Multi-material volumetric light solidification 3D printing apparatus with integrated dynamic fluid control

Abstract

The application discloses a multi-material volume light-curing 3D printing device integrated with dynamic fluid control and relates to the technical field of additive manufacturing 3D printing.The device comprises a rack, a liquid storage part, a light source part and a controller.The liquid storage part is used for storing printing materials, mixed materials and cleaning liquid, and the light source part is used for providing light sources required by photosensitive material curing.The device further comprises a dynamic fluid control module, an automatic switching unit, a flowing water forming assembly, a material recycling module and a printing monitoring module.The multi-material volume light-curing 3D printing device integrated with dynamic fluid control realizes quick and lossless switching of multiple materials, effectively inhibits cross contamination in the switching process of different materials, has the capability of adapting to wide- viscosity materials, can protect biological materials and granular materials from being damaged in the conveying process, is matched with a surrounding light source layout and real-time printing monitoring closed-loop regulation and control, and greatly improves the forming precision and structural consistency of multi-material printing.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing 3D printing technology, specifically to a multi-material volumetric photopolymerization 3D printing device with integrated dynamic fluid control. Background Technology

[0002] Volumetric photopolymerization 3D printing technology has rapidly emerged in the field of precision manufacturing due to its advantages such as no need for layer stacking, fast forming speed, and excellent surface quality. This technology uses multi-angle ultraviolet light exposure to create a three-dimensional light dose field, enabling photosensitive materials to solidify and form quickly. Compared with traditional layer printing technology, it has a significant efficiency advantage in the manufacture of complex structures. However, while existing technologies have the advantages of not requiring layer stacking and having a fast molding speed, they also face problems in multi-material printing scenarios, such as low efficiency of multi-material switching (relying on robotic arms to frequently change molding cavities, which is cumbersome and has poor molding continuity, making it difficult to meet the needs of mass production) and prominent cross-contamination problems (residual materials on the pipes and inner walls of the molding cavity are difficult to completely remove, directly affecting the functional characteristics of the printed structure, especially leading to the scrapping of biomaterials and high-precision functional materials printed parts). Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a multi-material volumetric photopolymerization 3D printing device with integrated dynamic fluid control, which solves the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a multi-material volumetric photopolymerization 3D printing device with integrated dynamic fluid control, comprising a frame, a liquid storage unit, a light source unit, and a controller; the liquid storage unit is used to store printing materials, mixed materials, and cleaning fluid, the light source unit is used to provide the light source required for photosensitive material curing, and also includes a dynamic fluid control module, an automated switching unit, a streamlined forming component, a material recycling module, and a printing monitoring module; The liquid storage section includes a resin storage tank, a mixing tank, a cleaning fluid storage tank, and a mixed material temporary storage tank. Each tank is connected to the dynamic fluid control module through a pipeline. The automated forming component passes through the clearance hole in the middle platform, is rotatably connected to the liquid storage section at the top, and is connected to the material recycling module at the bottom; The controller is electrically connected to the dynamic fluid control module, the automated switching unit, the automated forming assembly, the light source, the material recycling module, and the printing monitoring module, respectively.

[0005] Furthermore, the dynamic fluid control module is an execution unit for material exchange, including a micro Tesla pump and an optimized feed valve; The micro Tesla pump uses a concentric disc rotor to replace the traditional extrusion pump body structure, and uses momentum transfer within the fluid boundary layer to achieve fluid drive. The bladeless structure eliminates dead corners of material residue and is suitable for small-volume closed fluid units. The optimized feed valve is equipped with an air gap isolation structure and deep and shallow dual-branch flow channels. The air gap blocks the direct contact between different materials during the switching process, and the dual-branch flow channels are adapted to the stable conveying of materials with a viscosity range of 1-60 cP. The top of the fluid pool of the dynamic fluid control module is equipped with a PDMS-coated transparent glass window, which combines optical transparency, oxygen permeability and sealing and leak prevention functions. It is used to form an oxygen inhibition layer to help the polymer layer separate and avoid the generation of bubbles.

[0006] Furthermore, the automated switching unit includes multiple sets of resin tanks distributed equidistantly in a ring on the turntable, a washing tank set at the center of the turntable, and a loading robotic arm. The multiple resin tanks are made of high-transmittance materials with transmittance of 85%, 90%, 95%, and 98%, which are adapted to the curing energy requirements of different photosensitive resins; the turntable is positioned by a rotation drive device. The loading robotic arm is equipped with a precision rotating device and a gripping and positioning unit, which is used to hold the printing container and rotate it along the central axis to complete the movement and posture adjustment between the resin tank, the washing tank and the molding area.

[0007] Furthermore, the automated forming assembly includes multiple transparent cylindrical forming cavities connected in series from top to bottom. Each forming cavity is connected to an independent electric valve group, which enables precise control of feeding and discharging, and supports multi-layer gradient material structure printing and parallel printing of multiple parts. The molding cavity and the central platform can rotate relative to each other to cooperate with the light source to achieve 360° surround illumination.

