DLP-based voxelated heterogeneous structure 3D printing apparatus and method

Abstract

The present application relates to the field of multi-material additive manufacturing, in particular to a voxelized heterogeneous structure 3D printing device and method based on DLP. The method is to realize the movement, mixing and splitting of droplet materials through digital microfluidics by using dielectric wetting principle, transfer the droplets to the corresponding voxel position according to the predefined program, realize the precise control of different materials, and obtain voxelized heterogeneous structure three-dimensional workpiece through layer-by-layer accumulation and solidification processing. The present application provides a new method for realizing the printing of heterogeneous structure.

Description

Technical Field

[0001] This invention belongs to the field of direct-write 3D printing additive manufacturing technology, and specifically relates to a voxelized heterostructure 3D printing device and method based on DLP. Background Technology

[0002] Digital Light Processing (DLP) 3D printing is a method of 3D printing that utilizes digital light processing technology. Its working principle involves using a DLP projector to project UV light onto a photocurable resin, curing each layer of resin according to the designed pattern to create the desired shape. Compared to traditional 3D printing technologies, DLP 3D printing is faster, has higher resolution, and is suitable for creating objects with intricate structures and complex shapes. With DLP 3D printing technology, users can quickly and accurately produce printed materials with high-quality, smooth surfaces.

[0003] However, this process typically involves changing the resin tank containing different UV-curable resin materials (such as using a carousel-style tank transfer system) to print multi-material samples. But challenges remain regarding resin tank contamination and the complexity of heterogeneous materials during the printing process. Summary of the Invention

[0004] This invention provides a voxelized heterogeneous structure 3D printing device and method based on digital light processing (DLP) to address the problems of resin pool contamination and heterogeneous material complexity in digital light processing 3D printing technology. The invention utilizes a digital manipulation platform to control droplet movement, mixing, and splitting, transferring droplets to corresponding voxel positions according to a predefined program. This achieves precise control over different materials, and through layer-by-layer accumulation and curing, a voxelized heterogeneous three-dimensional part is obtained.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] A DLP-based voxelization heterostructure 3D printing device includes:

[0007] Digital droplet manipulation platform: It can pump multi-material systems through infusion pipelines to realize the supply of multi-material systems and the manipulation of droplets, and move droplets to designated positions in a timed and quantitative manner. In addition, the platform also has the function of droplet splitting and merging, thereby obtaining voxelized droplet patterns on the platform.

[0008] Photocuring system: As an optional module, it can be used for material systems that require light curing, such as photosensitive resin material systems;

[0009] Heated transfer platform: Its transfer device can be controlled by programming, and its lower surface contains periodically arranged hydrophilic units, with the gaps between each hydrophilic unit being hydrophobic areas. Relying on this patterned hydrophilic / hydrophobic design, through design and programming, it is possible to transfer voxelized droplets (or semi-cured materials) from the digital droplet manipulation platform to the lower surface of the transfer platform while maintaining their original shape and composition. The platform has an integrated temperature control program for starting and monitoring the heating function of the transfer platform, and precisely controlling the heating and curing process of thermosetting resin materials.

[0010] Ultrasonic platform: It contains an ultrasonic control program that can separate a single layer of voxelized material from the heatable transfer platform through ultrasonic treatment. The ultrasonic platform completely receives the voxelized droplets (or semi-cured material) transferred by the heatable transfer platform and accumulates the material layer by layer on this platform to complete the additive manufacturing printing of voxelized heterostructures. The platform also has an integrated temperature control program that can heat and cure thermoset parts.

[0011] Control system: It contains a main control program to coordinate and control the spatial movement, process timing and parameter design of the digital droplet manipulation platform, photopolymerization system and heating transfer platform; to ensure that the program can accurately control the position, speed and movement trajectory of each platform, as well as the process parameters of each platform, such as the time interval of droplet manipulation, the light exposure time of the photopolymerization system, the heating temperature of the transfer platform, etc., so as to ensure the accurate preparation of voxelized heteromaterials.

[0012] Furthermore, the digital droplet manipulation platform includes:

[0013] Liquid supply pumps: The digital droplet manipulation platform contains multiple liquid supply pumps, which are used to supply liquid materials A, B, C, D, etc. through the liquid delivery pipeline 12 to the storage area of ​​the digital droplet manipulation platform.

