Size-controllable gallium-based liquid metal droplet, preparation method and composite material

Abstract

The invention provides a gallium-based liquid metal droplet with a controllable size, a preparation method of the gallium-based liquid metal droplet and a composite material, and belongs to the technical field of liquid metal preparation. The preparation method comprises the following steps: melting solid pure gallium to obtain gallium-based liquid metal; condensing the gallium-based liquid metal in a capillary tube, and removing the capillary tube to obtain a gallium-based liquid metal wire; according to the size of the required gallium-based liquid metal droplet, cutting a gallium-based liquid metal wire section with a corresponding length; and the gallium-based liquid metal wire sections are placed on a substrate, the substrate with the gallium-based liquid metal wire sections is subjected to heating and freezing solidification treatment, and the gallium-based liquid metal liquid drops are obtained. The length of the gallium-based liquid metal wire section is determined through the size of the liquid drop, the gallium-based liquid metal liquid drop with the needed size is obtained through melting and freezing solidification treatment, no complex treatment process and equipment are needed, the method is simple and easy to implement, the cost is low, other organic reagents do not need to be added, and large-batch production can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid metal preparation, and in particular relates to a size-controllable gallium-based liquid metal droplet, a preparation method, and a composite material. Background Art

[0002] Gallium-based liquid metal is liquid at room temperature, and has excellent properties such as strong electrical conductivity (3×106 / Ω·m), high thermal conductivity (×60 times that of water), high boiling point (>2400℃), safety, non-toxicity, and high efficiency and recyclability. It has broad application prospects in important fields such as flexible electronics, electromagnetic shielding, soft robots, micromotors, thermal management, and biomedicine. As a functional material or filler, it can be more beneficial to combine with flexible media to exert these characteristics, and has obvious comprehensive performance advantages over media such as ion gels, hydrogels, and rigid conductive fillers.

[0003] Gallium-based liquid metals are usually in a flowable droplet state during the preparation and application process. In most applications, liquid metals need to exist in the form of droplets of a certain size. However, due to its own high surface tension, liquid metals are not easily dispersed into small droplets by machinery, and the size of the prepared droplets is even more difficult to accurately control. However, the size of gallium-based metal droplets has an important impact on the sensing, driving, and field response speed / amplitude of materials and devices. In addition, the size of gallium-based metal droplets is also significantly dependent on mechanics, electricity, heat, and supercooling. Therefore, in many key areas, the size and shape of gallium-based particles (droplets) need to be precisely controlled.

[0004] The preparation process of gallium-based particles (droplets) mainly includes mechanical stirring, injection, solution boiling and vapor deposition. Among them, when the mechanical stirring method is used, the shear force generated by the high-speed rotation of the shear probe is used to break up large pieces of liquid metal, and the size of the prepared droplets is not uniform, and the droplet size cannot be controlled. When the ultrasonic dispersion technology is used, the liquid metal is converted into micro-nano particles by the ultrasonic cavitation principle, and a surfactant needs to be added during the ultrasonic treatment process. There is a problem of difficulty in effectively removing the active agent in the subsequent process, and the surface of the obtained droplets is severely oxidized and difficult to extract. Secondly, when the injection method is used, liquid metal is injected into a solution containing a surfactant to generate liquid particles. The diameter of the metal particles can be adjusted by adjusting the needle aperture and the injection speed. The size of the prepared droplets is not uniform and the cost is high. Furthermore, when the solution boiling method is used, the high-energy bubbles generated by the solution boiling process collide with the liquid metal.

[0005] Dispersed into small droplets, the droplet size of this method is difficult to control, and subsequent droplet extraction is difficult; in addition, when using the vapor deposition method, high-temperature vapor diffusion is used to form a stable liquid metal nucleation and growth on a cold target substrate. The general particle size is 25nm to 100nm, but the high boiling point and high vapor pressure of gallium-based alloys seriously hinder the application of physical vapor deposition and cannot be mass-produced. Summary of the invention

[0006] The present disclosure aims to at least solve the problems existing in the prior art, such as the non-uniform size of droplets, the inability to control the size of droplets, the great difficulty in subsequent extraction, transportation and manipulation of droplets, the need to add other chemical solvents during the preparation process, which easily causes environmental pollution and insecurity, high cost and the inability to achieve mass production, and provides a gallium-based liquid metal droplet with controllable size, a preparation method and a composite material.

