Self-sintering printable liquid metal-montmorillonite composite conductive ink as well as preparation method and application thereof

Abstract

The invention relates to the technical field of electronic materials, in particular to self-sintering printable liquid metal-montmorillonite composite conductive ink as well as a preparation method and application thereof. The liquid metal-montmorillonite composite conductive ink is prepared from the following raw materials in percentage by mass: 90 to 97.5 percent of liquid metal; 2.5 to 10% of montmorillonite micro powder; wherein the liquid metal is gallium-indium eutectic alloy. The liquid metal-montmorillonite composite conductive ink disclosed by the invention is simple in structure and excellent in performance, has excellent conductivity without activation treatment, and can be directly printed at normal temperature and maintain high conductivity; the method can adapt to various substrates and pattern structures, and has wide prospects in the fields of flexible electronics, biosensing, intelligent wearing and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electronic materials, and particularly relates to a self-sintering printable liquid metal-montmorillonite composite conductive ink as well as a preparation method and application thereof. BACKGROUND

[0002] In recent years, with the development of intelligent wearable devices, biomedical monitoring systems and human-computer interaction technology, the demand for flexible stretchable electronic devices is increasing. Existing electronic materials mostly adopt rigid structures, which are difficult to adapt to high-curvature, dynamic deformation surfaces such as human joints, thereby limiting their application in biomedical and wearable technology. Compared with traditional rigid electronic devices, flexible electronic devices can be closely attached to complex curved surfaces or even dynamic tissue surfaces (such as skin, joints, etc.) without affecting the performance, thereby realizing stable and continuous signal acquisition and transmission, and being widely applied to frontier technical fields such as physiological signal monitoring, electromyographic identification analysis, remote rehabilitation diagnosis and treatment, and wearable computing platforms. Among many flexible conductor materials, gallium-based liquid metals (such as pure gallium, gallium-indium eutectic alloy (EGaIn) and gallium-indium-tin alloy (GaInSn)) have become an important direction of flexible electronic material research in recent years due to their liquid state at room temperature, high electrical conductivity, excellent stretchability and good biocompatibility. Such materials not only have metal-state electrical conductivity, but also maintain electrical continuity during mechanical deformation such as stretching, bending or twisting due to their excellent fluidity, showing much more flexible performance than traditional conductive polymers or metal nanowires. However, the high surface tension of the liquid metal itself leads to the aggregation of the liquid metal into spherical liquid beads during processing, making it difficult to achieve precise patterning on the surface of the substrate. In addition, most common flexible substrates (such as PDMS, PET, PI, paper, fabric, etc.) exhibit super-metal repulsion or oxide repulsion to liquid metals, making it difficult for liquid metals to spread or adhere uniformly on them, hindering the large-scale application of liquid metals in the field of flexible electronics. To overcome the above problems, researchers have proposed various improvement strategies, such as dispersing liquid metal micro / nano droplets in an elastic polymer matrix to form a composite material to reduce fluidity and improve pattern stability; or introducing magnetic or conductive fillers (such as Fe, Ni, Ag, Cu, carbon nanotubes, etc.) to prepare liquid metal composite paste, and enhancing the adhesion of the conductive network to the substrate through physical cross-linking or formation of intermetallic compounds. However, these methods generally have the problems of complex process, reduced electrical conductivity or the need for additional activation steps (such as mechanical pressing, heating, etc.), which are difficult to meet the needs of high-resolution, stretchable electronic device rapid printing manufacturing. Therefore, there is an urgent need for a liquid metal composite conductive ink with simple structure, excellent performance, which can be directly printed at room temperature and maintain high electrical conductivity, especially should take into account its adaptation to various flexible substrates, high-resolution patterning capability, and good mechanical flexibility and environmental stability, to meet the application requirements of the next generation of flexible bioelectronic devices. SUMMARY

[0003] In view of the above-mentioned disadvantages of the prior art, the purpose of the present application is to provide a self-sintering printable liquid metal-montmorillonite composite conductive ink as well as a preparation method and application thereof, which is used to solve the problems of poor printing precision, poor substrate adhesion and poor conductivity under the condition of no external activation of the liquid metal conductive ink in the prior art.

