A method for manufacturing a high aspect ratio liquid metal pattern

Abstract

The application discloses a kind of high high-width ratio liquid metal pattern manufacturing method, belong to liquid metal technical field.First, in situ direct writing nanofiber using electrospinning process on rotating receiving substrate, linear micro-ridge structure is made;Then, with micro-ridge structure as mold, the polymer film with micro-groove is casted;Then, pre-stretch the polymer film with micro-groove;Subsequently, liquid metal is coated on the surface of polymer film, liquid metal is scraped by cover glass, so that liquid metal and micro-groove are fully contacted;Subsequently, release the polymer film to initial state;Finally, high high-width ratio liquid metal pattern is prepared by packaging.The manufacturing method of the application does not need external instrument to provide the large pressure difference of liquid metal into micro-channel, does not need complex process steps and expensive processing instrument, is not limited by liquid metal surface oxide film and surface tension, and can be used for high high-width ratio liquid metal pattern processing on flexible substrate.

Description

Technical Field

[0001] This invention relates to the field of liquid metal technology, and more specifically to a method for fabricating liquid metal patterns with a high aspect ratio. Background Technology

[0002] Liquid metals have attracted much attention in fields such as flexible displays and flexible sensing due to their good fluidity, strong conductivity and low toxicity. In particular, patterned liquid metals are widely used in soft robots, flexible wearable electronics, human-computer interaction devices and biomedical devices.

[0003] Traditional liquid metal patterning methods, such as injection molding and vacuum-assisted adsorption, require large pressure differences to break the oxide film on the liquid metal surface, enabling the injection and flow of liquid metal within microgrooves. However, when the cross-sectional size of the microgrooves decreases to the micrometer level, the pressure difference increases dramatically, posing significant challenges to the selection of processing instruments and microgrooving materials. Screen printing requires overcoming the high surface tension of the liquid metal to allow it to flow through a perforated plate with sub-millimeter gaps, thus limiting the maximum liquid metal pattern resolution to 200 μm. Selective surface wetting and laser ablation can process liquid metal patterns with resolutions ranging from tens to several micrometers, but these processes require complex steps and expensive equipment, resulting in low efficiency and long processing times, significantly increasing the cost of high-resolution liquid metal patterns. Cryogenic casting can produce liquid metal structures with linewidths of several hundred micrometers and aspect ratios greater than 1, currently the method with the highest aspect ratio for liquid metal fabrication; however, its resolution is still limited to the hundred-micrometer level, making it impossible to achieve high-resolution, high-aspect-ratio liquid metal pattern fabrication. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a method for fabricating high aspect ratio liquid metal patterns. This method does not require external instruments to provide a large pressure difference for injecting liquid metal into microchannels, does not require complex process steps or expensive processing equipment, is not limited by the oxide film and surface tension of the liquid metal surface, and can perform high aspect ratio and high resolution liquid metal pattern processing on flexible substrates.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for creating a liquid metal graphic with a high aspect ratio, the method comprising the following steps:

[0007] (1) Preparation of flexible substrate with microridges: linear microridge structure is fabricated by in-situ direct writing of nanofibers on a rotating receiving substrate using electrospinning process.

[0008] (2) Fabrication of a flexible polymer film with microgrooves on a flexible substrate: Using a microridge structure as a mold, a polymer film with microgrooves is cast and fabricated.

[0009] (3) Embedding liquid metal inside the microgrooves: First, pre-stretch the polymer film with microgrooves, then coat the surface of the polymer film with liquid metal, and use a cover glass to scrape the liquid metal to make the liquid metal fully contact the microgrooves; then, release the polymer film to the initial state; finally, prepare a high aspect ratio liquid metal pattern by encapsulation.

[0010] In step (1) above, the process of preparing a flexible substrate with microridges is as follows: the flexible substrate is wrapped on a roller as a rotating receiving substrate, and the spinning material is written directly onto the receiving substrate in situ using an electrospinning device to form a smooth linear microridge structure.

[0011] In step (1) above, the flexible substrate material is polyethylene terephthalate (PET), polyimide (PI), aluminum foil, tin foil, or oil film paper; the spinning material is polyvinyl alcohol (PVA) or polymethyl methacrylate (PMMA); the linear microridge structure is an arrayed one-dimensional microridge structure or a two-dimensional microridge structure, and the aspect ratio of the microridge structure is controllable.

[0012] In step (1) above, during the preparation of the flexible substrate with microridges, the distance between the needle tip and the rotating receiving substrate is adjustable, the rotation speed is adjustable, the spinning voltage is adjustable, the spinning time is adjustable, and the spinning material is adjustable. The width and height of the microridges can be controlled according to different usage requirements.