[0014] Infusion pipelines: These are used to transport liquid materials from the liquid supply pump to the storage area of ​​the digital control platform;

[0015] Liquid storage area: It is used to temporarily store liquid materials supplied by the liquid supply pump, and then transport the liquid materials to the designated location through the timing control of the driving electrode in the control area;

[0016] Manipulation area: It is a driving electrode composed of a hydrophobic layer, a dielectric layer and a polygonal electrode array. It is used to move the liquid material in the storage area to the expected position along a specified path, and complete the multi-functional characteristics of microdroplet generation, transportation, splitting and merging.

[0017] The manipulation area of ​​the digital droplet manipulation platform consists of a hydrophobic layer, a dielectric layer, and a polygonal electrode array.

[0018] The hydrophobic layer is made of polytetrafluoroethylene or polyvinyl fluoride with a thickness of 50-900 nm. It can give the droplet a large initial contact angle. When the driving electrode is energized, the droplet generates a sufficiently large contact angle to make the droplet move.

[0019] The dielectric layer material is SiO2, Si3N4, Al2O3, PDMS, SU-8 photoresist, and parylene, etc., with a thickness of 5-70μm. It can be used to protect the driving electrode and optimize the liquid control effect. According to the dielectric wetting theory, as the driving voltage increases, the contact area between the droplet and the surface decreases, effectively reducing the friction of the interface and increasing the droplet movement speed.

[0020] The unit structure of the driving electrode has a side length of 0.5-1.5 mm. It can be designed as a polygon, such as a triangle, quadrilateral, pentagon and hexagon, according to specific needs. The edge serrations of the driving electrode are isosceles triangles with a serration width and height of 30-200 μm and a spacing of 0-100 μm, in order to improve the droplet driving performance.

[0021] Furthermore, the ultrasonic frequency of the ultrasonic platform is 20-100 kHz.

[0022] In addition, the voxelization heterostructure 3D printing device and method based on DLP are described below:

[0023] S101, Material Selection

[0024] Material system: one of photosensitive resin and thermosetting resin, or one of photosensitive resin and thermosetting resin containing 2-45 vol% filler;

[0025] The thermosetting resin is one of epoxy resin, acrylate, silicone rubber, and polyurethane.

[0026] The photosensitive resin is one of the following: free radical photosensitive resin, cationic photosensitive resin, and free radical-cationic hybrid photosensitive resin;

[0027] The filler is one or more of the following: photothermal agent (carbon nanomaterials, gold nanoparticles), magnetothermal agent (Fe3O4), and sacrificial template particles (sodium glutamate crystals, sugar particles, salt particles, iodine particles, polyvinyl alcohol).

[0028] The viscosity range of the applicable material is 1-800 cP;

[0029] In this material system, the photosensitive resin and thermosetting resin can be adjusted to obtain different mechanical properties by adjusting different material components;

[0030] S102 Additive manufacturing of voxelized heterostructures, specifically including:

[0031] Step 1: Constructing the structural model

[0032] The structure is designed according to the required performance, and the designed structure is modeled using 3D software;

[0033] Step 2: Voxel-based structural model design

[0034] The 3D model to be printed is decomposed into multiple small voxel units, voxelized, and the position, shape and material properties of each voxel are determined. The movement path and related process parameters of each droplet are also determined.

[0035] Step 3: Digital Droplet Manipulation

[0036] Material systems with different material properties are loaded into different liquid supply pumps. Material systems A, B, C, and D are pumped to the storage area of ​​the digital droplet manipulation platform through liquid delivery pipelines. Then, in the manipulation area, different droplets are transferred to the corresponding voxel positions according to a predefined path. During this process, the droplets can also be split and mixed to assemble a single layer of voxelized material. During the driving process, an appropriate voltage is selected according to different material properties, with a voltage range of 80V-180V.

[0037] The volume of the droplet is 2-50 μL;

[0038] Step 4: Semi-curing treatment

[0039] As an optional module, the corresponding equipment is matched according to the material requirements. If the liquid has photosensitive properties, a photocuring system module needs to be configured. At the same time, the light intensity of the photocuring system is determined to be between 500 mW / cm² and 2000 mW / cm², and the light exposure time is 10s-10min, depending on the material properties. If the liquid is a thermosetting material, the photocuring process can be skipped and the heating step can be skipped. The heating function of the heatable transfer platform is required. The heating temperature of the heatable transfer platform is 30-100℃ and the heating time is 5-200min, so that the liquid is in a semi-cured state.

