Flexible skin electrode and method of making same

Abstract

The application discloses a flexible skin layer electrode and a preparation method thereof, and relates to the technical field of brain-computer interface. The flexible skin layer electrode comprises a flexible supporting layer, a metal lead layer and a flexible packaging layer which are arranged in a stack. The metal lead layer is arranged between the flexible supporting layer and the flexible packaging layer. The metal lead layer comprises a plurality of spaced conductive wires. The flexible packaging layer covers the flexible supporting layer and the metal lead layer. The side of the flexible supporting layer and / or the flexible packaging layer facing the metal lead layer is provided with a plurality of protrusions. At least part of the protrusions are embedded between two adjacent conductive wires, and the protrusions form clamping to the metal lead layer. The application increases the force between the flexible supporting layer and / or the flexible packaging layer and the metal lead layer, thereby improving the problem that the metal lead layer is easy to fall off and improving the stability of the flexible skin layer electrode.

Description

Technical Field

[0001] This application relates to the field of brain-computer interface technology, and in particular to a flexible cortical electrode and its preparation method. Background Technology

[0002] Brain-computer interfaces (BCIs) are an important technology that connects the brain directly to a computer or other external devices via sensing terminals. This allows for the extraction and decoding of brain signals, ultimately converting them into command signals that can be used to control the external devices. A key function of BCIs is information extraction—the process of reading information from the brain.

[0003] Currently, there are generally two methods for information extraction: non-implantable and implantable. Non-implantable methods involve reading EEG (electroencephalogram) data using an EEG cap worn on the scalp; while implantable methods include obtaining EEG data through fully implantable microelectrode arrays, microneedle electrodes, deep brain electrodes, or flexible cortical electrodes. Among these technologies, flexible cortical electrodes are typically attached to the dura mater or subdural cortex surface via minimally invasive surgery. Due to their high signal resolution, relatively long-term stability, and relatively low invasiveness, flexible cortical electrodes can achieve good conformal adhesion to brain tissue, significantly reducing inflammatory responses caused by minute displacements, thus finding widespread application in the field of brain-computer interfaces.

[0004] Currently, flexible cortical electrodes typically consist of a bottom flexible support layer and a top flexible encapsulation layer made of polymer materials, as well as an intermediate metal lead layer made of metallic materials. Although flexible cortical electrodes can significantly alleviate inflammatory responses, they are prone to failure, such as lead layer detachment, during long-term implantation. The reasons for this failure are twofold: firstly, due to the water-absorbing properties of the polymer materials in flexible cortical electrodes, prolonged operation in a physiological fluid environment can lead to interlayer delamination caused by the infiltration of physiological fluid; continuous external nerve signals further exacerbate this infiltration. Secondly, the weak bonding between the metal and polymer materials makes the metal lead layer prone to oscillation and detachment under the continuous influence of low-frequency nerve signals. Both of these situations damage the original structure of the flexible cortical electrode, resulting in partial loss of electrode function and limiting its long-term implantable application in vivo.

[0005] Therefore, there is an urgent need to provide a flexible skin electrode with better stability. Summary of the Invention

[0006] In view of this, this application provides a flexible skin electrode and a method for preparing the same, aiming to improve the stability of the flexible skin electrode.

[0007] The first aspect of this application provides a flexible skin electrode, which includes a flexible support layer, a metal lead layer and a flexible encapsulation layer stacked together;

[0008] The metal lead layer is disposed between the flexible support layer and the flexible encapsulation layer; the metal lead layer includes multiple spaced conductive lines;

[0009] The flexible encapsulation layer covers the flexible support layer and the metal lead layer; wherein...

[0010] The flexible support layer and / or the flexible encapsulation layer have a plurality of protrusions on the side facing the metal lead layer, and at least some of the protrusions are embedded between two adjacent conductive lines, forming a clamping effect on the metal lead layer between the protrusions.

[0011] In some embodiments, the area on the flexible support layer covered by the metal lead layer is a first region; the area on the flexible support layer not covered by the metal lead layer is a second region.

[0012] The flexible support layer has a plurality of first fitting portions on the side facing the flexible encapsulation layer. The first fitting portions are disposed in the second region. The flexible encapsulation layer has a second fitting portion adapted to the first fitting portions. The flexible support layer and the flexible encapsulation layer are connected by fitting the first fitting portions and the second fitting portions. The first fitting portion and / or the second fitting portion includes the protrusion. The protrusion and the first fitting portion or the second fitting portion, as well as the flexible support layer and the flexible encapsulation layer, form a clamping effect on the metal lead layer.

[0013] In some embodiments, one of the first fitting portion and the second fitting portion is a groove, and the other of the first fitting portion and the second fitting portion is a protrusion adapted to the groove, the protrusion including the convex strip.

[0014] In some embodiments, the number of the first fitting portions is multiple, and the multiple first fitting portions are spaced apart in the second region.

[0015] In some embodiments, the first fitting portion is a groove, the second fitting portion is a protrusion, the end of the groove near the flexible encapsulation layer is the upper end of the groove, the end of the groove near 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.

[0016] In some embodiments, the vertical cross-section of the groove is at least one of trapezoidal, arc-shaped, sawtooth-shaped, and square.

[0017] In some embodiments, the depth of the groove ranges from 0.1 μm to 50 μm.

[0018] In some embodiments, the groove is a trapezoidal groove, and the side profile of the trapezoidal groove is straight or curved.

[0019] In some embodiments, the angle θ between the tangent at any point on the side profile of the trapezoidal groove and the horizontal plane ranges from 0 to 90°.

[0020] In some embodiments, the curve shape includes an externally concave curve shape, an internally concave curve shape, or an S-curve shape formed by alternating combinations of externally concave curves and internally concave curves once or multiple times.

[0021] In some embodiments, the flexible encapsulation layer includes an encapsulation body layer and a protrusion disposed on the side of the encapsulation body layer facing the flexible support layer. The protrusion includes a protrusion embedded in the groove and a ridge connecting the protrusion and the encapsulation body layer.

[0022] In some embodiments, 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, and the protrusion is a trapezoidal protrusion adapted to the trapezoidal groove; the protrusion, the protrusion strip and the encapsulation body layer are an integral structure.

[0023] In some embodiments, two adjacent conductive lines comprise parallel and spaced-apart conductor segments, and the protrusion is disposed between two adjacent parallel and spaced-apart conductor segments.

[0024] In some embodiments, the cross-section of the convex strip is rectangular.

[0025] In some embodiments, the extension direction of the protrusion is the same as the extension direction of the conductive wire.

[0026] In some embodiments, the width of the protrusion is equal to the distance between two adjacent conductive lines;

[0027] In some embodiments, the thickness of the protrusion is equal to the thickness of the metal lead layer.

[0028] A second aspect of this application provides a method for preparing the aforementioned flexible skin electrode, comprising the following steps:

[0029] It provides a flexible support layer and a metal lead layer stacked together; wherein...

