A direct pulling method for fabricating single / dual-channel microelectrodes with ultrathin insulating layers

Abstract

This invention belongs to the field of electrochemical technology, specifically disclosing a direct drawing method for preparing single / dual-channel disc microelectrodes with ultrathin insulating layers. The method includes the following steps: designing single / dual-channel silicate glass tubes; transferring metal wires / carbon fibers for direct drawing of the microelectrodes; sealing the electrode tips with epoxy resin; polishing the microelectrodes; and connecting the microelectrodes. The direct drawing method of this invention produces microelectrodes with thinner insulating layers at the tips, making the polishing process simpler, more controllable, and less time-consuming. The prepared microelectrodes have an RG value (ratio of the radius of the conductor portion to the overall portion) lower than 1.41, exhibiting high spatial resolution and suitable for high-precision electrochemical and Raman spectroscopy detection in micro-regions. This invention significantly shortens the microelectrode preparation time; compared to the traditional method of vacuum heating and melting the glass tube to wrap the metal wire, the drawing time is reduced to 3-10 seconds, while the traditional method typically requires 5-10 minutes, less than 3.5% of the traditional method.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology, specifically relating to a direct pulling method for preparing single / dual-channel microelectrodes with ultrathin insulating layers. Background Technology

[0002] Metal microelectrodes, due to their excellent conductivity, high catalytic activity, and stability, have shown broad application potential in various fields such as electrochemical analysis, biosensing, energy catalysis, and materials science. For example, in biosensing, metal microelectrodes exhibit high sensitivity and selectivity, and can be used to detect neurotransmitters, metabolites, and other biomolecules. In Raman spectroscopy research, especially gold and silver microelectrodes, due to their significant surface-enhanced Raman scattering (SERS) effect, they are widely used for the detection and analysis of trace substances. Furthermore, in the field of electrocatalysis, metal microelectrodes can be used to study important redox reaction processes, including CO2 reduction, providing a powerful tool for exploring electrochemical reaction mechanisms and developing highly efficient catalytic materials. Carbon fiber electrodes, with their excellent conductivity, high specific surface area, mechanical strength, and chemical stability, have shown wide applications in electrochemistry, biosensing, energy and environment, and Raman spectroscopy. In biosensing, they exhibit good sensitivity and biocompatibility, and can be used for the dynamic detection of neurotransmitters (such as dopamine and norepinephrine) and other biomolecules (such as glucose and lactic acid). In the energy and environmental fields, carbon fiber electrodes serve as highly efficient electrocatalyst carriers, widely used in oxygen reduction, hydrogen evolution, carbon dioxide reduction reactions, as well as pollutant removal and wastewater treatment. In Raman spectroscopy studies, carbon fibers themselves can be analyzed for structural characteristics through their Raman signals, and they also serve as highly sensitive substrate materials for molecular adsorption and detection. Furthermore, carbon fiber electrodes are suitable for implantable devices such as brain-computer interfaces and electrophysiological recording, providing crucial support for neuroscience and medical research due to their high stability and low toxicity.

[0003] The main existing methods for fabricating metal microelectrodes involve melting a glass tube under vacuum to encapsulate a metal wire. Common heating methods include resistance coil heating and laser heating. Microelectrodes fabricated by resistance coil heating typically have cylindrical tips with a thick insulating glass layer, requiring subsequent tedious polishing to form a conical structure, a difficult process. While laser heating allows for finer heating control, it usually cannot draw the metal wire to the micrometer level, but rather to the nanometer level. Furthermore, laser heating drawing typically requires multiple steps, and the polishing process is also time-consuming. Traditional fabrication methods are complex, time-consuming, and have poor repeatability. The resulting metal microelectrodes typically have a thick insulating layer (with a large RG value at the tip, generally above 6), resulting in a small effective working area and low spatial resolution, making it difficult to meet the requirements of high-resolution micro-area measurements. Therefore, developing a more efficient, simple, and reproducible method for fabricating metal and carbon fiber microelectrodes, especially one capable of fabricating single / dual-channel microelectrodes with ultrathin cutting-edge insulating layers and high spatial resolution, has become an urgent need for current research and applications. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a direct drawing method for preparing single / dual-channel microelectrodes with ultrathin insulating layers. This method involves directly drawing metal wires or carbon fibers into a glass tube, sealing and curing the electrode tip with epoxy resin, and polishing the electrode tip to expose the electrode surface. The resulting single / dual-channel microelectrodes have ultrathin insulating layers and high spatial resolution, providing an efficient solution for micro-area measurements in biological and chemical systems that combine electrochemistry and surface-enhanced Raman spectroscopy (SERS).