[0040] Step 5: Stacking and shaping process

[0041] The semi-cured voxelized material on the digital droplet manipulation platform is transferred to the ultrasonic platform or the previous layer of material using a heatable transfer platform. Steps 2-4 are repeated to achieve stereolithography of the three-dimensional structure containing the voxelized design.

[0042] S103 Post-processor

[0043] Depending on the materials used, appropriate post-processing methods are adopted. First, for samples containing sacrificial template particles (monosodium glutamate crystals, sugar particles, salt particles, iodine particles, polyvinyl alcohol), the printed sample must be immersed in water at 45℃~70℃ for 2-35 hours. Second, a curing post-processing is performed. Thermosetting resins require thermosetting post-processing, and photosensitive resins require photocuring post-processing to ensure that the printed object is completely cured and formed. The photocuring treatment requires a light intensity of 500 mW / cm² to 2000 mW / cm² and a light exposure time of 30-120 min. The thermosetting treatment requires a heating temperature of 30-100℃ and a heating time of 20-120 min. After the post-processing is completed, a voxelized heterostructure three-dimensional part is obtained.

[0044] The beneficial effects of this invention are:

[0045] 1. This invention patent is based on droplet manipulation technology, which can simultaneously process multiple different materials or components within a material system, including hard materials, soft materials and biological materials. Through operations such as droplet transfer, splitting, and mixing, it can realize the preparation of complex three-dimensional samples with voxelized material characteristics.

[0046] 2. This patent utilizes droplet manipulation technology to prepare complex heterogeneous structures, achieving efficient utilization of droplets, reducing waste generation, minimizing resource waste, and meeting the requirements of sustainable development.

[0047] 3. This invention has wide applicability. By changing the composition and proportion of each component in the photosensitive resin material system, it can achieve localized specialization of mechanical properties such as elasticity, tensile strength, etc., and can be widely used in fields such as drug detection, biomedicine, and aerospace material preparation. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the system configuration of the present invention;

[0049] Figure 2 This is a schematic diagram of the structure of the digital droplet manipulation platform described in this invention;

[0050] Figure 3 This is a schematic diagram illustrating the movement, mixing, and splitting of droplets on the digital droplet manipulation platform described in this invention;

[0051] Figure 4 This is a schematic diagram of the structure of the heatable transfer platform described in this invention;

[0052] Figure 5 This is a process flow diagram for 3D printing of single-layer voxelized heterostructures as described in this invention.

[0053] The reference numerals in the figure are:

[0054] Digital droplet manipulation platform 1, photopolymerization system 2, heatable transfer platform 3, ultrasonic platform 4;

[0055] Liquid supply pump 11, liquid delivery pipeline 12, liquid storage area 13, control area 14. Detailed Implementation

[0056] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] This invention solves the problems of resin pool contamination and heterogeneous material complexity in existing technologies. For detailed technical solutions, please refer to [link / reference]. Figure 1 As shown, the DLP-based voxelized heterostructure 3D printing apparatus includes:

[0058] Digital droplet manipulation platform 1 (see also) Figure 2 It can deliver multi-material systems via 12 pumps through infusion pipelines, enabling the supply of multi-material systems and the manipulation of droplets, moving droplets to designated locations in a timed and quantitative manner. Furthermore, the platform also has droplet splitting and merging capabilities (see [link to platform]). Figure 3 This allows for the acquisition of voxelized droplet patterns on the platform.

[0059] Photocuring System 2: As an optional module, it can be used for material systems that require photocuring, such as photosensitive resin material systems;

[0060] Heated transfer platform 3 (see also) Figure 4 The transfer device is programmable and its lower surface contains periodically arranged hydrophilic units, with the gaps between each hydrophilic unit being hydrophobic regions. Relying on this patterned hydrophilic / hydrophobic design, through design and programming, it is possible to transfer voxelized droplets (or semi-cured materials) from the digital droplet manipulation platform 1 to the lower surface of the transfer platform while preserving their original shape and composition. This platform has an integrated temperature control program for initiating and monitoring the heating function of the transfer platform, precisely controlling the heating and curing process of the thermosetting resin material.

[0061] Ultrasonic Platform 4: Contains an ultrasonic control program that uses ultrasonic treatment to detach a single layer of voxelized material from the heatable transfer platform 3. The ultrasonic platform 4 completely receives the voxelized droplets (or semi-cured material) transferred from the heatable transfer platform 3 and performs layer-by-layer accumulation of material on this platform to complete the additive manufacturing printing of the voxelized heterostructure. This platform also has an integrated temperature control program for heating and curing thermoset parts.

