A preparation device and method for nano copper probe for TERS

Abstract

The invention discloses a preparation device and method for a nano copper probe for TERS, comprising an experimental table, a constant temperature heating platform is arranged on the top of the experimental table, a first container filled with a mixed solution of sodium sulfate and phosphoric acid and a second container filled with a phosphoric acid solution are arranged on the constant temperature heating platform, a first displacement table and a second displacement table are connected to the experimental table, the first displacement table is connected to a copper wire through a copper wire fixing device, the second displacement table is connected to an inert nickel-chromium alloy ring through a ring fixing device, and a direct current power supply is also included, the negative electrode of the direct current power supply is connected to the ring fixing device through a first cable, and the positive electrode of the direct current power supply is connected to a stainless steel anode electrode arranged in the first container through a second cable. When in use, a phosphoric acid liquid film or a sodium sulfate and phosphoric acid mixed liquid film is arranged on the inert nickel-chromium alloy ring, and the lower end of the copper wire passes through the liquid film on the inert nickel-chromium alloy ring and is placed in the sodium sulfate and phosphoric acid mixed solution.

Description

Technical Field

[0001] The present invention relates to the technical field of nano metal probes, and in particular to a device and method for preparing a nano copper probe for TERS based on a double electrolyte electrochemical corrosion method. Background Art

[0002] Tip-enhanced Raman spectroscopy (TERS) technology combines plasmon-enhanced Raman spectroscopy and scanning probe microscopy (SPM) technology. Through SPM, a tip with a nanoscale tip (gold, silver, aluminum, copper, etc.) is controlled to approach the substrate surface. Under the irradiation of lasers with appropriate wavelengths and polarizations, due to the localized surface plasmon resonance (LSPR) effect and the lightning rod effect, the photoelectric field between the tip and the substrate is greatly enhanced and highly localized, so that the molecular signals in this area are amplified. Therefore, TERS can provide accurate surface morphology and chemical fingerprint information at the same time. Due to the highly localized near-field photoelectric field generated at the end of the nanoscale tip, the spatial resolution of TERS has reached the nanometer or even sub-nanometer level. It is precisely because of these outstanding advantages that TERS detection is sufficient to obtain chemical information at the nanoscale, helping people to further understand complex reaction processes and special material properties. At present, TERS is increasingly used in catalysis, materials, biology, molecular electronics, and surface science.

[0003] The needle tip is the core of TERS technology. On the one hand, the quality of the needle tip directly determines the quality and resolution of SPM imaging; on the other hand, the needle tip is the only source of Raman enhancement in TERS technology, and its material, radius of curvature, cone angle and surface morphology will significantly affect the sensitivity of TERS. Copper can be used for TERS because of its low price and very little optical loss in the visible and near-infrared regions. However, the only method for preparing copper needle tips is the electrochemical deposition of copper nanoparticles. This method has a complicated preparation process, and the controllability, repeatability and success rate are relatively low. Therefore, achieving a high success rate in preparing copper nanotips is a difficulty that TERS technology urgently needs to solve. Summary of the invention

[0004] The purpose of the present invention is to provide a device and method for preparing a nano copper probe for TERS to overcome the defects of the prior art. The present invention greatly improves the success rate of copper needle preparation and does not require a complex automatic power-off circuit.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme:

[0006] A preparation device for a nano copper probe for TERS comprises a laboratory table, a constant temperature heating platform is arranged on the top of the laboratory table, a first container filled with a mixed solution of sodium sulfate and phosphoric acid and a second container filled with a phosphoric acid solution are arranged on the constant temperature heating platform, a first displacement platform and a second displacement platform are connected to the laboratory table, the first displacement platform is connected to a copper wire through a copper wire fixing device, and the second displacement platform is connected to an inert nickel-chromium alloy ring through a ring fixing device, and also comprises a direct current power supply, the negative electrode of the direct current power supply is connected to the ring fixing device through a first cable, and the positive electrode of the direct current power supply is connected to a stainless steel anode electrode arranged in the first container through a second cable. When in use, a phosphoric acid liquid film or a sodium sulfate and phosphoric acid mixed liquid film is arranged on the inert nickel-chromium alloy ring, and the lower end of the copper wire passes through the liquid film on the inert nickel-chromium alloy ring and is placed in the sodium sulfate and phosphoric acid mixed solution.