[0005] To achieve the above objectives, the technical solution of the present invention is: a direct pulling method for preparing single / dual-channel microelectrodes with ultrathin insulating layers, comprising the following steps:

[0006] (1) Design of single / dual channel silicate glass tubes: The outer diameter of single channel silicate glass tubes ranges from 0.7 to 2.0 mm, the outer diameter of dual channel silicate glass tubes ranges from 1.0 to 1.6 mm, and the inner diameter of each single-hole glass tube ranges from 0.4 to 0.6 mm. The purpose of designing dual channel glass tubes is to ensure that their structural dimensions meet the preparation standards and experimental requirements, and to meet the operating range of the stretching apparatus. The spacing between the dual channel glass tubes is 0.15 to 0.25 mm, and the wall thickness of the single-hole glass tube is 0.15 to 0.25 mm to ensure structural stability.

[0007] (2) Transfer of metal wire / carbon fiber: Transfer a single metal wire along the axial direction of a single-channel silicate glass tube to the middle position in the channel, or transfer two metal wires / carbon fibers along the axial direction of a double-channel silicate glass tube to the middle position in the two channels respectively, to ensure that there is a metal wire / carbon fiber in each channel.

[0008] (3) Direct drawing of microelectrodes: Fix the two ends of the single / dual channel silicate glass tube containing metal wire / carbon fiber in step (2) on the slider of the laser drawing instrument, adjust the parameters of the drawing instrument, and directly draw out the microelectrode with an extremely thin glass layer wrapped around the tip.

[0009] (4) Epoxy resin sealing of electrode tip: Immerse the tip of the single / dual channel microelectrode prepared in step (3) into epoxy resin so that the epoxy resin fills the gap between the tip metal wire or carbon fiber and the glass wall; then place the single / dual channel microelectrode at high temperature to cure the epoxy resin.

[0010] (5) Microelectrode polishing: Use a grinding needle to polish the single / dual channel microelectrode in step (4), observe the polishing process through a microscope until the surface of the metal wire or carbon fiber is exposed.

[0011] (6) Microelectrode connection: Connect the microelectrode that has been polished in step (5) by inserting the wire into the glass tube at the end of the electrode until it contacts the metal wire or carbon fiber in the channel to achieve connection.

[0012] The maximum spacing and wall thickness between the two glass tubes should not exceed 0.25mm (0.25mm is the thickest glass tube currently in use). The minimum spacing and wall thickness are due to limitations in the glass tube processing technology; smaller spacing and wall thickness may lead to glass tube processing failure. Increasing the spacing and wall thickness will result in higher temperature and tension parameter settings during the drawing process, reducing the success rate of drawing and causing the tip insulation layer to become thicker after drawing.

[0013] In a preferred embodiment of the present invention, the length of the metal wire and carbon fiber in step (2) is 0.5-10 cm.

[0014] In a preferred embodiment of the present invention, the metal wire in step (2) includes one of Au wire, Ag wire, Cu wire, and Pt wire; the diameter of the Au wire is 5-50 μm; the diameter of the Ag wire, Cu wire, and Pt wire is 18-50 μm; and the diameter of the carbon fiber is 5-33 μm.

[0015] In a preferred embodiment of the present invention, the specific method for transferring the metal wire / carbon fiber in step (2) is as follows: the operation of transferring the metal wire into the glass tube can be carried out using different methods depending on the length: for metal wires with a length of 0.5-5cm, first insert one end of the metal wire horizontally into the glass tube, then stand the glass tube vertically, and gently tap the other end of the glass tube on the table to move the metal wire to the center position inside the tube; when the length of the metal wire used exceeds 5cm, connect one end of the glass tube to the vacuum pump, hold one end of the metal wire, start the vacuum pump, and then use the glass tube to suck in the metal wire. After turning off the vacuum pump, release your finger, and then gently tap the glass tube vertically to ensure that the metal wire is in the center. When transferring carbon fiber to the dual-channel glass tube, use the vacuum pump to suck the carbon fiber into the two channels respectively.

