A multi-material mixing and continuous 3D printing device and method for realizing biological gradient

Abstract

The application discloses a kind of multi-material mixing and continuous 3D printing device and method for realizing biological gradient, adopts XYZ three-axis motion module, multi-channel biological material, adjusts the feed rate and acceleration of multiple independent control syringes in real time during printing to realize real-time fast mixing of multi-material and printing physical property adjustable biological component;At the same time, low viscosity material containing cells can be printed in supporting bath, and biological functionalization integrated forming is realized;Camera tracks and takes gray scale photo of printed biological component in real time, calculates the gray value of each frame photo, judges mixing effect;And auxiliary ultraviolet laser module is pre-cured to biological component, detects the wire diameter and the forming quality of extruded wire, guides ultraviolet laser module to change laser power, guarantees good printing performance and biological activity.The application can realize the integrated low cost and high efficiency manufacturing of complex three-dimensional space structure of continuous functional gradient biological material.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing and biofunctionalized gradient materials / structure manufacturing technology, specifically relating to a device and method for realizing multi-material homogenization and continuous 3D printing of bio-gradient materials. Background Technology

[0002] Functionally graded materials (FGMs) are widely used in various fields due to their excellent properties. However, traditional FGM fabrication techniques suffer from long production cycles, high costs, and difficulties in manufacturing complex-shaped parts, limiting their application in many areas. With the rapid development of 3D printing technology, the fabrication of FGMs suitable for complex environments has become a current research hotspot. FGMs have shown great advantages in biomedicine, particularly for artificial bone implants, dental implants, and tissue engineering scaffolds.

[0003] 3D bioprinting technology can effectively simulate the complexity of tissues and fabricate multi-level gradient scaffold structures. Most importantly, it allows for the precise and controllable distribution of cells and / or bioactive molecules onto the scaffold. Anisotropic scaffolds loaded with multiple cells and various bioactive molecules from multiple materials can be used for research on biofunctionalized in vitro models. Therefore, 3D bioprinting technology has become a highly promising method for fabricating biofunctionalized gradient material components.

[0004] It is understood that the main methods for preparing spatial gradient components currently include: vapor deposition, powder metallurgy, centrifugal casting, spark plasma sintering, thermal spraying, electrochemical methods, centrifugal forming, slip casting, plasma spraying, self-propagating high-temperature synthesis, and electrolytic extraction. However, these traditional manufacturing methods can only produce simple gradient components and are insufficient for forming continuous functional gradient components made of multiple materials, especially for the integrated manufacturing of continuous biofunctional gradient components with complex spatial shapes. Furthermore, the entire forming and manufacturing process is complex, inefficient, and costly. In recent years, bio-3D printing technology has emerged, offering a novel technical solution for manufacturing biofunctional gradient components, particularly providing an ideal solution for the preparation and integrated forming of multi-material spatial gradient biofunctional components.

[0005] However, existing 3D printing technologies still have limitations in the fabrication and integrated molding of biofunctionalized gradient components. For example, when manufacturing components with complex spatial structures, it is difficult to achieve precise control over biofunctionality and print components with gradient structures. In particular, there is a lack of efficient and rapid integrated molding methods for the precise in vitro fabrication of biofunctionalized continuous gradient components. Furthermore, because biomaterials need to maintain high bioactivity during printing, the types of printable biomaterials are very limited, and their printing performance is inferior to conventional printing materials. Therefore, low-viscosity matrix materials exhibit severe flow and wetting characteristics at the beginning of printing, making precise geometric control difficult and resulting in poor surface roughness and poor geometric accuracy and surface roughness of the formed parts. Therefore, in vitro printing of low-viscosity biomaterials while maintaining their bioactivity during the printing process is a recognized challenge.

[0006] When printing with multiple materials, it is necessary to switch materials in different printing areas and mix multiple materials to achieve gradient effects in different areas. This inevitably leads to printing delays between different areas. These delays accumulate and continuously affect subsequent printing processes, resulting in poor process stability and low printing efficiency. Especially when printing multiple materials simultaneously, it is crucial to integrate material mixing, printing trajectory planning, and printing functionality into a single system. Furthermore, it is essential to ensure a strict sequence and synchronization of feeding, gradient material mixing, and printing path planning during the printing process; otherwise, it is difficult to accurately achieve the integrated molding of biofunctionalized gradient components. Summary of the Invention

[0007] To address the problems in the prior art, this invention provides a device for realizing multi-material mixing and continuous 3D printing with bio-gradients, comprising: a frame, an injection system, an end effector, a support bath unit, a base plate system, an XYZ three-axis motion module, a camera module, an ultraviolet laser module, and a control system; the end effector is equipped with a mixing unit.

[0008] The injection system is fixed to the frame and connected to the end effector, and alternately injects different biomaterials into the mixing unit in the end effector; the mixing unit mixes the injected biomaterials, and the mixed biomaterials are extruded through the outlet of the end effector; the support bath unit is located below the end effector, and the end effector squeezes the mixed biomaterials into the support bath unit to form a bio-component; wherein, the biomaterials include bio-ink and gradient materials of different concentrations;

[0009] The XYZ three-axis motion module includes an X-axis motion module, a Y-axis motion module, and a Z-axis motion module, all of which are connected to the control system. The Z-axis motion module is mounted on the frame and connected to the base plate system, receiving signals from the control system to drive the base plate system to move in the Z-axis direction. The support bath unit is placed on the base plate system and moves with the base plate system. The Y-axis motion module and the X-axis motion module are also mounted on the frame, and both receive signals from the control system to jointly drive the end effector to move laterally or longitudinally in the horizontal direction.

[0010] The camera module is mounted on the rack and connected to the control system. The camera module tracks the biological components in the support bath unit in real time and takes grayscale photos of the biological components. The control system calculates the grayscale value of each frame of the grayscale photo to determine the mixing effect of the material. Based on the mixing effect, the frequency and flow rate of the biological material alternately injected into the end effector are adjusted.

[0011] The ultraviolet laser module is arranged around the support bath unit and is used to cure the biological components with ultraviolet laser. The ultraviolet laser module is connected to the control system, which controls the power of the ultraviolet laser module and adjusts the pre-curing quality of the biological components.

[0012] The end effector also includes a temperature control module, which is used to ensure a constant temperature when various biological materials are mixed, thereby ensuring the biological activity of the biological materials; the base plate system includes a temperature control platform, on which the support bath unit is placed, and the temperature control platform is used to control the temperature of the support bath unit to be constant during the printing process.

[0013] Furthermore, the gradient material is a hydrogel of different concentrations, and the bio-ink is a uniform mixture of fibroblast culture medium and fibroblasts, and a uniform mixture of hepatic stellate cell culture medium and hepatic stellate cells.

