Liquid metal self-assembly film and preparation method thereof

Abstract

The application discloses a liquid metal self-assembly film and a preparation method thereof. The preparation method comprises the following steps: adding liquid metal into water to obtain a liquid metal solution; adding a surfactant solution into the liquid metal solution, and performing ultrasonic mixing to obtain a liquid metal self-assembly seed solution; wherein, the solvent of the surfactant solution is an organic solvent which has a smaller density than water and is immiscible with water; and mixing the liquid metal self-assembly seed solution with water to obtain the liquid metal self-assembly film at an oil-water interface. The surfactant is grafted on the surface of liquid metal nanoparticles by ultrasonic. After mixing the liquid metal self-assembly seed solution with water, the liquid metal nanoparticles modified by the surfactant are attracted to each other by non-covalent force at the oil-water liquid-liquid interface, and the preparation of the liquid metal film is rapidly self-assembled in a few seconds. The method provided by the application is simple in process, fast in preparation speed, and does not need expensive equipment.

Description

Technical Field

[0001] This invention relates to the field of liquid metal thin film technology, and in particular to a self-assembled liquid metal thin film and its preparation method. Background Technology

[0002] Liquid metals (generally referring to gallium and its alloys) possess both fluid and metallic properties, exhibiting high electrical and thermal conductivity, and good biocompatibility, making them widely applicable in wearable flexible electronics, catalysis, and biomedicine. However, existing methods for preparing liquid metal thin films mainly include molding, printing, and thermal evaporation (e.g., Chinese patents CN106498348A and CN112662999A). Thermal evaporation uses liquid metal as an evaporation source, undergoing one or more thermal evaporations in a thermal evaporation device to evaporate liquid metal particles that are deposited on the surface of a flexible substrate. While thermal evaporation offers some improvement in process complexity and equipment requirements compared to molding and printing, these methods still suffer from relatively expensive and complex equipment, relatively complex fabrication processes, and low production efficiency. Providing a simpler, lower-cost, and more efficient method is crucial for the widespread application of liquid metal thin films.

[0003] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a liquid metal self-assembled thin film and its preparation method, which aims to solve the problems of relatively complex process, expensive equipment and low production efficiency of existing liquid metal thin film preparation methods.

[0005] The technical solution of the present invention is as follows:

[0006] A first aspect of the present invention provides a method for preparing a self-assembled liquid metal thin film, comprising the steps of:

[0007] A surfactant solution and a liquid metal are provided, wherein the solvent of the surfactant solution is an organic solvent with a density less than that of water and immiscible with water;

[0008] The liquid metal is added to water to obtain a liquid metal solution;

[0009] The surfactant solution is added to the liquid metal solution, and after ultrasonic mixing, a liquid metal self-assembly seed solution is obtained.

[0010] After mixing the liquid metal self-assembly seed solution with water, the lower layer is an aqueous phase and the upper layer is an oil phase, and the liquid metal self-assembly film is obtained at the oil-water interface.

[0011] Optionally, the organic solvent is selected from at least one of methyl methacrylate, toluene, and n-hexane;

[0012] And / or, the surfactant is selected from surfactants containing a single carboxyl group, wherein the surfactant containing a single carboxyl group is selected from at least one of acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonacrylic acid, icosanoic acid, ethylene glycol, butenoic acid, pentenoic acid, hexenoic acid, heptadecanoic acid, octadecanoic acid, nonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid, heptadecanoic acid, heptadecenoic acid, octadecenoic acid, nonadecenoic acid, and icosanoic acid;

[0013] And / or, the liquid metal is selected from gallium indium tin alloy and eutectic gallium indium.

[0014] Optionally, the concentration of the surfactant in the surfactant solution is 0.5–9 mmol / L;

[0015] And / or, in the liquid metal solution, the concentration of the liquid metal is 10 to 400 mg / mL.

[0016] Optionally, the volume ratio of the surfactant solution to the liquid metal solution is (1-5):(9-5).

[0017] Optionally, the ultrasonic mixing time is 10 to 120 minutes, and the ultrasonic mixing temperature is 0 to 1°C.

[0018] Optionally, in the step of mixing the liquid metal self-assembly seed solution with water, the volume ratio of the liquid metal self-assembly seed solution to the water is 10:(20-100).