[0016] In a preferred embodiment of the present invention, the drawing instrument in step (3) is a resistance wire heating drawing instrument or a laser drawing instrument.

[0017] More preferably, the resistance wire heating and drawing instrument is a PC100 manufactured by NARISHIGE Corporation of Japan. The parameter adjustment includes the number of gravity weights (0-4), the adjustment of the up and down valves (up: 1-5, down: 2-10), the resistance wire heating power range of 40-99, and the ability to select a one-step or two-step drawing program.

[0018] Preferably, the laser drawing instrument is a P2000 manufactured by Sutter Corporation, USA. Parameter adjustments include HEAT (laser power), FILAMENT (length of the laser-heated area), VELOCITY (pre-stretch speed), DELAY (delay time), and PULL (stretch force), with setting ranges of 280-540, 1-5, 3-60, 100-200, and 40-255, respectively. One to three lines of programming can be set as needed. By adjusting the laser drawing instrument parameters, the cone angle of the microelectrode tip and the bonding length between the glass wall and the metal wire can be precisely controlled, ensuring the controllability of the fabrication process.

[0019] In a preferred embodiment of the present invention, when sealing the tip of the metal microelectrode with epoxy resin in step (4), the immersion depth is 0.5-5 mm and the immersion time is 1-5 min.

[0020] In a preferred embodiment of the present invention, after the epoxy resin impregnation in step (4) is completed, the microelectrode is dried at a drying temperature of 60-150°C for 4-24 hours.

[0021] In a preferred embodiment of the present invention, when the microelectrodes are connected in step (6), the wires used can be iron wire, nickel wire or silver wire. The connection can be achieved when the wire is inserted into the end of the glass tube and touches the metal wire or carbon fiber.

[0022] In a preferred embodiment of the present invention, in step (6), to ensure connectivity, the wire can be coated with conductive carbon powder before being inserted into the glass tube.

[0023] In a preferred embodiment of the present invention, step (6) further includes using hot melt adhesive to fix the wire to the end of the glass tube after the microelectrode is connected, so as to avoid poor contact caused by the movement of the wire during the test.

[0024] Single / dual-channel metal microelectrodes and dual-channel carbon microelectrodes were prepared by the above drawing method.

[0025] Applications of a single / dual-channel metal microelectrode and a dual-channel carbon microelectrode.

[0026] The aforementioned application areas include, but are not limited to, high spatiotemporal resolution electrochemical-Raman bifunctional microprobes, measurement and mechanism study of micromolecules in biological and chemical systems, and exploration of complex chemical and biological mechanisms involving multiple molecules.

[0027] After polishing, the metal microelectrode or carbon fiber can be tested by cyclic voltammetry curves to observe whether the curve shape is standard, and the steady-state current value is compared with the theoretical value.

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

[0029] 1. The insulating layer of the microelectrode tip prepared by the direct pulling method of the present invention is thinner, which makes the polishing process simpler, more controllable, and less time-consuming;

[0030] 2. The microelectrode prepared by the direct pulling method of the present invention can have an RG value of less than 1.41, which has higher spatial resolution and is suitable for the detection of extracellular neurotransmitters at the single-cell level;

[0031] 3. The direct drawing method of the present invention significantly shortens the microelectrode preparation time. Compared with the traditional method of vacuum heating and melting the glass tube wrapped with metal wire, the drawing time is shortened to 3-10 seconds, while the traditional method usually takes 5-10 minutes, which is less than 3.5% of the traditional method.

[0032] 4. The direct pulling method of the present invention is simple, easy to implement, highly controllable and reproducible, and is suitable for preparing microelectrodes of various sizes;

[0033] 5. The direct drawing method of the present invention is applicable to the production of microelectrodes of various metal materials (such as Pt, Ag, Cu). The Pt, Ag, and Cu microelectrodes produced also have ultra-thin insulating layers. These microelectrodes can be applied to a variety of fields. For example, Pt microelectrodes are suitable for detecting slow-kinetic reactions (such as the redox reaction of H2O2), while Ag and Cu electrodes can be used for Raman detection and the study of reaction processes such as CO2 reduction. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the direct drawing process steps of a single-channel Au wire microelectrode in Embodiment 1 of the present invention;

[0035] Figure 2 This is a schematic diagram of the direct drawing process steps of the dual-channel Au wire microelectrode in Embodiment 3 of the present invention;

[0036] Figure 3 This is an optical microscope image of the tip of the Au wire microelectrode after drawing in Embodiment 1 of the present invention;

[0037] Figure 4 This is an optical microscope image of the Au wire microelectrode during grinding using a needle grinding machine, as shown in Embodiment 1 of the present invention.