[0013] In step (2) above, the process of making a polymer film with microgrooves is as follows: using a smooth linear microridge structure as a mold, the polymer precursor is poured onto the microridge structure, and after curing, the mold is flipped to obtain a polymer film with microgrooves.

[0014] In step (2) above, the polymer is polydimethylsiloxane (PDMS) or Ecoflex; the aspect ratio of the microgroove is controllable.

[0015] In step (3) above, when the polymer film is pre-stretched, the pre-stretching range is controllable and can be adjusted according to the groove depth and the polymer elastic modulus.

[0016] In step (3) above, the liquid metal is a gallium-based liquid metal, such as gallium indium alloy (EGaIn) or gallium indium tin alloy (Galinstan); the liquid metal can be replaced with different materials as needed, and the aspect ratio of the liquid metal can be controlled and patterned according to different usage requirements.

[0017] The liquid metal pattern produced by the method of this invention has an aspect ratio greater than 5 and a resolution greater than 20μm.

[0018] The advantages and beneficial effects of this invention are as follows:

[0019] (1) This invention utilizes electrospinning to fabricate micro-ridge structures. The aspect ratio of the micro-ridges can be controlled in real time by the spinning time. At the same time, the high-speed rotation of the rotating substrate can bring high linear velocity and large centrifugal force, which is beneficial to the evaporation of solvent from the spinning fibers and the formation of the micro-ridge structure.

[0020] (2) The manufacturing method of the present invention does not require expensive instruments and complex process steps, the processing materials are easy to obtain, and the manufacturing cost is low;

[0021] (3) The present invention can realize the production of high aspect ratio liquid metal graphics with high resolution. Attached image description:

[0022] Figure 1 A schematic diagram illustrating the fabrication of microridge structures on a flexible substrate.

[0023] Figure 2 A schematic diagram for fabricating a polymer film with microgrooves.

[0024] Figure 3 This is a schematic diagram of a pre-stretched polymer film with microgrooves.

[0025] Figure 4 This is a schematic diagram of coating liquid metal onto a flexible polymer surface.

[0026] Figure 5 This is a schematic diagram illustrating the release of the polymer film back to its initial state.

[0027] Figure 6 This is a schematic diagram of the high aspect ratio liquid metal structure after encapsulation.

[0028] Figure 7 Scanning electron microscope (SEM) image of a cross-section of a microgroove embedded with liquid metal.

[0029] In the figure: 1-flexible substrate, 2-spinning material; 3-flexible polymer; 4-liquid metal. Detailed implementation method:

[0030] The embodiments of the present invention will be described in detail below with reference to the technical solutions and accompanying drawings.

[0031] This invention relates to a method for fabricating high aspect ratio liquid metal graphics, the structure of which and the fabrication process are as follows: Figure 1-6 As shown. First, a flexible substrate 1 is wrapped around a roller as a rotating receiving substrate. Then, an electrospinning system is used to orderly deposit spun material 2 onto the rotating receiving substrate, forming a smooth microridge structure, as shown. Figure 1As shown; next, the polymer precursor is cast onto the microridge structure, and after curing, it is molded to obtain a polymer film 3 with microgrooves, as shown. Figure 2 As shown; then the grooved polymer film is pre-stretched, as shown. Figure 3 As shown; then, liquid metal 4 is coated onto the surface of polymer film 3, and the liquid metal is evenly coated by scraping, as shown. Figure 4 As shown; then the polymer film 3 is released back to its initial state, and the liquid metal is embedded inside the microgrooves, as shown. Figure 5 As shown; finally, the micro-trench is encapsulated to obtain a high aspect ratio liquid metal pattern, as shown. Figure 6 As shown.

[0032] Example 1:

[0033] A flexible substrate (tin foil) 1 was wrapped around a roller as a rotating receiving substrate. Under the conditions of 30°C and 35% relative humidity, an electrospinning system was used to orderly deposit spinning material (polyvinyl alcohol) 2 onto the rotating receiving substrate. The vertical distance between the spinning needle tip and the roller was 3 mm. The liquid feed rate of the spinning material 2 was 0.4 mL / h, the potential difference was 2 kV, the roller speed was 500 rpm, and the in-situ spinning was completed in 60 s to prepare a smooth microridge structure.

