Liquid metal thin film, method of making and use thereof

Abstract

The present disclosure belongs to the technical field of laser precision machining, and provides a liquid metal film, a preparation method and application thereof. The preparation method comprises the following steps: spraying a dispersion liquid of liquid metal nanoparticles on a transparent substrate to obtain a processing material; opposing one side of the processing material, on which the liquid metal nanoparticles are sprayed, to one side of a target substrate; and focusing a laser at the interface between the transparent substrate and the liquid metal nanoparticles to perform laser processing. The present disclosure also discloses a liquid metal film prepared according to the above method and a flexible conductive device comprising the liquid metal film. The present disclosure utilizes the recoil pressure generated by gasification in the sintering process to realize the patterning of the liquid metal, so that the selection of the target substrate is more diverse, the selection of the processed pattern is more flexible, and the separation step between the conductive liquid metal film and the untreated liquid metal nanoparticles is omitted; and the liquid metal patterning has high efficiency and high flexibility under the premise of ensuring high precision.

Description

Technical Field

[0001] This disclosure relates to the field of laser precision machining technology, and in particular to liquid metal thin films, their preparation methods, and applications. Background Technology

[0002] Gallium-based alloys and other liquid metal materials possess excellent flexibility and conductivity, making them ideal materials for fabricating flexible conductive devices. Patterning of liquid metals is crucial for the fabrication of flexible liquid metal conductive devices. However, the extremely high surface energy of liquid metals makes it difficult to wet flexible substrates. This poses a challenge to existing patterning techniques in achieving high-precision fabrication of high-quality conductive films. While ultrasonic treatment of liquid metals to obtain liquid metal nanoparticles can overcome the surface energy, the oxide layer on the surface of each nanoparticle isolates them from each other, preventing the formation of conductive pathways. Therefore, how to sinter liquid metal nanoparticles to form conductive pathways between them has become a key focus of current liquid metal patterning processes. Current sintering techniques suffer from various problems: to ensure processing accuracy, evaporation sintering, photonic sintering, and thermal sintering often require methods such as mask printing to deposit liquid metal nanoparticles onto a substrate to obtain various patterns, resulting in limited processing flexibility. Furthermore, except for photonic sintering, other sintering methods have low processing efficiency; for example, evaporation sintering requires a one-day drying process.

[0003] In summary, there is still a lack of liquid metal patterning technology that can simultaneously guarantee processing accuracy and conductivity while also possessing advantages such as high processing efficiency, good processing flexibility, and low substrate requirements. Summary of the Invention

[0004] This disclosure provides liquid metal thin films, methods for their preparation, and applications, in order to at least solve the above-mentioned technical problems existing in the prior art.

[0005] According to a first aspect of this disclosure, a method for preparing a liquid metal thin film is provided, comprising the following steps:

[0006] A dispersion of liquid metal nanoparticles is sprayed onto a transparent substrate to obtain the processed material;

[0007] The side of the processing material coated with liquid metal nanoparticles is placed opposite the side of the target substrate; a laser is focused at the interface between the transparent substrate and the liquid metal nanoparticles to perform laser processing, thereby obtaining the liquid metal thin film.

[0008] According to one possible implementation of this disclosure, at least the following beneficial effects are achieved:

[0009] This disclosure utilizes pulsed lasers for selective sintering of liquid metal nanoparticles, allowing for flexible modification of the processing pattern via software. Simultaneously, the recoil pressure generated during vaporization in the sintering process facilitates the separation of the conductive liquid metal film from the untreated liquid metal nanoparticles, eliminating the need for complex separation steps.

[0010] Specifically, this disclosure involves spraying liquid metal nanoparticles onto the surface of a transparent substrate. Then, the side of the transparent substrate with the sprayed liquid metal nanoparticles is positioned opposite the side of the target substrate. A laser is incident from the side of the transparent substrate without the sprayed liquid metal nanoparticles. Utilizing the impact generated by the vaporization of the liquid metal nanoparticles under pulsed laser irradiation, the liquid metal nanoparticles are propelled to the surface of the target substrate while forming a film under laser processing. The liquid metal nanoparticles that are not laser-processed remain on the original transparent substrate, resulting in a conductive liquid metal thin film with a certain pattern on the surface of the target substrate.

