Temperature-electric composite field assisted direct writing forming system and method

Abstract

The invention provides a temperature-electric composite field assisted direct writing forming system and method. The system comprises a writing unit, a temperature regulation and control system, an electric field generation module and a post-processing unit. The writing unit achieves multi-dimensional printing, the temperature regulation and control system accurately controls the temperature of a substrate through a cooling liquid circulation pipeline and a heating resistance wire, the electric field generation module establishes a high-voltage electric field to assist material forming, and a freeze dryer of the post-processing unit removes low-temperature modal ice crystals. The method comprises the steps of macromolecule-based composite material preparation, base material input, temperature field control, electric field application, path control deposition jet flow, aftertreatment and the like, a porous structure is formed in a low-temperature mode, and regular cracks are induced in a high-temperature mode. According to the method, the precision control problem of the polymer-based composite material in complex structure manufacturing is effectively solved, rapid preparation of a cross-scale and high-precision three-dimensional structure is achieved, the forming quality and the morphology control capability are remarkably improved, and the method has remarkable technical advantages and application value.

Description

Technical Field

[0001] The present invention relates to the field of 3D printing technology, and in particular to a temperature-electricity composite field assisted direct writing system and method. Background Art

[0002] Electric field-assisted direct writing (EFAD) is a maskless, non-contact direct writing process that can produce more complex structures than conventional extrusion-based direct writing. The basic principle is that a voltage is applied to a needle tip. The electric field forces the material at the needle tip to form a Taylor cone. The material is ejected downward through the tip of this liquid cone, allowing the resulting lines to be several orders of magnitude smaller than those produced by the needle tip.

[0003] At present, the electric field assisted direct writing method has the following main limitations:

[0004] (1) This process can only form two-dimensional planar patterns and is difficult to stack in the out-of-plane direction. In other words, it is difficult to perform stable and high-precision multi-layer stacking in the vertical (Z-axis) direction to construct complex three-dimensional structures.

[0005] (2) The printed line pattern cannot be stable without curing treatment and is easy to spread on the substrate, affecting the width and molding accuracy of the line, resulting in increased line width and shape distortion, which seriously reduces the molding accuracy and resolution.

[0006] (3) When using polymer-based composite materials, it is impossible to control the molding accuracy in the manufacture of complex structures. For the fine and complex structures (such as high aspect ratio structures, porous structures, and regular crack structures) required for precision devices such as microsensors and functional microarrays, it is difficult to accurately control the molding quality and morphology when using polymer-based composite materials with traditional electric field-assisted direct writing technology.

[0007] To this end, we propose a temperature-electric composite field assisted direct writing system and method. Summary of the Invention

[0008] Based on this, it is necessary to provide a temperature-electric composite field assisted direct writing forming system and method to address the technical problems of traditional electric field assisted direct writing forming technology in the manufacture of complex structures of polymer-based composite materials, such as difficulty in achieving high-precision forming, inability to effectively control the forming morphology, and difficulty in constructing cross-scale three-dimensional structures. This will significantly improve the precision and morphology control of polymer-based composite materials in the manufacture of complex structures, and is particularly suitable for the preparation of precision devices such as microsensors and functional microarrays, and realize the rapid forming of cross-scale, high-precision three-dimensional structures.

[0009] The first aspect of the present invention provides a temperature-electric composite field-assisted direct writing system, comprising a writing unit, a temperature control system, an electric field generation module, and a post-processing unit. The writing unit includes a three-dimensional motion platform, a feed syringe, a plastic-steel needle, and a thrust control device, designed to achieve multi-dimensional precision printing. By controlling material extrusion through air pressure and combining it with the precise movement of the three-dimensional motion platform, the system can print two-dimensional or three-dimensional structures. The temperature control system integrates a coolant circulation pipeline, a low-temperature module containing a coolant circulation pump, and a high-temperature module containing a heating resistor to precisely control the substrate temperature field to meet printing requirements in different modes. The electric field generation module uses a high-voltage power supply and connectors to establish a high-voltage electric field between the plastic-steel needle and the substrate, assisting in material extrusion and molding. The post-processing unit includes a freeze dryer to remove ice crystals in the low-temperature mode and form a porous structure. Through the synergistic effect of the temperature and electric fields, this system significantly improves the molding precision of polymer-based composite materials and the ability to fabricate complex structures. This system provides strong support for the manufacture of precision devices such as microsensors and functional microarrays, and solves the problems of low molding precision and difficult morphology control in traditional technologies.

