阅读说明：本技术 一种液态金属-高分子可打印墨水及其制备和打印方法 (Liquid metal-polymer printable ink and preparation and printing methods thereof ) 是由 贺永 周璐瑜 傅建中 于 2019-10-07 设计创作，主要内容包括：本发明公开了一种液态金属高分子可打印墨水,由液态金属与可固化的高分子体系混合而成,其中液态金属的重量百分比含量为75-95％。本发明同时公开了上述液态金属高分子可打印墨水的制备方法及其应用。本发明的液态金属高分子可打印墨水具有良好的导电性,是一种理想的可用于柔性电子设备的导电墨水。同时,它具有出色的打印性能,为液态金属基柔性电子设备的高速度、高精度打印创造了可能。本发明的液态金属高分子可打印墨水的高分子组分可根据实际实施时柔性电子设备的柔性基底材料进行灵活的变换,从而保证墨水和柔性基底强的粘接力,提高了柔性电子设备的可靠性。本发明的液态金属高分子可打印墨水成分简单,制备方便,可打印性好,成本低,具有广阔的应用前景。(The invention discloses liquid metal high polymer printable ink, which is formed by mixing liquid metal and a curable high polymer system, wherein the weight percentage content of the liquid metal is 75-95%. The invention also discloses a preparation method and application of the liquid metal polymer printable ink. The liquid metal polymer printable ink has good conductivity, and is an ideal conductive ink for flexible electronic equipment. Meanwhile, the printing device has excellent printing performance, and creates possibility for high-speed and high-precision printing of liquid metal-based flexible electronic equipment. The high polymer components of the liquid metal high polymer printable ink can be flexibly changed according to the flexible substrate material of the flexible electronic equipment in actual implementation, so that the strong adhesive force of the ink and the flexible substrate is ensured, and the reliability of the flexible electronic equipment is improved. The liquid metal polymer printable ink disclosed by the invention is simple in component, convenient to prepare, good in printability, low in cost and wide in application prospect.)

1. The liquid metal polymer printable ink is characterized by being formed by mixing liquid metal and a curable polymer system, wherein the weight percentage content of the liquid metal is 75-95%.

2. The liquid metal polymer printable ink according to claim 1, wherein the liquid metal is gallium and binary, ternary, or quaternary alloys thereof, wherein the weight percentage of gallium in the liquid metal is 20-100%.

3. A liquid metal polymer printable ink according to claim 1 or 2, wherein the binary alloy comprises gallium indium, gallium tin, gallium mercury, gallium sodium, gallium potassium, gallium cesium; the ternary alloy comprises gallium indium tin, gallium indium mercury, gallium indium sodium, gallium indium potassium, gallium indium cesium, gallium tin mercury, gallium tin sodium, gallium tin potassium, gallium tin cesium, gallium mercury sodium, gallium mercury potassium, gallium mercury cesium and gallium sodium potassium; the quaternary alloy comprises gallium indium tin zinc, gallium indium tin mercury, gallium indium tin sodium, gallium indium tin potassium, gallium indium tin cesium, gallium indium mercury sodium, gallium indium mercury potassium, gallium indium mercury cesium, gallium tin mercury sodium, gallium tin mercury potassium, gallium tin mercury cesium, gallium indium sodium potassium, gallium tin sodium potassium, gallium mercury sodium potassium and gallium cesium sodium potassium.

4. A liquid metal polymer printable ink according to claim 1 or 2, wherein the polymer system mainly comprises one or more of an uncured or partially cured one-component silicone rubber system, an uncured or partially cured multi-component silicone rubber system, an uncured or partially cured PDMS system, an uncured or partially cured flexible resin system.

5. The liquid metal polymer printable ink according to claim 4, wherein the polymer system further comprises a corresponding curing agent.

6. The method for preparing the liquid metal polymer printable ink as claimed in any one of claims 1 to 5, wherein the method comprises the following steps: and uniformly mixing the liquid metal with excessive polymer system liquid, removing the excessive polymer system liquid from the mixed material, and obtaining a concentrated solution, namely the liquid metal polymer printable ink.