[0011] In one embodiment, the dispersion of the liquid metal nanoparticles is prepared by ultrasonic treatment of liquid metal to obtain the dispersion of the liquid metal nanoparticles.

[0012] Specifically, the liquid metal, dispersant, and solvent are mixed and ultrasonically treated to obtain a dispersion of the liquid metal nanoparticles.

[0013] Specifically, the liquid metal is selected from at least one of gallium-indium alloy, gallium-indium-tin alloy, and bismuth-indium-tin-zinc alloy.

[0014] Specifically, the dispersant is selected from at least one of 3-mercapto-N-nonylpropionamide, polyacrylamide, sodium dodecyl sulfate, and polyethylene glycol fatty acid esters.

[0015] Specifically, the choice of the dispersant is not limited, as long as it can disperse the liquid metal in the solvent.

[0016] Specifically, the solvent is selected from at least one of anhydrous ethanol, isopropanol, glycerol, and dimethyl sulfoxide.

[0017] Specifically, the mass ratio of the liquid metal to the dispersant is 160:1 to 90:1.

[0018] Specifically, the ultrasonic treatment time is 2 hours to 5 hours.

[0019] In one embodiment, the diameter of the liquid metal nanoparticles is 20 nm to 600 nm.

[0020] In one embodiment, the transparent substrate is selected from sapphire, quartz glass, aluminum nitride, and polyethylene terephthalate (PET).

[0021] In one embodiment, the thickness of the transparent substrate is 0.5 mm to 1.5 mm.

[0022] In one embodiment, the dispersion of the liquid metal nanoparticles is sprayed onto the transparent substrate to form a liquid metal nanoparticle film; the thickness of the liquid metal nanoparticle film is 1 μm to 20 μm.

[0023] In one embodiment, the target substrate is placed on a displacement stage, and the processing material is placed on the side of the target substrate away from the displacement stage. The side of the processing material coated with the liquid metal nanoparticles is opposite to the side of the target substrate away from the displacement stage.

[0024] In one embodiment, the target substrate is selected from any one of quartz glass, silicon wafer, sapphire, PI film, and PDMS.

[0025] Specifically, the target substrate can be flexibly selected and can be any common substrate. To ensure the transfer effect, the surface of the target substrate should be sufficiently clean and flat, and have a certain degree of heat resistance.

[0026] Specifically, this disclosure utilizes the recoil force generated by the vaporization of liquid metal nanoparticles to achieve the patterning of liquid metal, making the selection of target substrates more diverse, including organosilicon elastomers such as PDMS, sapphire sheets, glass, silicon wafers, PI films, etc.

[0027] In one embodiment, the laser is incident from the side of the processed material that is not coated with the liquid metal nanoparticles.

[0028] In one embodiment, the laser is emitted from a laser, expanded and collimated by a lens, passes through a power adjustment module, enters a scanning galvanometer and a 4F system, is focused by an objective lens, and is imported into a processing file. Appropriate laser power, repetition frequency and scanning speed are set for laser processing.

[0029] In one embodiment, the laser processing method is line-by-line scanning; the laser scanning path planning is as follows: design the pattern to be processed, fill the scanning lines into the pattern, scan the outline of the pattern after scanning the interior of the pattern, and convert the final scanning path into a processing file that can be recognized by the processing equipment.

[0030] Specifically, scanning the outline of the pattern after scanning the inside of the pattern can make the patterned liquid metal more firmly fixed on the target substrate.

