Composite microneedle structure as well as preparation method and use method thereof

Abstract

The invention relates to a composite microneedle structure, which comprises a circuit board and a microneedle, the microneedle comprises a plurality of soft needles, the plurality of soft needles are fixed with the circuit board, each soft needle is provided with a plurality of neural electrodes, and the plurality of neural electrodes are electrically connected with the circuit board; the microneedle further comprises a plurality of hard needles, each hard needle is fixed to the corresponding soft needle through a connecting column, and the connecting columns are made of electrochemical dissolving materials. The connecting column is arranged between the hard needle and the soft needle, the hard needle and the soft needle are connected, the soft needle is brought into the brain tissue of a patient through the hard needle, the implanting efficiency of the soft needle is improved, after the connecting column is subjected to electrochemical dissolution, the hard needle can be pulled out, and the soft needle is left in the brain tissue of the patient; the technical problems that in the prior art, a hard needle structure can damage brain tissue during long-term implantation, a soft needle structure is prone to deformation, implantation needs to be assisted by external equipment, and the implantation effect is not ideal are solved.

Description

Technical Field

[0001] The present application relates to the field of brain-computer interface neural microelectrodes, and specifically to a composite microneedle structure and a preparation method and a use method thereof. Background Art

[0002] Currently, microelectrodes implanted in the nervous system for a long time have a wide range of applications in the field of medical research. They can directly record changes in the discharge frequency of individual neurons, facilitating postoperative observation of patients.

[0003] In the related technologies, the microneedle structures of invasive microelectrodes are mostly single-type electrodes, such as the Michigan electrode and Utah electrode with a hard needle structure, and the polyimide electrode with a soft needle structure. The hard needle structure has a higher hardness and may cause damage to brain tissue during long-term implantation; the soft needle structure has good flexibility and excellent biocompatibility. Although it causes less damage to brain tissue during long-term implantation, it is prone to deformation and requires the assistance of external equipment for implantation, and the implantation effect is not ideal.

[0004] Therefore, it is necessary to design a new composite microneedle structure to overcome the above problems. Summary of the invention

[0005] The present application provides a composite microneedle structure and a preparation method and a use method, which can solve the technical problems in the related art that the hard needle structure will cause damage to brain tissue during long-term implantation, the soft needle structure is prone to deformation, and the implantation requires the assistance of external equipment, resulting in unsatisfactory implantation effects.

[0006] In a first aspect, an embodiment of the present application provides a composite microneedle structure, comprising: a circuit board and a microneedle, wherein the microneedle comprises a plurality of soft needles, wherein the plurality of soft needles are fixed to the circuit board, each of the soft needles is provided with a plurality of nerve electrodes, and the plurality of nerve electrodes are electrically connected to the circuit board; the microneedle also comprises a plurality of hard needles, wherein each of the hard needles is fixed to the corresponding soft needle via a connecting column, and the connecting column is made of an electrochemically dissolving material.

[0007] In combination with the first aspect, in one embodiment, protrusion structures are provided on both sides of each of the soft needles.

[0008] In combination with the first aspect, in one embodiment, a chamfer is provided on the outer side of the protruding structure.

[0009] In combination with the first aspect, in one implementation, the circuit board is provided with a first welding position and a second welding position, the first welding position is electrically connected to the second welding position, a plurality of the soft needles are fixedly disposed at the first welding position, and a microstrip line is fixedly disposed at the second welding position.

[0010] In combination with the first aspect, in one embodiment, each of the soft needles is provided with a through hole, and the connecting post passes through the through hole to connect the soft needle and the hard needle.

[0011] In combination with the first aspect, in one implementation, the height of the connecting pillar is set to 20-100 μm.

[0012] In combination with the first aspect, in one embodiment, the hard needle is made of metal material, and the soft needle is made of flexible polymer material.

[0013] In a second aspect, the present invention provides a method for preparing a composite microneedle structure, which comprises the following steps:

[0014] S1: depositing a first sacrificial layer on a substrate, depositing a metal layer on the first sacrificial layer, and obtaining a plurality of hard needles through photolithography and patterning.

