EWD-based three-dimensional simulation modeling expanded waveform verification method

Abstract

The invention provides an extended waveform verification method based on EWD three-dimensional simulation modeling. The method comprises the following steps: setting a common fluid field and an electrostatic field in a simulation model, simulating the fluid field by using a laminar flow field and a phase field method, carrying out geometric modeling by adopting EWD of rectangular pixel units, and jointly establishing an EWD pixel unit simulation model; setting dielectric constants of the solid photoresist and the hydrophobic insulating layer, and setting dynamic viscosity, dielectric constants and surface tension coefficients of fluid ink and water; the method comprises the following steps: describing fluid stress by using a Navier Stokes equation set in fluid mechanics, describing an electric field force received by a fluid by using a Maxwell stress tensor in an electric field, and adding the electric field force as a volume force into the Navier Stokes equation set; and setting a wetting wall and an entrance and exit boundary in the fluid field, and grounding and a potential boundary in the electrostatic field, and generating a one-dimensional, two-dimensional or three-dimensional drawing group through mesh generation and model solution. The simulation model is well matched with an actual result, and the EWD three-dimensional simulation model can expand waveform verification means.

Description

Technical Field

[0001] The present invention relates to the technical field of color ink simulation, and in particular to an extended waveform verification method based on EWD three-dimensional simulation modeling. Background Art

[0002] As a cutting-edge liquid manipulation technology, the core of the electrowetting theory is to use the power of electric fields to accurately guide and control the behavior of liquids. This technology can dynamically change the contact angle between the liquid and the solid interface by cleverly applying an electric field on the surface of the dielectric material, thereby driving the liquid to perform a series of complex and delicate operations such as directional flow, morphological changes, and even splitting according to a predetermined pattern. The discovery of this principle can be traced back to 1981, marking a new era in which humans began to explore the interaction between electric fields and liquids. After 22 years of technological accumulation and innovation, Robert A. Hayes finally turned this theory into reality and successfully developed high-quality electrowetting display technology (EWD), bringing a revolutionary breakthrough to the display field.

[0003] Compared with traditional electronic paper display technology (EPD), EWD display technology has shown unparalleled application potential with its superior response speed - reaching milliseconds, rich color expression and high reflectivity. However, the implementation of EWD technology is not smooth sailing, especially in the key link of ink splitting, the voltage selection of DC drive scheme is particularly important. The precise control of voltage is directly related to the uniformity, stability and efficiency of ink splitting, and is the key to ensuring the display effect.

[0004] Although EWD technology has broad prospects, the current research on its three-dimensional simulation model is still in its infancy and faces many challenges. On the one hand, the accuracy of existing models is limited, and it is difficult to accurately capture the subtle changes in the ink splitting process, which leads to problems such as non-convergence and fluid mass loss in the calculation results; on the other hand, due to the high requirements for calculation accuracy, the simulation process is often time-consuming, which seriously restricts scientific research progress and practical applications. In addition, there is a relative lack of intuitive simulation research on the ink splitting phenomenon in EWD, and there is a lack of an effective means to clearly display the distribution changes during fluid movement.

[0005] In view of this, the present invention is committed to expanding the application of EWD three-dimensional model in verifying the motion characteristics of oil film. By deeply exploring the intrinsic relationship between different driving schemes and ink splitting phenomenon, the present invention can not only effectively expand the verification means of driving schemes, provide more comprehensive and accurate simulation model support for scientific researchers, but also lay a solid foundation for the further optimization and wide application of EWD technology. This innovative achievement will undoubtedly open up a new path for the future development of display technology and lead us to a new era of more intelligent, efficient and colorful display.

[0006] In addition, the present invention also uses intuitive simulation visualization tools to display the changes in fluid motion distribution during the ink splitting process, and presents key information such as the flow trajectory, velocity distribution, and contact angle changes of the liquid in real time, so that researchers can intuitively observe the microscopic process and dynamic characteristics of ink splitting. This not only helps to deeply understand the physical mechanism of ink splitting, but also provides strong support for optimizing the driving scheme and improving the display effect.

[0007] In the research of driving scheme, the present invention has deeply explored the influence of different voltage waveforms, frequencies and amplitudes on the ink splitting phenomenon through a large number of experiments and simulation analysis. By comparing and analyzing the simulation results and experimental data under different driving schemes, the present invention reveals the intrinsic relationship between the driving scheme and the ink splitting phenomenon, and provides a scientific basis for optimizing the driving scheme.