[0031] Specifically, the liquid metal nanoparticle film formation and patterning of this disclosure are completed simultaneously. To prepare a conductive liquid metal thin film with a specific pattern, it is only necessary to directly and uniformly spray the liquid metal nanoparticles onto the surface of a transparent substrate, and then set the laser scanning path. No additional pre-steps (depositing liquid metal nanoparticles into a specific pattern on the substrate surface using various printing methods) or subsequent steps (separating the laser-processed conductive liquid metal thin film from the unprocessed non-conductive liquid metal nanoparticles using various methods after laser processing) are required. Furthermore, the method of this disclosure also has the potential to prepare liquid metal thin films with three-dimensional structures (e.g., pyramids).

[0032] In one possible implementation, the laser is a nanosecond laser.

[0033] In one embodiment, the wavelength of the laser is 532nm to 1650nm, the repetition frequency is 2kHz to 20kHz, the pulse width is <100ns, and the single pulse energy required for processing is >0.3mJ.

[0034] In one embodiment, the laser scanning speed is 50 mm / s to 3000 mm / s, the scanning range is -25° to 25°, the spot diameter is 30 μm to 44 μm, and the scanning line spacing is 30 μm to 44 μm.

[0035] According to a second aspect of this disclosure, a liquid metal thin film prepared according to the above-described preparation method is provided.

[0036] According to a third aspect of this disclosure, a flexible conductive device is provided, the flexible conductive device comprising the above-described liquid metal thin film.

[0037] Specifically, this disclosure utilizes the advantages of laser direct writing technology (such as wide applicability to materials, high speed, high precision, and good flexibility) to enable liquid metal patterning to achieve both high efficiency and high flexibility while ensuring high precision. It has broad application prospects in the manufacture of flexible conductive devices such as flexible circuits and is expected to achieve large-scale industrial application.

[0038] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0039] The above and other objects, features, and advantages of this disclosure will become readily apparent from the following detailed description of exemplary embodiments, taken in conjunction with the accompanying drawings. Several embodiments of this disclosure are illustrated in the drawings by way of example and not limitation, in which:

[0040] In the accompanying drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

[0041] Figure 1 The diagram illustrates the laser-induced liquid metal patterning technique in Embodiments 1 and 2 of this disclosure; specifically, it shows a cross-sectional view of the sample perpendicular to its thickness direction.

[0042] Figure 2 The diagram shows the effect of transferring a liquid metal thin film onto a target substrate according to Embodiment 1 of this disclosure;

[0043] Figure 3 Scanning electron microscope (SEM) images of the liquid metal thin film transferred to the surface of the target substrate in Embodiment 1 of this disclosure are shown; wherein, a) is a scanning electron microscope image at 400x magnification and b) is a scanning electron microscope image at 2000x magnification.

[0044] Figure 4 The diagram shows the effect of the liquid metal thin film transferred onto the target substrate in Embodiment 2 of this disclosure.

[0045] Figure label:

[0046] 1-Nanosecond laser; 2-Objective lens; 3-Transparent substrate; 4-Liquid metal nanoparticles; 5-Target substrate. Detailed Implementation

[0047] To make the objectives, features, and advantages of this disclosure more apparent and understandable, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0048] Flexible conductive devices are fundamental components in flexible electronics applications. Gallium-based alloys and other liquid metal materials possess both excellent flexibility and conductivity, making them ideal materials for fabricating flexible conductive devices. Patterning of liquid metals is crucial for the fabrication of flexible liquid metal conductive devices. However, the extremely high surface energy of liquid metals makes it difficult for them to wet flexible substrates. This poses a challenge to existing patterning techniques, such as contact printing, stencil transfer, and direct writing, in achieving high-precision fabrication of high-quality conductive films. On the other hand, liquid metals are easily oxidized and encapsulated by a non-conductive solid oxide layer. This oxide layer allows the liquid metal to wet heterogeneous surfaces, indicating that the surface energy of liquid metals can be overcome by ultrasonically processing them to obtain liquid metal nanoparticles. However, each liquid metal nanoparticle has an oxide layer of approximately 1–3 nm on its surface, isolating the nanoparticles from each other. Since the oxide layer is non-conductive, conductive pathways cannot be formed between the liquid metal nanoparticles. Therefore, how to sinter liquid metal nanoparticles to form conductive pathways between them has become a key focus of current liquid metal patterning processes. Currently, the main sintering technologies for liquid metal nanoparticles include photonic sintering, evaporation sintering, thermal sintering, and mechanical sintering. These sintering technologies have various problems: to ensure processing accuracy, evaporation sintering, photonic sintering, and thermal sintering often require methods such as mask printing to deposit liquid metal nanoparticles onto a substrate to obtain various patterns, which limits their processing flexibility. Furthermore, except for photonic sintering, other sintering methods have low processing efficiency; for example, evaporation sintering requires a one-day drying process.

