Stretchable wire preparation method based on laser in-situ activated liquid metal composite material

Abstract

The invention relates to the technical field of flexible materials, in particular to a preparation method of a stretchable wire based on a laser in-situ activated liquid metal composite material. According to the method, firstly, liquid metal is subjected to ultrasonic treatment to obtain liquid metal particles, then the liquid metal particles are fully mixed with a solution of an elastic polymer SEBS to prepare printing ink, then a stretchable wire pattern is prepared by means of the printing ink in combination with laser cutting and laser in-situ activation technologies, and finally, the stretchable wire is prepared through transferring and packaging. According to the method, two self-healing materials, namely liquid metal and SEBS, are utilized to form the composite material, and a technology for activating the liquid metal composite material in situ through laser scanning is provided, so that the defects in the prior art are overcome, and the requirements of flexible electronic devices on stretchable wires are met.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible materials, and in particular to a method for preparing a stretchable conductor based on laser in-situ activation of a liquid metal composite material. Background Art

[0002] Flexible electronic devices have shown broad application prospects in fields such as personalized medicine. At present, most flexible electronic devices rely on wires to transmit signals. However, traditional wire materials are solid metals that can only be bent and lack stretchability, which limits the application scenarios of flexible electronic devices in the human body. Therefore, how to achieve the stretchability of wires in flexible electronic devices has become one of the major challenges currently facing this field.

[0003] Liquid metal (LM, here refers to gallium-indium liquid alloy) is liquid at room temperature. It has both the deformable and reconfigurable fluid properties of liquid and the high electrical and thermal conductivity of metal. Its good plasticity and conductivity make it suitable for the preparation of flexible electronic devices. Gallium-based liquid metal has certain biocompatibility and is suitable as a material for wearable flexible circuits and flexible wires. However, due to the presence of a surface oxide layer, liquid metal has high surface tension and is difficult to pattern using traditional printing or printing methods. It is usually injected into a microfluidic channel or ultrasonically dispersed into particles and then assembled on a flexible substrate to achieve patterning. However, these methods are complicated and costly to operate. Due to differences in personal operating levels, the wire patterning effect is unstable. In addition, the liquid metal particles assembled on the flexible substrate are usually not conductive and require laser selective sintering activation. There are problems such as the activated liquid metal being easily overflowed by external forces and breaking the external pattern, and the remaining liquid metal particles affecting the wire performance. Therefore, it is urgent to solve this problem.

[0004] The above contents are only used to assist in understanding the technical solution of the present invention, and do not constitute an admission that the above contents are the closest prior art. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing stretchable wires based on laser in-situ activation of liquid metal composite materials. The method utilizes liquid metal and SEBS, two self-healing materials, to form a composite material, and proposes a technology for in-situ activation of liquid metal composite materials by laser scanning, which not only overcomes the shortcomings of the prior art, but also meets the needs of flexible electronic devices for stretchable wires.

[0006] To achieve the above object, the technical solution of the present invention is implemented as follows: a method for preparing a stretchable wire based on laser in-situ activation of a liquid metal composite material; the preparation method comprises the following steps:

[0007] S1. Preparation of liquid metal:

[0008] The molten gallium and indium are mixed according to a mass ratio and heated in an oil bath to obtain liquid metal LM.

[0009] Compared with gallium, which has a melting point of 29.76°C, gallium-indium liquid alloy has a lower melting point (15.5°C) and can be liquid at room temperature.

[0010] S2. Preparation of liquid metal particles:

[0011] S21, placing liquid metal (LM) into a surfactant solution diluted with anhydrous ethanol, and performing water bath ultrasound to obtain a LM particle suspension;

[0012] S22, after standing, take out the upper LM particle suspension, centrifuge and pour out the liquid, add anhydrous ethanol to wash away the excess surfactant, centrifuge and wash several times to obtain solid LM particles;

[0013] S3. Preparation of SEBS solution:

[0014] SEBS and an organic solvent are mixed according to a mass ratio and then ultrasonicated in a water bath until SEBS is completely dissolved to obtain a SEBS solution;

[0015] Preparation of S4 and LM ink:

[0016] The LM particles and the SEBS solution are mixed in proportion, shaken first and then magnetically stirred to obtain the LM ink;

[0017] Magnetic stirring not only saves manpower but also ensures that LM particles and SEBS solution are fully mixed.

