Liquid metal ink and preparation method and application thereof

Abstract

The invention discloses liquid metal ink as well as a preparation method and application thereof, relates to the technical field of liquid metal ink, and solves the technical problems that the existing conductive ink is poor in dispersion effect and easy to cause nozzle blockage, and high-temperature sintering is needed, so that the processing cost is increased, and a substrate material is limited. The preparation method comprises the following steps: dissolving n-dodecyl p-hydroxybenzoate in an ethanol solution to obtain an organic solution; liquid metal is dropped into the organic solution, and dispersion liquid of the liquid metal is obtained through ultrasonication; the dispersion liquid and diethylene glycol monomethyl ether are mixed and subjected to ultrasonic treatment, and quasi ink is obtained; mixing the quasi ink with ethylene glycol according to a volume ratio of 5: (2-4), and carrying out ultrasonic treatment and filter membrane filtration again to obtain liquid metal ink; the prepared liquid metal ink has good stability and dispersity and is suitable for flexible electronic ink-jet printing, and a flexible circuit with high conductivity can be obtained after normal-temperature mechanical sintering.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid metal ink, and in particular to liquid metal ink and a preparation method and application thereof. Background Art

[0002] Inkjet printing is an additive manufacturing process that enables highly scalable, mask-free, cleanroom-free patterning of unconventional materials. However, when using inkjet printing to build microcircuits, functional inks that are stable and well dispersed are required, otherwise the nozzles may become clogged, resulting in printing interruptions.

[0003] At present, the preparation process of commonly used conductive inks such as silver nanoparticle conductive ink and copper conductive ink is relatively complicated and costly. The particle size of nanoparticles is difficult to accurately control, which easily causes the problem of nozzle clogging. In addition, silver ink needs to be sintered at high temperature after printing to achieve conductivity, which is not friendly to electronic devices with flexible substrates that are not resistant to high temperatures, thus placing great restrictions on substrate materials and increasing processing costs. Summary of the invention

[0004] The present invention aims to solve the technical problems that the existing conductive ink has poor dispersion effect and is easy to cause nozzle clogging, and requires high-temperature sintering to increase processing costs and restrict the base material. The purpose is to provide a liquid metal ink and its preparation method and application. The prepared liquid metal ink has good stability and dispersibility and is suitable for flexible electronic inkjet printing. After mechanical sintering at room temperature, a flexible circuit with high conductivity can be obtained.

[0005] The present invention is achieved through the following technical solutions:

[0006] The first object of the present invention is to provide a method for preparing liquid metal ink, comprising the following steps:

[0007] dissolving n-dodecyl p-hydroxybenzoate in an ethanol solution to obtain an organic solution;

[0008] Dropping liquid metal into the organic solution, and obtaining a dispersion of the liquid metal by ultrasonic crushing;

[0009] The dispersion was mixed with diethylene glycol monomethyl ether and ultrasonicated to obtain a quasi-ink;

[0010] The quasi-ink was mixed with ethylene glycol in a volume ratio of 5:(2-4), ultrasonicated again, and filtered with a filter membrane to obtain liquid metal ink.

[0011] As a further technical solution of the present invention, the content of n-dodecyl parahydroxybenzoate in the organic solution is 0.4-1.2 wt %.

[0012] As a further technical solution of the present invention, the content of n-dodecyl parahydroxybenzoate in the organic solution is 0.8 wt %.

[0013] As a further technical solution of the present invention, the liquid metal is EGaIn.

[0014] As a further technical solution of the present invention, the concentration of the liquid metal is 17-29wt%.

[0015] As a further technical solution of the present invention, the concentration of the liquid metal is 29wt%.

[0016] As a further technical solution of the present invention, the dispersion is mixed with diethylene glycol monomethyl ether in a ratio of 1:1.

[0017] As a further technical solution of the present invention, the volume ratio of the quasi-ink and ethylene glycol is 5:4.

[0018] The second object of the present invention is to provide a liquid metal ink prepared by the above method.

[0019] The third object of the present invention is to provide the use of the aforementioned liquid metal ink in the preparation of flexible circuits.

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

[0021] 1. The present invention breaks the liquid metal into tiny nanoparticles through the strong mechanical action generated by the propagation of ultrasonic waves in the liquid, and the nanoparticles spontaneously form a layer of gallium oxide film. The dispersant n-dodecyl paraben has a strong hydrophilic end, which is tightly combined with the gallium oxide film, while the hydrophobic end of its long carbon chain faces outward, thereby coating the liquid metal nanoparticles, thereby forming uniform and stable nanoparticles, so that the liquid metal ink has good stability and dispersibility.