[0049] Laser direct writing technology utilizes a high-energy focused laser spot to flexibly scan three dimensions of space to process materials, offering advantages such as wide applicability, high precision, and good flexibility. By providing photothermal energy, laser direct writing causes nanoparticles to break due to the thermal expansion mismatch between the liquid metal and its oxide layer, resulting in interconnected conductive pathways between the nanoparticles. Laser direct writing technology has the potential to overcome current technological bottlenecks in terms of patterning accuracy, process stability, manufacturing efficiency, and scalability. However, laser processing of liquid metal is a multi-physics process involving light, heat, and force, with relatively complex mechanisms and process parameters. Therefore, the interaction mechanism between liquid metal and laser and its impact on the patterning process are still under investigation.

[0050] In summary, there is still a lack of liquid metal patterning technology that can simultaneously guarantee processing accuracy and conductivity while also possessing advantages such as high processing efficiency, good processing flexibility, and low substrate requirements.

[0051] To address the shortcomings of existing technologies, this disclosure aims to solve the following technical problem: Based on pulsed laser direct writing technology, it proposes a liquid metal patterning method that, while ensuring processing accuracy and conductivity, also possesses advantages such as high processing efficiency, good processing flexibility, and lower substrate requirements. Liquid metal is ultrasonically treated to obtain liquid metal nanoparticles, which are then sprayed onto a transparent substrate. A nanosecond laser is focused at the interface between the liquid metal nanoparticles and the transparent substrate, causing the liquid metal nanoparticles at the interface to rapidly heat and vaporize. The recoil pressure generated by vaporization propels the broken liquid metal nanoparticles within the laser scanning area to the target substrate while simultaneously forming a conductive film, completing the sintering and patterning process of the liquid metal nanoparticles. Laser direct writing technology utilizes a galvanometer to control the deflection of the laser beam, enabling high-speed processing with high precision. Furthermore, the processing pattern can be freely modified via software, providing sufficient processing flexibility. Because this technology utilizes the recoil pressure generated by vaporization during laser sintering to propel the pre-treated conductive liquid metal film onto the target substrate surface, it has lower requirements for the target substrate and also eliminates the complex process of separating the conductive liquid metal film from the unsintered liquid metal nanoparticles.

[0052] The following examples illustrate this in detail.

[0053] Example 1

[0054] This embodiment prepares a liquid metal thin film, and the specific process is as follows:

[0055] The transparent substrate was a double-polished sapphire sheet, 0.5 mm thick and 2 inches in size. The target substrate was a cured PDMS. A liquid metal conductive film was transferred onto the target substrate surface via the vaporization propulsion of liquid metal nanoparticles under pulsed laser irradiation, resulting in a rectangular liquid metal film with good conductivity, measuring 9 mm in length and 2 mm in width.

[0056] (1) Sample preparation before processing:

[0057] First, 360 mg of eutectic gallium-indium alloy (comprising 75% Ga and 25% In by mass fraction) and 2.8 mg of 3-mercapto-N-nonylpropionamide were added to 4 mL of anhydrous ethanol. The mixture was then sonicated for 3 h to obtain a dispersion of liquid metal nanoparticles. After sonication, the dispersion was diluted to 40 mL with anhydrous ethanol. The dispersion of liquid metal nanoparticles was then sprayed onto the surface of a double-polished sapphire wafer using a spray gun. After the anhydrous ethanol evaporated, a 60 mg film of liquid metal nanoparticles was obtained on the sapphire surface.