[0018] S5. Patterning of LM ink:

[0019] S51. Apply LM ink on a polytetrafluoroethylene substrate, and transfer the ink and substrate to a glass sheet after the solvent evaporates completely.

[0020] Scraping film formation can ensure uniform and adjustable film thickness. After the organic solvent is completely volatilized, the LM ink is a solid film. Compared with assembling LM particles on the elastomer polymer, the LM particles only exist on the surface of the elastomer. The LM particles in the ink are evenly distributed in the SEBS elastomer. After activation, SEBS can encapsulate LM, improve stretchability and prevent LM leakage.

[0021] S52, cutting a conductor pattern on the LM ink by laser.

[0022] Compared with the patterning of liquid metal by photolithography microfluidic channels, the method of patterning by laser cutting LM ink is simple to operate, low cost and has a short patterning process. Compared with the patterning of liquid metal ink by flexible printer, which is easy to block the needle and the patterning effect is greatly affected by personal operation, the method of patterning by laser cutting LM ink has high pattern accuracy and stable effect. After laser cutting is patterned, excess ink can be removed, thereby avoiding the influence of excess liquid metal on the electrical properties or radio frequency properties of the pattern.

[0023] S6, In-situ activation of LM ink:

[0024] The ink is activated in situ by laser scanning, and the conductor pattern is transformed from non-conductive to conductive.

[0025] Laser scanning evaporates the oxide layer on the surface of the LM particles, so that the LM particles in the ink are activated in situ and gathered together to form a conductive network, and the ink is conductive. Compared with mechanical activation, the laser scanning activation method can precisely control the power and area and can completely cover the pattern. After activation, the conductivity is high and the activation effect is stable and is not affected by personal operation level.

[0026] S7. Transfer and packaging of wires:

[0027] The wire pattern was transferred onto the SEBS substrate film and encapsulated with a layer of SEBS film to obtain a stretchable wire based on liquid metal ink.

[0028] Compared with PDMS, the most commonly used elastomeric polymer in flexible electronic devices, SEBS has better stretchability (the elongation at break can reach 1000%) and good self-healing properties. The encapsulation is achieved through the self-healing properties of SEBS, and the bond between the encapsulation and the substrate is strong, which effectively protects the wire pattern and improves its durability.

[0029] Preferably, in step S1, the mass ratio of gallium to indium is 75.5:24.5; the oil bath heating time is 3 hours; the oil bath heating condition is to perform oil bath heating on a hot plate at 85°C, turn on magnetic stirring while heating, the speed is 600-800r / min, and nitrogen needs to be continuously introduced during heating.

[0030] Preferably, in step S21, the liquid metal is a gallium-indium alloy, and the added volume of the liquid metal is 0.5 mL; the surfactant is ethyl 3-mercaptopropionate, the added volume of the surfactant solution is 15 mL, and the concentration of the surfactant solution is 0.1 mM / L, and the water bath ultrasound time is 30 min (the power of the water bath ultrasound is 30%, working for 3 s, and resting for 2 s).

[0031] Preferably, in step S22, the solution of the LM particle suspension is 30 mL; the washing amount of anhydrous ethanol added is 25-30 mL; the centrifugal speed of the centrifugal washing is 5000 r / min, the centrifugal time of the centrifugal washing is 15 min, and the number of washing times of the centrifugal washing is 2-3 times; the particle size of the prepared LM particles is 0.8-1.2 μm.

[0032] Preferably, in step S3, the organic solvent is a mixed solution of toluene and n-hexane; the mass ratio of SEBS particles to organic solvent in the SEBS solution is SEBS: n-hexane: toluene = 1:1:4; and the duration of the water bath ultrasonic mixing is 3-6 hours.