[0062] Control System 5: It contains a main control program to coordinate and control the spatial movement, process timing, and parameter design of the digital droplet manipulation platform 1, the photocuring system 2, and the heating transfer platform; to ensure that the program can accurately control the position, speed, and trajectory of each platform, as well as the process parameters of each platform, such as the time interval of droplet manipulation, the illumination time of the photocuring system 2, and the heating temperature of the transfer platform, so as to ensure the accurate preparation of voxelized heteromaterials.

[0063] Furthermore, the digital droplet manipulation platform 1 includes:

[0064] Liquid supply pump 11: The digital droplet manipulation platform 1 contains multiple liquid supply pumps 11. The supply pumps are used for supplying multi-material systems and can deliver liquid materials A, B, C, D, etc. to the storage area 13 of the digital droplet manipulation platform 1 through the liquid delivery pipeline 12.

[0065] Infusion pipeline 12: It is used to transport liquid material in the liquid supply pump 11 to the storage area 13 of the digital control platform;

[0066] Liquid storage area 13: It is used to temporarily store liquid materials supplied by liquid supply pump 11, and then transport the liquid materials to a designated location through the timing control of the driving electrode via the control area 14.

[0067] Manipulation area 14: It is a driving electrode composed of a hydrophobic layer, a dielectric layer and a polygonal electrode array, used to move the liquid material in the storage area 13 to the expected position according to the specified path, and complete the multi-functional characteristics of microdroplet generation, transportation, splitting and merging.

[0068] The manipulation area 14 of the digital droplet manipulation platform 1 is composed of a hydrophobic layer, a dielectric layer and a polygonal electrode array.

[0069] The hydrophobic layer is made of polytetrafluoroethylene or polyvinyl fluoride, with a thickness of 50-900 nm. It can impart a large initial contact angle to the droplet, and when the driving electrode is energized, the droplet generates a sufficiently large contact angle to allow the droplet to move.

[0070] The dielectric layer material is SiO2, Si3N4, Al2O3, PDMS, SU-8 photoresist, and parylene, with a thickness of 5-70 μm. It serves both to protect the driving electrode and optimize liquid control. According to dielectric wetting theory, as the driving voltage increases, the contact area between the droplet and the surface decreases, effectively reducing interfacial friction and increasing droplet movement speed.

[0071] The unit structure of the driving electrode has a side length of 0.5-1.5 mm, and can be designed as a polygon, such as a triangle, quadrilateral, pentagon, or hexagon, depending on specific needs. The serrations on the edge of the driving electrode are isosceles triangles with a width and height of 30-200 μm and a spacing of 0-100 μm, in order to improve the droplet driving performance.

[0072] Furthermore, the ultrasonic frequency of the ultrasonic platform 4 is 20-100 kHz.

[0073] In addition, the voxelization heterostructure 3D printing device and method based on DLP are described below:

[0074] S101, Material Selection

[0075] Material system: one of photosensitive resin and thermosetting resin, or one of photosensitive resin and thermosetting resin containing 2-45 vol% filler;

[0076] The thermosetting resin is one of epoxy resin, acrylate, silicone rubber, and polyurethane.

[0077] The photosensitive resin is one of the following: free radical photosensitive resin, cationic photosensitive resin, and free radical-cationic hybrid photosensitive resin;

[0078] The filler is one or more of the following: photothermal agent (carbon nanomaterials, gold nanoparticles), magnetothermal agent (Fe3O4), and sacrificial template particles (sodium glutamate crystals, sugar particles, salt particles, iodine particles, polyvinyl alcohol).

[0079] The viscosity range of the applicable material is 1-800 cP;

[0080] In this material system, the photosensitive resin and thermosetting resin can be adjusted to obtain different mechanical properties by adjusting different material components.

[0081] S102 Additive manufacturing of voxelized heterostructures (see also) Figure 5 Specifically, it includes:

[0082] Step 1: Constructing the structural model

[0083] The structure is designed according to the required performance, and the designed structure is modeled using 3D software.

[0084] Step 2: Voxel-based structural model design

[0085] The 3D model to be printed is decomposed into multiple small voxel units, voxelized, and the position, shape and material properties of each voxel are determined. The movement path and related process parameters of each droplet are also determined.

