Electrode contact processing method and implantable electrode

Abstract

The present application provides a processing method for electrode contacts and an implantable electrode. The processing method for electrode contacts includes performing line scanning on the surface of a contact substrate by laser direct writing technology to process a hierarchical structure and form an electrode contact with a hierarchical structure. The hierarchical structure includes grooves and micro-nano particles attached to the grooves. The laser is a laser with a pulse width of less than 10 picoseconds, the scanning line spacing of the laser is Δx, and the ablation width of a single line scan of the laser is W, satisfying Δx≤0.5×W. In addition to the above-mentioned electrode contacts, the implantable electrode provided in the present application also includes: a wire; a sleeve or coating, the sleeve or coating is arranged on the outside of the wire; and a sealing part, which is arranged at a position other than the hierarchical structure of the electrode contact. The present application ablates the electrode contacts by laser direct writing technology to process electrode contacts with grooves and micro-nano particles, and its charge injection capability is improved, the impedance amplitude is reduced, and it has an excellent wicking effect, thereby improving the electrochemical performance.

Description

Technical Field

[0001] The present application relates to the field of implantable medical devices, and in particular to a method for processing electrode contacts of an implantable electrode with a hierarchical structure and an implantable electrode. Background Art

[0002] Implantable electrodes for neural stimulation and / or recording are important components of neuromodulation devices and brain-computer interfaces, which are rapidly developing and applied to disease treatment and physical rehabilitation. In order to ensure the safety and stability of implantable electrodes, their electrode interface must allow sufficient charge injection while avoiding irreversible reduction and oxidation reactions.

[0003] Platinum or platinum-iridium alloy (Pt-Ir) is widely used in neural stimulation electrodes for active implantable medical devices, such as deep brain stimulators, cochlear implants, and spinal cord stimulators, due to its excellent biocompatibility and corrosion resistance. However, their low charge injection capability limits further applications and cannot meet the growing demand for smaller geometry electrodes and complex stimulation strategies. In addition, electrodes with small geometry are usually accompanied by high impedance amplitude, which affects not only the stimulation efficiency but also the recording quality.

[0004] In order to optimize the electrode interface properties, the existing technologies can be mainly divided into two categories: adding coatings and surface modification.

[0005] Adding coatings is done by adding coating materials such as iridium oxide, platinum black, and conductive polymers to the electrode substrate by sputtering, electrodeposition, chemical action, etc. They can greatly increase the charge injection capacity of the electrode by 1-2 orders of magnitude. However, the coating materials may not be firmly attached to the electrode substrate, and there may be biocompatibility challenges. In addition, most manufacturing methods for increasing the surface area of ​​the electrode involve complex manufacturing processes and uncommon materials, such as graphene, which are costly.

[0006] Surface modification provides another method, including plasma etching, electrochemical roughening processing and ultrafast laser direct writing. Plasma etching can achieve controllability of pore size and depth and has improved electrochemical performance, but requires precise masks to cover areas that do not need to be treated. Electrochemical roughening can obtain increased surface area, but it is difficult to maintain a stable process and requires the use of some harmful chemical reagents.

[0007] Ultrafast laser direct writing is a simple and fast method that produces a variety of micro / nano structures through processes such as re-solidification after ablation and redeposition of micro / nano particles. US9117680B2 proposes to use ultrafast lasers with high pulse energy to form micro / nano protrusion structures of multiple scales on the electrode surface to increase the specific surface area. However, this technology does not optimize the combined regulation of multiple processing parameters involved in the laser direct writing process and the surface structure formed, and cannot achieve the wicking of the main components of biological tissues (such as water). There is still a lot of room for improvement in charge injection capability and impedance amplitude. Summary of the invention

[0008] In order to improve or solve at least one problem raised by the background art, the present application provides a method for processing electrode contacts of an implantable electrode with a hierarchical structure and an implantable electrode.

[0009] The processing method of the electrode contact includes performing line scanning on the surface of the contact substrate by laser direct writing technology to process a hierarchical structure to form the electrode contact having the hierarchical structure, wherein the hierarchical structure includes grooves and micro-nano particles attached to the grooves, the laser is a laser with a pulse width of less than 10 picoseconds, the scanning line spacing of the laser is Δx, and the ablation width of a single line scan of the laser is W, satisfying Δx≤0.5×W.