[0010] In other embodiments, the system also includes a freeze dryer in the post-processing unit for ice crystal sublimation in low-temperature mode. The introduction of the freeze dryer allows for rapid removal of ice crystals from printed samples at low temperatures, forming a stable porous structure and further improving the performance and stability of the printed samples. This design enables the system to better preserve the original properties of polymer-based composite materials while achieving precise molding of complex structures.

[0011] A second aspect of the present invention provides a temperature-electric composite field-assisted direct writing method, comprising the steps of preparing a polymer-based composite printing substrate, feeding the printing substrate into a writing unit, controlling the substrate temperature field via a temperature control system, applying a voltage between a plastic-steel needle and the substrate via a high-voltage power supply to form a Taylor cone jet, controlling the deposition jet path using a three-dimensional motion platform, and employing a post-processing unit to remove ice crystals or induce regular cracks using thermal stress, depending on the mode. This method achieves high-precision molding of polymer-based composite materials in the manufacture of complex structures by precisely controlling temperature and electric field parameters. In low-temperature mode, a coolant circulation device controls the platform temperature, rapidly freezing the jet into cylindrical lines. Freeze-drying is then combined to remove ice crystals and form a multi-level pore structure. In high-temperature mode, an electric heating tube heats the printing platform, which is controlled by a temperature sensor, and thermal stress is used to induce regular cracks in the printed structure. This method effectively addresses the difficulty of precision control in the manufacture of complex polymer-based composite structures. Through the combined action of temperature and electric fields, it enables the rapid fabrication of high-precision three-dimensional structures across multiple scales, making it particularly suitable for the fabrication of precision devices such as microsensors and functional microarrays.

[0012] In other embodiments, the polymer matrix includes one or more of polyurethane, polyvinyl pyrrolidone, and polyvinyl alcohol; the nanofiller includes one or more of nanocarbon fibers, nanocarbon black, graphene, and carbon nanotubes; and the solvent includes one or more of water and dimethylformamide. This diverse selection of materials enables the method to adapt to the performance requirements of polymer-based composite materials in different fields, further expanding its scope of application. By adjusting the ratio and type of polymer matrix, nanofiller, and solvent, printed samples with different properties and morphologies can be prepared to meet the manufacturing needs of different precision devices.

[0013] In other embodiments, the direct writing molding method under low-temperature assisted conditions includes mixing and dissolving the polymer matrix, nanofiller and solvent and ultrasonically dispersing them, loading the solution into a feed syringe with a plastic steel needle, setting the temperature of the coolant circulation pump, adjusting the working distance between the needle and the substrate, applying voltage and air pressure to form a jet, printing according to the mapping software path, and transferring to a freeze dryer for freeze-drying molding. The optimized combination of these steps enables low-temperature assisted printing to achieve high-precision, high-resolution three-dimensional structure molding, while forming a stable porous structure. By precisely controlling parameters such as temperature, voltage, and air pressure, the performance and morphology of the printed sample can be further optimized, thereby improving its application value in precision devices.

[0014] In other embodiments, depending on the quality of the polymer matrix, the temperature of the substrate platform, the working distance between the needle and the substrate, and the voltage and pressure, either a multi-level pore structure or a micro-pillar structure can be formed. This structural diversity provides greater flexibility and adaptability for the preparation of complex three-dimensional structures. By adjusting the printing parameters, the internal structure and morphology of the printed sample can be precisely controlled to meet the complex structure requirements of different fields.

[0015] In other embodiments, the ambient humidity is controlled to ≤30% before printing, and frost is removed from the silicon wafer surface. This step effectively reduces the impact of environmental factors on the printing process and improves the stability and consistency of the printed samples. By strictly controlling the printing environment, a smooth printing process can be ensured, improving the quality and performance of the printed samples.

[0016] In other examples, a PU film attached to copper tape is used as a substrate, and after printing, the sample is transferred to the freeze dryer to mitigate freeze-drying cracking. This design effectively solves the problem of sample cracking during the freeze-drying process and improves the integrity and performance of the printed sample. By introducing PU film and copper tape as a substrate, it can provide better support and protection during the freeze-drying process, reduce stress concentration within the sample, and thus prevent the occurrence of cracking.

