Coaxial needle multi-process real-time switching printing method for curved surface conformal electronic circuit

Abstract

A coaxial needle head multi-process real-time switching printing method for a curved surface conformal electronic circuit comprises the steps that firstly, a curved surface dielectric layer structure needed by an FFF printing target is utilized, and then printing tracks of a conductive structure and a functional structure are designed; a micro-scale conductive structure and pins at the two end points of the micro-scale conductive structure are manufactured on the surface of an FFF printed supporting structure through a coaxial needle head multi-process switching printing technology, finally, a functional layer structure is printed at the pins through an extrusion printing process, and physical connection and electrical conduction of the conductive structure and the functional structure are achieved through connection. Rapid and efficient integrated manufacturing of the curved surface conformal electronic circuit functional structure is achieved, connection and conduction of the micro-scale core-shell conductive structure and the functional structure are further achieved, integrated manufacturing of the curved surface conformal electronic circuit functional structure is achieved through multi-material 3D printing path planning, the process is simple and efficient, and the production cost is low. And the method has the advantages of low cost and high efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of multi-material additive manufacturing of curved surface conformal electronic circuits, and in particular relates to a coaxial needle multi-process real-time switching printing method for curved surface conformal electronic circuits. Background Art

[0002] Curved conformal electronic circuits, due to their excellent mechanical, electrical, and magnetic properties and strong adaptability to extreme environments, hold great promise for applications in functional structural devices such as conformal antennas and frequency selective surfaces. Curved conformal electronic circuits consist of three components: a dielectric layer, a conductive layer, and a functional layer. The dielectric layer must provide excellent mechanical properties, while the conductive and functional layers must enable specific electromagnetic control or environmental sensing. Therefore, the integrated design and manufacturing of these three components is crucial for improving the performance and application of curved electronic circuits.

[0003] Existing curved conformal electronic circuits (Self-healing Kirigami Assembly Strategy for Conformal Electronics, Advanced functional materials, 2021; Wrap-like transfer printing for three-dimensional curvy electronics, Science Advances, 2023) are manufactured through a strategy of independent processing + manual assembly, in which the conductive layer uses traditional processes such as screen printing, inkjet processing, and photolithography to manufacture a predetermined conductive structure on the surface of the dielectric layer. Commercial functional devices are then welded on the surface of the conductive layer through manual assembly, and the entire structure is manufactured in conjunction with corresponding post-processing processes;

[0004] However, the manufacturing method of independent processing + manual assembly has problems such as difficult structural design, low manual assembly precision, and uncontrollable structural mechanical properties. The inkjet printing / screen printing / photolithography process has problems such as complex process, low efficiency, and low positioning accuracy of conductive structure. For curved electronic circuits including dielectric layers, conductive layers and functional layers, the existing manufacturing methods mentioned cannot meet the requirements of manufacturing stability and reliability.