7. The method of claim 6, wherein the liquid metal droplets have a diameter of less than 50 μm after mixing.

8. The method of claim 6, wherein the liquid metal is present in an amount of 20-70% by weight of the printable ink.

9. A method for printing by using liquid metal polymer printable ink, wherein the liquid metal polymer printable ink is the liquid metal polymer printable ink according to any one of claims 1 to 5.

10. The method of claim 9, wherein after printing, any one of the following methods is used to make the printed pattern conductive:

the method 1, standing the printed material until the pattern is conductive, and then finishing final curing;

the method 2, curing the printed material, and applying external force to the cured pattern until the pattern is conductive;

and 3, solidifying the printed material, and freezing the solidified pattern until the pattern is conductive.

Technical Field

The invention relates to the field of liquid metal printing, in particular to a liquid metal preparation and printing method applied to flexible electronics.

Background

With the rapid development of the electronic information industry, flexible electronic devices having excellent environmental suitability receive more and more extensive attention. One of the technical keys to flexible electronics fabrication is the selection of conductive materials, and liquid metals, such as gallium-based alloys, are increasingly being used in the flexible electronics field due to their high conductivity, liquid flexibility and self-healing properties.

There are three main methods for manufacturing flexible electronic devices using liquid metal as a conductive material: micro-channel injection, stencil printing, and direct writing. The micro flow channel injection method requires multi-step operations to complete the manufacture of the flexible electronic device, and the operation is complicated and difficult for mass production. The stencil printing method requires a corresponding stencil to be manufactured in advance before the circuit is manufactured, which causes a waste of the stencil and a low production efficiency when the circuit is frequently changed and customized. The direct writing method can directly print the liquid metal into designed patterns according to actual needs without complex steps or templates, and is an ideal manufacturing method of the flexible electronic equipment. However, due to the large surface tension of liquid metal and the poor wettability to the flexible substrate, it is often difficult to directly write pure liquid metal, which greatly limits the popularization and application of liquid metal in the field of flexible electronics.

Disclosure of Invention

In view of the technical bottleneck that the existing liquid metal is difficult to directly print and lacks of proper high-performance printing ink, the invention provides the liquid metal-polymer printable ink.

The liquid metal polymer printable ink is formed by mixing liquid metal and a curable polymer system, wherein the weight percentage content of the liquid metal is 75-95%.

Preferably, the liquid metal-polymer printable ink is a binary alloy, a ternary alloy or a quaternary alloy of gallium and gallium. The binary alloy comprises gallium indium, gallium tin, gallium mercury, gallium sodium, gallium potassium, gallium cesium and the like, the ternary alloy comprises gallium indium tin, gallium indium mercury, gallium indium sodium, gallium indium potassium, gallium indium cesium, gallium tin mercury, gallium tin sodium, gallium tin potassium, gallium tin cesium, gallium mercury sodium, gallium mercury potassium, gallium mercury cesium, gallium sodium potassium and the like, and the quaternary alloy comprises gallium indium tin zinc, gallium indium tin mercury, gallium indium tin sodium, gallium indium tin potassium, gallium indium tin cesium, gallium indium mercury sodium, gallium tin mercury potassium, gallium tin mercury cesium, gallium tin mercury potassium, gallium tin mercury cesium, gallium indium sodium potassium, gallium tin sodium potassium, gallium mercury sodium potassium, gallium cesium potassium and the like.

Preferably, the weight percentage of gallium in the liquid metal is 20-100%. More preferably, the alloy is a gallium-indium binary alloy, wherein the content of gallium is 35 to 90 parts by weight, and the balance is indium; or gallium indium tin ternary alloy, wherein the gallium content is 35-80 parts by weight, the indium content is 10-20 parts by weight, and the balance is tin.

