the rheological properties of the material must be investigated. At the Xi'an University of Technology in China, Yuan et al. [ 15 ] presented the results of an inkjet printing drop simulation study using Ansys Fluent. The nozzle model of a two-dimensional (2D) plane was designed, and analysis was conducted by inferring the speed at which the ink moved outward through the nozzle, considering the density, viscosity, and contact angle of the fluid. In particular, Yuan et al. determined what kind of droplet shape could be obtained by controlling the surface tension, moving speed, and period of the ink [ 15 ]. At Soonchunhyang University, Kwon et al. [ 16 ] measured the meniscus just before ink was dropped, not by entering a constant value, and calculated the function of the speed at which the solution moved by differentiating the movement distance with time. Through the user-defined function (UDF) method, they performed a simulation by inputting the speed function in C language, and the change in voltage was conducted at the desired voltage by multiplying a specific coefficient in the speed function. The specific coefficient matched the experimental result through trial and error, and the simulation and experimental results were observed to be similar [ 16 ]. At Guangzhou University in China, Liang et al. [ 17 ] conducted an inkjet printing drop simulation using Ansys CFX. The piezo inkjet head had a 3D shape, and the analysis was conducted by dropping the ink through a change in the internal pressure according to the displacement of the piezoelectric element. The displacement graph of the piezoelectric element was based on the premise that the shape of the voltage supplied to the element was the same, and the change in voltage was expressed by changing the displacement without measuring the meniscus [ 17 ]. In the aforementioned studies, the method of moving the ink was not the voltage applied to the piezoelectric element but by simply inputting the moving speed of the ink or using the velocity function and the displacement of the piezoelectric element. However, the inkjet printing equipment supplies voltage to the piezoelectric element, and the disadvantage is that accurate information regarding which voltage should be applied to produce the discharge result is unknown. The method of inputting a constant velocity is problematic in that it is impossible to ascertain the exact moving speed of the ink in the nozzle [ 15 ]. The meniscus method measures the displacement by applying the voltage just before it is dropped [ 16 ]. Finally, the method using the displacement of the piezoelectric element is limited in that it is difficult to accurately measure the displacement of an element moving several nanometers [ 17 ]. To overcome the limitations of the existing inkjet printing drop simulation, the present study conducted a simulation in which the ink was dropped from the nozzle through the deformation of the piezoelectric element while supplying voltage to the piezoelectric element. To achieve this, the fluid structural interaction (FSI) method was employed using Ansys Mechanical and Ansys Fluent. In Ansys Mechanical, the input voltage waveform supplied to piezoelectric elements was set, and the ink to be used was set in Ansys Fluent and simulated to be close to the real inkjet printing process method. After verifying the accuracy via Newtonian fluid simulation, non-Newtonian fluid simulation was performed, and the results were compared with the experimental results. 2. Method 2.1 Modeling The modeling of the nozzle was designed using SpaceClaim. Although the nozzle was in the form of a cylinder, only half of the model was designed to reduce the number of meshes and analysis time. In addition, the cross-section was set to symmetry so that the analysis could proceed symmetrically. For the nozzle model, a MJ-AT-01-50 piezo inkjet print head (MicroFab Technologies) was used ( Fig. S1 ), and Fig. S2 shows the nozzle model [ 21 – 24 ]. The total length of the model, total length of the piezoelectric element, nozzle diameter, and length of the air area where the droplets dropped were 26.851 mm, 10 mm, 50 µm, and 1 mm, respectively. To reduce the analysis time, only half of the total shape was implemented in the 3D modeling, and the cross-section was set to symmetry. 2.2 Ansys Mechanical The piezoelectric element applied to the model was barium titanate (BaTiO 3 ), and Table S1 lists its properties. The properties were coded using APDL commands and applied to the element. The physical properties associated with the elasticity of the piezoelectric element may specify which information to use, the compliance matrix ( \(\:\left[{s}^{E}\right]\) ) or stiffness matrix ( \(\:\left[{c}^{E}\right]\) ), using the ANEL command of Ansys APDL. For an elastic constant, the compliance or stiffness matrix was applied. Similarly, the DENS, PIEZ, and PERX (also PERY, PERZ) commands were used for the density, piezoelectric constant, and permittivity of the x-direction, respectively. CIRCU94, a circuit element used for piezoelectric element analysis, was used to supply voltage to the piezoelectric element. Using this method, various types of voltages can be supplied to the piezoelectric element, and each voltage waveform can be precisely modified. Five types of voltages can be supplied using CIRCU94, including constants. In addition to the constant, there are sinusoidal, pulse, exponential, and piecewise linear voltages; the pulse voltage, which is 1 kHz, was used in this study. 