[0010] In at least one embodiment, the relationship between Δx and W satisfies: 0.05×W≤Δx≤0.15×W.

[0011] In at least one embodiment, the number of irradiated pulses within a single spot of the laser is N, the single pulse energy of the laser is E, and the value of N is inversely proportional to the value of E.

[0012] In at least one embodiment, the contact substrate is processed into a tube shape or a sheet shape.

[0013] In at least one embodiment, when the contact base is processed into a tubular shape, the scanning line of the laser is processed into at least one of a spiral line, parallel lines extending along the circumference of the electrode contact and spaced apart in the axial direction of the electrode contact, and parallel lines extending along the axial direction and spaced apart in the circumferential direction.

[0014] In at least one embodiment, when the contact substrate is processed into a sheet shape, the scanning lines of the laser are arranged to be parallel straight lines or parallel bending lines.

[0015] In at least one embodiment, both sheet-shaped surfaces of the contact base body are processed with the layered structure.

[0016] In at least one embodiment, the width of the groove is a and satisfies 0.1 μm≤a≤1000 μm, and the particle size of the micro-nano particles is r and satisfies 10 nm≤r≤1000 nm.

[0017] In at least one embodiment, an angle between an optical axis of the laser and a surface of the contact substrate is greater than 0° and less than 90°.

[0018] The implantable electrode provided in the present application includes an electrode contact obtained by processing using the above processing method, and the implantable electrode also includes:

[0019] A wire connected to the electrode contact;

[0020] a sleeve or coating disposed on the outside of the wire; and

[0021] A sealing portion is provided at a location other than the hierarchical structure of the electrode contact.

[0022] The present application uses laser direct writing technology to scan lines to ablate the contact substrate to process electrode contacts with grooves and micro-nano particles. By controlling the line scanning repetition rate, the adhesion effect of the micro-nano particles is improved, the charge injection capability is improved, the impedance amplitude is reduced, and it has an excellent wicking effect, thereby improving the electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic structural diagram of an implantable electrode with a hierarchical structure according to an embodiment of the present application is shown.

[0024] Figure 2A , Figure 2B , Figure 2C , Figure 2D and Figure 2E A schematic structural diagram of an electrode contact according to an embodiment of the present application is shown.

[0025] Figure 3A , Figure 3B and Figure 3C A schematic structural diagram of the hierarchical structure of the electrode contact surface under different line scanning repetition rates according to an embodiment of the present application is shown.

[0026] Description of Reference Numerals

[0027] 1 electrode contact;

[0028] 2 wires;

[0029] 3 Casing;

[0030] 4. Sealing part;

[0031] 5 hierarchical structure; 51 grooves; 52 micro-nanoparticles DETAILED DESCRIPTION

[0032] The exemplary embodiments of the present application are described below with reference to the accompanying drawings. It should be understood that these specific descriptions are only used to teach those skilled in the art how to implement the present application, and are not intended to exhaust all possible methods of the present application, nor to limit the scope of the present application.

[0033] The present application provides an implantable electrode with a hierarchical structure, which can be suitable for a cardiac pacemaker, a defibrillator, a deep brain stimulator, a spinal cord stimulator, a vagus nerve stimulator, a gastrointestinal stimulator or other similar implantable medical devices.

[0034] See also Figure 1 The implantable electrode comprises an electrode contact 1, a wire 2, a sleeve 3 and a sealing part 4. The wire 2 is connected to the electrode contact 1, the sleeve 3 can be arranged outside the wire 2, and the sealing part 4 can be arranged at the left and right ends of the electrode contact 1. Figure 1 The sealing portion 4 at the left end can be used to prevent the human body from contacting the portion of the electrode contact 1 that does not have the hierarchical structure 5 (described later), and the sealing portion 4 at the right end can play the role of isolating the electrode contact 1 from the sleeve 3. That is, the sealing portion 4 can be provided at a portion other than the hierarchical structure 5 of the electrode contact 1. Of course, a coating (not shown in the figure) can also be provided on the outer surface of the wire 2 to replace the sleeve 3. That is, the electrode contact 1 can be insulated at a location other than the interface where it contacts the human body (subject) tissue to prevent unnecessary contact.

[0035] Exemplarily, the material of the sleeve 3 may be silicone rubber, polyimide, Pylaron, fluorine-containing plastic, etc. The material of the sealing portion 4 may be polyurethane, polyimide, Pylaron, fluorine-containing plastic, etc.