[0022] 2. The present invention further regulates the ink to obtain a liquid metal ink with moderate viscosity, making it suitable for a flexible electronic inkjet printer. After mechanical sintering at room temperature, a flexible circuit with high conductivity can be obtained, thereby realizing efficient maskless preparation of micro-flexible circuits. The preparation process is simple and does not require high-temperature treatment, thereby reducing manufacturing costs and requirements for production equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0024] Figure 1 This is an electron microscope image of the liquid metal ink prepared in Example 1.

[0025] Figure 2 This is an electron microscope image of the liquid metal ink prepared in Comparative Example 2.

[0026] Figure 3 This is a physical picture of the liquid metal microcircuit printed in Example 7. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the technical solutions in the embodiments of the present invention are clearly and completely described below in combination with the embodiments and drawings. Obviously, the schematic implementation modes of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0028] The following is a detailed description of the embodiments of the liquid metal ink, the preparation method and the application thereof according to the present invention with reference to the accompanying drawings as appropriate. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and facilitate the understanding of those skilled in the art.

[0029] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range.

[0030] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0031] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0032] Unless otherwise specified, the terms "include" and "comprising" mentioned in this application may be open-ended or closed-ended. For example, the terms "include" and "comprising" may mean that other substances not listed may also be included or only the listed substances may be included.

[0033] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0034] To solve the technical problems that the existing conductive ink has poor dispersion effect and is easy to cause nozzle clogging, requires high-temperature sintering, increases processing costs, and limits the substrate material, the technical solution of the present invention is to provide a method for preparing liquid metal ink, comprising the following steps:

[0035] dissolving n-dodecyl paraben in an ethanol solution to obtain an organic solution;

[0036] Dropping liquid metal into the organic solution, and obtaining a dispersion of the liquid metal by ultrasonic crushing;

[0037] The dispersion was mixed with diethylene glycol monomethyl ether and ultrasonicated to obtain a quasi-ink;

[0038] The quasi-ink was mixed with ethylene glycol in a volume ratio of 5:(2-4), and then ultrasonicated again and filtered with a filter membrane to obtain a liquid metal ink with moderate viscosity.

[0039] The invention breaks liquid metal into tiny nanoparticles by strong mechanical action generated by ultrasonic wave propagation in liquid, and the nanoparticles spontaneously form a layer of gallium oxide film. The dispersant n-dodecyl paraben has a strong hydrophilic end, which is tightly combined with the gallium oxide film, while the hydrophobic end of its long carbon chain faces outward, thereby coating the liquid metal nanoparticles, thereby forming uniform and stable nanoparticles. The liquid metal ink can pass through the nozzle of the inkjet printer to print microcircuits. Then, mechanical sintering at room temperature is performed to destroy the liquid metal oxide layer to make the circuit conductive.

[0040] The invention uses n-dodecyl parahydroxybenzoate as a dispersant for liquid metal, adopts an ultrasonic crushing method to crush the liquid metal into nanoparticles, and is coated with a dispersant to achieve stable and uniform dispersion. Meanwhile, by adding the specific dispersant, liquid metal particles with an average particle size of 60 nm can be obtained during the first ultrasonic dispersion. Compared with conventional dispersants, the particle size obtained by the invention is smaller, which is more conducive to the subsequent preparation of small-particle ink, so that the ink can smoothly pass through the nozzle of the inkjet printer; by adding diethylene glycol monomethyl ether, the boiling point of the ink can be increased, and the solvent volatilization during the printing process can be prevented from clogging the nozzle of the inkjet printer and affecting the printing quality; by adding ethylene glycol, the viscosity of the liquid metal ink is adjusted to 8-12 mPa·s, and a liquid metal ink with moderate viscosity is obtained, so that the liquid metal ink is suitable for a flexible electronic inkjet printer. After mechanical sintering at room temperature, a flexible circuit with high conductivity is obtained, thereby realizing efficient maskless preparation of a micro flexible circuit.