[0004] To achieve the above-mentioned purpose and other related purposes, the present application is obtained by the following technical solutions.

[0005] The first aspect of the present application provides a liquid metal-montmorillonite composite conductive ink, the raw materials of the liquid metal-montmorillonite composite conductive ink comprise, by mass percentage:

[0006] 90-97.5% of liquid metal;

[0007] 2.5-10% of montmorillonite powder;

[0008] The liquid metal is gallium-indium eutectic alloy.

[0009] In some embodiments of the present application, the mass percentage of gallium in the gallium-indium eutectic alloy is 74.5%-75.5%, and the mass percentage of indium is 24.5%-25.5%.

[0010] In some embodiments of the present application, the melting point of the gallium-indium eutectic alloy is 15.5-16.5℃.

[0011] In some embodiments of the present application, the electrical conductivity of the gallium-indium eutectic alloy at 20℃ is 3.2x10 6 -3.5x10 6 S / m.

[0012] In some embodiments of the present application, the particle size of the montmorillonite powder is 0.5-2.5μm.

[0013] In some embodiments of the present application, the specific surface area of the montmorillonite powder is 50-200m 2 / g.

[0014] The second aspect of the present application provides a preparation method of a liquid metal-montmorillonite composite conductive ink, comprising the following steps: mixing and stirring liquid metal and montmorillonite powder, and obtaining a liquid metal-montmorillonite composite conductive ink after uniform stirring.

[0015] In some embodiments of the present application, the stirring is planetary stirring.

[0016] In some embodiments of the present application, the stirring is divided into first stirring and second stirring.

[0017] In some embodiments of the present application, the first stirring speed is 100-300 rpm; the first stirring time is 4-10 minutes.

[0018] In some embodiments of the present application, the second stirring speed is 850-1150 rpm; the second stirring time is 20-40 minutes.

[0019] In some embodiments of the present application, the viscosity of the liquid metal-montmorillonite composite conductive ink is 2x10 3 -8x10 4 Pa·s.

[0020] In some embodiments of the present application, the color of the liquid metal-montmorillonite composite conductive ink is silver white.

[0021] In some embodiments of the present application, the electrical conductivity of the liquid metal-montmorillonite composite conductive ink at 20℃ is 1.4x10 6 -2.8x10 6 S / m.

[0022] The present application also provides a preparation method of a strain sensor, comprising the following steps: extruding the prepared liquid metal-montmorillonite composite conductive ink after being loaded into a container, printing a pattern on a flexible substrate, covering a layer of packaging material after the pattern printing is completed, standing and curing to form a flexible conductive structure, and obtaining the strain sensor.

[0023] In some embodiments of the present application, the liquid metal-montmorillonite composite conductive ink is loaded into a container for use after the third stirring, the third stirring speed is 100-300 rpm; the time is 2-10 minutes.

[0024] In some embodiments of the present application, the flexible substrate is a platinum catalytic silica gel material, a PI film or a PET film.

[0025] In some embodiments of the present application, the printing speed is 2-10 mm / s.

[0026] In some embodiments of the present application, the packaging material is a platinum catalytic silica gel material, a PI film or a PET film.

[0027] In some embodiments of the present application, the curing temperature is room temperature; the curing time is 3-6 h.

[0028] As described above, the self-sintering and printable liquid metal-montmorillonite composite conductive ink of the present invention, as well as its preparation method and application, have the following beneficial effects: the liquid metal-montmorillonite composite conductive ink of the present invention has a simple structure and excellent performance, has excellent conductivity without activation treatment, and can be directly printed at room temperature and maintain high conductivity; it can be adapted to a variety of substrates and pattern structures and has broad prospects in the fields of flexible electronics, biosensors, and smart wearables. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a flow chart for preparing the liquid metal-montmorillonite composite conductive ink in Example 1 of the present invention.

[0030] Figure 2 This is a scanning electron microscope image of the liquid metal-montmorillonite composite conductive ink in Example 1 of the present invention.

