Durable metal gel as well as preparation method and application thereof

Abstract

The invention discloses durable metal gel as well as a preparation method and application thereof, and belongs to the technical field of conductive elastomers and composite materials. The preparation method comprises the following steps that S1, a liquid metal-waterborne polyurethane mixed solution is prepared, specifically, liquid metal and waterborne polyurethane dispersion liquid are mixed and dispersed, and the liquid metal-waterborne polyurethane mixed solution is obtained; and S2, drying treatment is conducted, specifically, the liquid metal-waterborne polyurethane mixed solution is dried, and the durable metal gel is obtained. The durable metal gel disclosed by the invention has both metal-grade electronic conductivity and durability.

Description

Technical Field

[0001] The present invention relates to the technical fields of conductive elastomers and composite materials, and more specifically, to a durable metal gel and its preparation method and application. Background Art

[0002] Conductive elastomers have great application potential in many emerging fields such as wearable electronics and soft robots. Therefore, conductive elastomer materials need to achieve a metal conductivity of more than 10 6 S / m to reduce the internal resistance of the device, thereby improving the signal transmission quality and minimizing energy consumption. Moreover, this ultra-high conductivity must be maintained after undergoing long-term cyclic stretching (even up to 1 million times) to match the actual application requirements. For example, an electrocardiogram monitor attached to the skin surface needs to withstand nearly 1.2 million stretching deformations within three years due to the stretching and contraction of the skin.

[0003] However, the currently developed materials cannot meet the above performance requirements. Among them, metal conductors have a conductivity exceeding 10 6 S / m, but their inherent rigidity makes them unable to withstand stretching deformation. In addition, polymer materials such as elastomers can withstand more than or equal to 1 million stretching cycles, but their insulating properties cannot meet the needs. To solve these limitations, composite materials developed by incorporating conductive fillers into a polymer matrix are expected to simultaneously possess high conductivity and durability. However, the conductive pathways in these composite materials usually change after repeated stretching, resulting in a sharp change in resistance. For example, composite materials based on rigid fillers such as silver and gold nanowires will face random migration of the fillers after repeated stretching, and composite materials based on flexible fillers such as liquid metals will face activation connection or leakage of the liquid metals during cyclic stretching, which both lead to changes in the conductive pathways and thus cause instability of the conductivity. Therefore, there are still great challenges in developing conductive elastomers that can simultaneously have metal-level conductivity and ultra-high durability. Summary of the Invention

[0004] 1. Technical Problems to be Solved by the Invention

[0005] The purpose of the present invention is to overcome the problem that metal gels in the prior art cannot simultaneously possess metal-level electronic conductivity and durability, and provide a durable metal gel that combines metal-level electronic conductivity and durability; at the same time, a preparation method and application of the durable metal gel are provided.

[0006] 2. Technical Solutions

[0007] For the above purposes, the present invention provides a durable metal gel material, which forms a continuous phase of liquid metal inside the material and is fixed by a three-dimensional continuous polymer network to achieve metal-level conductivity. Moreover, due to the good interface between the liquid metal and the elastic polymer in the material, when the material undergoes tensile deformation, the liquid metal continuum can deform synchronously with the elastic polymer network, thereby achieving high durability. Specifically, the object of the present invention is achieved through the following technical solutions:

[0008] [Preparation Method of Durable Metal Gel and Durable Metal Gel Prepared Thereby]

[0009] In the first aspect, the present invention provides a preparation method of a durable metal gel, including the following steps:

[0010] S1. Prepare a liquid metal-aqueous polyurethane mixed solution: Mix and disperse liquid metal and an aqueous polyurethane dispersion to obtain a liquid metal-aqueous polyurethane mixed solution;

[0011] S2. Drying treatment: Perform drying treatment on the liquid metal-aqueous polyurethane mixed solution to obtain a durable metal gel.

[0012] It should be noted that in the present invention, liquid metal is dispersed in an elastic aqueous polyurethane polymer network. The elastic aqueous polyurethane network provides good mechanical support for the material. The electrostatic interaction between the oxide layer on the surface of the liquid metal and the aqueous polyurethane network establishes a good interface and provides a uniform stress conduction path between the two. Therefore, when the durable metal gel is deformed by force, the applied force causes the aqueous polyurethane network to deform; at the same time, the liquid metal and the aqueous polyurethane network deform synchronously, so that the conductive phase and the mechanical phase change conformally. Finally, the liquid metal continuum realizes the reversible deformation of its own conductive path by virtue of the elasticity of the aqueous polyurethane network. The obtained durable metal gel not only has high electronic conductivity at the metal level but also has durability comparable to that of an elastomer.

