阅读说明：本技术 基于微流控系统层流特性的电子墨水屏全彩显示装置 (Full-color display device of electron ink screen based on micro-fluidic system laminar flow characteristic ) 是由 秦晓飞 李�浩 张学典 于 2021-01-07 设计创作，主要内容包括：本发明涉及一种基于微流控系统层流特性的电子墨水屏全彩显示装置,将带正电荷的四色墨水(CMYK)分别与等比例不带电荷的白色墨水混合,再分装到四个微墨水泵中,四个微泵分别接入由PMMA制成的微通道,四个显像腔中每个显像腔通过各自的单向阀、微通道与微墨水泵站中的对应的一种混色墨水泵站的闭环连接,每个微通道内有不断流动的液体介质。该装置将一段CMYK四通道合并为一个像素点,使用电极控制各点颜色变化。利用微流控系统层流现象实现全彩显示。在成像的过程中可近乎完全复现出图像的真实颜色；简化了彩显过程中颜色调配的过程,极大地缩减了刷新时间；简化实现过程中所需的硬件设计和结构,减少工艺步骤,降低成本。(The invention relates to an electronic ink screen full-color display device based on the laminar flow characteristic of a microfluidic system, which is characterized in that four colors of ink (CMYK) with positive charges are respectively mixed with white ink without charges in equal proportion and then are respectively loaded into four micro ink pumps, the four micro pumps are respectively connected into micro channels made of PMMA, each developing cavity in the four developing cavities is connected with a closed loop of a corresponding color mixing ink pump station in a micro ink pump station through a respective one-way valve and the micro channel, and a liquid medium which flows continuously is arranged in each micro channel. The device combines one section of CMYK four channels into one pixel point, and the color change of each point is controlled by using an electrode. And full-color display is realized by utilizing the laminar flow phenomenon of the microfluidic system. The real color of the image can be almost completely reproduced in the imaging process; the color blending process in the color display process is simplified, and the refreshing time is greatly shortened; the hardware design and structure required in the implementation process are simplified, the process steps are reduced, and the cost is reduced.)

1. An electronic ink screen full-color display device based on the laminar flow characteristic of a microfluidic system is characterized by comprising a substrate, a micro-ink pump station, a one-way valve, a microchannel, a development cavity and an electrode; the two transparent substrates are oppositely arranged, four development cavities which are made of PMMA are arranged between the two substrates side by side, and each development cavity in the four development cavities is connected with a closed loop of a corresponding color mixing ink pump station in a micro ink pump station through a respective one-way valve and a micro channel; the micro ink pump station comprises a black and white mixed ink pump station, a yellow and white mixed ink pump station, a carmine and white mixed ink pump station and a cyan and white mixed ink pump station, wherein each mixed ink pump station is filled with colored particles with positive charges and uncharged white particles; the four imaging cavity equal division sections correspond to all pixel points in a row, namely each pixel point comprises one section of the four imaging cavities, and each section of the imaging cavity is provided with a group of cathode and anode electrodes; the micro ink pump station provides particle ink to the developing cavity through the one-way valve, the particle ink generates laminar flow in the micro channel under the condition that the Reynolds number is far less than 3000, and colored particle electrons are adsorbed to present required colors when the particle ink flows through the electrifying electrode between the substrate and the developing cavity.

2. The full-color display device of the electronic ink screen based on the laminar flow characteristic of the microfluidic system according to claim 1, wherein the micro channel and the image display chamber are both circular cross-section pipes, the diameter of the pipe of the image display chamber is slightly larger than that of the micro channel, and under the condition of no power supply, the colored particles and the white particles both flow in a laminar flow state in the whole process of flowing the closed-loop medium, i.e. the white ink particle beam flows on the upper layer of the fluid medium, and the colored ink particle beam flows on the lower layer of the fluid medium.

