Liquid metal circuit and its preparation method and application

Abstract

The present invention discloses a liquid metal circuit. The liquid metal circuit is made of gallium-based liquid metal and silicone rubber, and the mass ratio of the gallium-based liquid metal to the silicone rubber is: (0.5-8):(9.5-2). The present invention also provides a preparation method and application of the liquid metal circuit. Compared with the prior art, the liquid metal circuit obtained after printing in the present invention does not require mechanical pressing or scratching, and does not require freezing activation. The liquid metal circuit can be obtained losslessly by directly peeling off the upper layer of solidified printing slurry.

Description

Technical Field

[0001] The present invention belongs to the field of flexible and elastic electronic technology, and in particular relates to a liquid metal circuit and a preparation method and application thereof. Background Art

[0002] With the rise of wearable devices, soft robots, electronic skin and other fields, traditional hard circuits are no longer applicable and are gradually developing towards flexibility / elasticity. It is crucial for flexible / elastic circuits to have good flexible or stretchable conductors. Researchers prepare stretchable conductors by mixing conductive fillers into soft / elastic polymer materials or forming a three-dimensional conductive network in the matrix. This method is simple and stable, but due to the mixing of polymer materials, the stretchability becomes poor, the resistance will rise sharply, and it may even fail to work properly.

[0003] Gallium-based liquid metal has the advantages of self-healing, low modulus, low toxicity and high conductivity, and researchers have confirmed that liquid metal helps to enhance tensile conductivity. At present, although the above problems can be solved by using gallium-based liquid metal as a circuit conductor, the microfluidic injection method is mostly used, which will consume a large amount of gallium-based liquid metal. If squeezed or poorly packaged, it will also cause liquid metal leakage and contaminate the circuit. If the template method or printing method is used, due to the large surface tension of liquid metal and the poor wettability of most soft / elastic substrates, it cannot adhere well to the surface of the substrate. Therefore, the requirements for the substrate are very high and the types are limited. Although plasma surface treatment and polishing can be used to increase the surface roughness of the substrate, some liquid metal will still fall off when it encounters multiple bending or stretching in actual use, causing circuit failure. This is also a challenge that limits the application of liquid metal. Summary of the invention

[0004] The purpose of the present invention is to provide a method of directly changing the wettability with a substrate by compounding silicone rubber with gallium-based liquid metal, and obtaining a lossless liquid metal circuit by a direct peeling method.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a liquid metal circuit, the liquid metal circuit is made of gallium-based liquid metal and silicone rubber, and the mass ratio of the gallium-based liquid metal to the silicone rubber is: (0.5-8):(9.5-2).

[0006] Preferably, the gallium-based liquid metal comprises a gallium main body, and the gallium main body is selected from one of pure gallium, gallium-indium alloy and gallium-indium-tin alloy.

[0007] Preferably, the gallium-based liquid metal also includes a balance component, and the balance component is selected from one or more of iron-based monometallic materials, cobalt-based monometallic materials, nickel-based monometallic materials, copper-based monometallic materials, silver-based monometallic materials, multi-component magnetic metals, multi-component non-magnetic metals and solid non-metallic materials.

[0008] Preferably, the silicone rubber is single-component liquid silicone and / or two-component liquid silicone.

[0009] A second object of the present invention is to provide a method for preparing a liquid metal circuit, the method specifically comprising the following steps:

[0010] S1. Stirring and mixing gallium-based liquid metal and silicone rubber according to a certain proportion, and then extracting air after stirring evenly to obtain a mixture of gallium-based liquid metal and silicone rubber;

[0011] S2, after the mixture of gallium-based liquid metal and silicone rubber obtained in step S1 is allowed to stand or centrifuge, the lower sediment is taken out to obtain a liquid metal-based slurry;

[0012] S3, injecting the liquid metal-based slurry obtained in step S2 into a barrel configured for a 3D direct writing printer, and adjusting the printing parameters of the 3D direct writing printer according to the required circuit model;

[0013] S4, placing the substrate in the printing area of ​​the 3D direct writing printer, clicking to start printing, and then the liquid metal-based slurry is uniformly extruded according to the set circuit model path to obtain a liquid metal circuit blank;

[0014] S5. After solidification treatment, the liquid metal circuit blank is peeled off from the substrate to obtain a liquid metal circuit.