[0038] Figure 5 This is an optical microscope image of the tip of the Au wire microelectrode after polishing in Embodiment 1 of the present invention;

[0039] Figure 6 This is a scanning electron microscope (SEM) image of the tip of the Au wire microelectrode after polishing in Embodiment 1 of the present invention;

[0040] Figure 7 This is a photograph of the Au wire microelectrode connecting wires in Embodiment 1 of the present invention, which are fixed to the end of the glass tube with hot melt adhesive;

[0041] Figure 8 This is a cyclic voltammogram obtained by scanning the Au wire microelectrode in 10mM potassium ferricyanide solution after polishing in Example 1 of the present invention.

[0042] Figure 9 This is an optical microscope image of the tip of the Ag, Cu, Pt microelectrode after being drawn in Embodiment 2 of the present invention;

[0043] Figure 10 This is an optical microscope image of the polished Ag, Cu, Pt microelectrode tip portion in Embodiment 2 of the present invention;

[0044] Figure 11 This is an optical microscope image of the tip portion of the drawn dual-channel Au wire microelectrode in Embodiment 3 of the present invention;

[0045] Figure 12 This is an optical microscope image of the tip of the dual-channel Au wire microelectrode after polishing in Embodiment 3 of the present invention;

[0046] Figure 13 This is a cyclic voltammogram obtained by scanning the dual-channel Au wire microelectrode in a 10mM potassium ferricyanide solution after polishing in Example 3 of the present invention.

[0047] Figure 14This is a scanning electron microscope (SEM) image of the tip of the dual-channel Au wire microelectrode after polishing in Embodiment 3 of the present invention;

[0048] Figure 15 This is an optical microscope image of the tip portion of the drawn dual-channel carbon fiber microelectrode in Embodiment 4 of the present invention;

[0049] Figure 16 This is a scanning electron microscope (SEM) image of the tip of the dual-channel carbon fiber microelectrode after polishing in Embodiment 4 of the present invention;

[0050] Figure 17 This is a cyclic voltammogram obtained by scanning the dual-channel carbon fiber microelectrode in a 10mM potassium ferricyanide solution after polishing in Embodiment 4 of the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0052] The grinding device used in the following examples is a microelectrode grinding device manufactured by Kedou (Suzhou) Brain-Computer Technology Co., Ltd., with a grinding disc polishing specification of 1μm.

[0053] Example 1

[0054] A single-channel Au wire microelectrode, according to Figure 1 It is prepared by the following process steps:

[0055] (1) Design the dimensions of a single-channel silicate glass tube: Select a single-channel silicate glass tube with an outer diameter of 1.2 mm, an inner diameter of 0.69 mm, and a length of 10 cm.

[0056] (2) Transfer Au wire: Insert a 3cm long and 13μm diameter Au wire horizontally into one end of the glass tube, stand the glass tube vertically, and tap the other end on the table to move the Au wire along the axial direction of the glass tube to the middle position in the glass tube channel.

[0057] (3) Drawing the glass tube containing Au wire: The two ends of the glass tube containing Au wire were fixed to the slider module of the P-2000 laser drawing instrument manufactured by Sutter Corporation, USA. A drawing parameter program was set as follows: HEAT=370, FILAMENT=1, VELOCITY=12, DELAY=128, PULL=100. After drawing, a pair of symmetrical Au wire microelectrodes with ultra-thin glass layers at their tips were obtained. After drawing, the diameter of the gold wire in the microelectrodes became thinner to 11.2 μm, the outer diameter was 12.8 μm, and the glass layer thickness was less than 2 μm. Under an optical microscope, it could be observed that a section of Au wire at the tip of the glass tube was wrapped by the glass tube, such as... Figure 3 As shown.