[0007] In one aspect of the present disclosure, a method for preparing gallium-based liquid metal droplets with controllable size is provided, the preparation method comprising:

[0008] Melting solid pure gallium to obtain gallium-based liquid metal;

[0009] Gallium-based liquid metal is placed in a capillary for condensation, and the capillary is removed to obtain a gallium-based liquid metal wire;

[0010] According to the required size of the gallium-based liquid metal droplet, cutting the gallium-based liquid metal wire segment of corresponding length;

[0011] The gallium-based liquid metal wire segment is placed on a substrate, and the substrate with the gallium-based liquid metal wire segment is heated and frozen to solidify to obtain gallium-based liquid metal droplets.

[0012] Optionally, the length of the gallium-based liquid metal wire segment is determined by the following formula:

[0013]

[0014] h is the length of the gallium-based liquid metal wire segment, d 球 is the diameter of the gallium-based liquid metal droplet, d 柱 is the inner diameter of the capillary.

[0015] Optionally, the diameter of the gallium-based liquid metal droplet ranges from 0.246 mm to 4 mm.

[0016] Optionally, the gallium-based liquid metal is placed in the capillary tube and condensed at a temperature of -20°C to -15°C for a time of 8 hours to 12 hours.

[0017] Optionally, the temperature at which the substrate having the gallium-based liquid metal wire segment is heated is 48° C. to 53° C.

[0018] Optionally, the substrate having the gallium-based liquid metal wire segment is subjected to a freezing solidification treatment at a temperature of -13°C to -8°C and a time of 0.5h to 1.5h.

[0019] Optionally, the capillary is made of polytetrafluoroethylene.

[0020] Optionally, the substrate is printing paper.

[0021] Another aspect of the present disclosure provides a size-controllable gallium-based liquid metal droplet, which is prepared by the preparation method described above.

[0022] Another aspect of the present disclosure provides a composite material, which includes a stacked silicone base film, a plurality of regularly arranged gallium-based liquid metal droplets, and a silicone coating; wherein the plurality of gallium-based liquid metal droplets are the gallium-based liquid metal droplets described above.

[0023] The present disclosure provides a size-controllable gallium-based liquid metal droplet and a preparation method and composite material thereof. The preparation method includes: melting solid pure gallium to obtain gallium-based liquid metal; placing the gallium-based liquid metal in a capillary for condensation, removing the capillary to obtain gallium-based liquid metal wire; cutting gallium-based liquid metal wire segments of corresponding lengths according to the required size of the gallium-based liquid metal droplet; placing the gallium-based liquid metal wire segments on a substrate, and heating and freezing and solidifying the substrate with the gallium-based liquid metal wire segments to obtain gallium-based liquid metal droplets. The preparation process can control the size of the gallium-based liquid metal droplet, and only needs to determine the length of the gallium-based liquid metal wire segment. Gallium-based liquid metal droplets of the required size can be obtained through melting and freezing and solidification treatment, and the size of the gallium-based liquid metal droplet can be controlled. It does not require complicated processing procedures and equipment, is simple and easy to operate, has low cost, and does not require the addition of other organic reagents, and subsequent extraction, transportation and manipulation processes, and can achieve mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flowchart of a method for preparing gallium-based liquid metal droplets according to a specific embodiment of the present disclosure;

[0025] Figure 2 It is a flow chart of a method for preparing gallium-based liquid metal droplets according to a specific embodiment of the present disclosure;

[0026] Figure 3 It is a schematic flow chart of a method for preparing gallium-based liquid metal droplets according to a specific embodiment of the present disclosure;