[0014] Further, the mixing unit includes a multi-channel mixing unit I, a multi-channel mixing unit II, and a converging channel. The sum of the number of channels in multi-channel mixing unit I and multi-channel mixing unit II is less than or equal to the number of syringes. Multi-channel mixing unit I and multi-channel mixing unit II have the same structure, both including a floating mixing stirrer. The injection system injects biological material into the mixing unit through multiple tubing. The biological material enters the floating mixing stirrer through the tubing, and the mixed biological material is extruded from the outlet of the floating mixing stirrer. Finally, the mixed biological material extruded from the floating mixing stirrer of multi-channel mixing unit I and the mixed biological material extruded from the floating mixing stirrer of multi-channel mixing unit II enter the converging channel. The converging channel has two inlets and one outlet. The material extruded through the outlet of the converging channel is in the form of double-layer concentric cylindrical filaments. If only multi-channel mixing unit I or multi-channel mixing unit II is activated, the material extruded through the outlet of the converging channel is in the form of a single-layer cylindrical filament.

[0015] Furthermore, the end effector also includes a cooling fan, a shock absorption device, and a print head. The shock absorption device is installed on the top of the print head to prevent the print head from colliding with the print head during printing. Specifically, the shock absorption device is a shock-absorbing spring connected to the concentric shaft of the print head. This shock-absorbing spring is connected in series and sleeved on the print head to ensure that the print head has a certain degree of flexibility in the vertical direction, thereby reducing the risk of vibration and collision. The temperature control module consists of a semiconductor temperature control shell covering the mixing unit and temperature sensors installed inside and outside the semiconductor temperature control shell. The cooling fan is installed on both sides of the semiconductor temperature control shell to dissipate heat and cool the outside of the semiconductor temperature control shell. The semiconductor temperature control shell and temperature sensors... All devices are connected to the control system, which controls the power of the input current of the semiconductor temperature control housing based on the data transmitted by the temperature sensor inside the semiconductor temperature control housing, thereby changing the temperature of the inner wall of the semiconductor temperature control housing. The semiconductor temperature control housing changes the internal temperature of the semiconductor temperature control housing through heat conduction, and achieves precise control of the internal temperature of the end effector through closed-loop feedback control. The control system controls the cooling fan based on the data transmitted by the temperature sensor outside the semiconductor temperature control housing, thereby controlling the temperature of the outer surface of the semiconductor temperature control housing. The material extruded from the outlet of the converging channel enters the printing needle and leaves the end effector from the printing needle, entering the support bath unit.

[0016] Furthermore, the number of camera modules is greater than or equal to 4 and they are evenly arranged around the circumference of the support bath unit. Each camera module includes a camera gimbal and a camera mounted on the camera gimbal. By manually adjusting the position of the camera gimbal, the printing area within the support bath unit is located at the center of the camera image.

[0017] The adjustment of the frequency and flow rate of alternating injection of biomaterial into the end effector based on the mixing effect is as follows: When the control system calculates that the average gray value of the current grayscale image is greater than the target grayscale threshold, the control system will reduce the flow ratio of bio-ink to gradient material. When the average gray value is less than the target grayscale threshold, the control system will increase the flow ratio of bio-ink to gradient material. When adjusting the flow ratio of bio-ink to gradient material, the flow rate of the mixed biomaterial output from the printing needle should be kept constant. If the grayscale dispersion of the current grayscale image is less than the target grayscale dispersion, the control system controls the injection system to increase the frequency of alternating injection of biomaterial, and the flow rate of the mixed biomaterial output from the printing needle remains constant. If the grayscale dispersion of the current grayscale image is greater than the target grayscale dispersion, the control system controls the injection system to decrease the frequency of alternating injection of biomaterial, and the flow rate of the mixed biomaterial output from the printing needle remains constant.

[0018] Furthermore, the number of ultraviolet laser modules is greater than or equal to 4 and they are evenly arranged around the circumference of the support bath unit. The ultraviolet laser modules are installed below the camera module and move with the camera module. Alternatively, multiple laser gimbals are also installed on the rack, and the ultraviolet laser modules are set on the laser gimbals. By manually adjusting the position of the laser gimbals, the ultraviolet laser modules can perform ultraviolet laser curing on the biological components.

[0019] The control system controls the power of the ultraviolet laser module. Specifically, if the edge feature information of the current grayscale photo does not match the target edge feature information of the printed biological model, the control system will increase the ultraviolet laser power of the ultraviolet laser module. The maximum value of the ultraviolet laser power is less than the value of the ultraviolet laser power set for the biosafety of the bio-ink.

[0020] The present invention also provides a method for achieving multi-material homogenization and continuous 3D printing with bio-gradients using the aforementioned device, comprising the following steps:

[0021] 1) The control system establishes a corresponding gradient field and constructs a target biological model based on the biological functionalization requirements, and slices the target biological model layer by layer; combined with the gradient field to be constructed, the control system performs synchronous layer-by-layer slicing calculation on the gradient field to be constructed, calculates the continuous gradient information of the motion trajectory of the printing needle through an interpolation algorithm, sets the parameters of the printed biological component and generates gradient printing trajectory information. The parameters of the printed biological component are the motion speed control parameters of the base plate system, the temperature control parameters in the end effector, the temperature control parameters of the base plate system, the feed speed control parameters and acceleration control parameters of the syringe, and the support bath material parameters; the continuous gradient information of each motion trajectory and the gradient printing trajectory information are fused to generate a gradient printing control program;

[0022] 2) Install different gradient materials and bio-inks into different syringes respectively. Control the syringes to inject gradient materials and bio-inks into the mixing unit through the control system, and expel the air in the mixing unit. At the same time, inject support bath material into the support bath unit, and turn on all syringes and enable the XYZ three-axis motion module.

[0023] 3) Set the needle length of the printing needle and the thickness of the base plate, and start the gradient printing control program to begin XYZ three-axis needle alignment to complete the position calibration of the printing needle and ensure that the needle does not collide during the entire printing process; the control system calculates the displacement compensation amount and the pre-mixing amount for each layer of printing based on the position of the support bath unit fed back by the camera module to solve the problem of mixing delay caused by switching between different materials; finally, the control system adjusts the total flow rate of the printing needle by sending the pre-extrusion function code and keeps the flow rate constant until the stable printing requirements are met, that is, uninterrupted printing and uniform thickness of the printed material;

[0024] 4) Start the actual printing process. During the printing process, the control system converts the gradient printing control program into control information of the actual output flow of each syringe and the trajectory information of the printing needle. It also adjusts the flow of each injection pump. The syringe squeezes the gradient material and bio-ink into the mixing unit. The mixing unit mixes the received gradient material and bio-ink and squeezes it from the printing needle into the support bath unit to form a biological component. The ultraviolet laser module solidifies the biological component. The camera takes grayscale photos of the biological component in real time and uploads them to the control system. The control system adjusts the frequency and flow of the alternating injection of biological material into the end effector and the ultraviolet laser power of the ultraviolet laser module based on the feedback of the grayscale photos until the printing is completed.

