Breathable and stretchable circuit capable of being activated by imprinting, and preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of flexible electronics, and relates to a breathable and stretchable circuit capable of being activated by imprinting, and a preparation method therefor and a use thereof. The preparation method for the breathable and stretchable circuit capable of being activated by imprinting in the present invention comprises the following steps: dissolving a thermoplastic polymer in a solvent, adding liquid metal particles, and mixing and dispersing to obtain a mixed solution; carrying out electrospinning on the obtained mixed solution to prepare a nanofiber membrane; and using a stamping model having a circuit pattern to stamp the obtained nanofiber membrane so as to obtain the breathable and stretchable circuit capable of being activated by imprinting. The present invention ensures the breathability and the stretchability by using the nanofiber membrane. The liquid metal particles match fibers in diameter, and therefore, liquid metal in nanofibers can be overflowed by means of imprinting to form a conductive path, achieving high-precision preparation of circuits.

Description

A breathable and stretchable circuit that can be activated by printing, and its preparation method and application Technical Field

[0001] The present invention relates to the field of flexible electronic technology, and in particular to a breathable and stretchable circuit that can be activated by embossing, and a preparation method and application thereof. Background Art

[0002] Stretchable electronics and systems have attracted great interest due to their applications in wearable electronics, soft robotics, human-machine interfaces, and bioelectronic devices. A key aspect of stretchable electronics is the development of stretchable conductors. Many studies have focused on creating macroscopic deformable conductors by incorporating rigid conductors such as metal nanowires or conductive polymers into elastic substrates using methods such as bending, wrinkling design, or dispersion spraying. However, the inherent rigidity of conductive materials often compromises the stability of stretchable conductors during long-term deformation. Problems such as segregation of metal nanowires and cracking of conductive polymers under repeated external forces lead to irreversible degradation of the conductivity of stretchable conductors. In contrast, gallium-based liquid metals (LMs) have also attracted widespread attention due to their excellent deformability while having extremely high conductivity at room temperature.

[0003] To circumvent the challenges posed by the low viscosity and high surface tension of liquid metal and the spontaneous formation of a non-conductive Ga2O3 oxide layer, liquid metal-based filaments typically require complex fabrication processes such as sintering, transfer printing, or doping. These complexities limit the scalability and flexibility of stretchable electronic device designs. Furthermore, the elastic substrates commonly used for stretchable conductors are impermeable films with poor adhesion and compatibility with human skin. This makes them unsuitable for long-term applications such as healthcare monitoring and may even cause inflammatory or allergic health effects. Liquid metal-loaded nanofiber meshes have recently attracted attention because liquid metal can penetrate the interstices of nanofibers through coating or spraying, forming a grid-like conductive path during stretching. The resulting materials exhibit high conductivity and stretchability while maintaining good air permeability. However, existing studies typically rely on coating or spraying methods. Due to the high surface tension of liquid metal and its poor interfacial compatibility with polymer fiber networks, at the macroscopic level, the liquid metal and polymer network typically appear as two layers: a liquid metal conductive layer and a polymer support layer. The poor adhesion between these two layers can easily lead to liquid metal leakage, resulting in low circuit precision and difficulty achieving good cyclic stretching stability, which has become a problem in the industry. In other words, the shortcomings of current technologies are: 1. Existing stretchable circuits lack breathability; 2. Existing stretchable circuits have large circuit widths and low precision; 3. Activating the conductive pathways is difficult, making rapid fabrication difficult.

[0004] Therefore, how to make stable and precise conductive circuits and how to alleviate the serious interface problems between liquid metal and the substrate elastic network have become urgent issues to be solved.

[0005] Summary of the Invention

[0006] To address the above technical issues, the present invention provides a breathable and stretchable circuit that can be activated by imprinting, as well as a method for its preparation and application. This invention utilizes a nanofiber membrane to ensure both breathability and stretchability. Because the liquid metal particles match the fiber diameter, imprinting allows the liquid metal within the nanofibers to overflow and form a conductive path, enabling high-precision circuit fabrication.