[0041] As a further technical solution of the present invention, the content of n-dodecyl p-hydroxybenzoate in the organic solution is 0.4-1.2wt%. For example, the content of n-dodecyl p-hydroxybenzoate in the organic solution can be 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, and more preferably, the content of n-dodecyl p-hydroxybenzoate in the organic solution is 0.8wt%.

[0042] As a further technical solution of the present invention, the liquid metal is EGaIn (Ga 75.5 In 24.5 ), the present invention preferably uses EGaIn eutectic gallium-indium alloy Ga 75.5 In 24.5 , where the mass fractions of Ga and In are 75.5% and 24.5%, respectively.

[0043] As a further technical solution of the present invention, the concentration of the liquid metal is 17-29wt%. For example, the concentration of the liquid metal can be 17wt%, 18wt%, 19wt%, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, or 29wt%; further preferably, the concentration of the liquid metal is 29wt%.

[0044] As a further technical solution of the present invention, the dispersion is mixed with diethylene glycol monomethyl ether in a ratio of 1:1.

[0045] As a further technical solution of the present invention, the volume ratio of the quasi-ink and ethylene glycol is 5:(2-4), for example, it can be 5:2, 5:3, 5:4. Preferably, the volume ratio of the quasi-ink and ethylene glycol is 5:4.

[0046] As a further technical solution of the present invention, the membrane filtration adopts a membrane pore size of 1 μm.

[0047] Based on the aforementioned preparation method, the present invention obtains a liquid metal ink.

[0048] The liquid metal ink prepared by the present invention is mainly used to prepare flexible circuits. The liquid metal itself has a very high electrical conductivity, so that the final manufactured circuit has excellent electrical properties, which is particularly important in high-performance electronic devices. The low Young's modulus and high ductility of the liquid metal make the prepared circuit have good flexibility and can be applied to various flexible electronic devices, such as wearable devices and curved displays.

[0049] The specific application method is: the liquid metal ink prepared by the present invention is printed by a flexible electronic inkjet printer to form a high-resolution pattern on a substrate, and after mechanical sintering at room temperature, a flexible circuit with high conductivity is obtained. The flexible circuit is suitable for various flexible electronic devices.

[0050] Traditional conductive inks, such as silver nanoparticle inks, require high-temperature sintering after printing to achieve conductivity, which not only increases production costs but also limits the choice of flexible substrate materials. The high conductivity of liquid metal inks does not require high-temperature sintering, reducing processing costs and restrictions on substrate materials. Using liquid metal inks can simplify the printing process because it does not require complex preparation processes or high-temperature treatment, simplifying the process flow, reducing manufacturing costs and requirements for production equipment.

[0051] The liquid metal ink of the present invention is suitable for inkjet printing. The inkjet printing process has a maskless characteristic, which allows complex patterns and diversified circuit designs to be quickly produced to meet the needs of diversified electronic products. The high stability and good dispersibility of the liquid metal ink help to achieve high-resolution pattern printing on substrates (such as PET), which expands the application range of microcircuits in the field of flexible electronics.

[0052] The technical solution of the present invention is further described in detail below in conjunction with embodiments.

[0053] It should be noted that the experimental methods used in the examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained by those skilled in the art through commercial channels.

[0054] Example 1

[0055] A method for preparing liquid metal ink comprises the following steps:

[0056] (1) dissolving n-dodecyl p-hydroxybenzoate in an ethanol solution to obtain an organic solution; wherein the content of n-dodecyl p-hydroxybenzoate in the organic solution is 0.8 wt %.

[0057] (2) Dropping liquid metal into the organic solution obtained in the previous step, and obtaining a dispersion of liquid metal by ultrasonic crushing; the average particle size is 60 nm, wherein the concentration of liquid metal in the dispersion is 29 wt %; the ultrasonic power is 60% (total power is 650 W), the ultrasonic time is 120 min, and an ice water bath is used throughout the process to control the temperature of the liquid below 35° C.

[0058] (3) The dispersion obtained in the previous step was mixed with diethylene glycol monomethyl ether in a volume ratio of 1:1 and ultrasonicated, with an ultrasonic power of 60% (total power of 650 W) and an ultrasonic time of 120 min. An ice water bath was used throughout the process to control the temperature of the liquid below 35° C. to obtain a quasi-ink;

[0059] (4) The quasi-ink was mixed with ethylene glycol in a volume ratio of 5:4, and ultrasonicated again under the same ultrasonic conditions as the previous ultrasonication, and then filtered through a 1 μm filter membrane to obtain liquid metal ink.