[0033] Preferably, in step S4, the mass ratio of the LM particles to the SEBS solution is 7:1-8:1; the shaking time is 1-3 min, the magnetic stirring time is 30-60 min, and the speed of the magnetic stirring is 600 r / min.

[0034] Preferably, in step S51, the coating is performed using an adjustable film-scraping applicator, and the height of the scraper is 500 μm; the volume of the LM ink is 3-5 mL; the glass sheet is 14 cm long, 7 cm wide, and 2 mm thick; and the solvent completely evaporates in more than 12 hours.

[0035] Preferably, in step S52, the laser is an ultraviolet laser; the cutting parameters are a rate of 500-1000 mm / s, a power of 50-70%, a frequency of 40-60 kHz, and a number of laser cutting circles of 10.

[0036] Preferably, in step S6, the laser scanning range should completely include the conductor pattern, and the parameters of the laser in-situ activation are a rate of 500-1000 mm / s, a power of 40-60%, a frequency of 40-60 kHz, and a laser scanning circle of 1.

[0037] Preferably, in step S7, the SEBS base film is prepared by spin coating of a SEBS solution, the components of the SEBS solution are SEBS: n-hexane: toluene = 1:1:2 in a weight ratio, and the spin coating speed during the spin coating preparation is 300-500r / min, and the transfer is performed in a semi-cured state after 10-15min; the SEBS film for encapsulation is obtained by spin coating a SEBS solution with a composition of SEBS: n-hexane: toluene = 1:1:3 or 1:1:2 on a silicon wafer and then volatilizing it, and the volatilization time is more than 12h.

[0038] The beneficial effects of the present invention are embodied in:

[0039] (1) The method provided by the present invention prepares the stretchable conductor by mixing liquid metal particles and SEBS solution to prepare ink, scraping, laser cutting and laser activating the ink, and the operation process is relatively simple. Scraping can make the ink evenly coated, and laser cutting the ink can accurately achieve patterning, which improves the preparation accuracy and ensures good patterning effect, avoiding the unstable patterning effect caused by differences in operation levels in photolithography microfluidic channels and flexible electronic printing.

[0040] (2) The method provided by the present invention uses a laser to activate the liquid metal ink in situ, which is simple to operate and greatly ensures the success rate of activation. The SEBS in the ink also encapsulates the liquid metal after in situ activation, protecting the integrity of the pattern. Compared with the laser selective activation of the liquid metal conductive layer, the present invention effectively avoids the problem that the activated liquid metal is easily overflowed by external force, thereby destroying the pattern, and the liquid metal particles left after activation have a negative impact on the electrical properties.

[0041] (3) The method provided by the present invention utilizes the synergistic effect of liquid metal and SEBS dual self-healing materials to make the activated wire pattern show good stretchability and conductivity, and the resistance remains stable under strain up to 100%, which can well adapt to different deformation requirements. In addition, the good self-healing ability of SEBS makes the pattern easy to transfer and encapsulate, and has excellent durability after encapsulation.

[0042] (4) The method provided by the present invention can also be applied to the preparation of flexible radio frequency devices and has great application potential in the field of flexible electronics. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic flow chart of the patterning method and activation method of the liquid metal ink in the present invention;

[0044] Figure 2 is a scanning electron microscope image of the liquid metal ink before activation in the present invention;

[0045] Figure 3 is a scanning electron microscope image of the liquid metal ink after laser scanning activation in the present invention;

[0046] Figure 4 It is the square resistance diagram of the liquid metal ink after being activated by laser scanning at different powers in the present invention;

[0047] Figure 5 This is a graph showing the change in resistance of the activated liquid metal ink in the present invention as a result of continuous 100% stretching;

[0048] Figure 6 This is a graph showing changes in S11 of the coil prepared with liquid metal ink in the present invention under different degrees of stretching. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0050] like Figure 1-6 As shown:

