Multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal and preparation method thereof

Abstract

The invention provides a multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal and a preparation method. The preparation method comprises the following steps: firstly preparing ionic liquid gel with excellent performance as an upper substrate and a lower substrate of the flexible electronic device, then forming a high-resolution conductive pattern on the ionic liquid gel through a template printing method by using liquid metal alloy subjected to surface modification, and finally curing and packaging by using another layer of ionic liquid gel. According to the flexible electronic device, the modified particles are introduced to be mixed with the liquid metal, the flexible electronic device with the tensile adjustable resistance change characteristic is prepared, and meanwhile, the conductive patterns form firm interface bonding with the gel matrix through hydrogen bonds formed between the gallium with the oxidized surface and carboxyl of the ionic gel. Even if the prepared multifunctional flexible electronic device is stretched and released, the composite material can keep continuous contact with the base material, so that stable electric connection is maintained, and the method is suitable for the fields of wearable electronics and flexible electronics.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible electronic device preparation, and particularly relates to a multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal and a preparation method thereof. Background Art

[0002] With the gradual maturity of technology, flexible electronic components exhibit sufficient elasticity to adapt to various irregular changes, including bending, stretching, and twisting. Therefore, such devices are gradually entering the public life and showing broad application prospects in fields such as healthcare, information technology, and energy. Especially in the aspects of intelligent flexible sensors, electronic skin, flexible energy storage, and soft robotics technology, they have great application potential.

[0003] In the process of developing these flexible and soft electronic products, it is crucial to find a stretchable conductor material that not only has high conductivity but also is easy to integrate with elastic substrate materials. Recently, gallium-based room temperature liquid metals (LMs) have been recognized as ideal conductors for flexible electronic devices due to their excellent conductivity, infinite deformability, and low toxicity. By adding metal microparticles or elastic polymer materials such as polydimethylsiloxane (PDMS), silica gel (Eco-flex), polyurethane (PU), and hydrogel to liquid metal composites, the performance of flexible and stretchable electronic products can be improved. However, these materials often have problems such as insufficient mechanical strength and toughness, low conductivity, and weak self-healing ability, and are prone to failure especially in extreme environments (such as low temperature, high temperature, or vacuum conditions), which limits their durability in practical applications.

[0004] In view of this, it is necessary to design a multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal and a preparation method thereof to solve the above problems. Summary of the Invention

[0005] The present application provides a preparation method of a multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal. The preparation method first prepares an ionic liquid gel with excellent properties as the upper and lower substrates of the flexible electronic device. Then, the surface-modified liquid metal alloy is formed into a high-resolution conductive pattern on the ionic liquid gel by template printing method. Finally, it is cured and encapsulated with another layer of ionic liquid gel. This design enables the prepared flexible electronic device to achieve excellent mechanical ductility and multifunctionality while maintaining the integrity of the circuit, and is applicable to the fields of wearable electronics and flexible electronics.

[0006] In the first aspect, an embodiment of the present application provides a preparation method of a multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal, including the following steps:

[0007] S1. Mix the polymer monomer and the ionic liquid in proportion to form a uniform first mixed solution. Then, add a modifier, a crosslinking agent, and a photoinitiator to the first mixed solution to obtain a second mixed solution. Under the action of irradiation, the polymer monomer in the second mixed solution polymerizes to obtain an ionic liquid gel.

[0008] S2. Mix the liquid metal and the modified particles to form a highly conductive liquid metal alloy with printability and adjustable tensile resistance.

[0009] S3. Using a screen printing template, coat the highly conductive liquid metal alloy obtained in step S2 on the ionic liquid gel obtained in step S1 to obtain a conductive coating with a specific pattern and a resolution of 1 - 10 microns.

[0010] S4. On the basis of step S3, drop the uncured second mixed solution to cover the conductive coating to cure and seal the ionic liquid gel covering the conductive trace, obtaining a flexible electronic device with excellent performance.

[0011] Further, in the first mixed solution, the mass percentage of the polymer monomer is 40wt% - 60wt%, and the mass percentage of the ionic liquid is 40wt% - 60wt%.

[0012] Further, in the second mixed solution, the content of the modifier is 1% - 10% of the content of the polymer monomer, the content of the crosslinking agent is 0.1% - 0.3% of the content of the polymer monomer, and the content of the photoinitiator is 1% - 3% of the content of the polymer monomer.