[0017] In other embodiments, a high-temperature-assisted direct-write method includes dissolving a polymer matrix, nanofiller, and solvent, and ultrasonically dispersing the mixture; loading the solution into a feed syringe with a plastic-steel needle; setting the temperature of the heating platform; adjusting the working distance between the needle and the substrate; applying a square wave voltage and air pressure; printing according to the mapping software path; and inducing regular microcracks in the lines using thermal stress. The optimized combination of these steps enables high-temperature-assisted printing to achieve high-precision, high-resolution line formation, while also forming a stable, regular microcrack structure. By precisely controlling parameters such as temperature, voltage, and air pressure, the performance and morphology of the printed lines can be further optimized, enhancing their application value in precision devices.

[0018] As described in other embodiments, during multi-layer printing, the needle is raised after each layer is stacked to increase the working distance by 0.1 mm. This design effectively solves the problem of loose interlayer bonding during multi-layer printing, improving the overall strength and stability of the printed structure. By precisely controlling the working distance of each printed layer, it ensures tight interlayer bonding and seamless gaps, thereby improving the overall performance and reliability of the printed structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the temperature-electricity composite field assisted direct writing system used in the present invention.

[0020] Figure 2 Schematic diagram of low-temperature assisted manufacturing of multi-level hole grid structure.

[0021] Figure 3 Schematic diagram of low-temperature assisted fabrication of porous micro-pillar arrays.

[0022] Figure 4 Schematic diagram of high temperature assisted manufacturing of regular micro-crack lines.

[0023] In the figure: 1. Syringe feed air port; 2. Z-axis motion platform; 3. Feed syringe; 4. Plastic steel needle; 5. Alligator clip; 6. Heating resistor wire; 7. Coolant circulation pipeline; 8. X- and Y-axis motion platform; 9. Coolant circulation pump; 10. High-voltage power supply; 11. Freeze dryer. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0025] Example 1

[0026] like Figure 1As shown, this embodiment provides a temperature-electric composite field assisted direct writing molding system, the structure of which includes a writing unit, a temperature control system, an electric field generation module and a post-processing unit; the present invention is based on the electric field assisted direct writing process, combined with temperature field assisted molding, and has two working modes: high temperature and low temperature: the high temperature mode uses thermal stress to induce regular cracks in the printed structure, and the low temperature mode can achieve rapid preparation of cross-scale, high-precision three-dimensional structures. Compared with the existing technology, the present invention effectively solves the problem of precision control of polymer-based composite materials in the manufacture of complex structures, and is particularly suitable for the preparation of precision devices such as microsensors and functional microarrays, and has significant technical advantages and application value.

[0027] Specifically, the writing unit in this embodiment is used to achieve a multi-dimensional printing effect, and its structure includes:

[0028] Syringe feeding air port 1: used to connect the air pump to provide air pressure to the feeding syringe and control material extrusion.

[0029] The three-dimensional motion platform includes an x-axis and y-axis motion platform 8 and a z-axis motion platform 2. The x-axis and y-axis motion platform 8 is used to control the movement of the nozzle in the horizontal direction (X and Y axes) to realize two-dimensional pattern printing. The z-axis motion platform 2 is used to control the movement of the nozzle in the vertical direction (Z axis) to realize multi-layer printing based on the two-dimensional pattern.

[0030] Feed syringe 3: used to store printing materials and control material extrusion through air pressure.

[0031] Plastic-steel needle 4: installed at the lower end of the feeding syringe, the material is extruded through the needle to form a jet. The inner diameter of the plastic-steel needle 4 is 160 μm, which is used to prevent clogging of the nanofiller.

[0032] The temperature control system in this embodiment is used to control the temperature of the substrate, including providing both heating and cooling effects. In the low-temperature mode, the lower the substrate temperature, the smaller the size of the micropores formed after freeze-drying. Its structure includes:

[0033] Heating resistance wire 6: used to heat the printing platform to achieve high-temperature auxiliary printing.

[0034] Coolant circulation line 7: Built into the low-temperature printing platform, it controls the platform temperature through coolant circulation.

[0035] Coolant circulation pump 9: used to drive the coolant circulation and control the temperature of the low-temperature printing platform.

[0036] The electric field generating module in this embodiment is used to provide a high-voltage electric field, and its structure includes:

[0037] Connector 5: used to clamp the positive pole of the power supply onto the plastic-steel needle to form an electric field.

[0038] High voltage power supply 10: used to provide a high voltage electric field to assist in material extrusion and molding.