[0015] S2: depositing a second sacrificial layer on the hard needle and preparing a flexible layer on the second sacrificial layer.

[0016] S3: A lead layer, an insulating layer and an electrode layer are sequentially prepared on the flexible layer, and a plurality of soft needles and a plurality of neural electrodes on the soft needles are obtained through photolithography and patterning.

[0017] S4: removing the first sacrificial layer and the second sacrificial layer, and preparing a connecting column between the hard needle and the soft needle.

[0018] In conjunction with the second aspect, in one embodiment, before preparing the connecting column between the hard needle and the soft needle, the method further includes:

[0019] S401: etching the flexible layer and the second sacrificial layer at a preset position of the lead layer to form a through hole penetrating the flexible layer and the second sacrificial layer.

[0020] In a third aspect, the present invention provides a method for using a composite microneedle structure, which comprises the following steps:

[0021] The first step: implant the microneedles into the patient's brain tissue and apply a safe voltage to multiple hard needles.

[0022] Step 2: After the connecting column dissolves, withdraw the multiple hard needles and retain the multiple soft needles.

[0023] The beneficial effects brought by the technical solution provided in the embodiments of the present application include:

[0024] A connecting column is provided between the hard needle and the soft needle to connect the hard needle and the soft needle, and the hard needle is used to bring the soft needle into the patient's brain tissue to improve the implantation efficiency of the soft needle. After the connecting column is electrochemically dissolved, the hard needle can be pulled out and the soft needle can be left in the patient's brain tissue. This solves the technical problems in related technologies that the hard needle structure may cause damage to the brain tissue during long-term implantation, the soft needle structure is prone to deformation, and external equipment is required to assist implantation, resulting in unsatisfactory implantation effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 A schematic diagram of the structure of a composite microneedle structure provided in an embodiment of the present application;

[0027] Figure 2 A schematic diagram of the structure of the connection between the soft needle and the hard needle provided in the embodiment of the present application;

[0028] Figure 3 A schematic diagram of the structure of a circuit board provided in an embodiment of the present application;

[0029] Figure 4 A schematic diagram of a process for preparing a composite microneedle structure provided in an embodiment of the present application.

[0030] In the figure: 1. circuit board; 101. first welding position; 102. second welding position; 2. microneedle; 201. soft needle; 202. neural electrode; 203. hard needle; 204. connecting column; 205. protruding structure; 3. microstrip line; 4. substrate; 5. first sacrificial layer; 6. metal layer; 7. second sacrificial layer; 8. flexible layer; 9. lead layer; 10. insulating layer; 11. electrode layer. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0032] The embodiments of the present application provide a composite microneedle structure and a preparation method and a use method, which can solve the technical problems that hard needle structures may cause damage to brain tissue during long-term implantation, soft needle structures are prone to deformation, require external equipment to assist in implantation, and have unsatisfactory implantation effects.

[0033] See also Figure 1 and Figure 2 As shown, an embodiment of the present application provides a composite microneedle structure, which includes: a circuit board 1 and a microneedle 2, wherein the microneedle 2 includes a plurality of soft needles 201, and the plurality of soft needles 201 are fixed to the circuit board 1, and each of the soft needles 201 is provided with a plurality of nerve electrodes 202, and the plurality of nerve electrodes 202 are electrically connected to the circuit board 1; the microneedle 2 also includes a plurality of hard needles 203, and each of the hard needles 203 is fixed to the corresponding soft needle 201 through a connecting column 204, and the connecting column 204 uses an electrochemically dissolving material.