[0031] Figure 3 This is a data graph showing the resistance variation of the liquid metal-montmorillonite composite conductive ink as a function of temperature in Example 1 of the present invention.

[0032] Figure 4 Schematic diagram of the structure of the strain sensor in Example 1 of the present invention.

[0033] Figure 5 This is a data diagram showing the resistance change rate of the strain sensor according to Example 1 of the present invention as a function of the strain rate.

[0034] Figure 6 This is a diagram of fatigue test data of the strain sensor in Example 1 of the present invention.

[0035] Figure 7 This is a data graph of the storage modulus and loss modulus of the liquid metal-montmorillonite composite conductive ink in Example 2 of the present invention.

[0036] Figure 8 4 is a graph showing the relationship between viscosity and shear rate of the liquid metal-montmorillonite composite conductive ink in Example 2 of the present invention.

[0037] Figure 9 These are the printing effects of the liquid metal-montmorillonite composite conductive ink in Example 3 of the present invention on different substrates.

[0038] Figure 10 This is a pneumatic printing effect diagram of the eutectic gallium-indium alloy in comparative example 1 of the present invention. DETAILED DESCRIPTION

[0039] Following, the advantages and effects of the present application can be easily understood by those skilled in the art from the disclosure of the present specification. The present application can also be implemented or applied by means of other different specific embodiments, and the details in the present specification can be modified or changed in various ways based on different views and applications without departing from the spirit of the present application.

[0040] It should be noted that the process equipment or device not specifically mentioned in the following examples is the conventional equipment or device in the art.

[0041] The present application provides a self-sintering printable liquid metal-montmorillonite composite conductive ink, a preparation method and application thereof. By introducing natural clay mineral montmorillonite into the liquid metal system in a mechanical mixing manner, the rheological properties, shear thinning characteristics and adhesion ability to various flexible substrates of the ink are significantly improved. The composite conductive ink of the present application is suitable for direct ink printing (DIW) method, and can realize high-resolution patterning with line width less than 100 μm on various substrates including PDMS, PET, PI, glass, paper, etc., and stable conductivity can be realized without subsequent mechanical activation or heat treatment. The strain sensor prepared based on the composite conductive ink can be used for real-time monitoring of large human joint movements (such as wrist, elbow, knee bending) and small physiological movements (such as swallowing, neck rotation), and exhibits high sensitivity, low hysteresis and excellent repeatability. On this basis, the present application is completed.

[0042]

Liquid metal-montmorillonite composite conductive ink

[0043] The present application provides a liquid metal-montmorillonite composite conductive ink, which comprises, by mass percentage:

[0044] Liquid metal 90-97.5%, which can be selected from 90-92%, 92-94%, 94-96%, 96-97.5%, 90-95% or 95-97.5%;

[0045] Montmorillonite powder 2.5-10%, which can be selected from 2.5-4%, 4-6%, 6-8%, 8-10%, 2.5-6% or 6-10%;

[0046] Wherein, the liquid metal is a gallium-indium eutectic alloy.

[0047] The control of liquid metal and montmorillonite powder within the mass percentage range can form a uniform composite conductive ink by mixing. Beyond this range, due to the high proportion of montmorillonite powder, the liquid metal is difficult to uniformly wrap all the montmorillonite powder, resulting in uneven mixing and failure to form a homogeneous phase conductive ink.

[0048] The melting point (15.5-16.5℃) of the gallium-indium eutectic alloy ensures its liquid state at room temperature, and meanwhile, it has no biological toxicity, which is suitable for the processing and manufacturing of wearable sensors.

[0049] In the liquid metal-montmorillonite composite conductive ink provided by the application, the mass percentage of gallium in the gallium-indium eutectic alloy is 74.5%-75.5%, which can be selected as 74.5-75% or 75-75.5%; the mass percentage of indium is 24.5%-25.5%, which can be selected as 24.5-25% or 25-25.5%; the melting point of the gallium-indium eutectic alloy is 15.5-16.5℃, which can be selected as 15.5-16℃ or 16-16.5℃; the electrical conductivity of the gallium-indium eutectic alloy at 20℃ is 3.2×10 6 -3.5×10 6 S / m, which can be selected as 3.2×10 6 -3.3×10 6 S / m, 3.3×10 6 -3.4×10 6 S / m or 3.4×10 6 -3.5×10 6 S / m. In a preferred embodiment, the gallium-indium eutectic alloy is purchased from Dongguan City Houcheng Dingtai Metal Material Factory.