[0008] Furthermore, the central platform is equipped with a Z-axis lifting mechanism and an XY-axis translation mechanism to drive the light source unit to achieve 360° three-dimensional positioning around the molding cavity; The light source unit includes a UV LED, a collimating optical system and a projection lens, and is equipped with a detachable reflective light path to construct a dual-aperture 90° angle illumination mode, which is used to improve molding efficiency and lateral resolution.

[0009] Furthermore, the material recycling module includes a recycling tank with a delivery pump, which is detachably connected to the resin storage tank and the mixed material temporary storage tank via a corrosion-resistant hose, for the purpose of sorting and recycling the remaining materials; The bottom of the mixing tank is equipped with a photosensitive detector to monitor the photosensitive curing threshold of the recycled materials in real time, ensuring that the recycled materials can be reused after meeting the performance standards.

[0010] Furthermore, the printing monitoring module consists of a CCD camera and a red-band LED light source, which is used to capture the printing progress and curing status in real time without interfering with the curing of the photosensitive resin, and to feed back any abnormalities to the controller to form a closed-loop control. The device also includes an auxiliary module, which is electrically connected to the controller and is used to precisely control the oxygen content, temperature and humidity in the molding cavity to adapt to the printing needs of environmentally sensitive materials such as biomaterials.

[0011] Furthermore, the controller has a built-in multi-material printing parameter database, which stores fluid pressure thresholds, flow ranges, printing speeds, and light source exposure parameters for different materials, and is used to automatically call up the appropriate process parameters according to the printing task.

[0012] Furthermore, the operation method of the device includes the following steps: S1 Material Preparation and System Initialization: Load various printing materials into no fewer than 3 resin storage tanks, and load cleaning fluid into the cleaning fluid storage tank; if materials need to be mixed, pump the corresponding raw materials into the mixing tank according to the preset ratio and stir evenly, and monitor the photosensitive curing threshold of the mixed materials through a photosensitive detector; initialize the light source projection system, turntable and loading robotic arm through the controller, and adjust the oxygen content, temperature and humidity in the molding cavity to the standard state through the auxiliary module; S2 Printing Container Positioning: The loading robotic arm works in concert with the first and second links to drive the end gripping and positioning unit to clamp the printing container from the pile of containers to be processed, and adjusts the posture of the printing container through a precision rotating device, and moves it precisely to the top of the target resin tank. S3 Material Delivery and Initial Curing: The dynamic fluid control module pumps the target material from the storage tank into the molding cavity, optimizes the feed valve to select the appropriate flow channel based on the material viscosity (shallow flow channel for low-viscosity materials, deep flow channel for high-viscosity materials) for delivery, and controls shear stress. The light source is activated, projecting ultraviolet light through the dual light ports at a 90° angle to achieve curing of the first layer of material; the printing monitoring module captures the curing status in real time, and if insufficient or excessive curing is detected, the controller adjusts the exposure dose or exposure time immediately. S4 Material Switching and Residual Processing: When material switching is required, the controller closes the current material channel and controls the micro Tesla pump to start the reverse circulation flow, pumping the residual material in the molding cavity and pipeline into the recycling module through the discharge pipeline; after air is injected into the air gap chamber to form a physical blockage, the controller opens the target material channel to complete the material exchange in seconds. S5 Station Switching and Continuous Molding: The central platform drives the automated molding assembly to rotate or translate, precisely aligning the next molding cavity with the light source and feeding channel; repeat steps S3 to S4 to achieve multi-material layer-by-layer curing or parallel printing of multiple parts; if printing multi-layer gradient materials, the feeding and discharging of different materials are controlled by independent electric valve groups in each molding cavity to achieve gradient structure molding; material switching can be triggered automatically by the controller based on model layer data, or manually by the operator; S6 Material Recycling and Equipment Cleaning: After printing, the controller opens the valves at the bottom of each forming cavity, allowing all remaining material to flow into the recycling tank. The material is then pumped back to the corresponding storage tank by the transfer pump according to the material type. The cleaning fluid flows out from the cleaning fluid storage tank and flows through all material channels and forming cavities for a thorough cleaning for 3-5 minutes. The cleaning waste fluid is collected and treated separately. S7 Post-processing: The printed part is removed from the molding cavity and subjected to supplemental UV irradiation for post-curing; if it is a biological material or a precision part, it is subsequently disinfected and cut as needed to obtain the finished product.