2.3 Ansys Fluent Here, we used Newtonian and non-Newtonian fluid inks. The Newtonian fluid was ethyl 4-methylbenzoate (EMB) and 3-ethylbiphenyl (EBP) mixed at a ratio of 8:2. The non-Newtonian fluid was the hole transport layer (HTL) ink of an OLED in which poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) (TFB) is dissolved in cyclohexylbenzene (CHB). The viscosity of EMB + EBP ink, which is Newtonian fluid, was constantly measured at approximately 3 [cP] ( Fig. S3(a) ); that of HTL ink, which is non-Newtonian fluid, tended to gradually decrease with an increase in the shear rate ( Fig. S3(b) ). After measuring the viscosity of the inks, curve fitting was performed using Eq. S1 ( Fig. S3(b) ). Table S2 lists the parameter values of Eq. S1 . Fig. S4 shows the measurement results of the contact angle and surface tension of the inks. Tables S3 and S4 present the property values. This study verified the simulation accuracy using EMB + EBP ink, and simulation was performed with HTL ink. The backflow of the fluid was assumed to be zero as the boundary condition of the inlet. Thus, it was applied as a compressible fluid to form the meniscus in which the solution was sucked into the interior by the piezoelectric element. 3. Results The proposed piezo inkjet structure applies a high negative pressure in the ink channel by bending the piezoelectric device as if it were inflated when a high-voltage electrical signal was applied to the piezoelectric device [ 26 ]. Under the pressure, the ink in the nozzle was sucked into the nozzle to form a meniscus. When the electrical signal supplied to the piezoelectric device disappeared, the piezoelectric device returned to its original state, and a positive pressure was applied in the channel to jet the ink to the outside. The analysis was calculated up to 200 µs with a time step of 50 ns, and different voltage signals were calculated and compared with the experimental results. Figures 1 – 3 show the simulation results for the Newtonian fluid. In each figure, (a), (b), (c), and (d) show the experimental result, simulation result, input voltage waveform, and the total pressure by location in the nozzle over time, respectively. The red dashed and blue solid lines in (c) indicate the input waveforms for the experiment and simulation, respectively. Each result showed an error of approximately 5% with the amplitude of the input voltage waveform (Vmax) of the simulation input voltage waveform relative to the Vmax of the experimental input voltage waveform. Figure 1 (a) shows the experimental result obtained when the input voltage waveform (Vmax) was 40 V and the rising, dwelling, and falling time was 5 µs. Figure 1 (b) shows the simulation results at the input voltage waveform with 38 V of amplitude when the rising, dwelling, and falling time was 5 µs. Both results revealed stable jetting. Figure 1 (d) confirms that the pressure in the nozzle operated the negative pressure in the piezoelectric element region during the rising time of the input voltage. After the rising time was over, positive pressure began to be applied to the piezoelectric element region. It was confirmed that the positive pressure advanced toward the nozzle inlet over time. The minimum and maximum values of the internal pressure were − 140 and 130 kPa, respectively. Figure 2 (a) shows the experimental result at a Vmax of 45 V and the rising, dwelling, and falling time of 5 µs. Figure 2 (b) shows the simulation results at the input voltage waveform with 42.75 V of amplitude at a rising, dwelling, and falling time of 5 µs. A 12.5% increase was observed in the Vmax compared with that shown in Fig. 1 . The falling droplet was faster than that shown in Fig. 1 . Similar to the trend shown in Fig. 1 , the experimental and simulation results exhibited stable jetting. As shown in Fig. 1 (d) , it was confirmed that the pressure in Fig. 2 (d) was negative pressure applied at the rising time of the input voltage. Thereafter, positive pressure was applied, leading the wave to the nozzle inlet. However, the difference between Figs. 1 (d) and 2(d) was the magnitude of the pressure. The maximum and minimum internal pressures increased with an increase in the input voltage. Figure 2 (d) shows that the minimum and maximum values of the internal pressure were − 157 and 147 kPa, respectively. It was confirmed that the drop speed of the jetted inkjet droplet exceeded that shown in Fig. 1 (b) , as the higher positive pressure advanced toward the nozzle inlet. Figure 3 (a) shows the experimental result at the input voltage waveform with 35 V of amplitude and the rising, dwelling, and falling time of 5 µs. Figure 3 (b) shows the simulation results at the input voltage waveform with a Vmax of 33.25 V when the rising, dwelling, and falling time was 5 µs. This was a 12.5% decrease in the Vmax compared with Fig. 1 . Compared with that shown in Fig. 1 , the jetting tended to be separated from the nozzle and then sucked back into the nozzle, and the simulation calculated the same results. The calculated pressure was lower than those shown in Figs. 1 (d) and 2(d) . The minimum and maximum internal pressures were − 122 and 114 kPa, respectively. The positive pressure generated in the nozzle was transmitted to the nozzle inlet. However, the maximum pressure was not sufficiently formed for the inkjet droplet to be jetted out of the nozzle. Thus, it was confirmed that the inkjet simulation setup used in this study had an error of approximately 5% of the input voltage waveform. Subsequently, we attempted to find the input voltage waveform of the stable jetting for the non-Newtonian fluid, and Fig. 4 shows the results. Owing to the simulation, the input voltage waveform for the stable jetting of the non-Newtonian fluid was 33.25 V of amplitude. The input voltage waveform was 6 µs of the rising and falling time and 12 µs of dwell time. By applying the 5% error of the previous Newtonian fluid simulation, 35 V (a 5% compensation value of 33.25 V) was entered for the experimental results. Consequently, Fig. 4 (a) shows the trend. Figures 4 (a)(b) shows a stable drop trend; however, the drop speed was different. This was probably because the piezoelectric force was not sufficiently transferred to the solution by the high viscosity of the non-Newtonian fluid at rest. In addition, an error possibly occurred in the fitting using Eq. S1 . Fig. S3(b) shows that the viscosity measurement value was not stable in the region where the shear rate was approximately 0.01–1. The shear rate was extremely low because the fluid was at rest before the inkjet droplets were jetted. The viscosity at that time could significantly influence