3. The full-color display device of the electronic ink screen based on the laminar flow characteristic of the microfluidic system according to claim 1 or 2, wherein each color mixing ink pump station is provided with two ink filling ports, one is a color ink filling port and corresponds to a color ink area filled in the pump station, the other is a white ink filling port and corresponds to a white ink area filled in the pump station, an output micro-tube of each color mixing ink pump station is Y-shaped, the upper micro-tube and the lower micro-tube are combined into a micro-tube, the upper micro-tube is communicated with the white ink area, and the lower micro-tube is communicated with the color ink area; three branch pipes are led out from the lower part of the input end microchannel of the mixed ink pump station and are communicated with the colored ink area of the mixed ink pump station, an electrode which can be electrified to adsorb colored particle ink is arranged on the outer pipe wall of the microchannel in front of the inlet of each branch pipe, and a color sensor is arranged on the outer pipe wall of each branch pipe.

4. The full-color display device of the electronic ink screen based on the laminar flow characteristic of the microfluidic system according to claim 3, wherein the particle size of the white ink particles and the colored ink particles is 1-100 μm.

5. The full-color display device of the electronic ink screen based on the laminar flow characteristic of the microfluidic system according to claim 3, wherein the input side micro-channel and the output side micro-channel of each micro-ink pump station have two check valves, and the check valves control the flow direction of the liquid medium to prevent the backflow of the liquid medium, so that the colored particles in the developing chamber are insufficient.

6. The full-color display device of the electronic ink screen based on the laminar flow characteristic of the microfluidic system according to claim 3, wherein the color sensor collects color signals and sends the color signals to the control unit as feedback adjustment signals, and the control unit outputs control signals to adjust the voltage of the corresponding electrode and regulate the layered flow of the colored ink particles from the branch pipe into the colored ink area.

Technical Field

The invention relates to a display technology, in particular to an electronic ink screen full-color display device based on the laminar flow characteristic of a microfluidic system.

Background

Electronic ink is a new material generated by combining chemistry, physics and electronics. There are millions of microcapsules of about 10 microns in size in an electronic ink liquid. The microcapsule is a colloidal material after being prepared. This material is a fine solid particle that assumes the physical properties of a liquid. The microcapsules are suspended in a liquid medium and are capable of adhering to any surface to which conventional inks may be applied.

Compared with the traditional display screen, the electronic ink screen has the following advantages: (1) the optical fiber is light, thin and portable, and has high resolution; (2) the bistable display has strong endurance, and when the external voltage is removed, the pigment still remains on the electrode; (3) the image content display is that natural light enters human eyes after being reflected by a screen, and the visual angle is wider during reading; (4) the advantages of traditional paper printing and the characteristic of electronic display of repeated erasing are organically combined together, so that the paper has the visual effect of traditional paper and the characteristic that an electronic display screen flexibly changes text images, and the reading comfort level is greatly improved while the paper accords with the human visual physiological habit; (5) the damage to human body radiation and eyes is greatly reduced. Electronic paper is therefore a necessary trend for the intelligent application of handheld reading devices.

The existing technologies include: the reflectivity of the electrophoretic electronic paper is about 40%; the reflectivity of the electrowetting electronic paper is more than 40 percent; cholesteric liquid crystal bistable electronic paper, the reflectivity is about 50%; the reflectivity of the electrochromic electronic paper is about 3%; the reflectivity of the micro-electro-mechanical interference electronic paper is about 25%; the reflectivity of the powder fluid type electronic paper is more than or equal to 40 percent. Among them, the mainstream design schemes of electronic paper are electrophoretic electronic paper and electrowetting electronic paper.

In order to realize the color display of the electronic ink screen, the electrophoretic electronic paper display is used as a novel display technology and has wide viewing angle; the ultra-low energy consumption and paper-like display have the advantages that the innovation capability of the ultra-low energy consumption and paper-like display have certain influence on the development of the flat panel display industry in China. Some companies propose a display control method for electrophoretic electronic paper displays (patent publication No. CN108615506B), which ultimately achieves the results of eliminating flicker generated during image updating, reducing afterimage generated after image refreshing, and improving gray scale value, but is not good enough in full-color display. In addition, the design of the driving waveform is still a troublesome problem for the electrophoretic electronic paper, because the length of the driving waveform determines the image update time during the image update process, and the improper driving waveform seriously affects the image refresh rate.

