Flexible cortex electrode and preparation method thereof

Abstract

The invention discloses a flexible cortical electrode and a preparation method thereof, and relates to the technical field of brain-computer interfaces. The flexible cortex electrode provided by the invention comprises a flexible supporting layer, a metal lead layer and a flexible packaging layer which are arranged in a stacked manner, the metal lead layer is arranged between the flexible supporting layer and the flexible packaging layer; the metal lead layer comprises a plurality of conductive wires which are arranged at intervals; the flexible packaging layer covers the flexible supporting layer and the metal lead layer; wherein one side, facing the metal lead layer, of the flexible supporting layer and / or the flexible packaging layer is provided with a plurality of raised lines, at least part of the raised lines are embedded between the two adjacent conductive wires, and clamping of the metal lead layer is formed between the raised lines. By increasing the acting force between the flexible supporting layer and / or the flexible packaging layer and the metal lead layer, the problem that the metal lead layer is prone to falling off is solved, and the stability of the flexible cortex electrode is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of brain-computer interface, and particularly relates to a flexible cortex electrode and a preparation method thereof. BACKGROUND

[0002] The brain-computer interface is an important technology, which connects the brain and the computer or other external devices directly through a sensing terminal to realize the extraction and decoding of brain signals and finally convert them into instruction signals that can be used to control external devices. One of the main functions of the brain-computer interface is information extraction, that is, reading the information in the biological brain.

[0003] Currently, there are generally two information extraction methods, namely non-implanted and implanted information extraction methods. The non-implanted method is to read EEG (electroencephalogram) data through a head cap worn on the scalp; and the implanted method includes obtaining EEG data through a fully implanted microelectrode array, a microneedle electrode or a deep brain electrode, or a flexible cortex electrode. Among these technologies, the flexible cortex electrode is usually attached to the dura mater or the subdural cortex surface through minimally invasive surgery. The flexible cortex electrode can achieve good conformal attachment to the brain tissue due to its high signal resolution, relatively long stability and relatively low invasiveness, greatly reducing the inflammatory reaction of the brain tissue due to slight displacement, and thus has been widely used in the field of brain-computer interface.

[0004] Currently, the flexible cortex electrode generally includes a bottom flexible support layer and a top flexible packaging layer composed of a polymer material, and an intermediate metal lead layer formed of a metal material. Although the flexible cortex electrode can greatly alleviate the inflammatory reaction, it is prone to failure phenomena such as metal lead layer shedding in long-term implantation applications. The reasons for the failure phenomena are as follows: on the one hand, due to the water absorption characteristics of the polymer material of the flexible cortex electrode, the flexible cortex electrode is used in a physiological liquid environment for a long time, which causes the physiological liquid to penetrate between the layers and cause delamination, and the continuous neural electrical signals outside aggravate the penetration of the physiological liquid. On the other hand, the bonding force between the metal and the polymer material is weak, and under the continuous action of low-frequency neural signals, the metal lead layer is prone to oscillation and shedding. The above two cases will damage the original structure of the flexible cortex electrode, causing the loss of part of the function of the electrode and limiting the long-term implantable application of the flexible cortex electrode in the body.

[0005] Therefore, there is an urgent need to provide a flexible cortex electrode with better stability. SUMMARY

[0006] In view of the above, the present application provides a flexible cortex electrode and a preparation method thereof, which aims to improve the stability of the flexible cortex electrode.

[0007] The first aspect of the present application provides a flexible skin layer electrode, which comprises a flexible support layer, a metal lead layer and a flexible packaging layer arranged in layers. The metal lead layer is arranged between the flexible support layer and the flexible packaging layer; the metal lead layer comprises a plurality of spaced conductive wires. The flexible packaging layer covers the flexible support layer and the metal lead layer; wherein, The flexible support layer and / or the flexible packaging layer are provided with a plurality of protrusions on the side facing the metal lead layer, at least part of the protrusions are embedded between two adjacent conductive wires, and the protrusions form a clamping on the metal lead layer.

[0008] In some embodiments, the area of the flexible support layer covered by the metal lead layer is a first area; the area of the flexible support layer not covered by the metal lead layer is a second area. The flexible support layer is provided with a plurality of first fitting parts on the side facing the flexible packaging layer, the first fitting parts are arranged in the second area, the flexible packaging layer is provided with a plurality of second fitting parts matched with the first fitting parts, the flexible support layer and the flexible packaging layer are connected by the first fitting parts and the second fitting parts, the first fitting parts and / or the second fitting parts comprise the protrusions, and the protrusions form a clamping on the metal lead layer with the first fitting parts or the second fitting parts and the flexible support layer and the flexible packaging layer.

[0009] In some embodiments, one of the first fitting parts and the second fitting parts is a groove, and the other is a protrusion matched with the groove, and the protrusion comprises the protrusions.

[0010] In some embodiments, the number of the first fitting parts is a plurality, and a plurality of the first fitting parts are arranged in the second area.

[0011] In some embodiments, the first fitting part is a groove, and the second fitting part is a protrusion, one end of the groove close to the flexible packaging layer is an upper end of the groove, and the other end of the groove close to the flexible support layer is a lower end of the groove, and the horizontal cross section of the groove gradually increases in the direction from the lower end to the upper end.

[0012] In some embodiments, the vertical cross section of the groove is at least one of trapezoidal, circular arc, sawtooth and square.

[0013] In some embodiments, the depth of the groove ranges from 0.1 μm to 50 μm.

[0014] In some embodiments, the groove is a trapezoidal groove, and a side profile of the trapezoidal groove is linear or curved.

[0015] In some embodiments, an angle θ between a tangent line of any point on the side profile of the trapezoidal groove and a horizontal plane ranges from 0 to 90°.

[0016] In some embodiments, the curved profile includes an outwardly concave curved profile, an inwardly concave curved profile, or an S curved profile formed by alternating combination of outwardly concave curved profile and inwardly concave curved profile one or more times.

[0017] In some embodiments, the flexible encapsulation layer includes an encapsulation body layer and the bumps disposed on a side of the encapsulation body layer facing the flexible support layer, the bumps including protrusions embedded in the grooves and the protrusions and the encapsulation body layer being connected by the protrusions.

[0018] In some embodiments, the groove is a trapezoidal groove, an upper end of the trapezoidal groove has a width greater than a lower end of the trapezoidal groove, and the protrusion is a trapezoidal bump matching the trapezoidal groove; the protrusion, the protrusion and the encapsulation body layer are of an integral structure.

[0019] In some embodiments, two adjacent conductive wires include wire segments arranged in parallel and at intervals, and the protrusions are arranged between the two adjacent wire segments arranged in parallel and at intervals.

[0020] In some embodiments, the protrusions have a rectangular cross section.

[0021] In some embodiments, the protrusions have a rectangular cross section.

[0022] In some embodiments, the protrusions have a rectangular cross section. In some embodiments, the protrusions have a rectangular cross section.

[0023] The second aspect of the present application provides a preparation method of the flexible skin layer electrode, comprising the following steps: providing a flexible support layer and a metal lead layer arranged in layers; wherein, forming the flexible support layer on the surface of the substrate, and configuring the flexible support layer to be heated to 180-220°C for the first time, and the flexible support layer is not completely cured; depositing a metal material on the flexible support layer to form a metal lead layer; covering the flexible support layer and the metal lead layer with a flexible encapsulation layer to obtain the flexible skin layer electrode; wherein, The flexible support layer and the flexible encapsulation layer are configured to be subjected to a second stepwise temperature rise to 300-400°C, and the flexible support layer and the flexible encapsulation layer are both completely cured.

[0024] Advantages: In the present application, a plurality of protrusions are arranged on the side of the flexible support layer and / or the flexible encapsulation layer facing the metal lead layer, at least part of the protrusions are embedded between two adjacent conductive wires, and the protrusions form a clamping on the metal lead layer, so that the protrusions limit the conductive wires, which is beneficial to avoid the conductive wires from falling off. In addition, when the flexible skin layer electrode works in the body for a long time, the flexible encapsulation layer and the flexible encapsulation layer made of polymer material swell by absorbing water, which is beneficial to further increase the limiting effect of the protrusions on the conductive wires, further improve the problem of the conductive wires falling off, and improve the stability of the flexible skin layer electrode. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0026] Figure 1 Structure schematic diagram of the flexible skin layer electrode provided in some embodiments; Figure 2 Structure schematic diagram of the flexible skin layer electrode provided in some embodiments; Figure 1 Cross-sectional schematic diagram of A-A' plane in the present application; Figure 3 Cross-sectional schematic diagram of B-B' plane in the present application; Figure 1 Cross-sectional schematic diagram of B-B' plane in the present application; Figure 4 Structure schematic diagram of the interface between the flexible support layer and the flexible encapsulation layer in some embodiments; Figure 5 Structure schematic diagram of the interface between the flexible support layer and the flexible encapsulation layer in some embodiments; Figure 6 Structure schematic diagram of the interface between the flexible support layer and the flexible encapsulation layer in some embodiments; Figure 7 Structure schematic diagram of the interface between the flexible support layer and the flexible encapsulation layer in some embodiments; Figure 8 Preparation process flow chart of the flexible skin layer electrode in some embodiments; Figures 9-17 Product structure schematic diagram corresponding to different steps in the preparation process of the flexible skin layer electrode in some embodiments.