[0019] Optionally, the method for preparing the liquid metal self-assembled thin film further includes the step of:

[0020] Provide the first base;

[0021] The first substrate is vertically inserted from the oil phase into the lower aqueous phase. Then, the end of the first substrate inserted into the aqueous phase is tilted upward and lifted until it leaves the upper surface of the oil phase. The liquid metal self-assembled film at the oil-water interface is transferred onto the first substrate, and the liquid metal self-assembled film is prepared on the first substrate.

[0022] Optionally, the method for preparing the liquid metal self-assembled thin film further includes the step of:

[0023] A flexible second substrate with a preset pattern is provided; the flexible second substrate is vertically inserted from the oil phase into the lower aqueous phase, and then the end of the flexible second substrate inserted into the aqueous phase is tilted upward until it leaves the upper surface of the oil phase, and the liquid metal self-assembled film at the oil-water interface is transferred onto the flexible second substrate to form a patterned liquid metal self-assembled film on the flexible second substrate, and then ethanol is sprayed onto the patterned liquid metal self-assembled film;

[0024] Provides metal transfer substrate;

[0025] The metal transfer substrate is heated, and the flexible second substrate containing the patterned liquid metal self-assembled film is disposed on the heated metal transfer substrate, wherein the patterned liquid metal self-assembled film is attached to the metal transfer substrate.

[0026] The patterned liquid metal self-assembled film is transferred onto the metal transfer substrate by pressing the flexible second substrate vertically on the side opposite to the metal transfer substrate, thereby preparing the patterned liquid metal self-assembled film on the metal transfer substrate.

[0027] In a second aspect, the present invention provides a liquid metal self-assembled thin film, wherein it is prepared using the preparation method of the present invention as described above.

[0028] Optionally, the thickness of the liquid metal self-assembled ultrathin film is 300–1000 nm.

[0029] Beneficial Effects: This invention provides a simple bottom-up self-assembly method. Using ultrasonic technology, surfactants are grafted onto the surface of liquid metal nanoparticles, resulting in surfactant-modified liquid metal nanoparticles. When the self-assembly seed solution containing these surfactant-modified nanoparticles is mixed with water, the lower layer is an aqueous phase and the upper layer is an oil phase. At the oil-water interface, the surfactant-modified liquid metal nanoparticles attract each other through non-covalent forces, rapidly forming a dense film structure within seconds, thus achieving rapid self-assembly of liquid metal thin films. Simultaneously, the non-covalent forces between the surfactant-modified liquid metal nanoparticle droplets also enhance the stability of the film. The preparation method provided by this invention is simple, fast, efficient, and requires no expensive equipment. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of how, in an embodiment of the present invention, a first substrate is vertically inserted from the oil phase into the aqueous phase below, and then the end of the first substrate inserted into the aqueous phase is tilted upwards until it reaches the upper surface of the oil phase, so as to transfer the liquid metal self-assembled film at the oil-water interface onto the first substrate.

[0031] Figure 2 (a) is a schematic diagram of a metal transfer substrate and a flexible second substrate with a patterned liquid metal self-assembled film on its surface; (b) is a schematic diagram of a flexible second substrate with a patterned liquid metal film disposed on a metal transfer substrate, such that the patterned liquid metal self-assembled film is attached to the metal transfer substrate and the flexible second substrate is pressed vertically to the side away from the metal transfer substrate; (c) is a schematic diagram of the transfer of the patterned liquid metal film from the flexible second substrate to the metal transfer substrate.

[0032] Figure 3 The images show the laser confocal Raman spectra of the hexanoic acid-modified liquid metal self-assembled thin film prepared in Example 1 and the octadecenoic acid-modified liquid metal self-assembled thin film prepared in Example 2.

[0033] Figure 4 The image shown is a 50,000x SEM image of the octadecenoic acid-modified liquid metal self-assembled thin film prepared in Example 2 of this invention, taken by high-resolution scanning electron microscopy after being sampled on a glass slide.

[0034] Figure 5 The self-healing test results of the octadecenoic acid-modified liquid metal self-assembled film prepared by mixing the liquid metal self-assembly seed solution in Example 2 with ultrapure water at a volume ratio of 1:9 are shown in (a) the first image of the film; (b) the first self-healing image; (c) the third image of the film; and (d) the third self-healing image.