[0039] The post-processing unit in this embodiment is used to remove ice crystals, and its structure includes a freeze dryer 11: used to remove ice crystals in the printed sample to form a porous structure.

[0040] This system regulates the substrate temperature field through a heating or cooling device, and establishes a high-voltage electric field between the nozzle and the substrate through a high-voltage power supply. During low-temperature assisted printing, the coolant circulation pump 9 drives the coolant to circulate in the coolant circulation pipeline 7 to control the temperature of the low-temperature printing platform. During high-temperature assisted printing, the heating resistor wire 6 heats the printing platform to achieve high-temperature assisted printing. The material in the feed syringe 3 is extruded by the air pressure provided by the syringe feed air port 1, and forms a jet through the plastic steel needle 4. The connector 5 clamps the positive pole of the high-voltage power supply 10 on the plastic steel needle to form a high-voltage electric field to assist the extrusion and molding of the material. The x- and y-axis motion platforms 8 and the z-axis motion platform 2 control the movement of the nozzle to achieve printing of two-dimensional or three-dimensional structures. After printing is completed, the sample passes through a freeze dryer 11 to remove ice crystals to form a porous structure.

[0041] Example 2

[0042] This embodiment provides a temperature-electric composite field assisted direct writing method, which is characterized by comprising:

[0043] Next steps:

[0044] (a) preparing a polymer-based composite material printing substrate, comprising a polymer matrix, a nanofiller, and a solvent;

[0045] (b) inputting the prepared printing substrate into the writing unit and printing according to the path provided by the drawing software;

[0046] (c) The temperature field of the substrate is controlled by the temperature control system: the low temperature mode is set to -30℃ to 0℃, the high temperature mode is set to -30℃ to 0℃, and the low temperature mode is set to -30℃ to 0℃.

[0047] Temperature mode setting 40℃-100℃;

[0048] (d) A voltage of 1000V to 5000V is applied between the plastic-steel needle 4 and the substrate through a high-voltage power supply 10, forming a

[0049] into a Taylor cone jet;

[0050] (e) Path-controlled deposition jet combined with a three-dimensional motion platform;

[0051] (f) In the low-temperature mode, a freeze dryer 11 is used to remove ice crystals to form a porous structure, and in the high-temperature mode, thermal stress is used to induce regular cracks.

[0052] The polymer matrix includes one or more of polyurethane, polyvinyl pyrrolidone, and polyvinyl alcohol; the nanofiller includes one or more of nanocarbon fiber, nanocarbon black, graphene, and carbon nanotube; and the solvent includes one or more of water and dimethylformamide, which are fused in a specific proportion.

[0053] In this embodiment, the ambient humidity must be controlled at ≤30% before molding and printing, and any frost on the silicon wafer surface must be removed. Cold silicon wafers exposed to air will form frost on their surface, and excessive frost can affect printing. Therefore, when the indoor humidity is below 30%, frost formation is slow and will not affect the printing process. However, the frost on the silicon wafer surface must be removed before printing begins.

[0054] At the same time, a temperature-electric composite field assisted direct writing method in this embodiment also includes two modes: low-temperature assisted printing and high-temperature assisted printing.

[0055] The direct writing method under low temperature assisted conditions includes the following steps:

[0056] Material preparation: Mix and dissolve the polymer matrix, nanofiller and solvent using a magnetic stirring table.

[0057] Dispersion treatment: ultrasonically disperse the dispersion for 30 min to ensure that the nanofiller is evenly dispersed.

[0058] Loading and installation: Load the cooled solution into the syringe 3, install the plastic-steel needle 4 at the lower end, install the syringe in the writing unit, connect the air pump, and clamp the positive pole of the power supply to the needle through the connector 5.

[0059] Path compilation: Compile the printing path as needed, use drawing software (such as CAD) to draw the grid path and form a specific format, and input it into the printer.

[0060] Temperature control: Turn on the coolant circulation pump 9 and set the temperature to -10℃~-15℃. After the temperature drops to the target temperature, place the silicon wafer on the cooling platform. The temperature range is room temperature~-30℃. The lower the temperature, the smaller the micropores formed after freeze-drying.

[0061] Working distance adjustment: Adjust the distance from the lower end of the needle to the silicon wafer (working distance) to 2-5mm.

[0062] Electric field and air pressure settings: After confirming the starting position of the path in the silicon wafer, move the control motion platform and the needle away, turn on the voltage to 1800v-2500v and the air pressure to 20kpa-50kpa to form a stable vertical conical jet.