[0060] The electron microscope image of the liquid metal ink prepared in this embodiment is as follows: Figure 1 As shown, the viscosity of the liquid metal particles is 9.80 mPa·s and the average particle size is 88 nm.

[0061] Example 2

[0062] A method for preparing liquid metal ink comprises the following steps:

[0063] (1) dissolving n-dodecyl p-hydroxybenzoate in an ethanol solution to obtain an organic solution; wherein the content of n-dodecyl p-hydroxybenzoate in the organic solution is 0.4 wt %.

[0064] (2) Dropping liquid metal into the organic solution obtained in the previous step, and obtaining a dispersion of liquid metal by ultrasonic crushing; wherein the concentration of liquid metal in the dispersion is 17 wt %; the ultrasonic power is 60% (total power is 650 W), the ultrasonic time is 120 min, and an ice water bath is used throughout the process to control the temperature of the liquid below 35° C.

[0065] (3) mixing the dispersion obtained in the previous step with diethylene glycol monomethyl ether in a ratio of 1:1 and ultrasonicating to obtain a quasi-ink;

[0066] (4) The quasi-ink was mixed with ethylene glycol in a volume ratio of 5:4, ultrasonicated again, and filtered through a 1 μm filter membrane to obtain liquid metal ink.

[0067] Example 3

[0068] A method for preparing liquid metal ink comprises the following steps:

[0069] (1) dissolving n-dodecyl p-hydroxybenzoate in an ethanol solution to obtain an organic solution; wherein the content of n-dodecyl p-hydroxybenzoate in the organic solution is 1.2 wt %.

[0070] (2) Dropping liquid metal into the organic solution obtained in the previous step, and obtaining a dispersion of liquid metal by ultrasonic crushing; wherein the concentration of liquid metal in the dispersion is 22 wt %; the ultrasonic power is 60% (total power is 650 W), the ultrasonic time is 120 min, and an ice water bath is used throughout the process to control the temperature of the liquid below 35° C.

[0071] (3) mixing the dispersion obtained in the previous step with diethylene glycol monomethyl ether in a ratio of 1:1 and ultrasonicating to obtain a quasi-ink;

[0072] (4) The quasi-ink was mixed with ethylene glycol in a volume ratio of 5:4, ultrasonicated again, and filtered through a 1 μm filter membrane to obtain liquid metal ink.

[0073] Example 4

[0074] A method for preparing liquid metal ink comprises the following steps:

[0075] (1) dissolving n-dodecyl p-hydroxybenzoate in an ethanol solution to obtain an organic solution; wherein the content of n-dodecyl p-hydroxybenzoate in the organic solution is 0.6 wt %.

[0076] (2) Dropping liquid metal into the organic solution obtained in the previous step, and obtaining a dispersion of liquid metal by ultrasonic crushing; wherein the concentration of liquid metal in the dispersion is 20wt%; the ultrasonic power is 60% (total power is 650W), the ultrasonic time is 120min, and an ice water bath is used throughout the process to control the temperature of the liquid below 35°C.

[0077] (3) mixing the dispersion obtained in the previous step with diethylene glycol monomethyl ether in a ratio of 1:1 and ultrasonicating to obtain a quasi-ink;

[0078] (4) The quasi-ink was mixed with ethylene glycol in a volume ratio of 5:2, sonicated again, and filtered through a 1 μm filter membrane to obtain liquid metal ink.

[0079] Example 5

[0080] A method for preparing liquid metal ink comprises the following steps:

[0081] (1) dissolving n-dodecyl p-hydroxybenzoate in an ethanol solution to obtain an organic solution; wherein the content of n-dodecyl p-hydroxybenzoate in the organic solution is 1.0 wt %.

[0082] (2) Dropping liquid metal into the organic solution obtained in the previous step, and obtaining a dispersion of liquid metal by ultrasonic crushing; wherein the concentration of liquid metal in the dispersion is 25wt%; the ultrasonic power is 60% (total power is 650W), the ultrasonic time is 120min, and an ice water bath is used throughout the process to control the temperature of the liquid below 35°C.

[0083] (3) mixing the dispersion obtained in the previous step with diethylene glycol monomethyl ether in a ratio of 1:1 and ultrasonicating to obtain a quasi-ink;

[0084] (4) The quasi-ink was mixed with ethylene glycol in a volume ratio of 5:3, sonicated again, and filtered through a 1 μm filter membrane to obtain liquid metal ink.