[0030] The flexible support layer is formed on the substrate surface, and the flexible support layer is configured to be heated to 180℃-220℃ in a first step, during which the flexible support layer is not completely cured.

[0031] A metal lead layer is formed by depositing a metal material on the flexible support layer;

[0032] A flexible encapsulation layer is then applied to the flexible support layer and the metal lead layer to obtain the flexible skin electrode; wherein...

[0033] The flexible support layer and the flexible encapsulation layer are subjected to a second step temperature increase to 300℃-400℃, during which both the flexible support layer and the flexible encapsulation layer are completely cured.

[0034] Beneficial effects:

[0035] In this application, a plurality of protrusions are provided on the side of the flexible support layer and / or the flexible encapsulation layer facing the metal lead layer. At least some of the protrusions are embedded between two adjacent conductive wires, forming a clamping effect on the metal lead layer between the protrusions. This allows the protrusions to limit the corresponding conductive wires, which helps to prevent the conductive wires from falling off. Furthermore, when the flexible skin electrode operates in the body for a long time, the flexible encapsulation layer and the flexible encapsulation layer made of polymer material absorb water and expand, which further increases the limiting effect of the protrusions on the conductive wires, further improving the problem of conductive wire detachment and enhancing the stability of the flexible skin electrode. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the structure of the flexible skin electrode provided in some embodiments;

[0038] Figure 2 for Figure 1 A schematic diagram of the cross-section of plane A-A'.

[0039] Figure 3 for Figure 1 A schematic diagram of the cross-section of plane B-B'.

[0040] Figure 4 This is a schematic diagram of the structure at the interface between the flexible support layer and the flexible encapsulation layer in some embodiments;

[0041] Figure 5 This is a schematic diagram of the structure at the interface between the flexible support layer and the flexible encapsulation layer in some embodiments;

[0042] Figure 6 This is a schematic diagram of the structure at the interface between the flexible support layer and the flexible encapsulation layer in some embodiments;

[0043] Figure 7 This is a schematic diagram of the structure at the interface between the flexible support layer and the flexible encapsulation layer in some embodiments;

[0044] Figure 8 This is a process flow diagram for the fabrication of the flexible skin electrode in some embodiments;

[0045] Figures 9-17 These are schematic diagrams of the product structures corresponding to different steps in the fabrication process of the flexible skin electrode in some embodiments.

[0046] Icon labels:

[0047] 100. Flexible skin electrode; 10. Flexible support layer; 11. First mating part; 20. Metal lead layer; 21. Electrode contact; 22. Electrode solder joint; 23. Conductive wire; 24. Contact area; 25. Solder joint area; 30. Flexible encapsulation layer; 31. Encapsulation body layer; 32. Second mating part; 321. Protrusion; 322. Protrusion strip; 40. Electrode decoration layer; 50. Hole; 200. Substrate. Detailed Implementation

[0048] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application. Different components and technical features described in different embodiments herein can be freely combined and used with each other.

[0049] 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 this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0050] In this application, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or operating state, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative purposes and do not impose numerical requirements or establish a numerical order.

[0051] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0052] In this application, "at least one" means one or more, and "more than one" means two or more. "One or more", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0053] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that 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., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0054] Combination Figures 1 to 7 As shown, this application provides a flexible skin electrode 100, which includes a flexible support layer 10, a metal lead layer 20, and a flexible encapsulation layer 30. This flexible skin electrode 100 improves the stability of the flexible skin electrode 100 by increasing the interaction force between the flexible support layer 10 and / or the flexible encapsulation layer 30 and the metal lead layer 20, thereby mitigating the problem of the metal lead layer 20 being prone to detachment. It should be noted that the reference numeral "X1 (X)" in the accompanying drawings indicates that the structural component represented by X1 is subordinate to the structural component represented by X. Figure 1 For example, “23 (20)” in the text, “23” represents a conductive wire and “20” represents a metal lead layer. The conductive wire belongs to the metal lead layer.

[0055] In some embodiments, the flexible sheath electrode 100 includes a flexible support layer 10, a metal lead layer 20, and a flexible encapsulation layer 30 stacked together; the metal lead layer 20 is disposed between the flexible support layer 10 and the flexible encapsulation layer 30; the metal lead layer 20 includes a plurality of spaced conductive lines 23; the flexible encapsulation layer 30 covers the flexible support layer 10 and the metal lead layer 20; wherein, the flexible support layer 10 and / or the flexible encapsulation layer 30 has a plurality of protrusions 322 on the side facing the metal lead layer 20, at least some of the protrusions 322 are embedded between two adjacent conductive lines 23, and the protrusions 322 form a clamping effect on the metal lead layer 20.

[0056] Understandably, in this embodiment, by providing a plurality of protrusions 322 on the side of the flexible support layer 10 and / or the flexible encapsulation layer 30 facing the metal lead layer 20, at least some of the protrusions 322 are embedded between two adjacent conductive lines 23, thereby limiting and clamping the corresponding conductive lines 23, which helps to prevent the metal lead layer 20 from falling off. Furthermore, when the flexible skin electrode 100 operates 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 expand, which further increases the limiting effect of the protrusions 322 on the conductive lines 23, further improving the problem of metal lead layer 20 falling off and improving the stability of the flexible skin electrode 100.

[0057] In some embodiments of this application, the flexible sheath electrode 100 includes a flexible support layer 10, a metal lead layer 20, and a flexible encapsulation layer 30 stacked together; the area of ​​the flexible support layer 10 covered by the metal lead layer 20 is a first region; the area of ​​the flexible support layer 10 not covered by the metal lead layer 20 is a second region; the flexible encapsulation layer 30 covers the flexible support layer 10 and the metal lead layer 20; the flexible support layer 10 has a plurality of first fitting portions 11 on the side facing the flexible encapsulation layer 30, the first fitting portions 11 are disposed in the second region, the flexible encapsulation layer 30 has a second fitting portion 32 adapted to the first fitting portions 11, and the flexible support layer 10 and the flexible encapsulation layer 30 are fitted and connected through the first fitting portions 11 and the second fitting portions 32.

[0058] For example, the second fitting portion 32 is a protrusion, and the second fitting portion 32 includes the protruding strip 322. In other embodiments of this application, the first fitting portion 11 may also include the protruding strip 322, which is not limited here.

[0059] Understandably, in this application, by providing a first fitting portion 11 on the flexible support layer 10 and a second fitting portion 32 adapted to the first fitting portion 11 on the flexible encapsulation layer 30, the flexible support layer 10 and the flexible encapsulation layer 30 are fitted together through the first fitting portion 11 and the second fitting portion 32, thereby increasing the connection area between the flexible support layer 10 and the flexible encapsulation layer 30, and thus increasing the bonding force between the flexible support layer 10 and the flexible encapsulation layer 30, which is beneficial to improving the stability of the flexible skin electrode 100.

[0060] Furthermore, the first interlocking portion 11 in this application is disposed in the second region not covered by the metal lead layer 20, thereby avoiding interference between the first interlocking portion 11 and the metal lead layer 20, which helps to simplify the fabrication process of the flexible skin electrode 100.