Preferably, the liquid metal-polymer printable ink includes a polymer, such as single-component silicone rubber, multi-component silicone rubber, PDMS, flexible resin, and the like. The polymer system liquid consists of the components or the components and the corresponding curing agent. The high polymer material selected by the invention can generate strong adhesive force with a common silicon rubber flexible substrate, thereby improving the reliability of the flexible electronic equipment.

In the present invention, the polymer system may be a system in which no curing occurs or a system in which a part of the curing occurs. The curing agent can be a polymer system which can be cured by itself without the curing agent (in this case, the polymer system generally directly adopts a polymer material liquid), or a polymer system which needs the curing agent to be cured (in this case, the polymer system generally comprises a polymer and a corresponding curing agent). The polymer system can be prepared by itself, or can be a commercial product, such as a self-made pre-cured polymer material liquid, or a mixture of a polymer material liquid and a curing agent, which can adopt the existing polymer and curing agent. Preferably, the polymer system mainly comprises one or more of an uncured or partially cured one-component silicone rubber system, an uncured or partially cured multi-component silicone rubber system, an uncured or partially cured PDMS system, and an uncured or partially cured flexible resin system.

The single-component silicon rubber does not need a corresponding curing agent generally and can be cured by itself, and common single-component silicon rubbers comprise Dow Corning 737, Yoghu-966 and Xinyue KE-347-W. The multi-component silicon rubber comprises red-leaf silica gel E600, Hongfeng silica gel HF7709, Ecoflex 00-30 and the like, and matched curing agents are matched according to requirements. The flexible resin comprises plastic photosensitive resin H-03, TIME80SFlexibleresin, flexible resin (ETERSET 2858T, ETERSET 2731T and the like) produced by Changxing company, and matched curing agents are matched according to needs. The polymer materials can be purchased through the existing shopping channels, and various types of products of the types can be selected. For PDMS, a common curing agent may be selected from ethyl orthosilicate. Alternatively, the product of PDMSA or B liquid may be used.

Preferably, for a polymer system requiring matching of a curing agent, the polymer system further comprises a corresponding curing agent.

The preparation method of the liquid metal polymer printable ink in any technical scheme comprises the following steps: and uniformly mixing the liquid metal with excessive polymer system liquid, removing the excessive polymer system liquid from the mixed material, and obtaining a concentrated solution, namely the liquid metal polymer printable ink.

Preferably, the method for preparing the liquid metal polymer printable ink according to any one of the above technical solutions includes the following steps:

1) preparing liquid metal by a conventional method;

2) weighing liquid metal and high polymer according to the proportion, and stirring and mixing the liquid metal and the high polymer to obtain a uniform solution;

3) concentrating the uniform solution obtained in the step 2) to obtain the liquid metal polymer printable ink.

The liquid metal may be prepared by known methods. The polymer system can be a mixture of polymer feed liquid and curing agent feed liquid, or can be independently added polymer feed liquid and curing agent feed liquid.

Preferably, the liquid metal droplets have a diameter of less than 50 microns after mixing. The observation and detection can be performed using a microscope. Stirring and mixing can be adopted, and the stirring and mixing method comprises one or more of mechanical stirring, electromagnetic stirring, ultrasonic stirring and vibration stirring.

The removal of the redundant polymer system liquid can be realized in various ways, preferably, the adopted concentration method is centrifugal concentration, after centrifugation, the mixed liquid consisting of the polymer system liquid and the liquid metal is positioned at the bottom, the upper part is the polymer system liquid with lighter density, and the upper layer liquid is removed to obtain the liquid metal polymer printable ink. Preferably, the stirring time in step 2) is 0.5 to 5 h. The stirring speed is 200-1000 rpm. Preferably, the concentration time in step 3) is 5 to 30 minutes. The rotation speed of concentration is 1000-3000 rpm.