[0013] It should also be noted that in the prior art, ordinary polymers such as sodium alginate and hyaluronic acid are usually used as raw materials to prepare metal gels, and it is considered that elastomeric polymers are a kind of material that is not conducive to the preparation of metal gels because the side chains of elastomeric polymers usually do not have polar groups that can form electrostatic interactions with the oxide layer of liquid metal. However, the applicant creatively discovers that an elastomeric polymer aqueous polyurethane with carboxyl groups in its side chains can be used as a raw material to prepare a durable metal gel with both metal-level electronic conductivity and durability. On the other hand, samples prepared from common elastomeric polymers such as polydimethylsiloxane (PDMS) and styrene-butadiene-styrene block copolymer (SBS) are almost all in an insulating state.

[0014] Further, in step S1, the mass ratio of the liquid metal to the waterborne polyurethane in the waterborne polyurethane dispersion is (10-60):1.

[0015] It should be noted that the above ratio ensures that the liquid metals penetrate each other throughout the material to form a continuous phase, providing a good electronic path for the durable metal gel; it also ensures that the waterborne polyurethane polymer network presents a continuous three-dimensional porous structure, providing good mechanical support for the durable metal gel.

[0016] Further, the waterborne polyurethane includes carboxylic acid type waterborne polyurethane.

[0017] Preferably, the waterborne polyurethane is carboxylic acid type waterborne polyurethane.

[0018] Further, the liquid metal includes at least one of metal gallium, gallium-indium alloy, and gallium-indium-tin alloy.

[0019] Further, the mass fraction of gallium in the gallium-indium alloy is greater than or equal to 75.50%, and the mass fraction of indium is less than or equal to 24.5%.

[0020] Furthermore, the mass fraction of gallium in the gallium-indium alloy is 75.50%, and the mass fraction of indium is 24.5%.

[0021] Further, the mass ratio of gallium, indium, and tin in the gallium-indium-tin alloy is 68.50:21.50:10.00.

[0022] It should be noted that the waterborne polyurethane in the waterborne polyurethane dispersion uses carboxylic acid type waterborne polyurethane, and the liquid metal uses at least one of metal gallium, gallium-indium alloy, and gallium-indium-tin alloy. The reason is that the side chain of carboxylic acid type waterborne polyurethane contains carboxyl groups, which can form electrostatic interactions with trivalent gallium ions in the surface oxide layer of the liquid metal, thus forming a good interface between the liquid metal and the polymer network.

[0023] On the other hand, the liquid metal includes at least one of metal gallium, gallium-indium alloy, and gallium-indium-tin alloy. Gallium, indium metals and their alloys have the advantages of being safe, non-toxic, and having excellent performance. Liquid metals such as mercury, cesium, and francium are toxic, radioactive, or dangerous, and are greatly restricted in applications.

[0024] Furthermore, the liquid metal is metal gallium, gallium-indium alloy or gallium-indium-tin alloy.

[0025] Further, in step S1, the solid content of the waterborne polyurethane dispersion is 10wt% - 60wt%.

[0026] Preferably, the solid content of the waterborne polyurethane dispersion is 10wt% - 20wt%.

[0027] It should be noted that using an aqueous polyurethane dispersion with a solid content of 10 wt% to 20 wt% is beneficial for obtaining a liquid metal-aqueous polyurethane mixed solution with better uniformity through mixing and dispersion.

[0028] Furthermore, the aqueous polyurethane dispersion with a solid content of 10 wt% to 20 wt% can be obtained by adding deionized water to dilute a high-solid-content aqueous polyurethane dispersion.

[0029] For example, add three times the mass of deionized water to an aqueous polyurethane dispersion with a solid content of 60.00 wt%, and continuously stir magnetically at a temperature of 25 °C until evenly mixed to obtain an aqueous polyurethane dispersion with a solid content of 15.00 wt%.

[0030] Further, in step S2, the conditions for the drying treatment include: the temperature is 25 to 120 °C.

[0031] It should be noted that the purpose of the drying treatment is to remove the solvent in the liquid metal-aqueous polyurethane mixed solution.

[0032] Furthermore, the drying treatment includes the following steps:

[0033] Add the liquid metal-aqueous polyurethane mixed solution to a polytetrafluoroethylene petri dish, place it on a hot plate at 25 to 120 °C to heat and remove the solvent, and obtain a durable metal gel.

