Three-dimensional light-assisted electrophoretic deposition additive manufacturing device and method with controllable electrode spacing

Abstract

The present invention relates to a three-dimensional photo-assisted electrophoresis deposition additive manufacturing device and method with controllable electrode spacing, belonging to the field of electrophoresis deposition in 3D printing technology. The reaction device and the syringe are respectively fixed on two channels of a medical syringe pump. The water inlet of the reaction device is connected to the syringe through a joint and the water inlet conduit, and the water outlet is connected to the water outlet conduit through a joint to divert the liquid to a waste liquid tank. The advantages are that by combining a microfluidic pump with photo-assisted electrophoresis deposition, it can achieve the supply of particle suspension, the real-time control of the electrode spacing with micron-level high precision, and the rapid replacement of the types of particle suspension, making the electric field strength between the electrodes more stable, improving the deposition precision and part performance, and enabling the manufacturing of complex three-dimensional parts.

Description

Technical Field

[0001] The present invention belongs to the field of electrophoretic deposition in 3D printing technology, and particularly relates to a three-dimensional light-assisted electrophoretic deposition additive manufacturing device and method with controllable electrode spacing. Background Art

[0002] 3D printing, also known as additive manufacturing, is a technology that constructs three-dimensional objects by layer-by-layer bonding and accumulation of materials such as metals, plastics, and resins based on digital model files. Electrophoretic deposition is a technology that applies an electric field to a suspension of charged particles to promote the directional movement of the particles and their aggregation and deposition on the electrodes. The electrophoretic deposition material powder has a small size and a wide range of applicable materials, and can be used to produce coatings, layered materials, etc. Photo-assisted electrophoretic deposition is a manufacturing method in which a light pattern irradiates a photoconductive material to generate a local electric field, causing the charged particle material in the suspension to move directionally in the electric field and deposit layer by layer, capable of achieving micro-size pattern deposition with an accuracy of about 10 μm and having the potential to form micro-size three-dimensional parts with arbitrary structures.

[0003] The electrode spacing of existing photo-assisted electrophoretic deposition devices is difficult to change. Therefore, as the deposition layer gradually thickens and the surface of the deposition layer gradually rises, the electric field strength increases, affecting the deposition accuracy; a stable suspension requires a low solid particle ratio, while three-dimensional electrophoretic deposition requires a continuous supply of a large number of particles; during the deposition process, the suspension needs to be replaced when depositing the support material, and existing devices do not provide a solution for quickly changing the type of suspension, making it difficult to achieve the deposition of complex three-dimensional structures. Summary of the Invention

[0004] The present invention provides a three-dimensional light-assisted electrophoretic deposition additive manufacturing device and method with controllable electrode spacing to solve the problems of affecting deposition accuracy and difficulty in achieving the deposition of complex three-dimensional structures existing in existing photo-assisted electrophoretic deposition devices.

[0005] The technical solution adopted by the present invention includes a projection device, a medical syringe pump, a syringe, a reaction device, an inlet water conduit, a connector, an outlet water conduit, and a waste liquid tank. Among them, the reaction device and the syringe are respectively fixed on two channels of the medical syringe pump. The inlet of the reaction device is connected to the inlet water conduit through the connector, and the syringe and the outlet are connected to the outlet water conduit through the connector to divert the liquid to the waste liquid tank.

[0006] The projection device of the present invention includes a 405 nm wavelength light source, a positioning block, and an internal hexagonal screw. The light source is connected to the positioning block by the screw, so that the center of the light source is directly opposite to the center position of the hydrogenated amorphous silicon layer of the cathode plate in the reaction device, and the light source should be able to focus a beam with a specific shape and micron-size resolution on the hydrogenated amorphous silicon layer.

[0007] The medical syringe pump described in the present invention should be able to be used in conjunction with a syringe, enabling the syringe piston assembly to move forward and backward with high precision, and achieving high-precision movement with a minimum liquid flow rate of 1 ml / h.

[0008] The syringe described in the present invention is composed of a barrel and a piston assembly, and should comply with the standard of "YY / T 0573.2-2018 Disposable Sterile Syringes - Part 2: Syringes for Power-Driven Syringe Pumps".

[0009] The reaction device described in the present invention includes a cylinder body, a base, a piston rod, a cathode plate, and an anode plate. The base is composed of an outer rubber layer and an inner insulating material. The base is bonded to the piston rod, and the central hole of the base is aligned with the central hole of the piston rod. The piston rod and the base are inserted into the cylinder body, so that the two side surfaces of the base are respectively aligned with the water inlet and outlet of the cylinder body.