[0034] In this embodiment, the circuit board 1 can be set as a CMOS (complementary metal oxide semiconductor) circuit board, the circuit board 1 is welded to the multiple soft needles 201, the multiple soft needles 201 can be set as four soft needles 201 or more soft needles 201, preferably, the multiple soft needles 201 are set as four soft needles 201, the number of the hard needles 203, the soft needles 201 and the connecting column 204 corresponds, the multiple neural electrodes 202 can be set as eight neural electrodes 202 or more neural electrodes 202, the hard needle 203 is used to assist the soft needle 201 to be implanted into the patient's brain tissue, and the connecting column 204 can be set on the needle head of the soft needle 201 and the hard needle through MEMS (micro electromechanical system) process and welding process. 203, the connecting column 204 can also be set at other positions corresponding to the soft needle 201 and the hard needle 203, the connecting column 204 can be quickly dissolved at a set voltage, and the set voltage is a safe voltage. Demonstrably, the set voltage is set to 0.7~1V, and the connecting column 204 can be dissolved in 5~10 seconds. After the connecting column 204 is dissolved and disconnected, the multiple hard needles 203 and the multiple soft needles 201 can be detached, avoiding manual operation to detach the soft needles 201 and the hard needles 203. The connecting column 204 can be made of platinum-tungsten alloy or other electrochemically dissolving materials. Platinum-tungsten alloy has good biocompatibility, and the reactants generated by the electrochemical reaction are harmless. The reactants can be metabolized and excreted from the human body, and the products of the dissolved reactants are also harmless.

[0035] In this embodiment, a connecting column 204 is provided between the hard needle 203 and the soft needle 201 to connect the hard needle 203 and the soft needle 201, and the hard needle 203 is used to bring the soft needle 201 into the patient's brain tissue, thereby improving the implantation efficiency of the soft needle 201. After the connecting column 204 is electrochemically dissolved, the hard needle 203 can be pulled out, and the soft needle 201 can be left in the patient's brain tissue, thereby solving the technical problems in the related art that the hard needle structure may cause damage to the brain tissue during long-term implantation, the soft needle structure is prone to deformation, and the implantation effect is not ideal due to the need for external equipment.

[0036] Further, see Figure 1 and Figure 2 As shown, in some embodiments, protrusion structures 205 are provided on both sides of each soft needle 201 .

[0037] In the present embodiment, the protruding structure 205 is provided on both sides of each of the soft needles 201. Preferably, the protruding structure 205 can be provided on the needle head of each of the soft needles 201. Each of the soft needles 201 and the corresponding protruding structure 205 can be integrally formed. The protruding structure 205 can be provided in a serrated shape. The protruding structure 205 can fix the soft needle 201 to the brain tissue after the soft needle 201 and the hard needle 203 are separated, thereby avoiding electrostatic adsorption causing the hard needle 203 to carry the soft needle 201 with it during the withdrawal process, preventing the soft needle 201 from being deformed, and ensuring that the soft needle 201 remains in the brain tissue after the hard needle 203 is completely withdrawn.

[0038] Further, see Figure 1 and Figure 2 As shown, in some embodiments, the outer side of the protruding structure 205 is chamfered.

[0039] In this embodiment, the chamfer is provided on the outer side of the protruding structure 205 so that the outer side of the protruding structure 205 is arc-shaped, diamond-shaped or other shapes with a certain curvature, so as to prevent the protruding structure 205 from causing secondary damage due to excessive sharpness, and at the same time prevent electrostatic adsorption from causing the soft needle 201 to withdraw or deform when the hard needle 203 is pulled out.

[0040] Further, see Figure 1 and Figure 3 As shown, in some embodiments, the circuit board 1 is provided with a first welding position 101 and a second welding position 102, the first welding position 101 is electrically connected to the second welding position 102, the first welding position 101 is fixed with a plurality of the soft needles 201, and the second welding position 102 is fixed with a microstrip line 3.