In order to realize mixing conveniently, the weight percentage content of the liquid metal is 20-70% during mixing, and the balance is macromolecule. Namely, the liquid metal-polymer printable ink comprises the following components in parts by weight before concentration: 20-70 parts of liquid metal and the balance of high polymer. When the weight percentage content of the liquid metal is higher, the system viscosity is too high, so that the mixing is difficult to carry out, and the uniform mixing is difficult to ensure.

The method for printing by using the liquid metal polymer printable ink is characterized in that the liquid metal polymer printable ink is any one of the liquid metal polymer printable ink or the liquid metal polymer printable ink prepared by the preparation method of any one of the liquid metal polymer printable ink. When printing, the liquid metal polymer printable ink is added into an ink storage unit of a printer, and printing is carried out on a substrate according to a conventional method.

Preferably, the substrate is a flexible substrate made of silicone rubber. The high polymer material selected by the invention can generate strong adhesive force with a common silicon rubber flexible substrate, thereby improving the reliability of the flexible electronic equipment.

The ink may be left to conduct during printing or activated by pressure or freezing to conduct after printing is complete. Specifically, after printing is completed, the printed pattern is preferably made conductive by any one of the following methods:

the method 1, standing the printed material until the pattern is conductive, and then finishing final curing;

the method 2, curing the printed material, and applying external force to the cured pattern until the pattern is conductive;

and 3, solidifying the printed material, and freezing the solidified pattern until the pattern is conductive.

Compared with the prior art, the liquid metal polymer printable ink has the following advantages:

1) the liquid metal polymer printable ink provided by the invention is only composed of liquid metal and polymers, does not need a complex material formula, and is simple to prepare and low in cost; due to the addition of the polymer, the surface tension of the ink is reduced, the printability of the liquid metal is improved, and the wettability of the liquid metal relative to a flexible substrate is increased; meanwhile, a curable polymer system is adopted, and after curing, the polymer plays a supporting role, so that final electrification activation becomes possible, and the activation method is simple and convenient;

2) according to the liquid metal polymer printable ink, excessive polymer system liquid is adopted in the mixing stage, so that mixing becomes possible, and the uniformity and the controllability of the particle size of liquid metal can be easily ensured; through the concentration step, the printable performance of the ink is greatly improved, so that high-speed and high-precision printing of the liquid metal becomes possible;

3) the liquid metal polymer printable ink provided by the invention has the advantages that the liquid metal provides the conductive capability, so that the ink has excellent conductivity;

4) according to the liquid metal polymer printable ink, the polymer can generate strong adhesion with a flexible polymer substrate in flexible electronics, so that the reliability of flexible electronic equipment is improved;

5) the liquid metal polymer printable ink provided by the invention has no complicated high-temperature sintering process after printing, has no solvent volatilization, and is more efficient and environment-friendly.

In a word, the macromolecular liquid metal printable ink disclosed by the invention is simple to prepare, good in conductivity, excellent in printing performance, free of high-temperature sintering and solvent volatilization, and more efficient and environment-friendly. Meanwhile, the liquid metal polymer printable ink has good conductivity, and is an ideal conductive ink for flexible electronic equipment. Meanwhile, the printing device has excellent printing performance, and creates possibility for high-speed and high-precision printing of liquid metal-based flexible electronic equipment. The high polymer components of the liquid metal high polymer printable ink can be flexibly changed according to the flexible substrate material of the flexible electronic equipment in actual implementation, so that the strong adhesive force of the ink and the flexible substrate is ensured, and the reliability of the flexible electronic equipment is improved. The liquid metal polymer printable ink disclosed by the invention is simple in component, convenient to prepare, good in printability, low in cost and wide in application prospect.

Drawings

FIG. 1 is a schematic diagram illustrating a method for preparing a printable liquid metal polymer ink according to the present invention.

Fig. 2 is a scanning electron microscope image of the liquid metal polymer printable ink obtained in the embodiment of the present invention after printing.

Fig. 3 and 4 are graphs showing the results of conducting the conductivity test in examples 2 and 3, respectively.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the present invention will be further described with reference to the accompanying drawings and specific embodiments. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.