[0051] The present invention provides a method for preparing a stretchable conductor based on laser in-situ activation of a liquid metal composite material. The principle of the method provided by the present invention is: firstly, the liquid metal is ultrasonically treated to obtain liquid metal particles, and then the liquid metal particles are fully mixed with a solution of an elastic polymer SEBS to prepare ink, and then the ink is used in combination with laser cutting and laser in-situ activation technology to prepare a stretchable conductor pattern, and finally the stretchable conductor is transferred and packaged to achieve the preparation of the stretchable conductor. The mass ratio between the liquid metal particles and the SEBS solution is one or more of 7:6, 5:4, and 4:3. The mixing method of the liquid metal particles and the SEBS solution is selected from one or more of water bath ultrasound, oscillation, and magnetic stirring. The laser frequency is selected from one or more of 40kHz, 50kHz, and 60kHz. The laser scanning activation power is selected from one or more of 40%, 50%, and 60%.

[0052] Example 1

[0053] This example adopts the above method, and heats 100g of gallium and 32.5g of indium in an oil bath at 85°C, continuously introducing nitrogen during heating, and heating for 3h to obtain gallium-indium liquid metal. 0.5mL of LM is added to 15mL of 0.1mM / L ethanol solution of ethyl 3-mercaptopropionate, and ultrasonicated at 30% power for 30min to obtain LM particle suspension.

[0054] 30 mL of LM particle suspension was centrifuged at a centrifugal speed of 5000 r / s for 15 min to obtain LM particle precipitate. The LM particle precipitate was mixed with 30 mL of anhydrous ethanol by shaking and then allowed to stand for 5 min. The upper layer solution was centrifuged and washed 3 times to obtain LM particles.

[0055] 5 g of SEBS particles, 5 g of n-hexane and 20 g of toluene solution were mixed and ultrasonicated in a water bath for 6 h until the SEBS particles were completely dissolved to obtain a SEBS solution.

[0056] 3.5 g of LM particles were mixed with 3 g of SEBS solution, and the mixture was shaken for 3 minutes and then magnetically stirred for more than 30 minutes to obtain LM ink. The LM ink was scraped onto a polytetrafluoroethylene substrate with a scraping coater to a thickness of 500 μm, and the mixture was placed in a fume hood for more than 12 hours to wait for the organic solvent to evaporate.

[0057] The volatilized ink was transferred to a glass sheet together with a polytetrafluoroethylene substrate, and 10 circles of the volatilized LM ink were cut with an ultraviolet laser at a speed of 500 mm / s, a power of 60% and a frequency of 50 kHz. The excess part was torn off with tweezers to obtain a conductor pattern.

[0058] A UV laser is used to scan a circle of the conductor pattern at a speed of 500 mm / s, 40% power and a frequency of 50 kHz. The liquid metal particles in the ink are activated in situ, and the pattern changes from non-conductive to conductive.

[0059] Spin coat the SEBS solution on the silicon wafer at a speed of 500r / min, put the silicon wafer into a fume hood and wait for 10 minutes, the toluene in the SEBS solution will partially evaporate, and the SEBS base film will be semi-cured. Paste the conductor pattern together with the polytetrafluoroethylene substrate with the pattern facing down on the semi-cured SEBS base film, put it into a fume hood and wait for 12 hours until the SEBS substrate is completely cured, tear off the polytetrafluoroethylene, and the transfer is completed.

[0060] The SEBS solution was spin-coated at a speed of 500 r / min, and the product was placed in a fume hood and waited for 12 hours to obtain a SEBS film. The SEBS film was cut to a suitable size before pasting it on the transferred wire pattern, and the packaging was completed to obtain a stretchable wire based on liquid metal ink.

[0061] Example 2

[0062] This example adopts the above method, and heats 100g of gallium and 32.5g of indium in an oil bath at 85°C, continuously introducing nitrogen during heating, and heating for 3h to obtain gallium-indium liquid metal. 0.5mL of LM is added to 15mL of 0.1mM / L ethyl 3-mercaptopropionate ethanol solution, and ultrasonicated at 30% power for 30min to obtain LM particle suspension.