[0007] Furthermore, the experimental table adopts a manual lifting platform.

[0008] Furthermore, the first translation platform includes a first electric longitudinal translation platform connected to the experimental platform, and a first electric lateral translation platform connected to the first electric longitudinal translation platform; the second translation platform includes a second electric longitudinal translation platform connected to the experimental platform, and a second electric lateral translation platform connected to the second electric longitudinal translation platform.

[0009] Furthermore, the first translation stage and the second translation stage are both connected to an electric translation controller.

[0010] Furthermore, the phosphoric acid solution is prepared by mixing concentrated phosphoric acid and deionized water in a volume ratio of 1:2.

[0011] Furthermore, the sodium sulfate and phosphoric acid mixed solution is prepared by a phosphoric acid solution and a saturated sodium sulfate solution in a volume ratio of 1:4.

[0012] Furthermore, the temperature of the constant temperature heating platform is 60°C.

[0013] Furthermore, the diameter of the copper wire is 0.3 mm, and the length of the copper wire below the liquid film on the inert nickel-chromium alloy ring is 3 mm.

[0014] Furthermore, the inner diameter of the inert nickel-chromium alloy ring is 10 mm.

[0015] A method for preparing a nano copper probe for TERS comprises the following steps:

[0016] Step 1: prepare phosphoric acid solution and sodium sulfate and phosphoric acid mixed solution respectively, and place them on a constant temperature heating platform for use;

[0017] Step 2: Use dilute hydrochloric acid or dilute sulfuric acid to remove the oxide layer on the surface of the copper wire, and store it in anhydrous ethanol, take the copper wire stored in anhydrous ethanol, and fix the upper end of the copper wire on the copper wire fixing device; fix the inert nickel-chromium alloy ring on the ring fixing device;

[0018] Step 3: Using a second translation stage, the inert nickel-chromium alloy ring forms a phosphoric acid liquid film from the phosphoric acid solution;

[0019] Step 4: Using the second translation stage, the inert nickel-chromium alloy ring containing the phosphoric acid liquid film is adjusted to above the mixed solution of sodium sulfate and phosphoric acid; then, the first translation stage is controlled to pass the copper wire through the phosphoric acid liquid film and immerse it in the mixed solution of sodium sulfate and phosphoric acid;

[0020] Step 5: A DC voltage of 5V is applied to the corrosion circuit through a DC power supply, and the copper wire is electrochemically corroded at the phosphoric acid liquid film, wherein the corrosion circuit is composed of the positive electrode of the DC power supply, the first cable, the stainless steel anode electrode, the mixed solution of sodium sulfate and phosphoric acid, the copper wire, the phosphoric acid liquid film, the inert nickel-chromium alloy ring, the ring fixing device and the negative electrode of the DC power supply;

[0021] Step 6: If the phosphoric acid film breaks during the corrosion process; when the current of electrochemical corrosion is greater than or equal to 0.6 mA, first move the copper wire out of the inert nickel-chromium alloy ring through the first displacement stage, then use the second displacement stage to make the inert nickel-chromium alloy ring form a phosphoric acid film from the phosphoric acid solution, and finally use the second and first displacement stages to pass the copper wire through the phosphoric acid film and immerse it in a mixed solution of sodium sulfate and phosphoric acid to continue electrochemical corrosion;

[0022] When the current of electrochemical corrosion is less than 0.6 mA, the inert nickel-chromium alloy ring is used to extract the liquid film from the mixed solution of sodium sulfate and phosphoric acid below through the second displacement stage. The copper wire is still in the inert nickel-chromium alloy ring and immersed in the mixed solution of sodium sulfate and phosphoric acid. Finally, the copper wire below the liquid film falls off by itself, and the upper copper wire is the prepared copper needle.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] The invention comprises two sets of displacement platforms and a constant temperature heating platform capable of constant temperature heating of a corrosion solution, and electrochemical corrosion occurs to the copper wire at a phosphoric acid liquid film formed in an inert nickel-chromium alloy ring; wherein the corrosion solution (phosphoric acid solution, sodium sulfate and phosphoric acid mixed solution) is constant temperature heated, thereby improving the stability of the phosphoric acid liquid film or the sodium sulfate and phosphoric acid mixed liquid film; in addition, the electric displacement platform is used to solve the problem of accurate positioning of copper wire corrosion after the liquid film is broken; in addition, the invention adopts a double electrolyte electrochemical corrosion method to prepare the copper needle, and when the copper wire is corroded to be very thin, a liquid film is extracted from the sodium sulfate and phosphoric acid mixed solution below, thereby greatly improving the success rate of copper needle preparation, and no complicated automatic power-off circuit is required.