[0013] This invention provides a multi-material volumetric photopolymerization 3D printing device with integrated dynamic fluid control, which has the following beneficial effects: 1. This multi-material volumetric photopolymerization 3D printing device with integrated dynamic fluid control relies on the integrated collaborative design of dynamic fluid control module, automated switching unit and streamlined forming components to achieve rapid and non-destructive switching of multiple materials. The pump structure and air gap isolation design eliminate dead corners in the pipeline and effectively suppress cross-contamination during the switching process of different materials. At the same time, it has the ability to adapt to a wide range of viscosity materials, which can protect biological materials and particulate materials from damage during transportation. With the surrounding light source layout and real-time printing monitoring closed-loop control, it can achieve uniform curing and avoid forming defects in 3D printing, which greatly improves the forming accuracy and structural consistency of multi-material printing.

[0014] 2. This multi-material volumetric photopolymerization 3D printing device with integrated dynamic fluid control can classify, recycle, and reuse residual printing materials after performance verification, significantly improving material utilization, reducing production costs, and aligning with the concept of green manufacturing. Simultaneously, it achieves fully automated operation of the entire process, including feeding, material changing, curing, station transfer, recycling, and cleaning, requiring minimal manual intervention. It supports the parallel and continuous production of gradient multi-layer structures and multiple components. Furthermore, it can precisely control the internal atmosphere conditions of the molding cavity through an environmental auxiliary module, adapting to the printing needs of various environmentally sensitive biomaterials. This greatly expands the device's applicability in fields such as biomedical engineering, multifunctional integrated structures, and micro-robot component manufacturing, facilitating industrial-scale mass application. Attached Figure Description

[0015] Figure 1 This is a system structure block diagram of the multi-material volumetric photopolymerization 3D printing device integrating dynamic fluid control according to the present invention; Figure 2 This is a schematic diagram of the loading robotic arm grasping the multi-material volumetric photopolymerization 3D printing device with integrated dynamic fluid control according to the present invention; Figure 3 This is a schematic diagram of the multi-material switching principle of the multi-material volumetric photopolymerization 3D printing device integrating dynamic fluid control according to the present invention; Figure 4 This is a schematic diagram of the micro Tesla pump structure of the multi-material volumetric photopolymerization 3D printing device integrating dynamic fluid control according to the present invention. Figure 5 This is a complete workflow diagram of the multi-material volumetric photopolymerization 3D printing device integrating dynamic fluid control according to the present invention.

[0016] Figure 2 In the middle: 201, fixed base; 202, first connecting rod; 203, second connecting rod; 204, precision rotating device; 205, gripping and positioning unit; 206, printing container; 207, stack of containers to be processed; Figure 3 In the middle: 301, micro Tesla pump; 302, discharge pipeline; 303, air gap chamber; Figure 4 In the middle: 401, concentric disc rotor; 402, fluid flow channel; 403, fluid inlet; 404, fluid outlet. Detailed Implementation

[0017] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention. This invention provides a technical solution: a multi-material volumetric photopolymerization 3D printing device integrating dynamic fluid control, the overall system structure of which is as follows: Figure 1 As shown, it includes a frame, liquid storage unit, dynamic fluid control module, automated switching unit, automated forming assembly, light source unit, material recycling module, printing monitoring module, auxiliary module and industrial PLC controller; each module is fluidly connected through corrosion-resistant PTFE pipelines and electrically connected through RS485 bus, and the controller coordinates the entire process of automated operation of feeding, curing, switching, recycling and cleaning.

[0018] Specifically, the liquid storage section, located on the upper part of the frame, includes four 2L resin storage tanks, one 1L mixing tank with a stirrer, one 3L cleaning fluid storage tank, and one 500mL mixed material temporary storage tank. Each tank is equipped with a corrosion-resistant electromagnetic diaphragm valve at the bottom, connected to the inlet of the dynamic fluid control module via a φ6mm PTFE pipe. The mixing tank is equipped with adjustable-speed PTFE stirring blades (speed range 0-300rpm), and a high-precision photosensitive detector is embedded at the bottom, with a detection wavelength range of 320-400nm and a detection accuracy of ±1mJ / cm². The cleaning fluid storage tank is connected to all material delivery channels and the molding cavity through a multi-way valve, achieving thorough cleaning of the entire pipeline without dead angles.

[0019] Dynamic fluid control module: As the execution unit for material exchange, its structure is as follows Figure 3 , Figure 4 As shown, it includes one micro Tesla pump 301 and one set of integrated optimized feed valves. The micro Tesla pump 301 uses a concentric disc rotor 401 with a diameter of 15mm. The fluid enters the annular fluid channel 402 from the fluid inlet 403, and flows out from the fluid outlet 404 after boundary layer momentum transfer. The bladeless design completely eliminates dead zones of material residue, and the fluid shear stress during operation is also reduced. This effectively avoids damage to biological cells and sedimentation of particulate materials. The optimized feed valve features a built-in independent air gap chamber 303 and deep and shallow dual-branch flow channels (deep channel cross-section 2mm×2mm, shallow channel cross-section 1mm×1mm). When switching materials, a physical isolation layer is first formed in the air gap chamber 303 by 0.1MPa compressed air, and then the corresponding flow channel is automatically switched according to the material viscosity: the shallow flow channel is used for low-viscosity materials (1-20cP), and the deep flow channel is used for high-viscosity materials (20-60cP). The top of the fluid pool is covered with a 0.5mm thick PDMS-coated transparent quartz glass window with a light transmittance ≥95% and an oxygen permeability coefficient of [missing information]. It can ensure efficient penetration of ultraviolet light, form a stable oxygen suppression layer at the curing interface, and completely seal to prevent air bubbles from entering the molding cavity.