[0041] In this embodiment, the soft needle 201 is provided with a conductive circuit, and the multiple neural electrodes 202 are electrically connected to the first welding position 101 through the conductive circuit inside the soft needle 201, and are electrically connected to the microstrip line 3 through the second welding position 102, and then electrically connected to the external PCB through the microstrip line 3, so that the signal of the microneedle 2 can be output to the external PCB, and the multiple neural electrodes 202 collect the patient's brain data, and then perform preliminary data processing on the circuit board 1, and then transmit it to the external PCB for analysis through the microstrip line 3, which is convenient for postoperative imaging examination. The multiple soft needles 201 are connected to the circuit board 1 at the first welding position 101 using a reverse welding process, and the microstrip line 3 is connected to the circuit board 1 at the second welding position 102 using a reverse welding process to ensure the welding stability between the microneedle 2 and the circuit board 1, and improve the stability and accuracy of signal transmission.

[0042] Further, see Figure 1 and Figure 2 As shown, in some embodiments, each of the soft needles 201 is provided with a through hole, and the connecting column 204 passes through the through hole to connect the soft needle 201 and the hard needle 203 .

[0043] In this embodiment, the needle head of each soft needle 201 can be provided with the through hole, and the connecting column 204 passes through the through hole to connect the soft needle 201 and the hard needle 203, so that the soft needle 201 and the hard needle 203 are fixed, ensuring that the soft needle 201 and the hard needle 203 do not undergo relative displacement during the implantation process. The through hole can also be provided at other positions of the soft needle 201, and the connecting column 204 can be provided with a solid structure or a hollow structure.

[0044] Further, see Figure 1 and Figure 2 As shown, in some embodiments, the height of the connecting pillar 204 is set to 20-100 μm.

[0045] In this embodiment, the height of the connecting column 204 can be set to 20 to 100 μm. Preferably, the height of the connecting column 204 is set to 50 μm, so that the soft needle 201 and the hard needle 203 can be connected with an appropriate gap, ensuring that the hard needle 203 can be implanted into the patient's brain tissue with the soft needle 201, while facilitating the subsequent detachment of the soft needle 201 and the hard needle 203.

[0046] Further, see Figure 1 As shown, in some embodiments, the hard needle 203 is made of metal material, and the soft needle 201 is made of flexible polymer material.

[0047] In this embodiment, the hard needle 203 can be made of gold material, silver material, platinum material, tungsten material or other metal materials with good biocompatibility. Preferably, the hard needle 203 is made of silver material. Compared with the traditional hard needle made of silicon-based material, the hard needle 203 is not easy to break, which avoids the brittle fracture of the hard needle 203 during the implantation or removal process, and improves the implantation efficiency of the soft needle 201. The soft needle 201 can be made of polyimide material, PDMS (polydimethylsiloxane) material, silicone material, polyparaxylene material or other flexible polymer high molecular materials with good biocompatibility.

[0048] See also Figure 1 and Figure 4 As shown, the present invention provides a method for preparing a composite microneedle structure, which comprises the following steps:

[0049] S1: depositing a first sacrificial layer 5 on a substrate 4, and depositing a metal layer 6 on the first sacrificial layer 5, and obtaining a plurality of hard needles 203 through photolithography and patterning.

[0050] In this embodiment, the substrate 4 can be made of silicon material or other materials. First, the substrate 4 is cleaned and dried, and then the first sacrificial layer 5 is deposited on the substrate 4. The first sacrificial layer 5 can be made of aluminum material or chromium material or other metal materials that are easily soluble in acid. Then, at least two layers of the metal layer 6 are deposited on the first sacrificial layer 5, and at least two layers of the metal layer 6 are photolithographically processed and patterned to obtain a plurality of the hard needles 203. The metal layer 6 can be made of gold material or silver material or platinum material or tungsten material or other metal materials with good biocompatibility. At least two layers of the metal layer 6 are patterned by stripping or etching process. At least two layers of the metal layer 6 can ensure that the hard needle 203 has sufficient implantation strength. The deposition process of the first sacrificial layer 5 and the metal layer 6 can adopt PVD (physical vapor deposition) or CVD (chemical vapor deposition) or evaporation.

[0051] S2 : depositing a second sacrificial layer 7 on the hard needles 203 , and preparing a flexible layer 8 on the second sacrificial layer 7 .