[0050] In the liquid metal-montmorillonite composite conductive ink provided by the application, the particle size of the montmorillonite powder is 0.5-2.5μm, which can be selected as 0.5-1μm, 1-1.5μm, 1.5-2μm, 2-2.5μm, 0.5-1.5μm or 1.5-2μm; the specific surface area of the montmorillonite powder is 50-200m 2 / g, which can be selected as 50-100m 2 / g, 100-150m 2 / g or 150-200m 2 / g.

[0051] The liquid metal-montmorillonite composite conductive ink provided by the application has self-sintering property and printability, wherein the printability refers to that the ink has good rheological property and shear thinning behavior, is suitable for printing processes such as direct ink writing (DIW), and can form high-resolution patterns on various flexible or rigid substrates without complex treatment to realize patterning.

[0052] The self-sintering property refers to that after printing is completed, the conductive components (such as liquid metal) in the ink can naturally form a stable conductive network without additional high-temperature heat treatment or mechanical activation. This means that the pattern can realize conductivity at room temperature or under ambient conditions without the sintering step (such as heating to several hundred degrees Celsius or activating by mechanical force) commonly used in traditional conductive inks.

[0053] Preparation method of liquid metal-montmorillonite composite conductive ink

[0054] The second aspect of the present application provides a preparation method of the liquid metal-montmorillonite composite conductive ink as described above, comprising the following steps: mixing and stirring the liquid metal and the montmorillonite powder, and obtaining the liquid metal-montmorillonite composite conductive ink after uniform stirring. Specifically, the montmorillonite powder is added into the liquid metal, the liquid metal and the montmorillonite powder are preliminarily mixed by using a planetary centrifugal stirrer (BHJ-3) through first stirring, and then the stirring speed is increased for second stirring to uniformly mix the montmorillonite powder in the liquid metal until the liquid metal-montmorillonite composite conductive ink with uniform, silver-white color and viscosity is obtained.

[0055] In the preparation method of the liquid metal-montmorillonite composite conductive ink provided by the present application, the speed of the first stirring is 100-300 rpm, which can be selected as 100-200 rpm or 200-300 rpm; and the time of the first stirring is 4-10 minutes, which can be selected as 4-6 minutes, 6-8 minutes or 8-10 minutes.

[0056] In the preparation method of the liquid metal-montmorillonite composite conductive ink provided by the present application, the speed of the second stirring is 850-1150 rpm, which can be selected as 850-1000 rpm or 1000-1150 rpm; and the time of the second stirring is 20-40 minutes, which can be selected as 20-30 minutes or 30-40 minutes.

[0057] In the preparation method of the liquid metal-montmorillonite composite conductive ink provided by the present application, the viscosity of the liquid metal-montmorillonite composite conductive ink is 2×10 3 -8×10 4 Pa·s.

[0058] In the preparation method of the liquid metal-montmorillonite composite conductive ink provided by the present application, the color of the liquid metal-montmorillonite composite conductive ink is silver-white.

[0059] In the preparation method of the liquid metal-montmorillonite composite conductive ink provided by the present application, the electrical conductivity of the liquid metal-montmorillonite composite conductive ink at 20℃ is 1.4×10 6 -2.8×10 6 S / m, which can be selected as 1.4×10 6 -2×10 6 S / m, 2×10 6 -2.5×10 6 S / m or 2.5×10 6 -2.8×10 6 S / m.

[0060] Application

[0061] The application also provides application of the liquid metal-montmorillonite composite conductive ink and the liquid metal-montmorillonite composite conductive ink prepared by the preparation method in a flexible stretchable electronic device.

