A photocuring apparatus for 3D printing hydrogel structures and a manufacturing method thereof

Abstract

This invention provides a photopolymerization device for 3D printing hydrogel structures, comprising a printing substrate with surface modification for constraining a hydrogel solution; a digital light processing (DLP) device including a drive unit, an optical engine, and a tensioning unit, wherein the drive unit controls the up-and-down movement of the optical engine and the tensioning unit; a release film for separating the hydrogel solution from the printing substrate and constraining its shape; a DLP printing area consisting of the optical engine, the tensioning unit, and the printing substrate; the DLP device constrains the hydrogel solution through the release film and the surface of the printing substrate, controlling the deformation of the hydrogel solution droplets as the tensioning unit moves to match the layer-by-layer accumulation process of the DLP on the printed sample; and a manufacturing method based on the photopolymerization device, which controls the shape of the hydrogel solution on the printing substrate to form a high-precision 3D hydrogel structure by layer-by-layer curing.

Description

Technical Field

[0001] This invention relates to the field of photopolymer 3D printing technology, and more particularly to a liquid-constrained digital light processing (LC-DLP) technology. Background Technology

[0002] Hydrogels are widely used in flexible electronics and bioengineering due to their excellent biocompatibility and tunable mechanical properties. Photocurable hydrogels, in particular, can be used to construct high-resolution 3D models with complex structures through digital light processing (DLP). This offers significant advantages in the fabrication of bio-devices such as micro-tissue models, flexible sensors, and microfluidic chips. However, most photocurable hydrogel formulations contain water, which leads to water evaporation and solute precipitation in the resin bath. During the printing process, the hydrogel sample may dehydrate, causing sample deformation, thus limiting the printing accuracy and material utilization efficiency.

[0003] In traditional DLP printing, an excess of resin solution is added to cover the entire resin tank to complete the printing process. The space between the printing platform and the release film interface, along with the surface tension of the resin solution, provides some constraint. Utilizing this principle, a "bottom-up" DLP device with a scaled-down printing platform and no resin tank structure can create 3D models from trace amounts of resin solution. However, when printing flexible hydrogel samples using "bottom-up" DLP, the samples are difficult to shape due to surface tension and their own weight, requiring dynamic support from a yield-stress fluid to assist in the shaping of flexible samples. Furthermore, low-stiffness structures printed using typical flexible hydrogels are difficult to shape in the "bottom-up" DLP process; hydrogel samples with high water content are prone to dehydration and severe deformation.

[0004] In the bottom-up, layer-by-layer DLP printing process, the printing platform moves repeatedly up and down. As the hydrogel sample moves with the platform, it detaches from the uncured solution and is directly exposed to air. This causes the cured sample to dehydrate during printing, leading to misalignment with the subsequent printed model. This presents numerous challenges for DLP equipment with resin tank designs when printing hydrogel samples. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a photopolymerization device and its manufacturing method for 3D printing hydrogel structures, which improves the utilization efficiency of the hydrogel solution and reduces sample dehydration and deformation during the printing process.

[0006] To address the aforementioned technical problems, this invention provides a photopolymerization apparatus for 3D printing hydrogel structures, comprising:

[0007] The printing substrate is hydrophilic or hydrophobic at its liquid contact interface to improve the ability to control the solution morphology. The printing substrate is used to constrain the hydrogel solution.

[0008] A digital light processing (DLP) device includes a drive unit, an optomechanical system, and a tensioning device, wherein the drive unit controls the up-and-down movement of the optomechanical system and the tensioning device;

[0009] Release membranes are used to separate hydrogel solutions from the printing substrate and constrain their morphology;

[0010] The DLP printing area consists of an optical engine, a tensioning device, and a printing substrate;

[0011] The digital light processing (DLP) device uses a release film and a printing substrate to constrain the photocuring of a hydrogel solution. It controls the deformation of the hydrogel solution droplets as the tensioning device moves to match the DLP process of layer-by-layer accumulation of the printed sample.

[0012] In a preferred embodiment, the hydrophilic treatment is performed by plasma treatment;

[0013] The hydrophobic treatment is performed by spraying with a nano-silicon spray.