[0025] 5) After all the biofunctional gradient layers of the bio-component are printed, stop the feeding motion of all syringes and send a command through the control system to release the residual pressure in the tubing by reversing the injection pump motor, so that the internal pressure of the tubing is balanced with the atmospheric pressure; then send a command through the control system to control the XYZ three-axis motion module to return to the starting position; remove the support bath material to obtain the final biofunctional gradient component.

[0026] Furthermore, after printing is complete, the support bath material is heated and kept warm by the bottom temperature control platform, so that it changes from a suspended state to a liquid state, making it easier to remove the biological model components from the suspension.

[0027] The beneficial effects of the above embodiments of the present invention are as follows:

[0028] (1) One or more embodiments of the present invention can realize a method of printing biological components with complex spatial structures by mixing the biological ink and the biological functional gradient material with the liquid or low viscosity colloidal biological ink or the biological functional gradient material, and can achieve high efficiency and low cost manufacturing; the biological ink and gradient material available for printing are widely available, the process is stable and the manufacturing consistency is high, the printing accuracy of biological functional components is high, the printing efficiency is high and the cost is low.

[0029] (2) The present invention uses a support bath material as a support substrate for printing complex spatial structures, especially structures with a large aspect ratio. While depositing the material at any position in space, the bio-ink is coated and the position of the ink is maintained, which can realize the printing of continuous gradient components at any position in space.

[0030] (3) The printer of the present invention uses computer vision to monitor the printing status in real time and ensures the stability and consistency of printing by changing the laser power in real time. At the same time, it can allow users to monitor the printing status in real time and make adjustments, which has high automation and integration advantages.

[0031] (4) In the printing process, the present invention adopts a pre-crosslinking strategy between layers by adjusting the laser power, which can better improve the interlayer bonding strength of the biofunctionalized gradient component, improve the continuous gradient biofunctionality of the component, the manufacturing precision, and the mechanical strength of the component.

[0032] (5) This invention employs multiple collaboratively controlled injection pumps to inject biological gradient materials with different flow rates and proportions into a multi-channel mixing unit and perform uniform mixing. At the same time, a compensated printing method is used in the control of the printing trajectory to realize the gradient continuous printing of biological functional components and solve the problem of printing error accumulation caused by mixing delay. Furthermore, a floating discontinuous static mixing unit and PWM control are used to control the duty cycle and injection frequency of the injection mixing channel to achieve dynamic mixing. This solves the problem of agglomeration and uneven mixing of biological materials during mixing and can realize uniform mixing and continuous gradient printing of various biological gradient materials.

[0033] (6) The present invention can realize continuous gradient biomaterial deposition at any spatial location, with high manufacturing precision. By changing the nozzle diameter of different channels, it can realize the integrated molding and manufacturing of high-resolution continuous gradient biofunctional components across scales.

[0034] (7) The present invention adopts temperature coordinated control of multi-channel printing nozzle and base plate support bath printing platform, which can adjust the temperature parameters of printing nozzle and base plate in real time during the printing process. After printing ends and the nozzle returns to the origin, the support bath material can be heated and kept warm so that the biological gradient component can be taken out more quickly after printing. It has the advantages of integrated manufacturing and precise control of biological materials and continuous gradient materials, as well as the significant advantages of automation, integration, low cost and high production efficiency. Attached Figure Description

[0035] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0036] Figure 1 This is a front view of the overall device of the present invention, which employs an extrusion printing process using multi-channel homogenized gradient biomaterials according to one or more embodiments;

[0037] Figure 2 This is a left view of the overall device of the present invention, which employs an extrusion printing process using multi-channel homogenized gradient biomaterials according to one or more embodiments;

[0038] Figure 3 This is a three-dimensional schematic diagram of the overall equipment of the extrusion printing process using multi-channel homogenized gradient biomaterials according to one or more embodiments of the present invention.

[0039] Figure 4 This is a schematic diagram of the structure of the multi-channel mixing nozzle and temperature control system according to one or more embodiments of the present invention;

[0040] Figure 5 This is a schematic diagram of the multi-channel passive mixing nozzle structure according to one or more embodiments of the present invention;

[0041] Figure 6 This is a schematic diagram of the multi-channel passive mixing nozzle of the present invention, which achieves dynamic injection and mixing by adjusting the duty cycle and frequency of the PWM wave of the injected material according to one or more embodiments.

[0042] Figure 7 This is a schematic diagram of the process of dynamically mixing gradient materials and printing biofunctional gradient components using PWM control of multiple synergistic injection pumps according to one or more embodiments of the present invention.

[0043] The components include: 1. Top plate bracket, 2. Folding syringe pump fixing plate, 3. Coupling, 4. Angle iron fixing plate, 5. Syringe pump motor, 6. Syringe pump lead screw, 7. Syringe, 8. Injection needle, 9. Multi-channel mixing unit I, 10. Printer head temperature control module, 11. Printer head cooling fan, 12. Printer needle, 13. Support bath printing platform, 14. Base plate temperature control platform, 15. Z-axis motion module, 16. Multi-channel mixing unit II, 17. Printer head telescopic spring, 18. Base plate leveling spring, 19. Z-axis motor, 20. X-axis motion module, 21. Y-axis motion module, 22. Camera gimbal, 23. Gimbal telescopic spring, 24. Camera, and 25. Ultraviolet laser module. Detailed Implementation

[0044] The present invention will be further described and illustrated below with reference to specific embodiments. The embodiments described are merely examples of the content of this disclosure and do not limit the scope of the invention. The technical features of each embodiment in the present invention can be combined accordingly, provided that there is no mutual conflict.

[0045] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0046] For ease of description, the words "up," "down," "left," and "right" appearing in this invention only indicate that they are consistent with the up, down, left, and right directions of the accompanying drawings themselves. They do not limit the structure and are merely for the purpose of facilitating the description of this invention and simplifying the description. They do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0047] Terminology Explanation: The terms "installation," "connection," "linking," and "fixing" in this invention should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction relationship between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0048] To address the shortcomings of existing technologies, the purpose of this invention is to provide an integrated molding and manufacturing method particularly suitable for continuous gradient biofunctionalized components and complex spatial structures containing bioactive materials and polymer matrices. This invention solves the challenges of simultaneous printing of multiple materials and switching between different materials during the printing process of continuous biofunctionalized gradient components, ensuring printing consistency and precise, rapid forming. It also expands the application of in vitro 3D printing of continuously gradient biofunctionalized models in the medical field; improves the printing of spatially heterogeneous structures and ensures flexible gradient changes; increases the efficiency of manufacturing components with spatial gradients; and reduces manufacturing costs.