[0015] In the process of preparing the liquid metal circuit of the present invention, after the gallium-based liquid metal is added to the silicone rubber, it is fully stirred. Under the action of shear force, the liquid metal quickly turns into small droplets and is wrapped by the silicone rubber. At the same time, direct writing printing can be set to accumulate multiple layers during the preparation process to facilitate better peeling after curing treatment. There is no need to activate the circuit by mechanical sintering (pressing, scratching) or using liquid metal phase change (freezing). Instead, the liquid metal and silicone mixture after the upper layer of solidification is peeled off to obtain a liquid metal circuit without loss. The circuit can be used in various flexible / elastic electronic fields such as electrodes, capacitors, sensors, antennas, inductors, etc.

[0016] Preferably, in step S1, the stirring parameters are as follows: the stirring environment is room temperature or vacuum, the stirring speed is 300-2000prm / min, and the stirring time is 2-20min.

[0017] Preferably, in step S2, the centrifugal parameters are as follows: centrifugal time is 1-15 min, and centrifugal speed is 500-8000 rpm.

[0018] Preferably, in step S3, the printing parameters include extrusion needle thickness, printing speed, extrusion volume and extrusion air pressure.

[0019] Preferably, the ranges of the printing parameters are as follows: the outer diameter of the needle is 0.31-3.4 mm, the inner diameter of the needle is 2.69-0.15 mm, the printing speed is 10-300 mm / s, the extrusion volume is 50-150%, and the extrusion pressure is 0.1-0.5 MPa.

[0020] Preferably, in step S4, the cumulative number of printed layers is 1-10. Usually, it is set to print a single-layer circuit. In order to facilitate subsequent peeling and obtain a lossless circuit, the cumulative number of printed layers can be set to 1-10.

[0021] Preferably, in step S5, the parameters of the curing treatment are as follows: the curing temperature is 40-100° C., and the curing time is 5-48 hours.

[0022] After the slurry is solidified, the silicone rubber slurry on the substrate is directly peeled off with tweezers or hands. Due to the modulus of the liquid metal itself and gravity, the silicone slurry has a certain sedimentation during the static curing process, and the force generated during the peeling process will directly separate the upper and lower layers of the liquid metal. Part of it remains on the substrate pattern, and part of it is peeled off. Since the silicone and the substrate directly improve the wettability of the liquid metal and the substrate, a complete liquid metal pattern can be obtained after peeling.

[0023] Preferably, the substrate is selected from one of a hard substrate, a flexible substrate and an elastic substrate.

[0024] Preferably, the hard substrate is selected from one of wood, PCB, FR4, polytetrafluoroethylene, and silicon wafer.

[0025] Preferably, the flexible substrate is selected from one of a cloth-based material, a paper-based material, a PI film, a plastic film, a PET film, and PVA.

[0026] Preferably, the elastic substrate is selected from one of PDMS, silicone, Ecoflex, SBS elastomer, POE elastomer, aliphatic aromatic random copolyester, rubber, resin, hydrogel, polyurethane, styrene block copolymer, PVC, polyimide, polyethylene terephthalate plastic, polyethylene octene co-elastomer, and thermoplastic elastomer.

[0027] The third object of the present invention is to provide an application of liquid metal circuit in the field of flexible electronics.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. The prepared gallium-based liquid metal and silicone rubber mixed printing slurry has low cost and greatly improves the wettability of the gallium-based liquid metal and the substrate;

[0030] 2. The liquid metal circuit obtained after printing does not require mechanical pressing or scratching, and does not require freezing activation. The liquid metal circuit can be obtained without loss by directly peeling off the upper layer of solidified printing slurry.

[0031] 3. The raw materials are easily available, the preparation cost is low, it is green and environmentally friendly, the utilization rate is high, and it is easy to promote the large-scale preparation of liquid metal circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a physical picture of the layers of the printing slurry after centrifugation in Example 1 of the present invention;

[0033] Figure 2 This is a physical picture of the spiral circuit that has not been peeled off after printing in Example 1 of the present invention;

[0034] Figure 3 is a state diagram of circuit stripping in Embodiment 1 of the present invention;

[0035] Figure 4 This is a SEM image of the liquid metal circuit obtained after peeling in Example 1 of the present invention;

[0036] Figure 5 This is a diagram of the conductivity verification process of the liquid metal circuit prepared in Example 1 of the present invention under different stretching amounts. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0038] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0039] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0040] An embodiment of the present invention provides a liquid metal circuit, which is made of gallium-based liquid metal and silicone rubber, and the mass ratio of the gallium-based liquid metal to the silicone rubber is: (0.5-8):(9.5-2), wherein the gallium-based liquid metal includes a gallium main body, and the gallium main body is selected from one of pure gallium, gallium-indium alloy, and gallium-indium-tin alloy, and the silicone rubber is a single-component liquid silicone and / or a two-component liquid silicone.