[0061] Meanwhile, when the flexible skin electrode 100 works in the body for a long time, the flexible encapsulation layer 30 made of polymer material absorbs water and expands. The first interlocking part 11 and the second interlocking part 32 that are interlocked between the flexible support layer 10 and the flexible encapsulation layer 30 are squeezed against each other, which increases the interlayer friction between the two and forms a mutual lock, making it less likely to delaminate. It also forms a clamping effect on the metal lead layer 20, which is conducive to further improving the stability of the flexible skin electrode 100, thereby increasing the service life of the flexible skin electrode 100.

[0062] 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 specifically limited, as long as the flexible support layer 10 and the flexible encapsulation layer 30 can be connected by fitting the first fitting part 11 and the second fitting part 32.

[0063] For example, there are multiple first fitting portions 11, which are spaced apart in the second region. This helps to further increase the bonding force between the flexible support layer 10 and the flexible encapsulation layer 30, and improve the stability of the flexible skin electrode 100.

[0064] Optionally, in some embodiments, the main structure of the flexible cortical electrode 100 includes, from bottom to top, a flexible support layer 10, a metal lead layer 20, a flexible encapsulation layer 30, and an electrode modification layer 40 stacked together; wherein, the bottom flexible support layer 10 is used to support the metal lead layer 20 and serves to insulate and isolate moisture; the middle metal lead layer 20 is used to contact tissue and transmit nerve signals; the top flexible encapsulation layer 30 is used to insulate between metal lead channels and isolate moisture; the electrode modification layer 40 is connected to part of the metal lead layer 20 and is used to increase biocompatibility, electrode injection capability, and nerve signal acquisition signal-to-noise ratio.

[0065] In some embodiments, the flexible support layer 10 is selected from one or more polymer materials such as PI, Parylene-C, SU-8, or PDMS, and its thickness ranges from 5 μm to 1000 μm. Exemplarily, the thickness range of the flexible support layer 10 is 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 two of the above values.

[0066] In some embodiments, the metal lead layer 20 is disposed on the flexible support layer 10, and the metal lead layer 20 includes an electrode contact region 24, an electrode solder joint region 25, and a multi-channel connecting wire region. Exemplarily, the electrode contact region 24 includes one or more electrode contacts 21, the electrode solder joint region 25 includes one or more electrode solder joints 22, and the multi-channel connecting wire region includes multiple spaced conductive lines 23, with each electrode contact 21 and its corresponding electrode solder joint 22 electrically connected via a conductive line 23.

[0067] Optionally, the shape of the electrode contact 21 can be circular, rectangular, or other geometric shapes, without limitation.

[0068] Optionally, the shape of the electrode solder joint 22 can be circular, rectangular or other geometric shape, without limitation.

[0069] In some embodiments, the multi-channel connecting wire region is composed of multiple non-intersecting metal leads, each of which (i.e., conductive wire 23) is connected to an electrode contact 21 and an electrode solder joint 22 at both ends to form a conductive path.

[0070] In some embodiments, the metal lead layer 20 comprises one or more materials selected from titanium, chromium, gold, platinum, and silicon carbide, enabling it to conduct electricity while also maintaining good adhesion to 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 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 two of the above values. This allows the metal lead layer 20 to transmit neural signals more stably.

[0071] In some embodiments, the flexible encapsulation layer 30 is selected from one or more polymer materials such as PI, Parylene-C, SU-8, or PDMS.

[0072] 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 any two of the above values.

[0073] In some embodiments, the electrode modification layer 40 covers the exposed surface of the electrode contact 21 of the flexible encapsulation layer 30 and an area extending 5 μm to 50 μm beyond its edges. The electrode modification layer 40 is selected from one or more materials chosen from gold, platinum, iridium, iridium oxide, titanium nitride, poly(3,4-ethylenedioxythiophene) (PEDOT), and carbon nanotubes (CNTs). This improves the stability of the flexible cortical electrode 100 and enhances the signal-to-noise ratio of neural signal acquisition and electrode biocompatibility.

[0074] Optionally, in some embodiments, one of the first fitting portion 11 and the second fitting portion 32 is a groove, and the other of the first fitting portion 11 and the second fitting portion 32 is a protrusion adapted to the groove. For example, the first fitting portion 11 is a groove, and the second fitting portion 32 is a protrusion. Of course, in other embodiments of this application, the first fitting portion 11 may be a protrusion, and the second fitting portion 32 may be a groove. Naturally, the first fitting portion 11 and the second fitting portion 32 may also have other structures, which are not limited here. For ease of understanding, the following further explanation uses the example of the first fitting portion 11 being a groove and the second fitting portion 32 being a protrusion.

[0075] Optionally, the first fitting portion 11 is a groove, which can also be understood as the upper surface of the flexible support layer 10 having at least one groove. For example, the upper surface of the flexible support layer 10 has multiple grooves. Correspondingly, the second fitting portion 32 is a protrusion with a shape similar to the groove, which can also be understood as the lower surface of the flexible encapsulation layer 30 having at least one protrusion. Here, the shape of the protrusion matching the groove means that the shapes of the protrusion and the groove are complementary, which can also be understood as the protrusion being able to fill or be embedded in the groove.

[0076] In some embodiments, the first fitting portion 11 is a groove, and the second fitting portion 32 is a protrusion. The end of the groove near the flexible encapsulation layer 30 is the upper end of the groove, and the end of the groove near the flexible support layer 10 is the lower end of the groove. Along the direction from the lower end to the upper end, the horizontal cross-section of the groove gradually increases. This simplifies the process steps for fabricating the groove on the flexible support layer 10, and improves production efficiency and product stability.

[0077] In some embodiments, the vertical cross-section of the groove is at least one of trapezoidal, arc-shaped, sawtooth-shaped, square, or irregularly shaped. Exemplarily, the vertical cross-section of the groove is trapezoidal; this can also be understood as the cross-section of the groove being trapezoidal or similar to a trapezoid. Alternatively, the contour of the groove on the vertical cross-section (e.g., the B-B' plane) is trapezoidal or substantially trapezoidal, and can also be called a trapezoidal groove. It should be noted that the vertical cross-section of the groove can also be understood as a surface perpendicular to the multi-channel connecting wires, or a surface perpendicular to the length direction of the flexible skin electrode 100.

[0078] In some embodiments, the groove has a structure that is wider at the top and narrower at the bottom. Further, the groove has a trapezoidal structure that is wider at the top and narrower at the bottom. This simplifies the process steps for fabricating the groove on the flexible support layer 10, and improves production efficiency and product stability.

[0079] In some embodiments, the trapezoidal groove is located on the surface of the flexible encapsulation layer 30 and avoids the area of ​​the flexible encapsulation layer 30 covered by the metal lead layer 20. This helps to further improve the bonding force between the flexible support layer 10 and the flexible encapsulation layer 30, and also simplifies the manufacturing process.