[0086] Step 3: Digital Droplet Manipulation

[0087] Material systems with different material properties are loaded into different liquid supply pumps 11. Material systems A, B, C, and D are pumped to the storage area 13 of the digital droplet manipulation platform 1 via liquid delivery pipes 12. Then, in the manipulation area 14, different droplets are transferred to their corresponding voxel positions according to a predefined path. During this process, the droplets can also be split and mixed, ultimately assembling into a single layer of voxelized material. An appropriate voltage is selected based on the different material properties during the driving process, with a voltage range of 80V-180V.

[0088] The volume of the droplet is 2-50 μL.

[0089] Step 4: Semi-curing treatment

[0090] As an optional module, appropriate equipment is matched according to material requirements. If the liquid has photosensitive properties, a photocuring system 2 module needs to be configured. The light intensity of the photocuring system 2 should be between 500 mW / cm² and 2000 mW / cm², and the light exposure time should be 10s-10min, depending on the material properties. If the liquid is a thermosetting material, the photocuring process can be skipped, and the heating step can be initiated, requiring the heating function of the heatable transfer platform 3. The heating temperature of the heat transfer platform is 30-100℃, and the heating time is 5-200min, keeping the liquid in a semi-cured state.

[0091] Step 5: Stacking and shaping process

[0092] The semi-cured voxelized material on the digital droplet manipulation platform 1 is transferred to the ultrasonic platform 4 or the previous layer of material through the heatable transfer platform 3. Steps 2-4 are repeated to achieve stereolithography of the three-dimensional structure containing the voxelized design.

[0093] S103 Post-processor

[0094] Depending on the materials used, appropriate post-processing methods are adopted. First, for materials containing sacrificial template particles (monosodium glutamate crystals, sugar particles, salt particles, iodine particles, polyvinyl alcohol), the printed sample must be immersed in water at 45℃~70℃ for 2-35 hours. Next, a curing post-processing is performed. Thermosetting resins require thermosetting post-processing, while photosensitive resins require photocuring post-processing to ensure complete curing of the printed object. The photocuring treatment involves an irradiation intensity of 500 mW / cm² to 2000 mW / cm² for 30-120 min; the thermosetting treatment involves a heating temperature of 30-100℃ for 20-120 min. After post-processing, a voxelized heterostructure three-dimensional part is obtained.

[0095] A more preferred first embodiment of the method relating to this application is as follows:

[0096] Material selection: A variety of free radical photosensitive resin precursors were selected, with different moduli after curing, ranging from high to low as A1, B1, C1, and D1. The viscosity of the precursor materials was 400 cP.

[0097] The structure is designed according to the required performance, and modeled using 3D software. The 3D model to be printed is decomposed into multiple small voxel units, voxelized, and the position, shape, and material properties of each voxel are determined. The movement path and related process parameters of each droplet are then determined.

[0098] Four material systems with different material properties are loaded into different liquid supply pumps 11. The photosensitive resin is pumped to the liquid storage area 13 of the digital droplet manipulation platform 1 through the liquid delivery pipe 12. Then, in the manipulation area 14, different droplets are transferred to the corresponding voxel positions according to a predefined path. During this process, the droplets can also be split and mixed, and then assembled to form a monolayer material with a modulus voxel design. The voltage used is 90V, and the droplet volume is 5μL.

[0099] Select the photocuring system module 2, and determine the light intensity of the photocuring system 2 to be 1500 mW / cm² and the light exposure time to be 30s, so that the liquid is in a semi-polymerized state. Then, the semi-cured voxelized material on the digital droplet manipulation platform 1 is transferred to the ultrasonic platform 4 through the transfer platform 3. Repeat the above steps to achieve the stereolithography of the three-dimensional structure of the voxelized design with internal modulus.

[0100] Finally, the shaped voxelized heterostructure was placed in a 1500mW / cm² UV curing system 2 and cured for 30 minutes to obtain a fully cured voxelized heterostructure.

[0101] A more preferred second embodiment of the method relating to this application is as follows:

[0102] Thermosetting epoxy resin was selected as the matrix material A2. 10 vol% carbon nanomaterials, 10 vol% gold nanoparticles, and 15 vol% salt particles were added to the matrix material to obtain material systems B2, C2, and D2. The viscosities of material systems A2, B2, C2, and D2 were 200, 350, 370, and 450 cP, respectively.