[0014] In a preferred embodiment, the release film is kept flat by a tensioning device, which is used to control the shape of the liquid hydrogel solution.

[0015] In a preferred embodiment, the tensioning device tensions the release film into a shape with a flat center and a 17° angle around the edges.

[0016] In a preferred embodiment, the middle plane of the release film is a printing area, which is hydrophilically treated to improve the wettability of the hydrogel solution;

[0017] The hydrophilic treatment of the printing area is performed using a plasma treatment machine.

[0018] This invention also provides a method for manufacturing hydrogel structures for 3D printing, using the aforementioned photopolymerization equipment; the manufacturing method includes the following steps:

[0019] Step 1: Modify the surface of the printing substrate to give it hydrophilic or hydrophobic properties; assemble the digital light processing (DLP) device and release film;

[0020] Step 2, Printing Start-up Stage: Add a quantitative amount of hydrogel solution, which includes flexible hydrogel solution and rigid hydrogel solution, and mix them as needed; add the flexible hydrogel solution and rigid hydrogel solution to the printing substrate as needed; add the hydrogel solution in batches, and wet the printing substrate and release film before each addition of new solution;

[0021] Step 3: The hydrogel solution is cured layer by layer by exposure using a digital light processing (DLP) device to form a 3D structure;

[0022] Step 4: Use a release membrane to separate the cured liquid hydrogel structure.

[0023] In a preferred embodiment, step 3 includes the following process:

[0024] Step a, Descent stage: The tensioning device presses down the hydrogel solution to the specified height and squeezes out excess hydrogel solution into the storage area;

[0025] During the first layer of printing, the descent process constrains the solution in the printing area to a thin layer of the first layer height, and the remaining solution is squeezed into the reservoir area; the descent process descends at a speed of 0.1 mm / s for the last 5 mm and waits for 10 seconds to ensure that the solution flows level; in subsequent printing, it descends at a speed of 0.3 mm / s to constrain the solution to the specified height.

[0026] Step b, Exposure stage: The pattern of the optical-mechanical projection model slices and the hydrogel solution in the printing area undergo cross-linking;

[0027] Step c, rising stage: The tensioning device slowly rises by 1 mm at a speed of 0.3 mm / s, causing the hydrogel solution in the storage area to rewet the release film surface;

[0028] Step d, Printing completion stage: Repeat steps a, b, and c until all model slice patterns are projected, and finally lift the tensioning device to complete the preparation of the printed part.

[0029] In a preferred embodiment, the tensioning device tensions the release film into a flat plane in the middle and an inclined plane at 17° around the edges. The liquid storage area is disposed on the inclined plane at 17° around the edges, and the printing area is disposed on the flat plane in the middle.

[0030] In a preferred embodiment, the flexible hydrogel solution is a flexible AAm solution, and the rigid hydrogel solution is a rigid PEGDA solution; the flexible AAm solution is used to prepare microheart models and flexible sensors, and the rigid PEGDA solution is used to prepare micropatterns and microfluidic chips.

[0031] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0032] 1. A constrained solution digital light processing (LC-DLP) process is employed, utilizing a surface-modified substrate and the surface tension of the liquid. This "top-down" DLP method can progressively solidify and accumulate small amounts of hydrogel solution into controllable 3D structures. By adding formulated flexible and rigid hydrogel solutions as needed, LC-DLP has been used to fabricate high-precision microstructure models, flexible sensors, and microfluidic chips with complex 3D structures, achieving efficient utilization of small amounts of hydrogel solution.

[0033] 2. By utilizing a surface-modified substrate and a liquid surface tension constraint solution, referred to as LC-DLP process, the utilization efficiency of hydrogel solution is improved and sample dehydration deformation during printing is reduced, thereby improving the fidelity and success rate of printed samples. Attached Figure Description

[0034] Figure 1 This is a diagram of a photocuring device in a preferred embodiment of the present invention;

[0035] Figure 2 This is an enlarged view of the DLP printing area in a preferred embodiment of the present invention;

[0036] Figure 3 This is a cross-sectional view of the tensioning device in a preferred embodiment of the present invention;

[0037] Figure 4 This is a model diagram of the tensioning device in a preferred embodiment of the present invention;

[0038] Figure 5 (ac) is a view of the untreated 304 stainless steel surface in a preferred embodiment of the present invention;

[0039] Figure 5 (df) is a surface view of 304 stainless steel after hydrophobic treatment in a preferred embodiment of the present invention;

[0040] Figure 6 (i-v) is a flowchart of the layer-by-layer exposure and curing of the hydrogel solution in a preferred embodiment of the present invention;

[0041] Figure 7 This is a graph showing the relationship between liquid volume (AAm hydrogel solution), printing height, and material utilization rate in a preferred embodiment of the present invention.