[0062] Method for preparing strain sensor

[0063] The application also provides a method for preparing a strain sensor, which comprises the following steps: extruding the liquid metal-montmorillonite composite conductive ink prepared by the method after being loaded into a container, printing a pattern on a flexible substrate, covering the pattern with a layer of packaging material after the pattern printing is completed, and standing for solidification to form a flexible conductive structure, thereby obtaining the strain sensor. Specifically, the prepared liquid metal-montmorillonite composite conductive ink is loaded into a syringe, the pressure is controlled by using an air pressure regulator, and the required pattern is directly printed on a pre-solidified flexible substrate through a 23G needle (inner diameter about 300 μm), and a layer of packaging is covered after the patterning, and solidification is performed at room temperature.

[0064] In the method for preparing the strain sensor, the liquid metal-montmorillonite composite conductive ink is loaded into a syringe after the third stirring for removing bubbles in the ink and restoring uniformity, the speed of the third stirring is 100-300 rpm, which can be selected as 100-200 rpm or 200-300 rpm, and the time is 2-10 minutes, which can be selected as 2-5 minutes, 5-8 minutes or 8-10 minutes. In a preferred embodiment, the pressure applied when the syringe pushes the composite conductive ink to extrude from the needle is 10-40 kPa, which can be selected as 10-20 kPa, 20-30 kPa or 30-40 kPa.

[0065] In the method for preparing the strain sensor, the flexible substrate is a platinum-catalyzed silica gel material, a PI film or a PET film. In a specific embodiment, the flexible substrate is Ecoflex 00-30 (Smooth-On).

[0066] In the method for preparing the strain sensor, the printing speed is 2-10 mm / s, which can be selected as 2-5 mm / s, 5-8 mm / s or 8-10 mm / s.

[0067] In the method for preparing the strain sensor, the packaging material is a platinum-catalyzed silica gel material, a PI film or a PET film. In a specific embodiment, the packaging material is Ecoflex 00-30.

[0068] In the method for preparing the strain sensor, the solidification temperature is room temperature, and the solidification time is 3-6 h, which can be selected as 3-4 h, 4-5 h or 5-6 h.

[0069] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application is specifically described below in conjunction with examples and drawings.

[0070] In the following examples, each of the reaction raw materials is a commercially available product unless otherwise specified.

[0071] Unless otherwise specified, the purity of each product of each embodiment of the present application is more than 98%.

[0072] A specific embodiment of a flexible stretchable electronic device and a preparation method thereof is provided below.

[0073] Example 1

[0074] In this embodiment, a self-sintering printable liquid metal-montmorillonite composite conductive ink is prepared, and characterization tests and analysis are performed thereon. The preparation method comprises the following steps: 1 g of montmorillonite powder is added to 20 g of eutectic gallium-indium alloy (EGaIn, Ga:In = 75.5:24.5), and a planetary centrifugal stirrer is used to stir at 200 rpm for 5 minutes and at 1000 rpm for 30 minutes in sequence until a uniform, silver-white, moderately adhesive ink is obtained. The ink is stirred at 200 rpm for another 5 minutes before use to remove bubbles and restore uniformity. The prepared liquid metal-montmorillonite composite conductive ink is coated on a conductive tape and analyzed by scanning electron microscopy. It can be seen from Figure 2 that the montmorillonite powder is uniformly distributed in the liquid metal, and the conductive path of the liquid metal itself is not blocked, so the conductive ink of the present application can conduct electricity without an additional sintering process. The temperature stability of the ink is analyzed by placing the conductive ink on an intelligent constant temperature heating table (BY-S215), setting different temperatures, and measuring the resistance when the set temperature is reached. It can be seen from Figure 3 that the resistance drift in the temperature range of 25-95℃ is less than 6.65%, indicating good thermal stability.