[0008] In summary, the present invention successfully expanded the application of EWD three-dimensional model in verifying the motion characteristics of ink through innovative model building methods, efficient computing technology and intuitive simulation visualization tools. This achievement not only provides more comprehensive and accurate simulation model support for scientific researchers, but also lays a solid foundation for the further optimization and wide application of EWD technology. In the future, with the continuous development and improvement of technology, EWD technology is expected to show broader application prospects in display technology, microfluidic systems, biomedical engineering and other fields. Summary of the invention

[0009] In response to the problems in the above-mentioned prior art, the present application proposes an expanded waveform verification method based on EWD three-dimensional simulation modeling, in which a common fluid field and an electrostatic field are set in the simulation model, laminar field and phase field method are used to simulate the fluid field, and EWD of rectangular pixel units is used for geometric modeling to jointly establish an EWD pixel unit simulation model; the dielectric constant of the solid photoresist and the hydrophobic insulating layer is set, and the dynamic viscosity, dielectric constant, and surface tension coefficient of the fluid ink and water are set; the Navier-Stokes equations are used in fluid mechanics to describe the force on the fluid, and the Maxwell stress tensor is required in the electric field to describe the electric field force on the fluid and add it as a volume force to the Navier-Stokes equations; the wetting walls, inlet and outlet boundaries in the fluid field, the grounding and potential boundaries in the electrostatic field are set, and a one-dimensional, two-dimensional, or three-dimensional drawing group is generated through meshing and model solving.

[0010] In one embodiment, at least two fluids and multiple solid films are included in the EWD.

[0011] In one embodiment, the geometric modeling is performed using EWD of square pixel units, and the ink is isotropic in the forces in different directions.

[0012] In one embodiment, the EWD is composed of multiple layers of stacked solid-liquid films; the outermost layer is ITO glass, and its lower side is coated with a hydrophobic insulating layer; the photoresist barrier forms the pixel wall, and the pixel wall is filled with ink; a layer of water film serves as an intermediate medium, and the ink can move within the pixel wall.

[0013] In one embodiment, in the simulation model, by changing the potential option in the electric field, a DC voltage of 10V to 15V is simulated to drive the ink movement in the simulation model, and the ink distribution is characterized by the fluid volume fraction field.

[0014] In one embodiment, a Cartesian coordinate system is established in the EWD pixel unit simulation model, and three-dimensional coordinate values ​​are used to describe the ink distribution position.

[0015] In one embodiment, an ink distribution coordinate database of different levels or scores is established so that different three-dimensional coordinate sets correspond to different EWD pixel unit performances, thereby evaluating the EWD pixel unit performances under different driving voltages.

[0016] The above technical features can be combined in various suitable ways or replaced by equivalent technical features as long as the purpose of the present invention can be achieved.

[0017] The invention provides an extended waveform verification method based on EWD three-dimensional simulation modeling, which has at least the following beneficial effects compared with the prior art:

[0018] Compared with directly testing the waveform through experiments, repeated experiments will cause physical loss and lead to inaccurate experimental results. The present invention uses a three-dimensional EWD model to simulate the movement of liquid in the pixel unit, providing guidance for the development of new driving schemes. At the same time, it can be intuitively observed that the ink splitting may be more serious with the increase of voltage after a long-term DC driving voltage. Figure 3 As shown in the figure, a DC voltage of different amplitudes lasting 20ms was added to the simulation model. It was found that in the actual test, as the voltage increased, the aperture ratio increased slightly, but the ink splitting became more serious, and even ink overflow occurred. The simulation model is consistent with the actual results. The three-dimensional simulation model of EWD can expand the waveform verification method. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be described in more detail below based on embodiments and with reference to the accompanying drawings, wherein:

[0020] Figure 1 The three-dimensional structure diagram of the ink simulation model of the present invention is shown;

[0021] Figure 2 A schematic diagram of the electric field distribution of the ink simulation model of the present invention is shown;

[0022] Figure 3 Schematic diagram showing the ink movement in the simulation model driven by DC voltages of different amplitudes. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings.