[0005] Multi-material 3D printing technology enables rapid, on-demand fabrication of dielectric and conductive layers through nozzle design and print path planning. However, the surface morphology and roughness of the dielectric layer printed using FFF (Fractured Forming) are poor, severely limiting the stability and precision of the conductive layer structure. Furthermore, the functional layer is typically connected to the conductive layer using standard commercial electronic components through manual soldering (Wrap-like transfer printing for three-dimensional curvy electronics, Science Advances, 2023). This solder joint structure is prone to detachment and significantly affects the electromagnetic properties of the curved heterogeneous functional structure. While coaxial needle electrostatic printing (Coaxial Electrohydrodynamic Printing of Microscale Core–Shell Conductive Features for Integrated Fabrication of Flexible Transparent Electronics, ACS Applied Materials & Interfaces 2024) can directly and stably print microscale conductive structures on rough FFF surfaces, its endpoints are covered by the encapsulation layer, preventing direct connection to electronic components. This results in low overall manufacturing efficiency and complex processes for existing curved electronic circuits. The above manufacturing methods cannot meet the demand for integrated manufacturing of curved electronic circuits including dielectric layers, conductive layers and functional layers, and there is currently no mature and stable integrated manufacturing technology. Summary of the Invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a coaxial needle multi-process real-time switching printing method for curved surface conformal electronic circuits, which solves the problem that the existing FFF rough curved surface microscale core-shell conductive structure cannot be directly connected to electronic components, resulting in its limited function. The coaxial needle multi-process switching printing technology is used to realize the integrated manufacturing of the rough curved surface microscale core-shell conductive structure and the conductive contact structure at both ends thereof, and the resistance functional device is printed at the conductive contact position by extrusion printing, thereby realizing the rapid and efficient integrated printing of curved surface conformal electronic circuits, and further realizing the connection and conduction between the microscale conductive structure and the functional structure, overcoming the problem of easy detachment caused by manual welding of commercial electronic devices; in addition, the coaxial needle multi-process real-time switching printing path planning is used to realize the integrated manufacturing of the conductive layer and the functional layer on the surface of the FFF printed curved surface. The process is simple and efficient, without a large amount of material waste, and has the advantages of low cost and high efficiency.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A coaxial needle multi-process real-time switching printing method for curved conformal electronic circuits first uses FFF to print the curved dielectric layer structure required by the target, then designs the printing trajectories of the conductive structure and functional structure, and directly manufactures the microscale core-shell conductive structure and the pins of its two end points on the surface of the rough curved support structure printed by FFF through coaxial needle multi-process switching printing technology. Finally, the functional layer structure is printed at the pins through the extrusion printing process to achieve physical connection and electrical conduction between the conductive structure and the functional structure.

[0009] A coaxial needle multi-process real-time switching printing method for curved surface conformal electronic circuits includes the following steps:

[0010] Step 1: The multi-material 3D printing platform is equipped with an FFF (fused filament fabrication) print head, a coaxial print head, and an extrusion print head to manufacture the dielectric layer, the conductive layer, and the functional layer respectively.

[0011] Step 2: Select the dielectric layer material that meets the requirements and use the FFF printing nozzle to manufacture the flat / curved dielectric layer;

[0012] Step 3: Select conductive and insulating materials as printing inks for micro-scale conductive structures, inject them into the printing syringes respectively, connect them to the coaxial printing needles to form a coaxial printing nozzle, and fix it to the multi-material 3D printing platform;

[0013] Step 4: Use coaxial needle multi-process switching technology to print microscale core-shell conductive structures and conductive pins on the rough surface printed by FFF, preparing for the physical connection and electrical conduction between the microscale core-shell conductive structure and the functional structure. The coaxial printing needle has five printing modes: Mode 1 is the coaxial extrusion printing of the core-shell conductive structure with the encapsulation layer by the inner and outer needles, Mode 2 is the inner needle extrusion printing of the pins, Mode 3 is the outer needle extrusion printing of the encapsulation structure, Mode 4 is the coaxial electrostatic printing of the microscale core-shell conductive structure by the inner and outer needles after electrostatic application, and Mode 5 is the inner needle printing of the microscale conductive structure after electrostatic application;

[0014] Step 5: By optimizing the printing process parameters, controlling the air pressure of the inner and outer needles, and switching the voltage during the printing process, the inner needle extrusion printing process is first used to manufacture the pins during the printing process. Before the pin printing is completed, the inner needle extrusion printing process is switched to the inner and outer needle coaxial printing process to manufacture the core-shell conductive structure with the encapsulation layer. After the core-shell conductive structure with the encapsulation layer is stably manufactured, the voltage is turned on to realize coaxial electrostatic printing of the microscale core-shell conductive structure. Before the printing of the microscale conductive structure is completed, the voltage is turned off, and the coaxial electrostatic printing process is switched to coaxial extrusion printing. After the printing is stable, the coaxial extrusion printing is switched to the inner needle extrusion printing process to manufacture the pins; repeat the above printing process to print a microscale core-shell conductive structure array with pin structures at both ends on the surface of the dielectric layer, so that it is connected and conductive with the functional layer structure;

[0015] Step 6: Using an in-situ high-temperature sintering process, the microscale core-shell conductive structure and pins are in-situ sintered and solidified according to the sintering temperature and sintering time to improve their conductivity and bonding with the substrate structure;

[0016] Step 7: Select the functional layer material according to the requirements. After extrusion printing process optimization and printing path planning, print the functional layer between the two pins and connect them to the pins to achieve conductive interconnection with the microscale conductive structure.