[0020] Automated switching unit: Located above the platform in the middle of the rack, with the following structure. Figure 2As shown, the system includes a high-precision servo turntable with a diameter of 300mm, six equidistantly distributed resin tanks in annular rings, a washing tank located at the center of the turntable, and a six-degree-of-freedom loading robotic arm. The six resin tanks are made of fused silica glass with light transmittance of 85%, 90%, 90%, 95%, 95%, and 98%, respectively, to meet the curing requirements of photosensitive resins at three different wavelengths: 365nm, 385nm, and 405nm. The servo turntable has a rotational positioning accuracy of ±0.02mm and a maximum rotational speed of 60° / s, enabling precise positioning of any resin tank within 0.5s. The loading robotic arm is mounted on the side of the frame via a fixed base 201 and consists of a first connecting rod 202, a second connecting rod 203, a precision rotating device 204, and a gripping and positioning unit 205. Its end-effector repeatability is ±0.01mm, and it can grip a cylindrical printing container 206 with a diameter of 50mm to complete three-dimensional movement and 360° attitude adjustment between the resin tank, the washing tank, and the molding area.

[0021] The automated molding assembly comprises three transparent quartz cylindrical molding cavities connected in series from top to bottom. Each cavity has an inner diameter of 50mm and an effective molding height of 100mm. Each cavity is connected to an independent infeed and discharge solenoid valve, allowing for independent control of the feeding, discharging, and curing processes. It supports multi-layer gradient material structure printing and parallel printing of three components. The molding cavity is connected to the central platform via a rotating shaft, allowing it to rotate 360° with the platform and provide surround illumination in conjunction with the light source. The central platform integrates a Z-axis lifting mechanism and an XY-axis translation mechanism. The Z-axis lifting mechanism has a maximum stroke of 50cm and a positioning accuracy of ±0.01mm. The XY-axis translation mechanism has a stroke of 200mm×200mm and a positioning accuracy of ±0.005mm, enabling precise movement of the light source in three-dimensional space to ensure that the energy distribution uniformity deviation in various areas of complex structures is ≤3%.

[0022] The light source consists of a 365nm UVLED array (power density adjustable from 0-100mW / cm²), a collimating optical system, a 2560×1600 resolution DLP projection lens, and a detachable reflector assembly. By installing a reflector with a 90° angle, a dual-aperture illumination mode can be constructed, which improves the forming efficiency by more than 45% compared to a single-aperture mode. The optical resolution of the projection lens is 20μm, which can meet the printing needs of precision biological scaffolds and microstructures.

[0023] Material recycling module: Includes three separate recycling tanks with precision delivery pumps, corresponding to hydrogel, resin, and ceramic particle materials respectively; each recycling tank inlet is equipped with a 100μm corrosion-resistant stainless steel filter to filter impurities and solidified debris from the material; the recycling tanks are detachably connected to each resin storage tank via quick-connect connectors, and any remaining material after printing can be filtered and pumped back to the original storage tank for recycling; a photosensitive detector at the bottom of the mixing tank can detect the curing threshold of the recycled material in real time. When the detected value deviates from the standard value by more than 5%, the system automatically marks the batch of material as unqualified and discharges it into a dedicated waste liquid tank to avoid affecting print quality.

[0024] Printing monitoring module: Composed of a 1.3-megapixel global shutter CCD camera and a 625nm red band LED ring light source, installed directly above the forming cavity; the 625nm red light will not trigger the curing reaction of most photosensitive resins, and can capture real-time images of the surface of the cured layer during the printing process; the system's built-in image recognition algorithm can automatically detect common printing defects such as blurred edges, surface cracks, bubbles, and material shortages, with a detection response time of ≤100ms, and feeds abnormal signals back to the controller, which automatically adjusts the exposure dose, material flow rate, or robotic arm posture to form a closed-loop quality control.

[0025] Auxiliary modules include an oxygen concentration regulator, a precision temperature controller, and a humidity controller, which can precisely control the environmental parameters in the molding cavity at an oxygen concentration of 100-500ppm (accuracy ±10ppm), a temperature of 20-30℃ (accuracy ±0.5℃), and a humidity of 30%-70% (accuracy ±2%), fully meeting the printing requirements of environmentally sensitive biomaterials such as hydrogels and cell-loaded materials.