the simulation of the non-Newtonian fluid. Furthermore, the internal pressure wave was different from before. After the negative pressure was applied, the wave formed when the positive pressure was applied was not completely transmitted to the nozzle inlet. Thus, it is important to observe the trend of internal pressure waves for the rapid and stable jetting of droplets. The present simulation focused on three variables (contact angle, surface tension, and viscosity), which served as representative drop conditions. However, it is important to acknowledge that inkjet equipment encompasses a broader range of variables that can impact the process. Factors, such as temperature, humidity, and equipment conditions, were not incorporated into the simulation, thereby contributing to the disparities between the simulation results and real-world trends. Moreover, the performance of inkjet equipment heavily relies on the driver, responsible for supplying voltage to the piezoelectric device and facilitating ink ejection. Nevertheless, owing to environmental influences, the power transmission from the piezoelectric device to the ink may not have been fully efficient. Variables, such as temperature and humidity variations, can adversely affect the overall functionality of the equipment, potentially causing deviations from the anticipated outcomes. Furthermore, the simulation might underestimate the voltage applied to the equipment. Limitations and simplifications inherent in the modeling process might lead to a lower simulated input voltage waveform delivered to the piezoelectric device, compared with the true input voltage waveform. This voltage discrepancy can further contribute to discrepancies between the simulation results and real-world observations. Thus, the limited scope of variables considered in the simulation, the omission of environmental factors, and the potential underestimation of input voltage waveform contribute to incongruities between the simulation and experimental results. Thus, these limitations must be considered when interpreting and applying the findings of the present simulation to real-world trends. 4. Conclusions Here, the inkjet printing process by piezoelectric actuators was simulated using Ansys Fluent and Ansys Mechanical. Ansys APDL and CIRCU94 were used to calculate the displacement of piezoelectric actuators in Ansys Mechanical. The data of the displacement and internal pressure of the piezoelectric element calculated by Ansys Mechanical were transmitted to Ansys Fluent to implement the ejection of Newtonian and non-Newtonian inks. It is difficult to identify the material of the piezoelectric element used in the nozzle; thus, a simulation was conducted with information on the BaTiO 3 piezoelectric actuator. Therefore, the simulation and experimental results differed under the same voltage conditions. Thus, the voltage was changed to be similar to the experimental value by lowering the amplitude of the voltage input in the simulation. Based on the properties of the BaTiO 3 piezoelectric element, it was confirmed that the error was similar to the experimental results when an error was applied by 5% of the maximum input voltage waveform. If the exact shape and material in the nozzle are known, more accurate simulation results can be obtained. The industry spends considerable time setting input waveform conditions for a stable drop. If the input conditions for the stable drop are calculated through simulation and applied to the process, the required time can significantly reduce. This study ultimately aimed to create a stable inkjet printing drop model for the rheological properties of different materials. If a standard model that can predict drops only with the rheological properties of materials is established, this will promote the industrialization of OLED and QLED displays through the inkjet printing process. Declarations Acknowledgments This study was conducted with support from Ministry of Trade, Industry & Energy (MOTIE, No. 20010464). And This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. RS-2023-00222166). And this research was supported by "Regional Innovation Strategy (RIS)" through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (MOE)(2021RIS-003). Author contributions Dong Yeol Shin : Writing- original draft, Formal analysis. Jaebum Jeong: editing. Woo Jin Jeong: data curation . Seok Hwan Jang : data curation, Sung Wook Kang: Resource. Kyung-Tae Kang: Formal analysis. Jun Young Kim: Writing-review & editing, Writing-original draft, Resources, Formal analysis, Conceptualization. Declaration of interests The authors declare no conflict of interest. Declaration of generative AI in scientific writing This manuscript has been prepared without the use of generative AI technologies. Availability of Data and Materials The datasets generated during the current study are available from the corresponding author on reasonable request. AUTHOR INFORMATION Corresponding Author * [email protected] (Jun Young Kim) References Zheng, X.; Liu, Y.; Zhu, Y.; Ma, F.; Feng, C.; Yu, Y.; Hu. H.; Li, F. Efficient inkjet-printed blue OLED with boosted charge transport using host doping for application in pixelated display. Opt Mater . 2020 , 101 , 109755. DOI: 10.1016/j.optmat.2020.109755 Won, Y. H.; Cho, O.; Kim, T.; Chung, D. Y.; Kim, T.; Chung, H.; Jang, H.; Lee, J.; Kim, D.; Jang, E. Highly efficient and stable InP/ZnSe/ZnS quantum dot light-emitting diodes. Nature , 2019 , 575 (7784), 634-638. DOI: 10.1038/s41586-019-1771-5 Wang, L.; Lin, J.; Hu, Y.; Guo, X.; Lv, Y.; Tang, Z.; Zhao, J.; Fan, Y.; Zhang, N.; Wang, Y.; Liu, X. 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(b) Simulation result at input voltage waveform with 38 V of amplitude. (c) Input voltage waveforms. (d) Waterfall graph of total pressure by location in the nozzle over time.