Compared with electrophoresis type electronic paper, the electrowetting type electronic paper has a simple structure; the advantages of simple and convenient processing technology and easy driving, which gradually develops into a hot research object. Some companies have proposed a method of using three electrowetting display layers stacked one on top of the other to solve this problem (patent publication No. CN 107167916B). According to the scheme, colors are sequentially displayed by CMY three colors in an overlapping mode, color display is achieved to a certain extent, but the problem of full-color display is not well solved, because the method completely depends on three-color matching to achieve full color, the problem of color difference caused by impure primary color pigments can occur, and the processing cost is increased by the multi-layer color overlapping display method.

Disclosure of Invention

The invention provides an electronic ink screen full-color display device based on the laminar flow characteristic of a microfluidic system, aiming at the problems of full-color display of electronic ink. The method solves the technical problem that the refresh rate is too slow due to complicated color matching process in the existing full-color display method, and the color problem that the primary colors of the image cannot be perfectly reproduced due to incomplete primary color pigments.

The technical scheme of the invention is as follows: the full-color display device of the electronic ink screen based on the laminar flow characteristic of the microfluidic system comprises a substrate, a micro-ink pump station, a one-way valve, a microchannel, a development cavity and an electrode; the two transparent substrates are oppositely arranged, four development cavities which are made of PMMA are arranged between the two substrates side by side, and each development cavity in the four development cavities is connected with a closed loop of a corresponding color mixing ink pump station in a micro ink pump station through a respective one-way valve and a micro channel; the micro ink pump station comprises a black and white mixed ink pump station, a yellow and white mixed ink pump station, a carmine and white mixed ink pump station and a cyan and white mixed ink pump station, wherein each mixed ink pump station is filled with colored particles with positive charges and uncharged white particles; the four imaging cavity equal division sections correspond to all pixel points in a row, namely each pixel point comprises one section of the four imaging cavities, and each section of the imaging cavity is provided with a group of cathode and anode electrodes; the micro ink pump station provides particle ink to the developing cavity through the one-way valve, the particle ink generates laminar flow in the micro channel under the condition that the Reynolds number is far less than 3000, and colored particle electrons are adsorbed to present required colors when the particle ink flows through the electrifying electrode between the substrate and the developing cavity. .

Preferably: the microchannel and the imaging cavity are both circular-section pipelines, the diameter of the pipeline of the imaging cavity is slightly larger than that of the microchannel, and under the condition of no electricity, the colored particles and the white particles flow in a laminar flow state in the whole process of flowing of the closed-loop medium, namely, the white ink particle beams flow on the upper layer of the fluid medium, and the colored ink particle beams flow on the lower layer of the fluid medium.

Preferably: each mixed color ink pump station is provided with two ink filling ports, one is a colored ink filling port and corresponds to a colored ink area filled into the pump station, the other is a white ink filling port and corresponds to a white ink area filled into the pump station, an output micro-pipe of each mixed color ink pump station is Y-shaped, an upper micro-pipe and a lower micro-pipe are combined into a micro-pipe, the upper micro-pipe is communicated with the white ink area, and the lower micro-pipe is communicated with the colored ink area; three branch pipes are led out from the lower part of the input end microchannel of the mixed ink pump station and are communicated with the colored ink area of the mixed ink pump station, an electrode which can be electrified to adsorb colored particle ink is arranged on the outer pipe wall of the microchannel in front of the inlet of each branch pipe, and a color sensor is arranged on the outer pipe wall of each branch pipe.

Preferably: the particle size of the white ink particles and the particle size of the colored ink particles are 1-100 micrometers.

Preferably: the input side micro-channel and the output side micro-channel of each micro-ink pump station are provided with two one-way valves, and the one-way valves control the flow direction of the liquid medium to prevent the backflow of the liquid medium, so that the colored particles in the developing cavity are insufficient. By adopting the technical scheme: .