[0042] Figure 8 This is a graph showing the relationship between liquid volume (PEGDA hydrogel solution), printing height, and material utilization rate in a preferred embodiment of the present invention.

[0043] Figure 9 This is a graph showing the changes in the hydrogel solution during the descent process in a preferred embodiment of the present invention.

[0044] Figure 10 This is a diagram showing the change in the hydrogel solution as it accumulates from the storage area to the printing area during the rising process in a preferred embodiment of the present invention.

[0045] Figure 11 This is a diagram showing the change in the contact angle between the release film and the printing substrate in the hydrogel solution after surface treatment, according to a preferred embodiment of the present invention. Detailed Implementation

[0046] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0047] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element 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 the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0048] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed", "equipped", "sleeved / connected", "connected", etc., should be interpreted broadly. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0049] refer to Figures 1-11 This embodiment provides a photopolymerization device and its manufacturing method for 3D printing hydrogel structures. Hydrogels are widely used in flexible electronics and bioengineering due to their excellent biocompatibility and tunable mechanical properties. The LC-DLP process overcomes the shortcomings of traditional DLP technology, such as low solution utilization and sample dehydration deformation, by leveraging the advantage of high-resolution construction of complex three-dimensional structures through digital light processing (DLP).

[0050] To improve the utilization efficiency of hydrogel solutions and reduce sample dehydration deformation during printing, this embodiment provides a constraint solution utilizing the surface tension of a surface-modified substrate and liquid, referred to as the LC-DLP process. The technical solution adopted is as follows:

[0051] 1. A top-down DLP printing method is used to solidify and accumulate a small amount of hydrogel solution layer by layer into a controllable 3D structure.

[0052] 2. Apply hydrophilic or hydrophobic treatment to the liquid contact interface to improve the ability to control the solution morphology.

[0053] 3. High-precision micro-tissue models, flexible sensors, and microfluidic chips are fabricated using flexible and rigid hydrogel solutions.

[0054] 4. Modify the interface surface between the release film and the printing platform to enhance liquid confinement and prevent solution evaporation.

[0055] The light curing equipment (LC-DLP) provided in this embodiment, such as Figure 1 ,include

[0056] The printing substrate is hydrophilic or hydrophobic at its liquid contact interface to improve solution morphology control. The printing substrate is used to constrain the hydrogel solution. A printing substrate fixing device 3 is provided at the bottom of the printing substrate.

[0057] The digital light processing (DLP) device 1 includes a driving device, an optomechanical system, and a tensioning device, wherein the driving device controls the up-and-down movement of the optomechanical system and the tensioning device;

[0058] Release membranes are used to separate hydrogel solutions from the printing substrate and constrain their morphology;

[0059] The DLP printing area 2 consists of an optical engine 4, a tensioning device 5, and a printing substrate 6, such as Figure 2 As shown;

[0060] The digital light processing (DLP) device uses a release film and a printing substrate to constrain the photocuring of a hydrogel solution. It controls the deformation of the hydrogel solution droplets as the tensioning device moves to match the DLP process of layer-by-layer accumulation of the printed sample.

[0061] The hydrophilic treatment is performed through plasma treatment, and the hydrophobic treatment is performed by spraying with nano-silicon spray.

[0062] The release film is kept flat by a tensioning device, which stretches the release film into a shape with a flat center and a 17° angle around the edges. A liquid storage area is set on the 17° angled surface around the edges, and the printing area is set on the flat center. This triangular liquid storage space ensures that the solution in the storage area can flow smoothly back to the printing area when the tensioning device is raised.