[0080] In some embodiments, the recess depth of the trapezoidal groove ranges from 0.1 μm to 50 μm. Exemplarily, the recess 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, or any value between any two of the above. This facilitates a stronger bond between the flexible support layer 10 and the flexible encapsulation layer 30, and avoids incomplete filling of the grooves on the surfaces of the flexible encapsulation layer 30 and the flexible support layer 10 due to substrate flatness issues in subsequent flexible encapsulation layer 30 processing steps. It should be noted that the recess depth of the trapezoidal groove can also be selected based on the linewidth and spacing of the metal lead layer 20, and is not limited here.

[0081] In some embodiments, the angle between the tangent at any point on the side profile of the trapezoidal groove and the horizontal plane is defined as θ, and the value of θ ranges from 0 to 90°. For example, the value of θ ranges from 1°, 5°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 85°, 89°, and any two of the above values.

[0082] In some embodiments, please refer to Figures 4 to 7 The side profile of the trapezoidal groove can be straight or curved, without limitation. Furthermore, the curved shape can be an externally concave curve, an internally concave curve, or an S-curve formed by alternating externally and internally concave curves once or multiple times. It should be noted that if the side profile of the trapezoidal groove is curved, under the same etching depth-to-width ratio, the curved side can provide more contact area between the two, which is beneficial for further improving the bonding force between the flexible support layer 10 and the flexible encapsulation layer 30.

[0083] 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. This facilitates contact between the electrode contact 21 and the tissue, improving signal stability.

[0084] 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 solder joint 22. This facilitates electrical connection between the electrode solder joint 22 and an external device.

[0085] In some embodiments, the flexible encapsulation layer 30 covers the flexible support layer 10 and the metal lead layer 20, and only forms exposed surfaces at the electrode contacts 21 and the electrode solder joints 22. This facilitates increasing the area covered by the flexible encapsulation layer 30 and improving the encapsulation effect of the flexible sheath electrode 100 in this application.

[0086] In some embodiments, the upper surface of the flexible support layer 10 is provided with multiple trapezoidal grooves, and the lower surface of the flexible encapsulation layer 30 is provided with multiple trapezoidal protrusions, each trapezoidal protrusion being 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 interlock with each other. This arrangement serves two purposes: first, it increases the contact area between the flexible support layer 10 and the flexible encapsulation layer 30; second, when the flexible skin electrode 100 operates 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 trapezoidal protrusions between the flexible support layer 10 and the flexible encapsulation layer 30 interlock and press against each other, the interlayer friction between the two can be increased, forming an interlocking structure that makes it less prone to delamination, thereby improving the service life of the flexible skin electrode 100.

[0087] For example, the lower surface of the flexible encapsulation layer 30 is provided with multiple protrusions, and the upper surface of the flexible support layer 10 is provided with multiple grooves. The multiple protrusions and multiple grooves are provided in a one-to-one correspondence, with each protrusion embedded in a corresponding groove. This helps to further increase the connection area between the flexible support layer 10 and the flexible encapsulation layer 30, thereby increasing the bonding force between the flexible support layer 10 and the flexible encapsulation layer 30. Furthermore, the groove is a trapezoidal groove, and correspondingly, the end of the protrusion near the groove includes a trapezoidal protrusion adapted to the trapezoidal groove. It can also be understood that the trapezoidal protrusion and the trapezoidal groove on the surface of the flexible support layer 10 are complementary in shape.

[0088] In some embodiments, the flexible encapsulation layer 30 includes an encapsulation body layer 31 and a protrusion (i.e., a second fitting portion 32) disposed on the side of the encapsulation body layer 31 facing the flexible support layer 10. The protrusion includes a protrusion 321 embedded in the groove and a protrusion 322 connecting the protrusion 321 and the encapsulation body layer 31. Further, the shape of the protrusion is adapted to the groove, and the encapsulation body layer 31, the protrusion 322, and the protrusion are an integral structure. The outline of the protrusion in the vertical cross-section (e.g., the B-B' plane) is generally a combination of a trapezoidal protrusion (i.e., the protrusion 321) and a rectangular protrusion (i.e., the protrusion 322); wherein, the rectangular protrusion is disposed 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. Understandably, the rectangular protrusions can strengthen the clamping of the metal lead layer 20, thereby improving the problem of the metal lead layer 20 being easy to fall off; the trapezoidal protrusions are 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.

[0089] In some embodiments, at least a portion of the protrusions 322 are disposed between two adjacent electrode contacts 21, and / or between two adjacent electrode solder joints 22, and / or between two adjacent conductive lines 23.

[0090] In some embodiments, the two adjacent conductive lines 23 include parallel and spaced conductor segments, and the protrusion 322 is disposed between the two parallel and spaced conductor segments. This helps to enhance the clamping of the flexible encapsulation layer 30 on the metal lead layer 20, while simplifying the fabrication process of the flexible skin electrode 100.

[0091] In some embodiments, the width of the protrusion 322 is equal to the distance between two adjacent conductive wires 23. Exemplarily, the protrusion 322 is a rectangular protrusion, the length of which is the distance between two adjacent metal leads in the metal lead layer 20. This can also be understood as the rectangular protrusion being embedded between two adjacent conductive wires 23. This allows two adjacent rectangular protrusions to hold the metal lead located within them, which helps to further improve the stability of the flexible skin electrode 100. When the flexible skin electrode 100 operates in the body for a long time, the rectangular protrusions absorb water and swell. The two adjacent rectangular protrusions can then hold the metal conductive wire 23 located in the middle, which helps to prevent the metal lead layer 20 from detaching.

[0092] In some embodiments, the extending direction of the protrusion 322 is the same as the extending direction of the conductive line 23. For example, the protrusion 322 is a rectangular protrusion, and the extending direction of the rectangular protrusion is the same as the extending direction of the conductive line 23. This helps to increase the contact area between the rectangular protrusion and the conductive line 23, further preventing the metal lead layer 20 from detaching.

[0093] In some embodiments, the width of the protrusion 322 is equal to the distance between two adjacent conductive lines 23. Exemplarily, the protrusion 322 is a rectangular protrusion, the length of the shorter side of which is equal to the thickness of the metal leads in the metal lead layer 20. This allows two adjacent rectangular protrusions to clamp the metal leads located within them, and makes the interface layer between the flexible encapsulation layer 30 and the flexible support layer 10 more tightly bonded, which is beneficial for improving the bonding force between the flexible encapsulation layer 30 and the flexible support layer 10.

[0094] Correspondingly, the side profile of the trapezoidal bump can be straight or curved, without limitation. Further, the curved shape can be an externally concave curve, an internally concave curve, or an S-curve formed by alternating externally and internally concave curves once or multiple times. It should be noted that if the side profile of the trapezoidal bump is curved, the angle θ between the tangent at any point on the side profile of the trapezoidal bump and the plane containing the flexible support layer 10 ranges from 0° to 90°. It should also be noted that, under the same etching aspect ratio, an S-shaped curved side profile is beneficial for further improving the bonding force between the flexible support layer 10 and the flexible encapsulation layer 30.