[0027] Figure 4 A force diagram of a gallium-based liquid metal droplet according to a specific embodiment of the present disclosure;

[0028] Figure 5The contact angle test results of gallium-based liquid metal droplets on different substrates of Example 1 and Comparative Examples 1-4 of the present disclosure;

[0029] Figure 6 is a schematic diagram of a gallium-based liquid metal droplet according to Example 1 of the present disclosure;

[0030] Figure 7 is a particle size distribution diagram of gallium-based liquid metal droplets of Example 1 of the present disclosure;

[0031] Figure 8 is a compressive stress-strain curve of a gallium-based liquid metal droplet according to Example 1 of the present disclosure;

[0032] Fig. 9 is a schematic diagram of a gallium-based liquid metal droplet according to Example 2 of the present disclosure;

[0033] Fig.10 Schematic diagram of the composite material of Example 4 of the present disclosure. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solution of the present disclosure, the present disclosure is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0035] like Figures 1 to 3 As shown, in one aspect of the present disclosure, a method S100 for preparing gallium-based liquid metal droplets with controllable size is provided, which specifically includes the following steps S110 to S140:

[0036] S110, melting solid pure gallium to obtain gallium-based liquid metal.

[0037] Specifically, pure gallium (melting point: 29.8° C.) is melted by a water bath method, and its melting temperature should be at least 29.8° C., and the melted liquid metal is poured into a sample bottle.

[0038] S120, placing the gallium-based liquid metal in a capillary for condensation, and removing the capillary to obtain a gallium-based liquid metal wire.

[0039] Specifically, select a suitable capillary, immerse one end of the capillary completely in the liquid metal sample bottle in step S110, and connect the other end to a needle and a syringe of corresponding size to ensure the airtightness of both ends of the pipeline. Slowly pull the needle outward, and the flow rate in the pipeline is approximately controlled at 0.1m / s. The liquid metal will flow freely in the capillary. Wait for the liquid metal to flow completely to the syringe. First, pull out the capillary in the sample bottle. After pulling it out, a layer of gallium oxide will naturally form to ensure its airtightness. Then unscrew the needle from the threaded syringe. At this time, you need to use tweezers to place the capillary in a refrigerator for freezing. First, you need to wrap both ends of the tweezers with soft cloth or a paper towel with low friction, gently clamp the capillary, and put it in the refrigerator to freeze until the liquid metal is completely solidified. Afterwards, use a paper cutter to cut the polytetrafluoroethylene capillary in the middle, clamp the proximal ends of the capillaries with tweezers, and slowly pull both sides apart at the same time, peeling off without destroying the solidified liquid metal in the middle. After peeling, the liquid metal is in the form of filaments with a metallic luster on the surface.

[0040] In some preferred embodiments, the capillary containing gallium-based liquid metal is condensed in a refrigerator at a temperature of -20°C to -15°C, and the time is 8h to 12h. For example, -20°C, -18°C, -16°C, -15°C, etc., and the time is 8h, 9h, 10h, 11h, 12h, etc.

[0041] It should be noted that the selection of the material, length and inner diameter of the capillary is crucial. The appropriate material is conducive to the flow of liquid metal. For example, polytetrafluoroethylene (including PTFE or Teflon) can be preferred. The dynamic friction coefficient of this material is 0.06, which makes it difficult for liquid metal to adhere to the inner wall of its pipe, and will not encounter the problem of small flux blockage in the microfluidic process, and can flow smoothly in the pipe. In addition, the tensile strength of the material is within 20 to 35 MPa, and the stretching ratio is within the range of 200% to 400%, which can maintain the integrity of the pipe under curvature deformation. The surface of liquid metal is very easy to oxidize in the natural state, and a layer of Ga2O3 film with a thickness of 1 to 3 nm will be formed. The destructive strength of the gallium oxide is about 200 to 600 mN / m. The length of the polytetrafluoroethylene capillary is preferably about 5 m and the inner diameter is preferably 0.3 mm. Of course, the length and inner diameter of the capillary can be adjusted according to actual needs, and there is no specific limitation on this.