Preferably: the color sensor collects color signals and sends the color signals to the control unit as feedback adjusting signals, the control unit outputs control signals to adjust the voltage of the corresponding electrode, and colored ink particles are regulated and controlled to flow into a colored ink area from the branch pipe in a layered mode.

The invention has the beneficial effects that: the full-color display device of the electronic ink screen based on the laminar flow characteristic of the microfluidic system can almost completely reproduce the real color of an image in the imaging process; the color blending process in the color display process is simplified, and the refreshing time is greatly shortened; the hardware design and structure required in the implementation process are simplified, the process steps are reduced, and the cost is reduced.

Drawings

FIG. 1 is a schematic view of the whole structure of an electronic ink screen full-color display device based on the laminar flow characteristic of a microfluidic system according to the present invention;

FIG. 2 is a schematic view of a development chamber of the apparatus of the present invention;

FIG. 3 is a schematic diagram of a full color printing process of four colors CMYK mixed white (W) used in the present invention;

FIG. 4 is a schematic diagram of a color blending process required for displaying a certain pixel point according to the present invention;

FIG. 5 is a schematic view of the input/output module of the micro ink pump station according to the present invention.

Reference numerals: 1. a micro ink pump station; 101. an ink filling port; 2. a one-way valve; 3. a microchannel; 4. a visualization chamber; 5. a screen; 501. pixel points; 6. an upper substrate; 7. a cathode plate; 8. a baffle plate; 9. a gasket; 10. an anode plate; 11. a lower substrate; 12. an insulating washer; 13. positively charged (C/M/Y/K) particles; 14. uncharged white (W) particles; 15. electrodes (particle sieving); 16. a branch pipe; 17. a color sensor.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

As shown in fig. 1, the schematic diagram of the overall structure of the electronic ink screen based on the laminar flow characteristic of the microfluidic system includes a micro ink pump station 1, a one-way valve 2, a microchannel 3, a development chamber 4, and a screen 5. Wherein each micro ink pump station 1 consists of four mixed ink pump stations of black and white mixed ink pump stations K & W, yellow and white mixed ink pump stations Y & W, magenta and white mixed ink pump stations M & W and cyan and white mixed ink pump stations C & W. Every pixel point of screen 5 same row shares four colour mixture ink pump station four visualization chambeies 4 of arranging from top to bottom that connect, and every visualization chamber 4 of same row pixel point passes through check valve 2, microchannel 3 and the closed loop connection of a colour mixture ink pump station. For example, as shown in fig. 1, one row is 5 pixels, 5 pixels correspond to the upper and lower 4 imaging chambers 4, and each imaging chamber 4 is connected to a color-mixed ink pump station.

As shown in a schematic diagram of the structure of a display chamber in the device of fig. 2, an upper substrate 6, a cathode plate 7, a baffle plate 8, a gasket 9, an anode plate 10, a lower substrate 11, an insulating gasket 12, positively charged (C/M/Y/K) particles 13, and uncharged white (W) particles 14.

As shown in fig. 1 and 2, a cathode plate 7 and an anode plate 10 are respectively arranged above and below different pixel points of the same developing chamber 4, each pixel point of the same developing chamber 4 (the same row is 5 pixel points in the figure) is taken as a group, all cathode plates 7 of the same group are arranged between the same developing chamber 4 and the upper substrate 6, all anode plates 10 of the same group are arranged between the same developing chamber 4 and the lower substrate 11, insulating gaskets 9 are arranged on two sides of the developing chamber 4, the cathode plates 7 and the anode plates 10 are isolated from the outside, and the upper substrate 6, the lower substrate 11 and the gaskets 9 are pressed by baffle plates 8 on two sides of the developing chamber 4. All the cathode plates of different pixel points of the same developing chamber 4 are directly connected with the cathode of the power supply, and all the anode plates of different pixel points of the same developing chamber 4 are connected with the anode of the power supply through respective driving tubes. The positively charged (C/M/Y/K) particles 13 and the uncharged white (W) particles 14 in the imaging chamber 4 are sequentially aligned for color development by electrical control.