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5264271/v1/3a90f04d1de13e169427bc4b.png"},{"id":67840469,"identity":"6c49cc7c-0f5d-4f56-975b-b87b5351a0ab","added_by":"auto","created_at":"2024-10-30 09:07:49","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":446130,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Experimental result at input voltage waveform with 45 V of amplitude. (b) Simulation result at input voltage waveform with 42.75 V of amplitude. (c) Input voltage waveforms. (d) Waterfall graph of total pressure by location in the nozzle over time.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5264271/v1/32315c33bfff8865c9c865ea.png"},{"id":67840470,"identity":"6d728e30-b7d8-4569-8785-620844b4e332","added_by":"auto","created_at":"2024-10-30 09:07:49","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":438828,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Experimental result at input voltage waveform with 35 V of amplitude. (b) Simulation result at input voltage waveform with 33.25 V of amplitude. (c) Input voltage waveforms. (d) Waterfall graph of total pressure by location in the nozzle over time.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5264271/v1/eee53245bf5708f048d79f30.png"},{"id":67842016,"identity":"e15f0f37-a048-4049-a1a6-e01bddda86c9","added_by":"auto","created_at":"2024-10-30 09:15:49","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":448692,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Experimental result at input voltage waveform with 35 V of amplitude. (b) Simulation result at input voltage waveform with 33.25 V of amplitude. (c) Input voltage waveforms. (d) Waterfall graph of total pressure by location in the nozzle over time.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5264271/v1/50aea04e9e2ff551fa2645b8.png"},{"id":76134339,"identity":"d5c9fd4d-ab3d-4873-a48a-df964e139d67","added_by":"auto","created_at":"2025-02-12 16:02:19","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2717189,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5264271/v1/a7550649-0e4a-43bd-9836-25108184e164.pdf"},{"id":67840471,"identity":"f9ce6596-69b4-457c-a732-3b27605d7189","added_by":"auto","created_at":"2024-10-30 09:07:49","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":4989339,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementarySimulationManuscriptSR.docx","url":"https://assets-eu.researchsquare.com/files/rs-5264271/v1/9c19414a94e4d3012542940d.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Simulation of Piezoelectric Inkjet Printing Using Fluid Structural Interaction","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eOwing to the current organic light-emitting diode (OLED) technology based on the vacuum deposition process, OLED panels produced using fine metal masks and white OLED technologies have been commercialized. This is because low-molecular-weight organic materials can be selected and deposited into thin films with accurate thickness. However, the vacuum deposition process presents limitations, e.g., the impossibility of manufacturing a large-area display panel and the high cost and time required for the pump to keep the interior of the chamber in a vacuum state. The size of the mask for forming the red, green, blue (RGB) pattern should increase with an increase in the display panel. With an increase in the mask size, the center of the mask bends by gravity, and the precision of the RGB pattern decreases. The use of a thick mask can prevent sagging; however, dead pixels can occur because of thickness. As an alternative to the limited vacuum deposition technology, inkjet printing technology using a solution-type material has been proposed [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The manufacture of a display panel with inkjet printing technology presents the following advantages. (i) It is possible to manufacture a Quantum dot LED (QLED) for a high color gamut. QLEDs have been actively investigated with an external quantum efficiency of 20% or more [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. However, quantum dots exist in the form of solutions, dissimilar to powder-type organic materials; thus, it is difficult to form thin films via vacuum deposition processes. Therefore, most QLED studies are conducted using spin coating-based solution processes rather than vacuum deposition [\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Spin coating is an extremely simple process that can be employed to transform a solution-type material into a thin film; however, RGB patterning is impossible and difficult to apply to large-area substrates. Applications developed using spin coating are difficult to commercialize; however, inkjet printing technology can be used to perform the RGB patterning of solution-type materials. (ii) Considering that masks are not used, the amount of material wasted by the mask significantly reduces, and the cost of the process is reduced because it does not require a vacuum state. (iii) Finally, research on inkjet printing technology is actively ongoing because display panels can be printed in large quantities via this technology.\u003c/p\u003e \u003cp\u003eThe inkjet printing process involves various complex physics [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], such as piezoelectric elements [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], nozzle-shaped mechanical engineering [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], surface energy [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], kinetic energy of falling droplets [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], kinetic energy transfer of surface energy, dropping impact on substrates [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e], effectiveness of surfactants [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], and absorption on substrates and profiles of thin films [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Owing to the disadvantages presented by the aforementioned physics, it is difficult for the inkjet printing process to stably control the solution dropped from nozzles; thus, the thickness of the thin film formed on the pixel is nonuniform. Sub-pixels are spaced several micrometers apart from each other. When droplets from the nozzle fall more than one drop at a time, the solution may penetrate other adjacent sub-pixels, causing device defects. Thus, the stable control of the solution in the nozzle is extremely important in the development of a display using inkjet printing technology. Currently, the inkjet printing system does not have a quantified standard of input waveforms for stable ink ejection. Considering that drop conditions are dependent on the rheological properties of each ink, the correlation of the input voltage waveform on the rheological properties of the material must be investigated.