[0058] (4) Seal the tip of the glass tube with epoxy resin: Although the tip of the Au wire microelectrode was observed to be wrapped in glass under an optical microscope, there may still be gaps; Immerse the tip of the Au wire microelectrode in epoxy resin to a depth of about 2 mm, wait for 3 minutes and then take it out; Place the sealed electrode horizontally on a glass dish and fix it, place it in a forced-air drying oven, set the temperature to 100℃ and the drying time to 8 hours.

[0059] (5) Polishing the tip of the Au wire microelectrode: Use a microelectrode grinding tool to polish the tip to expose the Au surface and form a regular shape; polishing at a vertical 90° angle will produce a disc shape, and polishing at a 45° angle will produce an elliptical shape. The specific steps are as follows: fix the electrode on the micro-operation device and slowly lower it until it contacts the grinding disc. After each 30-second polishing, adjust the micro-operation knob to rotate 5° clockwise to control the electrode to move downwards. Repeat the operation until the Au wire surface is completely exposed. Figure 4 An optical microscope image of an Au wire microelectrode during grinding using a needle grinder; Figure 5 This is an optical microscope image of the tip of the Au wire microelectrode after polishing; Figure 6 This is a scanning electron microscope (SEM) image of the tip of the Au wire microelectrode after polishing.

[0060] (6) Connection of the single-channel Au wire microelectrode: After polishing, insert a 6cm long, 0.1mm diameter iron wire from the end of the electrode until it contacts the Au wire. After passing the electrochemical test, fix the iron wire to the end of the glass tube with hot melt adhesive, such as... Figure 7 As shown.

[0061] (7) Electrochemical Testing and Characterization: The electrolyte solution was 10 mM potassium ferrocyanide (Sigma), prepared with ultrapure water (Millipore, 18.2 MΩ*cm). Cyclic voltammetry was performed using an electrochemical workstation (Shanghai Chenhua Co., Ltd., CHI 840D) with a potential range of 0-0.6 V (vs. Ag / AgCl) and a scan rate of 50 mV / s. A single-channel Au microelectrode was used as the working electrode, and an Ag / AgCl electrode (Shanghai Chenhua Co., Ltd., CHI111) was used as the counter and reference electrodes. The results are as follows. Figure 8 As shown, from Figure 8 It can be seen that the obtained cyclic voltammetry curves exhibit typical "S"-shaped steady-state polarization characteristics, with small charging current and a stable plateau. According to the formula, the steady-state theoretical current of the polished 11.2 μm diameter Au microelectrode in 10 mM K3[Fe(CN)6] is 23.04 nA, and the actual measured value is 22.71 nA, which is basically consistent with the theoretical value.

[0062] The single-channel Au wire microelectrode has an RG value (ratio of electrode conductor radius to total radius) of less than 1.41, resulting in higher spatial resolution and suitability for single-cell level extracellular neurotransmitter detection. Furthermore, due to its inherent Raman enhancement properties, Au material can be further surface-treated to form nanostructures for use as SERS probes. Combined with electrochemical analysis techniques, this enables independent and simultaneous detection of electroactive and non-electroactive molecules.

[0063] Example 2

[0064] The preparation methods for the single-channel Ag wire microelectrode, single-channel Cu wire microelectrode, and single-channel Pt wire microelectrode are the same as those for the Au wire microelectrode in Example 1. The diameter of the Ag, Cu, and Pt wires used is 25 μm and the length is 4 cm.

[0065] Optical microscope images of the tips of Ag, Cu, and Pt microelectrodes after drawing are shown below. Figure 9 As shown, optical microscope images of the tips of the Ag, Cu, and Pt microelectrodes after polishing are as follows: Figure 10 As shown.

[0066] Example 3

[0067] A dual-channel Au wire microelectrode, according to Figure 2 It is prepared by the following process steps:

[0068] (1) Design of the dimensions of the dual-channel silicate glass tube: The dual-channel silicate glass tube is of the "θ" shape, with an outer diameter of 1.2 mm, a glass wall thickness of 0.15 mm, and an overall length of 10 cm.

[0069] (2) Transfer Au wires: Take two Au wires, each 8 cm long and 13 μm in diameter, and fix one end of each wire to the worktable (using fingers or tape). Slightly separate the other end. Connect one end of the glass tube to the vacuum pump, start the vacuum, and draw the two Au wires into the two channels of the glass tube along the axial direction, ensuring that there is one Au wire in each channel. The Au wires are positioned in the middle of the channels of the glass tube along the axial direction. Use a blade to cut off any excess Au wires to complete the transfer.