Because the laminar flow characteristics of microfluidic systems occur when conditions are met, i.e., reynolds numbers (Re) much less than 3000, and Re ═ ρ vd/μ, where v is the flow rate of the liquid; ρ is the liquid density; d is the characteristic length; μ is the fluid viscosity. It should be noted that the characteristic length d, the micro-channel 3 and the imaging cavity 4 used in the present invention are both circular cross-section tubes, and the diameter of the tube of the imaging cavity 4 is slightly larger than the diameter of the micro-channel 3, so the advantage of the design is that the imaging cavity will adsorb and retain a part of the colored charged particles 13 to realize color display, and the local charged particle accumulation and the continuous circulation flow of the liquid medium may interfere with each other, so the diameter of the imaging cavity 4 will be slightly larger, but if the diameter of the imaging cavity can satisfy the laminar flow condition, the same diameter size of the micro-channel 3 can also satisfy the laminar flow condition. The particle size of the white ink particles and the CMYK ink particles is 1-100 micrometers.

When the liquid condition and the hardware condition in the system meet the condition of the laminar flow phenomenon, the white ink particle beams flow on the upper layer of the fluid medium after the mixed color ink flows out of the micropump, the colored ink particle beams flow on the lower layer of the fluid medium, and the colored particles and the white particles can keep the moving state in the whole medium flowing process under the condition of no electricity.

As shown in fig. 1 and 3, the imaging chamber 4 is connected to each of the micro ink pump stations: the black-white mixed ink pump stations K & W contain positively charged (K) particles and uncharged white (W) particles, the yellow-white mixed ink pump stations Y & W contain positively charged (Y) particles and uncharged white (W) particles, the magenta-white mixed ink pump stations M & W contain positively charged (M) particles and uncharged white (W) particles, and the cyan-white mixed ink pump stations C & W contain positively charged (C) particles and uncharged white (W) particles. Then, the micro ink pump station is connected with the developing cavity through the micro channel 3 and two sets of one-way valves of input and output, colorless liquid can flow in the whole channel to be used as a medium for the movement of colored positive charge particles and white non-charge particles, and the liquid medium can flow clockwise along the channel in the whole channel according to a certain flow rate through the matching use of the micro pump and the one-way valves.

As shown in fig. 2 and 4, when the liquid in the micro channel 3 flows into the image development chamber in a laminar flow state, carrying the uncharged white particle beam and the charged colored particle beam, the cathodes located between the upper substrate 6 and the image development chamber 4 will display the required color by adsorbing the corresponding positively charged colored ink particles according to the image color requirement of each pixel. The importance of mixing white ink particles and colored ink particles is highlighted here, when a certain pixel point does not need to display other colors except white, namely the cathode does not adsorb colored charged particles, the white ink normally flows through the plate, and white is displayed on the screen, if a certain pixel point needs a certain special color which may be a result of mixing cyan (C), magenta (M), yellow (Y), black (K) and white (W) according to different proportions, at the moment, the cathode still adsorbs the colored ink particles according to the required colored particle amount, but the whole upper layer liquid medium is not filled with a certain color, a small amount of colored particles adsorbed by the electrode can be mixed with the white particle beams to form the required color proportion. All the pixel points are the same implementation method.