[0025] The nano copper needle prepared by the method of the invention has a curvature radius of 10 to 50 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0027] Figure 1 It is a schematic diagram of the device of the present invention;

[0028] Figure 2 This is a SEM image of the nano copper needles prepared in the embodiment of the present invention at ×140;

[0029] Figure 3 This is a SEM image of the nano copper needles prepared in an embodiment of the present invention at ×2k;

[0030] Figure 4 This is a SEM image of the nano-copper needles prepared in an embodiment of the present invention at ×100k.

[0031] Among them, 1-electric displacement controller, 2-first electric longitudinal displacement platform, 3-second electric longitudinal displacement platform, 4-first electric lateral displacement platform, 5-second electric lateral displacement platform, 6-copper wire fixing device, 7-ring fixing device, 8-copper wire, 9-inert nickel-chromium alloy ring, 10-stainless steel anode electrode, 11-sodium sulfate and phosphoric acid mixed solution, 12-phosphoric acid liquid film, 13-DC power supply, 14-first cable, 15-second cable, 16-phosphoric acid solution, 17-constant temperature heating platform, 18-experimental table. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0033] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0034] See also Figure 1 A preparation device for a nano copper probe for TERS includes an electric displacement controller 1, a first electric longitudinal displacement stage 2, a second electric longitudinal displacement stage 3, a first electric lateral displacement stage 4, a second electric lateral displacement stage 5, a copper wire fixing device 6, a ring fixing device 7, a copper wire 8, an inert nickel-chromium alloy ring 9, a stainless steel anode electrode 10, a sodium sulfate and phosphoric acid mixed solution 11, a phosphoric acid liquid film 12, a DC power supply 13, a first cable 14, a second cable 15, a phosphoric acid solution 16, a constant temperature heating platform 17, and a laboratory table 18.

[0035] The positive electrode of the DC power supply 13 is connected to the stainless steel anode electrode 10 through the first cable 15, the lower end of the stainless steel anode electrode 10 is placed in the sodium sulfate and phosphoric acid mixed solution 11, and the negative electrode of the DC power supply 13 is connected to the cathode ring fixture 7 through the second cable 14. The copper wire 8 is fixed on the copper wire fixture 6, passes through the phosphoric acid liquid film 12, and is immersed in the sodium sulfate and phosphoric acid mixed solution 11. The positive electrode of the DC power supply 13, the first cable 15, the stainless steel 10, the sodium sulfate and phosphoric acid mixed solution 11, the copper wire 8, the phosphoric acid liquid film 12, the inert nickel-chromium alloy ring 9, the ring fixture 7, the second cable 14 and the negative electrode of the DC power supply 13 form a corrosion circuit loop.

[0036] The length of the copper wire under the liquid film is precisely controlled by the electric displacement controller 1, the first electric longitudinal displacement stage 2, the first electric lateral displacement stage 4, the second electric longitudinal displacement stage 3, and the second electric lateral displacement stage 5. When the loop current is greater than or equal to 0.6 mA, the liquid film is broken, and the copper wire 8 is first moved out of the inert nickel-chromium alloy ring 9 by the first electric longitudinal displacement stage 2 and the first electric lateral displacement stage 4, and then the inert nickel-chromium alloy ring 9 is formed into a phosphoric acid liquid film 12 from the phosphoric acid solution 16 by the second electric longitudinal displacement stage 3 and the second electric lateral displacement stage 5. Finally, the copper wire 8 is passed through the phosphoric acid liquid film 12 and immersed in the sodium sulfate and phosphoric acid solution 16 by the first electric longitudinal displacement stage 2 and the first electric lateral displacement stage 4 and the second electric longitudinal displacement stage 3 and the second electric lateral displacement stage 5. In the mixed solution 11, the electric displacement controller 1 can accurately control the new liquid film to remain at the position where the copper wire 8 is corroded, and the electrochemical corrosion continues; when the loop current is less than 0.6 mA, the liquid film breaks, and the inert nickel-chromium alloy ring 9 is used to extract the liquid film from the sodium sulfate and phosphoric acid mixed solution 11 below through the second electric longitudinal displacement stage 3 and the second electric lateral displacement stage 5, wherein the copper wire is still in the ring and immersed in the sodium sulfate and phosphoric acid mixed solution 11. After the copper wire corrosion at the liquid film is completed, the lower end of the copper wire falls off, the corrosion loop is automatically disconnected, and the nano copper needle is formed. The needle tip obtained by electrochemical corrosion is placed in a vacuum chamber for storage after being cleaned and dried with deionized water and isopropyl alcohol.