[0034] It should be noted that as the drying progresses, the aqueous polyurethane molecules physically crosslink to form a three-dimensional network, and the liquid metal gradually approaches. Eventually, after demolding, the liquid metal forms a continuous phase, and the three-dimensional continuous aqueous polyurethane polymer network is in the liquid metal continuous phase, maintaining the stability of the material.

[0035] Furthermore, in step S2, the temperature of the drying treatment can be 80 to 120 °C or 100 to 120 °C.

[0036] Further, in step S1, the conditions for the mixing and dispersion include: the stirring speed is 8000 rpm to 15000 rpm, and the stirring time is 3 min to 10 min.

[0037] Specifically, the mixing and dispersion can be carried out by a handheld homogenizer.

[0038] It should be noted that after the liquid metal undergoes high-speed stirring and shearing by the homogenizer, micron-sized droplets are formed and dispersed in the solution. The polymer part wraps around the metal surface, and the rest is dispersed in the solvent.

[0039] The second aspect of the present invention provides a durable metal gel prepared by the preparation method of the durable metal gel according to any one of the embodiments of the first aspect of the present invention.

[0040] The electronic conductivity of the durable metal gel is greater than or equal to 5.00×10 5 S / m.

[0041] Furthermore, the electronic conductivity of the durable metal gel is greater than or equal to 1.00×10 6 S / m.

[0042] Preferably, the electronic conductivity of the durable metal gel can reach 3.00×10 6 S / m and can withstand cyclic stretching with a 100% tensile strain for 1 million times.

[0043] Among them, "can withstand cyclic stretching with a 100% tensile strain for 1 million times" means that it does not break after cyclic stretching with a 100% tensile strain for 1 million times and maintains the conductivity basically unchanged.

[0044] [Durable Metal Gel]

[0045] The third aspect of the present invention provides a durable metal gel,

[0046] The durable metal gel includes a liquid metal and an aqueous polyurethane, and the liquid metal is dispersed in the aqueous polyurethane.

[0047] Furthermore, the mass ratio of the liquid metal to the aqueous polyurethane is (10-60):1.

[0048] Furthermore, the aqueous polyurethane includes a carboxylic acid type aqueous polyurethane.

[0049] Furthermore, the liquid metal includes at least one of gallium, gallium-indium alloy, and gallium-indium-tin alloy.

[0050] Furthermore, the electronic conductivity of the durable metal gel is greater than or equal to 5.00×10 5 S / m.

[0051] [Flexible Electronic Products]

[0052] The fourth aspect of the present invention provides a flexible electronic product, which includes the durable metal gel according to any one of the embodiments of the second aspect of the present invention or any one of the embodiments of the third aspect of the present invention.

[0053] The novel highly conductive and highly durable flexible electronic product of the present invention includes a durable metal gel composed of liquid metal and aqueous polyurethane; wherein, the liquid metal forms a continuum as the fluid phase of the gel; the three-dimensional continuous aqueous polyurethane polymer network fixes the liquid metal fluid by means of interaction; there is a good interface between the liquid metals and between the metal and the polymer network, enabling the durable metal gel and the flexible electronic product containing the durable metal gel to have better durability.

[0054] 3. Beneficial effects

[0055] Adopting the technical solution provided by the present invention, compared with the prior art, it has the following beneficial effects:

[0056] (1) For the durable metal gel provided by the present invention, by using liquid metal as the continuous conductive phase in the gel material, a material structure completely different from that of the existing liquid metal composite material is obtained:

[0057] The electronic conductivity at the metal level is achieved by fixing the liquid metal continuum in the elastic three-dimensional polymer network; and, due to the good interface between the liquid metal continuum and the elastic polymer network, the two can achieve synchronous stretching deformation when being stretched, enabling the reversible recovery characteristic of the elastic polymer network to be transformed into the reversible recovery characteristic of the liquid metal continuum, so that the composite material obtains excellent durability, and finally the durable metal gel has both high electronic conductivity and durability.

[0058] (2) In the preparation method of the durable metal gel provided by the present invention, stable durable metal gels can be prepared at different drying temperatures, and there is a good corresponding relationship between the conductivity and the temperature, and a series of durable metal gels with adjustable conductivity can be prepared.