[0075] In this embodiment, a strain sensor is prepared, and the specific process comprises the following steps: the liquid metal-montmorillonite composite conductive ink prepared in Example 1 is loaded into a syringe, a pressure regulator is used to control the pressure at 25 kPa, and a 23G needle (inner diameter about 300 μm) is used to directly print the required pattern on a pre-solidified Ecoflex 00-30 flexible substrate at a printing speed of 4 mm / s. After patterning, a layer of Ecoflex 00-30 encapsulation is covered, and the encapsulation is cured at room temperature for 4 hours. (See Figure 4 for a structural schematic diagram.) The sensor is fixed on a universal tensile testing machine (Mark-10), the tensile stroke is set to 100% of the initial length, and a digital multimeter (SDM3055X-E) is used to test the resistance change of the sensor. It can be seen from Figure 5It can be seen that the prepared strain sensor exhibits a linear response in the strain range of 0–100%, and the hysteresis ratio within the range is less than 1.05. Figure 6 It can be seen that the resistance change of the prepared strain sensor remained stable after 125 cycles of testing at 50% strain.

[0076] Example 2

[0077] In this example, various self-sintering, printable liquid metal-montmorillonite composite conductive inks were prepared, characterized, and analyzed. The preparation method included the following steps: 0.5g, 1g, 1.5g, and 2g of montmorillonite powder were added to 20g of a eutectic gallium-indium alloy (EGaIn, Ga:In = 75.5:24.5). The mixture was stirred in a planetary centrifugal mixer at 200 rpm for 5 minutes and then at 1000 rpm for 30 minutes, until a uniform, silvery-white ink with moderate viscosity was obtained. Before use, the mixture was stirred again at 200 rpm for 5 minutes to remove bubbles and restore uniformity.

[0078] The rheological properties of the ink were analyzed by placing the ink sample on the test platform of the rotational rheometer (HAAKE MARS iQ AIR) and setting the distance between the upper and lower test discs to 1mm. -1 The sample was pre-sheared at a shear rate of 0.5%. Under the condition of 0.5% strain, the frequency sweep was performed in the test range of 0.1-100 rad·s -1 , the storage modulus (G') and loss modulus (G") of the sample were tested, as shown in Figure 7 As shown in Figure 3, the storage modulus (G') of the sample is greater than the loss modulus (G"), indicating that the sample can maintain a stable shape after printing.

[0079] To analyze the viscosity of the sample, the ink sample was placed on the test platform of the rotational rheometer (HAAKE MARS iQ AIR) and the distance between the upper and lower test discs was set to 1mm. -1 The sample is pre-sheared at a shear rate of 0.001 to 10s -1 Under the shear rate range, the sample is subjected to dynamic viscosity scanning, and the viscosity of the sample is tested to obtain the shear rate change curve, such as Figure 8 As shown in the figure, the viscosity of the sample decreases with the shear rate, showing obvious shear thinning properties, indicating that the sample is suitable for pneumatic extrusion printing.

[0080] Example 3

[0081] This example prepared a self-sintering, printable liquid metal-montmorillonite composite conductive ink and tested it with pneumatic extrusion printing. The preparation method included the following steps: 0.5g of montmorillonite powder was added to 20g of a eutectic gallium-indium alloy (EGaIn, Ga:In = 75.5:24.5). The mixture was stirred using a planetary centrifugal mixer at 200 rpm for 5 minutes and then at 1000 rpm for 30 minutes until a uniform, silvery-white ink with moderate viscosity was obtained. Before use, the mixture was stirred again at 200 rpm for 5 minutes to remove bubbles and restore uniformity.

[0082] The prepared liquid metal-montmorillonite composite conductive ink was loaded into a syringe, and the pressure was controlled at 25 kPa by a gas pressure regulator. The desired pattern was directly printed on PET substrates, glass substrates, PVC substrates and paper substrates through a 23G needle (inner diameter of about 300 μm). The printing speed was controlled at 4 mm / s. The results are shown in Figure 2. Figure 9 As shown, it shows that the ink has good adhesion to various substrates.