[0041] In other specific embodiments, the gallium-based liquid metal also includes a balance component, and the balance component is selected from one or more of iron-based monometallic metals, cobalt-based monometallic metals, nickel-based monometallic metals, copper-based monometallic metals, silver-based monometallic metals, multi-component magnetic metals, multi-component non-magnetic metals and solid non-metals.

[0042] The present invention also provides a method for preparing a liquid metal circuit, which specifically includes the following steps:

[0043] S1. Stir and mix gallium-based liquid metal and silicone rubber in proportion, at room temperature or in a vacuum environment, control the stirring speed to be 300-2000prm / min, and the stirring time to be 2-20min. After stirring evenly, evacuate the air to obtain a mixture of gallium-based liquid metal and silicone rubber;

[0044] S2, after the mixture of gallium-based liquid metal and silicone rubber obtained in step S1 is allowed to stand or centrifuge, the lower sediment is taken out to obtain liquid metal-based slurry, wherein when centrifugation is adopted, the centrifugation parameters are as follows: the centrifugation time is 1-15min, and the centrifugation speed is 500-8000prm;

[0045] S3, injecting the liquid metal-based slurry obtained in step S2 into the barrel configured by the 3D direct writing printer, and adjusting the printing parameters of the 3D direct writing printer according to the required circuit model, wherein the printing parameters include the thickness of the extrusion needle, the printing speed, the extrusion amount and the extrusion pressure. Specifically, in the embodiment, the range of the printing parameters is as follows: the outer diameter of the needle is 0.31-3.4 mm, the inner diameter of the needle is 2.69-0.15 mm, the printing speed is 10-300 mm / s, the extrusion amount is 50-150%, and the extrusion pressure is 0.1-0.5 MPa;

[0046] S4, placing the substrate in the printing area of ​​the 3D direct writing printer, clicking to start printing, and the liquid metal-based slurry is uniformly extruded according to the set circuit model path to obtain a liquid metal circuit blank, wherein the substrate is selected from one of a hard substrate, a flexible substrate and an elastic substrate, the hard substrate is selected from one of wood, PCB, FR4, polytetrafluoroethylene, and silicon wafer, the flexible substrate is selected from one of a cloth-based material, a paper-based material, a PI film, a plastic film, a PET film, and PVA, and the elastic substrate is selected from one of PDMS, silica gel, Ecoflex, SBS elastomer, POE elastomer, aliphatic aromatic random copolyester, rubber, resin, hydrogel, polyurethane, styrene block copolymer, PVC, polyimide, polyethylene terephthalate plastic, polyethylene octene co-elastomer, and thermoplastic elastomer;

[0047] S5. After the liquid metal circuit blank is cured at 40-100°C for 5-48h, it is peeled off from the substrate to obtain the liquid metal circuit. After the slurry is cured, the silicone rubber slurry on the substrate is directly peeled off with tweezers or hands. Due to the modulus of the liquid metal itself and gravity, the silicone slurry has a certain sedimentation during the static curing process, and the force generated during the peeling process will directly separate the upper and lower layers of the liquid metal. Part of it remains on the substrate pattern, and part of it is peeled off. Since the silicone and the substrate directly improve the wettability of the liquid metal and the substrate, a complete liquid metal pattern can be obtained after peeling.

[0048] In the process of preparing the liquid metal circuit of the present invention, after the gallium-based liquid metal is added to the silicone rubber, it is fully stirred. Under the action of shear force, the liquid metal quickly turns into small droplets and is wrapped by the silicone rubber. At the same time, direct writing printing can be set to accumulate multiple layers during the preparation process to facilitate better peeling after curing treatment. There is no need to activate the circuit by mechanical sintering (pressing, scratching) or using liquid metal phase change (freezing). Instead, the liquid metal and silicone mixture after the upper layer of solidification is peeled off to obtain a liquid metal circuit without loss. The circuit can be used in various flexible / elastic electronic fields such as electrodes, capacitors, sensors, antennas, inductors, etc.