[0027] Reference signs: 100, flexible skin layer electrode; 10, flexible support layer; 11, first fitting part; 20, metal lead layer; 21, electrode contact; 22, electrode welding spot; 23, conductive wire; 24, contact area; 25, welding spot area; 30, flexible encapsulation layer; 31, encapsulation body layer; 32, second fitting part; 321, convex part; 322, convex strip; 40, electrode decoration layer; 50, hollow hole; 200, base. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not intended to limit the present application. The different components and technical features described in different embodiments herein can be freely combined with each other.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein only for the purpose of describing specific embodiments and is not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0030] In the present application, the orientation words such as "up" and "down" used without the opposite description generally refer to the up and down of the device in the actual use or working state, specifically the direction of the drawing surface in the drawings; and "inner" and "outer" are relative to the outline of the device. In addition, in the description of the present application, the term "includes" means "includes but is not limited to". The words first, second, third, etc. are only used as markers and do not impose numerical requirements or establish sequences.

[0031] In the present application, "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which can represent the following cases: A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural.

[0032] In the present application, "at least one" means one or more, and "multiple" means two or more. "One or more", "at least one of the following (one)", or the like, means any combination of these items, including any combination of single item (one) or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0033] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a hard limit on the scope of the present application; therefore, it should be considered that the described range has specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the described range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) within the indicated range.

[0034] In combination Figures 1-7 As shown, the present application provides a flexible skin layer electrode 100, which includes a flexible support layer 10, a metal lead layer 20, and a flexible packaging layer 30. The flexible skin layer electrode 100 improves the problem of easy falling off of the metal lead layer 20 and improves the stability of the flexible skin layer electrode 100 by increasing the force between the flexible support layer 10 and / or the flexible packaging layer 30 and the metal lead layer 20. It should be noted that the reference "X1 (X)" in the drawings means that the structural component represented by X1 is subordinate to the structural component represented by X. Figure 1 For example, in "23 (20)" in the drawings, the reference "23" represents a conductive wire, and the reference "20" represents a metal lead layer, and the conductive wire belongs to the metal lead.

[0035] In some embodiments, the flexible skin layer electrode 100 comprises a flexible support layer 10, a metal lead layer 20 and a flexible encapsulation layer 30 which are stacked; the metal lead layer 20 is arranged between the flexible support layer 10 and the flexible encapsulation layer 30; the metal lead layer 20 comprises a plurality of spaced apart conductive wires 23; the flexible encapsulation layer 30 covers the flexible support layer 10 and the metal lead layer 20; wherein one side of the flexible support layer 10 and / or the flexible encapsulation layer 30 towards the metal lead layer 20 is provided with a plurality of protrusions 322, at least part of the protrusions 322 are embedded between two adjacent conductive wires 23, and the protrusions 322 form a clamping on the metal lead layer 20.

[0036] It can be understood that, in the embodiments of the present application, by providing a plurality of protrusions 322 on one side of the flexible support layer 10 and / or the flexible encapsulation layer 30 towards the metal lead layer 20, and embedding at least part of the protrusions 322 between two adjacent conductive wires 23, the protrusions 322 can limit and clamp the corresponding conductive wires 23, which is conducive to avoiding the metal lead layer 20 from falling off. In addition, when the flexible skin layer electrode 100 works in the body for a long time, the flexible support layer 10 and the flexible encapsulation layer 30 made of polymer material absorb water and swell, which is conducive to further increasing the limiting effect of the protrusions 322 on the conductive wires 23, further improving the problem of the metal lead layer 20 falling off, and improving the stability of the flexible skin layer electrode 100.

[0037] In some embodiments of the present application, the flexible skin layer electrode 100 comprises a flexible support layer 10, a metal lead layer 20 and a flexible encapsulation layer 30 which are stacked; the area of the flexible support layer 10 covered by the metal lead layer 20 is a first area; the area of the flexible support layer 10 not covered by the metal lead layer 20 is a second area; the flexible encapsulation layer 30 covers the flexible support layer 10 and the metal lead layer 20; one side of the flexible support layer 10 towards the flexible encapsulation layer 30 is provided with a plurality of first fitting parts 11, the first fitting parts 11 are arranged in the second area, the flexible encapsulation layer 30 is provided with a plurality of second fitting parts 32 which are adapted to the first fitting parts 11, and the flexible support layer 10 and the flexible encapsulation layer 30 are connected by the first fitting parts 11 and the second fitting parts 32.

[0038] For example, the second fitting parts 32 are protrusions, and the second fitting parts 32 comprise the protrusions 322. In other embodiments of the present application, the first fitting parts 11 can also comprise the protrusions 322, which is not limited herein.

[0039] It can be understood that, in the present application, the first fitting part 11 is arranged on the flexible support layer 10, the flexible packaging layer 30 is provided with a second fitting part 32 matched with the first fitting part 11, and the flexible support layer 10 and the flexible packaging layer 30 are fitted through the first fitting part 11 and the second fitting part 32, so as to increase the connection area between the flexible support layer 10 and the flexible packaging layer 30, and further increase the bonding force between the flexible support layer 10 and the flexible packaging layer 30, which is beneficial to improve the stability of the flexible skin layer electrode 100.

[0040] In addition, the first fitting part 11 in the present application is arranged in the second area which is not covered by the metal lead layer 20, so as to avoid interference between the first fitting part 11 and the metal lead layer 20, and facilitate the simplification of the preparation process of the flexible skin layer electrode 100.

[0041] Meanwhile, when the flexible skin layer electrode 100 works in the body for a long time, the flexible packaging layer 30 made of polymer material and the flexible packaging layer 30 swell by absorbing water, the first fitting part 11 and the second fitting part 32 of the fitting connection between the flexible support layer 10 and the flexible packaging layer 30 are extruded, the interlayer friction between the two is improved, and the two are locked to each other and are not easy to delaminate, and the metal lead layer 20 is clamped, which is beneficial to further improve the stability of the flexible skin layer electrode 100, thereby prolonging the service life of the flexible skin layer electrode 100.

[0042] It should be noted that the number and specific structure of the first fitting part 11 and the number and specific structure of the second fitting part 32 are not limited, as long as the flexible support layer 10 and the flexible packaging layer 30 can be fitted and connected through the first fitting part 11 and the second fitting part 32.

[0043] Exemplarily, the number of the first fitting part 11 is multiple, and multiple first fitting parts 11 are arranged in the second area. In this way, it is beneficial to further increase the bonding force between the flexible support layer 10 and the flexible packaging layer 30, and improve the stability of the flexible skin layer electrode 100.

[0044] Optionally, in some embodiments, the main structure of the flexible skin layer electrode 100 includes the flexible support layer 10, the metal lead layer 20, the flexible packaging layer 30 and the electrode modification layer 40 arranged in layers from bottom to top; wherein the flexible support layer 10 at the bottom layer is used to support the metal lead layer 20 and plays the role of insulation and water vapor isolation; the metal lead layer 20 at the middle layer is used to contact with the tissue and transmit the nerve signal; the flexible packaging layer 30 at the top layer is used for insulation between the metal lead channels and water vapor isolation; the electrode modification layer 40 is connected with part of the metal lead layer 20, and is used to increase the biocompatibility, electrode injection capacity and signal-to-noise ratio of nerve signal acquisition.

[0045] In some embodiments, the flexible support layer 10 is selected from one or more of the following polymer materials: PI, Parylene-C, SU-8, or PDMS, etc. The thickness of the flexible support layer 10 ranges from 5 μm to 1000 μm. For example, the thickness of the flexible support layer 10 ranges from 5 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, and any range between any two of the above values.

[0046] In some embodiments, the metal lead layer 20 is disposed on the flexible support layer 10. The metal lead layer 20 includes an electrode contact area 24, an electrode pad area 25, and a multi-channel connection wire area. For example, the electrode contact area 24 includes one or more electrode contacts 21, the electrode pad area 25 includes one or more electrode pads 22, and the multi-channel connection wire area includes a plurality of spaced apart conductive wires 23, each of the electrode contacts 21 and the corresponding electrode pads 22 being electrically connected by one of the conductive wires 23.

[0047] Optionally, the shape of the electrode contacts 21 can be circular, rectangular, or other geometric shapes, which are not limited herein.