[0010] The cathode plate described in the present invention includes a hydrogenated amorphous silicon layer, a metal wire, a glass plate, and an ITO layer. The ITO layer completely covers one side surface of the glass plate, and the hydrogenated amorphous silicon layer is deposited on the surface of the ITO layer. The size of the cathode plate is slightly larger than the square hole at the top of the cylinder body in the reaction device. The cathode plate is bonded to the cylinder body, so that the hydrogenated amorphous silicon layer completely covers the square hole at the top of the cylinder body. The metal wire is connected to the ITO layer, and the metal wire is used to connect the negative electrode of the power supply to the ITO layer.

[0011] The anode plate described in the present invention includes a platinum sheet and a metal wire. The size of the platinum sheet is slightly smaller than the square hole at the top of the cylinder body. The platinum sheet is pasted at the center position of the top of the insulating material of the base, so that it can just be inserted into the square hole at the top of the cylinder body. The metal wire is welded to the back of the platinum sheet and passes through the central hole of the base and the piston rod. The metal wire is used to connect to the positive electrode of the power supply.

[0012] An additive manufacturing method using a three-dimensional light-assisted electrophoresis deposition additive manufacturing device with controllable electrode spacing includes the following steps:

[0013] (1) Preparation of the electrophoresis particle suspension: The materials are surfactant, anhydrous ethanol, and nano metal powder.

[0014] (2) Setting of the light pattern: Use modeling software to construct a part model, slice and layer the model along the Z direction so that the thickness of each layer is sub-micron level, import the graphic information of each layer of the model into the control program of the projection light source, and the projection light source 1 sets the deposition light time for each layer to achieve automatic switching of the light pattern.

[0015] (3) Injection of electrophoretic particle suspension: Use a medical syringe pump to push the piston rod of the reaction device, adjust the distance between the anode plate and the cathode plate to 50 μm, then push the piston assembly of the syringe, inject the particle suspension at a relatively high flow rate, and discharge the air in the cylinder of the reaction device until there is no gas residue in the reaction device; during the part deposition process, use a medical syringe pump to control the syringe to continuously inject the electrophoretic particle suspension into the reaction device at a flow rate of 2 ml / h to ensure that the suspension concentration between the anode plate and the cathode plate in the reaction device meets the deposition requirements;

[0016] (4) Deposition of three-dimensional micro-scale parts: Connect the anode plate and the cathode plate to the DC power supply respectively, turn on the DC power supply, turn on the projection light source, irradiate the single-layer model slice on the cathode plate in the form of a light pattern, the conductivity of the illuminated area of the hydrogenated amorphous silicon layer on the cathode plate surface decreases, and a virtual electrode with the same shape as the light pattern is formed; the negatively charged particles in the suspension gather in the illuminated area of the anode plate under the action of the electric field to achieve single-layer deposition of particles; when one layer of deposition is completed, use a medical syringe pump to finely adjust the piston rod of the reaction device to control the electrode distance to increase the thickness of one layer of deposit; use a medical syringe pump to finely adjust the syringe to control the flow rate of the electrophoretic particle suspension injected into the reaction device to ensure a stable flow rate in the deposition area; switch the projection light source to the new layer of model pattern and start the next layer of deposition. As the piston rod of the reaction device moves, a micro-scale three-dimensional part is printed layer by layer;

[0017] (5) Replacement of deposition material: Disconnect the power supply, discharge the electrophoretic particle suspension in the reaction device, connect the water inlet catheter to the syringe filled with the new material electrophoretic particle suspension, and then use a medical syringe pump to control the injection of the new material electrophoretic particle suspension until the air bubbles in the reaction device are completely discharged and there is no residue of the raw material suspension. Calculate the Reynolds number and the fluid motion equation in the reaction device according to the density and dynamic viscosity of the new material, so as to determine the flow rate of the new material electrophoretic particle suspension; use a medical syringe pump to control the injection flow rate of the new material electrophoretic particle suspension, turn on the power supply, and continue the part deposition;

[0018] (6) Removal of three-dimensional parts: After the deposition is completed, turn off the DC power supply, turn off the projection light source, disconnect the connection between the anode plate and the cathode plate and the power supply, discharge the suspension in the reaction device, take out the piston rod from the cylinder, apply the degluing agent, remove the anode plate, clean the residual electrophoretic particle suspension on the anode plate and sinter it, and a densified micro-scale three-dimensional part can be obtained on the surface of the anode plate. The cathode plate can be deposited multiple times without disassembly. Use deionized water to clean the cathode plate, cylinder, base, piston rod, and dry them.

[0019] The metals in step (1) include copper and tungsten.