[0035] Figure 6 This is a diagram showing the result of transferring the liquid metal self-assembled film on the flexible patterned PDMS substrate after film removal in Example 3 onto a copper substrate. Detailed Implementation

[0036] This invention provides a self-assembled liquid metal thin film and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0038] This invention provides a method for preparing a self-assembled liquid metal thin film, comprising the following steps:

[0039] S10. Provide a surfactant solution and liquid metal, wherein the solvent of the surfactant solution is an organic solvent with a density less than that of water and immiscible with water;

[0040] S20. Add the liquid metal to water to obtain a liquid metal solution;

[0041] S30. The surfactant solution is added to the liquid metal solution, and after ultrasonic mixing, a liquid metal self-assembly seed solution is obtained.

[0042] S40. After mixing the liquid metal self-assembly seed solution with water, the lower layer is an aqueous phase and the upper layer is an oil phase, and the liquid metal self-assembly film is obtained at the oil-water interface.

[0043] Unlike traditional top-down photolithography and printing, this invention provides a simple bottom-up self-assembly method, namely liquid-liquid interface self-assembly. Liquid metal nanoparticles (also known as liquid metal nanodroplets) exhibit high fluidity at the oil-water interface, enabling rapid equilibrium assembly. This high fluidity also allows for the self-correction of defects in the liquid metal self-assembled film, giving it self-healing properties.

[0044] This invention first utilizes ultrasonic technology to add a surfactant solution to a liquid metal solution for ultrasonic mixing, grafting the surfactant onto the surface of liquid metal nanoparticles to obtain surfactant-modified liquid metal nanoparticles. Then, the liquid metal self-assembly seed solution containing surfactant-modified liquid metal nanoparticles is mixed with water. The solution rapidly separates into layers: the organic solvent (oil phase) is on top, and water is on the bottom. At the oil-water interface, the surfactant-modified liquid metal nanoparticles attract each other through non-covalent forces between the surfactants, rapidly forming a dense film structure within seconds, achieving rapid self-assembly of liquid metal thin films. Simultaneously, the non-covalent forces between the surfactant-modified liquid metal nanoparticle droplets also enhance the film's stability. The preparation method provided by this invention is simple, fast, efficient, and requires no expensive equipment, making it suitable for industrial production.

[0045] In this embodiment, by modifying the surface of liquid metal nanoparticles, liquid metal nanoparticles with high colloidal stability and uniform dispersion can be obtained, and liquid metal nanoparticles with controllable size can be formed. Specifically, the particle size of the liquid metal nanoparticles is 50-300 nm.

[0046] In this embodiment, liquid metal is added to water to obtain a liquid metal solution, and then a surfactant solution is added to the liquid metal solution for ultrasonic mixing. The purpose of this ultrasonic mixing is twofold: firstly, if the surfactant solution is directly added to the liquid metal for ultrasonic mixing, the amount of surfactant grafted onto the surface of the liquid metal will be very high, and a high number of surfactant grafts will make it difficult for subsequent self-assembly to form; secondly, since liquid metal is not a stable system in the oil phase (organic solvent), it will cause a large amount of liquid metal to agglomerate and precipitate during ultrasonic mixing. Therefore, it is necessary to first add the liquid metal to water to form a liquid metal solution, and then mix it with the surfactant solution by ultrasonic mixing.

[0047] In step S10, in one embodiment, the organic solvent is selected from at least one of methyl methacrylate, toluene, and n-hexane, but is not limited thereto. These organic solvents are immiscible with water and have a lower density than water. As an oil phase, they dissolve surfactants, further reducing the surface energy of the liquid metal nanoparticles, making self-assembly easier.

[0048] In one embodiment, the liquid metal is selected from gallium-based liquid metals. The gallium-based liquid metal is selected from gallium-indium-tin alloys and eutectic gallium-indium, but is not limited thereto. Gallium-based liquid metals have melting points close to room temperature and possess both metallic and liquid properties, spontaneously forming a thin interfacial oxide layer, i.e., a gallium oxide layer. The presence of this oxide layer allows the liquid metal to form complex, stable structures and tunable reactivity. The presence of the oxide layer further reduces the high surface tension of the liquid metal, improving its wettability.