[0058] Agent A and Agent B of PDMS were mixed and stirred at a mass ratio of 10:1, then degassed in a vacuum for 2 hours to remove air bubbles. The uncured PDMS was then poured into a mold and placed in a vacuum at 60°C for 2 hours to finally obtain cured PDMS, which was then used as the target substrate.

[0059] (2) Patterning of liquid metal using nanosecond lasers:

[0060] A PDMS sheet is placed on a displacement stage, and a double-polished sapphire sheet coated with liquid metal nanoparticles is placed on the PDMS, with the side coated with liquid metal nanoparticles in contact with the side of the PDMS facing away from the displacement stage. A nanosecond laser is incident from the side of the double-polished sapphire sheet not coated with liquid metal nanoparticles. The displacement stage is controlled to adjust the focus so that the nanosecond laser is focused at the interface between the double-polished sapphire sheet and the liquid metal nanoparticles. A processing pattern (9mm long, 2mm wide rectangle) is drawn in the control software, and then scan lines are filled into the pattern. The laser scanning is then started. After scanning, the double-polished sapphire sheet is removed, and the surface of the PDMS will show the following result: Figure 2 The transfer effect shown. Figure 2 After processing, a rectangular liquid metal film measuring 9 mm in length and 2 mm in width was fixed on the target substrate surface, demonstrating the high fidelity of the patterning process and verifying the feasibility and high precision of this disclosure. A scanning electron microscope image of the liquid metal film transferred to the PDMS surface is shown below. Figure 3 As shown, Figure 3 The liquid metal nanoparticles transferred from the surface of a transparent double-polished sapphire sheet to the surface of PDMS have formed a film. The interconnectedness of the sintered liquid metal nanoparticles gives the film good conductivity, confirming that the liquid metal nanoparticles form a conductive path after laser sintering.

[0061] In this embodiment, the optical parameters of the laser are set as follows: wavelength of 1064nm, pulse width of 5ns, repetition frequency of 10kHz, scanning speed of 1500mm / s, and single pulse energy required for processing of 0.5mJ.

[0062] The laser scanning path is set as follows: the laser scanning line spacing is 30μm, the scanning path is uniformly filled inside the processed pattern, and after the pattern scanning is completed, a second scan is performed along the pattern outline to make the liquid metal film transferred on the target substrate more firmly fixed on the target substrate.

[0063] The above schematic diagram of laser-induced liquid metal patterning is shown below. Figure 1As shown. Specifically, the nanosecond laser 1 passes through the objective lens 2 and is focused on the interface between the transparent substrate 3 and the liquid metal nanoparticles 4. The liquid metal nanoparticles 4 near the interface rapidly heat up and vaporize under the action of the nanosecond laser 1, generating a recoil force. The nearby liquid metal nanoparticles 4 heat up and form a film under the action of the nanosecond laser 1. At the same time, the recoil force impacts the liquid metal film with good conductivity onto the surface of the target substrate 5, realizing the patterning of liquid metal.

[0064] Example 2

[0065] This embodiment prepares a liquid metal thin film, and the specific process is as follows:

[0066] The transparent substrate is a double-polished sapphire wafer, 0.5 mm thick and 2 inches in size. The target substrate is a silicon wafer, 0.38 mm thick and 2 inches in size. Figure 1 The diagram shows a cross-sectional view of the processed sample perpendicular to its thickness direction. The transfer of a liquid metal conductive film was achieved through the vaporization and propulsion of liquid metal nanoparticles under pulsed laser irradiation, resulting in a 3×3 array of liquid metal films composed of squares with sides of 3 mm on the target substrate surface.