[0020] Preparation of the tungsten metal suspension in step (1): Take 1 part of dry tungsten powder into a beaker, add 2 parts of anhydrous ethanol solvent and an appropriate amount of ammonium polyacrylate, stir with a magnetic stirrer for 15 minutes, then perform ultrasonic treatment for 15 minutes, and then perform stirring treatment for 15 minutes to obtain the required suspension. Load the prepared tungsten particle suspension into a syringe for standby.

[0021] The injection flow rate of the electrophoretic particle suspension in step (4) or (5) is calculated as follows:

[0022] Determine the influence of viscous effects on the flow field through the Reynolds number, then list the N - S equations to solve the fluid motion equations. When using a medical syringe pump to push the piston rod of the reaction device, adjust the distance between the anode plate and the cathode plate to 50 μm, and then push the piston assembly of the syringe to inject the metal suspension described above into the reaction device at a flow rate of 2 ml / h. Under these conditions, the Reynolds number Re < 1, which belongs to Stokes flow, and the viscous force dominates. Neglect the inertial force term in the N - S equations and simplify them to:

[0023]

[0024] where p is the pressure vector, μ is the dynamic viscosity, and v is the velocity vector;

[0025] The height of the fluid domain is much smaller than the length and width dimensions. Therefore, the upper and lower boundaries, that is, the cathode plate and the anode plate, have a greater influence on fluid flow. Simplify this flow problem to a steady incompressible planar two - dimensional viscous flow problem and establish a coordinate system, where v y = 0. Substitute the boundary conditions to obtain the velocity as:

[0026]

[0027] where v x is the component of the velocity vector parallel to the electrode plate, and h is the electrode spacing;

[0028] At this time, the relationship between the flow rate and the flow velocity is:

[0029]

[0030] where q is the flow rate, A is the cross - sectional area, is the average velocity on the cross - section;

[0031] As the deposition progresses, the anode plate moves downward and the electrode spacing increases. If the flow rate is controlled to remain constant by increasing the flow volume, the Reynolds number Re increases with the increase of the electrode spacing. Under the condition that the flow rate is 2 ml / h and the electrode spacing is no more than 500 μm, the Reynolds number Re < 1. Therefore, when depositing parts with a small thickness, the horizontal flow velocity at a certain position is determined using formula (2), then the flow volume is determined using formula (3) and formula (4), and a medical syringe pump is used to push the piston assembly to adjust the flow volume of the electrophoretic particle suspension.

[0032] When the electrode spacing is greater than 500 μm and the Reynolds number Re ≥ 1, the influence of the viscous force term is small and can be ignored far from the boundary. The viscous effect is only limited to the vicinity of the boundary layer. Therefore, when depositing parts with a large thickness, the fluid flow can be divided into two parts according to the boundary layer thickness. If the solution point is located within the boundary layer, the local motion equation of the fluid is calculated using the flat plate laminar boundary layer equation:

[0033]

[0034] where ρ is the density of the suspension, and v y is the component of the velocity perpendicular to the electrode plate;

[0035] If the solution point is located outside the boundary layer, the viscous force term is ignored, and the local motion equation of the fluid is calculated using the Euler equation for ideal flow:

[0036]

[0037] where f x is the component of the inertial force parallel to the electrode plate, and f y is the component of the inertial force perpendicular to the electrode plate. At this time, the cross-sectional average flow velocity is:

[0038]

[0039] After obtaining the motion equation, the relationship between the flow velocity and the flow volume is obtained through formula (3) and formula (7), and a medical syringe pump is used to adjust the flow volume of the electrophoretic particle suspension to achieve real-time control of the deposition process.

[0040] The advantages of the present invention are as follows:

[0041] (1) By combining a medical syringe pump with the photo-assisted electrophoretic deposition technology, an electrophoretic additive manufacturing device capable of realizing the supply of the particle suspension, the discharge of bubbles, and the real-time control of the electrode spacing is designed, which improves the printing accuracy and the performance of the parts and can realize the manufacturing of micro-scale complex three-dimensional structures.

[0042] (2) The present invention can observe and control the electrophoretic deposition in real time, can quickly change the types of suspensions, realize the additive manufacturing of composite materials, and can realize the printing of scaffolds in micro-scale three-dimensional structures, having unique advantages in the forming of micro-scale parts with more complex structures.