[0063] 30 mL of LM particle suspension was centrifuged at a centrifugal speed of 5000 r / s for 15 min to obtain LM particle precipitate. The LM particle precipitate was mixed with 30 mL of anhydrous ethanol by shaking and then allowed to stand for 5 min. The upper layer solution was centrifuged and washed 3 times to obtain LM particles.

[0064] 5 g of SEBS particles, 5 g of n-hexane and 20 g of toluene solution were mixed and ultrasonicated in a water bath for 6 h until the SEBS particles were completely dissolved to obtain a SEBS solution.

[0065] 4 g of LM particles were mixed with 3 g of SEBS solution, and the mixture was shaken for 10 minutes and then subjected to water bath ultrasound for more than 30 minutes to obtain LM ink. The LM ink was scraped onto a polytetrafluoroethylene substrate using a scraper coater with a coating thickness of 500 μm, and the mixture was placed in a fume hood for more than 12 hours to wait for the organic solvent to evaporate.

[0066] The volatilized ink was transferred to a glass sheet together with a polytetrafluoroethylene substrate, and 10 circles of the volatilized LM ink were cut with an ultraviolet laser at a speed of 500 mm / s, a power of 60% and a frequency of 50 kHz. The excess part was torn off with tweezers to obtain a conductor pattern.

[0067] SEBS substrate film was prepared by spin coating SEBS solution on silicon wafer at a speed of 500r / min. The silicon wafer was placed in a fume hood and waited for 10 minutes. The toluene in the SEBS solution was partially volatilized and the SEBS substrate film was semi-cured. The conductor pattern together with the polytetrafluoroethylene substrate was pasted on the semi-cured SEBS substrate film with the pattern facing down. The SEBS substrate was placed in a fume hood and waited for 12 hours until the SEBS substrate was completely cured. The polytetrafluoroethylene was torn off and the transfer was completed.

[0068] A UV laser is used to scan a circle of the conductor pattern at a speed of 500 mm / s, 60% power and 60 kHz frequency. The liquid metal particles in the ink are activated in situ, and the pattern changes from non-conductive to conductive.

[0069] The SEBS solution was spin-coated on the transferred conductor pattern at a speed of 500 r / min, and the pattern was placed in a fume hood and waited for 12 hours for the toluene to completely evaporate. The packaging was completed and a stretchable conductor based on liquid metal ink was obtained.

[0070] It should be noted that the two packaging methods are differentiated according to the different practical applications of the present invention; if the present invention is applied to the preparation of flexible wires, since the wires need to leave interfaces for the connection of electronic components, the packaging method of Example 1 is adopted, and the SEBS film is pasted for packaging through the self-healing property of the SEBS substrate. The SEBS film used for packaging can be cut to a suitable size by laser cutting before pasting and leave interfaces for the subsequent connection of electronic components; if the present invention is applied to the preparation of flexible passive RF devices, the packaging method of Example 2 is adopted, and the SEBS solution is spin-coated on the pattern for packaging, and the packaging is completed after the organic solvent in the solution is completely volatilized. The packaging method of Example 2 can achieve complete packaging and can better protect the device.

[0071] like Figure 1Compared with the method of realizing liquid metal patterning by photolithography microfluidic channel or ultrasonic dispersion into particles and then assembling them on a flexible substrate, the present invention has a simple operation process, low cost and less time consumption, and the whole process can be completed within 24 hours. Compared with the method of realizing liquid metal ink patterning by flexible electronic printing, the present invention is less affected by personal operation level and has a stable pattern forming effect. After patterning by laser cutting, the present invention activates the liquid metal in the ink in situ by laser scanning. Since excess ink is removed after patterning by laser cutting, there is no problem of residual liquid metal particles existing in the laser selective sintering activation of liquid metal particles assembled on a flexible substrate affecting the performance of the conductor.

[0072] like Figure 2 As shown, before activation, the liquid metal particles are discretely embedded in the SEBS elastomer, and there is an oxide layer on the surface of the liquid metal particles, and the ink is not conductive.