[0024] like Figure 1-2 As shown, the present invention provides a waveform verification method based on EWD three-dimensional simulation modeling expansion, sets a common fluid field and electrostatic field in the simulation model, uses laminar field and phase field method to simulate the fluid field, adopts EWD of rectangular pixel unit for geometric modeling, and jointly establishes EWD pixel unit simulation model; sets the dielectric constant of solid photoresist and hydrophobic insulating layer, sets the dynamic viscosity, dielectric constant, and surface tension coefficient of fluid ink and water; uses Navier-Stokes equations to describe the force on the fluid in fluid mechanics, and requires Maxwell stress tensor in the electric field to describe the electric field force on the fluid and add it as volume force to the Navier-Stokes equations; sets the wetting wall, inlet and outlet boundaries in the fluid field, and the grounding and potential boundaries in the electrostatic field, and generates a one-dimensional, two-dimensional, or three-dimensional drawing group through meshing and model solving.

[0025] In one embodiment, an EWD pixel unit simulation model is established to simulate the movement of color ink in the pixel unit, and its movement provides guidance for the development of new driving schemes. In the EWD pixel unit, the color ink can be approximately considered to be an incompressible, non-permeable, non-chemically reactive, Newtonian two-phase flow model. Using partial differential equations (PDE) to construct the color ink model is the optimal solution. The model can be characterized by mass and momentum balance, and the balance is expressed by the Navier-Stokes equation and the continuity equation formula:

[0026]

[0027] F=F st +ρg+F vf

[0028] Where, equation 1 is the continuity equation, ρ is the fluid density and u is the fluid velocity, the right side of equation 2 represents the pressure, viscosity, and the resultant external force acting on the fluid, and the left side of equation 2 represents the inertial force. st is the surface tension, ρg is the gravity, F vf It is the volume force.

[0029] In EWD, electrostatic force is the main factor causing the change of color ink fluid. The electrostatic force is caused by the electric field gradient caused by the non-uniform electric field. For incompressible fluids, the stretching density can be approximately ignored, and the electrostatic volume force F is calculated by the divergence of the Maxwell stress tensor (MST), and the formula is:

[0030]

[0031] In the formula, Z ij is a tensor, and the formula of Maxwell stress tensor (MST) is:

[0032]

[0033] Where E is the electric field intensity, D is the electric flux density, I is the unit matrix, ε0 is the dielectric constant of free space, and ε r is the relative dielectric constant. In the three-dimensional simulation model, the matrix expression of the Maxwell stress tensor is:

[0034]

[0035] Combining the above expressions, the calculation formula for electrostatic volume force is:

[0036]

[0037] When the experimental results have large errors, the mesh mobility χ and the interface thickness control parameter ∈ can be modified. If the interface thickness control parameter value is too small, it may cause the value to fluctuate, and if the interface thickness control parameter value is too large, it may not be able to correctly capture the interface movement. The ideal ∈ value is half of the maximum mesh unit size; at the same time, the phase field model feature needs to define the mobility adjustment parameter. If the mesh mobility value is too small, it will lead to numerical instability, and if the value is too large, it will not be able to correctly capture the interface movement. Based on past experience, the initial estimate of the mobility adjustment parameter is:

[0038]

[0039] Where v max is the expected maximum velocity, and δ is the surface tension coefficient. It should be noted that the expected maximum velocity v in this formula max and surface tension coefficient δ are empirical parameters and need to be fine-tuned for different models.

[0040] In one embodiment, the simulation model building step includes:

[0041] Define the type of problem to be solved: For a problem that needs to be simulated, it is necessary to analyze the problem first; analyze the physical field, geometric model, and setting research required for the problem: In EWD, there are two fluids and multiple layers of solid films, and an external electric field is used as a driving means. Therefore, a common fluid field and electrostatic field setting are required in this simulation model. At the same time, the Reynolds number of the fluid during movement is low, so the laminar field and phase field method can be used to simulate the fluid field and jointly establish the EWD pixel unit simulation model.

[0042] Establish geometric model: Establish geometric model for the problem to be solved, or import various files such as CAD model: In the EWD of rectangular pixel unit, square pixels make the ink isotropic in each x and y direction, and the display effect is good. Therefore, for the three-dimensional ink splitting simulation model, the EWD of rectangular pixel unit is used for geometric modeling. If there is a new structure, this step can still be used.

[0043] Introduce material properties of the solution domain: For the selection of materials, you can add them directly from the material library of the software, and you can also add empty materials and set properties according to your needs: EWD is composed of multiple layers of stacked solid-liquid films. The outermost layer is ITO glass, and its lower side is coated with a hydrophobic insulating layer. The photoresist barrier produced by photolithography forms the pixel wall, and the pixel wall is filled with ink. A thin layer of water film serves as an intermediate medium to help the ink move in the pixel wall. When no driving voltage is applied, the EWD remains closed and the ink is spread flat in the pixel wall; when the appropriate voltage is applied, the EWD is turned on and the ink is pushed to a corner of the pixel. During the simulation process, the outermost ITO glass has little effect and can be ignored, and there is no need to set material properties. Solid photoresist and hydrophobic insulating layer need to set solid material properties such as dielectric constant according to actual conditions, and fluid ink and water need to set fluid material properties such as dynamic viscosity, dielectric constant, and surface tension coefficient according to actual conditions. Some properties of solid-liquid materials can use default material properties, which reduces some workload.