[0017] Step 8: Using an in-situ high-temperature post-treatment process, the functional layer material is in-situ solidified and its conductivity is improved according to the sintering time and temperature to meet the conductivity requirements, thereby achieving the integrated manufacturing of curved conformal electronic circuits including dielectric layers, conductive layers, and functional layers;

[0018] Step 9: Connect the pins on both sides of the microscale conductive structure to external detection instruments to transmit the detection data of the surface functional layer of the curved electronic circuit in real time, thereby realizing the quantitative detection and data analysis statistics of the functional structure performance of the curved conformal electronic circuit.

[0019] The multi-material 3D printing platform in step 1 includes a three-axis XYZ mobile platform and an in-situ high-temperature heating plate. The FFF print head, coaxial print head and extrusion print head are fixedly mounted on the three-axis XYZ mobile platform by a fixture and can be freely switched through optimized design. The maximum printing volume of the platform is 300mm×300mm×200mm.

[0020] The dielectric layer material in step 2 is a consumable material suitable for FFF printing, such as polyetheretherketone (PEEK), polylactic acid (PLA), acrylonitrile-butadiene-styrene copolymer (ABS), polyetherimide (PEI), a polyetheretherketone composite material mixed with glass fiber, or a polyetheretherketone composite material mixed with carbon fiber; FFF printing process parameters include parameters such as print head size, receiving distance, printing speed, extrusion flow rate, and nozzle heating temperature; the dielectric layer structure manufactured by FFF is first designed with a plane / curved surface model using 3D modeling software, and then imported into slicing software to convert it into G code to realize the manufacture of plane and curved dielectric layer structures; the maximum size of the dielectric layer structure manufactured by FFF is 300mm×300mm×200mm.

[0021] The conductive materials in step 3 include micron-nano conductive gold paste / silver paste / copper paste / platinum paste, conductive polymers, carbon-based conductive paste, PEDOT:PSS conductive materials and various conductive mixture materials; the insulating materials are thermosetting, thermoplastic or photosensitive polyimide (PI) solution and other materials; the coaxial printing needle is a dispensing needle made of stainless steel or plastic, and the dimensions of the inner and outer needles are such that the two materials can be smoothly extruded after the two needles are assembled into a coaxial printing needle, thereby realizing a core-shell conductive structure with an encapsulation layer structure.

[0022] The five printing process modes of the coaxial printing needle in step 4 are achieved by respectively controlling the on and off of the extrusion air pressure of the inner and outer needles and the on and off of the voltage applied to the coaxial printing needle; the working conditions of the five printing process modes of the coaxial printing needle are as follows: Mode 1 is that the inner and outer needles simultaneously extrude and print a core-shell conductive structure with an encapsulation layer, and the working conditions are that the air pressure of the inner and outer needles is on and the voltage is off; Mode 2 is that the inner needle extrude and prints a pin, and the working conditions are that the air pressure of the inner needle is on, the air pressure of the outer needle is off, and the voltage is off; Mode 3 is that the outer needle extrude and prints a packaging structure, and the working conditions are that the air pressure of the inner needle is off, the air pressure of the outer needle is on, and the voltage is off; Mode 4 is that the inner and outer needles simultaneously print a microscale core-shell conductive structure after adding static electricity, and the working conditions are that the air pressure of the inner and outer needles is on and the voltage is on; Mode 5 is that the inner needle prints a microscale conductive structure after adding static electricity, and the working conditions are that the air pressure of the inner needle is on, the air pressure of the outer needle is off, and the voltage is on.