[0043] (3) The present invention realizes a high-precision control scheme at the micron level at a relatively low price, has a light structure, is convenient to disassemble and assemble, and the device can be reused. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a schematic structural diagram of the present invention;

[0045] Figure 2 is a schematic structural diagram of the projection device of the present invention;

[0046] Figure 3 is a schematic structural diagram of the reaction device of the present invention;

[0047] Figure 4 is a schematic structural diagram of the anode plate and the cathode plate of the present invention;

[0048] Figure 5 is a schematic diagram of the positions of the metal wires of the anode plate and the cathode plate of the present invention;

[0049] Figure 6 is a schematic structural diagram of the syringe and the reaction device of the present invention;

[0050] Figure 7 is a schematic diagram of the deposition scheme in the embodiment of the present invention;

[0051] Figure 8 is a schematic diagram of the flow rate of the suspension in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] Refer to Figure 1 , which includes a projection device 1, a medical syringe pump 2, a syringe 3, a reaction device 4, a water inlet conduit 5, a connector 6, a water outlet conduit 7 and a waste liquid tank 8. Among them, the reaction device 4 and the syringe 3 are respectively fixed on two channels of the medical syringe pump 2. The water inlet of the reaction device 4 is connected to the water inlet conduit 5 through the connector 6, and the syringe 3 and the water outlet are connected to the water outlet conduit 7 through the connector 6 to divert the liquid to the waste liquid tank 8.

[0053] Refer to Figure 2 , the projection device 1 of the present invention includes a 405 nm wavelength light source 101, a positioning block 102 and an internal hexagonal screw 103. The light source 101 is connected to the positioning block 102 through the screw 103, so that the center of the light source 101 is directly opposite to the center position of the hydrogenated amorphous silicon layer 40401 of the cathode plate 404. The light source 101 should be able to focus a beam with a micron-sized resolution of a specific shape on the hydrogenated amorphous silicon layer 40401.

[0054] The medical syringe pump 2 according to the present invention should be able to be used in conjunction with a syringe 3, and should enable the piston assembly 302 of the syringe 3 to move forward and backward with high precision, and be able to achieve high-precision movement at a minimum liquid flow rate of 1 ml / h.

[0055] See Figure 6 , the syringe 3 according to the present invention is composed of a barrel 301 and a piston assembly 302, and should comply with the standard of "YY / T 0573.2-2018 Disposable sterile syringes - Part 2: Syringes for power-driven syringe pumps".

[0056] See Figure 3 , the reaction device 4 according to the present invention includes a cylinder body 401, a base 402, a piston rod 403, a cathode plate 404 and an anode plate 405. The base 402 is composed of an outer rubber layer and an inner insulating material. The base 402 is bonded to the piston rod 403, and the central hole of the base 402 is aligned with the central hole of the piston rod 403. The piston rod 403 and the base 402 are inserted into the cylinder body 401, so that the two side surfaces of the base 402 are respectively aligned with the water inlet and outlet of the cylinder body 401.

[0057] See Figure 4 , the cathode plate 404 according to the present invention includes an amorphous silicon hydride layer 40401, a metal wire 40402, a glass plate 40403 and an ITO layer 40404. The ITO layer 40404 completely covers one side surface of the glass plate 40403, and the amorphous silicon hydride layer 40401 is deposited on the surface of the ITO layer 40404. The size of the cathode plate 404 is slightly larger than the square hole at the top of the cylinder body 401 in the reaction device 4. The cathode plate 404 is bonded to the cylinder body 401, so that the amorphous silicon hydride layer 40401 completely covers the square hole at the top of the cylinder body 401. The metal wire 40402 is connected to the ITO layer 40404, and the metal wire 40402 is used to connect the negative electrode of the power supply to the ITO layer 40404.

[0058] See Figure 5 , the anode plate 405 according to the present invention includes a platinum sheet 40501 and a metal wire 40502. The size of the platinum sheet 40501 is slightly smaller than the square hole at the top of the cylinder body 401. The platinum sheet 40501 is pasted at the center position of the top of the insulating material of the base 402 so that it can just be inserted into the square hole at the top of the cylinder body 401. The metal wire 40502 is welded to the back of the platinum sheet 40501 and passes through the base 402 and the central hole of the piston rod 403. The metal wire 40502 is used to connect to the positive electrode of the power supply.

[0059] An additive manufacturing method using a three-dimensional light-assisted electrophoresis deposition additive manufacturing device with controllable electrode spacing includes the following steps:

[0060] (1) Preparation of electrophoretic particle suspension: The materials for preparation are surfactant, absolute ethanol, and nano-metal powder;

[0061] (2) Setting of illumination pattern: Use modeling software to construct a part model, slice and layer the model along the Z direction so that the thickness of each layer is sub-micron level, import the graphic information of each layer of the model into the control program of the projection light source 1, and the projection light source 1 sets the deposition illumination time for each layer to achieve automatic switching of the illumination pattern;