[0036] For example, see Figure 2A , Figure 2B , Figure 2C , Figure 2D and 2E The contact substrate of the electrode contact 1 may be in the form of a tube, a sheet, etc. The material of the contact substrate may be an implantable conductive material, such as platinum, platinum-iridium, stainless steel, MP35N (non-magnetic nickel-cobalt-chromium-molybdenum alloy), nickel, titanium, etc.

[0037] The electrode contact 1 has a layered structure 5 on its surface. Figure 3C The hierarchical structure 5 includes parallel grooves 51 and micro-nanoparticles 52 attached to the grooves 51 .

[0038] See also Figure 3A , Figure 3B and Figure 3C, the geometric dimensions of the groove 51 can be defined by the groove width a and the groove angle b. The groove width a is the width of the top opening of the groove 51, and the groove angle b is defined as the angle between the side wall of the groove and the horizontal plane. The groove width a can be set to 0.1μm≤a≤1000μm, and the groove angle b can be set to 0°<b<90°. The micro-nano particles 52 are attached to the groove 51, and the particle size r of the micro-nano particles 52 is in the range of 10nm≤r≤1000nm. The hierarchical structure 5 can greatly increase the actual surface area of ​​the electrode, so that the surface of the electrode contact 1 has a wicking effect, that is, it realizes rapid absorption of liquid (for example, water) under the action of surface tension, which is beneficial to the full infiltration of the electrode contact 1 and improves the electrochemical performance.

[0039] The hierarchical structure 5 can be prepared by scanning the surface of the contact substrate with an ultrafast laser. The so-called ultrafast laser is a laser with a pulse width of less than 10 ps. There are four basic parameters involved in laser processing: scanning speed v, repetition frequency f, scanning line spacing Δx and single pulse energy E.

[0040] The scanning speed v and the repetition frequency f jointly determine the number of irradiated pulses N within a single spot.

[0041]

[0042] Where ω0 is the radius of the Gaussian beam (laser).

[0043] The single pulse energy E affects the ablation width W of a single line scan. Figure 3A , the ablation width W is the width of the opening ablated by the laser on the material.

[0044]

[0045] Among them, E th is the ablation threshold.

[0046] In the present application, the scanning lines of the laser are parallel or spiral, the spacing between the scanning lines is Δx, or the pitch of the spiral line (the pitch is also called the scanning pitch) is Δx. According to the ablation width W and the designed scanning pitch Δx, the line scanning overlap rate can be obtained:

[0047]

[0048] Line scan overlap It can be understood as the overlap ratio of the grooves formed by two scanning line scans.

[0049] That is, by adjusting N, E and The hierarchical structure formed by ultrafast laser direct writing can be controlled. The value range of N is 100≤N≤100,000, and the value range of E is 1≤E≤500μJ.

[0050] This application has designed a reasonable The value range of The preferred value range is: That is, the laser scanning line spacing Δx is not greater than half of the laser single line scanning ablation width W. Using a line scanning overlap rate of more than 50% is more conducive to the deposition of micro-nano particles 52 and stable attachment to the grooves 51 to form a hierarchical structure 5.

[0051] Furthermore, the most reasonable The value range can be set in That is, 0.05×W≤Δx≤0.15×W, so as to increase the number of micro-nano particles 52 deposited per unit area and avoid clogging of the porous structure due to excessive deposition. If the overlap rate exceeds 95%, the sidewall of the groove 51 is too low, which is not conducive to the deposition of micro-nano particles 52.

[0052] See also Figure 3A When the ultrafast laser performs linear scanning on the metal surface, a conical microgroove 51 is formed, whose width is the ablation width W. When continuous parallel line scanning is performed, when the line scanning track has no overlap and the scanning interval Δx ≥ W, the scanning overlap rate is Forming a non-overlapping microgroove structure. It can be understood that There is no point. The minimum value of is 0, indicating that the grooves formed by two parallel line scans do not overlap. There are still very small amounts of micro-nano particles 52 deposited in the formed microgrooves 51 .

[0053] See also Figure 3B , the line scanning interval Δx decreases, that is, the scanning overlap rate The microgrooves 51 overlap, and the micro-nanoparticles 52 generated by subsequent scanning will be deposited into the already formed microgrooves. Only a small amount of micro-nano particles 52 are deposited in the formed microgrooves 51 .