[0095] In some embodiments, this application provides a method for preparing the aforementioned flexible skin electrode structure. Please refer to... Figures 8-17 As shown, the preparation method includes the following steps:

[0096] A flexible support layer 10 and a metal lead layer 20 are provided in a stacked configuration; wherein...

[0097] The flexible support layer 10 is formed on the substrate surface, and the flexible support layer 10 is configured to be heated to 180℃-220℃ in a first step, during which the flexible support layer 10 is not completely cured.

[0098] A metal lead layer 20 is formed by depositing a metal material on the flexible support layer 10;

[0099] A flexible encapsulation layer 30 is applied to the flexible support layer 10 and the metal lead layer 20 to obtain the flexible skin electrode; wherein...

[0100] The flexible support layer 10 and the flexible encapsulation layer 30 are subjected to a second step heating to 300℃-400℃, and both the flexible support layer 10 and the flexible encapsulation layer 30 are completely cured.

[0101] It is particularly emphasized that by allowing the flexible support layer 10 to not fully solidify during the fabrication of the flexible skin electrode 100, and then covering the incompletely solidified flexible support layer 10 and metal lead layer 20 with a flexible encapsulation layer 30, and by configuring the flexible support layer 10 and the flexible encapsulation layer 30 to undergo a second step temperature increase to 300℃-400℃, both the flexible support layer 10 and the flexible encapsulation layer 30 are fully solidified. This allows the flexible support layer 10 and the flexible encapsulation layer 30 to undergo a cross-linking reaction at the interface, which is beneficial to improving the bonding force between the flexible support layer 10 and the flexible encapsulation layer 30, and also better forming a clamping effect on the metal lead layer 20, thereby improving the stability of the flexible skin electrode.

[0102] In some embodiments, this application provides a method for preparing the aforementioned flexible skin electrode structure. Please refer to... Figures 8-17 As shown, the preparation method includes the following steps:

[0103] S10 provides a flexible support layer 10 and a metal lead layer 20 stacked together; a metal material is deposited on the flexible support layer 10 to form the metal lead layer 20;

[0104] The area of ​​the flexible support layer 10 covered by the metal lead layer 20 is a first region; the area of ​​the flexible support layer 10 not covered by the metal lead layer 20 is a second region; and the flexible support layer 10 has a first fitting portion 11 in the second region.

[0105] S20 A flexible encapsulation layer 30 is disposed on the flexible support layer 10 and the metal lead layer 20 to obtain the flexible skin electrode 100;

[0106] The flexible encapsulation layer 30 is provided with a second fitting portion 32 that is adapted to the first fitting portion 11, and the flexible support layer 10 and the flexible encapsulation layer 30 are connected by fitting the first fitting portion 11 and the second fitting portion 32.

[0107] In this application, a first fitting portion 11 is provided on the flexible support layer 10, and a second fitting portion 32 adapted to the first fitting portion 11 is provided on the flexible encapsulation layer 30. The flexible support layer 10 and the flexible encapsulation layer 30 are fitted together through the first fitting portion 11 and the second fitting portion 32, thereby increasing the connection area between the flexible support layer 10 and the flexible encapsulation layer 30, and thus increasing the bonding force between the flexible support layer 10 and the flexible encapsulation layer 30. This also better forms a clamping effect on the metal lead layer 20, which is beneficial to improving the stability of the flexible skin electrode 100.

[0108] Furthermore, the first interlocking portion 11 in this application is disposed in the second region not covered by the metal lead layer 20, thereby avoiding interference between the first interlocking portion 11 and the metal lead layer 20, which helps to simplify the fabrication process of the flexible skin electrode 100.

[0109] Meanwhile, when the flexible skin 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 expand. After the flexible support layer 10 and the flexible encapsulation layer 30 are squeezed against each other, the interlayer friction between the two is increased, forming a mutual lock that makes it less likely to delaminate. This is beneficial to further improve the stability of the flexible skin electrode 100, thereby increasing the service life of the flexible skin electrode 100.

[0110] In some embodiments, a flexible support layer 10 and a metal lead layer 20 are provided in a stacked configuration, and the step of depositing a metal material on the flexible support layer 10 to form the metal lead layer 20 includes:

[0111] S11 provides a substrate 200.

[0112] For example, combined Figure 9 As shown, the substrate 200 is generally a horizontal plate-like structure. For example, the material of the substrate 200 includes any one of silicon nitride, silicon, or 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 heated immersion in a cleaning solution.

[0113] In some instances, the cleaning solution includes acetone, isopropanol, ethanol, and deionized water.

[0114] In some instances, the cleaning solution includes a mixture of concentrated sulfuric acid and hydrogen peroxide, a hydrofluoric acid solution, a mixture of ammonia and hydrogen peroxide, and a mixture of concentrated hydrochloric acid and hydrogen peroxide.

[0115] S12 forms a flexible support layer 10 on the surface of the substrate 200.

[0116] In some instances, combined Figure 10 As shown, the flexible support layer 10 is selected from one of PI (polyimide), Parylene-C, SU-8 or PDMS materials, and its thickness ranges from 5μm to 1000μm.

[0117] For example, the flexible support layer 10 is a polyimide layer, which can be formed by coating a polyimide precursor solution onto a substrate 200, removing the solvent, and heating to imidize the polyimide precursor solution. The coating method can be spin coating, spray coating, blade coating, or chemical vapor deposition.

[0118] Optionally, the flexible support layer 10 is a polyimide layer.

[0119] The steps for preparing the flexible support layer 10 include:

[0120] The flexible support layer 10 is made of PI. After its precursor liquid is spin-coated onto the surface of the substrate 200 at a speed of 500 to 5000 revolutions per second, the flexible support layer 10 is obtained by first step heating to 180℃-220℃ and then incompletely curing. That is, the flexible support layer 10 is subjected to incomplete curing treatment.

[0121] It is emphasized that the flexible support layer 10 is not completely cured at a lower temperature, which on the one hand prevents it from being dissolved and damaged by acetone, N-methylpyrrolidone (NMP) or photoresist developer in subsequent process steps, and on the other hand maintains sufficient surface activity, thereby enabling a stronger connection with the subsequent flexible encapsulation layer 30.

[0122] It is particularly important to emphasize that during the preparation of the flexible support layer 10, the heating and curing process is carried out in stages. After the first step heating to 180-220℃, the PI of the flexible support layer 10 is imidized and becomes amorphous. At this time, the PI of the flexible support layer 10 retains more active functional groups.