[0037] A method for preparing a nano copper probe for TERS comprises the following steps:

[0038] Step 1, prepare a sodium sulfate solution, a phosphoric acid solution 16 and a sodium sulfate and phosphoric acid mixed solution 11 respectively, and place them on a constant temperature heating platform 17 for standby use;

[0039] The sodium sulfate solution is a saturated sodium sulfate solution, the phosphoric acid solution 16 is a solution prepared in a volume ratio of concentrated phosphoric acid: deionized water = 1:2, and the sodium sulfate and phosphoric acid mixed solution 11 is a solution prepared in a volume ratio of phosphoric acid solution 16: saturated sodium sulfate solution = 1:4; the temperature of the constant temperature heating platform 7 is 60°C.

[0040] Step 2: Install the copper wire and the ring;

[0041] First, cut the copper wire, then use dilute hydrochloric acid or dilute sulfuric acid to remove the oxide layer on the surface of the copper wire, and store it in anhydrous ethanol; take a copper wire, and fix the upper end of the copper wire 8 on the copper wire fixing device 6; wherein the diameter of the copper wire is 0.3mm.

[0042] An inert nickel-chromium alloy ring 9 is fixed on the ring fixing device 7; wherein the inert nickel-chromium alloy ring 9 has a diameter of 10 mm.

[0043] Step 3, forming a phosphoric acid liquid film 12;

[0044] By controlling the second electric longitudinal translation stage 3 and the second electric lateral translation stage 5, the inert nickel-chromium alloy ring 9 forms a phosphoric acid liquid film 12 from the phosphoric acid solution 16;

[0045] Step 4, connecting the circuit;

[0046] By controlling the second electric longitudinal translation stage 3 and the second electric lateral translation stage 5, the inert nickel-chromium alloy ring 9 containing the liquid film is adjusted to above the mixed solution 11 of sodium sulfate and phosphoric acid; then, the first electric longitudinal translation stage 2 and the first electric lateral translation stage 4 are controlled to pass the copper wire 8 through the phosphoric acid liquid film 12 and immerse it in the mixed solution 11 of sodium sulfate and phosphoric acid, and the length of the copper wire under the phosphoric acid liquid film 12 is controlled to be 3 mm.

[0047] Step 5, turning on the power supply, and electrochemically corroding the copper wire;

[0048] A DC voltage of 5V is applied to the corrosion circuit, and the copper wire is electrochemically corroded at the phosphoric acid liquid film 12 .

[0049] Step 6: Recovery after liquid film rupture and preparation of copper needles

[0050] In order to realize the preparation of copper nanoneedles, the key lies in how the liquid film is formed. If the copper wire corrodes to a very fine diameter less than 100nm, the liquid film will rupture. If the liquid film is still obtained from the external phosphoric acid solution 16, when the copper wire passes through the new liquid film, the lower end of the copper wire is very likely to float on the liquid film, resulting in preparation failure. In order to prevent this from happening, the following solution is adopted for liquid film recovery.