[0063] Printing start: Click to start printing, the needle will automatically move to the previously set starting position to start printing, and the aqueous solution will quickly freeze into a cylindrical line when it contacts the moving substrate.

[0064] Layer adjustment: When there are many stacked layers, raise the needle appropriately, increase the working distance, and increase the air pressure.

[0065] Freeze-drying process: After printing is completed, it needs to be transferred to the freeze dryer 11 for freeze drying to remove ice crystals. Liquid nitrogen is used to maintain a low temperature environment around the sample during the transfer process. The freeze dryer maintains a low temperature of -85°C and an air pressure of 0.13 bar until the sample is completely freeze-dried. The sample cannot be removed from the silicon wafer before it is freeze-dried. The sample and the silicon wafer are sent into the freeze dryer together. Due to the different freeze-drying efficiencies of the sample surface and the bottom surface in contact with the silicon wafer, slight deformations will also occur during the freeze-drying process. This uneven deformation will cause excessive stress inside the sample and cause cracking. The solution is to stick a layer of copper tape on the PI film, and stick one side of the PI film on the silicon wafer during printing with the copper tape facing up. When transferring the sample to the freeze dryer, only the membrane can be removed from the silicon wafer. The flexible membrane can effectively alleviate cracking during the freeze-drying process.

[0066] Structural observation: After taking out the sample, it was observed under a microscope and found to have a multi-level pore structure, such as Figure 2 As shown in the figure, the macroscopic pores are the rectangular holes between the lines formed by the grid paths, and the microscopic pores are the micron-sized pores formed on the surface of the lines due to the sublimation of freeze-dried ice crystals.

[0067] The width of the line can be controlled by the flow rate controlled by the air pressure voltage and the moving speed of the printing platform. The greater the flow rate, the larger the line width, and the faster the speed, the smaller the line width.

[0068] In the above method, the formed sample has a multi-level pore structure, and the sample operation steps of using low temperature assisted manufacturing of pillar arrays include the following steps:

[0069] Material preparation: The polymer matrix, nanofiller and solvent are mixed and dissolved using a magnetic stirring table. The mass ratio of the polymer matrix needs to be increased compared to the above-mentioned formation of the multi-level pore structure sample.

[0070] Dispersion treatment: ultrasonically disperse the dispersion for 30 min to ensure that the nanofiller is evenly dispersed.

[0071] Loading and installation: Load the cooled solution into the syringe 3, install the plastic-steel needle 4 at the lower end, install the syringe in the writing unit, connect the air pump, and clamp the positive pole of the power supply to the needle through the connector 5.

[0072] Path compilation: Compile the printing path as needed, use drawing software (such as CAD) to draw the grid path and form a specific format, and input it into the printer.

[0073] Temperature control: Turn on the coolant circulation pump 9 and set the temperature to -10℃~15℃. After the temperature drops to the target temperature, place the silicon wafer on the cooling platform. The temperature range is room temperature~-30℃. The lower the temperature, the smaller the micropores formed after freeze-drying.

[0074] Working distance adjustment: Adjust the distance from the lower end of the needle to the silicon wafer (working distance) to 0.2mm-0.5mm.

[0075] Electric field and air pressure settings: After confirming the starting position of the path in the silicon wafer, move the control motion platform and the needle away, turn on the voltage to 1800v-2500v and the air pressure to 20kpa-50kpa to form a stable vertical conical jet.

[0076] Printing start: Click to start printing, the needle will automatically move to the previously set starting position to start printing, and the aqueous solution will quickly freeze into a cylindrical line when it contacts the moving substrate.

[0077] Layer adjustment: When there are many stacked layers, raise the needle appropriately, increase the working distance, and increase the air pressure.

[0078] Freeze drying: After printing is completed, it needs to be transferred to the freeze dryer 11 for freeze drying to remove ice crystals.

[0079] Structural observation: After taking out the sample, micro-pillar structure was found through microscope observation, such as Figure 3 shown.

[0080] In this embodiment, the direct writing method under high temperature auxiliary state includes the following steps:

[0081] Material preparation: Mix and dissolve the polymer matrix, nanofiller and solvent using a magnetic stirrer.

[0082] Dispersion treatment: ultrasonically disperse the dispersion for 30 min to ensure that the nanofiller is evenly dispersed.