[0048] Optionally, the shape of the electrode pads 22 can be circular, rectangular, or other geometric shapes, which are not limited herein.

[0049] In some embodiments, the multi-channel connection wire area is formed by a plurality of non-intersecting metal leads, each of the metal leads (i.e., the conductive wires 23) having two ends respectively connected to one of the electrode contacts 21 and one of the electrode pads 22 to form a conductive path.

[0050] In some embodiments, the metal lead layer 20 is made of one or more of the following materials: titanium, chromium, gold, platinum, and silicon carbide, so as to have the function of electrical conduction and good adhesion with the flexible support layer 10. Preferably, the thickness of the metal lead layer 20 ranges from 0.05 μm to 10 μm, for example, the thickness of the metal lead layer 20 ranges from 0.05 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, and any range between any two of the above values. In this way, the metal lead layer 20 can stably transmit neural signals.

[0051] In some embodiments, the flexible encapsulation layer 30 is selected from one or more of the following polymer materials: PI, Parylene-C, SU-8, or PDMS, etc.

[0052] In some embodiments, the thickness of the flexible encapsulation layer 30 ranges from 5 μm to 1000 μm. Exemplarily, the thickness of the flexible encapsulation layer 30 ranges from 5 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, and a range value between any two of the above-mentioned values.

[0053] In some embodiments, the electrode modification layer 40 covers the exposed surface of the electrode contact 21 of the flexible encapsulation layer 30 and a region extending outwardly from the edge of the exposed surface by 5 μm to 50 μm. The electrode modification layer 40 is selected from one or more of gold, platinum, iridium, iridium oxide, titanium nitride, poly(3,4-ethylenedioxythiophene) (PEDOT), and carbon nanotube (CNT) materials. In this way, the stability of the flexible skin layer electrode 100 is improved, and the signal-to-noise ratio of the collected neural signals and the biocompatibility of the electrode are improved.

[0054] Optionally, in some embodiments, one of the first fitting part 11 and the second fitting part 32 is a groove, and the other of the first fitting part 11 and the second fitting part 32 is a protrusion that is adapted to the groove. Exemplarily, the first fitting part 11 is a groove, and the second fitting part 32 is a protrusion. Of course, in other embodiments of the present application, the first fitting part 11 can be a protrusion, and the second fitting part 32 can be a groove. Of course, the first fitting part 11 and the second fitting part 32 can also be other structures, which are not limited herein. For ease of understanding, the first fitting part 11 is taken as a groove, and the second fitting part 32 is taken as a protrusion for further elaboration.

[0055] Optionally, the first fitting part 11 is a groove, which can also be understood as that the upper surface of the flexible support layer 10 is provided with at least one groove. Exemplarily, the upper surface of the flexible support layer 10 is provided with a plurality of grooves. Correspondingly, the second fitting part 32 is a protrusion that is similar in shape to the groove, which can also be understood as that the lower surface of the flexible encapsulation layer 30 is provided with at least one protrusion. Here, the shape of the protrusion is adapted to the shape of the groove, which means that the shape of the protrusion is complementary to the shape of the groove, and can also be understood as that the protrusion can be filled in or embedded in the groove.

[0056] In some embodiments, the first fitting part 11 is a groove, the second fitting part 32 is a protrusion, the upper end of the groove is close to one end of the flexible packaging layer 30, the lower end of the groove is close to one end of the flexible support layer 10, and the horizontal cross section of the groove gradually increases in the direction from the lower end to the upper end. In this way, it is beneficial to simplify the process step of preparing the groove on the flexible support layer 10, and to improve the production efficiency and product stability.

[0057] In some embodiments, the vertical cross section of the groove is at least one of trapezoidal, circular arc, zigzag, square, special-shaped, etc. For example, the vertical cross section of the groove is trapezoidal. It can also be understood that the cross section of the groove is trapezoidal or similar to trapezoidal, or the profile of the groove in the vertical cross section (for example, the B-B' plane) is trapezoidal or generally trapezoidal, which can also be referred to as a trapezoidal groove. It should be noted that the vertical cross section of the groove can also be understood as a plane perpendicular to the multi-channel connecting wire, or a plane perpendicular to the length direction of the flexible skin electrode 100.

[0058] In some embodiments, the groove is in a structure of wide at the top and narrow at the bottom. Further, the groove is in a trapezoidal structure of wide at the top and narrow at the bottom. In this way, it is beneficial to simplify the process step of preparing the groove on the flexible support layer 10, and to improve the production efficiency and product stability.

[0059] In some embodiments, the trapezoidal groove is located on the surface of the flexible packaging layer 30 and avoids the area covered by the metal lead layer 20 on the flexible packaging layer 30. In this way, it is beneficial to further improve the bonding force between the flexible support layer 10 and the flexible packaging layer 30, and to simplify the preparation process.

[0060] In some embodiments, the depth of the trapezoidal groove ranges from 0.1 μm to 50 μm. For example, the depth of the trapezoidal groove is 0.1 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, and a range value between any two of the above values. In this way, it is beneficial to have a larger bonding force between the flexible support layer 10 and the flexible packaging layer 30, and to avoid the flatness of the substrate in the subsequent process step of the flexible packaging layer 30, which causes the flexible packaging layer 30 and the flexible support layer 10 surface groove not to be completely filled. It should be noted that the depth of the trapezoidal groove can also be selected according to the line width and line spacing of the metal lead layer 20, which is not limited here.

[0061] In some embodiments, the angle between the tangent line of any point on the side profile of the trapezoidal groove and the horizontal plane is θ, and θ ranges from 0 to 90°. Exemplarily, θ ranges from 1°, 5°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 85°, 89°, and any range between any two of the above values.

[0062] In some embodiments, referring to Figures 4-7 , the side profile of the trapezoidal groove can be linear or curvilinear, which is not limited herein. Further, the curvilinear profile can be an outwardly concave curve, an inwardly concave curve, or an S curve formed by alternating combination of outwardly concave curves and inwardly concave curves one or more times. It should be noted that if the side profile of the trapezoidal groove is curvilinear, the curvilinear side can provide more contact area between the two at the same etching aspect ratio, which is conducive to further improving the bonding force between the flexible support layer 10 and the flexible encapsulation layer 30.

[0063] In some embodiments, the flexible encapsulation layer 30 covers the flexible support layer 10 and the metal lead layer 20, and forms an exposed surface at the electrode contact 21. In this way, the electrode contact 21 is facilitated to contact the tissue, and the signal stability is improved.

[0064] In some embodiments, the flexible encapsulation layer 30 covers the flexible support layer 10 and the metal lead layer 20, and forms an exposed surface at the electrode pad 22. In this way, the electrode pad 22 is facilitated to be electrically connected to the outside.

[0065] In some embodiments, the flexible encapsulation layer 30 covers the flexible support layer 10 and the metal lead layer 20, and forms exposed surfaces only at the electrode contact 21 and the electrode pad 22. In this way, the area covered by the flexible encapsulation layer 30 is increased, and the encapsulation effect of the flexible skin layer electrode 100 is improved.

[0066] In some embodiments, the upper surface of the flexible support layer 10 is provided with a plurality of trapezoidal grooves, and the lower surface of the flexible encapsulation layer 30 is provided with a plurality of trapezoidal protrusions, each of which is embedded in a corresponding trapezoidal groove. In this embodiment, the trapezoidal grooves on the upper surface of the flexible support layer 10 and the trapezoidal protrusions on the lower surface of the flexible encapsulation layer 30 are embedded in each other. Through this arrangement, firstly, the contact area between the flexible support layer 10 and the flexible encapsulation layer 30 is increased; secondly, when the flexible skin layer electrode 100 works in the body for a long time, the flexible support layer 10 and the flexible encapsulation layer 30 made of polymer material absorb water and swell. After the trapezoidal grooves and the trapezoidal protrusions embedded in each other and pressed against each other, the interlayer friction between the two is improved, forming a mutual locking structure so that delamination is less likely to occur, thereby improving the service life of the flexible skin layer electrode 100.

[0067] Exemplarily, the lower surface of the flexible encapsulation layer 30 is provided with a plurality of protrusions, the upper surface of the flexible support layer 10 is provided with a plurality of grooves, the plurality of protrusions and the plurality of grooves are one-to-one correspondingly arranged, and each protrusion is embedded in a corresponding groove. In this way, the connection area between the flexible support layer 10 and the flexible encapsulation layer 30 is further increased, and the bonding force between the flexible support layer 10 and the flexible encapsulation layer 30 is further increased. Further, the grooves are trapezoidal grooves, and correspondingly, the protrusions include trapezoidal protrusions which are adapted to the trapezoidal grooves. It can also be understood that the trapezoidal protrusions are complementary to the trapezoidal groove shape of the surface of the flexible support layer 10.