[0013] Further, the modified particles are iron powder, copper powder, titanium dioxide, zirconium dioxide, aluminum oxide, or silicon dioxide, and the particle size of the modified particles is 20 - 500 nm.

[0014] Further, in step S2, in the highly conductive liquid metal alloy, the content of the modified particles is 5wt% - 20wt%.

[0015] Further, the modifier is one of cellulose, metal - organic framework, covalent - organic framework, graphene nanosheets, carbon nanotubes, silicon dioxide, cellulose nanocrystals, and graphene oxide.

[0016] Further, the polymer monomer is one of acrylic acid (AA), butyl acrylate (BA), methyl methacrylate (MMA), acrylamide (AM), N-isopropylacrylamide (NIPAM), and ethylene glycol diacrylate (EGDA); the ionic liquid includes at least one of imidazole-based ionic liquids, guanidine-based ionic liquids, quaternary ammonium-based ionic liquids, pyrrolidine-based ionic liquids, piperidine-based ionic liquids, and pyridine-based ionic liquids; further, the ionic liquid includes one of 1-ethyl-3-methylimidazolium diethyl phosphate, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium dicyanamide, tributylmethylammonium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium tetrafluoroborate, and 1-butyl-3-methylimidazolium hexafluorophosphate.

[0017] Further, the cross-linking agent is one of N,N'-methylenebisacrylamide (MBAA), 1,4-butanediol diacrylate (BDDA), divinylbenzene (DVB), polyethylene glycol diacrylate 600 (PEGDA600), and polyethylene glycol diacrylate 1000 (PEGDA1000); the photoinitiator includes at least one of benzoin and its derivatives, benzil and its derivatives, acetophenone derivatives, α-hydroxy ketone derivatives, α-amino ketone derivatives, acylphosphine oxides, benzophenone and its derivatives, thioxanthone and its derivatives, and anthraquinone and its derivatives.

[0018] Further, the liquid metal is gallium indium alloy, gallium indium tin alloy; wherein, the proportion of each component in the alloy is: 62% - 95% of gallium, 5 - 22% of indium, and 0 - 16% of tin.

[0019] In a second aspect, the embodiments of the present application provide a multifunctional flexible electronic device based on an ionic liquid gel and patterned liquid metal, which is prepared by any one of the foregoing technical solutions. The multifunctional flexible electronic device includes upper and lower base layers and a liquid metal alloy layer formed between the upper and lower base layers; the upper and lower base layers are ionic gel layers.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The preparation method of the multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal provided by this application. When preparing the ionic gel substrate, this application introduces a modifier into the polymer network to further improve the mechanical properties of the polymer. The hydrogen bond interaction between the polymer network and the modifier helps to form a dynamic viscoelastic network with high transparency and adjustable mechanical properties, and an ionic gel substrate with various excellent properties is prepared. Then, a conductive pattern is formed on the ionic gel substrate. This application prepares a flexible electronic device with stretchable adjustable resistance change characteristics by introducing modified particles and mixing them with liquid metal. At the same time, the conductive pattern forms a strong interfacial bond with the gel matrix by forming hydrogen bonds between the surface-oxidized gallium (Ga2O3) and the carboxyl group of the ionic gel, which can effectively promote the penetration of liquid metal and its alloys on the matrix and ensure the conductive stability of the substrate under high deformation. This bonding method enables the composite material to maintain continuous contact with the substrate even during the stretching and releasing processes, thus maintaining a stable electrical connection.

[0022] (2) The multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal prepared by this application has better super-stretchability (the film has ultra-high stretchability > 1500%), good self-healing ability, high elasticity, self-adhesion, and good temperature sensitivity even in extremely harsh environments compared with conventional conductive flexible electronic devices. At the same time, this flexible electronic device also has the characteristic of adjustable stretch resistance.

[0023] (3) In this application, a liquid metal alloy is introduced as an intermediate layer. By doping specific modified particles in the liquid metal, on the one hand, the chemical and physical adhesion synergy with the ionic gel is achieved, and on the other hand, the stretch resistance change of the liquid metal on the ionic gel substrate is effectively regulated, and then a flexible electronic device with stretchable adjustable resistance change characteristics is prepared.