[0070] (3) Drawing a double-channel glass tube equipped with Au wire: Fix both ends of the double-channel glass tube equipped with Au wire to the slider module of the P-2000 laser drawing instrument manufactured by Sutter Corporation in the United States, and set two lines of drawing program.

[0071] LINE1: HEAT=540, FILAMENT=1, VELOCITY=10, DELAY=128, PULL=60.

[0072] LINE2: HEAT=460, FILAMENT=1, VELOCITY=10, DELAY=128, PULL=40.

[0073] After the procedure, a dual-channel Au wire microelectrode with an ultrathin insulating layer at its tip was obtained. Under an optical microscope, it can be observed that the two Au wires within the two channels at the tip of the glass tube are encased in glass, as shown below. Figure 11 As shown.

[0074] (4) Seal the tip of the glass tube with epoxy resin: Immerse the tip of the Au wire microelectrode into the epoxy resin to a depth of about 2 mm, wait for 3 minutes and then take it out; place the sealed electrode horizontally on the glass dish and fix it, place it in the forced-air drying oven, set the temperature to 100℃ and the drying time to 8 hours.

[0075] (5) Polishing the tip of the gold wire microelectrode: A microelectrode grinding tool is used to polish the tip to expose the Au surface and form a regular shape; polishing at a vertical 90° angle yields a disc shape, while polishing at a 45° angle yields an elliptical shape. The specific steps are as follows: Fix the electrode on the micro-operation device and slowly lower it until it contacts the grinding disc. After each 30-second polishing session, adjust the micro-operation knob clockwise by 5° to control the electrode's downward movement. Repeat this operation until the Au wire surface is fully exposed. During polishing, pay attention to adjusting the position of the dual-channel glass tube to ensure that the Au wires in both channels contact the grinding disc simultaneously, and that the exposed surface areas of the Au wires in both channels are approximately the same after polishing. The optical microscope image of the tip of the dual-channel Au wire microelectrode after polishing is shown below. Figure 12 As shown, the scanning electron microscope (SEM) image of the tip of the dual-channel Au wire microelectrode after polishing is as follows: Figure 13 As shown; the cyclic voltammogram obtained by scanning in a 10 mM potassium ferricyanide solution, as shown. Figure 14 As shown;

[0076] (6) Connection of dual-channel Au wire microelectrode: After the electrode is polished, two 6cm long iron wires with a diameter of 0.1mm are inserted into the two channels at the end of the electrode and moved to the conical part of the electrode until they come into contact with the Au wire.

[0077] (7) Electrochemical Testing and Characterization: Electrochemical testing and characterization were performed. After passing the tests, two iron wires were fixed to the ends of the glass tube with hot melt adhesive. The electrochemical testing system and conditions were the same as in step 7 of Example 1 (the electrolyte solution was 10 mM potassium ferrocyanide (Sigma), and the solution was prepared with ultrapure water (Millipore, 18.2 MΩ*cm). Cyclic voltammetry was performed using an electrochemical workstation (Shanghai Chenhua Co., Ltd., CHI 840D), with a potential range of 0-0.6 V (vs. Ag / AgCl) and a scan rate of 50 mV / s. A dual-channel Au microelectrode was used as the working electrode, and an Ag / AgCl electrode (Shanghai Chenhua Co., Ltd., CHI111) was used as the counter electrode and reference electrode. The two-electrode system was tested, and the cyclic voltammetry curves of the two channels were measured separately. The results are as follows: Figure 14 As shown, from Figure 14 It can be seen that the cyclic voltammetry curves of both channels exhibit typical "S"-shaped steady-state current characteristics, with small charging current and a stable plateau. According to the formula, the diameters of the two gold wires at the tip after polishing are 10.21 μm and 10.43 μm, respectively. The theoretical steady-state currents in 10 mM K3[Fe(CN)6] are 21.08 nA and 21.53 nA, respectively, while the actual measured values ​​are 20.89 nA and 21.40 nA, respectively, which are basically consistent with the theoretical values.

[0078] Example 4

[0079] A dual-channel carbon fiber disk microelectrode is prepared according to the following steps:

[0080] (1) Design of the dimensions of the dual-channel silicate glass tube: The dual-channel silicate glass tube is of the "θ" shape, with an outer diameter of 1.2 mm, a glass wall thickness of 0.15 mm, and an overall length of 10 cm.