[0026] Controller: An industrial-grade PLC controller is used, which has a built-in multi-material printing parameter database containing more than 50 commonly used photosensitive resins, biomaterials and particle-loaded materials. The database stores process parameters such as fluid pressure threshold, flow range, pump speed, light source exposure dose, exposure time and material exchange time for each material. The controller can automatically identify material requirements and layering information based on the imported STL model, call the corresponding process parameters, and coordinate the work of each module according to the preset timing.

[0027] like Figure 5 As shown, the specific implementation steps are as follows: S1 Material Preparation and Performance Testing Single material preparation: Methacrylic anhydride gelatin hydrogel (viscosity 15 cP), polylactic acid photosensitive resin (viscosity 35 cP), and hydroxyapatite particle-loaded polylactic acid resin (particle content 30 wt%, viscosity 55 cP) were respectively loaded into 3 independent resin storage tanks. Anhydrous ethanol cleaning solution was loaded into the cleaning solution storage tank. The tank sealing caps were tightened and the airtightness was checked.

[0028] Preparation of mixed materials: If printing cell-loaded hydrogels is required, add sterilized methacrylic anhydride gelatin powder and PBS buffer at a ratio of 10% (w / v) to the mixing vessel, start the stirrer and stir at 150 rpm for 30 minutes until completely dissolved; after the solution cools to 37°C, proceed as follows... Add the bone marrow mesenchymal stem cell suspension to the specified density and stir at a low speed of 50 rpm for 5 minutes to ensure uniform cell distribution. The photosensitizer at the bottom of the mixing tank detects the curing threshold of the mixed material in real time. When the detection value is stable at 75±2 mJ / cm², the material performance is confirmed to meet the standard. The mixed cell hydrogel is then pumped into the mixed material storage tank for later use.

[0029] Material parameter input: Enter the viscosity, curing threshold, recommended flow rate and exposure parameters of the three materials into the controller database, or directly select the corresponding material parameters that already exist in the database.

[0030] S2 System Initialization and Environmental Calibration The controller starts automatically and performs a full system self-test: checking the opening and closing status of each valve, the operating status of the micro Tesla pump 301, the zero position of the servo turntable and the loading robot arm, the stability of the light source energy, and whether the signals of each sensor are normal; if an abnormality is found, the system immediately stops initialization and displays a fault code.

[0031] The auxiliary module is activated, and the environmental parameters inside the molding cavity are adjusted to standard conditions according to the printing requirements of cell hydrogel: oxygen concentration 200ppm, temperature 25℃, humidity 50%, and maintained stable operation for 10 minutes.

[0032] Light source calibration: Use an ultraviolet energy meter to calibrate the output energy of the light source to ensure that the energy density deviation at the center and four corners of the projection surface is ≤3%; according to the material curing threshold, set the exposure dose of the hydrogel layer to 75mJ / cm², the polylactic acid layer to 120mJ / cm², and the ceramic particle layer to 180mJ / cm².

[0033] Pipeline venting: The controller controls the dynamic fluid control module to pump a small amount of air into each material channel to expel residual air bubbles in the pipeline and ensure stable subsequent material delivery.

[0034] S3 Printing Container Positioning and Loading The loading robotic arm clamps a sterilized transparent quartz printing container 206 from the stack of containers to be processed 207 on the side of the frame, and adjusts the printing container 206 to a vertical position through a precision rotating device 204.

[0035] The robotic arm moves the printing container 206 above the central washing tank, sprays the inner wall of the container with anhydrous ethanol for 30 seconds, and then dries it with compressed air to prevent residual impurities on the container surface from affecting the printing quality.

[0036] The robotic arm precisely moves the cleaned printing container 206 directly above the hydrogel resin tank, then lowers it to a position where the bottom of the printing container 206 is 1mm below the surface of the resin tank, ready for feeding.

[0037] S4 First Layer Material Delivery and Curing The controller sends a feeding command to the dynamic fluid control module, optimizes the feeding valve to automatically select a shallow flow channel based on the viscosity of the hydrogel (15 cP), and the micro Tesla pump 301 pumps the cell hydrogel from the mixed material storage tank into the printing container 206 at a speed of 200 rpm, with the flow rate controlled at 5 mL / min.

[0038] When the material liquid level in the printing container 206 reaches the preset height (2mm), the micro Tesla pump 301 stops running and the optimized feed valve closes the hydrogel channel. At this time, an oxygen inhibition layer with a thickness of about 10μm is formed between the PDMS coated glass window at the top of the fluid pool and the material liquid level to prevent the cured layer from sticking to the glass window.

[0039] The light source unit activates the dual-port 90° angle irradiation mode and exposes the hydrogel layer to a preset exposure dose of 75 mJ / cm² for 1.5 seconds.

[0040] The printing monitoring module captures real-time images of the cured hydrogel layer surface and uses image recognition algorithms to detect edge clarity and surface smoothness. If blurred edges are detected (insufficient curing), the controller automatically increases the exposure dose of the next layer by 10%. If surface cracking is detected (over-curing), the exposure dose is reduced by 15%, and the material flow rate is reduced to 4 mL / min.