[0068] In some embodiments, the flexible encapsulation layer 30 includes an encapsulation body layer 31 and the protrusions (i.e., the second fitting part 32) arranged on the side of the encapsulation body layer 31 facing the flexible support layer 10. The protrusions include protruding parts 321 embedded in the grooves and protruding strips 322 connecting the protruding parts 321 and the encapsulation body layer 31. Further, the shape of the protruding parts is adapted to the grooves, and the encapsulation body layer 31, the protruding strips 322, and the protruding parts are an integral structure. The profile of the protrusion in the vertical cross-section (e.g., the B-B' plane) is generally a combination shape of the trapezoidal protrusion (i.e., the protruding part 321) and the rectangular protrusion (i.e., the protruding strip 322); wherein the rectangular protrusion is arranged on the side of the trapezoidal protrusion away from the trapezoidal groove, one long side of the rectangular protrusion is connected to the lower surface of the flexible encapsulation layer 30, and the other long side of the rectangular protrusion is connected to the trapezoidal protrusion. It can be understood that the rectangular protrusion can strengthen the clamping of the metal lead layer 20, thereby improving the problem of easy falling off of the metal lead layer 20; and the trapezoidal protrusion is used to increase the contact area between the flexible support layer 10 and the flexible encapsulation layer 30, which is conducive to further increasing the bonding force between the flexible support layer 10 and the flexible encapsulation layer 30.

[0069] In some embodiments, at least part of the protruding strips 322 is arranged between two adjacent electrode contacts 21, and / or between two adjacent electrode pads 22, and / or between two adjacent conductive lines 23.

[0070] In some embodiments, the two adjacent conductive lines 23 include parallel and spaced conductive line segments, and the protruding strips 322 are arranged between the two parallel and spaced conductive line segments. In this way, the clamping of the metal lead layer 20 by the flexible encapsulation layer 30 is enhanced, and the preparation process of the flexible skin layer electrode 100 is simplified.

[0071] In some embodiments, the width of the protrusions 322 is equal to the distance between two adjacent conductive wires 23. Exemplarily, the protrusions 322 are rectangular protrusions, the length of the long side of the rectangular protrusions is equal to the distance between two adjacent conductive wires 23 in the metal lead layer 20, and the rectangular protrusions can also be understood as being embedded between two adjacent conductive wires 23. In this way, the two adjacent rectangular protrusions can clamp the metal lead wire located therebetween, which is conducive to further improving the stability of the flexible skin layer electrode 100. When the flexible skin layer electrode 100 works in the body for a long time, the rectangular protrusions swell due to water absorption, and the two adjacent rectangular protrusions can clamp the metal lead wire 23 located therebetween, which is conducive to preventing the metal lead layer 20 from falling off.

[0072] In some embodiments, the extension direction of the protrusions 322 is the same as the extension direction of the conductive wires 23. Exemplarily, the protrusions 322 are rectangular protrusions, and the extension direction of the rectangular protrusions is the same as the extension direction of the conductive wires 23. In this way, it is conducive to increasing the contact area between the rectangular protrusions and the conductive wires 23, and further preventing the metal lead layer 20 from falling off.

[0073] In some embodiments, the width of the protrusions 322 is equal to the distance between two adjacent conductive wires 23. Exemplarily, the protrusions 322 are rectangular protrusions, and the length of the short side of the rectangular protrusions is equal to the thickness of the metal lead wire in the metal lead layer 20. In this way, the two adjacent rectangular protrusions can clamp the metal lead wire located therebetween, and the interface between the flexible packaging layer 30 and the flexible support layer 10 is combined more tightly, which is conducive to improving the bonding force between the flexible packaging layer 30 and the flexible support layer 10.

[0074] Correspondingly, the side profile of the trapezoidal protrusion can be a straight line or a curve, which is not limited here. Further, the curve can be an outward concave curve, an inward concave curve, or an S curve formed by alternating combination of the outward concave curve and the inward concave curve one or more times. It should be noted that if the side profile of the trapezoidal protrusion is a curve, the angle θ between the tangent line at any point on the side profile of the trapezoidal protrusion and the plane on which the flexible support layer 10 is located is in the range of 0°-90°. It should be noted that under the same etching aspect ratio, the S-shaped curve side is conducive to further improving the bonding force between the flexible support layer 10 and the flexible packaging layer 30.

[0075] In some embodiments, the application provides a preparation method of the flexible skin layer electrode with the above structure, which is shown in Figures 8-17 The preparation method comprises the following steps: providing a flexible support layer 10 and a metal lead layer 20 arranged in layers; wherein, The flexible support layer 10 is formed on the surface of the substrate, and the flexible support layer 10 is subjected to first stepwise heating to 180-220°C and is not completely cured; A metal lead layer 20 is formed by depositing a metal material on the flexible support layer 10; A flexible encapsulation layer 30 is arranged on the flexible support layer 10 and the metal lead layer 20 to obtain the flexible skin layer electrode; wherein, The flexible support layer 10 and the flexible encapsulation layer 30 are subjected to second stepwise heating to 300-400°C, and the flexible support layer 10 and the flexible encapsulation layer 30 are completely cured.

[0076] It is particularly emphasized that, by not completely curing the flexible support layer 10 during the preparation of the flexible skin layer electrode 100, then covering the flexible encapsulation layer 30 on the not completely cured flexible support layer 10 and the metal lead layer 20, and by subjecting the flexible support layer 10 and the flexible encapsulation layer 30 to second stepwise heating to 300-400°C, the flexible support layer 10 and the flexible encapsulation layer 30 are completely cured, so that the flexible support layer 10 and the flexible encapsulation layer 30 can cross-link at the interface, which is beneficial to improve the bonding force between the flexible support layer 10 and the flexible encapsulation layer 30, and can also better form clamping on the metal lead layer 20, thereby improving the stability of the flexible skin layer electrode.

[0077] In some embodiments, the present application provides a preparation method for preparing the aforementioned structure flexible skin layer electrode, please refer to Figures 8-17 The preparation method comprises the following steps: S10 provides a flexible support layer 10 and a metal lead layer 20 arranged in layers; a metal lead layer 20 is formed by depositing a metal material on the flexible support layer 10; Wherein, the area of the flexible support layer 10 covered by the metal lead layer 20 is a first area; the area of the flexible support layer 10 not covered by the metal lead layer 20 is a second area; the flexible support layer 10 is provided with a first fitting part 11 in the second area.

[0078] S20 provides a flexible encapsulation layer 30 on the flexible support layer 10 and the metal lead layer 20 to obtain the flexible skin layer electrode 100; Wherein, the flexible encapsulation layer 30 is provided with a second fitting part 32 matched with the first fitting part 11, and the flexible support layer 10 and the flexible encapsulation layer 30 are connected by the first fitting part 11 and the second fitting part 32.

[0079] In the present application, the first fitting part 11 is arranged on the flexible support layer 10, the flexible packaging layer 30 is provided with the second fitting part 32 matched with the first fitting part 11, and the flexible support layer 10 and the flexible packaging layer 30 are fitted through the first fitting part 11 and the second fitting part 32, so as to increase the connecting area between the flexible support layer 10 and the flexible packaging layer 30, and further increase the binding force between the flexible support layer 10 and the flexible packaging layer 30, which can better form the clamping of the metal lead layer 20 and is beneficial to improve the stability of the flexible skin layer electrode 100. In addition, the first fitting part 11 in the present application is arranged in the second area which is not covered by the metal lead layer 20, so as to avoid the interference between the first fitting part 11 and the metal lead layer 20, and is beneficial to simplify the preparation process of the flexible skin layer electrode 100.

[0080] Meanwhile, when the flexible skin layer electrode 100 works in the body for a long time, the flexible support layer 10 and the flexible packaging layer 30 made of polymer material absorb water and swell, the flexible support layer 10 and the flexible packaging layer 30 are extruded after mutual extrusion, the interlayer friction force of the two is improved, mutual locking is formed so that delamination is not easy to occur, which is beneficial to further improve the stability of the flexible skin layer electrode 100, so as to improve the service life of the flexible skin layer electrode 100.

[0081] In some embodiments, the flexible support layer 10 and the metal lead layer 20 are provided in a stacked manner, and the step of depositing a metal material on the flexible support layer 10 to form the metal lead layer 20 includes: S11 provides a substrate 200.

[0082] Exemplarily, in combination with Figure 9 As shown, the substrate 200 is generally in a horizontal plate structure. For example, the material of the substrate 200 includes any one of silicon nitride, silicon, quartz glass. The size of the substrate 200 can be one of four inches, six inches or eight inches. The substrate 200 is cleaned by ultrasonic or heating immersion in a cleaning solution.

[0083] In some examples, the cleaning solution includes acetone, isopropyl alcohol, ethanol and deionized water.