[0083] Comparative Example 1

[0084] This example uses a eutectic gallium-indium alloy without montmorillonite powder for pneumatic extrusion printing, and the results are analyzed. The eutectic gallium-indium alloy (purchased from Dingtai Metal Material Factory, Houjie, Dongguan City) is loaded into a syringe, and a pressure regulator is used to control the pressure to 25kPa. The desired pattern is directly printed on a pre-cured Ecoflex 00-30 substrate through a 23G needle (inner diameter of about 300μm). The printing speed is controlled at 4mm / s. The printing results are shown in Figure 2. Figure 10 As shown in the figure, the eutectic gallium-indium alloy will gather into liquid beads after being printed by pneumatic extrusion and cannot maintain a good straight shape.

[0085] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A liquid metal-montmorillonite composite conductive ink, characterized in that: The raw materials of the liquid metal-montmorillonite composite conductive ink include, by mass percentage: Liquid metal 90-97.5%; Montmorillonite micro powder 2.5-10%; Among them, the liquid metal is a gallium-indium eutectic alloy.

2. The liquid metal-montmorillonite composite conductive ink according to claim 1, characterized in that: Also includes any one or more of the following features: A1) the mass percentage of gallium in the gallium-indium eutectic alloy is 74.5%-75.5%; the mass percentage of indium is 24.5%-25.5%; A1) the melting point of the gallium-indium eutectic alloy is 15.5° C.-16.5° C.; A2) The electrical conductivity of the gallium-indium eutectic alloy at 20°C is 3.2×10 6 -3.5×10 6 S / m.

3. The liquid metal-montmorillonite composite conductive ink according to claim 1, characterized in that: Also includes any one or more of the following features: B1) the particle size of the montmorillonite powder is 0.5-2.5 μm; B2) The specific surface area of ​​the montmorillonite powder is 50-200m 2 / g.

4. The method for preparing the liquid metal-montmorillonite composite conductive ink according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: mixing liquid metal and montmorillonite micropowder and stirring them evenly to obtain liquid metal-montmorillonite composite conductive ink.

5. The method for preparing the liquid metal-montmorillonite composite conductive ink according to claim 4, characterized in that: Include at least one of the following technical features: C1) the stirring is planetary stirring; C2) The stirring is divided into a first stirring and a second stirring.

6. The method for preparing the liquid metal-montmorillonite composite conductive ink according to claim 5, characterized in that: Include at least one of the following technical features: C21) the first stirring speed is 100-300 rpm; C22) the first stirring time is 4-10 minutes; C23) the second stirring speed is 850-1150 rpm; C24) the second stirring time is 20-40 minutes.

7. The method for preparing the liquid metal-montmorillonite composite conductive ink according to claim 4, characterized in that: Include at least one of the following technical features: C3) The viscosity of the liquid metal-montmorillonite composite conductive ink is 2×10 3 -8×10 4 Pa·s; C4) the color of the liquid metal-montmorillonite composite conductive ink is silvery white; C5) The conductivity of the liquid metal-montmorillonite composite conductive ink at 20°C is 1.4×10 6 -2.8×10 6 S / m.

8. Use of the liquid metal-montmorillonite composite conductive ink according to any one of claims 1 to 3 and / or the liquid metal-montmorillonite composite conductive ink prepared by the preparation method according to any one of claims 4 to 6 in flexible and stretchable electronic devices.

9. A method for preparing a strain sensor, characterized in that: The invention comprises the following steps: placing the liquid metal-montmorillonite composite conductive ink according to any one of claims 1 to 3 or the liquid metal-montmorillonite composite conductive ink prepared by the preparation method according to any one of claims 4 to 6 into a container and then extruding it; printing a pattern on a flexible substrate; covering a layer of packaging material after the pattern printing is completed; standing and curing; forming a flexible conductive structure, and thus obtaining a strain sensor.

10. The method for preparing a strain sensor according to claim 9, wherein: Includes any one or more of the following characteristics: D1) the liquid metal-montmorillonite composite conductive ink is placed in a container after a third stirring, wherein the third stirring speed is 100-300 rpm and the time is 2-10 minutes; D2) the flexible substrate is a platinum-catalyzed silica gel material, a PI film or a PET film; D3) the printing speed is 2-10 mm / s; D4) the packaging material is a platinum-catalyzed silica gel material, a PI film or a PET film; D5) The curing temperature is room temperature; the curing time is 3-6 hours.

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