[0059] (3) The durable metal gel prepared by the present invention exhibits high electronic conductivity and high durability. As Figure 13 shown, compared with other highly conductive composite materials in the prior art, the durable metal gel of the present invention stands out in simultaneously achieving high conductivity and high durability; specifically, compared with the existing highly conductive composite materials, the durability of the durable metal gel is increased by at least 50 times. Brief description of the drawings

[0060] Figure 1 It is a schematic diagram of a computed tomography image of the durable metal gel in Example 1 of the present invention;

[0061] Figure 2 It is a schematic diagram of the aqueous polyurethane polymer network extracted from the computed tomography image of the durable metal gel in Example 1 of the present invention and a schematic cross-sectional diagram of the aqueous polyurethane polymer network;

[0062] Figure 3 Schematic diagram of the cross-section structure of the metal gel (a) formed by liquid metal and waterborne polyurethane in Example 1 of the present invention and (b, c, d) element distribution diagrams;

[0063] Figure 4 Schematic diagram of the preparation process of the durable metal gel in the embodiment of the present invention;

[0064] Figure 5 Schematic diagram of the statistical results of the electronic conductivity of the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention;

[0065] Figure 6 Schematic diagram of the stress-strain curve and mechanical durability performance of the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention;

[0066] Figure 7 Schematic diagram of the electrical durability and mass stability performance during cyclic stretching of the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention;

[0067] Figure 8 X-ray diffraction (XRD) patterns of the durable metal gel prepared at different heating temperatures in Example 1 of the present invention and the corresponding volume changes before and after heating;

[0068] Figure 9 Schematic diagram of the cross-section of the durable metal gel prepared at heating temperatures of 25°C and 100°C and the corresponding conductivity performance of the durable metal gels prepared in Examples 1-5;

[0069] Figure 10 Schematic diagram of the cross-section of the durable metal gel prepared at a heating temperature of 120°C;

[0070] Figure 11 Schematic diagram of the microstructure change of the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention during cyclic stretching;

[0071] Figure 12 Fourier transform infrared spectroscopy (FTIR) diagrams of the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention at different temperatures, wide-angle X-ray scattering two-dimensional images (2D-WAXS) at different stretching amounts, and the corresponding crystallinity;

[0072] Figure 13 Schematic diagram of the performance comparison of the conductivity and durability of the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention with other conductive materials;

[0073] Figure 14Schematic diagram of the scenarios where the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention is used in a soft robot to perform lighting, volume change, positioning, and rescue functions;

[0074] Figure 15 Optical photo and current output performance schematic diagram of the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention as the electronic skin of a soft robot during the volume change process;

[0075] Figure 16 Schematic diagram of the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention as the electronic skin of a soft robot using volume change to pass through a slit and complete a rescue task;

[0076] Figure 17 Performance schematic diagram of the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention as the electronic skin of a soft robot to achieve one-dimensional and three-dimensional positioning;

[0077] Figure 18 Performance schematic diagram of the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention for monitoring myoelectric signals during muscle contraction and relaxation. Detailed implementation manners

[0078] The present disclosure can be more easily understood by referring to the following description in combination with examples, all of which form part of the present disclosure. It should be understood that the present disclosure is not limited to the specific products, methods, conditions, or parameters described and / or illustrated herein. Further, the terms used herein are for the purpose of describing specific embodiments by way of example only and are not intended to be limiting unless otherwise specified.

[0079] It should also be understood that, for clarity, certain features of the present disclosure may be described herein in the context of separate embodiments, but may also be provided in combination with each other in a single embodiment. That is, unless clearly incompatible or specifically excluded, each separate embodiment is considered combinable with any other embodiment, and such combination is considered to represent another different embodiment. Conversely, for the sake of brevity, the various features of the present disclosure described in the context of a single embodiment may also be provided separately or in any sub-combination. Finally, although a specific embodiment may be described as part of a series of steps or part of a more general structure, each step or sub-structure itself may also be considered an independent embodiment.

[0080] Unless otherwise specified, it should be understood that each individual element in a list and each combination of individual elements in that list will be construed as a distinct embodiment. For example, a list of embodiments expressed as "A, B, or C" should be construed as including the embodiments "A", "B", "C", "A or B", "A or C", "B or C", or "A, B, or C".

[0081] In the present disclosure, the singular forms of the articles "a", "an", and "the" also include the corresponding plural referents, and a reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. Thus, for example, a reference to "a substance" is a reference to at least one of such substance and its equivalents.

[0082] When items are described by use of the conjunctive term "……and / or……" etc., the description should be understood to include any one of the associated listed items and all combinations of one or more of them.