[0042] S130, cutting gallium-based liquid metal wire segments of corresponding lengths according to the required size of gallium-based liquid metal droplets.

[0043] It should be noted that, based on the principle of mass (volume) invariance, this embodiment can accurately calculate parameters such as the length of the liquid gallium-based metal wire segment, and then accurately prepare gallium-based liquid metal particles of the required size, achieve more precise size control, and provide liquid metal particles of suitable specifications for related applications.

[0044] Specifically, the principle of mass (volume) invariance is as follows:

[0045] Volume of a sphere:

[0046] The volume of the cylinder:

[0047] According to the volume invariance principle V 球 =V 柱 , the following formula can be obtained to determine the length of the gallium-based liquid metal wire segment:

[0048]

[0049] Where h is the length of the gallium-based liquid metal wire segment, d 球 is the diameter of the gallium-based liquid metal droplet, d 柱 is the inner diameter of the capillary.

[0050] It should be understood that based on the above formula, the length of the gallium-based liquid metal wire segment to be cut can be determined according to the diameter of the gallium-based liquid metal wire segment and the diameter of the gallium-based liquid metal droplet to be prepared, and then the gallium-based liquid metal droplets of corresponding sizes can be obtained by subsequent processing of the gallium-based liquid metal wire segment of this length, thereby achieving controllable size of the gallium-based liquid metal droplets.

[0051] It should be noted that the diameter of the gallium-based liquid metal wire segment is related to the inner diameter of the capillary. Therefore, the size range of the gallium-based liquid metal droplet can be determined in combination with the inner diameter of the existing capillary. For example, the thinnest capillary currently available on the market has an inner diameter of d 柱 =0.1mm, if h>1mm is required, the minimum gallium-based liquid metal droplet size d can be calculated 球 =246μm. For another example, the inner diameter of the thickest capillary on the market is d 柱 =4.0mm, if h>4mm is required, the maximum droplet size that can be prepared is calculated to be d 球 =4580 μm, thus it can be determined that the size range of the prepared gallium-based liquid metal particles (droplets) is 246 μm to 4580 μm. Of course, in other preferred embodiments, gallium-based liquid metal particles (droplets) with other diameter ranges can also be prepared according to capillaries of other sizes, and this is not specifically limited.

[0052] It should also be noted that there is a critical size for gallium-based liquid metal droplets. When the size is below this critical size, surface tension plays a dominant role, making the droplets spherical. When the size is above this critical size, the gravity of the droplets plays a dominant role. Therefore, the size of the gallium-based liquid metal droplets needs to be further combined with the critical size. The force on the droplets is as follows: Figure 4As shown, the critical size can be defined as

[0053] The droplet gravity and surface contraction force are:

[0054]

[0055] Where P represents the gravity of the gallium-based liquid metal droplet, and ρ represents the density of the gallium-based liquid metal droplet, which is 6.45×10 3 , V represents the volume of the gallium-based liquid metal droplet, g is 10, γ represents the surface contraction force of the gallium-based liquid metal droplet, and r represents the surface tension coefficient of the gallium-based liquid metal droplet, which is 700×10 -3 .

[0056] Based on P = γ, the critical size of the droplet can be obtained It can be determined that as long as the diameter of the gallium-based liquid metal droplet is less than 4 mm, the gallium-based droplet is basically spherical. In summary, based on the current capillary size, the diameter range of the gallium-based liquid metal droplet in this embodiment is preferably 0.246 mm to 4 mm, for example, 0.246 mm, 0.3 mm, 0.5 mm, 0.7 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 4 mm, etc.

[0057] S140, placing the gallium-based liquid metal wire segment on a substrate, and heating and freezing and solidifying the substrate with the gallium-based liquid metal wire segment to obtain gallium-based liquid metal droplets.