[0049] In one embodiment, the surfactant is selected from surfactants containing a single carboxyl group. In this embodiment, the carboxyl group can be used to bind to the oxide layer on the surface of the liquid metal nanoparticles to achieve the grafting of the surfactant onto the liquid metal nanoparticles.

[0050] In one embodiment, the surfactant containing a single carboxyl group is selected from at least one of acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, icosanoic acid, ethylene glycol, butenoic acid, pentenoic acid, hexenoic acid, heptadecanoic acid, octadecanoic acid, nonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid, heptadecanoic acid, heptadecanoic acid, octadecenoic acid, nonadecanoic acid, and icosanoic acid, but is not limited thereto. These surfactants containing a single carboxyl group can utilize the carboxyl group to bind to the oxide layer on the surface of liquid metal nanoparticles, thereby achieving the grafting of the surfactant onto the liquid metal nanoparticles.

[0051] In one embodiment, the concentration of the surfactant in the surfactant solution is 0.5–9 mmol / L, for example, it can be 0.5 mmol / L, 1 mmol / L, 2 mmol / L, 3 mmol / L, 4 mmol / L, 5 mmol / L, 6 mmol / L, 7 mmol / L, 8 mmol / L, or 9 mmol / L. This concentration of surfactant is more conducive to the self-assembly of liquid metal into a dense film. When the surfactant concentration is below 0.5 mmol / L, film formation is not favorable; when the surfactant concentration is above 9 mmol / L, large agglomerates are easily formed, which is not conducive to the formation of a dense self-assembled liquid metal film.

[0052] In step S20, in one embodiment, the liquid metal is added to ultrapure water and mixed to obtain a liquid metal solution. In a further embodiment, the mixing is ultrasonic mixing.

[0053] In one embodiment, the concentration of the liquid metal in the liquid metal solution is 10–400 mg / mL. For example, it can be 10 mg / L, 30 mg / L, 50 mg / mL, 100 mg / L, 200 mg / L, 300 mg / L, or 400 mg / L. This concentration of surfactant is more conducive to the self-assembly of liquid metal into a dense film. When the concentration of liquid metal is below 10 mg / L, film formation is not favorable. When the concentration of liquid metal is above 400 mg / L, large agglomerates are easily formed, which is not conducive to the formation of a dense self-assembled liquid metal film.

[0054] In step S30, in one embodiment, the volume ratio of the surfactant solution to the liquid metal solution is (1-5):(9-5). This ratio can make the self-assembled liquid metal film more dense.

[0055] In one embodiment, the ultrasonic mixing time is 10–120 min (e.g., 10 min, 20 min, 30 min, 50 min, 80 min, 100 min, or 120 min), and the ultrasonic mixing temperature is 0–1 °C (e.g., 0 °C, 0.5 °C, or 1 °C). At low temperatures of 0–1 °C, the grafting of surfactants onto liquid metal particles is more stable. Excessively high temperatures can damage the oxide layer on the surface of the liquid metal nanoparticles and hinder the grafting process, making the liquid metal nanoparticles more prone to aggregation, thus preventing grafting and self-assembly. This invention uses ultrasound to graft surfactants onto the oxide layer surface of liquid metal nanoparticles. The ultrasonic mixing time allows for more complete grafting. When the ultrasonic mixing time is less than 10 min, the grafting of surfactants onto liquid metal nanoparticles is insufficient, resulting in waste. When the ultrasonic mixing time is greater than 120 min, the localized high temperature caused by ultrasound affects the oxide layer of the liquid metal nanoparticles, leading to liquid metal aggregation, which is detrimental to the grafting process.

[0056] Of course, in steps S20 and S30, the liquid metal can also be added to water, then a surfactant solution can be added, and ultrasonic mixing can be performed to obtain a liquid metal self-assembly seed solution.

[0057] In step S40, in one embodiment, the volume ratio of the liquid metal self-assembly seed solution to water is 10:(20-100). This volume ratio ensures a denser liquid metal self-assembly film.

[0058] In one embodiment, at the oil-water interface, the volume of the liquid metal self-assembled film in the aqueous phase is approximately 20%, and the volume of the liquid metal self-assembled film in the oil phase is approximately 80%.