[0052] In this embodiment, the second sacrificial layer 7 can be made of aluminum material, chromium material, nickel material, indium material, or other metal materials that are easily soluble in acid. The double sacrificial layer process is used to prepare the microneedle 2, which can simplify the process flow and improve the preparation yield. The deposition process of the second sacrificial layer 7 can be PVD, CVD, or evaporation. Then, the flexible layer 8 is spin-coated on the second sacrificial layer 7. The flexible layer 8 serves as the substrate layer of the soft needle 201. The flexible layer 8 can be made of polyimide material, PDMS material, silicone material, polyparaxylene material, or other flexible polymer materials with good biocompatibility.

[0053] S3: preparing a lead layer 9, an insulating layer 10 and an electrode layer 11 in sequence on the flexible layer 8, and obtaining a plurality of soft needles 201 and a plurality of neural electrodes 202 on the soft needles 201 through photolithography and patterning.

[0054] In this embodiment, the lead layer 9 is prepared on the flexible layer 8 by photolithography and patterning process. The lead layer 9 can be made of gold material or silver material or other metal materials with good biocompatibility. Then, the insulating layer 10 is spin-coated on the lead layer 9 and the insulating layer 10 is patterned. The insulating layer 10 can be made of polyimide material or PDMS material or silicone material or polyparaxylene material or other flexible polymer high molecular materials with good biocompatibility. The insulating layer 10 is patterned by photolithography or etching process. Then, the electrode layer 11 is deposited on the insulating layer 10, and the electrode layer 11 is photolithographically and patterned to obtain a plurality of the soft needles 201 and a plurality of the neural electrodes 202 on the soft needles 201. The electrode layer 11 can be made of gold material or silver material or other metal materials with good biocompatibility. The deposition process of the electrode layer 11 can be PVD or CVD or evaporation. The electrode layer 11 is patterned by stripping or etching process.

[0055] S4: removing the first sacrificial layer 5 and the second sacrificial layer 7 , and preparing a connecting column 204 between the hard needle 203 and the soft needle 201 .

[0056] In this embodiment, the first sacrificial layer 5 and the second sacrificial layer 7 are removed by a wet etching process, so that the substrate 4 is separated from the microneedle 2, and the hard needle 203 and the soft needle 201 are spaced apart. The connecting column 204 is prepared at a preset position of the lead layer 9 by a spot welding process. The connecting column 204 can be made of platinum tungsten alloy or other electrochemically dissolved materials.

[0057] Further, see Figure 1 and Figure 4As shown, in some embodiments, before preparing the connecting column 204 between the hard needle 203 and the soft needle 201, the method further includes:

[0058] S401 : etching the flexible layer 8 and the second sacrificial layer 7 at a preset position of the lead layer 9 to form a through hole penetrating the flexible layer 8 and the second sacrificial layer 7 .

[0059] In this embodiment, the flexible layer 8 and the second sacrificial layer 7 are etched at the preset position of the lead layer 9 by photolithography and etching processes, so that the soft needle 201 forms the through hole at the preset position, and reserves space for preparing the connecting column 204.

[0060] See also Figure 1 As shown, the embodiment of the present application provides a method for using a composite microneedle structure, which includes the following steps:

[0061] The first step: implant the microneedle 2 into the patient's brain tissue and apply a safe voltage to the multiple hard needles 203.

[0062] Step 2: After the connecting column 204 is dissolved, the multiple hard needles 203 are withdrawn and the multiple soft needles 201 are retained.