[0024] Specifically, the doping of different types of modified particles has a differential impact on the conductive stability of the composite material. The introduction of inorganic particles such as Al2O3 and SiO2 significantly enhances the overall stability of the composite material. The addition of these inorganic particles moderately increases the overall resistance of the composite alloy, promotes the formation of a porous conductive network with embedded nanoparticles inside, avoids the drastic fluctuation of resistivity caused by too small resistance and cross-sectional area changes, and ensures that the material can still maintain a stable resistance change under high stretching and cyclic stretching conditions. In contrast, the addition of highly conductive particles such as Fe and Cu effectively reduces the high surface tension of the liquid metal (LM) after mechanochemical treatment, thereby enhancing the stability of the alloy surface. At the same time, it does not affect the resistance sensitivity of the liquid metal itself to stretching changes, enabling it to still sensitively reflect the resistance change during the stretching process.

[0025] (4) The present application uses a sandwich structure design to encapsulate the conductive intermediate layer between two layers of ionic liquid gel substrates. This structure can maintain the electrical stability of the intermediate patterned conductive traces and prevent leakage of conductive materials when undergoing extreme mechanical deformations such as high tension, torsion and compression.

[0026] (5) The sandwich structure composite material prepared by the present invention is simple to form and easy to operate. The combination of ionic liquid gel and printable liquid metal is a strategy for developing adjustable flexible electronic devices with multiple functions, while achieving better human-computer interaction; it broadens the application scope of flexible electronic devices in electronic skin, smart sensors, wearable electronic devices, and soft robots.

[0027] (6) The present application uses a specially made perforated mask for template printing, which can easily produce complex conductive patterns.

[0028] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 It is a schematic flow chart of the method for preparing multifunctional flexible electronic devices based on ionic liquid gel and patterned liquid metal of the present invention.

[0031] Figure 2 This is a physical picture of the multifunctional flexible electronic devices with different patterns prepared by the present invention.

[0032] Figure 3 Schematic diagram of the self-repairing properties of the multifunctional flexible electronic device prepared in Example 1.

[0033] Figure 4 Schematic diagram of the flexibility characteristics of the multifunctional flexible electronic device prepared in Example 1.

[0034] Figure 5 Schematic diagram of the high adhesion characteristics of the multifunctional flexible electronic device prepared in Example 1.

[0035] Figure 6Thermal imaging of the multifunctional flexible electronic device prepared in Example 1 at -25°C was taken at room temperature. Therefore, the actual temperature is slightly increased due to the influence of the ambient temperature.

[0036] Figure 7 Stress-strain curves of the multifunctional flexible electronic devices based on ionic liquid gels and patterned liquid metals in Examples 1-4 and Comparative Example 1.

[0037] Figure 8 Relative resistance change of the multifunctional flexible electronic devices prepared in Example 1 and Comparative Example 4.

[0038] Figure 9 Relative resistance change of the flexible device of the multifunctional flexible electronic device based on ionic liquid gels and patterned liquid metals prepared in Example 1 under cyclic stretching at 100% strain in air (150 cycles). Detailed implementation manners

[0039] Embodiments of the technical solutions of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solutions of the present application more clearly, so they are only examples and cannot be used to limit the protection scope of the present application.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above accompanying drawings are intended to cover non-exclusive inclusion.

[0041] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality" is more than two, unless otherwise clearly and specifically defined.

[0042] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0043] In the description of the embodiments of the present application, the term "and / or" is merely a description of the association relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Additionally, in this text, the character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0044] In the description of the embodiments of the present application, the term "a plurality of" refers to two or more (including two). Similarly, "a plurality of groups" refers to two or more groups (including two groups), and "a plurality of sheets" refers to two or more sheets (including two sheets).

[0045] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific situations.

[0046] The embodiments of the present application provide a preparation method for a multifunctional flexible electronic device based on an ionic liquid gel and a patterned liquid metal, including the following steps:

[0047] S1, mixing a polymer monomer and an ionic liquid in proportion to form a uniform first mixed solution; then, adding a modifier, a crosslinking agent, and a photoinitiator to the first mixed solution to obtain a second mixed solution; under the action of irradiation, the polymer monomer in the second mixed solution polymerizes to obtain an ionic liquid gel;

[0048] Among them, in the first mixed solution, the mass percentage of the polymer monomer is 40wt%-60wt%, and the mass percentage of the ionic liquid is 40wt%-60wt%.