[0123] Specifically, the substrate 200 is pre-baked at a temperature of 110-150℃. After baking, once the substrate 200 has cooled to room temperature, a polyimide precursor solution is spin-coated. The viscosity of the polyimide precursor solution at 25℃ is 500-13000 mPa·s. The spin-coated polyimide precursor solution is then baked, with the initial oven temperature below 100℃, starting from 80℃. After pre-baking for 10 minutes, the temperature is increased at a rate of 1℃ / 2℃ per minute, reaching 120-140℃ and holding for 30 minutes (the temperature can be within this range, including 120℃ and 140℃). The temperature is then increased again at a rate of 1℃ / 2℃ per minute, reaching 180℃-220℃ and holding for 60 minutes (the temperature can be within this range, including 180℃ and 220℃). Finally, the temperature is decreased at a rate not exceeding 4℃ per minute until it reaches room temperature. Thus, in the step of preparing the flexible support layer 10, the precursor liquid raw material for preparing the polyimide layer is partially cured at a lower temperature.

[0124] S13 deposits a metallic material on the first region of the flexible support layer 10 to form a metallic lead layer 20.

[0125] In some embodiments, combined with Figures 1-3 and Figure 11 As shown, the metal lead layer 20 comprises three parts: an electrode contact area 24, an electrode solder joint area 25, and a multi-channel connecting wire area. The electrode contact area 24 includes multiple electrode contacts 21, which can be circular, rectangular, or other geometric shapes, without limitation. Similarly, the electrode solder joint area 25 includes multiple electrode solder joints 22, which can be circular, rectangular, or other geometric shapes, without limitation. The multi-channel connecting wire area includes multiple non-intersecting metal leads (i.e., conductive lines 23), each metal lead connecting to one electrode contact 21 and one electrode solder joint 22 at each end, forming a conductive path.

[0126] In some embodiments, multiple electrode contacts 21, multiple electrode solder joints 22, and multiple conductive lines 23 are integrally fabricated and formed simultaneously. Further, the multiple electrode contacts 21, multiple electrode solder joints 22, and multiple conductive lines 23 are made of identical materials, including one or more of titanium, chromium, silicon carbide, gold, or platinum, and the thickness of the metal lead layer 20 prepared from each material ranges from 5 to 500 nm.

[0127] In some embodiments, the metal lead layer 20 comprises one or more composite metal films, which are deposited from one or more composite metal films. Optionally, the metal lead layer 20 comprises multiple composite metal films, wherein the bottom layer of the multiple composite metal films comprises one or more of titanium, chromium, or silicon carbide, and the thickness of the bottom layer of the multiple composite metal films ranges from 5 to 20 nm. In the multiple composite metal films, the intermediate layer comprises one or more of gold or platinum, and the thickness of the intermediate layer ranges from 50 to 200 nm. In the multiple composite metal films, 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.

[0128] In some embodiments, the deposition method of the metal lead layer 20 includes at least one of magnetron sputtering, electron beam evaporation, or ion beam deposition.

[0129] In some embodiments, the formation of the plurality of electrode contacts 21, the plurality of electrode solder joints 22, and the plurality of conductive lines 23 on the metal lead layer 20 includes at least one of a metal lift-off process, a dry etching process, or a wet etching process.

[0130] In some embodiments, a photoresist layer (not shown) may be coated on the flexible support layer 10, and the photoresist layer may be patterned after photolithography and development. The areas on the flexible support layer 10 not covered by the patterned photoresist layer correspond to the areas where the metal lead layer 20 of the flexible skin electrode 100 is located.

[0131] In some embodiments, after photoresist is applied to the flexible support layer 10, the upper surface of the flexible support layer 10 covered with photoresist can be subjected to plasma treatment. Plasma treatment of the upper surface of the flexible support layer 10 helps to increase the roughness of the upper surface of the flexible support layer 10, while removing surface impurities and increasing the adhesion between the subsequently deposited metal and the upper surface of the flexible support layer 10.

[0132] For example, in some embodiments, the step of depositing a metallic material on the flexible support layer 10 to form the metal lead layer 20 may include:

[0133] Step (1): After preparing the flexible support layer 10 and before preparing the metal lead layer 20, the surface of the flexible support layer 10 is treated with oxygen plasma or a mixed plasma of oxygen and argon.

[0134] Step (2) involves preparing one or more thin films of titanium, chromium, silicon carbide, gold, or platinum by magnetron sputtering;

[0135] Step (3): Spin-coat positive photoresist onto the surface of the magnetron sputtered thin film, and after exposure and development, form the photoresist into the shape of metal leads;

[0136] Step (4): The metal lead shape of the photoresist layer 300 is transferred to the magnetron sputtering film layer by dry etching or wet etching process to form the final metal lead layer 20.

[0137] Step (5): Remove the photoresist.

[0138] In these embodiments, treating the surface of the flexible support layer 10 with plasma can increase the surface roughness and surface activity of the flexible support layer 10, which is beneficial to improving the bonding force between the metal lead layer 20 and the flexible support layer 10. Furthermore, fabricating the metal lead layer 20 using a magnetron sputtering process is beneficial to further improve the bonding force between the flexible support layer 10 and the metal lead layer 20.

[0139] Alternatively, in some embodiments, the step of depositing a metal material on the flexible support layer 10 to form the metal lead layer 20 may include:

[0140] Step (1): After preparing the flexible support layer 10, spin-coat a negative photoresist onto its surface, expose and develop it to reveal the metal lead shape area;

[0141] Step (2) involves treating the exposed area of ​​the photoresist with oxygen plasma or a mixed plasma of oxygen and argon.

[0142] Step (3) involves preparing one or more thin films of titanium, chromium, silicon carbide, gold, or platinum by electron beam evaporation;

[0143] Step (4) involves removing the photoresist using a lift-off process to form the final metal lead layer 20.

[0144] It should be noted that in some embodiments, the materials used to prepare the electrode contacts 21, electrode solder joints 22, and conductive wires 23 may be the same or different.

[0145] In some embodiments, the materials used to fabricate the electrode contacts 21, electrode solder joints 22, and conductive wires 23 are the same, and the metal lead layer 20 may consist of only one metal layer, which can be fabricated in a single thin-film deposition process. For example, if the materials used to fabricate the electrode contacts 21, electrode solder joints 22, and conductive wires 23 are all a 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 includes a metal layer on the photoresist and a metal lead layer 20 on the flexible support layer 10. The first metal layer may include at least one of gold, aluminum, tungsten, platinum, and titanium. Taking platinum as an example, platinum material is deposited on the flexible support layer 10 to form a platinum metal layer on the flexible support layer 10.

[0146] The platinum metal layer includes a platinum metal layer on the photoresist and a metal lead layer 20 on the flexible support layer 10. The platinum metal layer on the photoresist will eventually be removed along with the photoresist to obtain the platinum metal layer of the flexible support layer 10, namely the metal lead layer 20.

[0147] For example, the first metal material may include platinum and gold (e.g., a platinum layer is grown first, followed by a gold layer). Accordingly, the first metal layer includes a platinum layer and a gold layer stacked together, thereby forming a first metal layer on the flexible support layer 10. The first metal layer includes a first metal layer located on the photoresist and a metal lead layer 20 on the flexible support layer 10. That is, the first metal layer refers to a metal layer prepared by a single thin film deposition process. Further optionally, in a single thin film deposition process, one metal material may be deposited or multiple metal materials may be deposited sequentially to form a metal layer.