[0041] After confirming that the first layer of curing quality is up to standard, the Z-axis lifting mechanism of the central platform raises the light source unit by 2mm, preparing for the next layer to be printed.

[0042] S5 Material Switching and Cross-Contamination Control When the controller detects that the model data needs to be switched from hydrogel to polylactic acid resin, it automatically triggers the material switching process (or the operator can manually trigger the switching command through the controller).

[0043] The controller first closes the hydrogel feeding channel and simultaneously starts the reverse circulation mode of the micro Tesla pump 301, which generates a backward suction force at a speed of 300 rpm to pump the hydrogel remaining in the printing container 206 and pipeline into the hydrogel-specific recycling tank through the discharge pipeline 302. The pumping time is 0.5 seconds. After the residual material is extracted, compressed air of 0.1 MPa is injected into the air gap chamber 303 of the optimized feed valve to form an air isolation layer with a thickness of about 2 mm, which completely blocks the direct contact between the residual hydrogel and the subsequent polylactic acid resin.

[0044] The feed valve is optimized to switch to the polylactic acid resin channel. The deep flow channel is automatically selected according to the viscosity of polylactic acid (35 cP). The micro Tesla pump 301 pumps polylactic acid resin into the printing container 206 at a speed of 250 rpm. The total time of the entire material exchange process is ≤1 second.

[0045] Cross-contamination verification: After printing, energy dispersive spectroscopy analysis was performed on the material switching interface. The results showed that the residual amount of hydrogel component in the polylactic acid layer was ≤0.3%, which is far lower than the industry standard requirement of 1%, proving that the air gap isolation and backflushing technology can effectively control cross-contamination.

[0046] S6 Station Switching and Continuous Molding After the polylactic acid layer is printed, the central platform drives the entire assembly line to rotate 120°, precisely aligning the second empty forming cavity with the light source and the feeding channel, with a positioning accuracy of ±0.005mm.

[0047] Repeat steps S4 to S5 to complete the printing of the polylactic acid transition layer and the hydroxyapatite ceramic particle load-bearing layer in sequence. When printing the ceramic particle layer, optimize the feed valve to select the deep flow channel, run the micro Tesla pump 301 at a speed of 300 rpm, control the flow rate at 6 mL / min, set the exposure dose to 180 mJ / cm², and set the exposure time to 2 s.

[0048] If multiple identical or different parts need to be printed simultaneously, parallel printing can be achieved using three serially connected molding cavities: the first molding cavity prints the hydrogel layer, the second molding cavity prints the polylactic acid layer, and the third molding cavity prints the ceramic particle layer. Each molding cavity independently controls feeding and curing, and the overall production efficiency is increased by more than 200% compared to a single molding cavity.

[0049] S7 Multi-layer Gradient Structure Molding For structures requiring continuous gradient changes, the controller automatically calculates the material mixing ratio for each layer based on the gradient distribution data of the model. For example, in the transition region between hydrogel and polylactic acid, the dynamic fluid control module pumps the hydrogel and polylactic acid into the mixing tank at different ratios, mixes them in real time, and then delivers them to the molding cavity to achieve continuous gradient changes in material properties.

[0050] During the printing process, the printing monitoring module continuously monitors the curing quality and forming accuracy of each layer, and performs a global accuracy test every 10 layers. If the deviation of the forming cavity position exceeds ±0.01mm, the controller automatically controls the XY translation mechanism of the central platform to make compensation adjustments to ensure the positional accuracy of the entire printing process.

[0051] S8 Material Recycling and Equipment Cleaning After all printing tasks are completed, the controller opens the discharge valve at the bottom of each forming cavity to discharge all the remaining material into the corresponding recycling tank; the conveying pump in the recycling tank starts to pump the filtered material back to the original storage tank. In this embodiment, the average recovery rate of the three materials is ≥92%.

[0052] After the material recycling is completed, the automatic cleaning process is started: the discharge valve of the cleaning solution storage tank is opened, and the anhydrous ethanol cleaning solution flows through all material channels, molding cavities and resin tanks at a flow rate of 10mL / min, circulating and cleaning for 4 minutes to thoroughly remove residual resin materials.

[0053] After cleaning, the compressed air pump is started to blow dry the residual cleaning liquid in the pipeline and molding cavity for 2 minutes; the cleaning waste liquid is discharged into a special hazardous waste collection bucket for unified environmental protection treatment.

[0054] The controller automatically records all process parameters, material consumption, printing time, and quality inspection data for this printing, generates a printing report, and archives it.

[0055] S9 Printing Post-processing The loading robotic arm removes the printed gradient bracket from the printing container 206, gently rinses the surface with anhydrous ethanol to remove any remaining uncured resin, and then rinses it three times with PBS buffer for five minutes each time.