[0059] In one embodiment, the water is ultrapure water.

[0060] In one embodiment, the method for preparing the liquid metal self-assembled thin film further includes the step of:

[0061] S511, providing a first substrate;

[0062] S512, such as Figure 1 As shown, the first substrate is vertically inserted from the oil phase into the lower aqueous phase. Then, the end of the first substrate inserted into the aqueous phase is tilted upward until it leaves the upper surface of the oil phase, and the liquid metal self-assembled film at the oil-water interface is transferred to the first substrate (i.e., the film is taken by the vertical tilting method). The liquid metal self-assembled film is then prepared on the first substrate.

[0063] In this embodiment, the first substrate includes a hydrophobic substrate and a hydrophilic substrate. The hydrophobic substrate includes, but is not limited to, hydrophobic glass, oil paper, etc., and also includes flexible substrates such as polydimethylsiloxane (PDMS) and thermoplastic copolyester (Ecoflex). The hydrophilic substrate includes, but is not limited to, hydrophilic glass, metal substrates (e.g., copper substrates). In one embodiment, the method for preparing the liquid metal self-assembled thin film further includes the following steps:

[0064] S521, Provide a flexible second substrate with a preset pattern;

[0065] S522. The flexible second substrate is vertically inserted from the oil phase into the lower aqueous phase. Then, the end of the flexible second substrate inserted into the aqueous phase is tilted upward and lifted until it leaves the upper surface of the oil phase. The liquid metal self-assembled film at the oil-water interface is transferred to the flexible second substrate. A patterned liquid metal self-assembled film is formed on the flexible second substrate. Then, ethanol is sprayed onto the patterned liquid metal self-assembled film.

[0066] S523, such as Figure 2 As shown in (a), a metal transfer substrate 3 and a flexible second substrate 1 with a patterned liquid metal self-assembled film 2 on the surface obtained in step S522 are provided.

[0067] S524. Heat the metal transfer substrate 3, such as... Figure 2 As shown in (b), the flexible second substrate containing the patterned liquid metal self-assembled film is disposed on the heated metal transfer substrate, wherein the patterned liquid metal self-assembled film is disposed in conjunction with the metal transfer substrate;

[0068] S525, such as Figure 2 As shown in (b), the flexible second substrate 1 is pressed vertically on the side opposite to the metal transfer substrate 3, as shown in (b). Figure 2 As shown in (c), the patterned liquid metal self-assembled film 2 is transferred onto the metal transfer substrate 3, and the patterned liquid metal self-assembled film 2 is prepared on the metal transfer substrate 3.

[0069] In this embodiment, since ethanol has a low surface tension, spraying ethanol onto the patterned liquid metal self-assembled film allows the ethanol to bridge the liquid metal self-assembled film at the interface between the liquid metal self-assembled film and the flexible second substrate, thereby reducing the van der Waals force (also known as attraction force) between the patterned liquid metal self-assembled film and the flexible second substrate. By heating the metal transfer substrate and applying vertical pressure, the patterned liquid metal self-assembled film and the heated metal transfer substrate are brought into full contact, further reducing the van der Waals force between the patterned liquid metal self-assembled film and the flexible second substrate. This increases the van der Waals attraction force between the metal transfer substrate and the patterned liquid metal self-assembled film, transferring the patterned liquid metal self-assembled film onto the metal transfer substrate.

[0070] In one embodiment, the flexible second substrate may be selected from flexible substrates such as PDMS and Ecoflex; the metal transfer substrate may be selected from a copper substrate.

[0071] This invention also provides a liquid metal self-assembled thin film, which is prepared using the preparation method described above in this invention.

[0072] In one embodiment, the thickness of the liquid metal self-assembled film is 300–1000 nm (e.g., 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1000 nm). Its surfactant content is 0.6–0.9 wt%, and it possesses high modulus (up to 690 GPa) and strong wettability, while also exhibiting self-healing capabilities.

[0073] This invention also provides an application of liquid metal self-assembled thin films in the field of flexible electronics. Specifically, the liquid metal self-assembled thin film can be sintered with the surface of a flexible material to form stretchable electronic wire pathways for application.

