A method of patterning a liquid metal on a flexible substrate

Abstract

The application discloses a method for patterning liquid metal on a flexible substrate, which comprises the following steps: (1) taking a flexible film substrate as a base material and attaching an electrode pattern mask; (2) placing the base material with the attached electrode pattern mask on a low-temperature device, and printing the liquid metal into an electrode pattern on the flexible substrate through repeated rubbing; wherein, during the repeated rubbing, the temperature of the low-temperature device is kept at a temperature lower than the melting point of the liquid metal for a certain time, and then is increased to a temperature higher than the melting point of the liquid metal. The method provided by the application can realize fast, direct, simple, efficient and high-quality patterning of liquid metal on a flexible substrate.

Description

Technical Field

[0001] This invention belongs to the field of liquid metal printing, and specifically relates to a method for patterning liquid metal on a flexible substrate. Background Technology

[0002] Liquid metals possess not only excellent fluidity but also the superior electrical and thermal conductivity of metals, making them widely used in flexible electronics, wearable devices, biomedical therapy, and soft machines. However, the extremely high surface tension of liquid metals makes it difficult to wet most materials, especially flexible polymers, thus hindering the patterning of liquid metals on flexible substrates. To overcome this drawback, researchers have attempted to mix liquid metals with viscous liquids to improve their adhesion to the substrate, thereby achieving stable bonding. For example, Wang et al., in their paper "Printable Liquid-Metal@PDMS Stretchable Heater with High Stretchability and Dynamic Stability for Wearable Thermotherapy" published in Advanced Materials Technologies, reported a conductive composite material prepared using liquid metal and PDMS, which improved patterning capabilities and successfully fabricated a high-performance electrically driven heater using this material. Furthermore, Guo et al., in their paper "One-Step Liquid Metal Transfer Printing: Toward Fabrication of Flexible Electronics on Wide Range of Substrates" published in Advanced Materials Technologies, reported a transfer printing method that attaches liquid metal to PMA adhesive, making it an efficient transfer printing patterning method for bonding liquid metal to various substrates. Encapsulation has also proven to be an effective way to construct liquid metal smart materials such as electronic skin.

[0003] However, these methods rely on the addition of materials other than liquid metal and the substrate, which can complicate the fabrication process and affect electrical, thermal, or mechanical properties. Therefore, how to directly pattern liquid metal on flexible polymer substrates is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a method for patterning liquid metal on a flexible substrate, which can achieve rapid, direct, simple and efficient patterning of liquid metal on a flexible substrate.

[0005] This invention provides the following technical solution:

[0006] A method for patterning liquid metal on a flexible substrate, the method comprising the following steps:

[0007] (1) A flexible thin film substrate is used as the substrate material, and an electrode pattern mask is attached thereon;

[0008] (2) Place the substrate material on which the electrode pattern mask is attached on a low-temperature device, and print the liquid metal on the flexible substrate as an electrode pattern by repeatedly rubbing the substrate material.

[0009] During the repeated friction process, the temperature of the cryogenic equipment is maintained at a temperature below the melting point of liquid metal for a certain period of time, and then raised to a temperature above the melting point of liquid metal.

[0010] The technical concept of this invention lies in the following: During repeated rubbing, the flexible substrate (such as PDMS) is initially maintained at a low temperature (below the melting point of liquid metal) on a low-temperature device (such as a cold stage). At this low temperature, the liquid metal solidifies at the point of contact with the substrate. The partially solidified liquid metal remains firmly on the PDMS, and because the partially solidified liquid metal effectively modifies the PDMS surface, it further facilitates the retention of liquid metal on the PDMS substrate surface during subsequent rubbing. Then, during the subsequent heating (above the melting point of liquid metal), this liquid metal remains on the PDMS substrate surface in a solid form. The method provided by this invention is inexpensive, efficient, practical, simple to operate, and produces excellent printing results.

[0011] Furthermore, in step (1), the substrate material is polydimethylsiloxane (PDMS).

[0012] A further preferred embodiment is that a flexible polydimethylsiloxane (PDMS) thin film substrate is prepared by a four-sided coating apparatus.

[0013] Furthermore, in step (1), the electrode pattern mask is prepared from transparent tape using a laser cutting machine.

[0014] In step (2), the liquid metal is one of gallium-indium alloy, gallium-indium-tin alloy, and liquid gallium.

[0015] Furthermore, in step (2), during repeated friction, the temperature is maintained at a temperature below the melting point of the liquid metal for 15-25 minutes, and then heated to a temperature above the melting point of the liquid metal at a heating rate of 3-7°C.

[0016] Furthermore, in step (2), during repeated friction, the temperature below the melting point of the liquid metal is 20-30°C below the melting point, and the temperature above the melting point of the liquid metal is 3-5°C above the melting point.

[0017] Furthermore, in step (2), the liquid metal is continuously rubbed on the flexible substrate using a friction medium.

[0018] Furthermore, the friction medium is selected from dust-free paper.

[0019] More preferably, the substrate material is polydimethylsiloxane (PDMS), and the liquid metal is gallium indium alloy (EGaIn) with a Ga:In ratio of 75:25. During repeated friction, the temperature of the cryogenic equipment is maintained at -10°C for 20 minutes, and then heated to 20°C at a rate of 5°C per minute.