[0083] Loading and installation: Fill the solution into the syringe 3, install the plastic steel needle 4 at the lower end, install the syringe in the writing unit, connect the air pump, and clamp the positive pole of the power supply to the needle through the connector 5.

[0084] Path compilation: Compile the printing path as needed, use mapping software to draw the grid path and form a specific format, and input it into the printer.

[0085] Temperature control: Turn on the heating platform and set the temperature to 40℃-100℃. After the temperature rises to the target temperature, place the PDMS film on the heating platform as the printing base.

[0086] Working distance adjustment: Adjust the distance from the lower end of the needle to the silicon wafer (working distance) to 0.1mm-0.5mm.

[0087] Electric field and air pressure settings: After confirming the starting position of the path in the silicon wafer, move the control motion platform and the needle away, turn on the voltage, set the square wave bias to 0, the amplitude to 2000V-4000V, the frequency to 200Hz-500Hz, and the air pressure to 50kPa-100kPa.

[0088] Print Start: Click Start Printing, and the needle will automatically move to the previously set starting position to start printing, obtaining the desired graphics. If multiple layers are required, the working distance will be raised by 0.1mm for each layer.

[0089] Structural observation: After printing, regular micro cracks were found in the lines through microscope observation, such as Figure 4 As shown, this is due to the result of thermal stress.

[0090] Multi-layer printing optimization: When printing multiple layers, the working distance of each layer is precisely controlled to ensure close bonding between layers and improve the overall strength of the printed structure.

[0091] Experimental Example 1

[0092] This experimental example 1 provides a low-temperature assisted manufacturing multi-level hole grid structure;

[0093] The steps include:

[0094] Polyurethane, Ketjen Black and deionized water were mixed at a mass ratio of 1:1:8 on a magnetic stirring table, and the stirring table was heated to 40°C to accelerate dissolution;

[0095] The dispersion was ultrasonically dispersed for 30 min;

[0096] Pour the cooled solution into the syringe, install the plastic steel needle at the lower end, install the syringe in the writing unit, connect the air pump, and clamp the positive pole of the power supply to the needle through the connector;

[0097] Compile the printing path as needed, use the drawing software CAD to draw the grid path in dxf format, and input it into the printer;

[0098] Turn on the coolant circulation pump and set the temperature to -12°C;

[0099] After the temperature drops to -12°C, place the silicon wafer on a cooling platform;

[0100] Adjust the distance between the lower end of the needle and the silicon wafer (working distance) to 2 mm;

[0101] After confirming the starting point of the path in the silicon wafer, the control motion platform is moved away, the needle is removed, and the voltage is turned on to 2100V and the air pressure to 30kPa to form a stable vertical cone jet;

[0102] Click Start Printing, and the needle will automatically move to the previously set starting position to start printing. When the aqueous solution contacts the moving substrate, it will quickly freeze and retain the shape of a cylindrical line.

[0103] When stacking a large number of layers, raise the needle appropriately, increase the working distance, and increase the air pressure;

[0104] After printing is completed, it needs to be transferred to a freeze dryer for freeze drying to remove ice crystals. Liquid nitrogen is used to maintain a low temperature environment around the sample during the transfer process.

[0105] The freeze dryer is maintained at -85°C and 0.13 bar pressure until the sample is completely freeze-dried;

[0106] After the sample was taken out and observed under a microscope, it was found that it had a multi-level pore structure. The macroscopic pores were rectangular holes between the lines formed by the grid paths, and the microscopic pores were micron-sized pores formed on the surface of the lines due to the sublimation of freeze-dried ice crystals.

[0107] Experimental Example 2:

[0108] This experimental example 1 provides a low-temperature assisted manufacturing micro-pillar array structure;

[0109] Polyvinyl alcohol, carbon black and deionized water were mixed in a mass ratio of 1.3:1:10 on a magnetic stirring table, and the stirring table was heated to 40°C to accelerate dissolution;

[0110] Place the cooled polyvinyl pyrrolidone aqueous solution into the syringe, install a plastic steel needle at the lower end, install the syringe in the writing unit, connect the air pump, and clamp the positive electrode of the power supply to the needle through the connector;

[0111] Compile the printing path as needed, draw the path in CAD and export it to dxf format, then input it into the printer;

[0112] Turn on the coolant circulation pump and set the temperature to -15°C;

[0113] After the temperature drops to -15°C, place the silicon wafer on the cooling platform;