[0074] This invention also provides an application of a liquid metal self-assembled thin film in the field of thermally conductive materials. Specifically, the liquid metal self-assembled thin film can be combined with an elastomer to form a large-area universally adherent thermally conductive material for application.

[0075] This invention also provides an application of a liquid metal self-assembled thin film in the battery field. Specifically, a liquid metal self-assembled thin film can be coated onto the surface of garnet to improve lithium adhesion, thereby enhancing battery performance.

[0076] The following detailed description uses specific examples.

[0077] In the examples below, the SEM used was purchased from Thermo Fisher Scientific, model APREO S.

[0078] Example 1

[0079] Add 11.6 mg of hexanoic acid to 20 mL of methyl methacrylate, vortex for 5 min to obtain a 5 mmol / L hexanoic acid solution, and store it in a refrigerator protected from light.

[0080] Weigh 300 mg of liquid metal (gallium indium tin alloy) and add it to 9 mL of ultrapure water. Then add 1 mL of hexanoic acid solution and sonicate at 0 °C for 30 min to obtain a liquid metal self-assembly seed solution.

[0081] Place 20 mL of ultrapure water in a 9 cm diameter circular glass dish, mix 10 mL of liquid metal self-assembly seed solution with the ultrapure water in the glass dish, shake for 5 seconds, and a hexanoic acid-modified liquid metal self-assembly film can be obtained at the oil-water-liquid interface.

[0082] Example 2

[0083] Add 28.2 mg of octadecenoic acid to 20 mL of methyl methacrylate, vortex for 5 min to obtain a 5 mmol / L octadecenoic acid solution, and store it in a refrigerator away from light.

[0084] Weigh 300 mg of liquid metal (gallium indium tin alloy) and add it to 9 mL of ultrapure water. Then add 1 mL of octadecenoic acid solution and sonicate at 0 °C for 30 min to obtain a liquid metal self-assembly seed solution.

[0085] Place 20 mL of ultrapure water in a 9 cm diameter circular glass dish, mix 10 mL of liquid metal self-assembly seed solution with the ultrapure water in the glass dish, shake for 5 seconds, and an octadecenoic acid liquid metal self-assembly film can be obtained at the oil-water-liquid interface.

[0086] test:

[0087] (1) The laser confocal Raman spectra of the two liquid metal self-assembled thin films prepared in Examples 1 and 2 are as follows: Figure 3 As shown. Figure 3The upper spectral line represents the laser confocal Raman spectrum of the hexanoic acid-modified liquid metal self-assembled film prepared in Example 1, while the lower spectral line represents the laser confocal Raman spectrum of the octadecenoic acid-modified liquid metal self-assembled film prepared in Example 2. Comparing the two spectra reveals that the characteristic peak of Ga2O3 is the characteristic peak of the gallium indium tin alloy oxide layer. The peak positions and areas of the other characteristic peaks show significant changes, indicating that both surfactants can effectively graft onto liquid metal nanoparticles. Furthermore, different surfactants will produce different Raman spectra for the liquid metal self-assembled films, allowing for further differentiation of different liquid metal self-assembled films. Additionally, at 2912.6 cm⁻¹... -1 The Raman peak intensity of the octadecenoic acid-modified liquid metal self-assembled film was stronger than that of the hexanoic acid-modified liquid metal self-assembled film, indicating that using surfactants with longer alkane chains resulted in a higher Raman peak intensity at 2912.6 cm⁻¹. -1 The stronger the Raman peak at a given location.

[0088] (2) The octadecenoic acid-modified liquid metal self-assembled film prepared in Example 2 was sampled on a glass slide and then magnified 50,000 times using a high-resolution scanning electron microscope (SEM) as shown below. Figure 4 As shown. From Figure 4 As can be seen, the surface of the octadecenoic acid-modified liquid metal self-assembled film is dense and smooth, without large cracks or pores. This indicates that the interaction between the surfactants grafted onto the surface of the liquid metal nanoparticles makes the film dense and stable, and the advantage of liquid-liquid interface self-assembly also makes the liquid metal self-assembled film smoother.

[0089] (3) The self-healing properties of octadecenoic acid-modified liquid metal self-assembled films were tested.

[0090] The liquid metal self-assembly seed solution from Example 2 was mixed with ultrapure water at a volume ratio of 1:9. After shaking, a liquid metal self-assembly film could be obtained at the oil-water interface in 5 seconds.