[0084] In some examples, the cleaning solution includes a mixed solution of concentrated sulfuric acid and hydrogen peroxide, a hydrofluoric acid solution, a mixed solution of ammonia and hydrogen peroxide, and a mixed solution of concentrated hydrochloric acid and hydrogen peroxide.

[0085] S12 forms a flexible support layer 10 on the surface of the substrate 200.

[0086] In some examples, in combination with Figure 10As shown, the flexible support layer 10 is selected from one of PI (polyimide), Parylene-C, SU-8 or PDMS material, and has a thickness ranging from 5 μm to 1000 μm.

[0087] Exemplarily, the flexible support layer 10 is a polyimide layer, which can be formed by coating a polyimide precursor solution on the substrate 200, then removing the solvent, and heating to imidize the polyimide precursor solution. The coating method can be spin coating, spraying, blade coating or chemical vapor deposition.

[0088] Optionally, the flexible support layer 10 is a polyimide layer.

[0089] The steps of preparing the flexible support layer 10 include: The material of the flexible support layer 10 is PI, which is spin-coated on the surface of the substrate 200 at a speed of 500-5000 rpm, then first-stage heated to 180-220 °C to incompletely solidify the flexible support layer 10, i.e. to incompletely solidify the flexible support layer 10.

[0090] It is emphasized that the flexible support layer 10 is incompletely solidified at a lower temperature, which on the one hand does not dissolve and destroy the flexible support layer 10 in the subsequent process steps of acetone, N-methyl pyrrolidone (NMP) or photoresist developer, and on the other hand can maintain sufficient surface activity, so as to be more strongly connected with the subsequent flexible packaging layer 30.

[0091] It is particularly emphasized that the PI of the flexible support layer 10 is imidized and amorphous by first-stage heating to 180-220 °C when preparing the flexible support layer 10, so that the PI of the flexible support layer 10 retains more active functional groups.

[0092] Specifically, the substrate 200 is pre-baked at a temperature of 110-150°C, and after the substrate 200 is cooled to room temperature, a polyimide precursor solution is spin-coated, the viscosity of the polyimide precursor solution being 500-13000 mPa·s at 25°C. Then the spin-coated polyimide precursor solution is baked, the initial temperature of the oven being less than 100°C, which can be 80°C. After pre-baking for 10 min, the temperature is raised at a rate of 1°C / 2°C per minute, and when the temperature reaches 120-140°C (which can be a temperature within the range, including 120°C and 140°C), the temperature is maintained for 30 min; then the temperature is raised at a rate of 1°C / 2°C per minute, and when the temperature reaches 180-220°C (which can be a temperature within the range, including 180°C and 220°C), the temperature is maintained for 60 min; finally, the temperature is lowered at a rate of no more than 4°C per minute until it reaches room temperature. In this way, in the step of preparing the flexible support layer 10, the precursor solution for preparing the polyimide layer is allowed to undergo incomplete curing at a lower temperature.

[0093] S13 Depositing a metal material on the first region of the flexible support layer 10 to form a metal lead layer 20. In some embodiments, the metal lead layer 20 is prepared by a process comprising the following steps: Figures 1-3 and Figure 11 As shown in FIG. 1, the metal lead layer 20 comprises an electrode contact region 24, an electrode pad region 25, and a multi-channel connecting wire region. The electrode contact region 24 comprises a plurality of electrode contacts 21, which can be circular, rectangular, or other geometric shapes. Similarly, the electrode pad region 25 comprises a plurality of electrode pads 22, which can be circular, rectangular, or other geometric shapes. The multi-channel connecting wire region comprises a plurality of non-intersecting metal leads (i.e., conductive wires 23), each of which is connected at both ends to an electrode contact 21 and an electrode pad 22, forming a conductive path.

[0094] In some embodiments, the plurality of electrode contacts 21, the plurality of electrode pads 22, and the plurality of conductive wires 23 are integrally fabricated and formed simultaneously. Further, the plurality of electrode contacts 21, the plurality of electrode pads 22, and the plurality of conductive wires 23 are made of the same material, which can be one or more of titanium, chromium, silicon carbide, gold, or platinum. The thickness of the metal lead layer 20 prepared from each material is in the range of 5-500 nm.

[0095] In some embodiments, the metal lead layer 20 comprises one or more layers of composite metal thin film, and the metal lead layer 20 is deposited by one or more layers of composite metal. Optionally, the metal lead layer 20 comprises multiple layers of composite metal thin film, the material of the bottom layer of the multiple layers of composite metal thin film comprises one or more of titanium, chromium or silicon carbide, and the thickness of the bottom layer of the multiple layers of composite metal thin film ranges from 5 to 20 nm. In the multiple layers of composite metal thin film, the material of the middle layer comprises one or more of gold or platinum, and the thickness of the middle layer ranges from 50 to 200 nm. In the multiple layers of composite metal thin film, the material of the top layer comprises one or more of titanium, chromium or silicon carbide, and the thickness of the top layer ranges from 5 to 20 nm.

[0096] In some embodiments, the deposition method of the metal lead layer 20 comprises at least one of magnetron sputtering, electron beam evaporation or ion beam deposition.

[0097] In some embodiments, the formation of the plurality of electrode contacts 21, the plurality of electrode pads 22 and the plurality of conductive lines 23 on the metal lead layer 20 comprises at least one of a metal lift-off process, a dry etching process or a wet etching process.

[0098] In some embodiments, a photoresist layer (not shown in the figures) can be coated on the flexible support layer 10, and the photoresist layer is patterned by a photoresist developing process. The area of the flexible support layer 10 not covered by the patterned photoresist layer corresponds to the area of the flexible skin electrode 100 where the metal lead layer 20 is located.

[0099] In some embodiments, after the photoresist is coated on the flexible support layer 10, the upper surface of the flexible support layer 10 covered by the photoresist can be subjected to a plasma treatment. The plasma treatment on the upper surface of the flexible support layer 10 is beneficial to increase the roughness of the upper surface of the flexible support layer 10, and to remove surface impurities, thereby increasing the adhesion between the subsequently deposited metal and the upper surface of the flexible support layer 10.

[0100] For example, in some embodiments, the step of depositing a metal material on the flexible support layer 10 to form the metal lead layer 20 can comprise: Step (1), after the flexible support layer 10 is prepared, before the metal lead layer 20 is prepared, the surface of the flexible support layer 10 is treated by oxygen plasma or a mixed plasma of oxygen and argon; Step (2), a thin film of one or more of titanium, chromium, silicon carbide, gold or platinum is prepared by magnetron sputtering; Step (3), a positive photoresist is spin-coated on the surface of the thin film prepared by magnetron sputtering, and the photoresist is patterned after exposure and development to form a metal lead shape; Step (4), transferring the metal lead shape of the photoresist layer 300 to the magnetron sputtering film layer by a dry etching or wet etching process to form the final metal lead layer 20. Step (5), removing the photoresist.

[0101] In these embodiments, the surface of the flexible support layer 10 is treated by plasma to increase the surface roughness and surface activity of the flexible support layer 10, which is conducive to improving the bonding force between the metal lead layer 20 and the flexible support layer 10. In addition, the metal lead layer 20 is prepared by a magnetron sputtering process, which is conducive to further improving the bonding force between the flexible support layer 10 and the metal lead layer 20.

[0102] Alternatively, in some embodiments, the step of depositing a metal material on the flexible support layer 10 to form the metal lead layer 20 can include: Step (1), after the flexible support layer 10 is prepared, a negative photoresist is spin-coated on the surface thereof, and exposed and developed to expose the metal lead shape area; Step (2), treating the photoresist exposed area by oxygen plasma or a mixed plasma of oxygen and argon; Step (3), preparing one or more thin films of titanium, chromium, silicon carbide, gold or platinum by electron beam evaporation; Step (4), removing the photoresist by a lift-off process to form the final metal lead layer 20.

[0103] It should be particularly pointed out that, in some embodiments, the materials for preparing the electrode contact 21, the electrode solder joint 22 and the conductive wire 23 can be the same or different.

[0104] In some embodiments, the materials for preparing the electrode contact 21, the electrode solder joint 22 and the conductive wire 23 are the same, and the metal lead layer 20 can only include one metal layer, which can be prepared by a one-time thin film deposition process. For example, the materials for preparing the electrode contact 21, the electrode solder joint 22 and the conductive wire 23 are all the first metal, then the first metal material can be deposited on the flexible support layer 10 to form a first metal layer on the flexible support layer 10, the first metal layer including a metal layer on the photoresist and a metal lead layer 20 on the flexible support layer 10. The first metal layer can include at least one of gold, aluminum, tungsten, platinum and titanium. Taking platinum as the first metal material for example, the platinum material is deposited on the flexible support layer 10 to form a platinum metal layer on the flexible support layer 10, the platinum metal layer including a platinum metal layer on the photoresist and a metal lead layer 20 on the flexible support layer 10, and the platinum metal layer on the photoresist will be removed together with the photoresist finally to obtain the platinum metal layer of the flexible support layer 10, i.e. the metal lead layer 20.