[0044] Define the control function: The control equations of some models have been given and do not need further improvement, but in order to improve the accuracy of the model, more control equations are needed for optimization and adjustment: In fluid mechanics, the Navier-Stokes equations are used to describe the forces on the fluid. In the electric field, the Maxwell stress tensor is needed to describe the electric field force on the fluid and add it as a volume force to the Navier-Stokes equations.

[0045] Set boundary conditions: In this step, you can set the selected physical field. The software can set parameters, variables, functions, etc. to achieve the setting of the physical field: set boundary conditions according to actual conditions, such as wetting walls, inlet and outlet boundaries and other conditions in the fluid field, grounding and potential boundaries and other conditions in the electrostatic field.

[0046] Plan mesh generation: Through the mesh generation algorithm, you can select the mesh shape and choose different domains to set meshes of different shapes to improve the accuracy of mesh generation. You can adjust the mesh parameters to achieve meshes of different refinement levels.

[0047] Solution model: In this step, you can choose different calculation models and iterative solutions to solve the problem, or you can directly use the original algorithm without making any further adjustments.

[0048] Post-processing and reporting results: This process can generate 1D, 2D, 3D drawing groups, or export reports to export the software setup process, results, etc. into pdf documents. Get response data through simulation results.

[0049] Error correction and model optimization: The reported errors and post-processing results are the core of guiding the next step of work. Improving model accuracy through different methods is the only purpose of establishing a simulation model.

[0050] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. A waveform verification method based on EWD three-dimensional simulation modeling, characterized in that: A common fluid field and an electrostatic field are set in the simulation model, the laminar flow field and the phase field method are used to simulate the fluid field, the EWD of rectangular pixel units is used for geometric modeling, and the EWD pixel unit simulation model is jointly established; Set the dielectric constant of the solid photoresist and the hydrophobic insulating layer, set the dynamic viscosity, dielectric constant, and surface tension coefficient of the fluid ink and water; use the Navier-Stokes equations to describe the forces on the fluid in fluid mechanics, and in the electric field, the Maxwell stress tensor is required to describe the electric field force on the fluid and add it to the Navier-Stokes equations as a volume force; set the wetting wall, inlet and outlet boundaries in the fluid field, and the ground and potential boundaries in the electrostatic field, and generate one-dimensional, two-dimensional, or three-dimensional drawing groups through meshing and model solving.

2. The method for expanding waveform verification based on EWD three-dimensional simulation modeling according to claim 1 is characterized in that: EWD includes at least two fluids and multiple solid films.

3. The method for expanding waveform verification based on EWD three-dimensional simulation modeling according to claim 1 is characterized in that: The geometric modeling is carried out using EWD with square pixel units, and the ink is isotropic in different directions.

4. The method for expanding waveform verification based on EWD three-dimensional simulation modeling according to claim 1 is characterized in that: EWD consists of multiple layers of stacked solid-liquid films; the outermost layer is ITO glass, with a hydrophobic insulating layer coated on the underside; a photoresist barrier forms the pixel wall, which is filled with ink; a layer of water film serves as an intermediate medium, and the ink can move within the pixel wall.

5. The method for expanding waveform verification based on EWD three-dimensional simulation modeling according to claim 1 is characterized in that: In the simulation model, by changing the potential option in the electric field, the DC voltage is used to drive the ink movement in the simulation model, and the ink distribution is characterized by the fluid volume fraction field.

6. The method for expanding waveform verification based on EWD three-dimensional simulation modeling according to claim 1 is characterized in that: A Cartesian coordinate system is established in the EWD pixel unit simulation model, and the ink distribution position is described using three-dimensional coordinate values.

7. The method for expanding waveform verification based on EWD three-dimensional simulation modeling according to claim 6 is characterized in that: An ink distribution coordinate database with different levels or scores is established so that different three-dimensional coordinate sets correspond to different EWD pixel unit performances, thereby evaluating the EWD pixel unit performance under different driving voltages.

Images