[0062] (3) Injection of electrophoretic particle suspension: Use a medical syringe pump 2 to push the piston rod 403 of the reaction device 4, adjust the distance between the anode plate 405 and the cathode plate 404 to 50 μm, then push the piston assembly 302 of the syringe 3, and inject the particle suspension at a relatively high flow rate to discharge the air in the cylinder 401 of the reaction device 4 until there is no gas residue in the reaction device 4; During the part deposition process, use the medical syringe pump 2 to control the syringe 3 to continuously inject the particle suspension into the reaction device 4 at a flow rate of 2 ml / h to ensure that the suspension concentration between the anode plate 405 and the cathode plate 404 in the reaction device 4 meets the deposition requirements; As shown in Figure 7 ①, the space between the anode plate 405 and the cathode plate 404 is filled with charged suspended particles;

[0063] (4) Deposition of three-dimensional micro-scale parts: Connect the anode plate 405 and the cathode plate 404 to a DC power supply respectively, turn on the DC power supply, turn on the projection light source 1, and irradiate the single-layer model slice on the cathode plate 404 in the form of a light pattern. As shown in Figure 7 ②, the conductivity of the illuminated area of the hydrogenated amorphous silicon layer 40401 on the surface of the cathode plate 404 decreases, forming a virtual electrode with the same shape as the light pattern; The negatively charged particles in the suspension gather in the illuminated area of the anode plate 405 under the action of the electric field to achieve single-layer deposition of particles; As shown in Figure 7 ③ and ④, when one layer of deposition is completed, use the medical syringe pump 2 to finely adjust the piston rod 403 of the reaction device 4 to control the electrode distance to increase the thickness of one layer of deposit; Use the medical syringe pump 2 to finely adjust the syringe 3 to control the flow rate of the suspension injected into the reaction device 4 to ensure a stable flow rate in the deposition area; Make the projection light source 1 switch to the new layer model pattern and start the next layer of deposition. As the piston rod 403 of the reaction device 4 moves, a micro-scale three-dimensional part is printed layer by layer;

[0064] (5) Replacement of deposition material: Disconnect the power supply, drain the suspension in the reaction device 4, connect the water inlet conduit 5 to the syringe 3 filled with the new material suspension, and then use the medical injection pump 2 to control the injection of the suspension until the bubbles in the reaction device 4 are completely discharged and there is no residue of the raw material suspension. Calculate the Reynolds number and the fluid motion equation in the reaction device 4 based on the density and dynamic viscosity of the new material, so as to determine the flow rate of the new material suspension; use the medical injection pump 2 to control the injection flow rate of the suspension, connect the power supply, and continue with the part deposition;

[0065] (6) Removal of the three-dimensional part: After the deposition is completed, turn off the DC power supply, turn off the projection light source 1, disconnect the connection between the anode plate 405 and the cathode plate 404 and the power supply, drain the suspension in the reaction device 4, take out the piston rod 403 from the cylinder 401, apply the peptizing agent, remove the anode plate 405, clean the residual suspension on the anode plate 405 and sinter it, and a densified micro-sized three-dimensional part can be obtained on the surface of the anode plate 405. The cathode plate 404 can be deposited multiple times without disassembly. Clean the cathode plate 404, the cylinder 401, the base 402 and the piston rod 403 with deionized water and dry them.

[0066] In the step (1), the metals include copper and tungsten.

[0067] Preparation of the tungsten metal suspension in the step (1): Take 1 part of dry tungsten powder into a beaker, add 2 parts of anhydrous ethanol solvent and an appropriate amount of ammonium polyacrylate, stir with a magnetic stirrer for 15 minutes, then carry out ultrasonic treatment for 15 minutes, and then carry out stirring treatment for 15 minutes to obtain the required suspension. Load the prepared tungsten particle suspension into the syringe 3 for standby.

[0068] The injection flow rate of the particle suspension in the step (4) or (5) is calculated as follows:

[0069] As Figure 8 shown, in the three-dimensional light-assisted electrophoresis deposition, the local electric field induces the charged particles to generate an acceleration towards the illuminated area of the anode plate 405 to achieve deposition. However, due to the flow of the suspension, the charged particles have a lateral initial velocity. If the flow rate is too high, the charged particles will break away from the confinement of the local electric field and deposition cannot be achieved; if the flow rate is too low, the particle concentration of the electrophoretic particle suspension during the deposition process will decrease, affecting the deposition efficiency and quality. Therefore, during the deposition process, the flow rate of the electrophoretic particle suspension in the reaction device 4 needs to be kept stable.