[0081] (2) Transfer of carbon fiber: Take two carbon fibers with a length of 8cm and a diameter of 10μm, fix one end of them on the operating table (you can fix them with your fingers or tape), and slightly separate the other end; connect one end of the glass tube to the vacuum pump, start the vacuum, and suck the carbon fibers into the two channels of the glass tube respectively, ensuring that there is a carbon fiber in the middle of each channel; use a blade to cut off the excess carbon fiber to complete the transfer.

[0082] (3) Drawing a dual-channel glass tube containing carbon fiber: A PC100 resistance wire heating drawing instrument manufactured by NARISHIGE Corporation of Japan was used, equipped with four gravity weights. The scales of the upper and lower stop valves were set to 4 and 8 respectively. A one-step drawing program was adopted, and the temperature heating parameter was set to 54.0. The two ends of the dual-channel glass tube containing carbon fiber were fixed to the PC100. The program was started, and the coil heated the glass tube. Under the action of gravity weights, the glass tube was drawn in half. The carbon fiber did not break in two along with the glass tube, so scissors were used to cut the carbon fiber. The optical microscope image of the tip of the dual-channel carbon fiber microelectrode after drawing is shown below. Figure 15 As shown.

[0083] Alternatively, the P-2000 laser drawing instrument from Sutter Corporation (USA) can be used for drawing. The operation steps are the same as in Example 3, and the drawing parameters are set as follows:

[0084] LINE1: HEAT=370, FILAMENT=1, VELOCITY=10, DELAY=128, PULL=90.

[0085] After the procedure, a pair of dual-channel carbon fiber microelectrodes with ultrathin insulating layers at their tips were obtained. Under an optical microscope, it could be observed that the two carbon fibers at the tips of the glass tube were wrapped in the glass tube.

[0086] (4) Seal the tip of the glass tube with epoxy resin: Immerse the tip of the carbon fiber microelectrode into epoxy resin to a depth of about 2 mm, wait for 3 minutes and then take it out; place the sealed electrode horizontally on the glass dish and fix it, place it in the forced-air drying oven, set the temperature to 100℃ and the drying time to 8 hours.

[0087] (5) Grinding and polishing the tip of the carbon fiber microelectrode: A microelectrode grinding tool is used to grind and polish the tip to expose the carbon fiber surface and form a regular shape; grinding at a vertical 90° angle yields a disc shape, while grinding at a 45° angle yields an elliptical shape. The specific steps are as follows: Fix the electrode on the micro-manipulation device and slowly lower it until it contacts the grinding disc. After each 30-second grinding, adjust the micro-manipulation knob clockwise by 5° to control the electrode's downward movement. Repeat this operation until the carbon fiber surface is completely exposed. During grinding, pay attention to adjusting the position of the dual-channel glass tube to ensure that the carbon fibers in both channels contact the grinding disc simultaneously, and that the exposed surface areas of the carbon fibers in both channels are approximately the same after grinding. The scanning electron microscope (SEM) image of the tip of the dual-channel carbon fiber microelectrode after grinding is shown below. Figure 16 As shown.

[0088] (6) Connection of dual-channel carbon fiber microelectrode: After the electrode is polished, two 6cm long iron wires with a diameter of 0.1mm are inserted into the two channels at the end of the electrode and moved to the conical part of the electrode until they come into contact with the carbon fiber.

[0089] (7) Electrochemical Testing and Characterization: Electrochemical testing and characterization were performed. After passing the tests, two iron wires were fixed to the ends of the glass tube using hot melt adhesive. The cyclic voltammetry images obtained by scanning the dual-channel carbon fiber microelectrode in a 10mM potassium ferricyanide solution after polishing are shown below. Figure 17 As shown, after polishing 10μm carbon fibers at 45°, the theoretical steady-state current in a 10mM potassium ferricyanide solution is 20.46nA. In actual testing, the steady-state currents of the two channels were 20.39nA and 23.41nA, respectively, with only a small difference from the theoretical value. The slightly higher current in one channel is likely due to minor inhomogeneities during the polishing process.