[0049] In the second mixed solution, the content of the modifier is 1%-10% of the content of the polymer monomer, the content of the crosslinking agent is 0.1%-0.3% of the content of the polymer monomer, and the content of the photoinitiator is 1%-3% of the content of the polymer monomer.

[0050] The polymer monomer is one of acrylic acid (AA), butyl acrylate (BA), methyl methacrylate (MMA), acrylamide (AM), N-isopropylacrylamide (NIPAM), and ethylene glycol diacrylate (EGDA); the ionic liquid includes at least one of imidazole-based ionic liquids, guanidine-based ionic liquids, quaternary ammonium-based ionic liquids, pyrrolidine-based ionic liquids, piperidine-based ionic liquids, and pyridine-based ionic liquids; further, the ionic liquid includes one of 1-ethyl-3-methylimidazolium diethyl phosphate, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium dicyanamide, tributylmethylammonium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium tetrafluoroborate, or 1-butyl-3-methylimidazolium hexafluorophosphate.

[0051] The modifier is one of cellulose, metal-organic frameworks, covalent organic frameworks, graphene nanosheets, carbon nanotubes, silica, cellulose nanocrystals, and graphene oxide; the crosslinking agent is one of N,N'-methylenebisacrylamide (MBAA), 1,4-butanediol diacrylate (BDDA), divinylbenzene (DVB), polyethylene glycol diacrylate 600 (PEGDA600), and polyethylene glycol diacrylate 1000 (PEGDA1000); the photoinitiator includes at least one of benzoin and its derivatives, benzil and its derivatives, acetophenone derivatives, α-hydroxy ketone derivatives, α-amino ketone derivatives, acylphosphine oxides, benzophenone and its derivatives, thioxanthone and its derivatives, and anthraquinone and its derivatives.

[0052] S2. Mix the liquid metal with the modified particles to form a highly conductive liquid metal alloy with printability and adjustable tensile resistance.

[0053] Among them, in the highly conductive liquid metal alloy, the content of the modified particles is 5wt% - 20wt%.

[0054] The liquid metal is a gallium-indium alloy or a gallium-indium-tin alloy; among them, the proportion of each component in the alloy is: 62% - 95% gallium, 5 - 22% indium, and 0 - 16% tin.

[0055] The modified particles are iron powder, copper powder, titanium dioxide, zirconium dioxide, aluminum oxide, and silica, and the particle size of the modified particles is 20 - 500nm.

[0056] S3. Using a screen printing template, coat the highly conductive liquid metal alloy obtained in step S2 on the ionic liquid gel obtained in step S1 to obtain a conductive coating with specific patterning and a resolution of 1 - 10 microns.

[0057] S4. Based on step S3, drop the uncured second mixed solution to cover the conductive layer, so as to cure and seal the ionic liquid gel covering the conductive trace, and obtain a flexible electronic device with excellent performance.

[0058] Second, the embodiments of the present application provide a multifunctional flexible electronic device based on an ionic liquid gel and patterned liquid metal, which is prepared by the foregoing technical solutions. The multifunctional flexible electronic device includes upper and lower base layers and a liquid metal alloy layer formed between the upper and lower base layers; the upper and lower base layers are ionic gel layers.

[0059] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those without specific technologies or conditions noted in the embodiments, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For reagents or instruments without the manufacturer noted, they are all conventional products that can be obtained through commercial procurement.

[0060] I. Preparation method

[0061] Example 1

[0062] Please refer to Figure 1 As shown, this embodiment provides a preparation method of a multifunctional flexible electronic device based on an ionic liquid gel and patterned liquid metal, including the following steps:

[0063] S1. Mix the polymer monomer acrylic acid (AA) and the ionic liquid 1-ethyl-3-methylimidazolium diethyl phosphate ([EMIM][DEP]) in proportion to prepare a uniform first mixed solution; then, add the modifier hydroxypropyl cellulose, the crosslinking agent N-methylenebisacrylamide, and the photoinitiator (1-hydroxycyclohexyl phenyl ketone) to the first mixed solution, and stir magnetically at 60-70 °C for 2-3 h to obtain a uniform and transparent mixed solution (second mixed solution); then, irradiate (power 35 W, wavelength 365 nm) for 5 min to polymerize the polymer monomers in the second mixed solution to obtain an ionic liquid gel;

[0064] Among them, in the first mixed solution, the mass percentage of the ionic liquid [EMIM][DEP] is 50 wt%.