[0114] Adjust the distance between the lower end of the needle and the silicon wafer (working distance) to 0.5 mm;

[0115] After confirming the starting point of the path in the silicon wafer, the control motion platform is moved away, the needle is removed, and the voltage is turned on to 1700V and the air pressure is turned on to 5kPa to form a stable vertical conical jet;

[0116] Click Start Printing, and the needle will automatically move to the previously set starting position to start printing. When the jet contacts the low-temperature substrate, it will quickly freeze upwards. As the substrate moves, the jet will jump to the next point and repeat the previous process, finally forming micro-pillars along the path;

[0117] After printing is completed, it needs to be transferred to a freeze dryer for freeze drying to remove ice crystals. Liquid nitrogen is used to maintain a low temperature environment around the sample during the transfer process.

[0118] The freeze dryer is maintained at -85°C and 0.13 bar pressure until the sample is completely freeze-dried;

[0119] Microscopic examination of the sample revealed pores on the surface of each pillar. Each micropillar has a "chicken leg" shape, narrow at the bottom and wide at the top. This is because the freezing rate is faster at the bottom, closest to the base, and slows down as it moves upwards, resulting in this morphology.

[0120] Experimental Example 3:

[0121] This experimental example 3 provides a high temperature assisted method for manufacturing micro crack lines, including the following steps:

[0122] Carbon nanofibers, TX-100 surfactant, and dimethylformamide were prepared into a dispersion at a ratio of 1:1:12 at 40 °C using a magnetic stirrer;

[0123] The dispersion was ultrasonically dispersed for 30 min;

[0124] Polyvinyl pyrrolidone was added to the dispersion at a mass ratio of 4:1 to carbon nanofibers and stirred with a magnetic stirrer for 5 h until completely dissolved;

[0125] Pour the solution into the syringe, install a 160μm plastic-steel needle at the lower end, install the syringe in the writing unit, connect the air pump, and clamp the positive electrode of the power supply to the needle through the connector;

[0126] Compile the printing path as needed, draw the grid path with CAD and export it in dxf format, then input it into the printer;

[0127] Turn on the heating platform and set the temperature to 50°C;

[0128] After the temperature rises to the target temperature, the PDMS film is placed on the heating platform as a printing substrate;

[0129] Adjust the distance between the lower end of the needle and the silicon wafer (working distance) to 0.1 mm;

[0130] After confirming the starting point of the path in the silicon wafer, move the control motion platform and the needle away, turn on the voltage, set the square wave bias to 0, the amplitude to 3000V, the frequency to 200Hz, and the air pressure to 55kPa;

[0131] Click Start Printing, the needle will automatically move to the previously set starting position to start printing, and the required graphics will be obtained. During the heating process, regular micro cracks will be generated in the lines due to thermal stress;

[0132] The present invention provides a temperature-electric composite field-assisted direct writing forming method and system, which realizes the rapid preparation of cross-scale, high-precision three-dimensional structures and the precise control of regular crack structures through two modes: low-temperature assisted printing and high-temperature assisted printing. Low-temperature assisted printing uses a coolant circulation device to control the platform temperature, so that the jet quickly freezes into cylindrical lines after falling on the substrate, and combines freeze-drying to remove ice crystals to form a multi-level pore structure. High-temperature assisted printing uses electric heating tubes to heat the printing platform, cooperates with temperature sensors to control the temperature, and uses thermal stress to induce regular cracks in the printed structure. By optimizing the steps of material preparation, temperature control, working distance adjustment, electric field and air pressure setting, the printing quality and efficiency are improved. Experimental results show that the present invention effectively solves the problem of precision control of polymer-based composite materials in the manufacture of complex structures, is particularly suitable for the preparation of precision devices such as microsensors and functional microarrays, and has significant technical advantages and application value.

[0133] The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. Any modifications may be made within the scope of protection of the present invention.

Claims

1. A temperature-electricity composite field assisted direct writing system, characterized in that: include: Writing unit: comprising a three-dimensional motion platform, a feeding syringe (3), a plastic steel needle (4) and a thrust control device (1); Temperature control system: a low-temperature module integrating a coolant circulation pipeline (7), a coolant circulation pump (9), and a high-temperature module containing a heating resistor (6), for controlling the substrate temperature field; Electric field generating module: a high-voltage power supply (10) is connected to the plastic-steel needle (4) via a connector (5), and a high-voltage electric field is established between the needle (4) and the substrate.