[0091] Clean the 18×18mm glass slide with ethanol under ultrasonication for 20 minutes, and then dry it in an oven for 10 minutes. Use the dried glass slide to take a film from the same position of the liquid metal self-assembled film obtained in the above steps using the vertical tilt film taking method (see above for details).

[0092] After taking multiple films from the same location, the octadecenoic acid-modified liquid metal self-assembled film at the oil-water interface can complete the healing of defects in 20 seconds.

[0093] Figure 5To test the self-healing properties of the octadecenoic acid-modified liquid metal self-assembled film prepared by mixing the liquid metal self-assembly seed solution from Example 2 with ultrapure water at a volume ratio of 1:9, the results show the self-healing behavior of the octadecenoic acid-modified liquid metal self-assembled film after multiple film removals from the same location on a glass slide. Image (a) shows the result of the first film removal, image (b) shows the result of the first self-healing, image (c) shows the result of the third film removal, and image (d) shows the result of the third self-healing. Figure 5 As can be seen, the octadecenoic acid-modified liquid metal self-assembled film exhibits rapid self-healing behavior at defects, similar to human wound healing, healing from the edge of the defect towards the center without the need for external force.

[0094] Example 3

[0095] This embodiment illustrates that the liquid metal self-assembled ultrathin film obtained by the method of the present invention can be transferred to different substrates.

[0096] Sylgard 184 silicone base and Sylgard curing agent were mixed at a mass ratio of 10:1 and stirred for 3 minutes to ensure uniform mixing. Then, the mixture was defoamed under vacuum for 30 minutes. After spin coating onto a patterned mold, it was cured to obtain a flexible patterned PDMS substrate.

[0097] Mix Ecoflex 00-30 PART A and PART B in a 1:1 mass ratio, stir for 3 minutes until homogeneous, then defoam under vacuum for 30 minutes. Spin coat onto a patterned mold and cure to obtain a flexible patterned Ecoflex substrate.

[0098] The flexible patterned PDMS substrate and the flexible patterned Ecoflex substrate were cut into 5×5cm squares. Then, the liquid metal self-assembled film obtained at the oil-water interface in Example 1 was taken by the vertical tilting method (see above). The liquid metal self-assembled film was completely immersed in the patterned surface of the two flexible substrates.

[0099] As can be seen from Example 3, the liquid metal self-assembled ultrathin film prepared by the present invention can be transferred to different substrates.

[0100] Example 4

[0101] Liquid metal self-assembled films have different wetting capabilities for different substrates. By changing the wetting ability of the liquid metal self-assembled film on the flexible substrate, the pattern of the flexible substrate can be transferred to any substrate.

[0102] After drying the liquid metal self-assembled film on the flexible patterned PDMS substrate after film removal in Example 3, an appropriate amount of anhydrous ethanol was sprayed onto the surface, thereby reducing the van der Waals force between the liquid metal self-assembled film and the flexible patterned PDMS substrate.

[0103] A copper substrate is heated (to increase the attraction between the copper substrate and the liquid metal self-assembled film), and then the pattern of the flexible patterned PDMS substrate is brought into full contact with the copper substrate by a vertical pressure method, and maintained for 3 minutes (that is, the flexible patterned PDMS substrate containing the liquid metal self-assembled film is stacked on the copper transfer substrate, wherein the liquid metal self-assembled film is adhered to the copper transfer substrate, and then the side of the flexible patterned PDMS substrate away from the copper substrate is pressed vertically to bring the pattern of the flexible patterned PDMS substrate into full contact with the copper transfer substrate, and maintained for 3 minutes), thus obtaining a copper substrate with a liquid metal self-assembled film pattern.

[0104] Figure 6 This image shows the result of transferring the liquid metal self-assembled thin film from the flexible patterned PDMS substrate after film removal in Example 3 onto a copper substrate. From... Figure 6 As can be seen, liquid metal self-assembled films on flexible patterned PDMS substrates can be effectively transferred onto copper substrates.

[0105] In this embodiment, by spraying anhydrous ethanol and heating the copper substrate, the attractive force of the flexible patterned PDMS substrate on the liquid metal self-assembled film is less than that on the copper substrate. Ultimately, the liquid metal self-assembled film can be well transferred onto the copper substrate in a patterned manner, thus achieving patterned transfer.