[0070] The average flow velocity between the electrodes is related to the cross-sectional area of the region between the anode plate 405 and the cathode plate 404. The average flow velocity can be obtained from the known flow rate and cross-sectional area, and the flow rate is controlled in real time using a medical syringe pump 2. However, the deposition region is narrow, and the flow velocity distribution is greatly affected by the viscous force, resulting in a large velocity gradient and uneven distribution across the cross-section. The influence of the viscous effect on the flow field can be determined by the Reynolds number, and then the N-S equation is listed to solve the fluid motion equation.

[0071] Use the medical syringe pump 2 to push the piston rod 403 of the reaction device 4, adjust the distance between the anode plate 405 and the cathode plate 404 to 50 μm, and then push the piston assembly 302 of the syringe 3 to inject the electrophoretic particle metal suspension described above into the reaction device 4 at a flow rate of 2 ml / h. Under these conditions, the Reynolds number Re < 1, which belongs to Stokes flow, and the viscous force dominates. The inertial force term of the N-S equation can be ignored and simplified to:

[0072]

[0073] where p is the pressure vector, μ is the dynamic viscosity, and v is the velocity vector;

[0074] The height of the fluid domain is much smaller than the length and width dimensions. Therefore, the upper and lower boundaries, that is, the cathode plate 404 and the anode plate 405, have a greater influence on the fluid flow. This flow problem can be simplified to a steady incompressible planar two-dimensional viscous flow problem, and a Figure 8 shown coordinate system is established, where v y = 0. Substituting the shown boundary conditions, the velocity can be obtained as:

[0075]

[0076] where v x is the component of the velocity vector parallel to the electrode plate, and h is the electrode spacing.

[0077] At this time, the relationship between the flow rate and the flow velocity is:

[0078]

[0079] where q is the flow rate, A is the cross-sectional area, is the average velocity across the cross-section;

[0080] As the deposition progresses, the anode plate 405 moves downward, increasing the electrode spacing. If the flow rate is controlled to remain constant by increasing the flow volume, the Reynolds number Re increases with the increase of the electrode spacing. Under the conditions of a flow rate of 2 ml / h and an electrode spacing not greater than 500 μm, the Reynolds number Re < 1. Therefore, when depositing parts with a small thickness, the horizontal flow velocity at a certain position can be determined using formula (2), and then the flow rate can be determined using formula (3) and formula (4). The medical injection pump 2 is used to push the piston assembly 302 to adjust the flow rate of the electrophoretic particle suspension.

[0081] When the electrode spacing is greater than 500 μm and the Reynolds number Re ≥ 1, the influence of the viscous force term is small and can be ignored far from the boundary. The viscous effect is only limited to the vicinity of the boundary layer. Therefore, when depositing parts with a large thickness, the fluid flow can be divided into two parts according to the boundary layer thickness. If the solution point is within the boundary layer, the flat plate laminar boundary layer equation is selected to calculate the local motion equation of the fluid:

[0082]

[0083] where ρ is the density of the suspension, and v y is the component of the velocity perpendicular to the electrode plate;

[0084] If the solution point is outside the boundary layer, the viscous force term is ignored, and the Euler equation of ideal flow is used to calculate the local motion equation of the fluid:

[0085]

[0086] where f x is the component of the inertial force parallel to the electrode plate, and f y is the component of the inertial force perpendicular to the electrode plate. At this time, the cross-sectional average flow velocity is:

[0087]

[0088] After obtaining the motion equation, the relationship between the flow velocity and the flow rate is obtained through formula (3) and formula (7), and the medical injection pump 2 is used to adjust the flow rate of the electrophoretic particle suspension to achieve real-time control of the deposition process.

Claims

1. A three-dimensional light-assisted electrophoresis deposition additive manufacturing device with controllable electrode spacing, characterized in that: It includes a projection device, a medical syringe pump, a syringe, a reaction device, a water inlet conduit, a connector, a water outlet conduit, and a waste liquid tank. The reaction device and the syringe are respectively fixed on two channels of the medical syringe pump. The water inlet of the reaction device is connected to the water inlet conduit through a connector, and the syringe and the water outlet are connected to the water outlet conduit through a connector to divert the liquid to the waste liquid tank; The projection device includes a 405 nm wavelength light source, a positioning block, and an Allen screw. The light source is connected to the positioning block by the screw so that the center of the light source is directly opposite the center position of the hydrogenated amorphous silicon layer of the cathode plate in the reaction device. The light source should be able to focus a beam with a micron-sized resolution of a specific shape on the hydrogenated amorphous silicon layer of the cathode plate; The reaction device includes a cylinder body, a base, a piston rod, a cathode plate, and an anode plate. The base is composed of an outer rubber layer and an inner insulating material. The base is bonded to the piston rod, and the center holes of the base and the piston rod are directly opposite. The piston rod and the base are inserted into the cylinder body so that the two side surfaces of the base are respectively directly opposite the water inlet and outlet of the cylinder body. The cathode plate is bonded to the cylinder body. The anode plate includes a platinum sheet, and the platinum sheet is pasted at the center position of the top of the insulating material of the base so that it can just be inserted into the square hole at the top of the cylinder body.