[0058] Specifically, the length of the gallium-based liquid metal wire segment is determined based on the above formula, and it is placed on a substrate after cutting, and then the substrate is placed on a heating plate, and the constant temperature is set to 48°C to 53°C, for example, preferably 50°C. After the gallium-based liquid metal wire segment is melted and polymerized, it is very easy to form a spherical shape due to the high surface tension of the liquid metal of 700mN / m. However, it should be noted that after the droplet size is larger than the critical size, the droplet will be in a spreading state because its own gravity exceeds the surface tension.

[0059] Furthermore, the gallium-based droplets that have aggregated into spherical shapes are placed in a refrigerator together with the attached substrate, the temperature is set to -13°C to -8°C, and they are taken out after 0.5h to 1.5h, and liquid metal solid spheres can be successfully obtained.

[0060] In some preferred embodiments, the freezing temperature is preferably -13°C, -11°C, -10°C, -8°C, etc., and the freezing time is 0.5h, 1h, 1.5h, etc.

[0061] In other preferred embodiments, the substrate is printing paper.

[0062] The preparation process disclosed in the present invention can control the size of gallium-based liquid metal droplets, and determine the length of the gallium-based liquid metal wire segment by the size of the droplets. The gallium-based liquid metal wire segment can be melted and frozen to obtain gallium-based liquid metal droplets of a desired size. It does not require complicated processing procedures and equipment, is simple and easy, has low cost, and does not require the addition of other organic reagents, and can achieve mass production.

[0063] Another aspect of the present disclosure provides a size-controllable gallium-based liquid metal droplet, which is prepared by the preparation method described above. Please refer to the above description for the specific preparation process, which will not be repeated here.

[0064] Another aspect of the present disclosure provides a composite material, which includes a stacked silicone base film, a plurality of gallium-based liquid metal droplets, and a silicone cover film; wherein the plurality of gallium-based liquid metal droplets are regularly arranged.

[0065] It should be noted that a certain number of gallium-based liquid metal droplets can be prepared based on the preparation process given in the previous article. Multiple gallium-based liquid metal droplets can be arranged in a certain regular pattern in the silicone base film and the silicone covering film. According to the needs of mechanical design and physical analysis, a composite material with a special structure can be prepared to effectively improve the material's mechanical deformation response capability and ability to prevent damage and destruction.

[0066] It should be further explained that the present embodiment does not specifically limit the arrangement of the plurality of gallium-based liquid metal droplets, for example, regular structures such as regular hexagons and honeycombs.

[0067] This embodiment can independently manipulate and conveniently transport gallium-based liquid metal droplets to achieve special functions such as material and device movement, sensing, and solid-liquid phase change, providing strong technical support in device transportation, pattern design, and integrated assembly. By adjusting the size of gallium-based liquid metal droplets, the composite material structure with special microstructure and functional requirements can be precisely controlled and effectively applied to applications such as actuators, soft robots, and sensors. The above preparation technology provides necessary support for the derivative development of key fields such as basic physics, mechanical manufacturing, artificial intelligence, and flexible drives.

[0068] The preparation method of gallium-based liquid metal droplets will be further described below in conjunction with specific examples:

[0069] Example 1

[0070] like Figure 2 and Figure 3 As shown, the method for preparing gallium-based liquid metal droplets in this example includes the following steps:

[0071] S1. Heat and melt 99.99% pure solid gallium in a water bath to form liquid metal, and pour it into a 10 mL sample bottle.

[0072] S2. Select a polytetrafluoroethylene capillary with a length of about 5m and an inner diameter of 0.3mm. Completely immerse one end of the capillary in the liquid metal sample bottle, and connect the other end to a needle and syringe of corresponding size to ensure the airtightness of both ends of the pipe. Slowly pull the needle outward by hand. The flow rate in the pipe is approximately controlled at 0.1m / s. The liquid metal will flow freely in the capillary. Wait for the gallium-based liquid metal to flow completely to the syringe. Pull out the capillary in the sample bottle first. After pulling it out, a layer of gallium oxide will naturally form to ensure its airtightness. Unscrew the needle and the threaded syringe, wrap soft cloth or low-friction paper towels at both ends of the tweezers, gently clamp the capillary, put it in the refrigerator, and freeze it at -18℃ for 10 hours. At this time, the liquid metal is completely solidified. Use a paper cutter to cut the polytetrafluoroethylene capillary in the middle, clamp the proximal ends of the capillaries with tweezers, and slowly pull the two sides apart at the same time, peeling off without destroying the solidified liquid metal in the middle. After peeling, the liquid metal is in the form of filaments with a metallic luster on the surface.