[0090] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A direct draw method for fabricating single / dual channel microelectrodes with ultrathin insulation layer, characterized in that, The method comprises the following steps: (1) design single / dual channel silicate glass tube: the outer diameter of single channel silicate glass tube is 0.7-2.0 mm, the outer diameter of dual channel silicate glass tube is 1.0-1.6 mm, the inner diameter of each channel is 0.4-0.6 mm, the spacing between the two channels of dual channel glass tube is 0.15-0.25 mm, and the wall thickness of single hole glass tube is 0.15-0.25 mm; (2) transfer metal wire / carbon fiber: transfer a single metal wire to the middle position of the channel of single channel silicate glass tube in an axial direction, or transfer two metal wires / carbon fibers to the middle positions of the two channels of dual channel silicate glass tube in an axial direction, respectively, to ensure that there is a metal wire / carbon fiber in each channel; (3) direct drawing of microelectrode: fix the single / dual channel silicate glass tube containing metal wire / carbon fiber in step (2) at both ends of the slider of a drawing instrument, adjust the parameters of the drawing instrument, and directly draw a microelectrode with a sharp tip wrapped in a thin glass layer; (4) seal the electrode tip with epoxy resin: immerse the tip of the single / dual channel microelectrode prepared in step (3) in epoxy resin to fill the gap between the tip metal wire or carbon fiber and the glass wall; then place the single / dual channel microelectrode in a high temperature environment to cure the epoxy resin; (5) polish the microelectrode: polish the single / dual channel microelectrode in step (4) using a needle polisher, and observe the polishing process through a microscope until the surface of the metal wire or carbon fiber is exposed; (6) connect the microelectrode: connect the microelectrode polished in step (5) by inserting a wire into the glass tube at the end of the electrode until it contacts the metal wire or carbon fiber in the channel to achieve connection; wherein the metal wire is drawn using a laser drawing instrument, and the carbon fiber is drawn using a laser drawing instrument or a resistance wire heating drawing instrument; the parameter adjustment of the resistance wire heating drawing instrument includes gravity weight number of 0-4, upper action of 1-5, lower action of 2-10, and resistance wire heating power range of 40-99; the parameter adjustment of the laser drawing instrument includes HEAT of 280-540, FILAMENT of 1-5, VELOCITY of 3-60, DELAY of 100-200, and PULL of 40-255; the RG value of the microelectrode is lower than 1.

41.

2. The direct drawing method for preparing single / dual channel microelectrode with ultra-thin insulation layer according to claim 1, wherein, the length of the metal wire and carbon fiber in step (2) is 0.5-10 cm, the metal wire includes one of Au wire, Ag wire, Cu wire and Pt wire, the diameter of Au wire is 5-50 μm, the diameters of Ag wire, Cu wire and Pt wire are 18-50 μm, and the diameter of carbon fiber is 5-33 μm.

3. The direct drawing method for preparing single / dual channel microelectrode with ultra-thin insulation layer according to claim 1, wherein, when the metal microelectrode tip is sealed with epoxy resin in step (4), the immersion depth is 0.5-5 mm, and the soaking time is 1-5 min.

4. The direct drawing method for preparing single / dual channel microelectrode with ultra-thin insulation layer according to claim 1, wherein, after the epoxy resin soaking in step (4) is completed, the microelectrode is dried at a drying temperature of 60-150 ℃ for 4-24 h.

5. The direct drawing method for preparing single / dual channel microelectrode with ultra-thin insulation layer according to claim 1, wherein, the wire used for microelectrode connection in step (6) is one of iron wire, nickel wire or silver wire.

6. The direct drawing method for fabricating single / dual channel microelectrode with ultra-thin insulation layer according to claim 1, wherein, In step (6), the wire can be coated with conductive carbon powder before being inserted into the glass tube to ensure the connection.

7. The direct drawing method for fabricating single / dual channel microelectrode with ultra-thin insulation layer according to claim 1, wherein, In step (6), after the microelectrode is connected, the wire is fixed at the end of the glass tube using hot melt glue to avoid poor contact caused by movement of the wire during testing.

8. The single / dual channel metal microelectrode and dual channel carbon microelectrode prepared by the direct drawing method for preparing single / dual channel microelectrodes with ultrathin insulating layer according to any one of claims 1-7.

9. Use of the single / dual channel metal microelectrode and dual channel carbon microelectrode according to claim 8.

Images