[0049] Preferably, in step S1, preferably, in step S2, preferably, in the specific embodiment, in step S4, the cumulative number of printed layers is 1-10. Usually, it is set to print a single-layer circuit. In order to facilitate subsequent peeling and obtain a lossless circuit, the cumulative number of printed layers can be set to 1-10 layers.

[0050] The third purpose of the embodiment of the present invention is to provide an application of a liquid metal circuit in the field of flexible electronics.

[0051] The technical effects of the present invention are described below in conjunction with specific embodiments.

[0052] Example 1

[0053] The present embodiment provides a liquid metal circuit, which is made of gallium-based liquid metal and silicone rubber, wherein the gallium-based liquid metal is composed of a gallium-indium-tin ternary alloy, and the silicone rubber is a two-component liquid silicone rubber; the preparation method of the liquid metal circuit of the present embodiment includes the following steps:

[0054] S1. Set the mass ratio of liquid metal to silica gel to 3:7, mix and stir the two directly in a vacuum environment, the mechanical stirring speed is 1000prm, and the mixing and stirring time is 5min; after the stirring is completed, a large number of bubbles are generated in the mixed liquid, and the air in the mixed liquid is extracted in a vacuum environment;

[0055] S2, then pour the mixed solution into a centrifuge tube, and centrifuge it in a high-speed centrifuge, preferably with a centrifugal speed of 3000prm and a centrifugal time of 5min; the actual picture of the layers in the centrifuge tube after centrifugation is as shown in the figure Figure 1 As shown, from Figure 1 It can be seen that the upper layer is almost entirely pure silica gel, and the lower layer is a sediment of liquid metal particles wrapped in silica gel, indicating that the utilization of liquid metal is high, up to 99% using the composition of the embodiment of the present invention;

[0056] S3, separating the mixture after centrifugation, taking out the sediment, and then loading it into the barrel of the 3D direct writing printer, setting the required circuit model in advance with the slicing software, and the printing parameters including the thickness of the extrusion needle, the printing speed, the extrusion amount, the extrusion pressure and other parameters; in this embodiment: the needle specification is 27G, the printing speed is 100mm / s, the extrusion amount is 100%, and the extrusion pressure is: 0.25MPa;

[0057] S4. Select a silicone substrate with good elasticity as the substrate and place it in the printing area of ​​the 3D direct writing printer. Click to start printing. The slurry is evenly extruded according to the set circuit model path. Set it to print a double-layer circuit. In order to facilitate subsequent peeling and obtain a lossless circuit, the circuit is obtained after printing. Figure 2 As shown;

[0058] S5. Heat and cure the printed circuit on the silicone substrate in a 50°C blast drying oven for 2 hours. After the slurry is cured, directly peel off the silicone rubber slurry on the substrate with a Figure 3 As shown, the silicone slurry has a certain amount of sedimentation during the static solidification process, and the force generated during the peeling process will directly separate the upper and lower layers of the liquid metal droplets, with part of it remaining on the substrate circuit pattern and part of it in the upper slurry, ultimately obtaining a lossless liquid metal circuit.

[0059] Example 2

[0060] The only difference from Example 1 is that in this embodiment, the mass ratio of the gallium-based liquid metal to the silicone rubber is 1:4, and the gallium-based liquid metal is composed of a gallium-indium alloy and a solid non-metal, and the solid non-metal is composed of carbon nanotubes, and the silicone rubber is a single-component liquid silicone rubber. The rest is the same as Example 1 and will not be repeated here.

[0061] Example 3

[0062] The only difference from Example 1 is that in this embodiment, the mass ratio of the gallium-based liquid metal to the silicone rubber is 8:9.5, and the gallium-based liquid metal is composed of pure gallium and copper-based monometallic metal, and the silicone rubber is a single-component liquid silicone rubber. The rest is the same as Example 1 and will not be repeated here.

[0063] Example 4

[0064] The only difference from Example 1 is that the substrate in this embodiment is wood, and the rest is the same as Example 1 and will not be repeated here.

[0065] Example 5

[0066] The only difference from Example 1 is that the substrate in this embodiment is a plastic film, and the rest is the same as Example 1 and will not be described again.

[0067] Example 6

[0068] The only difference from Example 1 is that in the process of preparing the liquid metal circuit in this embodiment, the stirring environment in step S1 is room temperature, and the rest is the same as Example 1 and will not be repeated here.