[0056] The stent was placed under a 365nm UV lamp for post-curing treatment for 10 minutes to enhance its mechanical strength.

[0057] For the cell-loaded hydrogel layer, the scaffold was immersed in DMEM medium containing 10% fetal bovine serum and incubated at 37°C. After being cultured in an incubator for 24 hours, the cells can be used for subsequent animal experiments or clinical studies once they have adhered to the incubator.

[0058] For polylactic acid layers supported by ceramic particles, if further improvement of mechanical properties is required, the support can be placed in a high-temperature furnace for degreasing and sintering: the temperature is raised to 600℃ at a rate of 5℃ / min, held for 2 hours for degreasing, and then raised to 1250℃ at a rate of 10℃ / min, held for 3 hours for sintering. After natural cooling, the final ceramic support is obtained.

[0059] In summary, this multi-material volumetric photopolymerization 3D printing device with integrated dynamic fluid control achieves rapid and non-destructive switching of multiple materials through the integrated collaborative design of the dynamic fluid control module, automated switching unit, and streamlined forming components. The pump structure and air gap isolation design eliminate dead zones in the pipeline, effectively suppressing cross-contamination during the switching process of different materials. It also possesses wide viscosity material compatibility, protecting biological and particulate materials from damage during transport. Combined with a surrounding light source layout and real-time printing monitoring closed-loop control, it achieves uniform curing and avoids forming defects in 3D printing, significantly improving the forming accuracy and structural consistency of multi-material printing.

[0060] It can classify, recycle, and reuse leftover printing materials, significantly improving material utilization, reducing production costs, and aligning with the concept of green manufacturing. At the same time, it achieves fully automated operation of the entire process, including feeding, material changing, curing, workstation transfer, recycling, and cleaning, without requiring extensive manual intervention. It can support the parallel and continuous production of gradient multi-layer structures and multiple components, and can also precisely control the internal atmosphere conditions of the molding cavity through an environmental auxiliary module, adapting to the printing needs of various environmentally sensitive biomaterials. This greatly expands the applicable scenarios of the device in fields such as biomedical engineering, multifunctional integrated structures, and micro-robot component manufacturing, facilitating industrial-scale mass promotion and application.

[0061] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A multi-material volumetric photopolymerization 3D printing device with integrated dynamic fluid control, comprising a frame, a liquid storage unit, a light source unit, and a controller; wherein the liquid storage unit is used to store printing materials, mixed materials, and cleaning fluid, and the light source unit is used to provide the light source required for curing photosensitive materials, characterized in that: It also includes a dynamic fluid control module, an automated switching unit, a streamlined forming assembly, a material recycling module, and a printing monitoring module; The liquid storage section includes a resin storage tank, a mixing tank, a cleaning fluid storage tank, and a mixed material temporary storage tank. Each tank is connected to the dynamic fluid control module through a pipeline. The automated forming component passes through the clearance hole in the middle platform, is rotatably connected to the liquid storage section at the top, and is connected to the material recycling module at the bottom; The controller is electrically connected to the dynamic fluid control module, the automated switching unit, the automated forming assembly, the light source unit, the material recycling module, and the printing monitoring module, respectively. The dynamic fluid control module is the execution unit for material exchange, including a micro Tesla pump and an optimized feed valve; The micro Tesla pump uses a concentric disc rotor to replace the traditional extrusion pump body structure, and uses momentum transfer within the fluid boundary layer to achieve fluid drive. The bladeless structure eliminates dead corners of material residue and is suitable for small-volume closed fluid units. The optimized feed valve is equipped with an air gap isolation structure and deep and shallow dual-branch flow channels. The air gap blocks the direct contact between different materials during the switching process, and the dual-branch flow channels are adapted to the stable conveying of materials with a viscosity range of 1-60 cP. The top of the fluid pool of the dynamic fluid control module is equipped with a PDMS-coated transparent glass window, which combines optical transparency, oxygen permeability and sealing and leak prevention functions. It is used to form an oxygen inhibition layer to help the polymer layer separate and avoid the generation of bubbles. The automated switching unit includes multiple sets of resin tanks distributed equidistantly in a ring on the turntable, a washing tank set at the center of the turntable, and a loading robotic arm. The multiple resin tanks are made of high-transmittance materials with transmittance of 85%, 90%, 95%, and 98%, which are adapted to the curing energy requirements of different photosensitive resins; the turntable is positioned by a rotation drive device. The loading robotic arm is equipped with a precision rotating device and a gripping and positioning unit, which is used to hold the printing container and rotate it along the central axis and complete the movement and posture adjustment between the resin tank, the washing tank and the molding area. The automated forming assembly includes multiple transparent cylindrical forming cavities connected in series from top to bottom. Each forming cavity is connected to an independent electric valve group. The independent electric valve group enables precise control of feeding and discharging, and supports multi-layer gradient material structure printing and parallel printing of multiple parts. The molding cavity and the central platform are rotatable relative to each other, which is used to cooperate with the light source to achieve 360° surround irradiation; The printing monitoring module consists of a CCD camera and a red-band LED light source, which is used to capture the printing progress and curing status in real time without interfering with the curing of the photosensitive resin, and to feed back abnormal situations to the controller to form a closed-loop control. The device also includes an auxiliary module, which is electrically connected to the controller and is used to precisely control the oxygen content, temperature and humidity in the molding cavity to adapt to the printing needs of environmentally sensitive materials such as biomaterials.