[0073] like Figure 3 As shown, after activation, the oxide layer on the surface of the liquid metal particles is evaporated and reassembled together to form a continuous liquid metal conductive network in situ in the SEBS elastomer, and the ink is conductive; under the synergistic effect of the two self-healing materials, SEBS and liquid metal, the activated ink has good conductivity and good stretchability, and can be used as a stretchable conductor in flexible electronic devices; compared with the method of laser selective sintering to activate liquid metal particles assembled on a flexible substrate, the SEBS with good stretchability and self-healing properties in the present invention wraps the liquid metal after in-situ activation therein, plays a packaging role, and ensures that the liquid metal will not overflow due to external force and destroy the pattern under continuous stretching.

[0074] like Figure 4 As shown in the figure, after laser activation, the ink changes from non-conductive to conductive. When the activation power is 40%, the ink sheet resistance decreases significantly. The sheet resistance reaches mΩ / □ level after detection by a four-probe sheet resistance meter. After conversion, the conductivity can reach 10 6 S / m, compared to the conductivity of the ink after mechanical activation 10 4 The S / m is significantly improved and can be used as a conductor in flexible electronic devices. When the power is 70%, most of the liquid metal evaporates, the pattern is destroyed and it is not conductive.

[0075] like Figure 5 As shown, compared with the traditional metal wire materials commonly used in current flexible electronic devices that can only be bent but not stretched, the liquid metal ink in the present invention has a change rate of ink resistance of less than 10% during multiple consecutive 100% stretching and has good recovery, which is more in line with the needs of flexible electronic devices.

[0076] like Figure 6As shown, compared with most of the current flexible antennas / coils prepared by combining thin solid metal materials or conductive nanomaterials on flexible substrates, which can only be bent but do not have good stretchability, the flexible coil prepared by the method of the present invention still maintains a stable frequency under 100% stretching and the S11 value at the frequency is below -10dB, which proves that the coil still has a good ability to transmit signals under high stretching conditions. Therefore, the present invention can be used to prepare flexible radio frequency devices.

[0077] It can be seen from the above method and the preparation process of Example 1 and Implementation 2 using the method that the method provided by the present invention synergistically utilizes the characteristics of two self-healing materials, liquid metal and SEBS. Liquid metal is liquid at room temperature, has a deformable and reconfigurable ability similar to a fluid, and has the high conductivity of metal. As an elastic polymer, SEBS has good stretchability and self-healing ability, providing a good flexible foundation for composite materials. The synergistic effect of the two makes the prepared wire have good conductivity and stretchability. At the same time, the structure and electrical properties can be kept relatively stable during the stretching process. In addition, through the key step of laser scanning in-situ activation of ink, the surface oxide layer of the liquid metal particles in SEBS can be accurately evaporated and sintered together, prompting the wire pattern to change from a non-conductive state to a conductive state. SEBS plays a role of encapsulation after the liquid metal particles are activated in situ, preventing liquid metal from overflowing and protecting the integrity of the pattern, thereby achieving high-quality preparation of stretchable wires.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a stretchable conductor based on laser in-situ activation of liquid metal composite materials, characterized in that: The preparation method comprises the following steps: S1. Preparation of liquid metal: The molten gallium and indium are mixed according to the mass ratio and heated in an oil bath to obtain liquid metal LM; S2. Preparation of liquid metal particles: S21, placing the liquid metal LM into a surfactant solution diluted with anhydrous ethanol, and performing water bath ultrasound to obtain a LM particle suspension; S22, after standing, take out the upper LM particle suspension, centrifuge and pour out the liquid, add anhydrous ethanol to wash away the excess surfactant, centrifuge and wash several times to obtain solid LM particles; S3. Preparation of SEBS solution: SEBS and an organic solvent are mixed according to a mass ratio and then ultrasonicated in a water bath until SEBS is completely dissolved to obtain a SEBS solution; Preparation of S4 and LM ink: The LM particles and the SEBS solution are mixed in proportion, shaken first and then magnetically stirred to obtain the LM ink; S5. Patterning of LM ink: S51, scrape LM ink on the polytetrafluoroethylene substrate, and transfer the ink and the substrate to a glass sheet after the solvent evaporates completely; S52, cutting a conductor pattern on the LM ink by laser; S6, In-situ activation of LM ink: The ink is activated in situ by laser scanning, and the conductor pattern is transformed from non-conductive to conductive; S7. Transfer and packaging of wires: The wire pattern was transferred onto the SEBS substrate film and encapsulated with a layer of SEBS film to obtain a stretchable wire based on liquid metal ink.