[0105] For example, the first metal material includes platinum and gold (e.g., a platinum layer is first deposited and then a gold layer is deposited), and accordingly, the first metal layer includes a platinum layer and a gold layer which are arranged in a stack, so that the first metal layer is formed on the flexible support layer 10, and the first metal layer includes the first metal layer on the photoresist and the metal lead layer 20 on the flexible support layer 10. That is, the first metal layer refers to a metal layer prepared by a one-time thin film deposition process, and further optionally, one metal material can be deposited or multiple metal materials can be sequentially deposited to form a metal layer in the one-time thin film deposition process.

[0106] In other embodiments, the material for preparing the electrode contact 21 and the electrode pad 22 is not the same. Accordingly, the metal lead layer 20 includes at least a first metal layer and a second metal layer, i.e., the metal lead layer 20 includes multiple metal layers. In these embodiments, multiple photoetching and multiple metal deposition are required in the process of preparing the metal lead layer 20 so as to obtain the metal lead layer 20 with multiple metal layers.

[0107] Specifically, the first metal layer is deposited on the flexible support layer 10, and the first metal layer covers the areas on the flexible support layer 10 corresponding to the electrode contact 21 and the conductive wire 23. Then, the photoresist and the metal layer on the photoresist are removed, and the photoresist is arranged on the flexible support layer 10 and the first metal layer, and the photoresist covers the part of the flexible support layer 10 except the electrode pad 22 and the conductive wire 23. The second metal layer is deposited on the flexible support layer 10 and the first metal layer, and the second metal layer covers the areas on the flexible support layer 10 corresponding to the electrode pad 22 and the conductive wire 23.

[0108] The following is described by taking platinum as the material for preparing the electrode contact 21, gold as the material for preparing the electrode pad 22, and platinum material is first deposited and then gold material is deposited as an example.

[0109] Specifically, the platinum material is deposited on the flexible support layer 10 to form a platinum metal layer, the platinum metal layer includes a platinum metal layer on the photoresist and a first electrode layer on the flexible support layer 10, it should be noted that the pattern of the first electrode layer here is not the metal lead layer 20 in the flexible skin layer electrode 100, the first electrode layer only includes the electrode contact 21 and the conductive wire 23 (the area on the flexible support layer 10 corresponding to the electrode pad 22 is covered by the photoresist, and the electrode pad 22 is not covered by the first electrode layer), that is, the first electrode layer only covers the area on the flexible support layer 10 corresponding to the electrode contact 21 and the conductive wire 23. Then the photoresist is removed, and the part of the flexible support layer 10 not covered by the first electrode layer is exposed. The step of coating the photoresist is repeated, and then the patterned photoresist layer is prepared on the flexible support layer 10 again, the patterned photoresist layer covers the surface of the flexible support layer 10 except the area corresponding to the electrode pad 22 and the conductive wire 23, and then the gold material is deposited to form a gold material layer, the gold material layer includes a part covered on the patterned photoresist layer and a second metal layer covered on the flexible support layer 10, the second metal layer includes a part covering the electrode pad 22 and the conductive wire 23. The first metal layer and the second metal layer together form the metal lead layer 20 in the flexible skin layer electrode 100.

[0110] It should be emphasized that the flexible skin layer electrode 100 adopts a multi-film deposition process, so that each conductive wire 23 prepared includes the first metal layer and the second metal layer.

[0111] It can be understood that during the entire manufacturing process of the flexible skin layer electrode 100, the second metal layer is arranged to cover the first metal layer at the position of the conductive wire 23, so that each conductive wire 23 includes the first metal layer and the second metal layer arranged in layers, thereby avoiding the remaining second metal layer or first metal layer in the conductive wire 23 when the first metal layer or second metal layer of the conductive wire 23 breaks, so that the conductive wire 23 can continue to conduct, thereby effectively improving the stability of the flexible skin layer electrode 100 product.

[0112] At the same time, the electrode layer in the flexible skin layer electrode 100 adopts a multi-film deposition process, which can make the materials of the exposed surfaces of the electrode contact 21 and the electrode pad 22 (i.e. the parts of the electrode contact 21 and the electrode pad 22 not covered by the encapsulation layer) different, so that different materials can fully exert their respective advantages, further optimizing the performance of the flexible skin layer electrode 100.

[0113] Further, by depositing the gold layer (i.e., the second metal layer) on the platinum layer (i.e., the first metal layer) in the following way, i.e., first growing a titanium layer on the platinum layer, and then depositing the gold layer on the titanium layer, the problem of the existence of burrs at the edges of the conductive wire 23 due to the deposition of a platinum layer and then a gold layer on the conductive wire 23, which affects the appearance of the product and even causes the adjacent two conductive wires 23 to be connected, can be avoided.

[0114] In some embodiments, the photoresist can be stripped by a heating water bath using acetone or N-methyl pyrrolidone, and the metal layer on the photoresist is stripped together with the photoresist. For example, the product can be subjected to a heating water bath stripping of the photoresist at 90°C using N-methyl pyrrolidone. After the photoresist is stripped by the heating water bath using acetone or N-methyl pyrrolidone, the electrode layer covering the flexible support layer 10 remains on the flexible support layer 10.

[0115] S14 A groove is processed in the second region of the flexible support layer 10. For example, referring to Figure 12 , the groove is a trapezoidal groove, and the trapezoidal groove is located in the entire region of the surface of the flexible support layer 10 that is not covered by the metal lead layer 20, i.e., forms a snap-in recess. It should be noted that the groove can also be other shapes, such as a spherical groove, a cylindrical groove, etc., which are not limited herein. If not otherwise specified, the following is described by taking the trapezoidal groove as an example, and the structure of the trapezoidal groove is described in the foregoing, which is not repeated here.

[0116] In some embodiments, the trapezoidal groove is further etched from the flexible support layer 10 by a reactive ion etching (RIE) process. By forming the trapezoidal groove by the RIE process, not only is the embedding of the flexible encapsulation layer 30 and the flexible support layer 10 in the macrostructure promoted, but also a series of oxygen-containing functional groups are introduced on the surface of the flexible support layer 10 and the surface roughness is increased, further improving the micro bonding between the two, and better forming the clamping of the metal lead layer 20.

[0117] For example, the etching mask is the metal lead layer 20, and the etching gas is O2 or a mixture of O2+CF4 or O2+CF4+Ar. The cross-sectional shape of the trapezoidal groove is large at the top and small at the bottom, the sidewall angle ranges from 0° to 90°, and the groove depth ranges from 1 μm to 10 μm, or 1 μm to 50 μm, or 1 μm to 100 μm.

[0118] In some embodiments, the side shape of the trapezoidal groove can be adjusted according to the RIE process parameters, which have been described above and will not be repeated here. In some examples, by keeping the etching gas, pressure and power unchanged, a straight side profile can be formed. In some examples, by keeping the etching gas and pressure unchanged and gradually reducing the etching power, a convex side profile can be formed. In some examples, by keeping the etching gas and pressure unchanged and gradually increasing the etching power, a concave side profile can be formed. In some examples, by keeping the etching gas and pressure unchanged, gradually increasing (or decreasing) the etching power, and then gradually decreasing (or increasing) the etching power, and repeating the above process one or more times, an S-shaped side profile can be formed. As mentioned above, it should be noted that, at the same etching aspect ratio, the S-shaped curve side can obtain better results for the improvement of the bonding force emphasized in the present application.

[0119] It should be noted that, in order to achieve the best embedding of the subsequent flexible encapsulation layer 30, the appropriate groove size can be selected according to the actual etching aspect ratio, and the groove with the preset size can be obtained by adjusting the RIE process parameters. In some examples, by keeping the etching gas and pressure unchanged and slowly increasing (or decreasing) the etching power, the side tangent angle θ of the trapezoidal groove is slowly increased (or decreased). The side tangent angle θ of the trapezoidal groove is the angle between the tangent at each point of the side and the horizontal plane of the solid end of the flexible support layer 10, and the range of the angle θ is 0-90°.

[0120] Optionally, in some embodiments, a very thin adhesion promoter (not shown in the figure) can be spin-coated on the surface of the flexible support layer 10 to further improve the effect of the close adhesion between the flexible support layer 10 and the flexible encapsulation layer 30.

[0121] In some embodiments, the step of arranging the flexible encapsulation layer 30 on the flexible support layer 10 and the metal lead layer 20 comprises: S21 forming the flexible encapsulation layer 30 on the flexible support layer 10 and the metal lead layer 20 by using a coating process. In some embodiments, referring to Figure 12 and Figure 13 , the flexible encapsulation layer 30 covers the flexible support layer 10 and the metal lead layer 20, and the metal lead layer 20 is encapsulated in the flexible encapsulation layer 30. The flexible encapsulation layer 30 is selected from one of PI, Parylene-C, SU-8 or PDMS, and the flexible encapsulation layer 30 is coated by spin coating, spraying or chemical vapor deposition.