[0063] In this embodiment, the hard needle 203 is used to bring the soft needle 201 into the patient's brain tissue, and then a safety voltage is applied to the multiple hard needles 203, and the connecting column 204 dissolves quickly. The safety voltage can be set to 0.7-1V, and the connecting column 204 can dissolve in 5-10 seconds. After the connecting column 204 dissolves and disconnects, the multiple hard needles 203 and the multiple soft needles 201 can be separated, and the multiple hard needles 203 are withdrawn and the multiple soft needles 201 are retained, so that the multiple soft needles 201 are implanted in the patient's brain tissue, which is convenient for postoperative imaging examination. The hard needle 203 can be made of metal materials with good biocompatibility such as gold material, silver material, platinum material, or tungsten material. Preferably, the hard needle 203 is made of silver material. Compared with the traditional hard needle which is made of silicon-based material, the hard needle 203 is not easy to break, thus avoiding brittle fracture of the hard needle 203 during implantation or removal, and improving the implantation efficiency of the soft needle 201. The soft needle 201 can be made of polyimide material, PDMS material, silicone material, polyparaxylene material, or other flexible polymer materials with good biocompatibility. The connecting column 204 can be made of platinum-tungsten alloy or other electrochemically dissolved materials. Platinum-tungsten alloy has good biocompatibility, and the reactants generated by the electrochemical reaction are harmless. The reactants can be metabolized and excreted from the human body, and the products of the dissolved reactants are also harmless.

[0064] In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0065] It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0066] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A composite microneedle structure, characterized in that: It includes: Circuit board (1); A microneedle (2), the microneedle (2) comprising a plurality of soft needles (201), the plurality of soft needles (201) being fixed to the circuit board (1), each of the soft needles (201) being provided with a plurality of nerve electrodes (202), the plurality of nerve electrodes (202) being electrically connected to the circuit board (1); The microneedle (2) further comprises a plurality of hard needles (203), each of the hard needles (203) being fixed to the corresponding soft needle (201) via a connecting column (204), and the connecting column (204) is made of an electrochemically dissolving material.

2. The composite microneedle structure according to claim 1, characterized in that: Each of the soft needles (201) is provided with protruding structures (205) on both sides.

3. The composite microneedle structure according to claim 2, characterized in that: The outer side of the protruding structure (205) is provided with a chamfer.

4. The composite microneedle structure according to claim 1, characterized in that: The circuit board (1) is provided with a first welding position (101) and a second welding position (102); the first welding position (101) is electrically connected to the second welding position (102); a plurality of soft needles (201) are fixedly arranged at the first welding position (101); and a microstrip line (3) is fixedly arranged at the second welding position (102).

5. The composite microneedle structure according to claim 1, characterized in that: Each of the soft needles (201) is provided with a through hole, and the connecting column (204) passes through the through hole to connect the soft needle (201) and the hard needle (203).

6. The composite microneedle structure according to claim 1, characterized in that: The height of the connecting column (204) is set to be 20-100 μm.

7. The composite microneedle structure according to claim 1, characterized in that: The hard needle (203) is made of metal material, and the soft needle (201) is made of flexible polymer material.

8. A method for preparing the composite microneedle structure as claimed in claim 1, characterized in that: It includes the following steps: Depositing a first sacrificial layer (5) on a substrate (4), depositing a metal layer (6) on the first sacrificial layer (5), and obtaining a plurality of hard needles (203) through photolithography and patterning; Depositing a second sacrificial layer (7) on the hard needle (203), and preparing a flexible layer (8) on the second sacrificial layer (7); A lead layer (9), an insulating layer (10) and an electrode layer (11) are sequentially prepared on the flexible layer (8), and a plurality of soft needles (201) and a plurality of neural electrodes (202) on the soft needles (201) are obtained through photolithography and patterning. The first sacrificial layer (5) and the second sacrificial layer (7) are removed, and a connecting column (204) is prepared between the hard needle (203) and the soft needle (201).

9. The preparation method according to claim 8, characterized in that: Before preparing the connecting column (204) between the hard needle (203) and the soft needle (201), the method further includes: The flexible layer (8) and the second sacrificial layer (7) are etched at a preset position of the lead layer (9) to form a through hole penetrating the flexible layer (8) and the second sacrificial layer (7).

10. A method for using the composite microneedle structure as claimed in claim 1, characterized in that: It includes the following steps: Implanting the microneedles (2) into the patient's brain tissue and applying a safe voltage to the plurality of hard needles (203); After the connecting column (204) is dissolved, the multiple hard needles (203) are withdrawn and the multiple soft needles (201) are retained.

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