[0148] In other embodiments, the materials used to fabricate the electrode contacts 21 and the electrode solder joints 22 are different. Accordingly, the metal lead layer 20 includes at least a first metal layer and a second metal layer; that is, the metal lead layer 20 comprises multiple metal layers. In these embodiments, the fabrication of the metal lead layer 20 requires multiple photolithography and metal deposition processes to obtain the metal lead layer 20 with multiple metal layers.

[0149] Specifically, a first metal layer is deposited on the flexible support layer 10, covering the areas corresponding to the electrode contacts 21 and conductive lines 23 on the flexible support layer 10. Then, the photoresist and the metal layer on the photoresist are removed. Photoresist is then applied to the flexible support layer 10 and the first metal layer, covering the portion of the flexible support layer 10 except for the electrode solder joints 22 and conductive lines 23. A second metal layer is then deposited on the flexible support layer 10, covering the areas corresponding to the electrode solder joints 22 and conductive lines 23 on the flexible support layer 10.

[0150] The following explanation uses platinum as the material for preparing electrode contact 21 and gold as the material for preparing electrode solder joint 22, with platinum material deposited first and then gold material deposited as an example.

[0151] Specifically, a platinum metal layer is formed by depositing platinum material on the flexible support layer 10. This 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 this first electrode layer is not the metal lead layer 20 in the flexible skin electrode 100. The first electrode layer only includes electrode contacts 21 and conductive lines 23 (the area on the flexible support layer 10 corresponding to the electrode solder joints 22 is covered by photoresist, and the first electrode layer does not cover the electrode solder joints 22). That is, the first electrode layer only covers the area on the flexible support layer 10 corresponding to the electrode contacts 21 and conductive lines 23. Then, the photoresist is removed, exposing the portion of the flexible support layer 10 not covered by the first electrode layer. The photoresist coating process is repeated, and then a patterned photoresist layer is prepared again on the flexible support layer 10. The patterned photoresist layer covers the surface of the flexible support layer 10 except for the areas corresponding to the electrode solder joints 22 and the conductive lines 23. Then, gold material is deposited to form a gold material layer. The gold material layer includes a portion covering the patterned photoresist layer and a second metal layer covering the flexible support layer 10. The second metal layer includes a portion covering the electrode solder joints 22 and the conductive lines 23. The first metal layer and the second metal layer together form the metal lead layer 20 in the flexible skin electrode 100.

[0152] It should be emphasized that the flexible skin electrode 100 employs a multi-film deposition process, so that each conductive line 23 prepared includes a first metal layer and a second metal layer.

[0153] It is understandable that during the entire manufacturing process of the flexible skin electrode 100, by setting a second metal layer to cover the first metal layer at the location of the conductive wire 23, each conductive wire 23 includes a first metal layer and a second metal layer stacked together. This prevents the conductive wire 23 from continuing to conduct even if the first metal layer or the second metal layer of the conductive wire 23 breaks, thus effectively improving the stability of the flexible skin electrode 100 product.

[0154] Meanwhile, the electrode layer in the flexible skin electrode 100 adopts a multi-film deposition process, which allows the exposed surfaces of the electrode contacts 21 and electrode solder joints 22 (i.e. the parts of the electrode contacts 21 and electrode solder joints 22 that are not covered by the encapsulation layer) to be made of different materials. This allows different materials to give full play to their respective advantages and further optimize the performance of the flexible skin electrode 100.

[0155] Furthermore, by first growing a Ti (titanium) layer on the platinum layer (i.e., the first metal layer) and then depositing a gold layer on the Ti layer during the process of depositing a gold layer on the platinum layer (i.e., the first metal layer), a rough edge is avoided at the location of the conductive line 23, which would affect the appearance of the product and, in severe cases, even cause the two adjacent conductive lines 23 to be connected.

[0156] In some embodiments, acetone or N-methylpyrrolidone can be used to peel off the photoresist using a heated water bath, and the metal layer on the photoresist is peeled off along with the photoresist. For example, the photoresist can be peeled off the product using N-methylpyrrolidone in a heated water bath at 90°C. After the photoresist is peeled off using acetone or N-methylpyrrolidone in a heated water bath, the electrode layer covering the flexible support layer 10 remains on the flexible support layer 10.

[0157] S14 forms a groove in the second region of the flexible support layer 10.

[0158] For example, please refer to Figure 12 The groove is a trapezoidal groove, located on the entire surface of the flexible support layer 10 not covered by the metal lead layer 20, thus forming an engaging recess. It should be noted that the groove can also be other shapes, such as spherical or columnar grooves, and is not limited here. Unless otherwise specified, the following explanation uses a trapezoidal groove as an example. The structure of the trapezoidal groove has been described in detail above and will not be repeated here.

[0159] In some embodiments, the trapezoidal groove is formed by further etching the flexible support layer 10 using a reactive ion etching (RIE) process. The RIE process forms the trapezoidal groove, which not only promotes the macroscopic integration of the flexible packaging layer 30 and the flexible support layer 10, but also introduces a series of oxygen-containing functional groups and increases surface roughness on the surface of the flexible support layer 10, further enhancing the microscopic bonding force between the two, and also better clamping the metal lead layer 20.

[0160] 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 trapezoidal groove has a cross-sectional shape that is larger at the top and smaller at the bottom, with a sidewall angle ranging from 0 to 90°, and a groove depth ranging from 1 μm to 10 μm, or 1 μm to 50 μm, or 1 μm to 100 μm.

[0161] In some embodiments, the side shape of the trapezoidal groove can be adjusted according to the RIE process parameters. The side shape of the trapezoidal groove has been specifically described above and will not be repeated here. In some instances, a straight side profile can be formed by keeping the etching gas, pressure, and power constant. In some instances, an outwardly concave side profile can be formed by keeping the etching gas and pressure constant and gradually decreasing the etching power. In some instances, an inwardly concave side profile can be formed by keeping the etching gas and pressure constant and gradually increasing the etching power. In some instances, an S-shaped side profile can be formed by keeping the etching gas and pressure constant, first gradually increasing (decreasing) the etching power, then gradually decreasing (increasing) the etching power, and repeating this once or multiple times. As mentioned above, it should be noted that, under the same etching depth-to-width ratio, the S-shaped curve side profile achieves a better effect on the adhesion enhancement emphasized in this application.

[0162] It should be noted that, to achieve optimal fit with the subsequent flexible encapsulation layer 30, a suitable groove size can be selected based on the actual etching aspect ratio, and the groove of this preset size can be obtained by adjusting the RIE process parameters. In some examples, while keeping the etching gas and pressure constant, the etching power is gradually increased (or decreased), and the included angle θ of the tangent on the side of the trapezoidal groove gradually increases (or decreases). The included angle θ of the tangent on the side of the trapezoidal groove is the angle between the tangent at each point on the side and the horizontal plane of the solid end of the flexible support layer 10, and the angle θ ranges from 0 to 90°.

