A method for preparing micro-nano structure on liquid metal surface

Abstract

The present application belongs to the field of liquid metal surface processing, and particularly relates to a method for preparing micro-nano structure on the surface of liquid metal. The method comprises the following steps: providing an electrolytic cell, a cathode and an anode; adding liquid metal and electrolyte solution into the electrolytic cell, the cathode contacts the electrolyte solution, and the anode contacts the liquid metal; applying voltage between the cathode and the anode to anodize the liquid metal; wherein the electrolyte solution is substantially insoluble to the anodic oxide film formed in the anodizing process. The method can quickly and low-costly obtain liquid metal oxide semiconductor material with micro-nano structure on the surface of liquid metal, and the morphology of the micro-nano structure can be adjusted by changing the local geometry and curvature of the liquid metal.

Description

Technical Field

[0001] This invention belongs to the field of liquid metal surface processing, and specifically relates to a method for preparing micro-nano structures on the surface of liquid metal. Background Technology

[0002] Room-temperature liquid metals mainly refer to elements or alloys such as gallium, gallium-indium, and gallium-indium-tin that can remain in a liquid state within a room-temperature range. Considering chemical reactivity and toxicity, gallium-based liquid metals, with gallium as the main component, are commonly used. In an atmospheric environment, a self-limiting oxide film spontaneously forms on the surface of gallium-based liquid metals. The oxides of the various components in the liquid metal are semiconductor materials, such as gallium oxide (Ga₂O₃), indium oxide (In₂O₃), and tin oxide (SnO₂). Researchers have already used printing methods to transfer the oxide film from the surface of liquid metals to directly fabricate semiconductor devices (DOI: 10.1002 / pssr.201900271), demonstrating the broad application prospects of liquid metals in the semiconductor field.

[0003] The function of a material surface is determined by both its chemical properties and microstructure. Modifying the microstructure of the oxide film on a liquid metal surface, such as creating micro / nano structures, can endow it with more functions and has promising applications in sensing, flexible electronics, and optics. Micro / nano structures refer to functional structures with micrometer or nanometer-scale features arranged in a specific manner. Currently, micro / nano fabrication technologies include photolithography, femtosecond laser processing, self-assembly processes, plasma etching, and micro / nano additive manufacturing. However, these methods are cumbersome, require sophisticated equipment, and are costly. Therefore, researchers have been researching low-cost and rapid methods for fabricating micro / nano structures on liquid metal surfaces. Currently, a low-cost and efficient method for constructing micro / nano-scale structures on liquid metal surfaces has not yet emerged. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for the rapid and low-cost fabrication of micro- and nano-structures on the surface of liquid metal. This method is simple and requires minimal equipment.

[0005] Specifically, this invention first provides a method for preparing micro / nano structures on the surface of liquid metal, comprising the following steps:

[0006] Provides electrolytic cells, cathodes, and anodes;

[0007] Liquid metal and electrolyte solution are added to an electrolytic cell, with the cathode in contact with the electrolyte solution and the anode in contact with the liquid metal;

[0008] A voltage is applied across the cathode and the anode to perform anodic oxidation on the liquid metal;

[0009] The electrolyte solution is essentially insoluble in the anodic oxide film formed during the anodic oxidation process.

[0010] The present invention discovers that by performing anodizing on liquid metal using the above method and then turning off the power after a period of time, an oxide layer and micro-nano-scale wrinkles (the wavelength range of the wrinkles is 100nm to 50um) are formed on the surface of the liquid metal, thereby obtaining a liquid metal oxide with a micro-nano structure.

[0011] Meanwhile, the present invention requires that the electrolyte solution is basically insoluble in the anodic oxide film formed during the anodic oxidation process, thereby ensuring that the formed anodic oxide film is a barrier type anodic oxide film. If an electrolyte solution such as sodium chloride solution is used, which has high solubility in anodic oxide films, the oxidation process tends to form a porous structure on the surface of the anodic oxide film or cannot form a complete anodic oxide film, and micro-nano-scale wrinkled morphology cannot be obtained.

[0012] Preferably, the surface of the liquid metal in contact with the electrolyte solution is planar, cylindrical, or spherical. Experiments have shown that by changing the local geometry and curvature of the liquid metal, micro- and nanostructures with different morphologies can be obtained.