[0073] S3, prepare gallium-based liquid metal droplets with a diameter of 1 mm, d 球 =1mm, the inner diameter of the capillary is 0.3mm, d 柱 =0.3mm, based on the formula, the length of the gallium-based liquid metal wire segment is determined to be h=7.6mm, and the gallium-based liquid metal wire is cut into wire segments with a length of 7.6mm.

[0074] S4. Place the gallium-based liquid metal wire segment on the printing paper, and then place it on the heating plate, set the constant temperature to 50°C, and after the metal wire segment melts and polymerizes, it is very easy to form a spherical shape due to the high surface tension of the liquid metal of 700mN / m. Place the spherical gallium-based droplets together with the attached printing paper in a refrigerator, set the temperature to -10°C, and take them out after 1 hour. You can successfully obtain a small ball of liquid metal droplets, and the size of the gallium-based liquid metal droplets is 1mm.

[0075] Furthermore, as shown in Table 1 and Figure 5 As shown, when printing paper is used as the substrate, the contact angle of the formed gallium-based liquid metal droplets on the printing paper is 136.25°, which indicates that during the heating and solidification process, the gallium-based liquid metal droplets can be stably placed on the printing paper.

[0076] Furthermore, the diameters of 100 gallium-based liquid metal droplets were measured three times using a vernier caliper / micrometer screw, and the average value was calculated. Calculate the standard deviation and analyze the particle size consistency through particle size distribution statistics. Figure 6 and Figure 7As shown, the particle size distribution conforms to the normal distribution, and the droplet size of the gallium-based liquid metal is about 1.05 mm.

[0077] Furthermore, if Figure 8 As shown, the stress of the gallium-based liquid metal droplet in this embodiment is 35 MPa.

[0078] Example 2

[0079] The preparation process of this example is the same as that of Example 1, except that the size of the gallium-based liquid metal droplet is changed to 2 mm. At this time, in step S3, it is determined that the gallium-based liquid metal wire segment to be cut is cut to a length of 59.26 mm.

[0080] like Fig. 9 As shown, the size of the gallium-based liquid metal droplets obtained in this embodiment is about 2 mm.

[0081] Example 3

[0082] The preparation process of this example is the same as that of Example 1, except that the size of the gallium-based liquid metal droplet is changed to 0.5 mm. At this time, in step S3, it is determined that the gallium-based liquid metal wire segment to be cut is cut to a length of 0.93 mm.

[0083] Example 4

[0084] The gallium-based liquid metal droplets obtained in Example 1 are formed into a composite material, such as Fig.10 As shown, the composite material 200 includes a stacked silicone base film 210, a plurality of regularly distributed gallium-based liquid metal droplets 220, and a silicone cover film 230, wherein the plurality of gallium-based liquid metal droplets are arranged in a honeycomb shape.

[0085] Comparative Example 1

[0086] The preparation process of this example is the same as that of Example 1, except that the substrate in step S4 is changed to a steel plate, and the gallium-based liquid metal wire segment is placed on the steel plate, as shown in Tables 1 and Figure 5 As shown, the contact angle of the formed gallium-based liquid metal droplet on the steel plate is 131°.

[0087] Comparative Example 2

[0088] The preparation process of this example is the same as that of Example 1, except that the substrate in step S4 is changed to a steel plate, and the gallium-based liquid metal wire segment is placed on the PDMS, as shown in Tables 1 and Figure 5 As shown, the contact angle of the formed gallium-based liquid metal droplet on the PDMS is 113.97°.