[0065] In the second mixed solution, the content of the modifier is 5.0% of the content of the polymer monomer, the content of the crosslinking agent is 0.3% of the content of the polymer monomer, and the content of the photoinitiator is 1.0% of the content of the polymer monomer.

[0066] S2. Strongly mix liquid metal (LM) and modified particles Al2O3 in a mortar to form a highly conductive liquid metal alloy with good printability and adjustable tensile resistance. Among them, the liquid metal is a gallium-indium-tin alloy, and the proportion of each component in the alloy is: 62% gallium, 22% indium, and 16% tin.

[0067] In the highly conductive liquid metal alloy, the content of Al2O3 is 16.7 wt% (corresponding to a mass ratio of Al2O3 / LM of 1:5).

[0068] S3. Obtain a silhouette film with a specific pattern by laser cutting a TPU transparent film. After placing the template mask on the ionic gel film, pour the liquid metal alloy prepared in step S2 onto the template mask and coat it with a brush. Then, peel off the template mask, that is, a conductive layer with a specific pattern and a resolution of 1-10 microns is formed on the ionic gel surface.

[0069] S4. On the basis of step S3, drop a small amount of uncured second mixed solution to cover the conductive layer (patterned circuit) to cure and seal the ionic liquid gel covering the conductive trace, and obtain a flexible electronic device with excellent performance. The physical diagram is as Figure 2 shown.

[0070] Figure 3 It is a schematic diagram of the self-healing property of the multifunctional flexible electronic device prepared in this embodiment. As shown in the figure, when two independent parts come into contact with each other in a natural environment, they will quickly and seamlessly combine together, light up the red small light bulb, indicating that it has good self-healing properties.

[0071] Figure 4 It is a schematic diagram of the flexible property of the multifunctional flexible electronic device prepared in this embodiment. It can be seen that in various deformations (tensile, torsion, bending, knotting), the flexible electronic device shows excellent high toughness.

[0072] Figure 5 It is a schematic diagram of the high adhesion property of the multifunctional flexible electronic device prepared in Example 1 of this embodiment. It can be seen that the flexible electronic device can adhere to various substrates, demonstrating excellent adhesion.

[0073] Figure 6 It is a schematic diagram of the excellent thermal stability property of the multifunctional flexible electronic device prepared in Example 1 of the present invention. As shown in the figure, it still has flexibility at low temperature (-25°C) (because it is photographed at room temperature, the actual displayed temperature is affected by the ambient temperature and slightly increases).

[0074] Examples 2-4 and Comparative Examples 1-3

[0075] Examples 2-4 and Comparative Examples 1-3 provide a method for preparing a multifunctional flexible electronic device based on an ionic liquid gel and patterned liquid metal. Compared with Example 1, the difference lies in that the mass percentage of the ionic liquid [EMIM][DEP] in step S1 is changed, as shown in the following table. The rest is substantially the same as in Example 1 and will not be elaborated here.

[0076]

[0077] It can be seen from the experiments that when the mass percentage of the ionic liquid [EMIM][DEP] is higher than 60% (Comparative Example 2), due to the too high concentration of the ionic liquid, the monomer concentration is significantly reduced, thus inhibiting the polymerization reaction of the monomer, resulting in a sharp drop in the stress of the prepared gel. When the mass percentage of the ionic liquid [EMIM][DEP] is lower than 40% (Comparative Example 3), the ionic liquid concentration is too low, and the ionic bond energy between the monomers is relatively weak. This not only results in a lower stress of the gel, but also makes the strain value relatively low.

[0078] Tensile tests were carried out on the ionic liquid gels composed of different amounts of AA and ionic liquid (IL) in Examples 1-4 and Comparative Example 1, and the test results are as Figure 7 shown. It can be seen that when the ionic liquid concentration is 50%, the mechanical properties of the ionic liquid gel are the best, and the corresponding fracture stress / strain is 2000 KPa / 1370%. In Example 2, due to the relatively low ionic liquid concentration, the ionic bond energy between the monomers is relatively weak. Therefore, the stress of the gel is relatively reduced, and at the same time, the strain value is also relatively low (only relative to Example 1). In Example 4, due to the increase in the ionic liquid concentration, the monomer concentration is significantly reduced, thus inhibiting the polymerization reaction of the monomer. Therefore, the stress of the prepared gel has decreased (only relative to Example 1). However, compared with Comparative Example 1 without ionic liquid added, both the stress and strain have been greatly improved.