[0085] Example 6

[0086] A method for preparing liquid metal ink comprises the following steps:

[0087] (1) dissolving n-dodecyl p-hydroxybenzoate in an ethanol solution to obtain an organic solution; wherein the content of n-dodecyl p-hydroxybenzoate in the organic solution is 1.0 wt %.

[0088] (2) Dropping liquid metal into the organic solution obtained in the previous step, and obtaining a dispersion of liquid metal by ultrasonic crushing; wherein the concentration of liquid metal in the dispersion is 20wt%; the ultrasonic power is 60% (total power is 650W), the ultrasonic time is 120min, and an ice water bath is used throughout the process to control the temperature of the liquid below 35°C.

[0089] (3) mixing the dispersion obtained in the previous step with diethylene glycol monomethyl ether in a ratio of 1:1 and ultrasonicating to obtain a quasi-ink;

[0090] (4) The quasi-ink was mixed with ethylene glycol in a volume ratio of 5:3, sonicated again, and filtered through a 1 μm filter membrane to obtain liquid metal ink.

[0091] Comparative Example 1

[0092] The difference between this comparative example and Example 1 is that no dispersant n-dodecyl paraben is added. Liquid metal is dropped into an ethanol solution without a dispersant and immediately delaminated within a short time after ultrasonic treatment, and subsequent printing cannot be performed.

[0093] Comparative Example 2

[0094] The difference between this comparative example and Example 1 is that no ethylene glycol is added to mix with the quasi-ink. The ink viscosity is 2.72 mPa·s, with good dispersibility, and the average particle size of the liquid metal particles is 49 nm. Figure 2 shown.

[0095] Example 7

[0096] A method for preparing a flexible circuit comprises the following steps:

[0097] The liquid metal ink prepared in Example 1 is printed by a flexible electronic inkjet printer to form a high-resolution pattern on a PET substrate. After mechanical sintering at room temperature, a flexible circuit with high conductivity is obtained.

[0098] The prepared flexible circuit was tested and the results showed that the conductivity was 5.6×10 5 S / m, the minimum line width of printing is 100μm, such as Figure 3 shown.

[0099] Finally, it should be noted that the above specific embodiments are only used to explain in detail the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific implementation method of the present invention and is not used to limit the protection scope of the present invention. Although the present invention is described in detail with reference to the above specific embodiments, ordinary technicians in this field should understand that it is still possible to modify the technical solutions recorded in the above embodiments, or to replace or improve some or all of the technical features therein. These modifications, equivalent replacements and improvements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A method for preparing liquid metal ink, characterized in that: The following steps are involved: dissolving n-dodecyl p-hydroxybenzoate in an ethanol solution to obtain an organic solution; Dropping liquid metal into the organic solution, and obtaining a dispersion of the liquid metal by ultrasonic crushing; The dispersion was mixed with diethylene glycol monomethyl ether and ultrasonicated to obtain a quasi-ink; The quasi-ink was mixed with ethylene glycol in a volume ratio of 5:(2-4), ultrasonicated again, and filtered with a filter membrane to obtain liquid metal ink.

2. The method for preparing liquid metal ink according to claim 1, characterized in that: The content of n-dodecyl parahydroxybenzoate in the organic solution is 0.4-1.2 wt %.

3. The method for preparing liquid metal ink according to claim 2, characterized in that: The content of n-dodecyl parahydroxybenzoate in the organic solution is 0.8 wt %.

4. The method for preparing liquid metal ink according to claim 1, characterized in that: The liquid metal is EGaIn.

5. The method for preparing liquid metal ink according to claim 1, characterized in that: The concentration of the liquid metal is 17-29 wt %.

6. The method for preparing liquid metal ink according to claim 5, characterized in that: The concentration of the liquid metal is 29 wt %.

7. The method for preparing liquid metal ink according to claim 1, characterized in that: The dispersion was mixed with diethylene glycol monomethyl ether in a ratio of 1:

1.

8. The method for preparing liquid metal ink according to claim 1, characterized in that: The volume ratio of the quasi-ink to ethylene glycol is 5:

4.

9. A liquid metal ink prepared by the method according to any one of claims 1 to 8.

10. Use of the liquid metal ink as claimed in claim 9 in preparing flexible circuits.

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