[0089] Comparative Example 3

[0090] The preparation process of this example is the same as that of Example 1, except that the substrate in step S4 is changed to a steel plate, and the gallium-based liquid metal wire segment is placed on Ecoflex, as shown in Table 1 and Figure 5 As shown, the contact angle of the formed gallium-based liquid metal droplet on the Ecoflex is 91.54°.

[0091] Comparative Example 4

[0092] The preparation process of this example is the same as that of Example 1, except that the substrate in step S4 is changed to a steel plate, and the gallium-based liquid metal wire segment is placed on polyethylene, as shown in Tables 1 and Figure 5 As shown, the contact angle of the formed gallium-based liquid metal droplet on the polyethylene is 122.37°.

[0093] Table 1 Contact angle test data of gallium-based liquid metal droplets on different substrates

[0094] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Base Printing paper Steel Plate PDMS Ecoflex Polyethylene Contact angle (°) 136.25 131 113.97 91.54 122.37

[0095] In summary, according to Example 1 and Comparative Examples 1-4, when the substrate is printing paper, the contact angle of the gallium-based liquid metal droplets on the printing paper is the largest and the wettability is poor, which means that the gallium-based liquid metal droplets are easy to maintain a spherical shape on the printing paper, and are easy to spread on other substrates (e.g., polyethylene), and are not easy to form a spherical shape. In addition, according to Examples 1-3, it can be seen that gallium-based liquid metal droplets of different sizes and uniform distribution can be prepared through the principle of mass invariance, realizing a process flow of controllable size droplets. In addition, according to Example 4, based on the uniform size of the formed gallium-based liquid metal droplets, a composite material containing a honeycomb arrangement configuration can be formed, which effectively improves the application performance.

[0096] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present disclosure, but the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and substance of the present disclosure, and these modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A method for preparing gallium-based liquid metal droplets with controllable size, characterized in that: The preparation method comprises: Melting solid pure gallium to obtain gallium-based liquid metal; Gallium-based liquid metal is placed in a capillary for condensation, and the capillary is removed to obtain a gallium-based liquid metal wire; According to the required size of the gallium-based liquid metal droplet, cutting the gallium-based liquid metal wire segment of corresponding length; The gallium-based liquid metal wire segment is placed on a substrate, and the substrate with the gallium-based liquid metal wire segment is heated and frozen to solidify to obtain gallium-based liquid metal droplets.

2. The preparation method according to claim 1, characterized in that: The length of the gallium-based liquid metal wire segment is determined using the following formula: h is the length of the gallium-based liquid metal wire segment, d 球 is the diameter of the gallium-based liquid metal droplet, d 柱 is the inner diameter of the capillary.

3. The preparation method according to claim 2, characterized in that: The diameter of the gallium-based liquid metal droplet ranges from 0.246 mm to 4 mm.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The gallium-based liquid metal is placed in the capillary tube and condensed at a temperature of -20°C to -15°C for a period of 8 hours to 12 hours.

5. The preparation method according to any one of claims 1 to 3, characterized in that: The temperature at which the substrate having the gallium-based liquid metal wire segment is heated is 48° C. to 53° C.

6. The preparation method according to any one of claims 1 to 3, characterized in that: The substrate with the gallium-based liquid metal wire segment is subjected to a freezing solidification treatment at a temperature of -13°C to -8°C and a time of 0.5h to 1.5h.

7. The preparation method according to any one of claims 1 to 3, characterized in that: The material of the capillary is polytetrafluoroethylene.

8. The preparation method according to any one of claims 1 to 3, characterized in that: The substrate is printing paper.

9. A size-controllable gallium-based liquid metal droplet, characterized in that: The gallium-based liquid metal droplets are prepared by the preparation method according to any one of claims 1 to 8.

10. A composite material, characterized in that: The composite material comprises a stacked silicone base film, a plurality of regularly arranged gallium-based liquid metal droplets and a silicone coating; wherein the plurality of gallium-based liquid metal droplets are the gallium-based liquid metal droplets described in claim 9.

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