[0079] Comparative Example 4

[0080] Compared with Example 1, the main difference in Comparative Example 4 is that in step S2, the modified particles Al2O3 are not used, and the rest is substantially the same as in Example 1 and will not be elaborated here.

[0081] The relative resistance changes of the flexible electronic devices prepared in Example 1 and Comparative Example 4 were tested, and the test results are as Figure 8As shown, it can be seen that since the conductive paste in the flexible electronic device prepared in Comparative Example 4 is pure liquid metal, the resistivity changes greatly with the increase of strain during stretching, while the conductive paste in the flexible electronic device prepared in Example 1 is a liquid metal alloy added with modified particles, and its resistance change rate is relatively stable with the increase of strain during stretching, indicating that the flexible electronic device prepared in Example 1 has the characteristic of adjustable stretching resistance.

[0082] The relative resistance change of the flexible electronic device prepared in Example 1 was tested under cyclic stretching (150 cycles) at 100% strain in air, and the test results are as Figure 9 shown. It can be seen that the resistance of this flexible electronic device remains stable under high cycles.

[0083] Examples 5-11 and Comparative Examples 5-6

[0084] Examples 5-11 and Comparative Examples 5-6 provide a preparation method of a multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal. Compared with Example 1, the difference is that in step S2, the modified particles and the mass percentage of the modified particles in the conductive liquid metal alloy are changed, as shown in the following table. The rest is roughly the same as that of Example 1 and will not be elaborated here.

[0085]

[0086]

[0087] It can be known from experiments that when the mass percentage of the modified particles is higher than 20%, the stretching resistance change rate is lower than 15%. However, due to the too high content of the modified particles, the fluidity of the conductive paste gradually decreases, and finally becomes solid or semi-solid, resulting in a decrease in its adhesion, unable to be printed, and the conductivity is discontinuous. When the mass percentage of the modified particles is lower than 5%, the stretching resistance change rate is larger. Generally speaking, it is more appropriate to select the mass percentage of the modified particles to be 5wt% - 20wt%.

[0088] It can be known from experiments that the introduction of inorganic particles such as Al2O3 and SiO2 significantly enhances the overall stability of the composite material. The addition of these inorganic particles moderately increases the overall resistance of the composite alloy, promotes the formation of a porous conductive network with embedded nanoparticles inside, avoids the drastic fluctuation of resistivity caused by too small resistance and cross-sectional area change, and ensures that the material can still maintain a stable resistance change under high stretching and cyclic stretching conditions. In contrast, the addition of highly conductive particles such as Fe and Cu effectively reduces the high surface tension of the liquid metal (LM) after mechanochemical treatment, thereby enhancing the surface stability of the alloy. At the same time, it does not affect the resistance sensitivity of the liquid metal itself to stretching changes, enabling it to still sensitively reflect the resistance change during stretching.

[0089] It can be known from experiments that the polymer monomer can also be one of butyl acrylate (BA), methyl methacrylate (MMA), acrylamide (AM), N-isopropylacrylamide (NIPAM), and ethylene glycol diacrylate (EGDA).

[0090] The ionic liquid can also be at least one of guanidine-based ionic liquids, quaternary ammonium-based ionic liquids, pyrrolidine-based ionic liquids, piperidine-based ionic liquids, and pyridine-based ionic liquids; for example, the ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium dicyanamide, tributylmethylammonium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium tetrafluoroborate, and 1-butyl-3-methylimidazolium hexafluorophosphate.

[0091] The modifier can also be one of metal-organic frameworks, covalent organic frameworks, graphene nanosheets, carbon nanotubes, silica, cellulose nanocrystals, and graphene oxide.

[0092] The crosslinking agent can also be one of 1,4-butanediol diacrylate (BDDA), divinylbenzene (DVB), polyethylene glycol diacrylate 600 (PEGDA600), and polyethylene glycol diacrylate 1000 (PEGDA1000).