[0007] The present invention is achieved through the following technical solutions:

[0008] The first object of the present invention is to provide a method for preparing a breathable and stretchable circuit that can be activated by embossing, comprising the following steps:

[0009] Dissolving a thermoplastic polymer in a solvent, adding liquid metal particles and mixing and dispersing the mixture to obtain a mixed liquid;

[0010] The obtained mixed solution is subjected to electrospinning to prepare a nanofiber membrane;

[0011] The obtained nanofiber membrane is stamped with a stamping mold with a circuit pattern to obtain a breathable and stretchable circuit that can be activated by stamping.

[0012] In one embodiment of the present invention, the thermoplastic polymer is selected from one or more of polyurethane, PVDF, PVDF-HFP, PVA, SBS and SEBS.

[0013] In one embodiment of the present invention, the solvent is selected from one or more of hexafluoroisopropanol, tetrahydrofuran, acetone, N,N-dimethylformamide, N,N-dimethylacetamide, water and dichloromethane.

[0014] In one embodiment of the present invention, the metal in the liquid metal particles is selected from one or more of gallium, gallium-indium alloy, gallium-indium-tin alloy and indium-tin-bismuth alloy.

[0015] In one embodiment of the present invention, the liquid metal particles are prepared by the following method:

[0016] The metal is placed in alcohol and ultrasonically treated to obtain the liquid metal particles.

[0017] In one embodiment of the present invention, the mass ratio of the liquid metal particles to the thermoplastic polymer in the thermoplastic polymer solution is 4-10:1.

[0018] In one embodiment of the present invention, the ratio of the particle size of the liquid metal particles to the diameter of the fibers in the nanofiber membrane is 1:0.35-2.

[0019] In one embodiment of the present invention, the electrospinning satisfies one or more of the following conditions:

[0020] Needle size is 20G-24G;

[0021] The applied voltage is 6kV-15kV;

[0022] The solution feeding rate was 0.5 mL h -1 -1.2 mL h -1 ;

[0023] The fiber collection distance is 8cm-16cm;

[0024] The speed of the metal roller collecting the fiber film is 120rpm-200rpm;

[0025] The humidity for electrospinning was 40%.

[0026] In one embodiment of the present invention, the punching condition is: the pressure on the contact surface of the nanofiber membrane is 100 kPa-1 MPa.

[0027] The second object of the present invention is to provide a breathable and stretchable circuit that can be embossed and activated and is prepared by the preparation method.

[0028] The third object of the present invention is to provide applications of the imprintable, breathable, stretchable circuit in wearable electronics, soft robots, human-machine interfaces, or bioelectronic devices.

[0029] The above technical solution of the present invention has the following advantages over the prior art:

[0030] The present invention provides a breathable stretchable circuit that uses imprinting technology and liquid metal nanofiber membrane (LMNM) to create flexible and personalized circuit designs. By adapting the liquid metal particles and electrospun fibers, the stretchable nanofiber membrane exhibits excellent properties under high liquid metal content loading, such as super elasticity (up to 400%) and moisture permeability (2941g m -2 d -1). Initially, the liquid metal particles are in a semi-embedded and unconnected state in the polymer nanofibers, at which point the stretchable nanofiber membrane is electrically insulating. The stamping process causes the external liquid metal particles to break and penetrate the nanonetwork gaps, thereby forming a conductive area within the stretchable nanofiber membrane. The liquid metal particles inside the fibers become fixed anchor points, while the overflowing liquid metal is tightly bonded to the nanofibers on the same plane, which greatly improves the interfacial compatibility between the liquid metal and the polymer fibers. This process facilitates the post-production of patterned circuits and provides greater flexibility for personalized circuit design. After these circuits are integrated with various electronic components, they can realize a variety of functions, such as outputting square wave signals, lighting circuits, and wireless charging. In addition, the manufactured flexible electronic components have high precision, a minimum line width of 50 microns, good cycle stability, and can be recycled more than 30,000 times. Its excellent biocompatibility and permeability make it suitable for collecting bioelectric signals such as electrocardiogram (ECG) and electromyogram (EMG), and it has broad application prospects in the field of flexible electronics. The technology is also considered environmentally friendly, as both the polymer components and the liquid metal particles can be easily separated and recycled after use. Furthermore, experiments were conducted on various commonly used polymers for preparing stretchable nanofiber membranes, demonstrating the technology's potential for flexible electronics. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein

[0032] FIG1 is a schematic diagram of the preparation process of the breathable and stretchable circuit that can be activated by embossing according to the present invention;

[0033] FIG2 is a circuit diagram of Example 1 of the present invention;

[0034] FIG3 is a schematic diagram of a stretchable light-emitting circuit in Example 1 of the present invention;

[0035] FIG4 is a diagram showing the diameter distribution of liquid metal particles of different sizes in a test example of the present invention;

[0036] FIG5 shows the resistance and conductivity of the nanofiber membrane containing liquid metal particles of different particle sizes after stamping in the test example of the present invention;

[0037] FIG6 is a graph showing fiber diameters corresponding to different liquid metal contents in a test example of the present invention;

[0038] FIG7 is a stress-strain curve of a circuit under different liquid metal loadings in a test example of the present invention;

[0039] FIG8 is a strain-impedance curve of the circuit under different liquid metal loading amounts in a test example of the present invention;

[0040] FIG9 is a diagram showing the impedance stability of a circuit under cyclic stretching in a test example of the present invention;

[0041] FIG10 is a diagram showing the air permeability of a circuit under different pressure differences in a test example of the present invention;

[0042] FIG11 is a scanning electron microscope photograph of conductive lines of different widths (50 μm, 100 μm, 500 μm, and 1 mm) in a test example of the present invention;

[0043] FIG12 is a template used for imprinting in a test example of the present invention and a circuit prepared after imprinting;

[0044] FIG13 is a test diagram of the conductivity of the nanofiber membrane circuit in the test example of the present invention. DETAILED DESCRIPTION

[0045] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0046] Example 1

[0047] This embodiment provides a method for preparing a breathable and stretchable circuit that can be activated by embossing, and the specific steps are as follows:

[0048] (1) Preparation of composite spinning solution

[0049] A polymer solution was prepared by dissolving 1g of thermoplastic polyurethane in 19g of hexafluoroisopropanol and stirring at room temperature for 12 hours. Liquid metal particles were prepared by sonicating 1g of EGaIn eutectic alloy in 5g of anhydrous ethanol in a 10mL centrifuge tube. Ultrasonication was performed in an ultrasonic cell disruptor at 50% power for 5 minutes, with the centrifuge tube placed in an ice-water bath. The resulting liquid metal slurry was centrifuged at 100 rpm for 60 seconds; the supernatant was retained and then centrifuged again at 500 rpm for 90 seconds before removal. The remaining slurry was vacuum-dried at room temperature for 6 hours. The liquid metal particles were then added to the polymer solution in a specific mass ratio (liquid metal particle mass: polymer solution mass = 8:1) and stirred at room temperature for two hours to ensure uniform dispersion of the particles.

[0050] (2) Preparation of nanofiber membranes by electrospinning

[0051] The mixed solution containing polymer solution and liquid metal particles was loaded into a 10 mL syringe and electrospun using an electrospinning machine. During the electrospinning process, the needle size, applied voltage, solution feeding speed, and fiber collection distance were set to 23 G, 12 kV, 1 mL h, and 1 s, respectively. -1The fiber membrane was collected by a metal roller at 110 rpm. The entire 110 rpm process was performed at room temperature with humidity controlled at 40%. The syringe was rotated every 2 hours to prevent settling of the liquid metal particles in the solution. Finally, the electrospun fiber membrane was placed in a 40°C oven for 6 hours to remove any residual solvent.

[0052] (3) Activating the conductive network by pressure stamping

[0053] Using a stamping mold with the desired circuit pattern, a pressure of 500 kPa was applied to the nanofiber membrane to stamp out a stretchable circuit board with a patterned circuit; the liquid metal loading of the resulting stretchable circuit board was 40 wt%, and the ratio of the particle size of the liquid metal particles in the nanofiber membrane to the diameter of the fiber was 1:0.5-2.