\u003c/p\u003e \u003cp\u003eAt the Xi'an University of Technology in China, Yuan et al. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] presented the results of an inkjet printing drop simulation study using Ansys Fluent. The nozzle model of a two-dimensional (2D) plane was designed, and analysis was conducted by inferring the speed at which the ink moved outward through the nozzle, considering the density, viscosity, and contact angle of the fluid. In particular, Yuan et al. determined what kind of droplet shape could be obtained by controlling the surface tension, moving speed, and period of the ink [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. At Soonchunhyang University, Kwon et al. [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] measured the meniscus just before ink was dropped, not by entering a constant value, and calculated the function of the speed at which the solution moved by differentiating the movement distance with time. Through the user-defined function (UDF) method, they performed a simulation by inputting the speed function in C language, and the change in voltage was conducted at the desired voltage by multiplying a specific coefficient in the speed function. The specific coefficient matched the experimental result through trial and error, and the simulation and experimental results were observed to be similar [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. At Guangzhou University in China, Liang et al. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] conducted an inkjet printing drop simulation using Ansys CFX. The piezo inkjet head had a 3D shape, and the analysis was conducted by dropping the ink through a change in the internal pressure according to the displacement of the piezoelectric element. The displacement graph of the piezoelectric element was based on the premise that the shape of the voltage supplied to the element was the same, and the change in voltage was expressed by changing the displacement without measuring the meniscus [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. In the aforementioned studies, the method of moving the ink was not the voltage applied to the piezoelectric element but by simply inputting the moving speed of the ink or using the velocity function and the displacement of the piezoelectric element. However, the inkjet printing equipment supplies voltage to the piezoelectric element, and the disadvantage is that accurate information regarding which voltage should be applied to produce the discharge result is unknown. The method of inputting a constant velocity is problematic in that it is impossible to ascertain the exact moving speed of the ink in the nozzle [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The meniscus method measures the displacement by applying the voltage just before it is dropped [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Finally, the method using the displacement of the piezoelectric element is limited in that it is difficult to accurately measure the displacement of an element moving several nanometers [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTo overcome the limitations of the existing inkjet printing drop simulation, the present study conducted a simulation in which the ink was dropped from the nozzle through the deformation of the piezoelectric element while supplying voltage to the piezoelectric element. To achieve this, the fluid structural interaction (FSI) method was employed using Ansys Mechanical and Ansys Fluent. In Ansys Mechanical, the input voltage waveform supplied to piezoelectric elements was set, and the ink to be used was set in Ansys Fluent and simulated to be close to the real inkjet printing process method. After verifying the accuracy via Newtonian fluid simulation, non-Newtonian fluid simulation was performed, and the results were compared with the experimental results.\u003c/p\u003e"},{"header":"2. Method","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Modeling\u003c/h2\u003e \u003cp\u003eThe modeling of the nozzle was designed using SpaceClaim. Although the nozzle was in the form of a cylinder, only half of the model was designed to reduce the number of meshes and analysis time. In addition, the cross-section was set to symmetry so that the analysis could proceed symmetrically. For the nozzle model, a MJ-AT-01-50 piezo inkjet print head (MicroFab Technologies) was used (\u003cb\u003eFig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e\u003c/b\u003e), and \u003cb\u003eFig. S2\u003c/b\u003e shows the nozzle model [\u003cspan additionalcitationids=\"CR22 CR23\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. The total length of the model, total length of the piezoelectric element, nozzle diameter, and length of the air area where the droplets dropped were 26.851 mm, 10 mm, 50 \u0026micro;m, and 1 mm, respectively. To reduce the analysis time, only half of the total shape was implemented in the 3D modeling, and the cross-section was set to symmetry.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Ansys Mechanical\u003c/h2\u003e \u003cp\u003eThe piezoelectric element applied to the model was barium titanate (BaTiO\u003csub\u003e3\u003c/sub\u003e), and \u003cb\u003eTable \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e\u003c/b\u003e lists its properties. The properties were coded using APDL commands and applied to the element. The physical properties associated with the elasticity of the piezoelectric element may specify which information to use, the compliance matrix (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\left[{s}^{E}\\right]\\)\u003c/span\u003e\u003c/span\u003e) or stiffness matrix (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\left[{c}^{E}\\right]\\)\u003c/span\u003e\u003c/span\u003e), using the ANEL command of Ansys APDL. For an elastic constant, the compliance or stiffness matrix was applied. Similarly, the DENS, PIEZ, and PERX (also PERY, PERZ) commands were used for the density, piezoelectric constant, and permittivity of the x-direction, respectively.