[0122] Optionally, in some embodiments of the present application, the step of arranging the flexible encapsulation layer 30 on the flexible support layer 10 and the metal lead layer 20 comprises: A polyimide precursor solution is coated on the flexible support layer 10 and the metal lead layer 20, and the polyimide precursor solution on the flexible support layer 10 and the polyimide in the flexible support layer 10 which is not completely cured are together subjected to a second stepwise temperature rise to 300-400°C, to obtain a flexible packaging layer 30, and the flexible support layer 10 and the flexible packaging layer 30 are both completely cured.

[0123] Exemplarily, the material for preparing the flexible packaging layer 30 is PI, such as any one of PI2610, JA-902, P12611, PMR-15, AFR-PE-4, etc., and a precursor solution thereof is coated on the surface of the flexible support layer 10 and the metal lead layer 20. Under the action of centrifugal force, the PI precursor solution flows to fill the trapezoidal grooves on the surface of the flexible support layer 10 and covers the metal lead layer 20. The flexible packaging layer 30 is completely cured by temperature rise, to form a reliable package with a thickness in the range of 5-1000 μm.

[0124] Specifically, the sample is pre-baked, and after being cooled to room temperature, a polyimide precursor solution is spin-coated on the flexible support layer 10 and the metal lead layer 20. After baking the sample to 80°C, the sample is baked for 10 min. The temperature is raised to 120-140°C at a rate of 1-2°C per minute, and the sample is kept at this temperature for 30 min. Then the temperature is raised to 180-220°C at a rate of 1-2°C per minute, and the sample is kept at this temperature for 60 min, so that the flexible packaging layer 30 forms an incomplete curing structure as the flexible support layer 10. Then the temperature is raised to 300-400°C at a rate of not more than 3°C per minute, and the sample is kept at this temperature for 60 min. When the curing temperature is raised to 300°C (for 60 min) - 360°C (for 60 min) - 400°C (for 60 min), i.e. the temperature is sequentially raised from 300°C to 360°C, and then to 400°C, and the sample is kept at each preset temperature for 60 min, the polyimide on the flexible support layer 10 and the polyimide in the flexible support layer 10 which is not completely cured are sufficiently imidized, so that intermolecular bonding is formed between the flexible support layer 10 and the flexible packaging layer 30, which is beneficial to further increasing the bonding force between the flexible support layer 10 and the flexible packaging layer 30. Finally, the temperature is reduced to room temperature at a rate of not more than 4°C per minute.

[0125] It is emphasized that in the process of preparing the flexible encapsulation layer 30, the raw material for preparing the flexible encapsulation layer 30 is subjected to stepwise temperature rising and solidification, so that the raw material not completely solidified in the flexible support layer 10 is further subjected to solidification cross-linking reaction in the process of preparing the flexible encapsulation layer 30, the molecular chains in the PI film formed flow, and the filling and fitting of the flexible encapsulation layer 30 to the trapezoidal grooves on the surface of the flexible support layer 10 are promoted, which is beneficial to further increase the interfacial bonding force between the flexible encapsulation layer 30 and the flexible support layer 10 and to further improve the stability of the flexible skin layer electrode 100, thereby prolonging the service life of the flexible skin layer electrode 100.

[0126] It is particularly stated that the flexible encapsulation layer 30 is filled into the flexible support layer 10 during the deposition process, and after the temperature rising and solidification process, the flexible encapsulation layer 30 forms downward trapezoidal protrusions, i.e., the engaging protrusions, which are adapted to each other in shape with the trapezoidal grooves provided on the flexible support layer 10, i.e., the stable fitting connection between the engaging recesses and the engaging protrusions is formed. The trapezoidal protrusion region includes all regions on the lower surface of the flexible encapsulation layer 30 except the region corresponding to the metal lead layer 20. The height of the trapezoidal protrusion ranges from 1 to 100 μm, and the angle between the side profile and the horizontal plane ranges from 0 to 90°.

[0127] It should be noted that the trapezoidal protrusions are formed by the flow filling of the flexible encapsulation layer 30, so the trapezoidal protrusions and the aforementioned trapezoidal grooves are complementary in shape. That is, the trapezoidal protrusions are wide at the top and narrow at the bottom, and the side edges can be linear, outwardly convex, inwardly convex, or S-shaped. The linear shape, the inwardly convex curve, the outwardly convex curve, and the S curve are characterized in that the tangent line at any point on the line and the horizontal angle θ of the physical end of the flexible encapsulation layer 30 range from 0 to 90°.

[0128] In some embodiments, after the flexible encapsulation layer 30 is prepared, the preparation method further comprises: S22 drilling holes in the flexible encapsulation layer 30, please refer to Figure 14 to expose the electrode contact area 24 and the electrode pad area 25.

[0129] In some examples, the thickness of the flexible encapsulation layer 30 is not more than 10 μm, and when the etching rate of the material and the photoresist of the flexible encapsulation layer 30 in oxygen plasma is close to 1:1 or higher, a thick photoresist can be directly used as an etching barrier layer, which reduces the process cost and process complexity.

[0130] The specific implementation process is as follows: Step (1), spin coating a photoresist of suitable thickness on the surface of the flexible encapsulation layer 30, and sequentially performing photoetching, developing, and hardening steps to form a photoresist pattern, i.e., no photoresist on the electrode contact area 24 and the electrode solder area 25, and photoresist everywhere else; Step (2), etching the flexible encapsulation layer 30 to the metal lead layer 20 by a reactive ion etching process with O2 or a mixture of O2+CF4 or O2+CF4+Ar; Step (3), removing the photoresist barrier layer by dry or wet method.

[0131] In some examples, when the thickness of the flexible encapsulation layer 30 exceeds 10 μm, or the selection ratio of the material of the flexible encapsulation layer 30 and the photoresist is less than 1:1, an etching hard mask layer needs to be additionally prepared. The etching hard mask material is one of silicon dioxide, silicon nitride, aluminum, or chromium. The etching hard mask is prepared by a lift-off process or an etching process.

[0132] The specific implementation process is as follows: Step (1), depositing one of silicon dioxide, silicon nitride, aluminum, or chromium as the etching hard mask material on the surface of the flexible encapsulation layer 30; Step (2), spin coating a photoresist on the surface of the etching hard mask layer, and sequentially performing photoetching, developing, and hardening steps to form a photoresist pattern, i.e., no photoresist on the electrode contact area 24 and the electrode solder area 25, and photoresist everywhere else; Step (3), transferring the photoresist pattern to the surface of the etching hard mask material by a wet or dry etching process, and removing the photoresist; Step (4), etching the flexible encapsulation layer 30 to the metal lead layer 20 by a reactive ion etching process with O2 or a mixture of O2+CF4 or O2+CF4+Ar; Step (5), removing the etching hard mask material layer.

[0133] Another specific implementation process is as follows: Step (1), uniformly coating a photoresist on the flexible encapsulation layer 30 and performing photoetching, developing, and hardening steps to form a photoresist pattern. The photoresist pattern is specifically that there is photoresist on the electrode contact area 24 and the electrode solder area 25, and no photoresist everywhere else; Step (2), depositing an etching hard mask material such as silicon dioxide, silicon nitride, chromium, or aluminum on the photoresist pattern; Step (3), forming an etching hard mask layer by a lift-off process; Step (4), etching the flexible encapsulation layer 30 to the metal lead layer 20 by a reactive ion etching process with O2 or a mixture of O2+CF4 or O2+CF4+Ar; Step (5), removing the etching hard mask material layer.

[0134] In some embodiments, after the step of opening holes on the flexible encapsulation layer 30, the preparation method further includes: S23 covering the electrode contact 21 with an electrode modification layer 40, see Figure 15 .

[0135] Exemplarily, the electrode modification layer 40 is a one or more layer composite structure, which is beneficial to reduce the electrode surface impedance, improve the signal-to-noise ratio of the neural signal acquisition, and increase the charge injection capacity in the neural stimulation stage.

[0136] Exemplarily, the electrode modification layer 40 material includes one or more of titanium, chromium, gold, platinum, iridium, iridium oxide, titanium nitride, PEDOT, and CNTs. The electrode modification layer 40 deposition process includes electron beam evaporation, magnetron sputtering, and electrodeposition process. The electrode modification layer 40 patterning process includes etching and lift-off process. It can be understood that the electrode modification layer 40 deposits metal on the electrode contact 21 of the flexible skin layer electrode 100, so that a metal layer is added on the electrode contact 21, thereby making the electrode contact 21 flush with the flexible packaging layer 30 or the electrode contact 21 higher than the flexible packaging layer 30, so that the flexible skin layer electrode 100 is more beneficial to the acquisition of neural signals, thereby improving the signal-to-noise ratio of neural signal acquisition and electrode biocompatibility.