[0049] Example 1:

[0050] This embodiment provides a continuous 3D printing device for multi-material homogenized bio-gradient materials. Figure 3 A three-dimensional model of the device is shown. A schematic diagram of the overall 3D printing device is also provided. Figure 1 , Figure 2 As shown, the 3D printing device includes a top plate support 1, a folding injection pump fixing plate 2, a coupling 3, an angle iron fixing plate 4, an injection pump motor 5, an injection pump lead screw 6, a syringe 7, an injection needle 8, a multi-channel mixing unit I 9, a print head temperature control module 10, a print head cooling fan 11, a print needle 12, a support bath printing platform 13, a bottom plate temperature control platform 14, a Z-axis motion module 15, a multi-channel mixing unit II 16, a print head telescopic spring 17, a bottom plate leveling spring 18, a Z-axis motor 19, an X-axis motion module 20, a Y-axis motion module 21, a camera gimbal 22, a gimbal telescopic spring 23, a camera 24, and an ultraviolet laser module 25.

[0051] The injection system comprises an injection pump motor 5, an injection pump lead screw 6, a syringe 7, and an injection needle 8. The injection pump motor 5 is mounted on the injection pump lead screw 6, and the syringe 7 is mounted below the injection pump lead screw 6. The injection pump motor 5 drives the injection pump lead screw 6 to compress the syringe 7, and the material loaded in the syringe 7 is expelled through the injection needle 8 located on the syringe 7. In this invention, one syringe (7) contains the bio-ink, and the other syringes (7) contain gradient materials of different concentrations.

[0052] Among them, such as Figure 4 As shown, a three-axis desktop motion platform for a gradient bio-3D printer is illustrated. The X-axis motion module 20 and Y-axis motion module 21 are mounted on top of the support printing platform 13 via a fixed frame to control the movement of the printing nozzles in the horizontal XY directions; the Z-axis motion module 15 is fixed at the bottom of the frame. Figure 1As shown, multiple independently controlled injection pump motors 5 are fixed on the folding fixing plate 2, and the folding injection pump fixing plate 2 is fixed to the top of the printing platform through the coupling 3. Figure 3 The image also shows a detailed enlarged view of the end effector and the printing nozzle. The printing nozzle temperature control module 10 is installed on the outside of the multi-channel printing nozzle (printing needle) 12; the base plate temperature control platform 14 is installed on the top of the base plate platform; and the camera 24 and the ultraviolet laser module 25 are installed around the printing platform via a frame.

[0053] The X-axis motion module 20, Y-axis motion module 21, and Z-axis motion module 15 together form the XYZ three-axis module. Both the X-axis and Y-axis motion modules employ dual-motor parallel control to ensure high-precision motion control. The XYZ three-axis motion support uses a gantry-type high-precision displacement table, which can be driven by servo motors, stepper motors, or linear motors. In this embodiment, the XY-axis motion platform has a working stroke of 0-250mm, a positioning accuracy of no less than ±5μm, a repeatability of no less than ±3mm, and a maximum speed of 500mm / s. The Z-axis motion module has a working stroke of 0-300mm, a positioning accuracy of no less than ±3μm, a repeatability of no less than ±1μm, and a maximum speed of 300mm / s.

[0054] Furthermore, the Z-axis motion module 15 is mounted on the bottom of the printing platform via a frame, and the motion module and stepper motor control the movement of the printing platform along the Z-axis. A base plate temperature control platform 14 and a support bath printing platform 13 are mounted on the printing platform; a camera 24 and an ultraviolet laser curing module 25 are mounted on the side of the printing platform. Multiple collaboratively controlled injection needles 8 are connected to a multi-channel mixer via rubber tubing. Figure 5 (This is an enlarged view of the multi-channel mixing unit), with the inner channel 9 and the outer channel 16 connected to the printing needle 12.

[0055] The printing platform's base plate is equipped with a telescopic spring for leveling and a base plate temperature control system for insulating the support bath material, with an insulation range of 4-50℃. The flatness of the printing platform is no less than ±5μm, and it is equipped with a semiconductor temperature control system that enables rapid heating and cooling control. During printing, the support bath material can be placed on the base plate temperature control, and the printing needle can be inserted into the support bath to achieve embedded printing.

[0056] The support bath unit consists of a container with an open top and support bath material disposed within the container. The support bath unit is placed on a temperature control platform, which comprises multiple independently controlled miniature temperature control platforms arrayed on a base plate. Each temperature control platform or miniature temperature control platform is made of a semiconductor material with thermoelectric effect, and the temperature of the semiconductor can be controlled by changing the input current power. The thermoelectric semiconductor materials are lead telluride (PbTe), zinc antimonide (ZnSb), and silicon-germanium alloy (SiGe). The multiple independently controlled temperature control platforms collectively provide a stable printing temperature range for the support bath unit.

[0057] The semiconductor temperature control shell covering the mixing unit is used to control the printing temperature of the bio-ink. A temperature sensor is installed inside to monitor the temperature of the inner wall of the semiconductor in real time. A microcontroller (control system) controls the power of the input current to the semiconductor via a power amplifier, thereby controlling the temperature of the inner wall of the semiconductor. The controllable temperature of the inner wall of the semiconductor is maintained in the range of 10℃ to 40℃. This temperature is transferred to the mixing unit, which contains the bio-ink and bio-gradient material, through heat conduction, ensuring that the bio-ink and bio-gradient material are maintained within the temperature range required for the printing window. On the outer wall of the semiconductor shell, due to current heat loss, some heat is lost. Therefore, a cooling fan installed on the outside is used to ensure the safe and stable operation of the semiconductor. The semiconductor temperature control shell is made of a thermoelectric semiconductor material, such as lead telluride (PbTe), zinc antimonide (ZnSb), or silicon-germanium alloy (SiGe).

[0058] The base plate system also includes a base plate and a leveling spring located below the base plate. The leveling spring is used to keep the base plate in a horizontal state and prevent the printing pin from hitting the pin. The leveling spring also keeps the support bath unit in a horizontal state. The temperature control platform is placed on the base plate.

[0059] In this embodiment, the high-voltage DC power supply can output DC high voltage, AC high voltage, and pulsed high voltage, and can set the bias voltage, which is continuously adjustable from 0-2kV. The DC high voltage is 0-5kV, the output pulsed DC voltage is continuously adjustable from 0-±4kV, the output pulse frequency is continuously adjustable from 0-3000Hz, and the AC high voltage is 0-±4kV. The syringe pump controls the flow rate to be between 0.1 and 100 μl / min.

[0060] If the printed biomaterial is microscale, the nozzle can be replaced with a jet piezoelectric module for printing. If the printed material is macroscale, extrusion printing can be used. In multi-channel systems, microsphere units can be used to encapsulate microscale materials, and extrusion printing can be used to shape the microscale materials.