[0083] Generally, the use of the term "about" indicates an approximation that can vary according to the desired properties obtained from the disclosed subject matter and will be interpreted in a context-dependent manner based on functionality. Thus, one of ordinary skill in the art will be able to interpret a certain degree of variation on a case-by-case basis. In some cases, the number of significant digits used in expressing a particular value can be a representative technique for determining the variation allowed by the term "about". In other cases, a gradient within a series of values can be used to determine the range of variation allowed by the term "about". Further, all ranges in the present disclosure are inclusive and combinable, and a reference to a value within a range includes each value within that range.

[0084] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs; the terms used herein and / or include any and all combinations of one or more of the associated listed items.

[0085] In the following examples, those without specific conditions noted were carried out under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments without the manufacturer indicated were all conventional products that could be obtained by purchasing from the market. Among them, the gallium-indium alloy (Ga 75.50% wt ; In 24.50% wt ), the gallium-indium-tin alloy (Ga 68.50% wt ,; In 21.50% wt ; Sn 10.00% wt ) were purchased from Dongguan Dingyi Metal Co., Ltd., and the aqueous polyurethane dispersion (60.00 wt% solids content) was purchased from Shanghai Macklin Biochemical Co., Ltd.

[0086] The present invention will be further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field. The essential features and remarkable effects of the present invention can be reflected from the following embodiments. The described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Therefore, they do not limit the present invention in any way. Those skilled in the art make some non-essential improvements and adjustments based on the content of the present invention, which all fall within the protection scope of the present invention.

[0087] Example 1

[0088] As Figure 4 shown, this embodiment discloses a preparation method of a durable metal gel, including the following steps:

[0089] Prepare an aqueous polyurethane dispersion:

[0090] Specifically, the steps for preparing the aqueous polyurethane dispersion are as follows: Add 3 times the mass of deionized water to the aqueous polyurethane dispersion with a solid content of 60.00 wt%, and continuously stir magnetically at a temperature of 25 °C until evenly mixed to obtain an aqueous polyurethane dispersion with a solid content of 15.00 wt%;

[0091] Prepare a liquid metal-aqueous polyurethane mixed solution:

[0092] Mix the liquid metal gallium-indium alloy with the aqueous polyurethane dispersion with a solid content of 15.00 wt%. Among them, the mass ratio of the liquid metal to the aqueous polyurethane in the aqueous polyurethane dispersion is 60:1. Then, use a handheld homogenizer to stir and shear at a speed of 10,000 rpm for 5 min at a temperature of 25 °C to obtain a gallium-indium alloy-aqueous polyurethane mixed solution;

[0093] Drying treatment:

[0094] Remove the solvent in an environment of 100 °C:

[0095] Add the obtained liquid metal-aqueous polyurethane mixed solution to a polytetrafluoroethylene watch glass and heat to remove the solvent.

[0096] Specifically, add the obtained liquid metal-aqueous polyurethane mixed solution to a polytetrafluoroethylene watch glass, place it in an environment of 100 °C to remove the solvent, and obtain a durable metal gel prepared at 100 °C.

[0097] Example 2

[0098] Basically the same as Example 1, the difference is only that:

[0099] During the drying process, the solvent was removed in an environment at 25 °C to obtain a durable metal gel.

[0100] Example 3

[0101] Basically the same as Example 1, the only difference is that:

[0102] During the drying process, the solvent was removed in an environment at 40 °C to obtain a durable metal gel.

[0103] Example 4

[0104] Basically the same as Example 1, the only difference is that:

[0105] During the drying process, the solvent was removed in an environment at 80 °C to obtain a durable metal gel.

[0106] Example 5

[0107] Basically the same as Example 1, the only difference is that:

[0108] During the drying process, the solvent was removed in an environment at 120 °C to obtain a durable metal gel.

[0109] The durable metal gels prepared in Examples 1-5 were tested for their electronic conductivity, and the test results are shown in Table 1.

[0110] Table 1 Test results of the electronic conductivity of the durable metal gels prepared in Examples 1-5

[0111] Electronic conductivity (S / m) Example 2 <![CDATA[5.432×10 5 > Example 3 <![CDATA[6.021×10 5 > Example 4 <![CDATA[1.804×10 6 > Example 1 <![CDATA[3.010×10 6 > Example 5 <![CDATA[1.868×10 6 >

[0112] As shown in Table 1, according to Examples 1-5, durable metal gels can be prepared at different heating temperatures. And the prepared durable metal gels all have excellent electronic conductivity.