[0137] In some examples, uniform glue photo lithography is performed on the flexible packaging layer 30 to expose the electrode contact 21 and the area 5-50 μm outside the edge thereof. Then, titanium / platinum metal layers are respectively deposited by electron beam evaporation, and patterning is achieved by lift-off process. Finally, porous platinum is deposited on the patterned surface by electrodeposition process to achieve the purpose of electrode modification. Of course, in another embodiment of the present application, at least one of porous gold, PEDOT, or PEDOT / CNTs composite layer can be deposited on the patterned surface by electrodeposition process to achieve the purpose of electrode modification.

[0138] In some examples, uniform glue photo lithography is performed on the flexible packaging layer 30 to expose the electrode contact 21 and the area 5-50 μm outside the edge thereof. Then, titanium / iridium oxide is respectively deposited by magnetron sputtering, and electrode modification is achieved by lift-off process.

[0139] In some examples, the preparation method further comprises: S24 etching the contact area 24 of the flexible skin layer electrode 100 to open a through hole to form a hollow hole 50, In combination with Figure 1 and Figure 16As shown. A material resistant to plasma etching such as silicon dioxide, metal chromium or metal aluminum is deposited on the flexible encapsulation layer 30 as an etching mask layer. The etching mask layer is patterned by etching or lift-off process. The etching depth of the hollow hole 50 is the thickness of the flexible encapsulation layer 30 plus the thickness of the flexible support layer 10. The shape of the hollow hole 50 can be circular, rectangular, triangular or various irregular shapes, etc. The hollow holes 50 are distributed in the electrode contact area 24, more specifically, between the electrode contacts 21. By forming a plurality of hollow holes 50 in the electrode contact area 24 of the flexible skin layer electrode 100, it helps to better maintain a good environment for the brain, and can increase the flexibility of the flexible skin layer electrode 100 as a whole, so as to form a good common adhesion with the brain tissue. At the same time, the open hole design of the electrode contact area 24 can promote the circulation of cerebrospinal fluid, help to maintain the health of the brain, promote the cleaning and normal function of the brain, and thus reduce the abnormal deposition and aggregation of harmful proteins and the risk of other brain diseases.

[0140] In some embodiments, the preparation method further comprises: S25 etching to form an electrode release groove (not shown) in the electrode edge extension area.

[0141] The electrode release groove is an area with a width of 50-500 μm extending outward from the electrode edge, and has a structure similar to that of the hollow hole 50. The purpose is to facilitate the overall release of the flexible skin layer electrode 100 from the substrate 200. The electrode release groove and the local hollow hole 50 are both formed by etching through the flexible encapsulation layer 30 and the flexible support layer 10 by a reactive ion etching process.

[0142] The specific implementation process is as follows: Step (1), uniform glue photo etching development is performed on the flexible encapsulation layer 30 to form the shape of the electrode release groove and the hollow hole 50; Step (2), an etching mask layer material such as silicon dioxide, silicon nitride, chromium or aluminum is deposited; Step (3), the etching mask layer is patterned by lift-off process; Step (4), the flexible encapsulation layer 30 and the flexible support layer 10 are etched through in the electrode release groove and the hollow hole 50 area by a reactive ion etching process; Step (5), the etching mask layer is removed.

[0143] In some embodiments, the preparation method further comprises: S26 peeling off the flexible support layer 10 from the silicon wafer substrate 200 to release the flexible skin layer electrode 100, as shown. Figure 17 ​Optionally, in some embodiments, a sacrificial layer is arranged between the silicon wafer substrate 200 and the flexible support layer 10, the silicon wafer substrate 200 with the sacrificial layer is placed in an acidic or alkaline solution, and the flexible support layer 10 is released from the silicon wafer substrate 200 by the reaction of the sacrificial layer with the acidic or alkaline solution.

[0144] The above describes the technical solutions of the embodiments of the present application in detail. The principles and implementation manners of the present application are described by using specific examples. The above description of the embodiments is only used to help understand the method of the present application and its core idea. Meanwhile, for those skilled in the art, the specific implementation manners and application ranges can be changed according to the idea of the present application, and the technical features of different embodiments can be freely combined. In summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A flexible skin electrode, characterized by, The flexible skin layer electrode comprises a flexible support layer, a metal lead layer and a flexible encapsulation layer arranged in a stack; The metal lead layer is arranged between the flexible support layer and the flexible encapsulation layer; the metal lead layer comprises a plurality of spaced apart conductive wires; The flexible encapsulation layer covers the flexible support layer and the metal lead layer; wherein, The flexible support layer and / or the flexible encapsulation layer are provided with a plurality of protrusions on the side facing the metal lead layer, at least part of the protrusions are embedded between two adjacent conductive wires, and the protrusions form a clamping of the metal lead layer.

2. The flexible skin electrode of claim 1, wherein, The area of the flexible support layer covered by the metal lead layer is a first area; the area of the flexible support layer not covered by the metal lead layer is a second area; The flexible support layer is provided with a plurality of first fitting parts on the side facing the flexible encapsulation layer, the first fitting parts are arranged in the second area, the flexible encapsulation layer is provided with second fitting parts matched with the first fitting parts, the flexible support layer and the flexible encapsulation layer are connected by the first fitting parts and the second fitting parts, the first fitting parts and / or the second fitting parts comprise the protrusions, and the protrusions, the first fitting parts or the second fitting parts and the flexible support layer, the flexible encapsulation layer form a clamping of the metal lead layer.

3. The flexible skin electrode of claim 2, wherein, One of the first fitting parts and the second fitting parts is a groove, and the other is a protrusion matched with the groove, and the protrusion comprises the protrusions; And / or, the number of the first fitting parts is a plurality, and the plurality of first fitting parts are arranged in the second area.

4. The flexible skin electrode of claim 3, wherein, The first fitting part is a groove, the second fitting part is a protrusion, the end of the groove close to the flexible encapsulation layer is the upper end of the groove, the end of the groove close to the flexible support layer is the lower end of the groove, and the horizontal cross section of the groove gradually increases along the direction from the lower end to the upper end.

5. The flexible skin electrode of claim 4, wherein, The vertical cross section of the groove is at least one of trapezoidal, circular arc, sawtooth and square; And / or, the depth of the groove ranges from 0.1 μm to 50 μm.

6. The flexible skin electrode of claim 5, wherein, The groove is a trapezoidal groove, and the side profile of the trapezoidal groove is a straight line or a curve; And / or, the angle θ between the tangent line of any point on the side profile of the trapezoidal groove and the horizontal plane ranges from 0 to 90°; And / or, the curve comprises an outward concave curve, an inward concave curve, or an S curve formed by alternating combination of the outward concave curve and the inward concave curve one or more times.

7. The flexible skin electrode according to any one of claims 4 to 6, wherein, The flexible encapsulation layer comprises an encapsulation body layer and the protrusions arranged on the side of the encapsulation body layer facing the flexible support layer, the protrusions comprise protruding parts embedded in the grooves and the protrusions, and the protrusions and the encapsulation body layer are connected by the protrusions.

8. The flexible skin electrode of claim 7, wherein, The groove is a trapezoidal groove, the width of the upper end of the trapezoidal groove is greater than the width of the lower end of the trapezoidal groove, the protruding part is a trapezoidal protrusion matched with the trapezoidal groove, and the protruding part, the protrusions and the encapsulation body layer are an integral structure.

9. The flexible skin electrode of claim 8, wherein, Two of the conductive lines arranged adjacently comprise conductive line segments arranged in parallel and at intervals, and the protrusions are arranged between two of the conductive line segments arranged in parallel and at intervals; And / or, the protrusions have a rectangular cross section; And / or, the protrusions have the same extension direction as the conductive lines; And / or, the width of the protrusions is equal to the distance between two adjacent conductive lines; And / or, the thickness of the protrusions is equal to the thickness of the metal lead layer.

10. A method of making the flexible skin electrode of any one of claims 1-9, wherein, The method comprises the following steps: providing a flexible support layer and a metal lead layer arranged in layers; wherein, forming the flexible support layer on the surface of the substrate, and configuring the flexible support layer to be heated to 180-220°C in the first step, and the flexible support layer is not completely cured; depositing metal material on the flexible support layer to form a metal lead layer; covering the flexible support layer and the metal lead layer with a flexible encapsulation layer to obtain the flexible skin layer electrode; wherein, configuring the flexible support layer and the flexible encapsulation layer to be heated to 300-400°C in the second step, and the flexible support layer and the flexible encapsulation layer are completely cured.

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