2. The three-dimensional light-assisted electrophoresis deposition additive manufacturing device with controllable electrode spacing according to claim 1, wherein: The medical syringe pump should be able to be used in combination with the syringe, and it should be able to make the piston assembly of the syringe move forward and backward with high precision, and be able to achieve a high-precision movement with a minimum liquid flow rate of 1 ml / h.

3. The three-dimensional light-assisted electrophoresis deposition additive manufacturing device with controllable electrode spacing according to claim 1, characterized in that: The syringe is composed of an outer sleeve and a piston assembly, and should comply with the standard of "YY / T 0573.2-2018 Disposable Sterile Syringe - Part 2: Syringe for Power-driven Syringe Pump".

4. The three-dimensional photo-assisted electrophoresis deposition additive manufacturing device with controllable electrode spacing according to claim 1, characterized in that: The cathode plate includes a hydrogenated amorphous silicon layer, a metal wire, a glass plate, and an ITO layer. The ITO layer completely covers one side surface of the glass plate, and the hydrogenated amorphous silicon layer is deposited on the surface of the ITO layer. The size of the cathode plate is slightly larger than the square hole at the top of the cylinder body in the reaction device so that the hydrogenated amorphous silicon layer completely covers the square hole at the top of the cylinder body. The metal wire is connected to the ITO layer, and the metal wire is used to connect the negative electrode of the power supply to the ITO layer.

5. The three-dimensional light-assisted electrophoresis deposition additive manufacturing device with controllable electrode spacing according to claim 1, characterized in that: The anode plate includes a platinum sheet and a metal wire. The size of the platinum sheet is slightly smaller than the square hole at the top of the cylinder body. The metal wire is welded to the back of the platinum sheet and passes through the center holes of the base and the piston rod. The metal wire is used to connect to the positive electrode of the power supply.

6. An additive manufacturing method using the additive manufacturing device of three-dimensional photo-assisted electrophoresis deposition with controllable electrode spacing as described in any one of claims 1 to 5, characterized in that, It includes the following steps: (1) Preparation of the electrophoretic particle suspension: The preparation materials are surfactants, anhydrous ethanol, and nano-metal powders. The metal includes copper or tungsten; (2) Setting of the illumination pattern: Use modeling software to construct a part model, slice and layer the model along the Z direction so that the thickness of each layer is sub-micron level, import the graphic information of each layer of the model into the control program of the projection light source, and the projection light source 1 sets the deposition illumination time for each layer to achieve automatic switching of the illumination pattern; (3)Injection of electrophoretic particle suspension: Use a medical syringe pump to push the piston rod of the reaction device, adjust the distance between the anode plate and the cathode plate to 50 μm, then push the piston assembly of the syringe, inject the particle suspension at a relatively high flow rate, and discharge the air in the cylinder body of the reaction device until there is no gas residue in the reaction device; during the deposition process of the part, use a medical syringe pump to control the syringe to continuously inject the electrophoretic particle suspension into the reaction device at a flow rate of 2 ml / h to ensure that the suspension concentration between the anode plate and the cathode plate in the reaction device meets the deposition requirements; (4)Deposition of three-dimensional micro-scale parts: Connect the anode plate and the cathode plate to the DC power supply respectively, turn on the DC power supply, turn on the projection light source, irradiate the single-layer model slice on the cathode plate in the form of a light pattern, and the conductivity of the illuminated area of the hydrogenated amorphous silicon layer on the surface of the cathode plate decreases, forming a virtual electrode with the same shape as the light pattern; the negatively charged particles in the suspension gather in the illuminated area of the anode plate under the action of the electric field, realizing the single-layer deposition of particles; When one layer of deposition is completed, use a medical syringe pump to finely adjust the piston rod of the reaction device to control the electrode distance to increase by the thickness of one layer of deposit; use a medical syringe pump to finely adjust the syringe to control the flow rate of the electrophoretic particle suspension injected into the reaction device to ensure a stable flow rate in the deposition area; switch the projection light source to the new layer of model pattern and start the next layer of deposition. As the piston rod of the reaction device moves, a micro-scale three-dimensional part is printed layer by layer; (5)Replacing the deposition material: Disconnect the power supply, discharge the electrophoretic particle suspension in the reaction device, connect the water inlet conduit to the syringe filled with the electrophoretic particle suspension of the new material, then use a medical syringe pump to control the injection of the electrophoretic particle suspension of the new material until the air bubbles in the reaction device are completely discharged and there is no residue of the raw material suspension. Calculate the Reynolds number and the fluid motion equation in the reaction device according to the density and dynamic viscosity of the new material, so as to determine the flow rate of the electrophoretic particle suspension of the new material; use a medical syringe pump to control the injection flow rate of the electrophoretic particle suspension of the new material, turn on the power supply, and continue the part deposition; (6)Removing the three-dimensional part: After the deposition is completed, turn off the DC power supply, turn off the projection light source, disconnect the connection between the anode plate and the cathode plate and the power supply, discharge the suspension in the reaction device, take out the piston rod from the cylinder body, apply the degluing agent, remove the anode plate, clean the residual electrophoretic particle suspension on the anode plate and sinter it, and a densified micro-scale three-dimensional part can be obtained on the surface of the anode plate. The cathode plate can be deposited multiple times without disassembly. Wash the cathode plate, cylinder body, base, piston rod with deionized water and dry.