[0013] Preferably, the liquid metal remains liquid during anodizing. In practice, considering the supercooling of the liquid metal, the temperature during anodizing can be maintained within the range of -40°C to +100°C, which is the melting point of the liquid metal.

[0014] Preferably, a DC power supply of 1V to 100V is used to apply voltage across the cathode and the anode.

[0015] Preferably, the anodizing time is 10s to 60min.

[0016] Preferably, the pH of the electrolyte solution is 3 to 12, and more preferably neutral.

[0017] Preferably, the electrolyte solution comprises an ionized salt and a solvent, wherein the ionized salt is one or a mixture of borates, chromates, molybdates, tartrates, citrates, oxalates, carbomer, sodium polyacrylate, sodium carboxymethyl cellulose, sodium alginate, and polyacrylamide, and the solvent is water.

[0018] More preferably, the electrolyte solution further includes an additive, which is an alcohol, such as ethylene glycol or glycerol.

[0019] Preferably, the concentration of the electrolyte solution is 0.01 wt% to 10 wt%.

[0020] Preferably, the liquid metal has a melting point below 300°C and is a conductive fluid formed from one or more of the following elements: gallium, indium, tin, zinc, bismuth, lead, cadmium, copper, silver, gold, iron, cobalt, nickel, manganese, titanium, and vanadium, or a conductive fluid formed with a fluid dispersant.

[0021] Preferably, the materials of the cathode and the anode are each independently selected from graphite, stainless steel, tungsten, titanium or nickel.

[0022] Preferably, the anodizing is performed without stirring. In this invention, it is necessary to minimize disturbance to the surface of the liquid metal during anodizing.

[0023] The beneficial effects of this invention are as follows:

[0024] 1) The method for rapidly preparing micro-nano structures on the surface of liquid metal at low cost provided by the present invention can rapidly obtain liquid metal oxide semiconductor materials with micro-nano structures on the surface of liquid metal;

[0025] 2) The method for rapidly and cost-effectively preparing micro- and nano-structures on the surface of liquid metal provided by this invention has a simple process, does not require expensive equipment, and is low in cost;

[0026] 3) The method for rapidly and cost-effectively preparing micro- and nano-structures on the surface of liquid metal provided by this invention can adjust the morphology of micro- and nano-structures by changing the local geometry and curvature of the liquid metal. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the prior art in the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 A schematic diagram of an apparatus for preparing surface microstructures by electrochemical oxidation of liquid metals.

[0029] In the diagram: 1. DC power supply; 2. Cathode; 3. Anode; 4. Anode insulation layer; 5. Electrolytic container; 6. Electrolyte solution; 7. Liquid metal.

[0030] Figure 2 This is a SEM image of the one-dimensional wrinkled structure on the sample surface obtained in Example 1.

[0031] Figure 3 This is a SEM image of the two-dimensional wrinkled structure on the sample surface obtained in Example 2. Detailed Implementation

[0032] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention. Any modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and essence of the invention are within the scope of the invention.

[0033] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. All reagents or instruments without specified manufacturers are conventional products that can be purchased through legitimate channels.

[0034] Figure 1 The following is a schematic diagram of the apparatus for preparing surface microstructures by electrochemical oxidation of liquid metal in the embodiments below. In the figure: 1, DC power supply; 2, cathode; 3, anode; 4, anode insulating layer; 5, electrolytic container; 6, electrolyte solution; 7, liquid metal.

[0035] Example 1

[0036] An electrochemical method for the low-cost and rapid preparation of micro / nano structures on liquid metal surfaces includes the following steps:

[0037] Step 1: Take a 1kg container of pure gallium and melt it into liquid metal in a water bath at 50℃. Use a syringe to draw 5ml of liquid metal and draw a thin line of liquid metal on the bottom of a round glass petri dish. Adjust the temperature of the water bath to 35℃ and use the water bath to control the temperature of the petri dish and the liquid metal to keep the liquid metal in a liquid state.

[0038] Step 2: Add 1 wt% sodium carboxymethyl cellulose (CNC-Na) solution to the petri dish, covering the liquid metal. Connect the power supply cable from the DC power source to the electrodes. The cathode (platinum electrode) is placed in the electrolyte solution, and the anode (graphite rod) is connected to the liquid metal. The portion of the anode in contact with the electrolyte solution is insulated with polyimide insulating tape (i.e., the anode insulation layer).