After the first supply of ink particles is finished, the redundant mixed ink particles are circulated back to the micro-pump station along with the organic liquid medium, and are separated and stored for the next supply of ink particles. Since the colored particles 13 and the white particles 14 in the micro channel 3 are always kept "mixed", i.e. the upper layer of the circulating liquid medium contains white particles and the lower layer of the liquid medium contains colored particles, the solution of the present invention is to achieve different particle flows back to the respective corresponding areas in the micro pump: as shown in fig. 5, each color mixture ink pump station has two ink filling ports 101, one is a color ink filling port (C/M/Y/K) corresponding to a color ink area filled into the pump station, and the other is a white ink filling port (W) corresponding to a white ink area filled into the pump station, an output micro-tube of each color mixture ink pump station is Y-shaped, an upper micro-tube and a lower micro-tube are combined into a micro-tube, the upper micro-tube is communicated with the white ink area, and the lower tube is communicated with the color ink area; three branch pipes 16 are led out from the lower part of the input end microchannel of the mixed ink pump station and are led into the mixed ink pump station, an electrode 15 is arranged on the outer pipe wall of the microchannel in front of the inlet of each branch pipe, and a color sensor 17 is arranged on the outer pipe wall of each branch pipe. The implementation process is as follows: since the white particles are uncharged and will not be disturbed by the electric field, and will still flow in the same direction as the liquid medium, the positively charged colored ink particles will deviate from the original flow path due to the attraction of the cathode plate, and then under a suitable voltage, the colored ink particles can enter the branch pipe 16. The color sensor 17 arranged on the branch pipe wall can prevent the colored ink particles from flowing into the branch pipe all too early, so that the white ink particles also flow into the branch pipe behind the color sensor, or the colored ink particles are not separated completely, the color sensor can monitor the inflow amount of the colored particles in each branch pipe 16 along with the white ink particle beam entering the white ink pool, and the voltage applied to the electrode is changed through feedback regulation, so that all the colored particles are sucked into the branch pipe when the colored particle beam flows through the last branch pipe opening, and the color pollution of the ink particles is not caused to the maximum extent.

Selecting and matching pigments: in order to better reproduce the due colors in the image, the invention adopts four-color printing ink: cyan (C), magenta (M), yellow (Y) and black (K) plus white (W) inks, CMYK inks containing positively charged colored particles and W ink containing uncharged white particles. The method does not use the primary colors CMY to prepare black, mainly aiming at preventing that the real black cannot be prepared under the condition that the primary colors CMY are impure. After the primary color ink is determined, a certain amount of white ink particles and equal proportion of colored ink particles are mixed, and the mixed color ink is subpackaged into all the micro ink pumps.

The mixing of CMYK ink and W ink in the invention means that CMYK and W are respectively mixed and loaded in the same micro-ink pump station, but the inside of the pump station is divided into two sub-areas which are respectively loaded with CMYK ink and white ink, and the detailed description is shown in a schematic diagram 5.

Preparation of the microchannel and the imaging cavity: the microchannel and the imaging chamber are both made of polymethyl methacrylate (PMMA) because the density of PMMA is about 1.15-1.19g/cm³The glass is half of glass, the tensile resistance and the impact resistance are 7-18 times of those of common glass, and the light transmittance of PMMA is as high as 92% and is higher than that of glass. Based on the advantages of PMMA, the invention uses PMMA to manufacture the micro-channel and the imaging cavity. The developing cavity is a cylindrical cavity arranged between the upper substrate and the lower substrate, and the color gamut formed when the ink particles stay in the developing cavity can be developed on a screen through the substrate. Because the colors of all pixel points are different, in order to enable equivalent colored ink particles to be retained at the position of an appointed cavity wall to meet the color development requirement of all the pixel points, four developing cavities with different color mixtures are regarded as a group, a plurality of electrodes (cathodes) are distributed at the contact part of each group of developing cavities and an upper substrate along the cavity wall, four cathodes corresponding to the developing cavities with different colors form a pixel point, each group of developing cavities are provided with electrodes with the same number as the required pixel points along the outer wall of the cavity, each group of developing cavities transversely and inertially penetrate through a screen, and the screen is longitudinally provided with a plurality of groups of developing cavities according to the requirement, so that the number of the pixel points can meet the.

Supply and circulation of ink: a micro-channel made of PMMA (polymethyl methacrylate) is used for connecting a micro-ink pump station (micro-pump for short) and a developing cavity, and an organic solvent is circulated in the micro-channel to be used as a liquid medium for transporting CMYK (CMYK) and white (W) ink particles. All be equipped with the check valve at the input and the output of every micropump, the design objective is: the liquid medium is ensured to flow circularly along the micro-channel in the clockwise direction all the time, and liquid backflow is avoided, so that sufficient ink particle supply in the developing cavity is ensured.