[0020] In this invention, the cryogenic equipment can be a cold stage.

[0021] Compared with existing technologies, this invention uses a low-temperature combined with friction method to pattern metal. It utilizes the fact that liquid metal partially solidifies at low temperatures, making it easier to retain on a substrate, ultimately achieving patterning on a flexible substrate. This provides a fast, direct, simple, and efficient method for patterning liquid metal on flexible substrates, solving the problem of difficulty in coating liquid metal onto polymer flexible substrates for patterning due to its high surface tension. Furthermore, the patterning process used in this invention is simple and direct, requiring no complex templates or patterning techniques, and the liquid metal patterns obtained on flexible substrates (such as PDMS) exhibit high precision and high retention. Attached Figure Description

[0022] Figure 1 The present invention provides a preparation process for a method (temperature-controlled friction method) for patterning liquid metal on a flexible substrate;

[0023] Figure 2 The image shown is a 5x magnified optical microscope image of a liquid metal electrode pattern prepared by the temperature-controlled friction method in the example.

[0024] Figure 3 An optical microscope image magnified 5x for a comparative example of a liquid metal electrode pattern prepared by room temperature rubbing. Detailed Implementation

[0025] The technical solution of the present invention will be further illustrated below with reference to the embodiments.

[0026] Example

[0027] like Figure 1 As shown, the fabrication process of the method (temperature-controlled friction method) for patterning liquid metal on a flexible substrate provided in this embodiment is as follows: Figure 1 As shown, specifically:

[0028] 1) Mix the SK-184 main agent and curing agent for PDMS preparation in a ratio of 10:1, use a degassing machine to eliminate air bubbles in the solution, and then use a four-sided coating machine to prepare a PDMS film. Heat the prepared PDMS film at 80°C for 3 hours to cure.

[0029] 2) The transparent tape is designed into an adhesive neural electrode pattern mask using a laser cutting machine, and then the substrate is placed on a cold table;

[0030] 3) By setting the cold stage temperature program, the cold stage is set to -10℃ and held for 20 minutes. Then, the temperature is increased to 20℃ at a rate of 5℃ per minute. During this heating process, the liquid metal (75:25 eutectic EGaIn) is continuously rubbed on the PDMS using a lint-free friction medium. The rubbing continues until the heating ends. The neural electrode pattern mask is then removed, and finally, the liquid metal is printed as an electrode pattern on the PDMS.

[0031] Electrode patterns were obtained by repeatedly rubbing liquid metal onto a flexible substrate under a controlled temperature stage. The details of the liquid metal patterns, magnified 5x, were observed using an optical microscope. Figure 2 As shown.

[0032] Comparative Example

[0033] Without using a cold stage to regulate temperature, electrode patterns were obtained by repeatedly rubbing liquid metal on a flexible substrate at room temperature. The details of the liquid metal patterns, magnified 5x, were observed using an optical microscope. Figure 3 As shown.

[0034] contrast Figure 2 and Figure 3 It can be seen that the temperature-controlled friction method used in this invention can quickly, directly, simply and efficiently pattern liquid metal on a flexible substrate, and the prepared liquid metal pattern exhibits high precision and high retention.

[0035] The specific embodiments described above illustrate the technical solution and beneficial effects of the present invention in detail. It should be understood that the above description is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for patterning liquid metal on a flexible substrate, characterized in that, Includes the following steps: The method includes the following steps: (1) A flexible thin film substrate is used as the substrate material, and an electrode pattern mask is attached thereon; (2) Place the substrate material on which the electrode pattern mask is attached on a low-temperature device, and print the liquid metal on the flexible substrate as an electrode pattern by repeatedly rubbing the substrate material. In step (2), during repeated friction, the temperature is maintained at a temperature below the melting point of liquid metal for 15-25 minutes, and then heated to a temperature above the melting point of liquid metal at a heating rate of 3-7°C.

2. The method for patterning liquid metal on a flexible substrate according to claim 1, characterized in that, In step (1), the substrate material is polydimethylsiloxane (PDMS).

3. The method for patterning liquid metal on a flexible substrate according to claim 1, characterized in that, In step (1), the electrode pattern mask is prepared from transparent tape by a laser cutting machine.

4. The method for patterning liquid metal on a flexible substrate according to claim 1, characterized in that, In step (2), the liquid metal is one of gallium-indium alloy, gallium-indium-tin alloy, and liquid gallium.

5. The method for patterning liquid metal on a flexible substrate according to claim 1, characterized in that, In step (2), during repeated friction, the temperature below the melting point of the liquid metal is 20-30°C below the melting point, and the temperature above the melting point of the liquid metal is 3-5°C above the melting point.

6. The method for patterning liquid metal on a flexible substrate according to claim 1, characterized in that, In step (2), liquid metal is continuously rubbed on a flexible substrate using a friction medium.

7. The method for patterning liquid metal on a flexible substrate according to claim 1, characterized in that, The substrate material is polydimethylsiloxane (PDMS), and the liquid metal is gallium indium alloy (EGaIn) with a Ga:In ratio of 75:

25. During repeated friction, the temperature of the cryogenic equipment is maintained at -10°C for 20 minutes, and then increased to 20°C at a rate of 5°C per minute.

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