[0106] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a self-assembled liquid metal thin film, characterized in that, Including the following steps: A surfactant solution and a liquid metal are provided, wherein the solvent of the surfactant solution is an organic solvent with a density less than that of water and immiscible with water; The liquid metal is added to water to obtain a liquid metal solution; The surfactant solution is added to the liquid metal solution and ultrasonically mixed to graft the surfactant onto the surface of the liquid metal nanoparticles, resulting in liquid metal nanoparticles with surfactant-modified surfaces, and thus a liquid metal self-assembly seed solution containing surfactant-modified liquid metal nanoparticles. After mixing the liquid metal self-assembly seed solution containing surfactant-modified liquid metal nanoparticles with water, the lower layer is an aqueous phase and the upper layer is an oil phase. At the oil-water interface, the surfactant-modified liquid metal nanoparticles attract each other through non-covalent forces between surfactants to form a dense film structure, thus obtaining the liquid metal self-assembly film. The surfactant is selected from surfactants containing a single carboxyl group.

2. The preparation method according to claim 1, characterized in that, The organic solvent is selected from at least one of methyl methacrylate, toluene, and n-hexane; And / or, the surfactant containing a single carboxyl group is selected from at least one of acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptanoic acid, octadecanoic acid, nonenoic acid, icosanoic acid, butenoic acid, pentenoic acid, hexenoic acid, heptenoic acid, octadecanoic acid, nonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid, heptanoic acid, heptanoic acid, octadecenoic acid, nonadecenoic acid, and icosanoic acid; And / or, the liquid metal is selected from gallium indium tin alloy and eutectic gallium indium.

3. The preparation method according to claim 1, characterized in that, In the surfactant solution, the concentration of the surfactant is 0.5~9 mmol / L; And / or, in the liquid metal solution, the concentration of the liquid metal is 10~400 mg / mL.

4. The preparation method according to claim 1, characterized in that, The volume ratio of the surfactant solution to the liquid metal solution is (1-5):(9-5).

5. The preparation method according to claim 1, characterized in that, The ultrasonic mixing time is 10~120 min, and the ultrasonic mixing temperature is 0~1℃.

6. The preparation method according to claim 1, characterized in that, In the step of mixing the liquid metal self-assembly seed solution with water, the volume ratio of the liquid metal self-assembly seed solution to the water is 10:(20~100).

7. The preparation method according to any one of claims 1-6, characterized in that, The method for preparing the liquid metal self-assembled thin film further includes the following steps: Provide the first base; The first substrate is vertically inserted from the oil phase into the lower aqueous phase. Then, the end of the first substrate inserted into the aqueous phase is tilted upward and lifted until it leaves the upper surface of the oil phase. The liquid metal self-assembled film at the oil-water interface is transferred onto the first substrate, and the liquid metal self-assembled film is prepared on the first substrate.

8. The preparation method according to any one of claims 1-6, characterized in that, The method for preparing the liquid metal self-assembled thin film further includes the following steps: A flexible second substrate with a preset pattern is provided; the flexible second substrate is vertically inserted from the oil phase into the lower aqueous phase, and then the end of the flexible second substrate inserted into the aqueous phase is tilted upward until it leaves the upper surface of the oil phase, and the liquid metal self-assembled film at the oil-water interface is transferred onto the flexible second substrate, forming a patterned liquid metal self-assembled film on the flexible second substrate, and then ethanol is sprayed onto the patterned liquid metal self-assembled film; Provides metal transfer substrate; The metal transfer substrate is heated, and a flexible second substrate containing a patterned liquid metal self-assembled film is placed on the heated metal transfer substrate, wherein the patterned liquid metal self-assembled film is attached to the metal transfer substrate. The patterned liquid metal self-assembled film is transferred onto the metal transfer substrate by pressing the flexible second substrate vertically on the side opposite to the metal transfer substrate, thereby preparing the patterned liquid metal self-assembled film on the metal transfer substrate.

9. A self-assembled liquid metal thin film, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

10. The liquid metal self-assembled thin film according to claim 9, characterized in that, The thickness of the liquid metal self-assembled film is 300~1000nm.

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