[0061] In this invention, the biogradient material (biomaterial) refers to a mixture of cell-based bio-ink and a biocompatible gradient material. For example, the gradient material can be composed of hydrogels and collagen with different percentages, which can change the physical and chemical properties of the overall model structure. For example, by controlling the mixing of hydrogels and cells with different percentages for printing, the overall elastic modulus and compressive modulus of the final printed model can be controlled and adjusted.

[0062] This embodiment introduces a support bath material. Unlike traditional printing methods using materials and processes, where the composition and properties of a single material or composite material remain largely unchanged during printing, the optimized printing process parameters are generally applicable throughout the entire printing process. Addressing the significant printing challenges posed by the real-time changes in the composition and physicochemical properties of continuously functionally graded materials / structures during printing, this embodiment proposes introducing a constrained sacrificial support bath material. This allows for the deposition of bio-gradient materials at arbitrary locations in three-dimensional space, enabling the printing of spatial structures with wide aspect ratios.

[0063] In this embodiment, the support bath material is a Fresh support bath material, which is made by treating gelatin and calcium chloride solution.

[0064] Its advantages and significant effects are: 1) With the assistance of the support bath material, it overcomes the problem of poor printing stability and consistency caused by the continuous changes in material composition / components and physicochemical properties during the printing process of continuous functional gradient materials / structures. The printing process parameters have a very wide process window, which can ensure the printing accuracy, geometry, surface quality and continuous gradient performance.

[0065] 2) Utilizing a constrained sacrificial layer structure to assist in the forming of arbitrarily complex functionally graded 3D structures. Since the current layer is not fully cured during printing, precise geometric control is difficult to achieve without the assistance of a constrained sacrificial layer. This is especially beneficial as it solves the problem of maintaining the printed geometry when the already formed layer is in an incompletely cured state. It can also precisely form low-viscosity photosensitive resin materials; and assist in the forming of complex internal structures, overhanging structures, thin-walled structures, and inverted structures, etc.

[0066] 3) Improved printing accuracy and consistency. The optimized process window is applicable over a very wide range. Utilizing the support bath structure ensures that the thickness of each layer of the printed functionally graded material / structure is the set thickness. Regardless of whether the printed individual functionally graded part is in a low-filler functionally graded region or a high-filler functionally graded region, the constrained sacrificial layer structure ensures the same thickness (either a set variable thickness or an adaptive thickness). In particular, the printed functionally graded parts exhibit excellent consistency across different regions of the same part, the same batch, and different batches.

[0067] This embodiment can be applied to many fields and industries such as aerospace, biomedicine, ultra-high voltage, nuclear power, energy, composite materials, flexible electronics, wearable devices, electronic skin, soft robots, new materials, and biomimetic manufacturing.

[0068] This invention is achieved through the following technical solution:

[0069] (1) A method of multi-mixing material collaborative control and printing path difference compensation mixing is adopted to solve the problems of delayed mixing and uneven mixing when switching between different materials. In the planning of the printing path, the difference compensation method is adopted to pre-mix the printing trajectory that needs to be mixed with gradient, and the gradient field to be printed is re-optimized to match the biological model file to be printed. First, the host computer system optimizes the model file, slices the optimized model, and generates the original printing trajectory code. A gradient mapping relationship is established between the gradient model of the required components and the biological model to be printed, and the gradient field to be implemented is mapped onto the biological model to be printed. First, based on the pre-set gradient field information, the gradient data of each trajectory is calculated and converted into actual output flow control information, which is fed back to the microcontroller to adjust the flow control and flow rate control of each injection pump. Finally, during the printing process, the extrusion rate of each independently controlled injection pump and the mixing ratio between each gradient material are dynamically adjusted in real time to realize the construction and printing of continuous gradient models at any position in space. Finally, by setting the premixed material range on the host computer, the control system calculates the displacement compensation amount of the nozzle movement to compensate for the printing delay, and conducts a trial extrusion test on the first layer of material. The printing quality and mixing effect of the first layer of gradient material are judged by the auxiliary observation camera, and the compensation amount parameters are adjusted by the host computer. After adjusting the compensation parameters, printing begins.

[0070] (2) A multi-channel mixing unit is used to perform real-time mixing and switching of multiple materials. The unit is internally filled with a floating, discontinuous mixing device that can float and stir the materials while they are being injected. The multiple materials are injected alternately during the printing process by controlling the duty cycle and injection frequency via PWM (e.g., ...). Figure 6As shown in the diagram, this allows for dynamic mixing within a static mixing channel. The multi-channel mixing unit can print in multiple channels, achieving the effect of cross-linked material coating biomaterials. This allows low-viscosity biomaterials to be encapsulated by high-viscosity coating materials, ensuring structural fidelity and printing accuracy. The overall mechanism enables material mixing with arbitrary degrees of freedom and high fidelity of low-viscosity biomaterials, improving the integrated forming accuracy of low-viscosity bio-gradient components.

[0071] (3) The introduction of a support bath material. Unlike traditional 3D printing technology, which requires maintaining the composition and properties of materials during printing, the optimized printing process parameters have universality. For the manufacture of complex spatial heterogeneous structural models with large aspect ratios, a support bath is used to support the printed biomaterials, ensuring that the bio-components do not collapse during the entire printing process. Simultaneously, with the auxiliary support of the support bath, the printed biomaterials can be well encapsulated within the support bath, preventing issues of poor printing stability and consistency caused by mixing different materials or switching between materials during printing. Therefore, the process parameters for multi-material gradient printing using a support bath have a wider printing window, allowing for the selection of support bath materials in more temperature ranges, increasing the variety of support bath materials applicable to printing, and better ensuring the accuracy, stability of the printed shape, surface quality, and continuous gradient performance of the entire bio-component during printing. Furthermore, by using a layer-by-layer pre-curing and cross-linking method during printing, it is possible to further ensure that the low-viscosity, high-bioactivity gradient components encapsulated in the support bath can form more complex overhanging structures, thin-walled structures, and oblique-cut structures.

[0072] (4) By using computer vision to monitor the printing process and adjusting the power of the ultraviolet laser according to the curing quality of the material, better bioactivity and forming quality can be ensured. This can greatly reduce the need to adjust printing process parameters and ensure the stability and consistency of multiple printings. Moreover, pre-curing each layer helps to improve the bonding strength between gradient layers, thus preventing problems such as poor interlayer bonding strength, weak continuous gradient biofunctionality, and poor printing accuracy when forming large-sized structural parts.