[0023] The coaxial printing needle process parameter control optimization in step 5 includes the extrusion flow rate of the inner and outer needles, the platform movement speed, the receiving distance from the needle to the substrate, the applied voltage, etc.; the coaxial needle printing process modes required for printing a microscale conductive structure with pins at both ends are mode 1, mode 2 and mode 4, and the switching order is mode 2, mode 1, mode 4, mode 1 and mode 2; switching from mode 2 to mode 1 requires turning on the outer needle air pressure at the end of the printed contact, and switching from mode 1 to mode 4 requires waiting for mode 1 to stably print the core-shell conductive structure with the encapsulation layer, then quickly turning on the voltage and increasing the printing speed to achieve the printing of the microscale core-shell conductive structure, switching from mode 4 back to mode 1 requires reducing the printing speed and turning off the power to print the core-shell conductive structure with the encapsulation layer, and switching from mode 1 back to mode 2 requires turning off the outer needle extrusion air pressure to achieve the printing of the pins.

[0024] In step 5, the process parameters for the inner needle extrusion printing of mode 2 are as follows: the inner needle extrusion pressure is 1000mbar-10000mbar, the platform movement speed is 1mm / s-50mm / s, and the receiving distance is 50μm-500μm; the process parameters for the coaxial extrusion printing of mode 1 are as follows: the inner needle extrusion pressure is 1000mbar-9000mbar, the outer needle extrusion pressure is 50mbar-500mbar, the platform movement speed is 1mm / s-100mm / s, and the receiving distance is 50μm -500μm; Mode 4 coaxial electrostatic printing process parameters are: inner needle extrusion pressure is 1000mbar-9000mbar, outer needle extrusion pressure is 50mbar-5000mbar, platform movement speed is 10mm / s-300mm / s, receiving distance is 200μm-3000μm; switching from Mode 1 to Mode 4 increases the printing needle receiving distance from 100μm to 3000μm; switching from Mode 4 to Mode 1 reduces the printing needle receiving distance from 500μm to 100μm.

[0025] The conductive structure of the core-shell conductive structure with the encapsulation layer in step 5 has a line width of 50 μm-1000 μm and a thickness of 10 μm-500 μm, and the encapsulation layer has a line width of 100 μm-2000 μm and a thickness of 10 μm-500 μm; the conductive structure of the microscale core-shell conductive structure has a line width of 10 μm-100 μm and a thickness of 1 μm-100 μm, and the encapsulation layer has a line width of 100 μm-3000 μm and a thickness of 10 μm-100 μm; the minimum pin area is 0.5 mm 2 -5mm 2 .

[0026] The high-temperature in-situ sintering process in step 6 has a sintering temperature of 145°C for the core-shell conductive structure with packaging structure, the microscale core-shell conductive structure and the pin, and the sintering time is at least 45 minutes; after the conductive structure and the packaging structure are sintered at high temperature, the packaging material and the dielectric layer form a tight and reliable connection, thereby improving the interface bonding strength.

[0027] The functional layer manufacturing process in step 7 is extrusion 3D printing, and the process parameters included are extrusion air pressure of 300mbar-3000mbar, platform movement speed of 1mm / s-10mm / s and receiving distance of 50μm-100μm; the functional layer structure size is designed and manufactured according to the function and requirements; the functional layer electronic devices include resistors of different resistance values ​​and sizes, temperature sensors, wind speed sensors, pressure sensors, strain and stress sensors, as well as functional devices such as capacitors and inductors; the functional layer materials are graphite-based resistor paste, carbon nanotube-based resistor paste, metal gold / silver / platinum-based resistor paste, carbon nanotube / graphene / MXene / graphite and other conductive materials and mixtures thereof; the pins at both ends of the functional structure and the microscale conductive structure are connected to achieve physical connection and electrical conduction.

[0028] The in-situ high-temperature post-treatment process of the functional layer in step 8 has a heating temperature and a heating time determined by the printing material and properties of the functional layer, with a heating temperature range of 100°C-150°C and a heating time range of 45-60 minutes. The functional layer can realize the monitoring and testing of the performance of three-dimensional heterogeneous functional structures.