[0103] The structure is designed according to the required performance, and modeled using 3D software. The 3D model to be printed is decomposed into multiple small voxel units, voxelized, and the position, shape, and material properties of each voxel are determined. The movement path and related process parameters of each droplet are then determined.

[0104] Four material systems with different material properties are loaded into different liquid supply pumps 11. The photosensitive resin is pumped to the liquid storage area 13 of the digital droplet manipulation platform 1 through the liquid delivery pipe 12. Then, in the manipulation area 14, different droplets are transferred to the corresponding voxel positions according to a predefined path. During this process, the droplets can also be split and mixed, thereby assembling a monolayer material with a modulus voxel design. The voltage used is 100V, and the droplet volume is 10μL.

[0105] The matrix material is a thermosetting resin, so a heatable transfer platform 3 can be used directly. The heating temperature of the transfer platform is 70℃, and the heating time is 20 minutes, so that the liquid is in a semi-solid state. Subsequently, the semi-solid voxelized material on the digital droplet manipulation platform 1 is transferred to the ultrasonic platform 4 or the previous layer of material through the heatable transfer platform 3. Steps 2-4 are repeated to achieve stereolithography of the three-dimensional structure containing the voxelized design.

[0106] Finally, post-processing is performed. First, for samples containing sacrificial template particles (monosodium glutamate crystals, sugar particles, salt particles, iodine particles, polyvinyl alcohol), the entire printed sample must be immersed in 60°C water for 2 hours. Then, the printed sample is placed in a 60°C environment for 100 minutes to obtain a fully cured porous structure, a heterogeneous structure with different composite materials and voxelized distribution of matrix materials.

Claims

1. A voxelized heterostructure 3D printing device based on DLP, characterized in that: include: Digital droplet manipulation platform (1): It can pump a multi-material system through the infusion pipeline (12) to realize the supply of the multi-material system and the manipulation of droplets, and move the droplets to the designated position in a timed and quantitative manner. In addition, the platform also has the function of droplet splitting and merging, so as to obtain voxelized droplet patterns on the platform. Photocuring system (2): It can be used as an optional module for material systems that require photocuring; Heated transfer platform (3): Its transfer device can be controlled by programming, and its lower surface contains periodically arranged hydrophilic units. The gap between each hydrophilic unit is a hydrophobic area. Relying on this patterned hydrophilic / hydrophobic design, through design and programming, it is possible to transfer the voxelized droplets on the digital droplet manipulation platform (1) to the lower surface of the transfer platform while ensuring the original shape and composition. The platform has an integrated temperature control program for starting and monitoring the heating function of the transfer platform and accurately controlling the heating and curing process of thermosetting resin materials. Ultrasonic platform (4): It contains an ultrasonic control program. Through ultrasonic treatment, the single-layer voxelized material can be separated from the heatable transfer platform (3). The ultrasonic platform (4) completely receives the voxelized droplets transmitted by the heatable transfer platform (3) and accumulates the material layer by layer on this platform to complete the additive manufacturing printing of the voxelized heterostructure. The platform also has an integrated temperature control program, which can heat and cure thermosetting parts. Control system (5): It contains a main control program to coordinate and control the spatial movement, process timing and parameter design of the digital droplet manipulation platform (1), the photocuring system (2) and the heating transfer platform; to ensure that the program can accurately control the position, speed and movement trajectory of each platform, as well as the process parameters of each platform. The process parameters are the time interval of droplet manipulation, the illumination time of the photocuring system (2) and the heating temperature of the transfer platform, so as to ensure the accurate preparation of voxelized heteromaterials. The digital droplet manipulation platform (1) includes: Liquid supply pump (11): The digital droplet control platform (1) contains multiple liquid supply pumps (11). The supply pumps are used for supplying multi-material systems and can deliver liquid materials A, B, C and D to the storage area (13) of the digital droplet control platform (1) through the liquid delivery pipeline (12). Infusion pipeline (12): It is used to transport liquid material in the liquid supply pump (11) to the storage area (13) of the digital control platform. Storage area (13): It is used to temporarily store liquid materials supplied by the liquid supply pump (11), and then transport the liquid materials to the designated location through the timing control of the driving electrode by the control area (14); Manipulation area (14): It is a driving electrode composed of a hydrophobic layer, a dielectric layer and a polygonal electrode array, used to move the liquid material in the storage area (13) to the expected position according to the specified path, and complete the multi-functional characteristics of microdroplet generation, transportation, splitting and merging; The manipulation area (14) of the digital droplet manipulation platform (1) is composed of a hydrophobic layer, a dielectric layer and a polygonal electrode array. The hydrophobic layer is made of polytetrafluoroethylene or polyvinyl fluoride with a thickness of 50-900 nm. It can give the droplet a large initial contact angle. When the driving electrode is energized, the droplet generates a sufficiently large contact angle to make the droplet move. The dielectric layer material is one or a combination of several of SiO2, Si3N4, Al2O3, PDMS, SU-8 photoresist and parylene, with a thickness of 5-70 μm. It can be used to protect the driving electrode and optimize the liquid control effect. According to the dielectric wetting theory, as the driving voltage increases, the contact area between the droplet and the surface decreases, which effectively reduces the friction of the interface and increases the droplet movement speed. The unit structure of the driving electrode has a side length of 0.5-1.5 mm, and can be designed as a polygon as needed. The edge serrations of the driving electrode are isosceles triangles with a serration width and height of 30-200 μm and a spacing of 0-100 μm, in order to improve the droplet driving performance. Furthermore, the ultrasonic frequency of the ultrasonic platform (4) is 20-100 KHz.