\u003c/p\u003e \u003cp\u003eCIRCU94, a circuit element used for piezoelectric element analysis, was used to supply voltage to the piezoelectric element. Using this method, various types of voltages can be supplied to the piezoelectric element, and each voltage waveform can be precisely modified. Five types of voltages can be supplied using CIRCU94, including constants. In addition to the constant, there are sinusoidal, pulse, exponential, and piecewise linear voltages; the pulse voltage, which is 1 kHz, was used in this study.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Ansys Fluent\u003c/h2\u003e \u003cp\u003eHere, we used Newtonian and non-Newtonian fluid inks. The Newtonian fluid was ethyl 4-methylbenzoate (EMB) and 3-ethylbiphenyl (EBP) mixed at a ratio of 8:2. The non-Newtonian fluid was the hole transport layer (HTL) ink of an OLED in which poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) (TFB) is dissolved in cyclohexylbenzene (CHB). The viscosity of EMB\u0026thinsp;+\u0026thinsp;EBP ink, which is Newtonian fluid, was constantly measured at approximately 3 [cP] (\u003cb\u003eFig. S3(a)\u003c/b\u003e); that of HTL ink, which is non-Newtonian fluid, tended to gradually decrease with an increase in the shear rate (\u003cb\u003eFig. S3(b)\u003c/b\u003e). After measuring the viscosity of the inks, curve fitting was performed using \u003cb\u003eEq. S1\u003c/b\u003e (\u003cb\u003eFig. S3(b)\u003c/b\u003e). \u003cb\u003eTable S2\u003c/b\u003e lists the parameter values of \u003cb\u003eEq. S1\u003c/b\u003e. \u003cb\u003eFig. S4\u003c/b\u003e shows the measurement results of the contact angle and surface tension of the inks. \u003cb\u003eTables S3\u003c/b\u003e and \u003cb\u003eS4\u003c/b\u003e present the property values.\u003c/p\u003e \u003cp\u003eThis study verified the simulation accuracy using EMB\u0026thinsp;+\u0026thinsp;EBP ink, and simulation was performed with HTL ink. The backflow of the fluid was assumed to be zero as the boundary condition of the inlet. Thus, it was applied as a compressible fluid to form the meniscus in which the solution was sucked into the interior by the piezoelectric element.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cp\u003eThe proposed piezo inkjet structure applies a high negative pressure in the ink channel by bending the piezoelectric device as if it were inflated when a high-voltage electrical signal was applied to the piezoelectric device [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Under the pressure, the ink in the nozzle was sucked into the nozzle to form a meniscus. When the electrical signal supplied to the piezoelectric device disappeared, the piezoelectric device returned to its original state, and a positive pressure was applied in the channel to jet the ink to the outside. The analysis was calculated up to 200 \u0026micro;s with a time step of 50 ns, and different voltage signals were calculated and compared with the experimental results.\u003c/p\u003e \u003cp\u003eFigures\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e show the simulation results for the Newtonian fluid. In each figure, (a), (b), (c), and (d) show the experimental result, simulation result, input voltage waveform, and the total pressure by location in the nozzle over time, respectively. The red dashed and blue solid lines in (c) indicate the input waveforms for the experiment and simulation, respectively. Each result showed an error of approximately 5% with the amplitude of the input voltage waveform (Vmax) of the simulation input voltage waveform relative to the Vmax of the experimental input voltage waveform.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e(a)\u003c/b\u003e shows the experimental result obtained when the input voltage waveform (Vmax) was 40 V and the rising, dwelling, and falling time was 5 \u0026micro;s. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e(b)\u003c/b\u003e shows the simulation results at the input voltage waveform with 38 V of amplitude when the rising, dwelling, and falling time was 5 \u0026micro;s. Both results revealed stable jetting. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e(d)\u003c/b\u003e confirms that the pressure in the nozzle operated the negative pressure in the piezoelectric element region during the rising time of the input voltage. After the rising time was over, positive pressure began to be applied to the piezoelectric element region. It was confirmed that the positive pressure advanced toward the nozzle inlet over time. The minimum and maximum values of the internal pressure were \u0026minus;\u0026thinsp;140 and 130 kPa, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e(a)\u003c/b\u003e shows the experimental result at a Vmax of 45 V and the rising, dwelling, and falling time of 5 \u0026micro;s. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e(b)\u003c/b\u003e shows the simulation results at the input voltage waveform with 42.75 V of amplitude at a rising, dwelling, and falling time of 5 \u0026micro;s. A 12.5% increase was observed in the Vmax compared with that shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The falling droplet was faster than that shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Similar to the trend shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the experimental and simulation results exhibited stable jetting. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e(d)\u003c/b\u003e, it was confirmed that the pressure in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e(d)\u003c/b\u003e was negative pressure applied at the rising time of the input voltage. Thereafter, positive pressure was applied, leading the wave to the nozzle inlet. However, the difference between Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e(d) and 2(d)\u003c/b\u003e was the magnitude of the pressure. The maximum and minimum internal pressures increased with an increase in the input voltage. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e(d)\u003c/b\u003e shows that the minimum and maximum values of the internal pressure were \u0026minus;\u0026thinsp;157 and 147 kPa, respectively. It was confirmed that the drop speed of the jetted inkjet droplet exceeded that shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e(b)\u003c/b\u003e, as the higher positive pressure advanced toward the nozzle inlet.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e(a)\u003c/b\u003e shows the experimental result at the input voltage waveform with 35 V of amplitude and the rising, dwelling, and falling time of 5 \u0026micro;s. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e(b)\u003c/b\u003e shows the simulation results at the input voltage waveform with a Vmax of 33.25 V when the rising, dwelling, and falling time was 5 \u0026micro;s. This was a 12.5% decrease in the Vmax compared with Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Compared with that shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the jetting tended to be separated from the nozzle and then sucked back into the nozzle, and the simulation calculated the same results. The calculated pressure was lower than those shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e(d)\u003c/b\u003e and \u003cb\u003e2(d)\u003c/b\u003e. The minimum and maximum internal pressures were \u0026minus;\u0026thinsp;122 and 114 kPa, respectively. The positive pressure generated in the nozzle was transmitted to the nozzle inlet. However, the maximum pressure was not sufficiently formed for the inkjet droplet to be jetted out of the nozzle.\u003c/p\u003e \u003cp\u003eThus, it was confirmed that the inkjet simulation setup used in this study had an error of approximately 5% of the input voltage waveform. Subsequently, we attempted to find the input voltage waveform of the stable jetting for the non-Newtonian fluid, and Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the results. Owing to the simulation, the input voltage waveform for the stable jetting of the non-Newtonian fluid was 33.25 V of amplitude. The input voltage waveform was 6 \u0026micro;s of the rising and falling time and 12 \u0026micro;s of dwell time. By applying the 5% error of the previous Newtonian fluid simulation, 35 V (a 5% compensation value of 33.25 V) was entered for the experimental results. Consequently, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cb\u003e(a)\u003c/b\u003e shows the trend.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigures\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cb\u003e(a)(b)\u003c/b\u003e shows a stable drop trend; however, the drop speed was different. This was probably because the piezoelectric force was not sufficiently transferred to the solution by the high viscosity of the non-Newtonian fluid at rest. In addition, an error possibly occurred in the fitting using \u003cb\u003eEq. S1\u003c/b\u003e. \u003cb\u003eFig. S3(b)\u003c/b\u003e shows that the viscosity measurement value was not stable in the region where the shear rate was approximately 0.01\u0026ndash;1. The shear rate was extremely low because the fluid was at rest before the inkjet droplets were jetted. The viscosity at that time could significantly influence the simulation of the non-Newtonian fluid. Furthermore, the internal pressure wave was different from before. After the negative pressure was applied, the wave formed when the positive pressure was applied was not completely transmitted to the nozzle inlet. Thus, it is important to observe the trend of internal pressure waves for the rapid and stable jetting of droplets.\u003c/p\u003e \u003cp\u003eThe present simulation focused on three variables (contact angle, surface tension, and viscosity), which served as representative drop conditions. However, it is important to acknowledge that inkjet equipment encompasses a broader range of variables that can impact the process. Factors, such as temperature, humidity, and equipment conditions, were not incorporated into the simulation, thereby contributing to the disparities between the simulation results and real-world trends. Moreover, the performance of inkjet equipment heavily relies on the driver, responsible for supplying voltage to the piezoelectric device and facilitating ink ejection. Nevertheless, owing to environmental influences, the power transmission from the piezoelectric device to the ink may not have been fully efficient. Variables, such as temperature and humidity variations, can adversely affect the overall functionality of the equipment, potentially causing deviations from the anticipated outcomes. Furthermore, the simulation might underestimate the voltage applied to the equipment. Limitations and simplifications inherent in the modeling process might lead to a lower simulated input voltage waveform delivered to the piezoelectric device, compared with the true input voltage waveform. This voltage discrepancy can further contribute to discrepancies between the simulation results and real-world observations. Thus, the limited scope of variables considered in the simulation, the omission of environmental factors, and the potential underestimation of input voltage waveform contribute to incongruities between the simulation and experimental results. Thus, these limitations must be considered when interpreting and applying the findings of the present simulation to real-world trends.