[0039] Step 3: Adjust the DC power supply voltage to 15V and turn on the power to anodize the liquid metal. Turn off the power after 30 seconds. At this point, an oxide layer and microstructure have appeared on the surface of the liquid metal, and the optical appearance of the liquid metal has changed.

[0040] Step 4: Remove the electrolyte solution from the electrolytic container (i.e., the round glass petri dish), wash the liquid metal surface with deionized water and dry it to obtain a liquid metal oxide sample with micro-nano wrinkled structure.

[0041] Because the liquid metal substrate is a long, thin line, the upper surface in contact with the electrolyte solution can be approximated as a cylinder. During the anodizing process, the surface oxide film thickens and compressive stress is generated, with the main stress direction along the axial direction. Therefore, the surface instability morphology is a one-dimensional wrinkled stripe morphology, such as... Figure 2 As shown, the direction of the wrinkled stripes is perpendicular to the axis of the base.

[0042] Example 2

[0043] An electrochemical method for the low-cost and rapid preparation of micro / nano structures on liquid metal surfaces includes the following steps:

[0044] Step 1: Take a 1kg container of pure gallium and melt it into liquid metal in a water bath at 50℃. Use a syringe to draw 20ml of liquid metal and inject it into the bottom of a round glass petri dish, forming a liquid metal pad with a flat top surface. Adjust the water bath to 35℃ and use it to control the temperature of the petri dish and the liquid metal, keeping the liquid metal in a liquid state.

[0045] Step 2: Add 0.5 wt% sodium carboxymethyl cellulose (CNC-Na) solution to the petri dish, covering the liquid metal. Connect the power supply cable from the DC power source to the electrodes. The cathode (stainless steel) is placed in the electrolyte solution, and the anode (graphite rod) is connected to the liquid metal. Insulate the part of the anode in contact with the electrolyte solution with polyimide insulating tape.

[0046] Step 3: Adjust the DC power supply voltage to 10V and turn on the power to anodize the liquid metal. Turn off the power after 1 minute. At this point, an oxide layer and microstructure have appeared on the surface of the liquid metal, and the optical appearance of the liquid metal has changed.

[0047] Step 4: Remove the electrolyte solution from the electrolytic container, wash the liquid metal surface with deionized water and dry it to obtain a liquid metal oxide sample with micro-nano wrinkled structure.

[0048] Since the upper surface of the liquid metal pad is flat, it can be approximated as a plane. During the anodizing process, the surface oxide film thickens and generates compressive stress, which can be considered as equibiaxial compressive stress. Therefore, the surface instability morphology is a two-dimensional labyrinthine folded morphology, such as... Figure 3 As shown.

[0049] Comparative Example 1

[0050] Compared with Example 2, the only difference was that the electrolyte solution was replaced with a 1 wt% phosphate buffer solution (pH=7). The results showed that no typical wrinkle morphology was observed on the oxide film, but pores of hundreds of nanometers could be observed.

[0051] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for fabricating micro / nano structures on the surface of liquid metal, characterized in that, Includes the following steps: Provides electrolytic cells, cathodes, and anodes; Liquid metal and electrolyte solution are added to an electrolytic cell, with the cathode in contact with the electrolyte solution and the anode in contact with the liquid metal; A voltage is applied across the cathode and the anode to perform anodic oxidation on the liquid metal; The electrolyte solution comprises an ionized salt and a solvent, wherein the ionized salt is sodium carboxymethyl cellulose and the solvent is water; The liquid metal is gallium.

2. The method for preparing micro / nano structures on the surface of liquid metal according to claim 1, characterized in that, The surface of the liquid metal in contact with the electrolyte solution is a plane, a cylinder, or a sphere.

3. The method for preparing micro / nano structures on the surface of liquid metal according to claim 1 or 2, characterized in that, The liquid metal remains liquid during anodizing.

4. The method for preparing micro / nano structures on the surface of liquid metal according to claim 1 or 2, characterized in that, A DC power supply of 1V to 100V is used to apply voltage across the cathode and the anode.

5. The method for preparing micro / nano structures on the surface of liquid metal according to claim 3, characterized in that, A DC power supply of 1V to 100V is used to apply voltage across the cathode and the anode.

6. The method for preparing micro / nano structures on the surface of liquid metal according to claim 1, 2, or 5, characterized in that, The anodizing time is 10s to 60min.