[0054] See also Figure 3C , the line scan spacing Δx is further reduced to Δx less than W / 2, that is, the scan overlap rate At this time, the center of the line scanning laser beam falls on the inclined side wall of the microgroove formed by the previous line scanning, which helps more micro-nano particles 52 to be sprayed obliquely and deposited into the formed microgroove 51, and stably adhere to the surface of the microgroove 51 to form a rich hierarchical structure 5.

[0055] See also Figure 3B and Figure 3C , it can be clearly seen that when When the groove sidewall height of the groove 51 is low, the deposition density of the micro-nano particles 52 is relatively high, and the micro-nano particles 52 are more easily adhered to the micro-nano particles 52, thereby reducing the shedding rate of the micro-nano particles 52 from the groove 51, and can reduce the biocompatibility problems caused by the shedding of the micro-nano particles 52 into human tissues.

[0056] when When the laser beam is irradiated more on the unprocessed smooth surface, The actual surface area of ​​the processed surface is larger than that of the unprocessed smooth surface. The larger actual surface area helps to absorb more laser energy, thus making the When the temperature is high, more micro-nano particles can be precipitated in the grooves.

[0057] This application Figure 3A , Figure 3B , Figure 3C The embodiment in which the optical axis of the laser is perpendicular to the surface of the contact substrate is shown. Further, the optical axis of the laser can also have an angle greater than 0° and less than 90° with the surface of the contact substrate (for example Figure 2C ), so that ablation is more conducive to the deposition of micro-nano particles. It can be understood that when the contact substrate is tubular, its cylindrical surface can be regarded as a plane under microscopic conditions.

[0058] The present application also proposes that a reasonable selection of a combination of E and N can significantly improve the electrochemical performance of the electrode. A combination with high values ​​of both E and N may lead to excessive deposition of micro-nanoparticles, blocking the formed hierarchical structure 5. The present application found that a combination of high and low E and N is beneficial to optimizing electrode performance. For example, when E = 10 μJ, N = 1000 can be selected; or when E = 5 μJ, N = 5000 can be selected. The values ​​of E and N can be inversely proportional, so that the value of the product of E and N is not greater than 25,000, avoiding excessive deposition of micro-nanoparticles caused by high E and N.

[0059] The present application also provides a method for processing an implantable electrode.

[0060] See also Figure 2A For example, a femtosecond laser can be used to process a platinum-iridium alloy tube (contact substrate) with an outer diameter D of 1.27 mm and a wall thickness of 100 μm to form the electrode contact 1. The laser has a pulse width of 300 fs, a central wavelength of 1030 nm, a repetition frequency upper limit of 600 kHz, and a rated output power of 10 W.

[0061] Of course, the present application does not limit the model of the femtosecond laser, the parameters of the material to be processed of the electrode contact 1 and the specific working parameters of the femtosecond laser.

[0062] When the platinum-iridium alloy tube is subjected to surface treatment, the platinum-iridium alloy tube can be clamped by a three-jaw chuck of a machine tool motion system, and line scanning ablation is performed along the circumference of the electrode contact 1 by controlling the translation axis X and the rotation direction A. A suitable set of laser pulse energy E, repetition frequency f and scanning speed v are selected, and a circumferential scanning is performed on the platinum-iridium alloy tube to obtain a groove 51 on which abundant micro-nano particles 52 are embedded.

[0063] See also Figure 2A , Figure 2B , Figure 2C In the present application, the scanning line of the laser on the tubular electrode contact 1 can be a spiral line (such as Figure 2A ), parallel lines extending in the circumferential direction and spaced apart in the axial direction (such as Figure 2B ), parallel lines extending axially and spaced circumferentially (such as Figure 2C ); see Figure 2D and Figure 2E In the present application, the scanning lines of the laser on the sheet-shaped electrode contacts 1 can be parallel straight lines (such as Figure 2D ), parallel bending lines (such as Figure 2E ) etc. In one embodiment of the present application, both sides of the sheet-shaped electrode contact 1 have a layered structure 5 .