[0051] If the phosphoric acid liquid film 12 breaks during the corrosion process; when the current of electrochemical corrosion is greater than or equal to 0.6 mA, the copper wire 8 is first moved out of the inert nickel-chromium alloy ring 9 by the first electric longitudinal displacement stage 2 and the first electric lateral displacement stage 4, and then the inert nickel-chromium alloy ring 9 is formed into a phosphoric acid liquid film 12 from the phosphoric acid solution 16 by the second electric longitudinal displacement stage 3 and the second electric lateral displacement stage 5, and finally the copper wire 8 is passed through the phosphoric acid liquid film 12 and immersed in the mixed solution 11 of sodium sulfate and phosphoric acid by the second electric longitudinal displacement stage 3 and the second electric lateral displacement stage 5 as well as the first electric longitudinal displacement stage 2 and the first electric lateral displacement stage 4, and the electric displacement controller 1 can accurately control the new liquid film to remain at the position where the copper wire 8 is corroded, and the electrochemical corrosion continues.

[0052] When the current of electrochemical corrosion is less than 0.6 mA, the inert nickel-chromium alloy ring 9 needs to extract the liquid film from the sodium sulfate and phosphoric acid mixed solution 11 below through the second electric longitudinal displacement stage 3 and the second electric lateral displacement stage 5, wherein the copper wire is still in the ring and immersed in the sodium sulfate and phosphoric acid mixed solution 11, ensuring that the lower end of the copper wire will not float on the liquid film when the liquid film is replaced, resulting in preparation failure. Finally, the copper wire below the liquid film falls off by itself, and the copper wire above is the prepared copper needle.

[0053] The prepared copper needle is sequentially cleaned of impurities with deionized water, dried with isopropyl alcohol, and then stored in a vacuum chamber.

[0054] Example

[0055] A copper needle with a curvature radius of 25 nm was produced using a copper wire 8 with a diameter of 0.3 mm.

[0056] The steps for preparing TERS nano-copper needles based on the dual electrolyte electrochemical corrosion method are as follows:

[0057] Step 1, prepare phosphoric acid solution 16 phosphoric acid: water = 1:2 and sodium sulfate and phosphoric acid mixed solution 11, wherein saturated sodium sulfate solution: phosphoric acid solution = 4:1, and place the solution on a 60° C. constant temperature heating platform 17 for standby use;

[0058] Step 2: fix the inert nickel-chromium alloy ring 9 on the ring fixing device 7, and use the second electric longitudinal displacement stage 3 and the second electric lateral displacement stage 5 to make the inert nickel-chromium alloy ring 9 form a phosphoric acid liquid film 12 from the phosphoric acid solution 16, and then use the second electric longitudinal displacement stage 3 and the second electric lateral displacement stage 5 to make the liquid film be above the sodium sulfate and phosphoric acid mixed solution 11;

[0059] Step three, fix the cleaned copper wire on the copper wire fixing device 6, and control the copper wire 8 to pass through the phosphoric acid liquid film 12 through the first electric longitudinal displacement stage 2 and the first electric lateral displacement stage 4, and immerse it in the sodium sulfate and phosphoric acid mixed solution 11. The length of the copper wire under the liquid film is 3mm.

[0060] Step 4: connect the inert nickel-chromium alloy ring 9 to the negative pole of the DC power supply, connect the stainless steel anode electrode 10 to the positive pole of the DC power supply, turn on the DC power supply, and apply a DC voltage of 5V. If the liquid film breaks when the loop current is greater than or equal to 0.6mA, the liquid film should be regenerated from the phosphoric acid solution 16 through the first electric longitudinal displacement stage 2 and the first electric lateral displacement stage 4, the second electric longitudinal displacement stage 3 and the second electric lateral displacement stage 5. When the loop current is less than 0.6mA, the liquid film breaks, and the liquid film is regenerated from the sodium sulfate and phosphoric acid mixed solution 11 below through the second electric longitudinal displacement stage 3 and the second electric lateral displacement stage 5. There is no need to move the first electric longitudinal displacement stage 2 and the first electric lateral displacement stage 4. When the lower end of the copper wire falls, the corrosion circuit is automatically disconnected to obtain the nano copper needle;

[0061] Step 5: The prepared copper needle is cleaned and dried with deionized water and isopropyl alcohol in turn, and then placed in a vacuum chamber.

[0062] The SEM image of the nano copper needles prepared in the embodiment is shown in Figure 2-Figure 4 . Figure 2 This is a SEM image of a copper needle at ×140. Figure 3 The SEM image of the copper needle at ×2K. Figure 4 This is the SEM image of the copper needle at ×100K, from which it can be seen that the curvature radius of the needle tip is 25nm.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit its protection scope. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that after reading the present invention, those skilled in the art can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the invention, but these changes, modifications or equivalent substitutions are all within the protection scope of the pending claims of the invention.