[0029] The external detection instruments in step 9 include a DC power supply, a resistance tester and a voltmeter.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention proposes a coaxial needle multi-process real-time switching printing method for curved conformal electronic circuits, which can directly manufacture microscale core-shell conductive structures, pin contacts and functional layers on the rough curved surface substrate printed by FFF. The directly printed functional structure can determine its structural performance according to the selected material type and the designed size (length × width × height), and can directly avoid the easy detachment of manual solder joints of functional devices (such as commercial resistors and commercial sensors) and the impact on their performance stability. It is conducive to the efficient and rapid integrated manufacturing of functional components of curved conformal electronic circuits, and is of great help to their performance improvement and regulation.

[0032] The traditional manufacturing process requires machining the dielectric layer structure and screen-printing the conductive structure, and then connecting the conductive structure to the functional structure by manual welding. The process of the present invention has high integration and high manufacturing efficiency, and does not require any manual operation assistance. The interface between the functional layer electronic devices and the dielectric layer and the conductive layer is highly stable, and the performance of the functional layer can be controlled through the printing process, thereby realizing on-demand regulation of the functional structure performance of the entire curved conformal electronic circuit, and can realize the overall and efficient manufacturing of large-scale, complex curved surface structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the multi-process switching process of the coaxial needle in an embodiment of the present invention.

[0034] Figure 2 In an embodiment of the present invention, a coaxial needle prints a microscale core-shell conductive structure with conductive pins on a rough planar substrate surface printed by FFF through multi-process switching.

[0035] Figure 3 This is a microscale core-shell conductive structure with a conductive pin structure printed by a coaxial needle on the surface of a rough curved substrate printed by FFF through a multi-process switching technology in Example 1 of the present invention.

[0036] Figure 4 The integrated printed curved conformal electronic circuit functional component in Example 2 of the present invention includes a curved dielectric layer, a curved conformal microscale core-shell conductive structure and conductive pins, and a conformal functional structure (resistance) structure. DETAILED DESCRIPTION

[0037] The present invention is described in detail below with reference to the embodiments and accompanying drawings.

[0038] Example 1, with reference to Figure 1-Figure 3 A coaxial needle multi-process real-time switching printing method for curved surface conformal electronic circuits includes the following steps:

[0039] Step 1: The multi-material 3D printing platform is equipped with an FFF (fused filament fabrication) print head, a coaxial print head, and an extrusion print head to manufacture the dielectric layer, the conductive layer, and the functional layer respectively.

[0040] Step 1: In this embodiment, PEEK material is used as the dielectric layer material. The PEEK material is loaded into the FFF (fused filament fabrication) print head 1 and formed by high-temperature melt extrusion. The PEEK dielectric layer printing process is as follows: the platform movement speed is 25 mm / s, the distance from the needle to the substrate is 300 μm, the heating temperature is 405°C, and the needle diameter is 0.4 mm copper nozzle;

[0041] In this embodiment, a conductive material and an insulating material are loaded into a coaxial printing nozzle 2, and a coaxial needle is used to print a microscale core-shell conductive structure and a conductive pin on the surface of a PEEK dielectric layer. A 3ml syringe and a 10ml syringe are connected to the coaxial needle. The coaxial needle models are 20G (inner diameter 0.58mm) and 25G (inner diameter 0.25mm) stainless steel needles. The inner syringe is a highly conductive conductive silver paste, and the outer syringe is a polyimide solution. The printing process parameters are: internal and external air pressures of 1500mbar and 100mbar, respectively, a voltage of 1200V, a platform movement speed of 12.5mm / s, and a receiving distance from the needle to the substrate of 250μm.

[0042] In this embodiment, the functional material is loaded into the extrusion printing nozzle 3, and a plastic dispensing needle is used to extrude and print the graphite-based resistor paste. The dispensing needle is 25G (inner diameter 0.25mm). The printing process parameters are as follows: air pressure 2000mbar, platform movement speed 5mm / s, and receiving distance from the needle to the substrate is 100μm.