2. The method for preparing a stretchable conductor based on laser in-situ activation of liquid metal composite materials according to claim 1, characterized in that: In step S1, the mass ratio of gallium to indium is 75.5:24.5; and the oil bath heating time is 3 hours.

3. The method for preparing a stretchable conductor based on laser in-situ activation of liquid metal composite materials according to claim 1, characterized in that: In step S21, the liquid metal is a gallium-indium alloy, and the added volume of the liquid metal is 0.5 mL; the surfactant is ethyl 3-mercaptopropionate, the added volume of the surfactant solution is 15 mL, and the concentration of the surfactant solution is 0.1 mM / L; the water bath ultrasound time is 30 min.

4. The method for preparing a stretchable conductor based on laser in-situ activation of liquid metal composite materials according to claim 3, characterized in that: In step S22, the solution of the LM particle suspension is 30 mL; the washing amount of anhydrous ethanol added is 25-30 mL; the centrifugal speed of the centrifugal washing is 5000 r / min, the centrifugal time of the centrifugal washing is 15 min, and the number of washing times of the centrifugal washing is 2-3 times; the particle size of the prepared LM particles is 0.8-1.2 μm.

5. The method for preparing a stretchable conductor based on laser in-situ activation of liquid metal composite materials according to claim 1, characterized in that: In step S3, the organic solvent is a mixed solution of toluene and n-hexane; the mass ratio of SEBS particles to organic solvent in the SEBS solution is SEBS: n-hexane: toluene = 1:1:4; and the duration of the water bath ultrasonic mixing is 3-6 hours.

6. The method for preparing a stretchable conductor based on laser in-situ activation of liquid metal composite material according to claim 1, characterized in that: In step S4, the mass ratio of the LM particles to the SEBS solution is 7:1-8:1; the shaking time is 1-3 min, the magnetic stirring time is 30-60 min, and the speed of the magnetic stirring is 600 r / min.

7. The method for preparing a stretchable conductor based on laser in-situ activation of liquid metal composite material according to claim 1, characterized in that: In step S51, the coating is performed using an adjustable film-scraping applicator, and the height of the scraper is 500 μm; the volume of the LM ink is 3-5 mL; the glass sheet is 14 cm long, 7 cm wide, and 2 mm thick; and the solvent completely evaporates for more than 12 hours.

8. The method for preparing a stretchable conductor based on laser in-situ activation of liquid metal composite materials according to claim 7, characterized in that: In step S52, the laser is an ultraviolet laser; the cutting parameters are a rate of 500-1000 mm / s, a power of 50%-70%, a frequency of 40-60 kHz, and a number of laser cutting circles of 10.

9. The method for preparing a stretchable conductor based on laser in-situ activation of liquid metal composite materials according to claim 1, characterized in that: In step S6, the laser scanning range should completely include the conductor pattern, and the parameters of the laser in-situ activation are a rate of 500-1000 mm / s, a power of 40-60%, a frequency of 40-60 kHz, and a laser scanning circle of 1.

10. The method for preparing a stretchable conductor based on laser in-situ activation of liquid metal composite materials according to claim 1, characterized in that: In step S7, the SEBS base film is prepared by spin coating of a SEBS solution, the components of the SEBS solution are SEBS: n-hexane: toluene = 1:1:2 by weight, and the spin coating speed during the spin coating preparation is 100-500r / min, and the transfer is performed in a semi-cured state after 10-15min; the SEBS film for packaging is obtained by spin coating a SEBS solution with a composition of SEBS: n-hexane: toluene = 1:1:3 or 1:1:2 on a silicon wafer and then volatilizing it, and the volatilization time is more than 12h.

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