[0113] Specifically, the electronic conductivity of the durable metal gel material prepared in Example 1 is greater than or equal to 3.00×10 6 S / m, and it can withstand 1 million cycles of cyclic stretching with a 100% tensile amount, achieving a balance between high electronic conductivity and high durability. The cyclic stretching test specimen in Example 1 was prepared according to the ASTM D882 Type 2 specification and the test was completed at a rate of 50 mm / min.

[0114] Combined with Figure 1 - Figure 2 , it can be seen that among them, the liquid metal as the fluid phase in the durable metal gel is a continuous body that is interconnected. Among them, the liquid metal occupies a volume fraction of 71.38%, and the aqueous polyurethane occupies a volume fraction of 28.62%.

[0115] As Figure 3As shown, it is a schematic structural diagram and an elemental distribution map of the cross-section of the metal gel formed by the liquid metal and the waterborne polyurethane in Preparation Example 1 of the present invention, where Figure 3 (a) is a scanning electron microscope (SEM) photograph of the cross-section of the durable metal gel. It can be observed that the liquid metal is connected to form a complete conductive path within the field of view. Through Figure 3 (b, c, d) elemental analysis, it can be found that there are polymer components wrapped by the liquid metal in the photograph. The surface waterborne polyurethane network is evenly dispersed in the liquid metal path, which is consistent with Figure 1 and Figure 2 the results.

[0116] As Figure 5 shown, it is a statistical schematic diagram of the electronic conductivity of the durable metal gel prepared at 100 °C. The conductivity of the durable metal gel prepared at 100 °C has good repeatability, and the highest conductivity can reach 3.10×10 6 S / m.

[0117] As Figure 6 shown, it is a stress-strain curve of the durable metal gel prepared at 100 °C and a schematic diagram of the corresponding mechanical durability performance. The durable metal gel prepared at 100 °C shows a uniaxial tensile amount of 1100%, and there is basically no irreversible deformation after 1 million cycles of 100% tensile amount.

[0118] As Figure 7 shown, it is a schematic diagram of the electrical durability of the durable metal gel prepared at 100 °C and the performance of mass stability during cyclic stretching. The durable metal gel prepared at 100 °C shows excellent electrical durability with only a 3.3% increase in resistance after 1 million cycles of 100% tensile cycling, and the mass remains stable without leakage of the liquid metal.

[0119] As Figure 8 shown, it is an X-ray diffraction (XRD) pattern of the durable metal gel prepared at different heating temperatures in Preparation Example 1 of the present invention and the corresponding volume change before and after heating. Among them, the crystallization peak of the waterborne polyurethane becomes stronger with the increase of the heating temperature, and the volume of the obtained durable metal gel also decreases accordingly, representing an enhanced degree of volume shrinkage.

[0120] As Figure 9 shown, it is a schematic diagram of the cross-section of the durable metal gel prepared at heating temperatures of 25 °C and 100 °C and the corresponding conductivity performance of the durable metal gels prepared at other different heating temperatures. Corresponding to Figure 8 , a stronger crystallization peak corresponds to a greater degree of volume shrinkage, thereby increasing the connectivity of the liquid metal inside the sample and bringing higher electronic conductivity.

[0121] AsFigure 10 As shown, it is a schematic cross-sectional view of a durable metal gel prepared at a heating temperature of 120°C. To explain that the conductivity of the durable metal gel prepared at 120°C is lower than that at 100°C, pores were found in its cross-section by electron microscopy, which may be caused by the rapid evaporation of water at high temperature, damaging the internal conductive pathway.

[0122] As Figure 11 shown, it is a schematic diagram of the change in the microstructure of the durable metal gel obtained from liquid metal and waterborne polyurethane in Preparation Example 1 of the present invention during cyclic stretching. Specifically, the liquid metal continuum undergoes a conformal reversible change with the elastic waterborne polyurethane network under the traction of electrostatic interaction, bringing excellent electronic conductivity and durability to the durable metal gel.

[0123] As Figure 12 shown, it is the Fourier transform infrared spectroscopy (FTIR) of the durable metal gel obtained from liquid metal and waterborne polyurethane in Preparation Example 1 of the present invention at different temperatures, as well as the two-dimensional wide-angle X-ray scattering image (2D-WAXS) and the corresponding crystallinity at different stretching amounts. Specifically, the characteristic peak representing the amino group in the sample showed an obvious reversible shift during the process of heating from 30°C to 150°C and cooling from 150°C to 30°C, which proves that the polymer network of the sample contains abundant dynamic reversible hydrogen bonds. The 2D-WAXS image showed an obvious transformation from isotropic circles to anisotropic circles during stretching to 300%, and quickly recovered after release. These are the sources of the excellent mechanical properties of the elastic waterborne polyurethane network.