7. The method for preparing micro / nano structures on the surface of liquid metal according to claim 3, characterized in that, The anodizing time is 10s to 60min.

8. The method for preparing micro / nano structures on the surface of liquid metal according to claim 4, characterized in that, The anodizing time is 10s to 60min.

9. The method for preparing micro / nano structures on the surface of liquid metal according to claim 1, 2, 5, 7 or 8, characterized in that, The concentration of the electrolyte solution is 0.01wt% to 10wt%.

10. The method for preparing micro / nano structures on the surface of liquid metal according to claim 3, characterized in that, The concentration of the electrolyte solution is 0.01wt% to 10wt%.

11. The method for preparing micro / nano structures on the surface of liquid metal according to claim 4, characterized in that, The concentration of the electrolyte solution is 0.01wt% to 10wt%.

12. The method for preparing micro / nano structures on the surface of liquid metal according to claim 6, characterized in that, The concentration of the electrolyte solution is 0.01wt% to 10wt%.

13. The method for preparing micro / nano structures on the surface of a liquid metal according to any one of claims 1, 2, 5, 7, 8, 10-12, characterized in that, The cathode and the anode are each independently selected from metals, carbon-based materials, and ceramic materials.

14. The method for preparing micro / nano structures on the surface of liquid metal according to claim 3, characterized in that, The cathode and the anode are each independently selected from metals, carbon-based materials, and ceramic materials.

15. The method for preparing micro / nano structures on the surface of liquid metal according to claim 4, characterized in that, The cathode and the anode are each independently selected from metals, carbon-based materials, and ceramic materials.

16. The method for preparing micro / nano structures on the surface of liquid metal according to claim 6, characterized in that, The cathode and the anode are each independently selected from metals, carbon-based materials, and ceramic materials.

17. The method for preparing micro / nano structures on the surface of liquid metal according to claim 9, characterized in that, The cathode and the anode are each independently selected from metals, carbon-based materials, and ceramic materials.

18. The method for preparing micro / nano structures on the surface of a liquid metal according to any one of claims 1, 2, 5, 7, 8, 10-12, 14-17, characterized in that, The cathode and the anode are each independently selected from graphite, stainless steel, tungsten, titanium, platinum, silver, copper, or nickel.

19. The method for preparing micro / nano structures on the surface of liquid metal according to claim 3, characterized in that, The cathode and the anode are each independently selected from graphite, stainless steel, tungsten, titanium, platinum, silver, copper, or nickel.

20. The method for preparing micro / nano structures on the surface of liquid metal according to claim 4, characterized in that, The cathode and the anode are each independently selected from graphite, stainless steel, tungsten, titanium, platinum, silver, copper, or nickel.

21. The method for preparing micro / nano structures on the surface of liquid metal according to claim 6, characterized in that, The cathode and the anode are each independently selected from graphite, stainless steel, tungsten, titanium, platinum, silver, copper, or nickel.

22. The method for preparing micro / nano structures on the surface of liquid metal according to claim 9, characterized in that, The cathode and the anode are each independently selected from graphite, stainless steel, tungsten, titanium, platinum, silver, copper, or nickel.

23. The method for preparing micro / nano structures on the surface of liquid metal according to claim 13, characterized in that, The cathode and the anode are each independently selected from graphite, stainless steel, tungsten, titanium, platinum, silver, copper, or nickel.

24. The method for preparing micro / nano structures on a liquid metal surface according to any one of claims 1, 2, 5, 7, 8, 10-12, 14-17, 19-23, characterized in that, The anodizing is performed without stirring.

25. The method for preparing micro / nano structures on the surface of liquid metal according to claim 3, characterized in that, The anodizing is performed without stirring.

26. The method for preparing micro / nano structures on the surface of liquid metal according to claim 4, characterized in that, The anodizing is performed without stirring.

27. The method for preparing micro / nano structures on the surface of liquid metal according to claim 6, characterized in that, The anodizing is performed without stirring.

28. The method for preparing micro / nano structures on the surface of liquid metal according to claim 9, characterized in that, The anodizing is performed without stirring.

29. The method for preparing micro / nano structures on the surface of liquid metal according to claim 13, characterized in that, The anodizing is performed without stirring.

30. The method for preparing micro / nano structures on the surface of liquid metal according to claim 18, characterized in that, The anodizing is performed without stirring.

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