After the first supply of ink particles is finished, the redundant mixed ink particles are circulated back to the micro-pump station along with the organic liquid medium, and are separated and stored for the next supply of ink particles. Because the colored particles and white particles in the micro-channel are always kept to be mixed, namely the upper layer of the circulating liquid medium contains the white particles and the lower layer of the liquid medium contains the colored particles, in order to realize that different particles flow back to the corresponding areas in the micro-pump, the solution of the invention is as follows: three branch pipes are led out from the micro-channel at the input end of the micro-pump, an electrode is arranged on the outer pipe wall of the micro-channel in front of the inlet of each branch pipe, and a color sensor is arranged on the outer pipe wall of each branch pipe. The reason and meaning of the design are as follows: the white particles are not electrified and can not be disturbed by an electric field and still flow along with the liquid medium, and the colored ink particles with positive charges can deviate from the original flow track due to the attraction of the cathode plate, so that the colored ink particles can enter the branch pipe under a proper voltage. The color sensor is arranged on the wall of the branch pipe to prevent colored ink particles from flowing into the branch pipe all too early, so that white ink particles also flow into the branch pipe behind the color sensor, or the colored ink particles are not separated completely, the inflow amount of the colored particles in each branch pipe can be monitored by the color sensor along with the white ink particle beams entering the white ink pool, the voltage applied to the electrode is changed through feedback adjustment, all colored particles are sucked into the branch pipe when the colored particle beams flow through the last branch pipe opening, and color pollution of the ink particles is avoided to the maximum extent.

And full-color display is realized by utilizing laminar flow characteristics: after the microchannel is arranged, appropriate ink is filled, the flow rate of mixed liquid in the microchannel is controlled through a valve, so that the whole system meets the Reynolds number condition (Re is rho vd/mu is far less than 3000), and the laminar flow phenomenon can occur. Wherein v is the flow rate of the liquid; ρ is the liquid density; d is the characteristic length; μ is the fluid viscosity. The channels involved in the invention are all the channels with circular sections, so d refers to the diameter of the channel, and the diameter of the developing cavity is slightly larger than that of the microchannel, so when the developing cavity meets the laminar flow condition, the laminar flow condition is necessarily met in the microchannel. When the laminar flow phenomenon occurs, the white ink and the colored ink generate obvious laminar flow phenomenon, namely the white ink flows in the upper layer of the fluid in the channel, the colored ink flows in the lower layer of the fluid in the channel, and when the fluid keeps the state and flows through the inside of the developing cavity, the white ink particles are uncharged, so that the white ink particles can still keep flowing in the original direction on the upper layer of the liquid when passing through an electric field. However, the colored ink particles on the lower layer are positively charged, the top of the developing cavity is provided with an electrode (cathode), and when the colored particles flow through the lower part of the cathode, the cathode can adsorb the colored ink particles according to the amount of the colored ink particles required by the pixel point. Although the white ink particles are on the upper layer of the fluid, gaps exist among the ink particles, so that the colored ink particles can completely penetrate through the white ink particle layer to reach the lower part of the cathode. Problems that may exist after the colored ink particles are adsorbed are: because the upper layer liquid medium in the channel is mixed with white ink particles to flow continuously, the colored ink particles have certain probability to be washed away by the white particle beams. The solution here is: the colored particle beams on the lower layer continuously flow through the development cavity in the medium moving process, so that some colored particles are still relative to the development cavity in the development cavity, and the colored ink particles can fill the particle vacancies flushed away by the medium in real time.

The target application scenario of the invention is as follows: (1) the movable site display board (2), the shop product/movable billboard (3), the roadside billboard (4) and the station information board. The invention can be expected to be applied to the electronic reader under the condition that the processing technology meets.

The foregoing illustrates and describes the principles, essential features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.