Claims

1. A method for preparing a nano copper probe for TERS, based on a preparation device for a nano copper probe for TERS, the preparation device for a nano copper probe for TERS comprising a laboratory table (18), a constant temperature heating platform (17) is arranged on the top of the laboratory table (18), a first container containing a mixed solution of sodium sulfate and phosphoric acid (11) and a second container containing a phosphoric acid solution (16) are arranged on the constant temperature heating platform (17), a first displacement table and a second displacement table are connected to the laboratory table (18), the first displacement table is connected to a copper wire (8) through a copper wire fixing device (6), and the second displacement table is connected to a copper wire fixing device (6) through a circular The ring fixing device (7) is connected to the inert nickel-chromium alloy ring (9), and also includes a direct current power supply (13), the negative electrode of the direct current power supply (13) is connected to the ring fixing device (7) through a first cable (14), and the positive electrode of the direct current power supply (13) is connected to a stainless steel anode electrode (10) arranged in a first container through a second cable (15). When in use, a phosphoric acid liquid film (12) or a sodium sulfate and phosphoric acid mixed liquid film is arranged on the inert nickel-chromium alloy ring (9), and the lower end of the copper wire (8) passes through the liquid film on the inert nickel-chromium alloy ring (9) and is placed in the sodium sulfate and phosphoric acid mixed solution (11), characterized in that: The following steps are involved: Step 1: prepare a phosphoric acid solution (16) and a mixed solution of sodium sulfate and phosphoric acid (11) respectively, and place them on a constant temperature heating platform (17) for standby use; Step 2: using dilute hydrochloric acid or dilute sulfuric acid to remove the oxide layer on the surface of the copper wire (8), and storing it in anhydrous ethanol, taking the copper wire (8) stored in anhydrous ethanol, and fixing the upper end of the copper wire (8) on the copper wire fixing device (6); fixing the inert nickel-chromium alloy ring (9) on the ring fixing device (7); Step 3: Using a second displacement stage, the inert nickel-chromium alloy ring (9) forms a phosphoric acid liquid film (12) from the phosphoric acid solution (16); Step 4: Using the second displacement stage, the inert nickel-chromium alloy ring (9) containing the phosphoric acid liquid film (12) is adjusted to above the sodium sulfate and phosphoric acid mixed solution (11); then, the first displacement stage is controlled to pass the copper wire (8) through the phosphoric acid liquid film (12) and immerse it in the sodium sulfate and phosphoric acid mixed solution (11); Step 5: A DC voltage of 5V is applied to the corrosion circuit through a DC power supply (13), and the copper wire (8) is electrochemically corroded at the phosphoric acid liquid film (12), wherein the corrosion circuit is composed of the positive electrode of the DC power supply (13), the first cable (14), the stainless steel anode electrode (10), the sodium sulfate and phosphoric acid mixed solution (11), the copper wire (8), the phosphoric acid liquid film (12), the inert nickel-chromium alloy ring (9), the ring fixing device (7) and the negative electrode of the DC power supply (13); Step 6: If the phosphoric acid liquid film (12) breaks during the corrosion process; when the current of the electrochemical corrosion is greater than or equal to 0.6 mA, firstly, the copper wire (8) is moved out of the inert nickel-chromium alloy ring (9) by the first displacement stage, and then the inert nickel-chromium alloy ring (9) is made to form a phosphoric acid liquid film (12) from the phosphoric acid solution (16) by the second displacement stage, and finally, the copper wire (8) is passed through the phosphoric acid liquid film (12) and immersed in a mixed solution of sodium sulfate and phosphoric acid (11) by the second displacement stage and the first displacement stage to continue the electrochemical corrosion; When the current of electrochemical corrosion is less than 0.6 mA, the inert nickel-chromium alloy ring (9) is used to extract a liquid film from the sodium sulfate and phosphoric acid mixed solution (11) below through the second displacement stage, and the copper wire (8) is still in the inert nickel-chromium alloy ring (9) and immersed in the sodium sulfate and phosphoric acid mixed solution (11). Finally, the copper wire below the liquid film falls off by itself, and the copper wire above is the prepared copper needle.

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