[0069] Example 7

[0070] The only difference from Example 1 is that, after the mixture of gallium-based liquid metal and silicone rubber obtained in step S1 in this embodiment is allowed to stand, the lower sediment is taken out to obtain liquid metal-based slurry. The rest is the same as Example 1 and will not be repeated here.

[0071] Example 8

[0072] The only difference from Example 1 is that the printing parameters of step S3 in this embodiment are as follows: the outer diameter of the needle is 3 mm, the inner diameter of the needle is 0.15 mm, the printing speed is 300 mm / s, the extrusion amount is 150%, and the extrusion pressure is 0.5 MPa. The rest is the same as Example 1 and will not be repeated here.

[0073] Example 9

[0074] The only difference from Example 1 is that the cumulative number of printed layers of the liquid metal circuit in this embodiment is 10 layers, and the rest is the same as Example 1 and will not be repeated here.

[0075] In order to verify the conductivity of the circuit and whether it is stable under large tensile deformation, the liquid metal circuit prepared in Example 1 was tested. The specific test process is as follows: 2 LED lamps connected in series are selected to verify the conductivity of the circuit. The test results are as follows: Figure 5 As shown, after testing, when the prepared liquid metal spiral circuit was stretched by 20%, 100%, and 600% respectively, the LED remained lit. The results showed that the prepared liquid metal circuit has good conductivity and stable conductivity when stretched.

[0076] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A liquid metal circuit, characterized in that: The liquid metal circuit is made of gallium-based liquid metal and silicone rubber, and the mass ratio of the gallium-based liquid metal to the silicone rubber is: (0.5-8): (9.5-2). The preparation method of the liquid metal circuit specifically includes the following steps: S1. Stirring and mixing gallium-based liquid metal and silicone rubber according to a certain proportion, and then extracting air after stirring evenly to obtain a mixture of gallium-based liquid metal and silicone rubber; S2, after the mixture of gallium-based liquid metal and silicone rubber obtained in step S1 is allowed to stand or centrifuge, the lower sediment is taken out to obtain a liquid metal-based slurry; S3, injecting the liquid metal-based slurry obtained in step S2 into a barrel configured for a 3D direct writing printer, and adjusting the printing parameters of the 3D direct writing printer according to the required circuit model; S4, placing the substrate in the printing area of ​​the 3D direct writing printer, and after clicking to start printing, the liquid metal-based slurry is uniformly extruded according to the set circuit model path to obtain a liquid metal circuit blank; the substrate is selected from one of a hard substrate, a flexible substrate and an elastic substrate; S5, peeling the liquid metal circuit blank from the substrate after solidification to obtain a liquid metal circuit; In step S5, the parameters of the curing process are as follows: the curing temperature is 40-100° C., and the curing time is 5-48 hours.

2. The liquid metal circuit according to claim 1, characterized in that: The gallium-based liquid metal includes a gallium main body, and the gallium main body is selected from one of pure gallium, gallium-indium alloy, and gallium-indium-tin alloy; And / or, the silicone rubber is a single-component liquid silicone rubber and / or a two-component liquid silicone rubber.

3. The liquid metal circuit according to claim 2, characterized in that: The gallium-based liquid metal also includes a balance component, and the balance component is selected from one or more of iron-based monometallic, cobalt-based monometallic, nickel-based monometallic, copper-based monometallic, silver-based monometallic, multi-component magnetic metals, multi-component non-magnetic metals and solid non-metallic.

4. The liquid metal circuit according to claim 1, characterized in that: In step S1, the stirring parameters are as follows: the stirring environment is room temperature or vacuum, the stirring speed is 300-2000prm / min, and the stirring time is: 2-20min; And / or, in step S2, the centrifugal parameters are as follows: centrifugal time is 1-15 min, centrifugal speed is 500-8000prm; And / or, in step S3, the printing parameters include extrusion needle thickness, printing speed, extrusion volume and extrusion air pressure.

5. The liquid metal circuit according to claim 4, characterized in that: The ranges of the printing parameters are as follows: the outer diameter of the needle is 0.31-3.4 mm, the inner diameter of the needle is 2.69-0.15 mm, the printing speed is 10-300 mm / s, the extrusion volume is 50-150%, and the extrusion air pressure is 0.1-0.5 MPa.

6. The liquid metal circuit according to claim 1, characterized in that: In step S4, the cumulative number of printing layers is 1-10 layers.

7. An application of the liquid metal circuit as described in any one of claims 1 to 6 in the field of flexible electronics.

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