[0043] Step 2: This embodiment uses a coaxial needle multi-process switching printing method to achieve the integrated manufacturing of curved conformal electronic circuit structures, especially the integrated manufacturing of micro-scale conductive structures and conductive pins on the surface of the curved PEEK dielectric layer.

[0044] In this embodiment, the PEEK dielectric layer has a curved surface structure. First, a 3D model is designed using the 3D software Pro / E. Then, using the Cura slicing software, it is converted into G-code that can be recognized by the printer. The optimized process parameters are used to print the curved dielectric structure.

[0045] In this embodiment, the conductive structure and pins on the surface of the PEEK dielectric layer are integratedly manufactured through multi-process switching of a coaxial needle. First, the pin structure is extruded and printed by the inner needle of the coaxial needle. Then, when the pin structure is printed, the outer needle air pressure and voltage are turned on, and the coaxial electrostatic printing of the micro-scale conductive structure is switched. Finally, before the conductive structure is printed, the outer needle air pressure and voltage are turned off, and the inner needle extrusion printing of the pins is switched. The entire printing process realizes the integrated manufacturing of the micro-scale conductive structure on the surface of the PEEK dielectric layer and the pins at both ends by controlling the on-off of the air pressure and voltage of the inner and outer needles, and reserves the corresponding position for the printing of the functional layer.

[0046] Step 3: Place the printed PEEK dielectric layer + conductive structure in an oven and heat at 145°C for 45-60 minutes.

[0047] The beneficial effects of this embodiment are: the multi-process switching printing technology based on the coaxial needle is used to achieve the FFF rough surface ( Figure 2 ) / Surface( Figure 3) integrated printing of the microscale core-shell conductive structure on the surface of the structure and the conductive contact structure at its endpoints; compared with traditional manufacturing methods, this process is simple and efficient, and can achieve real-time switching of different processes during the printing process, and maintain the continuity and conductivity of the microscale core-shell conductive structure and the conductive pins without any manual processing.

[0048] Example 2, reference Figure 4 A coaxial needle multi-process real-time switching printing method for curved surface conformal electronic circuits includes the following steps:

[0049] Step 1: In this embodiment, an extrusion printing nozzle 3 is used to print the resistive functional layer. In step 2 of embodiment 1, pins for the functional structure and the conductive structure are reserved in advance. The functional layer is printed at the previously reserved pin positions by the extrusion printing nozzle 3, and the microscale conductive structure and the functional structure are physically connected and electrically conductive through the pins.

[0050] Step 2: In this embodiment, the printed functional layer structure is placed in an oven and heated at 180° C. for 60 minutes.

[0051] Beneficial effects of this embodiment: Based on Example 1, this embodiment realizes the printing of a curved conformal fixed-value resistor structure at the reserved conductive pin position. Compared with the traditional manual welding resistor structure, the directly printed and deposited conformal resistor structure has a strong interface bonding force, is not easy to fall off, and has good resistance / electrical stability.

Claims

1. A coaxial needle multi-process real-time switching printing method for curved surface conformal electronic circuits, characterized by: First, use FFF to print the rough curved surface substrate required by the target, then design the printing trajectory of the conductive structure and functional structure, and use the coaxial needle multi-process real-time switching printing technology to manufacture the microscale conductive structure and the pins of its two end points on the rough surface printed by FFF. Finally, use the extrusion printing process to print the functional layer structure at the pins to achieve physical connection and electrical conduction between the conductive structure and the functional structure.