[0093] The photoinitiator can also be at least one of benzoin and its derivatives, benzil and its derivatives, acetophenone derivatives, α-hydroxy ketone derivatives, α-amino ketone derivatives, acylphosphine oxides, benzophenone and its derivatives, thioxanthone and its derivatives, and anthraquinone and its derivatives.

[0094] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same composition and the same effect as the technical idea within the scope of the technical solution of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that can be thought of by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A preparation method of a multifunctional flexible electronic device based on an ionic liquid gel and a patterned liquid metal, characterized in that It includes the following steps: S1. Mix the polymer monomer and the ionic liquid in proportion to prepare a uniform first mixed solution; Then, add a modifier, a crosslinking agent and a photoinitiator to the first mixed solution to obtain a second mixed solution; under the action of irradiation, the polymer monomer in the second mixed solution polymerizes to obtain an ionic liquid gel; S2. Mix the liquid metal and the modified particles to form a highly conductive liquid metal alloy with adjustable printability and tensile resistance; S3. Using a screen printing template, coat the highly conductive liquid metal alloy obtained in step S2 on the ionic liquid gel obtained in step S1 to obtain a conductive coating layer with specific patterning and a resolution of 1 to 10 microns; S4. On the basis of step S3, drop the uncured second mixed solution to cover the conductive coating layer to cure and seal the ionic liquid gel covering the conductive trace, and obtain a flexible electronic device with excellent performance.

2. The preparation method of the multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal according to claim 1, wherein, In the first mixed solution, the mass percentage of the polymer monomer is 40wt%-60wt%, and the mass percentage of the ionic liquid is 40wt%-60wt%.

3. The preparation method of the multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal according to claim 1, wherein In the second mixed solution, the content of the modifier is 1%-10% of the content of the polymer monomer, the content of the crosslinking agent is 0.1%-0.3% of the content of the polymer monomer, and the content of the photoinitiator is 1%-3% of the content of the polymer monomer.

4. The preparation method of the multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal according to claim 1, wherein, The modified particles are iron powder, copper powder, titanium dioxide, zirconium dioxide, aluminum oxide or silicon dioxide, and the particle size of the modified particles is 20-500nm.

5. The preparation method of the multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal according to claim 1, characterized in that, In step S2, in the highly conductive liquid metal alloy, the content of the modified particles is 5wt% to 20wt%.

6. The preparation method of the multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal according to claim 1, wherein, The modifier is one of cellulose, metal-organic framework, covalent organic framework, graphene nanosheets, carbon nanotubes, silicon dioxide, cellulose nanocrystals, graphene oxide.

7. The preparation method of the multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal according to claim 1, characterized in that, The polymer monomer is one of acrylic acid, butyl acrylate, methyl methacrylate, acrylamide, N-isopropylacrylamide and ethylene glycol diacrylate; the ionic liquid includes at least one of imidazole ionic liquids, guanidine ionic liquids, quaternary ammonium ionic liquids, pyrrolidine ionic liquids, piperidine ionic liquids and pyridine ionic liquids; further, the ionic liquid includes one of 1-ethyl-3-methylimidazolium diethyl phosphate, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium dicyanamide, tributylmethylammonium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium tetrafluoroborate or 1-butyl-3-methylimidazolium hexafluorophosphate.

8. The preparation method of the multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal according to claim 1, characterized in that, The crosslinking agent is one of N,N'-methylenebisacrylamide, 1,4-butanediol diacrylate, divinylbenzene, polyethylene glycol diacrylate 600, and polyethylene glycol diacrylate 1000; the photoinitiator includes at least one of benzoin and its derivatives, benzil and its derivatives, acetophenone derivatives, α-hydroxy ketone derivatives, α-amino ketone derivatives, acylphosphine oxides, benzophenone and its derivatives, thioxanthone and its derivatives, and anthraquinone and its derivatives.

9. The preparation method of the multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal according to claim 1, wherein The liquid metal is a gallium-indium alloy or a gallium-indium-tin alloy; wherein, the proportion of each component in the alloy is: 62% to 95% of gallium, 5 to 22% of indium, and 0 to 16% of tin.

10. A multifunctional flexible electronic device based on ionic liquid gel and patterned liquid metal, characterized in that, Prepared by the preparation method according to any one of claims 1-9; the multifunctional flexible electronic device includes upper and lower base layers and a liquid metal alloy layer formed between the upper and lower base layers; the upper and lower base layers are ionic gel layers.

Images