2. A method for 3D printing voxelized heterostructures based on DLP, characterized in that: The specific printing method is as follows: S101, Material Selection Material system: one of photosensitive resin and thermosetting resin, or one of photosensitive resin and thermosetting resin containing 2-45 vol% filler; The thermosetting resin is one of epoxy resin, acrylate, silicone rubber, and polyurethane. The photosensitive resin is one of the following: free radical photosensitive resin, cationic photosensitive resin, and free radical-cationic hybrid photosensitive resin; The filler is one or more of photothermal agents, magnetothermal agents, and sacrificial template particles; The applicable material viscosity range is 1-800 cP; In this material system, the photosensitive resin and thermosetting resin can be adjusted to obtain different mechanical properties by adjusting different material components; S102 Additive manufacturing of voxelized heterostructures, specifically including: Step 1: Constructing the structural model The structure is designed according to the required performance, and the designed structure is modeled using 3D software; Step 2: Voxel-based structural model design The 3D model to be printed is decomposed into multiple small voxel units, voxelized, and the position, shape and material properties of each voxel are determined. The movement path and related process parameters of each droplet are also determined. Step 3: Digital Droplet Manipulation Material systems with different material properties are loaded into different liquid supply pumps (11), and material systems A, B, C and D are pumped to the storage area (13) of the digital droplet manipulation platform (1) through the liquid delivery pipeline (12). Then, in the manipulation area (14), different droplets are transferred to the corresponding voxel positions according to the predefined path. During this process, the droplets can also be split and mixed, and then assembled to form a single layer of voxelized material. During the driving process, an appropriate voltage is selected according to different material properties, and the voltage range is 80V-180V. The volume of the droplet is 2-50 μL; Step 4: Semi-curing treatment As an optional module, the corresponding equipment is matched according to the material requirements. If the liquid has photosensitive properties, a photocuring system (2) module needs to be configured. At the same time, the light intensity of the photocuring system (2) is determined to be 500 mW / cm based on the material properties. 2 Up to 2000 mW / cm 2 Between, the light exposure time is 10s-10min; if the liquid is a thermosetting material, the light curing process can be skipped and the heating step can be skipped. The heating function of the heatable transfer platform (3) is required. The heating temperature of the heat transfer platform is 30-100℃ and the heating time is 5-200min, so that the liquid is in a semi-cured state. Step 5: Stacking and shaping process The semi-solidified voxel material on the digital droplet manipulation platform 1 is transferred to the ultrasonic platform (4) or the previous layer material through the heatable transfer platform (3). Steps 2-4 are repeated to achieve the stereolithography of the three-dimensional structure containing the voxel design. S103 Post-processor Depending on the materials used, appropriate post-processing methods should be adopted. First, for samples containing sacrificial template particles, the entire printed sample should be immersed in water at 45℃~70℃ for 2-35 hours. Second, a curing post-processing should be performed. Thermosetting resins require thermosetting post-processing, while photosensitive resins require photocuring post-processing to ensure complete curing of the printed object. The photocuring treatment requires a light intensity of 500 mW / cm². 2 Up to 2000 mW / cm 2 The light exposure time is 30-120 min; the thermosetting heating temperature is 30-100℃ and the heating time is 20-120 min. After post-processing, a voxelized heterostructure three-dimensional part is obtained.

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