2. The method according to claim 1, comprising the steps of: Step 1: The multi-material 3D printing platform is equipped with an FFF (fused filament fabrication) print head, a coaxial print head, and an extrusion print head to manufacture the dielectric layer, the conductive layer, and the functional layer respectively. Step 2: Select the dielectric layer material that meets the requirements and use the FFF printing nozzle to manufacture the flat / curved dielectric layer; Step 3: Select conductive and insulating materials as printing inks for micro-scale conductive structures, inject them into the printing syringes respectively, connect them to the coaxial printing needles to form a coaxial printing nozzle, and fix it to the multi-material 3D printing platform; Step 4: Use coaxial needle multi-process switching technology to print microscale conductive structures and pins on the surface of the FFF-printed dielectric layer. The coaxial printing needle has five printing modes: Mode 1 is the coaxial extrusion printing of a core-shell conductive structure with an encapsulation layer by the inner and outer needles; Mode 2 is the inner needle extrusion printing of pins; Mode 3 is the outer needle extrusion printing of the encapsulation structure; Mode 4 is the coaxial electrostatic printing of a microscale core-shell conductive structure by the inner and outer needles after electrostatic application; Mode 5 is the inner needle printing of a microscale conductive structure after electrostatic application; Step 5: By optimizing the printing process parameters, controlling the air pressure of the inner and outer needles, and switching the voltage during the printing process, the inner needle extrusion printing process is first used to manufacture the pins during the printing process. Before the pin printing is completed, the inner needle extrusion printing process is switched to the inner and outer needle coaxial printing process to manufacture the core-shell conductive structure with the encapsulation layer. After the core-shell conductive structure with the encapsulation layer is stably manufactured, the voltage is turned on to realize coaxial electrostatic printing of the microscale core-shell conductive structure. Before the printing of the microscale conductive structure is completed, the voltage is turned off, and the coaxial electrostatic printing process is switched to coaxial extrusion printing. After the printing is stable, the coaxial extrusion printing is switched to the inner needle extrusion printing process to manufacture the pins; repeat the above printing process to print a microscale core-shell conductive structure array with pin structures at both ends on the surface of the dielectric layer, so that it is connected and conductive with the functional layer structure; Step 6: Using an in-situ high-temperature sintering process, the microscale core-shell conductive structure and the pins are in-situ sintered and solidified according to the sintering temperature and sintering time; Step 7: Select the functional layer material according to the requirements. After extrusion printing process optimization and printing path planning, print the functional layer between the two pins and connect them to the pins to achieve conductive interconnection with the microscale conductive structure. Step 8: Using an in-situ high-temperature post-treatment process, the functional layer material is in-situ cured and its conductivity is improved, achieving the integrated manufacturing of curved conformal electronic circuits including dielectric layers, conductive layers, and functional layers; Step 9: Connect the pins on both sides of the microscale conductive structure to external detection instruments to transmit the detection data of the surface functional layer of its three-dimensional heterogeneous functional structure in real time, realizing the quantitative detection and data analysis statistics of the performance of the curved conformal electronic circuit structure.

3. The method according to claim 2, wherein: The multi-material 3D printing platform in step 1 includes a three-axis XYZ mobile platform and an in-situ high-temperature heating plate. The FFF printing nozzle, coaxial printing nozzle and extrusion printing nozzle are fixedly installed on the three-axis XYZ mobile platform by a clamp and can be freely switched through optimized design.

4. The method according to claim 2, wherein: The dielectric layer material in step 2 is polyetheretherketone (PEEK) material, polylactic acid (PLA) material, acrylonitrile-butadiene-styrene copolymer (ABS) material, polyetherimide (PEI) material, polyetheretherketone composite material mixed with glass fiber, or polyetheretherketone composite material mixed with carbon fiber; FFF printing process parameters include print head size, receiving distance, printing speed, extrusion flow rate, and nozzle heating temperature; the dielectric layer structure manufactured by FFF is first designed with a plane / curved surface model using 3D modeling software, imported into slicing software and converted into G code to realize the manufacture of plane and curved dielectric layer structures.

5. The method according to claim 2, wherein: The conductive materials in step 3 include micron-nano conductive gold paste / silver paste / copper paste / platinum paste, conductive polymers, carbon-based conductive paste, PEDOT:PSS conductive materials and various conductive mixture materials; the insulating material is a thermosetting, thermoplastic or photosensitive polyimide (PI) solution; the coaxial printing needle is a dispensing needle made of stainless steel or plastic, and the dimensions of the inner and outer needles are such that the two materials can be smoothly extruded after the two needles are assembled into a coaxial printing needle, thereby realizing a core-shell conductive structure with an encapsulation layer structure.