7. The additive manufacturing method according to claim 6, characterized in that: The preparation of the tungsten metal suspension in step (1) is as follows: Take 1 part of dry tungsten powder into a beaker, add 2 parts of anhydrous ethanol solvent and an appropriate amount of ammonium polyacrylate, stir with a magnetic stirrer for 15 minutes, then perform ultrasonic treatment for 15 minutes, and then perform stirring treatment for 15 minutes to obtain the required suspension. Load the prepared tungsten particle suspension into a syringe for standby.

8. The additive manufacturing method according to claim 6, wherein: The calculation of the injection flow rate of the electrophoretic particle suspension in step (4) or (5) is as follows: The influence of viscous effects on the flow field is determined by the Reynolds number. Then, the N-S equations are listed to solve the fluid motion equations. Using a medical syringe pump to push the piston rod of the reaction device, the distance between the anode plate and the cathode plate is adjusted to 50 μm. Then, the piston assembly of the syringe is pushed to inject the metal suspension described above into the reaction device at a flow rate of 2 ml / h. Under these conditions, the Reynolds number Re < 1, which belongs to Stokes flow, and the viscous force dominates. The inertial force term of the N-S equation is ignored and simplified to: （1） wherein, is the pressure vector, is the dynamic viscosity, is the velocity vector; The height of the fluid domain is much smaller than its length and width. Therefore, the upper and lower boundaries, namely the cathode plate and the anode plate, have a great influence on fluid flow. The flow problem is simplified to a steady incompressible two-dimensional viscous flow problem in a plane, and a coordinate system is established, where , substituting the boundary conditions, the velocity can be obtained as follows: ； Among them, is the component of the velocity vector parallel to the electrode plate, and h is the electrode spacing; At this time, the relationship between the flow rate and the flow velocity is: ； where q is the flow rate, A is the cross-sectional area, and is the average velocity across the cross-section; With the deposition proceeding, the anode plate moves downward and the electrode distance increases. If the flow rate is increased to keep the flow velocity constant, the Reynolds number Re increases with the increase of the electrode distance. Under the condition of a flow rate of 2 ml / h and an electrode distance not greater than 500 μm, the Reynolds number Re < 1. Therefore, when depositing parts with a small thickness, formula (2) is used to determine the horizontal flow velocity at a certain position, and then formula (3) and formula (4) are used to determine the flow rate, and a medical syringe pump is used to push the piston assembly to adjust the flow rate of the electrophoretic particle suspension; When the electrode distance is greater than 500 μm and the Reynolds number Re ≥ 1, the influence of the viscous force term is small and can be ignored far from the boundary. The viscous effect is only limited to the vicinity of the boundary layer. Therefore, when depositing parts with a large thickness, the liquid flow can be divided into two parts according to the boundary layer thickness. If the solution point is within the boundary layer, the flat plate laminar boundary layer equation is selected to calculate the local fluid motion equation: （5） where ρ is the density of the suspension, is the component of the velocity perpendicular to the electrode plate; If the solution point is outside the boundary layer, the viscous force term is ignored and the Euler equation of ideal flow is used to calculate the local fluid motion equation: （6） Among them, is the component of the inertial force parallel to the electrode plate, is the component of the inertial force perpendicular to the electrode plate. At this time, the cross-sectional average flow velocity is: ； After obtaining the motion equation, the relationship between the flow velocity and the flow rate is obtained through formula (3) and formula (7), and a medical syringe pump is used to adjust the flow rate of the electrophoretic particle suspension to achieve real-time control of the deposition process.

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