2. The multi-material volumetric photopolymerization 3D printing device with integrated dynamic fluid control according to claim 1, characterized in that: The central platform is equipped with a Z-axis lifting mechanism and an XY-axis translation mechanism, which are used to drive the light source to achieve 360° three-dimensional positioning around the molding cavity; The light source unit includes a UV LED, a collimating optical system and a projection lens, and is equipped with a detachable reflective light path to construct a dual-aperture 90° angle illumination mode, which is used to improve molding efficiency and lateral resolution.

3. The multi-material volumetric photopolymerization 3D printing device with integrated dynamic fluid control according to claim 1, characterized in that: The material recycling module includes a recycling tank with a delivery pump. The recycling tank is detachably connected to the resin storage tank and the mixed material temporary storage tank via a corrosion-resistant hose, which is used to realize the classified recycling of the remaining materials. The bottom of the mixing tank is equipped with a photosensitive detector to monitor the photosensitive curing threshold of the recycled materials in real time, ensuring that the recycled materials can be reused after meeting the performance standards.

4. The multi-material volumetric photopolymerization 3D printing device with integrated dynamic fluid control according to claim 1, characterized in that: The controller has a built-in multi-material printing parameter database, which stores fluid pressure thresholds, flow ranges, printing speeds, and light source exposure parameters for different materials. This database is used to automatically call up the appropriate process parameters according to the printing task.

5. The integrated dynamic fluid control multi-material volumetric photopolymerization 3D printing apparatus according to any one of claims 1-4, characterized in that: The operation method of the device includes the following steps: S1 Material Preparation and System Initialization: Load various printing materials into no less than 3 resin storage tanks, and load cleaning fluid into the cleaning fluid storage tank; If materials need to be mixed, the corresponding raw materials are pumped into the mixing tank according to the preset ratio and stirred evenly. The photosensitive curing threshold of the mixed materials is monitored by a photosensitive detector. The light source projection system, turntable and feeding robot arm are initialized by the controller. The oxygen content, temperature and humidity in the molding cavity are adjusted to the standard state by the auxiliary module. S2 Printing Container Positioning: The loading robotic arm works in concert with the first and second links to drive the end gripping and positioning unit to clamp the printing container from the pile of containers to be processed, and adjusts the posture of the printing container through a precision rotating device, and moves it precisely to the top of the target resin tank. S3 Material Delivery and Initial Curing: The dynamic fluid control module pumps the target material from the storage tank into the molding cavity. The optimized feed valve selects the appropriate flow channel based on the material viscosity, using shallow channels for low-viscosity materials and deep channels for high-viscosity materials, while controlling shear stress. The light source is activated, projecting ultraviolet light through the dual light ports at a 90° angle to achieve the curing of the first layer of material. The printing monitoring module captures the curing status in real time. If insufficient or excessive curing is detected, the controller will adjust the exposure dose or exposure time immediately. S4 Material Switching and Residual Processing: When material switching is required, the controller closes the current material channel and controls the micro Tesla pump to start the reverse circulation flow, pumping the residual material in the molding cavity and pipeline into the recycling module through the discharge pipeline; after air is injected into the air gap chamber to form a physical blockage, the controller opens the target material channel to complete the material exchange in seconds. S5 Station Switching and Continuous Molding: The central platform drives the automated molding assembly to rotate or translate, precisely aligning the next molding cavity with the light source and feeding channel; repeat steps S3 to S4 to achieve multi-material layer-by-layer curing or parallel printing of multiple parts; if printing multi-layer gradient materials, the feeding and discharging of different materials are controlled by independent electric valve groups in each molding cavity to achieve gradient structure molding; material switching can be triggered automatically by the controller based on model layer data, or manually by the operator; S6 Material Recycling and Equipment Cleaning: After printing, the controller opens the valves at the bottom of each forming cavity, allowing all remaining material to flow into the recycling tank. The material is then pumped back to the corresponding storage tank by the transfer pump according to the material type. The cleaning fluid flows out from the cleaning fluid storage tank and flows through all material channels and forming cavities for a thorough cleaning for 3-5 minutes. The cleaning waste fluid is collected and treated separately. S7 Post-processing: The printed part is removed from the molding cavity and subjected to supplemental UV irradiation for post-curing; if it is a biological material or a precision part, it is subsequently sterilized and cut as needed to obtain the finished product.

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