[0073] Example 2:

[0074] This embodiment provides a 3D printing method for the integrated manufacturing of continuous functionally graded materials and structures, using the printing apparatus described in Embodiment 1, such as... Figure 7 As shown, it includes the following steps:

[0075] (1) Model Setup. Determine the geometry of the printed part;

[0076] (2) Model information processing. Determine the geometric information (path, layer thickness, etc.) of each layer and generate print data files;

[0077] (3) Pre-printing preparation: Determine the material ratio and pre-treat the gradient bio-ink and printing bio-ink in multiple syringes, as well as the support bath material in the printing platform; input and set the printing feed rate, printing speed, substrate temperature, nozzle temperature, printing flow rate, etc. through the host computer;

[0078] (4) Printing functional gradient structure: Multiple coordinated injection pumps inject bio-gradient material and bio-ink into a multi-channel mixer alternately or synchronously according to the instructions of the host computer, and print in a support bath.

[0079] (5) After each layer is printed, the ultraviolet laser module pre-cures and cross-links the printed area, while the camera monitors the cured area in real time and adjusts the laser power accordingly. After the layer is printed, the Z-axis descends by one layer thickness before printing the next layer. This process is repeated until all layers are printed.

[0080] (6) Post-printing processing. After printing, the base plate temperature control starts to heat up and maintain the temperature until the support bath material fuses, while the ultraviolet laser completely cures the printed bio-gradient component. After curing is complete, all devices and modules are turned off, the printed functional gradient structure with auxiliary support structure is removed, and then the auxiliary support structure is separated from the functional gradient sample (peeling, dissolving in a special solution or hot water, etc.).

[0081] The printing functional gradient structure can be configured with multiple layers of the same material information and gradient cloud map that integrates the gradient field to be printed with the printing model, according to the actual printing needs (printing efficiency and actual printing requirements or accuracy requirements, etc.).

[0082] This embodiment uses GelMA (Gelatin Methacryloyl) and HAMA (Hyaluronic Acid Methacrylate) as gradient mixing materials, and GelMA as a bio-ink material as an example (the bio-ink may not contain cells initially, and cell loading may be added after the biological component is printed; alternatively, the bio-ink may contain cells before printing). It demonstrates a printing method for the integrated manufacturing of continuous biofunctionalized gradient materials and complex spatial structures, and explains the specific process steps:

[0083] Step 1: Prepare the print data file. The STL model file is sliced ​​to generate the print trajectory. Simultaneously, the gradient field is sliced, and the sliced ​​gradient field model is merged with the print trajectory. The gradient printing difference algorithm and print trajectory edge optimization are then used to generate the final code for the gradient print trajectory.

[0084] Based on the physical gradient field requirements for printing, the concentration of gradient biomaterial in multiple collaboratively controlled injection pumps is continuously varied from 0% to 20%. HAMA (hybrid HAMA) at concentrations of 4%, 8%, 12%, 16%, and 20% is injected into the first through fifth injection pumps, respectively. GelMA (5%) is injected into the sixth injection pump, followed by 5% GelMA and bio-ink containing cell A (fibroblasts) in the seventh pump, and finally 5% GelMA and bio-ink containing cell B (hepatic stellate cells) in the eighth pump. All syringes are connected to a multi-channel mixing unit using rubber tubing. A stainless steel nozzle (model 21G, 810μm outer diameter, 510μm inner diameter) is installed at the end of each channel, with a printing height of 0.05mm and a line spacing of 300μm.

[0085] Step 2: Print preprocessing.

[0086] (2-1) Prepare the support bath material. Take out the geltain solution (mass-volume ratio of 8%-10%) that has been refrigerated overnight and put it into a mixer to crush it (stirring time is 50s-60s). Take it out and put it into a centrifuge for 7min. After centrifugation, take the supernatant as the support bath and inject it into the support bath printing platform.

[0087] (2-2) Pre-extrusion test flow rate: Turn on the temperature control system located in the multi-channel mixing unit and the base plate temperature control system of the support bath printing platform. Set the temperature at the printing nozzle to 25℃ and the base plate temperature to 10℃. The host computer sends a command to control the injection pump to start working. Multiple injection pumps simultaneously inject bio-gradient material and bio-ink containing cells and cell culture medium into the passive mixing channel. The camera starts to observe the droplet state of the printing nozzle and controls and adjusts the output flow rate of the injection pump until the droplet becomes spindle-shaped, which is the optimal printing state. Turn on the observation camera and ultraviolet laser module to standby state, and turn on each XYZ motion module to enable state to complete all the preparation work required for printing.

[0088] Step 3: Printing of biofunctionalized continuous gradient structures.

[0089] (3-1) Input the gradient printing Gcode into the host computer, set the pre-extrusion flow rate information, printing layer information, feeding time, and calculate the ratio and flow rate information of different biological gradient materials, including mass ratio or volume ratio, according to the physical gradient field to be realized.

[0090] (3-2) Printing biofunctionalized gradient layers: Gradient biomaterials are injected into a multi-channel mixer via multiple coordinated injection pumps. The duty cycle and frequency of the injected materials are changed by controlling the duty cycle and frequency of the injection pump motors. The host computer sends a printing start command to the slave computer, which controls the XYZ three-free motion platform to start printing. For the continuous gradient structure to be deposited in the current printing layer, different proportions of biogradient materials are injected into the passive mixing unit according to a preset ratio. During the injection process, the biogradient materials are injected alternately to achieve dynamic mixing in the passive mixing unit. The gradient printing of the current layer is completed according to the preset trajectory of the initial layer.

[0091] (3-3) The observation camera determines the position of the current layer through a computer vision positioning algorithm; the ultraviolet laser module pre-cures and cross-links the current layer, and adjusts the laser power according to the printing quality of the current layer obtained by the camera to complete the pre-curing of the current layer; the Z-axis motion module controls the printing platform to move down one layer, and the host computer controls the motion module to move according to the Gcode code of the next layer, depositing biological gradient material in the second layer; the camera positions the biological material of the second layer and controls the ultraviolet laser module to pre-cures and cross-link the material of the second layer; the gradient printing of the current layer is completed according to the preset trajectory of the second layer.

[0092] Step 4: Repeat the above steps until all layers have been printed and pre-cured for cross-linking.

[0093] Step 5: Post-printing processing.

[0094] After all printing layers have been printed and pre-cured, the XY-axis free motion module controls the printing nozzle to move to the origin position, and the Z-axis free motion module controls the support bath printing platform to move to the lowest position. An auxiliary observation camera determines the position of the bio-gradient component in the support bath and controls the ultraviolet laser module to perform final curing and cross-linking of the bio-gradient component. After final curing and cross-linking, the substrate temperature control system heats and maintains the temperature until the support bath material melts. The printed bio-gradient component is then washed out of the support bath material, yielding the finished biofunctionalized gradient component.