[0067] (1) Sample preparation before processing:

[0068] First, 360 mg of eutectic gallium-indium alloy (comprising 75% Ga and 25% In by mass fraction) and 2.8 mg of 3-mercapto-N-nonylpropionamide were added to 4 mL of anhydrous ethanol. The mixture was then sonicated for 3 h to obtain a dispersion of liquid metal nanoparticles. After sonication, the dispersion was diluted to 40 mL with anhydrous ethanol. The dispersion of liquid metal nanoparticles was then sprayed onto the surface of a double-polished sapphire wafer using a spray gun. After the anhydrous ethanol evaporated, a 60 mg film of liquid metal nanoparticles was obtained on the sapphire surface.

[0069] Meanwhile, the silicon wafer was placed in deionized water and ultrasonically cleaned for 10 minutes to serve as the target substrate.

[0070] (2) Patterning of liquid metal using nanosecond lasers:

[0071] A silicon wafer is placed on a displacement stage. A double-polished sapphire wafer with liquid metal nanoparticles sprayed onto its surface is placed on the silicon wafer, with the side coated with liquid metal nanoparticles in contact with the side of the silicon wafer facing away from the displacement stage. A nanosecond laser is incident from the side of the double-polished sapphire wafer not coated with liquid metal nanoparticles. The displacement stage is controlled to adjust the focus, so that the nanosecond laser is focused at the interface between the double-polished sapphire wafer and the liquid metal nanoparticles. The processing pattern is drawn in the control software: a 3×3 array of squares with a side length of 3mm. Then, scan lines are filled into the pattern, and the laser scanning is started. After the scanning is completed, the double-polished sapphire wafer is removed, and the surface of the silicon wafer can be obtained as shown in the image. Figure 4 The transfer effect shown. Figure 4 The image shows that after processing, a 3×3 array of liquid metal thin films, consisting of squares with sides of 3mm, is fixed on the surface of the target substrate, demonstrating the high fidelity of the imaging process. Unlike PDMS, which is an elastomer, silicon wafers are hard and brittle materials. Figure 4 The transfer effect verifies the high versatility of this disclosure for target substrates with different properties.

[0072] In this embodiment, the optical parameters of the laser are set as follows: wavelength of 1064nm, pulse width of 5ns, repetition frequency of 2kHz, scanning speed of 300mm / s, and single pulse energy required for processing of 0.41mJ.

[0073] The laser scanning path is set as follows: the laser scanning line spacing is 30μm, the scanning path is uniformly filled inside the processed pattern, and after the pattern scanning is completed, a second scan is performed along the pattern outline to make the liquid metal film transferred on the target substrate more firmly fixed on the target substrate.

[0074] Example 3

[0075] This embodiment prepares a liquid metal thin film, and the specific preparation process is the same as in Example 1. However, in this embodiment, the laser wavelength is 532 nm, the repetition frequency is 20 kHz, the pulse width is 95 ns, the scanning speed is 50 mm / s, and the scanning line spacing is 44 μm.

[0076] Example 4

[0077] This embodiment prepares a liquid metal thin film, and the specific preparation process is the same as in Example 1. However, in this embodiment, the laser wavelength is 1650 nm, the pulse width is 50 ns, the scanning speed is 3000 mm / s, and the scanning line spacing is 44 μm.

[0078] All the above embodiments utilize pulsed lasers for selective sintering of liquid metal nanoparticles. The processing pattern can be freely modified via software, providing great flexibility in pattern selection. Simultaneously, the recoil pressure generated during vaporization in the sintering process is used to separate the conductive liquid metal film from the untreated liquid metal nanoparticles, eliminating the need for complex separation steps.

[0079] Comparative Example 1

[0080] This comparative example prepared a liquid metal thin film. The difference between this example and Example 1 is that this comparative example uses photonic sintering to prepare the liquid metal thin film. That is, firstly, liquid metal nanoparticles are deposited on a substrate to obtain a target pattern by mask printing. Then, the printed liquid metal nanoparticles are heated by a high-intensity pulsed light flash lamp to destroy the oxide layer, thereby creating a conductive path to prepare the liquid metal thin film.