2. The temperature-electricity composite field assisted direct writing system according to claim 1, characterized in that: The invention also comprises a post-processing unit: a freeze dryer (11) for sublimation of ice crystals in a low temperature mode.

3. A temperature-electricity composite field assisted direct writing method, characterized in that: The following steps are involved: (a) preparing a polymer-based composite material printing substrate, comprising a polymer matrix, a nanofiller, and a solvent; (b) inputting the prepared printing substrate into the writing unit and printing according to the path provided by the drawing software; (c) Controlling the substrate temperature field through a temperature control system: the low-temperature mode is set to -30°C to 0°C, and the high-temperature mode is set to 40°C to 100°C; (d) applying a voltage of 1000V to 3000V between the plastic-steel needle (4) and the substrate through a high-voltage power supply (10) to form a Taylor cone jet; (e) Path-controlled deposition jet combined with a three-dimensional motion platform; (f) In the low-temperature mode, a freeze dryer (11) is used to remove ice crystals to form a porous structure, and in the high-temperature mode, thermal stress is used to induce regular cracks.

4. The temperature-electricity composite field assisted direct writing method according to claim 3, characterized in that: The polymer matrix includes one or more of polyurethane, polyvinyl pyrrolidone, and polyvinyl alcohol; the nanofiller includes one or more of nanocarbon fiber, nanocarbon black, graphene, and carbon nanotube; and the solvent includes one or more of water and dimethylformamide.

5. The temperature-electricity composite field assisted direct writing method according to any one of claims 3 to 4, characterized in that: The direct writing method under low temperature assisted state includes: (1) The polymer matrix, nanofiller and solvent were mixed and dissolved and ultrasonically dispersed for 30 minutes; (2) The solution is loaded into a feeding syringe (3) with a plastic steel needle (4) and connected to the positive electrode of a high voltage power supply (10); (3) Setting the temperature of the coolant circulation pump (9) to -30°C to 0°C, and placing the silicon wafer on the cooling platform; (4) adjusting the working distance between the needle (4) and the substrate to 0.5-3 mm, applying a voltage of 1000V-3000V and an air pressure of 5-50 kPa to form a jet; (5) Print according to the path of the drawing software, and the jet contacts the low-temperature substrate and freezes instantly; (6) Transfer to a freeze dryer (11) for freeze drying and forming to form a sample.

6. The temperature-electricity composite field assisted direct writing method according to claim 5, characterized in that: In the above steps, the sample formed includes one of a multi-level pore structure and a micro-pillar structure according to the quality of the polymer matrix, the temperature of the substrate platform, the working distance between the needle (4) and the substrate, and the voltage and gas pressure; Among them, the molding step of the micro-pillar structure sample requires a larger polymer matrix weight and a lower substrate temperature than the molding step of the multi-level pore structure sample; when the working distance is 0.5-3mm, a multi-level pore structure is formed; when the working distance is 0.2-0.5mm, a micro-pillar array is formed.

7. The temperature-electricity composite field assisted direct writing method according to claim 5, characterized in that: Before printing, the ambient humidity must be controlled at ≤30% and the frost on the silicon wafer surface must be cleaned.

8. The temperature-electricity composite field assisted direct writing method according to claim 5, characterized in that: Pi film attached with copper tape was used as the substrate, and after printing, the sample was transferred to a freeze dryer (11) to alleviate freeze-drying cracking.

9. The temperature-electricity composite field assisted direct writing method according to any one of claims 3 to 4, characterized in that: Direct writing method under high temperature assisted state, including: (1) The polymer matrix, nanofiller and solvent were mixed and dissolved and ultrasonically dispersed for 30 minutes; (2) The solution is loaded into a feeding syringe (3) with a plastic steel needle (4) and connected to the positive electrode of a high voltage power supply (10); (3) Set the heating platform temperature to 40°C-100°C and place the PDMS membrane on the heating platform; (4) Adjust the working distance between the needle (4) and the substrate to 0.1-0.5 mm; (5) Apply square wave voltage: bias 0V, amplitude 2000V-4000V, frequency 100-500Hz, with 50-100kPa air pressure; (6) Print according to the path of the drawing software, and the thermal stress induces the lines to produce regular micro cracks.

10. The temperature-electricity composite field assisted direct writing method according to claim 9, characterized in that: When printing multiple layers, the needle (4) is raised after each layer is stacked to increase the working distance by 0.1 mm.

Images