6. The method according to claim 2, wherein: The five printing process modes of the coaxial printing needle in step 4 are achieved by respectively controlling the on and off of the extrusion air pressure of the inner and outer needles and the on and off of the voltage applied to the coaxial printing needle; the working conditions of the five printing process modes of the coaxial printing needle are as follows: Mode 1 is that the inner and outer needles simultaneously extrude and print a core-shell conductive structure with an encapsulation layer, and the working conditions are that the air pressure of the inner and outer needles is on and the voltage is off; Mode 2 is that the inner needle extrude and prints a pin, and the working conditions are that the air pressure of the inner needle is on, the air pressure of the outer needle is off, and the voltage is off; Mode 3 is that the outer needle extrude and prints a packaging structure, and the working conditions are that the air pressure of the inner needle is off, the air pressure of the outer needle is on, and the voltage is off; Mode 4 is that the inner and outer needles simultaneously print a microscale core-shell conductive structure after adding static electricity, and the working conditions are that the air pressure of the inner and outer needles is on and the voltage is on; Mode 5 is that the inner needle prints a microscale conductive structure after adding static electricity, and the working conditions are that the air pressure of the inner needle is on, the air pressure of the outer needle is off, and the voltage is on.

7. The method according to claim 2, wherein: The coaxial printing needle process parameter control optimization in step 5 includes the extrusion flow rate of the inner and outer needles, the platform movement speed, the receiving distance from the needle to the substrate, and the applied voltage; The coaxial needle printing process modes required for printing microscale conductive structures with pins at both ends are mode 1, mode 2, and mode 4, and the switching order is mode 2, mode 1, mode 4, mode 1, and mode 2; To switch from mode 2 to mode 1, it is necessary to turn on the external needle air pressure at the end of the printed contact. To switch from mode 1 to mode 4, it is necessary to wait until mode 1 stably prints the core-shell conductive structure with the encapsulation layer, then quickly turn on the voltage and increase the printing speed to achieve the printing of the microscale core-shell conductive structure. To switch from mode 4 back to mode 1, it is necessary to reduce the printing speed and turn off the power to print the core-shell conductive structure with the encapsulation layer. To switch from mode 1 back to mode 2, it is necessary to turn off the external needle extrusion air pressure to achieve the printing of the pins.

8. The method according to claim 2, wherein: The high-temperature in-situ sintering process in step 6 has a sintering temperature of 145°C for the core-shell conductive structure with packaging structure, the microscale core-shell conductive structure and the pin, and the sintering time is at least 45 minutes; after the conductive structure and the packaging structure are sintered at high temperature, the packaging material and the dielectric layer form a tight and reliable connection, thereby improving the interface bonding strength.

9. The method according to claim 2, wherein: The functional layer manufacturing process in step 7 is extrusion 3D printing, and the functional layer structure size is designed and manufactured according to the function and requirements; the functional layer electronic devices include resistors of different resistance values ​​and sizes, temperature sensors, wind speed sensors, pressure sensors, strain and stress sensors, and functional devices of capacitors and inductors; the functional layer materials are graphite-based resistor paste, carbon nanotube-based resistor paste, metal gold / silver / platinum-based resistor paste, carbon nanotube / graphene / Mxene / graphite conductive materials and mixtures thereof; the functional structure is connected to the pins at both ends of the microscale conductive structure to achieve physical connection and electrical conduction.

10. The method according to claim 2, wherein: In the in-situ high-temperature post-treatment process of the functional layer in step 8, the heating temperature and heating time are determined by the printing material and properties of the functional layer, the heating temperature range is 100°C-150°C, and the heating time range is 45-60 minutes; The functional layer realizes the monitoring and testing of the performance of three-dimensional heterogeneous functional structures.

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