[0054] Example 2

[0055] This embodiment provides a method for preparing a breathable and stretchable circuit that can be activated by embossing, and the specific steps are as follows:

[0056] (1) Preparation of composite spinning solution

[0057] A polymer solution was prepared by dissolving 1g of PVDF-HFP in 9g of DMF and stirring at room temperature for 12 hours. Liquid metal particles were prepared by sonicating 1g of EGaIn eutectic alloy in 5g of anhydrous ethanol in a 10mL centrifuge tube. Ultrasonication was performed in an ultrasonic cell disruptor at 50% power for 5 minutes, with the tube kept in an ice-water bath. The resulting liquid metal slurry was centrifuged at 100 rpm for 60 seconds; the supernatant was retained and then centrifuged again at 500 rpm for 90 seconds before removal. The remaining slurry was vacuum-dried at room temperature for 6 hours. The liquid metal particles were then added to the polymer solution at a specific mass ratio (liquid metal particle mass: polymer solution mass = 3:1) and stirred at room temperature for two hours to ensure uniform dispersion of the particles.

[0058] (2) Preparation of nanofiber membranes by electrospinning

[0059] The mixed solution containing polymer solution and liquid metal particles was loaded into a 10 mL syringe and electrospun using an electrospinning machine. During the electrospinning process, the needle size, applied voltage, solution feeding speed, and fiber collection distance were set to 22 G, 14 kV, 1 mL h, and 1 s, respectively. -1The electrospun membrane was collected by a metal roller at 110 rpm. The entire 110 rpm process was performed at room temperature with humidity controlled at 40%. The syringe was rotated every 2 hours to prevent settling of the liquid metal particles in the solution. Finally, the electrospun membrane was placed in a 40°C oven for 6 hours to remove any residual solvent.

[0060] (3) Activating the conductive network by pressure stamping

[0061] Using a stamping mold with the desired circuit pattern, a pressure of 300kPa was applied to the nanofiber membrane to stamp out a stretchable circuit board with a patterned circuit; the liquid metal loading of the obtained stretchable circuit board was 30wt%, and the ratio of the particle size of the liquid metal particles in the nanofiber membrane to the diameter of the fiber was 1:0.35-1.5.

[0062] Test Case

[0063] (1) The liquid metal slurry obtained by the ultrasonic cell disruption system can be separated into liquid metal particles of different sizes by centrifugation at different speeds and vacuum drying at room temperature; the average particle sizes obtained by Gaussian fitting are 0.36 μm, 0.99 μm, and 3.95 μm, respectively. Nanofiber membranes with different liquid metal particle sizes were prepared by the method of Example 1.

[0064] Nanofiber membranes containing liquid metal particles of varying sizes were tested for resistance and conductivity after stamping. The results are shown in Figure 5. Nanofiber membrane a, containing liquid metal particles with an average particle size of 0.99 μm (Example 1), can be activated by stamping. Nanofiber membrane b, containing liquid metal particles with a size of 0.36 μm, does not match the nanofiber size and cannot be activated by stamping. Liquid metal particles with an average particle size of 3.95 μm are too large to be stably coated by the fibers, resulting in misconductivity even before stamping, and were therefore not used.

[0065] (2) Nanofiber membranes with different liquid metal loadings (20 wt%, 30 wt%, 40 wt%, and 50 wt%) were prepared using the method of Example 1. After stamping, stretchable circuit boards with patterned circuits were obtained. The diameters of the nanofibers within the nanofiber membranes were measured, and the results are shown in Figure 6. As can be seen from Figure 6, the liquid metal loading has little effect on the nanofiber diameter.

[0066] The mechanical properties of 50 mm × 10 mm strip samples were evaluated using an Instron tensile tester, as shown in Figure 7. Figure 7 confirms that the circuits with different liquid metal loadings are stretchable overall, with lower metal loadings resulting in greater stretchability.

[0067] The imprintable, breathable, and stretchable circuits with different liquid metal loadings (20 wt%, 30 wt%, 40 wt%, and 50 wt%) were measured using a Keithley DMM6500 connected to a computer to measure the change in sample resistance during stretching. The four-terminal method was used to accurately measure the resistance change of the sample and avoid interference. The results are shown in Figure 8. It can be seen from Figure 8 that the higher the metal loading, the higher the circuit conductivity. The stretchable circuit with a metal loading of 40 wt% was cyclically stretched, and the results are shown in Figure 9. Figure 9 confirms that the impedance stability of the circuit under cyclic stretching with a metal loading of 40 wt% is high.