\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eHere, the inkjet printing process by piezoelectric actuators was simulated using Ansys Fluent and Ansys Mechanical. Ansys APDL and CIRCU94 were used to calculate the displacement of piezoelectric actuators in Ansys Mechanical. The data of the displacement and internal pressure of the piezoelectric element calculated by Ansys Mechanical were transmitted to Ansys Fluent to implement the ejection of Newtonian and non-Newtonian inks. It is difficult to identify the material of the piezoelectric element used in the nozzle; thus, a simulation was conducted with information on the BaTiO\u003csub\u003e3\u003c/sub\u003e piezoelectric actuator. Therefore, the simulation and experimental results differed under the same voltage conditions. Thus, the voltage was changed to be similar to the experimental value by lowering the amplitude of the voltage input in the simulation. Based on the properties of the BaTiO\u003csub\u003e3\u003c/sub\u003e piezoelectric element, it was confirmed that the error was similar to the experimental results when an error was applied by 5% of the maximum input voltage waveform. If the exact shape and material in the nozzle are known, more accurate simulation results can be obtained. The industry spends considerable time setting input waveform conditions for a stable drop. If the input conditions for the stable drop are calculated through simulation and applied to the process, the required time can significantly reduce. This study ultimately aimed to create a stable inkjet printing drop model for the rheological properties of different materials. If a standard model that can predict drops only with the rheological properties of materials is established, this will promote the industrialization of OLED and QLED displays through the inkjet printing process.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAcknowledgments\u003c/p\u003e\n\u003cp\u003eThis study was conducted with support from Ministry of Trade, Industry \u0026amp; Energy (MOTIE, No. 20010464). And This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. RS-2023-00222166). And this research was supported by \u0026quot;Regional Innovation Strategy (RIS)\u0026quot; through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (MOE)(2021RIS-003).\u003c/p\u003e\n\n\u003cp\u003eAuthor contributions\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDong Yeol Shin\u003c/strong\u003e\u003cstrong\u003e:\u003c/strong\u003e Writing- original draft, Formal analysis.\u0026nbsp;\u003cstrong\u003eJaebum Jeong:\u0026nbsp;\u003c/strong\u003eediting.\u003cstrong\u003e\u0026nbsp;Woo Jin Jeong:\u0026nbsp;\u003c/strong\u003edata curation\u003cstrong\u003e. Seok Hwan Jang\u003c/strong\u003e: data curation,\u003cstrong\u003e\u0026nbsp;Sung Wook Kang:\u0026nbsp;\u003c/strong\u003eResource.\u003cstrong\u003e\u0026nbsp;Kyung-Tae Kang:\u003c/strong\u003e Formal analysis. \u003cstrong\u003eJun Young Kim:\u003c/strong\u003e Writing-review \u0026amp; editing, Writing-original draft, Resources, Formal analysis, Conceptualization.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eDeclaration of interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflict of interest.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eDeclaration of generative AI in scientific writing\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis manuscript has been prepared without the use of generative AI technologies.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eAvailability of Data and Materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\n\u003cp\u003eAUTHOR INFORMATION\u003c/p\u003e\n\u003cp\u003eCorresponding Author\u003c/p\u003e\n\u003cp\u003e*[email protected] (Jun Young Kim)\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eZheng, X.; Liu, Y.; Zhu, Y.; Ma, F.; Feng, C.; Yu, Y.; Hu. 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DOI: 10.1016/j.fuel.2021.120307\u003c/li\u003e\n\u003cli\u003eMicrofab Technologies, Inc. MJ-AT User\u0026apos;s manual\u003c/li\u003e\n\u003cli\u003eTadros, T. F. Encyclopedia of colloid and interface science. \u003cem\u003eSpringer reference\u003c/em\u003e, \u003cstrong\u003e2013\u003c/strong\u003e, 1020-1042.\u003c/li\u003e\n\u003cli\u003eWei, H.; Xiao, X.; Yin, Z.; Yi, M.; Zou, H. A waveform design method for high DPI piezoelectric inkjet print-head based on numerical simulation. \u003cem\u003eMicrosyst. Technol.\u003c/em\u003e\u003cstrong\u003e2017\u003c/strong\u003e, \u003cem\u003e23\u003c/em\u003e, 5365-5373.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"inkjet printer, Ansys Fluent, Ansys Mechanical, ink droplet, inkjet simulation, fluid structural interaction","lastPublishedDoi":"10.21203/rs.3.rs-5264271/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5264271/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAs inkjet printers have recently been used to manufacture organic/quantum dot light-emitting diode displays, stable ink drops and control have become important during the printing process. This paper proposes a combination simulation of Ansys Fluent and Ansys Mechanical to find the conditions of stable ink droplets. To confirm the feasibility of the simulation, a jetting simulation of Newtonian fluids with practically constant viscosity was performed, and the results were compared with experimental results. Next, we performed a simulation of commercial non-Newtonian ink whose viscosity changed with a change in shear rate and compared the results with the experimental results. The experimental and simulation outcomes differed under the same voltage conditions. The study findings show that inkjet simulation can be employed not only to find stable drop conditions but also to observe changes in pressure in the inkjet nozzle.\u003c/p\u003e","manuscriptTitle":"Simulation of Piezoelectric Inkjet Printing Using Fluid Structural Interaction","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-10-30 09:07:43","doi":"10.21203/rs.3.rs-5264271/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"2ab25f08-fc96-4953-996f-9dce55091f6b","owner":[],"postedDate":"October 30th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-02-12T15:54:08+00:00","versionOfRecord":[],"versionCreatedAt":"2024-10-30 09:07:43","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5264271","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5264271","identity":"rs-5264271","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}