[0095] This embodiment employs a pre-curing crosslinking method, which improves the bonding strength between bio-gradient layers. Supported by a support bath material, continuous gradient biomaterials are deposited at arbitrary spatial locations, enabling the integrated manufacturing of bio-gradient components with a large aspect ratio. This effectively improves the manufacturing efficiency of printed bio-gradient components and enhances the interlayer bonding strength and continuous gradient performance of the biofunctionalized components. Specifically, each layer of biomaterial is pre-cured and crosslinked simultaneously with printing, and the entire bio-component is fully cured and crosslinked after all layers are completed.

[0096] This embodiment employs a continuous gradient mixing method, achieving differential mixing within different mixing intervals by continuously mixing biomaterials at gradients of 4%, 8%, 12%, 16%, and 20%. It calculates the injection ratio and flow rate of each gradient material required for the intermediate value and adjusts the injection flow rate and start / stop control of multiple coordinating injection pumps in real time during printing, thereby achieving continuous gradient mixing within any concentration range. Furthermore, in the multi-channel mixing unit, a floating, discontinuous surface-structured passive mixing stirrer is used. While injecting the bio-gradient material, the stirrer moves up and down, dynamically mixing the bio-gradient material through alternating injection of bio-mixing material, achieving uniform mixing of the bio-gradient material, and ensuring that the biomaterial at the nozzle has good continuous biofunctionalization gradient performance.

[0097] Example 3:

[0098] Furthermore, at the end of the multi-channel mixing unit, a syringe nozzle for printing is connected. The outermost layer of the multi-channel unit is printed with a gradient material encapsulating bio-ink, while the inner layer is bio-ink containing cells, thus achieving the deposition of a bio-gradient material encapsulating bio-ink in space. While printing each layer, the camera locates the position of the current printed layer and controls the ultraviolet laser module to solidify and cross-link the current layer. While printing each layer, the injection flow rate and start / stop of different syringe pumps are changed, thereby controlling the content of magnetic nanoparticles in different regions of the material to achieve continuous gradient changes of the magnetic material at any position in space.

[0099] A camera mounted on the printing platform tracks the printed components in real time and captures grayscale images of them. By calculating the grayscale value of each frame of the biological component image, the mixing effect is determined. An ultraviolet laser is used to pre-cur and cross-link the printed area, while simultaneously detecting the diameter and forming quality of the extruded filaments. This information guides the laser power adjustment to ensure good printing performance and bioactivity.

[0100] Repeat the above operations until all biofunctionalized gradient layers are printed. The XY-axis free motion module controls the printing nozzle to move to the origin position, and the Z-axis free motion module controls the support bath printing platform to move to the lowest position. The auxiliary observation camera determines the position of the bio-gradient components in the support bath and controls the ultraviolet laser module to perform final curing and cross-linking of the bio-gradient components. After the final curing and cross-linking is completed, the substrate temperature control system heats up and maintains the temperature until the support bath material melts. The printed bio-gradient components are washed out of the support bath material to obtain the finished biofunctionalized gradient components.

[0101] The embodiments described above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for bio-graded multi-material blending and continuous 3D printing using a multi-material blending and continuous 3D printing device, the method comprising: The multi-material mixing and continuous 3D printing device comprises a rack, an injection system, an end effector, a support bath unit, a bottom plate system, an XYZ three-axis motion module, a camera module, an ultraviolet laser module (25), and a control system; the end effector is internally provided with a mixing unit; ​ The injection system is fixed on the rack and connected with the end effector, and different biomaterials are alternately injected into the mixing unit in the end effector; the mixing unit mixes the injected biomaterials, and the mixed biomaterials are extruded through the outlet of the end effector; the support bath unit is located below the end effector, and the end effector extrudes the mixed biomaterials into the support bath unit, and the mixed biomaterials form a biological component with a biological gradient in the support bath unit, wherein the biomaterials comprise biological ink and gradient materials with different concentrations; The XYZ three-axis motion module is installed on the rack and connected with the control system, and is used to drive the bottom plate system to move in the Z direction and drive the end effector to move laterally or longitudinally in the horizontal direction; The camera module is installed on the rack and connected with the control system, and the camera module tracks and takes gray-scale photos of the biological component formed in the support bath unit in real time, the control system calculates the gray-scale values of each frame of the gray-scale photos to judge the mixing effect of the materials, and the frequency and flow of the biomaterials injected into the end effector are corrected according to the mixing effect; The ultraviolet laser module (25) is arranged around the support bath unit and is used to cure the biological component by ultraviolet laser, the ultraviolet laser module (25) is connected with the control system, and the control system controls the power of the laser of the ultraviolet laser module (25) to adjust the pre-curing quality of the biological component; The end effector further comprises a temperature control module, the temperature control module is used to ensure the temperature of the mixed biomaterials constant and ensure the biological activity of the biomaterials; the bottom plate system comprises a temperature control platform, the support bath unit is placed on the temperature control platform, and the temperature control platform is used to control the temperature of the support bath unit constant during the printing process; The injection system comprises a plurality of injection pump motors (5), a plurality of injection pump screws (6), a plurality of injectors (7), and a plurality of injection needles (8), the injection pump motor (5) drives the injection pump screw (6) to extrude the injector (7), and the materials loaded in the injector (7) are extruded through the injection needle (8) located on the injector (7); one of the injectors (7) stores the biological ink, and the remaining injectors (7) respectively store gradient materials with different concentrations; The mixing unit comprises a multi-channel mixing unit I (9), a multi-channel mixing unit II (16) and a converging channel, the number of channels of the multi-channel mixing unit I (9) and the number of channels of the multi-channel mixing unit II (16) are less than or equal to the number of injectors (7); the multi-channel mixing unit I (9) and the multi-channel mixing unit II (16) are structurally identical, and each comprises a floating mixing stirrer, the injection system injects biological materials into the mixing unit through a plurality of hoses, the biological materials enter the floating mixing stirrer through the hoses, and the mixed biological materials are extruded from the outlet of the floating mixing stirrer; finally, the mixed biological materials extruded from the floating mixing stirrer of the multi-channel mixing unit I (9) and the mixed biological materials extruded from the floating mixing stirrer of the multi-channel mixing unit II (16) enter the converging channel respectively; the converging channel has two inlets and one outlet, and the material extruded through the outlet of the converging channel is in the form of double-layer concentric cylindrical filaments; if only the multi-channel mixing unit I (9) or the multi-channel mixing unit II (16) is started, the material extruded through the outlet of the converging channel is in the form of single-layer cylindrical filaments; The method comprises the following steps: 1) The control system establishes a corresponding gradient field with physical property changes and chemical property changes according to the biological functionalization requirements, constructs a target biological model, and slices the target biological model layer by layer; in combination with the gradient field to be constructed, the control system performs synchronous layer-by-layer slicing calculation on the gradient field to be constructed, calculates the continuous gradient information of the motion trajectory of the printing needle (12) through an interpolation algorithm, sets the parameters of the printed biological component, and generates gradient printing trajectory information, wherein the parameters of the printed biological component are the motion speed control parameters of the base plate system, the temperature control parameters in the end effector, the temperature control parameters of the base plate system, the feed speed control parameters and acceleration control parameters of the injector (7), and the support bath material parameters; the gradient printing control program is generated by fusing the continuous gradient information of each motion trajectory and the gradient printing trajectory information; 2) Different gradient materials and biological inks are respectively installed in different injectors (7), the control system controls the injectors (7) to inject the gradient materials and biological inks into the mixing unit, and exhausts the air in the mixing unit; at the same time, the support bath material is injected into the support bath unit, and all the injectors (7) are started and the XYZ three-axis motion module is enabled; 3) The needle length of the printing needle (12) and the thickness of the base plate are set, and the gradient printing control program is started, and the XYZ three-axis is started to calibrate the position of the printing needle (12), so as to prevent the needle from being stuck during the whole printing process; the control system calculates the displacement compensation amount and the premixing amount of each layer according to the position of the support bath unit fed back by the camera module, so as to solve the premixing delay problem caused by the switching of different materials; finally, the control system adjusts the total flow of the printing needle (12) through the sending of the pre-extrusion function code, and keeps the flow constant until the stable printing requirements are met, that is, the printing is uninterrupted and the printed material is uniform in thickness. 4) Start formal printing, during the printing process, the control system converts the gradient printing control program into the control information of the actual output flow of each injector (7) and the trajectory information of the printing needle (12), and adjusts the flow of each injection pump, the injectors (7) extrude the gradient material and the biological ink into the mixing unit, the mixing unit mixes the received gradient material and biological ink and then extrudes it from the printing needle (12) into the support bath unit to form a biological component, the ultraviolet laser module (25) cures the biological component, the camera takes a gray-scale photo of the biological component in real time and uploads it to the control system, the control system adjusts the frequency and flow of the biological material alternately injected into the end effector and the ultraviolet laser power of the ultraviolet laser module (25) according to the feedback of the gray-scale photo until the printing is completed; 5) After the printing of all the biological functional gradient layers of the biological component is completed, stop the feeding movement of all the injectors (7), and send instructions through the control system to release the residual pressure in the hose by reversing the injection pump motor (5), so that the internal pressure of the hose is balanced with the atmospheric pressure; then send instructions through the control system to control the XYZ three-axis motion module to return to the initial position; remove the support bath material to obtain the final biological functional gradient component.