[0068] (3) The moisture permeability of the sample was determined by the water method according to the ASTM E96 / E96M-2012 textile standard. The test was carried out at 32°C and 50% relative humidity for 24 hours. A sample with a liquid metal loading of 40wt% was sealed on the mouth of a cup filled with water and then placed in a test environment. The weight loss of water during this period was measured to determine the mass of water vapor that seeped out. According to the ASTM D737-75 standard test method, the permeability was measured at different pressure drops using a fully automatic permeability instrument (YG461G, Ningbo Yamato Instrument Co., Ltd., China). The output air flow rate (unit: mm / s) represents the permeability of the sample, and the results are shown in Figure 10. It can be seen from Figure 10 that the stretchable circuit prepared by the present invention has moisture permeability and breathability as a whole.

[0069] (4) According to the method of Example 1, imprintable, breathable, and stretchable circuits with different conductive line widths (50 μm, 100 μm, 500 μm, and 1000 μm) were prepared. The conductive line width was characterized by scanning electron microscopy (Regulus 8230) as shown in Figure 11. Figure 11 confirms that the minimum line width of the circuit is highly accurate.

[0070] (5) Circuit design was performed using Altium Designer software, and the corresponding 3D model was produced using SolidWorks software. A stamping mold with the desired pattern was produced using a 3D printer (Zortrax Inkspire), and then a pneumatic press (LNA001-63) was used to stamp the nanofiber membrane prepared in Example 1. The results are shown in FIG12 , confirming that different circuits can be prepared using the stamping technique.

[0071] (6) A constant voltage power supply was used to power the nanofiber membrane prepared in Example 2, and the on / off of the light-emitting diode was used as a test of the circuit conductivity. The results are shown in FIG13 , which confirms that the imprinting technology can realize the transformation of the nanofiber membrane from non-conducting to conducting circuit.

[0072] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a breathable and stretchable circuit that can be activated by embossing, characterized in that: The following steps are involved: The thermoplastic polymer is dissolved in a solvent, and liquid metal particles are added and mixed and dispersed to obtain a mixed liquid; The obtained mixed solution is subjected to electrostatic spinning to prepare a nanofiber membrane; The obtained nanofiber membrane is stamped with a stamping mold with a circuit pattern to obtain a breathable and stretchable circuit that can be activated by stamping.

2. The preparation method according to claim 1, characterized in that: The thermoplastic polymer is selected from one or more of polyurethane, PVDF, PVDF-HFP, PVA, SBS and SEBS.

3. The preparation method according to claim 1, characterized in that: The solvent is selected from one or more of hexafluoroisopropanol, tetrahydrofuran, acetone, N,N-dimethylformamide, N,N-dimethylacetamide, water and dichloromethane.

4. The preparation method according to claim 1, characterized in that: The metal in the liquid metal particles is selected from one or more of gallium, gallium-indium alloy, gallium-indium-tin alloy and indium-tin-bismuth alloy.

5. The preparation method according to claim 1, characterized in that: The mass ratio of the liquid metal particles to the thermoplastic polymer in the thermoplastic polymer solution is 4-10:

1.

6. The preparation method according to claim 1, characterized in that: The ratio of the particle size of the liquid metal particles in the nanofiber membrane to the diameter of the fiber is 1:0.35-2.

7. The preparation method according to claim 1, characterized in that: The electrospinning satisfies one or more of the following conditions: The needle size is 20G-24G; The applied voltage is 6kV-15kV; The solution feed rate was 0.5 mL / h -1 -1.2mLh -1 ; The fiber collection distance is 8cm-16cm; The rotation speed of the metal roller collecting the fiber membrane is 120rpm-200rpm.

8. The preparation method according to claim 1, characterized in that: The punching conditions are as follows: the pressure on the contact surface of the nanofiber membrane is 100 kPa-1 MPa.

9. A breathable and stretchable circuit that can be embossed and activated, prepared according to the preparation method according to any one of claims 1 to 8.

10. Application of the imprint-activated breathable stretchable circuit according to claim 9 in wearable electronic products, soft robots, human-machine interfaces or bioelectronic devices.

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