[0063] The middle plane of the release film is the printing area, which is hydrophilically treated; the hydrophilic treatment of the printing area is performed using a plasma treatment machine.

[0064] To improve the utilization rate of the hydrogel solution, the release film and the printing substrate are treated with either hydrophilic or hydrophobic agents. The 15×9 mm printing area in the center plane of the release film is hydrophilicated using a plasma treatment machine. The surface of the printing substrate is then coated with a nano-silicone spray. Figure 5 ac indicates that the surface of untreated 304 stainless steel is smooth and flat. After hydrophobic treatment, a large number of nanoparticles adhere to the surface of the 304 stainless steel. Figure 5 df), to prevent the hydrogel solution from wetting the 304 stainless steel.

[0065] The manufacturing method provided in this embodiment includes the following steps:

[0066] Step 1: Modify the surface of the printing substrate to give it hydrophilic or hydrophobic properties; assemble the digital light processing (DLP) device and release film;

[0067] Step 2, Printing Start-up Stage: Add a quantitative amount of hydrogel solution, which includes flexible hydrogel solution and rigid hydrogel solution, and mix them as needed; add the flexible hydrogel solution and rigid hydrogel solution to the printing substrate as needed;

[0068] Step 3: The hydrogel solution is cured layer by layer using a digital light processing (DLP) device to form a 3D structure; including the following process:

[0069] Step a, Descent stage: The tensioning device presses down the hydrogel solution to the specified height and squeezes out excess hydrogel solution into the storage area;

[0070] During the first layer of printing, the descent process constrains the solution in the printing area to a thin layer of the first layer height, and the remaining solution is squeezed into the reservoir area; the descent process descends at a speed of 0.1 mm / s for the last 5 mm and waits for 10 seconds to ensure that the solution flows level; in subsequent printing, it descends at a speed of 0.3 mm / s to constrain the solution to the specified height.

[0071] Step b, Exposure stage: The pattern of the optical-mechanical projection model slices and the hydrogel solution in the printing area undergo cross-linking;

[0072] Step c, rising stage: The tensioning device slowly rises by 1 mm at a speed of 0.3 mm / s, causing the hydrogel solution in the storage area to rewet the release film surface;

[0073] Step d, Printing completion stage: Repeat steps a, b, and c until all model slice patterns are projected, and finally lift the tensioning device to complete the preparation of the printed part;

[0074] Step 4: Use a release membrane to separate the cured liquid hydrogel structure.

[0075] Flowchart reference for layer-by-layer exposure curing of hydrogel solution Figure 6 The process is divided into five stages: i. Printing start stage, ii. Descent stage, iii. Exposure stage, iv. Ascent stage, and v. End stage. In the start stage, a specified amount of hydrogel is added; in the descent stage, excess hydrogel solution is stored in the reservoir; the hydrogel solution in the printing area is cured by exposure; and in the ascent stage, the hydrogel solution refills the printing area.

[0076] The materials used in the fabrication process included hydrogel solutions with different formulations, including flexible AAm hydrogel solutions and rigid PEGDA hydrogel solutions. Flexible AAm solutions were used to fabricate micro-heart models and flexible sensors, while rigid PEGDA solutions were used to fabricate micropatterns and microfluidic chips.

[0077] To use LC-DLP to complete the overall construction of a 3D model, the constrained liquid needs to be controlled to ensure that: 1. the highest liquid level is greater than or equal to the height of the 3D model; 2. the liquid keeps the printing area wetted.

[0078] The formulation of the flexible AAm hydrogel solution: A 2 wt% Alg solution was prepared by dissolving 2.04 g of Alg powder in 100 g of DIwater and magnetically stirring at 35°C for 12 hours. 0.75 g of LAP and 0.375 g of lemon yellow were dissolved in the Alg solution and magnetically stirred at room temperature for 2 hours. 25 g of AAm and 0.75 g of PEGDA were added to the above mixture and stirred for 5 hours to obtain a basic AAm flexible hydrogel solution with a ratio of AAm:PEGDA:LAP:Tartrazine:Alg:DIwater = 1:0.03:0.03:0.015:0.08:4. When constructing micro-tissue models, microspheres were incorporated into the basic AAm solution to simulate a cell-containing hydrogel solution. When constructing flexible sensor devices, 3M LiCl (Aladdin, Shanghai, China) was dissolved in the basic AAm flexible hydrogel solution.