[0124] As Figure 13 shown, the conductivity and durability of the durable metal gel prepared at 100°C far exceed the performance of other conductive materials.

[0125] As Figure 14 shown, it is a schematic diagram of the scenario where the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention is used in a soft robot to perform lighting, volume change, positioning, and rescue functions.

[0126] As Figure 15 shown, it is a schematic diagram of the optical photo and current output performance of the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention as a soft robot electronic skin during volume change. Specifically, during the repeated deformation of the robotic pufferfish, the output current amplitude of the sample as the electronic skin is only within 3 mA.

[0127] As Figure 16 shown, it is a schematic diagram of the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention as a soft robot electronic skin using volume change to pass through a slit and complete a rescue mission.

[0128] As Figure 17 shown, it is a schematic diagram of the performance of the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention for realizing one-dimensional and three-dimensional positioning as a soft robot electronic skin. Specifically, using the durable metal gel as an electrode can prepare a pressure sensor with sensitive performance to sense water pressure and obtain the depth information of the robotic pufferfish. Combining with the GPS device integrated on the electronic skin, we can obtain the three-dimensional positioning information of the robotic pufferfish.

[0129] As Figure 18 shown, it is a schematic diagram of the performance of the durable metal gel obtained from liquid metal and waterborne polyurethane in Example 1 of the present invention for monitoring electromyographic signals during muscle contraction and relaxation. Specifically, the excellent conductivity of the durable metal gel provides a performance basis for the high sensitivity of electromyographic signal monitoring. Its excellent durability can ensure that the electrode maintains stable performance during repeated elbow extension and flexion processes, and the signals before and after 1000 times of elbow flexion are almost the same.

[0130] In summary, the liquid metals penetrate each other throughout the material to form a continuous phase, providing a good electronic path for the durable metal gel. The durable metal gel has an electronic conductivity close to that of metals. The elastic waterborne polyurethane polymer network presents a continuous three-dimensional porous structure, providing good mechanical support for the durable metal gel and having excellent durability. The uniaxial elongation reaches 1100%, and it can withstand 1 million times of 100% tensile cycles. There is an electrostatic interaction between the waterborne polyurethane polymer network and the liquid metal, fixing the liquid metal in the elastic waterborne polyurethane polymer network and ensuring that the liquid metal does not leak. A stable interface is formed between the components, enabling the material to have excellent durability while having good electronic conductivity.

[0131] Example 6

[0132] Basically the same as Example 1, the difference is only that:

[0133] In the preparation of the liquid metal-waterborne polyurethane mixed solution, the liquid metal gallium-indium-tin alloy is mixed with a waterborne polyurethane dispersion with a solid content of 15.00 wt%, wherein the mass ratio of the liquid metal to the waterborne polyurethane in the waterborne polyurethane dispersion is 60:1, obtaining a gallium-indium-tin alloy-waterborne polyurethane mixed solution.

[0134] Example 7

[0135] Basically the same as Example 1, the difference is only that:

[0136] In the preparation of the liquid metal-aqueous polyurethane mixed solution, the liquid metal gallium-indium alloy is mixed with an aqueous polyurethane dispersion with a solid content of 15.00 wt%, wherein the mass ratio of the liquid metal to the aqueous polyurethane in the aqueous polyurethane dispersion is 10:1, and a gallium-indium alloy-aqueous polyurethane mixed solution is obtained.

[0137] Example 8

[0138] Basically the same as Example 1, the only difference is that:

[0139] In the preparation of the liquid metal-aqueous polyurethane mixed solution, the liquid metal gallium-indium alloy is mixed with an aqueous polyurethane dispersion with a solid content of 15.00 wt%, wherein the mass ratio of the liquid metal to the aqueous polyurethane in the aqueous polyurethane dispersion is 20:1, and a gallium-indium alloy-aqueous polyurethane mixed solution is obtained.

[0140] Example 9

[0141] Basically the same as Example 1, the only difference is that:

[0142] In the preparation of the liquid metal-aqueous polyurethane mixed solution, the liquid metal gallium-indium alloy is mixed with an aqueous polyurethane dispersion with a solid content of 15.00 wt%, wherein the mass ratio of the liquid metal to the aqueous polyurethane in the aqueous polyurethane dispersion is 35:1, and a gallium-indium alloy-aqueous polyurethane mixed solution is obtained.