[0064] Depending on the selected overlap ratio of the laser line scans In one embodiment of the present application, E = 10 μJ, f = 100 kHz, v = 5 mm / s and Δx = 8 μm (at this time, ) as an example, ablation is performed on the electrode in parallel around the X axis. After completing the femtosecond laser direct writing, an ultrasonic cleaner is used to clean it in water for 30 seconds. A platinum-iridium tube with a length l of 1.5 mm can be cut as an electrode contact 1, a sleeve 3 is put on the outside of the metal conductor, and the two ends of the electrode contact 1 are insulated and sealed with a sealing part 4, thereby completing the processing of an implantable electrode with a hierarchical structure.

[0065] In the experimental test of the present application, the surface of the electrode contact 1 exhibited a wicking effect on water. More specifically, about 0.3 μL of water was dripped onto the surface of the electrode contact 1; after 0.25 seconds, the water quickly wetted the surface of the electrode contact 1; after 3 seconds, the water droplet was significantly smaller due to being absorbed by the surface of the electrode contact 1. In the experimental test of the present application, through the electrochemical performance test, the charge storage capacity of the electrode contact 1 was increased to 28 times that of the electrode without a hierarchical structure, the electrochemical impedance amplitude was greatly reduced, and the interface capacitance was increased.

[0066] The present application forms a rich micro-nano hierarchical structure with stable attachment on the metal surface by setting a line scan overlap rate of more than 50% (more preferably not less than 85% and not more than 95%) and reasonably controlling the combination of pulse energy, scanning speed and repetition frequency. The stably attached hierarchical structure can avoid the biocompatibility problems caused by the shedding of micro-nano particles, which is the key performance of the electrode to meet clinical applications. At the same time, the charge injection capacity of the electrode is significantly improved, the impedance amplitude is reduced, and it has an excellent wicking effect.

[0067] The above is a preferred embodiment of the present application. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A method for processing an electrode contact, characterized in that: include: Line scanning is performed on the surface of the contact substrate by laser direct writing technology to process a hierarchical structure (5) to form the electrode contact (1) having the hierarchical structure (5), wherein the hierarchical structure (5) comprises a groove (51) and micro-nanoparticles (52) attached to the groove (51), the laser has a pulse width of less than 10 picoseconds, and the scanning line spacing of the laser is Δx , the ablation width of the laser single line scan is W， satisfy Δx ≤ 0.5× W , so that the center of the line scanning laser beam can fall on the inclined side wall of the groove (51) formed by the previous line scanning, so that the micro-nano particles (52) formed by ablating the contact substrate by the line scanning laser beam can be sprayed at an angle to increase adhesion stability, and the particle size of the micro-nano particles (52) is r, and satisfies 10 nm ≤ r ≤ 1000 nm.

2. The processing method according to claim 1, characterized in that: Said Δx With the W The relationship between satisfies, 0.05× W ≤ Δx ≤ 0.15× W .

3. The processing method according to claim 1 or 2, characterized in that: The number of irradiated pulses within a single spot of the laser is N , the single pulse energy of the laser is E , N With the E is inversely proportional to the value of .

4. The processing method according to claim 1 or 2, characterized in that: The contact base is processed into a tube shape or a sheet shape.

5. The processing method according to claim 4, characterized in that: When the contact substrate is processed into a tubular shape, the scanning line of the laser is processed into at least one of a spiral line, parallel lines extending along the circumference of the electrode contact (1) and spaced apart in the axial direction of the electrode contact (1), and parallel lines extending along the axial direction and spaced apart in the circumferential direction.

6. The processing method according to claim 4, characterized in that: When the contact substrate is processed into a sheet shape, the scanning lines of the laser are set to be parallel straight lines or parallel bending lines.

7. The processing method according to claim 6, characterized in that: The layered structure (5) is processed on both sheet-like sides of the contact base body.

8. The processing method according to claim 1 or 2, characterized in that: The width of the groove (51) is a, and satisfies 0.1 μm ≤ a ≤ 1000 μm.

9. The processing method according to claim 1, characterized in that: An angle between the optical axis of the laser and the surface of the contact substrate is greater than 0° and less than 90°.

10. An implantable electrode, comprising an electrode contact (1) processed by the processing method according to any one of claims 1 to 9, characterized in that: The implantable electrode further comprises: A wire (2), the wire (2) being connected to the electrode contact (1); a sleeve (3) or a coating, wherein the sleeve (3) or the coating is arranged on the outside of the wire (2); and A sealing portion (4), wherein the sealing portion (4) is provided at a location outside the hierarchical structure (5) of the electrode contact (1).

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