[0079] The relationship between the liquid volume of AAm hydrogel solution and printing height, and material utilization rate (e.g.) Figure 7 ): Add 0.3, 0.6, 0.9, 1.2, and 1.5 ml of AAM hydrogel solution respectively. The relationship between liquid volume and printing height and material utilization rate is shown. The dashed line represents the relationship between liquid volume and printing height, and the solid line represents the relationship between liquid volume and material utilization rate.

[0080] The rigid PEGDA hydrogel solution formulation consists of PEGDA (Mw = 700), LAP, Tarrazine, and DI water. A rigid PEGDA hydrogel solution with a PEGDA:LAP:Tartrazine:DI water ratio of 8:0.03:0.03:2 was obtained by magnetically stirring 40 g PEGDA, 0.15 g LAP, and 0.15 g lemon yellow in 10 g DI water for 2 hours.

[0081] The relationship between the liquid volume of PEGDA hydrogel solution and printing height, and material utilization rate (e.g.) Figure 8 ): 0.3, 0.6, 0.9, 1.2, and 1.5 ml of PEGDA hydrogel solution were added respectively. The relationship between liquid volume and printing height and material utilization rate is shown. The dashed line represents the relationship between liquid volume and printing height, and the solid line represents the relationship between liquid volume and material utilization rate.

[0082] During the exposure stage, the onboard optical engine operated on a focal plane with an exposure area of ​​15.1*8.49, outputting a light energy intensity of 257 mW / cm² and an accuracy of 7.86 μm. The 3D model was sliced ​​at 50 μm per layer using CHITUBOX V1.9.4. The exposure time for each layer of samples prepared using flexible AAm hydrogel was set to 1 s, and the exposure time for each layer of samples prepared using PEGDA hydrogel was set to 2 s. After printing, residual hydrogel solution was removed using a high-pressure air gun, and the samples were gently wiped with lint-free paper. The samples, after removing residual hydrogel solution, were then cured under a UV lamp (1000 mW, 20 mins).

[0083] The movement process of the constrained hydrogel solution during descent and elevation:

[0084] like Figure 9 During descent, the hydrogel solution is compressed, and due to its own surface tension, the solution can be maintained in the reservoir area; such as Figure 10 During the ascent, the release film detaches from the surface of the cured sample, and the hydrogel solution, driven by the internal negative pressure, rapidly wets the printing area and the surface of the cured sample. During the ascent, the constrained hydrogel solution changes state; as the tensioning device rises, the uncured solution gradually accumulates from the reservoir area towards the printing area.

[0085] Controlling the morphology of hydrogel liquids during DLP printing is crucial for LC-DLP technology. Hydrophilic or hydrophobic treatments of the release film and printing substrate surface properties are effective methods to control the confinement of droplets. Figure 11After the printing substrate was spray-treated, the contact angle between the flexible AAM hydrogel solution containing 77.59 wt% water and the substrate increased from 40° to 160°. The PEGDA hydrogel solution, with a lower water content (19.88 wt%), showed no significant change in its contact angle (12°) on the printing substrate before and after treatment. After the release film was hydrophilically treated with oxygen plasma, the surface energy of both hydrogels increased, and their contact angles decreased to varying degrees (AAm: 84° to 76°, PEGDA: 86° to 67°), promoting the wetting of the hydrogel solution on the release film surface. By inhibiting liquid wetting on the printing substrate while promoting liquid wetting on the release film, the LC-DLP process achieved confinement of the hydrogel solution.

[0086] This embodiment provides a top-down liquid-constrained digital light processing (LC-DLP) process that achieves efficient utilization of small amounts of hydrogel solution and high-fidelity molding of bio-devices. Surface modification was applied to the interface in contact with the hydrogel solution to improve LC-DLP's morphological control over the solution during printing. LC-DLP can successfully fabricate micro-heart models with complex spatial structures, flexible sensors sensitive to stretching and compression, and 3D microfluidic chips with intersecting independent flow channels while maintaining high hydrogel material utilization.