[0143] Comparative Example 1

[0144] Basically the same as Example 1, the only difference is that:

[0145] In the preparation of the liquid metal-aqueous polyurethane mixed solution, the liquid metal gallium-indium alloy is mixed with an aqueous polyurethane dispersion with a solid content of 15.00 wt%, wherein the mass ratio of the liquid metal to the aqueous polyurethane in the aqueous polyurethane dispersion is 10:3, and a gallium-indium alloy-aqueous polyurethane mixed solution is obtained.

[0146] Comparative Example 2

[0147] Basically the same as Example 1, the only difference is that:

[0148] Preparation of the liquid metal-aqueous polyurethane mixed solution:

[0149] The liquid metal gallium-indium alloy is mixed with an aqueous polyurethane dispersion with a solid content of 15.00 wt%, wherein the mass ratio of the liquid metal to the aqueous polyurethane in the aqueous polyurethane dispersion is 80:1, and a gallium-indium alloy-aqueous polyurethane mixed solution is obtained;

[0150] Drying treatment:

[0151] Removing the solvent in an environment of 100 °C:

[0152] The obtained liquid metal-aqueous polyurethane mixed solution was added to a polytetrafluoroethylene petri dish, and the solvent was removed by heating.

[0153] Specifically, the obtained liquid metal-aqueous polyurethane mixed solution was added to a polytetrafluoroethylene petri dish and placed in an environment at 100 °C to remove the solvent. Due to the too high content of liquid metal, the mixed solution could not be formed after drying, and a self-supporting metal gel sample could not be obtained.

[0154] The durable metal gels prepared in Examples 6-9 and Comparative Example 1 were tested for electronic conductivity, and the test results are shown in Table 2.

[0155] Table 2 Test results of durable metal gels prepared in different examples and comparative examples

[0156]

[0157]

[0158] As shown in Table 2, the performance of the samples prepared from the gallium-indium-tin alloy was basically the same as that of the gallium-indium alloy. The electrical conductivity of the metal gel increased with the increase in the proportion of liquid metal. When the mass ratio of liquid metal to aqueous polyurethane was less than 10:1, the sample was basically insulating; when the mass ratio of liquid metal to aqueous polyurethane was higher than 60:1, a formable metal gel could not be prepared.

Claims

1. A method for preparing a durable metal gel, characterized in that: The following steps are involved: S1. Preparation of a liquid metal - aqueous polyurethane mixed solution: mixing and dispersing the liquid metal and the aqueous polyurethane dispersion to obtain a liquid metal - aqueous polyurethane mixed solution; S2. Drying treatment: Drying the liquid metal-aqueous polyurethane mixed solution to obtain a durable metal gel.

2. The method for preparing the durable metal gel according to claim 1, characterized in that: In step S1, the mass ratio of the liquid metal to the aqueous polyurethane in the aqueous polyurethane dispersion is (10-60):

1.

3. The method for preparing the durable metal gel according to claim 1, characterized in that: The waterborne polyurethane includes carboxylic acid type waterborne polyurethane; The liquid metal includes at least one of metallic gallium, gallium-indium alloy, and gallium-indium-tin alloy.

4. The method for preparing the durable metal gel according to claim 3, characterized in that: The mass fraction of gallium in the gallium-indium alloy is greater than or equal to 75.50%, and the mass fraction of indium is less than or equal to 24.5%; and / or, The mass ratio of gallium, indium and tin in the gallium-indium-tin alloy is 68.50:21.50:10.

00.

5. The method for preparing the durable metal gel according to any one of claims 1 to 4, characterized in that: In step S2, the drying process conditions include: a temperature of 25 to 120°C.

6. The method for preparing the durable metal gel according to claim 5, characterized in that: In step S1, the solid content of the aqueous polyurethane dispersion is 10 wt% to 60 wt%.

7. The method for preparing the durable metal gel according to claim 6, characterized in that: In step S1, the mixing and dispersing conditions include: a stirring speed of 8000 rpm to 15000 rpm, and a stirring time of 3 min to 10 min.

8. A durable metal gel prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The durable metal gel comprises liquid metal and waterborne polyurethane, wherein the liquid metal is dispersed in the waterborne polyurethane.

9. The durable metal gel according to claim 8, characterized in that: The electronic conductivity of the durable metal gel is greater than or equal to 5.00×10 5 S / m.

10. A flexible electronic product comprising the durable metal gel according to claim 8 or 9.

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