2. The method of claim 1, wherein, The gradient material is a hydrogel with different concentrations, and the biological ink is a uniform mixture of fibroblast culture medium and fibroblasts, or a uniform mixture of hepatic stellate cell culture medium and hepatic stellate cells.

3. The method of claim 1, wherein, The XYZ three-axis motion module includes an X-axis motion module, a Y-axis motion module, and a Z-axis motion module, all of which are connected to the control system; the Z-axis motion module is installed on the rack and connected to the bottom plate system, receiving signals from the control system to drive the bottom plate system to move in the Z direction; the support bath unit moves with the bottom plate system; the Y-axis motion module and the X-axis motion module are also installed on the rack and both receive signals from the control system to drive the end effector to move horizontally or vertically in the horizontal direction.

4. The method of claim 1, wherein, The end effector further comprises a heat dissipation fan (11), a damping device, and a printing needle (12); the damping device is installed on the top of the printing needle (12) to prevent the printing needle (12) from being damaged during printing; the temperature control module is composed of a semiconductor temperature control shell covering the mixing unit and temperature sensors installed inside and outside the semiconductor temperature control shell; the heat dissipation fan (11) is installed on both sides of the semiconductor temperature control shell to dissipate heat from the outside of the semiconductor temperature control shell; the semiconductor temperature control shell and the temperature sensors are connected to the control system; the control system controls the power of the input current of the semiconductor temperature control shell according to the data transmitted by the temperature sensor inside the semiconductor temperature control shell, changes the temperature of the inner wall of the semiconductor temperature control shell, and realizes accurate control of the temperature inside the end effector through closed-loop feedback control; the control system controls the heat dissipation fan (11) according to the data transmitted by the temperature sensor outside the semiconductor temperature control shell, and then controls the temperature of the outer surface of the semiconductor temperature control shell; the material extruded from the outlet of the converging channel enters the printing needle (12) and leaves the end effector from the printing needle (12) into the support bath unit.

5. The method of claim 1, wherein, The support bath unit is composed of a container with an open top and a support bath material arranged in the container, The bottom plate system further comprises a bottom plate and leveling springs located below the bottom plate, which are used to keep the bottom plate in a horizontal state and prevent the printing needle from being damaged during printing, and also keep the support bath unit in a horizontal state through the leveling springs; the temperature control platform is placed on the bottom plate.

6. The method of claim 4, wherein, The number of camera modules is greater than or equal to 4 and is arranged uniformly along the circumference of the support bath unit; the camera module comprises a camera holder (22) and a camera (24) arranged on the camera holder (22); by manually adjusting the position of the camera holder (22), the printing area in the support bath unit is located at the center of the camera image; The frequency and flow rate of the biological material injected into the end effector are adjusted according to the mixing effect, specifically: when the control system calculates that the average gray value of the current gray photo is greater than the target gray threshold, the control system will reduce the flow rate ratio of biological ink and gradient material; when the average gray value is less than the target gray threshold, the control system will increase the flow rate ratio of biological ink and gradient material; when adjusting the flow rate ratio of biological ink and gradient material, the flow rate of the mixed biological material output by the printing needle (12) should be constant; if the gray dispersion degree of the current gray photo is less than the target gray dispersion degree, the control system controls the injection system to increase the frequency of the syringe (7) injecting biological material, and the flow rate of the mixed biological material output by the printing needle (12) is constant; if the gray dispersion degree of the current gray photo is greater than the target gray dispersion degree, the control system controls the injection system to reduce the frequency of the syringe (7) injecting biological material, and the flow rate of the mixed biological material output by the printing needle (12) is constant.

7. The method of claim 6, wherein, The number of the ultraviolet laser modules (25) is greater than or equal to 4 and is arranged uniformly along the circumference of the support bath unit, the ultraviolet laser modules (25) are installed below the camera module and move with the camera module, or a plurality of laser gimbals are further installed on the rack, the ultraviolet laser modules (25) are arranged on the laser gimbals, and the position of the laser gimbals is adjusted manually to make the ultraviolet laser modules (25) perform ultraviolet laser curing on the biological component; The control system controls the power of the laser of the ultraviolet laser module (25), specifically: if the edge feature information of the current gray photo does not match the target edge feature information of the printed target biological model, the control system will increase the ultraviolet laser power of the ultraviolet laser module (25); the maximum value of the ultraviolet laser power is less than the value of the ultraviolet laser power set by the biological safety of the biological ink.

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