[0087] The above description is merely a preferred embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention by those skilled in the art within the scope of the technology disclosed in the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A photopolymerization apparatus for 3D printing hydrogel structures, characterized in that: include The printing substrate is hydrophilic or hydrophobic at its liquid contact interface to improve the ability to control the solution morphology. The printing substrate is used to constrain the hydrogel solution. A digital light processing (DLP) device includes a drive unit, an optomechanical system, and a tensioning device, wherein the drive unit controls the up-and-down movement of the optomechanical system and the tensioning device; Release membranes are used to separate hydrogel solutions from the printing substrate and constrain their morphology; The DLP printing area consists of an optical engine, a tensioning device, and a printing substrate; The digital light processing (DLP) device uses a release film and a printing substrate to constrain the photocuring of a hydrogel solution. It controls the deformation of the hydrogel solution droplets as the tensioning device moves to match the DLP process of layer-by-layer accumulation of the printed sample.

2. The photopolymerization device for 3D printing hydrogel structures according to claim 1, characterized in that: The hydrophilic treatment is performed via plasma treatment; The hydrophobic treatment is performed by spraying with a nano-silicon spray.

3. The photopolymerization apparatus for 3D printing hydrogel structures according to claim 1, characterized in that: The release film is kept flat by tensioning the tensioning device.

4. The photopolymerization apparatus for 3D printing hydrogel structures according to claim 3, characterized in that: The tensioning device tensions the release film into a shape with a flat center and a 17° angle around the edges.

5. The photopolymerization apparatus for 3D printing hydrogel structures according to claim 4, characterized in that: The middle plane of the release film is the printing area, which is hydrophilically treated. The hydrophilic treatment of the printing area is performed using a plasma treatment machine.

6. A method for manufacturing hydrogel structures for 3D printing, characterized in that: The photocuring device according to any one of claims 1-5; Its manufacturing method includes the following steps: Step 1: Modify the surface of the printing substrate to give it hydrophilic or hydrophobic properties; assemble the digital light processing (DLP) device and release film; Step 2, Printing Start-up Stage: Add a quantitative amount of hydrogel solution, which includes flexible hydrogel solution and rigid hydrogel solution, and mix them as needed; add the flexible hydrogel solution and rigid hydrogel solution to the printing substrate as needed; Step 3: The hydrogel solution is cured layer by layer by exposure using a digital light processing (DLP) device to form a 3D structure; Step 4: Use a release membrane to separate the cured liquid hydrogel structure.

7. A method for manufacturing hydrogel structures for 3D printing according to claim 6, characterized in that: Step 3 includes the following process: Step a, Descent stage: The tensioning device presses down the hydrogel solution to the specified height and squeezes out excess hydrogel solution into the storage area; During the first layer of printing, the descent process constrains the solution in the printing area to a thin layer of the first layer height, and the remaining solution is squeezed into the reservoir area; the descent process descends at a speed of 0.1 mm / s for the last 5 mm and waits for 10 seconds to ensure that the solution flows level; in subsequent printing, it descends at a speed of 0.3 mm / s to constrain the solution to the specified height. Step b, Exposure stage: The pattern of the optical-mechanical projection model slices and the hydrogel solution in the printing area undergo cross-linking; Step c, rising stage: The tensioning device slowly rises by 1 mm at a speed of 0.3 mm / s, causing the hydrogel solution in the storage area to rewet the release film surface; Step d, printing completion stage: Repeat steps a, b, and c until all model slice patterns are projected, and finally lift the tensioning device to complete the preparation of the printed part.

8. A method for manufacturing hydrogel structures for 3D printing according to claim 7, characterized in that: The tensioning device tensions the release film into a flat plane in the middle and an inclined plane at 17° around the edges. The liquid storage area is set on the inclined plane at 17° around the edges, and the printing area is set on the flat plane in the middle.

9. A method for manufacturing a 3D printed hydrogel structure according to claim 6, characterized in that: The flexible hydrogel solution is a flexible AAM solution, and the rigid hydrogel solution is a rigid PEGDA solution.

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