[0034] Polydimethylsiloxane was used as the flexible polymer film 3. The polymer precursor was prepared by mixing the polydimethylsiloxane main agent and the curing agent, and then cast onto the microridge structure and cured by heating at 80°C for 2 hours. The flexible polymer film 3 with microgrooves was prepared by casting.

[0035] The polymer 3 with microgrooves was pre-stretched to 175% of its original length.

[0036] A gallium-indium-tin alloy (GaInTT) was used as the liquid metal 4, with a mass ratio of gallium, indium, and tin of 62:25:13. The liquid metal 4 was coated onto the surface of the polymer film 3.

[0037] The polymer film 3, coated with liquid metal 4, is released back to its initial state. Scanning electron microscopy (SEM) of the microgroove cross-section embedded with liquid metal is shown below. Figure 7 As shown, the liquid metal has an aspect ratio of 5.9 and a resolution of 16.8 μm.

[0038] The polydimethylsiloxane polymer precursor is cast onto the surface of a flexible polymer film 3 embedded with liquid metal 4 in a trench, and then cured and encapsulated at 80°C for 2 hours to complete the production of a high aspect ratio liquid metal pattern.

[0039] The examples described above are merely illustrative of the embodiments of the present invention, but should not be construed as limiting the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention.

Claims

1. A method for fabricating a liquid metal graphic with a high aspect ratio, characterized in that: The method includes the following steps: (1) Preparation of flexible substrate with microridges: linear microridge structure is fabricated by in-situ direct writing of nanofibers on a rotating receiving substrate using electrospinning process; (2) Fabrication of a flexible polymer film with microgrooves on a flexible substrate: Using a microridge structure as a mold, a polymer film with microgrooves is cast and fabricated. (3) Embedding liquid metal inside the microgroove: First, pre-stretch the polymer film with microgroove, then coat the surface of the polymer film with liquid metal, and use a cover glass to scrape the liquid metal to make the liquid metal fully contact the microgroove; then, release the polymer film to the initial state; finally, prepare a liquid metal pattern with a high aspect ratio by encapsulation.

2. The method for fabricating a high aspect ratio liquid metal pattern according to claim 1, characterized in that: In step (1), the process of preparing a flexible substrate with microridges is as follows: the flexible substrate is wrapped on a roller as a rotating receiving substrate, and the spinning material is written directly onto the receiving substrate in situ using an electrospinning device to form a smooth linear microridge structure.

3. The method for fabricating a high aspect ratio liquid metal pattern according to claim 1, characterized in that: In step (1), the flexible substrate material is polyethylene terephthalate (PET), polyimide (PI), aluminum foil, tin foil or oil film paper; the spinning material is polyvinyl alcohol (PVA) or polymethyl methacrylate (PMMA); the linear microridge structure is an arrayed one-dimensional microridge structure or a two-dimensional microridge structure, and the aspect ratio of the microridge structure is controllable.

4. The method for fabricating a high aspect ratio liquid metal pattern according to claim 1, characterized in that: In step (1), during the preparation of the flexible substrate with microridges, the distance between the needle tip and the rotating receiving substrate is adjustable, the rotation speed is adjustable, the spinning voltage is adjustable, the spinning time is adjustable, and the spinning material is adjustable. The width and height of the microridges can be controlled according to different usage requirements.

5. The method for fabricating a high aspect ratio liquid metal pattern according to claim 1, characterized in that: In step (2), the process of making a polymer film with microgrooves is as follows: using a smooth linear microridge structure as a mold, the polymer precursor is poured onto the microridge structure, and after curing, the mold is flipped to obtain a polymer film with microgrooves.

6. The method for fabricating a high aspect ratio liquid metal pattern according to claim 5, characterized in that: In step (2), the polymer is polydimethylsiloxane (PDMS) or Ecoflex; the aspect ratio of the microgroove is controllable.

7. The method for fabricating a high aspect ratio liquid metal pattern according to claim 1, characterized in that: In step (3), when the polymer film is pre-stretched, the pre-stretching range is controllable and adjusted according to the groove depth and the polymer elastic modulus.

8. The method for fabricating a high aspect ratio liquid metal pattern according to claim 1, characterized in that: In step (3), the liquid metal is a gallium-based liquid metal.

9. The method for fabricating a high aspect ratio liquid metal pattern according to claim 1, characterized in that: In step (3), the liquid metal is replaced with different materials as needed, and the aspect ratio of the liquid metal is controlled and graphically represented according to different usage requirements.

10. The method for fabricating a high aspect ratio liquid metal pattern according to claim 1, characterized in that: The liquid metal images produced by this method have an aspect ratio greater than 5 and a resolution greater than 20 μm.

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