[0081] This comparative example requires the deposition of liquid metal nanoparticles onto a substrate using a mask printing method to obtain the target pattern, which has poor processing flexibility.

[0082] Comparative Example 2

[0083] This comparative example prepared a liquid metal thin film. The difference from Example 1 is that, in this comparative example, the liquid metal nanoparticles were not first sprayed onto a transparent substrate, but were directly sprayed onto the target substrate for laser direct writing. The rest of the process is the same as in Example 1.

[0084] Because this comparative example did not use a transparent substrate, but instead directly sprayed liquid metal nanoparticles onto the target substrate for laser processing, the liquid metal film formed during sintering would mix with the untreated liquid metal nanoparticles, requiring subsequent separation, which is a complex process.

[0085] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this disclosure can be achieved, and this is not limited herein.

[0086] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0087] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A method for preparing a liquid metal thin film, characterized in that, Includes the following steps: A dispersion of liquid metal nanoparticles is sprayed onto a transparent substrate to obtain the processed material; The side of the processing material coated with liquid metal nanoparticles is placed opposite the side of the target substrate; a laser is focused at the interface between the transparent substrate and the liquid metal nanoparticles to perform laser processing, thereby obtaining the liquid metal film; wherein, the laser is emitted from a laser, expanded and collimated by a lens, passes through a power adjustment module, and enters a scanning galvanometer and a 4F system, and is then focused by an objective lens; The laser processing method is line-by-line scanning; the laser scanning path planning is as follows: design the graphic to be processed, fill the scanning lines into the graphic, scan the outline of the graphic after scanning the inside of the graphic, and convert the final scanning path into a processing file that can be recognized by the processing equipment. The laser has a repetition frequency of 2kHz to 20kHz, a single pulse energy of 0.41 to 0.5mJ required for processing, a scanning speed of 50mm / s to 3000mm / s, and a spot diameter of 30μm to 44μm.

2. The preparation method according to claim 1, characterized in that, The dispersion of the liquid metal nanoparticles is prepared by the following method: ultrasonic treatment of liquid metal to obtain the dispersion of the liquid metal nanoparticles; The liquid metal, dispersant, and solvent are mixed and subjected to ultrasonic treatment to obtain a dispersion of the liquid metal nanoparticles; The liquid metal is selected from at least one of gallium indium alloy, gallium indium tin alloy, and bismuth indium tin zinc alloy; The mass ratio of the liquid metal to the dispersant is 160:1 to 90:

1.

3. The preparation method according to claim 1, characterized in that, The transparent substrate is selected from any one of sapphire, quartz glass, aluminum nitride, and polyethylene terephthalate; The thickness of the transparent substrate is 0.5mm to 1.5mm.

4. The preparation method according to claim 1, characterized in that, The dispersion of the liquid metal nanoparticles is sprayed onto the transparent substrate to form a liquid metal nanoparticle film; the thickness of the liquid metal nanoparticle film is 1μm~20μm.

5. The preparation method according to claim 1, characterized in that, The target substrate is placed on a displacement stage, and the processing material is placed on the side of the target substrate away from the displacement stage. The side of the processing material coated with the liquid metal nanoparticles is opposite to the side of the target substrate away from the displacement stage. The target substrate is selected from any one of quartz glass, silicon wafer, sapphire, PI film, and PDMS.

6. The preparation method according to claim 1, characterized in that, The laser is incident from the side of the processed material that is not coated with the liquid metal nanoparticles.

7. The preparation method according to claim 1, characterized in that, The laser in question is a nanosecond laser.

8. The preparation method according to claim 7, characterized in that, The wavelength of the laser is 532nm~1650nm, and the pulse width is <100ns; The scanning range of the laser is -25° to 25°.

9. A liquid metal thin film prepared by the preparation method according to any one of claims 1 to 8.

10. A flexible conductive device, characterized in that, The flexible conductive device includes the liquid metal thin film of claim 9.

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