[0163] Optionally, in some embodiments, a very thin layer of tackifier (not shown in the figure) can be spin-coated onto the surface of the flexible support layer 10 to further enhance the tight adhesion between the flexible support layer 10 and the flexible encapsulation layer 30.

[0164] In some embodiments, the step of forming a flexible encapsulation layer 30 on the flexible support layer 10 and the metal lead layer 20 includes:

[0165] S21 forms a flexible encapsulation layer 30 on the flexible support layer 10 and the metal lead layer 20 using a coating process.

[0166] In some embodiments, please refer to Figure 12 and Figure 13 A flexible encapsulation layer 30 is covered on the flexible support layer 10 and the metal lead layer 20, with the metal lead layer 20 encapsulated within the flexible encapsulation layer 30. The flexible encapsulation layer 30 is selected from PI, Parylene-C, SU-8, or PDMS, and is applied by spin coating, spraying, or chemical vapor deposition.

[0167] Optionally, in some embodiments of this application, the step of forming a flexible encapsulation layer 30 on the flexible support layer 10 and the metal lead layer 20 includes:

[0168] A polyimide precursor solution is coated on the flexible support layer 10 and the metal lead layer 20. The polyimide precursor solution on the flexible support layer 10 and the incompletely cured polyimide in the flexible support layer 10 are then subjected to a second step heating to 300℃-400℃ to prepare a flexible encapsulation layer 30. Both the flexible support layer 10 and the flexible encapsulation layer 30 are completely cured.

[0169] For example, the material used to prepare the flexible encapsulation layer 30 is PI, such as any one of PI2610, JA-902, P12611, PMR-15, AFR-PE-4, etc. The precursor liquid of the PI is applied to the surface of the flexible support layer 10 and the metal lead layer 20. Under the action of centrifugal force, the PI precursor liquid flows and fills the trapezoidal groove on the surface of the flexible support layer 10 and covers the metal lead layer 20. The flexible encapsulation layer 30 is completely cured by heating to form a reliable encapsulation with a thickness ranging from 5μm to 1000μm.

[0170] Specifically, the sample is pre-baked, cooled to room temperature, and then spin-coated with a polyimide precursor solution onto the flexible support layer 10 and the metal lead layer 20. The sample is baked to 80°C for 10 minutes. The temperature is then increased to 120°C-140°C at a rate of 1°C / 2°C per minute and held for 30 minutes. Finally, the temperature is increased to 180°C-220°C at a rate of 1°C / 2°C per minute and held for 60 minutes, so that the flexible encapsulation layer 30 forms an incompletely cured structure similar to that of the flexible support layer 10. Then, the temperature is increased to 300℃-400℃ at a rate not exceeding 3℃ per minute and held for 60 minutes. When the curing temperature is increased to 300℃ (e.g., held for 60 minutes) - 360℃ (e.g., held for 60 minutes) - 400℃ (e.g., held for 60 minutes), that is, the temperature is sequentially increased from 300℃ to 360℃, and then to 400℃, with each increase to the preset temperature followed by a 60-minute holding period, to fully imidize the polyimide on the flexible support layer 10 and the incompletely cured polyimide in the flexible support layer 10. This allows intermolecular bonds to form between the flexible support layer 10 and the flexible encapsulation layer 30, further increasing the bonding force between them. Finally, the temperature is reduced to room temperature at a rate not exceeding 4℃ per minute.

[0171] It should be emphasized that during the preparation of the flexible encapsulation layer 30, the raw materials for preparing the flexible encapsulation layer 30 are subjected to step-by-step heating and curing. This allows the incompletely cured raw materials in the flexible support layer 10 to undergo further curing and cross-linking reactions during the preparation of the flexible encapsulation layer 30. The resulting PI film has internal molecular chain flow, which promotes the filling and interlocking of the flexible encapsulation layer 30 with the trapezoidal grooves on the surface of the flexible support layer 10. This 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 electrode 100, thereby extending the service life of the flexible skin electrode 100.

[0172] Specifically, during the deposition process of the flexible encapsulation layer 30, it fills into the flexible support layer 10. After a heating and curing process, the flexible encapsulation layer 30 forms trapezoidal bumps downwards, i.e., engaging protrusions. The trapezoidal bumps and the trapezoidal grooves of the flexible support layer 10 are mutually adapted in shape, i.e., a stable interlocking connection is formed between the engaging grooves and the engaging protrusions. The trapezoidal bump area includes all areas on the lower surface of the flexible encapsulation layer 30 except for the area corresponding to the covering metal lead layer 20. The protrusion height of the trapezoidal bumps ranges from 1 to 100 μm, and the angle between the side profile and the horizontal plane ranges from 0 to 90°.

[0173] It should be noted that the trapezoidal bump is formed by the flow filling of the flexible encapsulation layer 30, so the shape of the trapezoidal bump and the aforementioned trapezoidal groove are complementary. That is, the trapezoidal bump is wider at the top and narrower at the bottom, and its sides can be straight, outwardly convex, inwardly convex, or S-shaped. The straight, inwardly convex, outwardly convex, and S-shaped shapes are characterized in that the angle θ between the tangent at any point on the line and the horizontal plane of the solid end of the flexible encapsulation layer 30 ranges from 0 to 90°.

[0174] In some embodiments, after fabricating the flexible encapsulation layer 30, the fabrication method further includes:

[0175] S22 has an opening in the flexible encapsulation layer 30. Please refer to [link / reference]. Figure 14 This exposes the electrode contact area 24 and the electrode solder joint area 25.

[0176] In some instances, the thickness of the flexible packaging layer 30 does not exceed 10 μm, and when the etching rate ratio of the material of the flexible packaging layer 30 to the photoresist in oxygen plasma is close to 1:1 or higher, a thick photoresist can be directly used as an etching barrier layer, reducing process cost and process complexity.

[0177] The specific implementation process is as follows:

[0178] Step (1) Spin-coating a suitable thickness of photoresist onto the surface of the flexible packaging layer 30, and performing photolithography, development, hardening, and other steps in sequence to form a photoresist pattern, that is, there is no photoresist in the electrode contact area 24 and the electrode solder joint area 25, while there is photoresist in the rest of the area; Step (2) Etching the flexible packaging layer 30 down to the metal lead layer 20 by introducing O2 or a mixture of O2+CF4 or O2+CF4+Ar through a reactive ion etching process; Step (3) Removing the photoresist barrier layer by dry or wet method.

[0179] In some instances, when the thickness of the flexible packaging layer 30 exceeds 10 μm, or when the material-to-photoresist ratio of the flexible packaging layer 30 is much less than 1:1, an additional etching hard mask layer needs to be fabricated. The etching hard mask material is one of silicon dioxide, silicon nitride, aluminum, or chromium. The etching hard mask is fabricated using a lift-off process or an etching process.

[0180] The specific implementation process is as follows:

[0181] Step (1) Deposit one of the etching hard mask materials such as silicon dioxide, silicon nitride, aluminum, or chromium on the surface of the flexible packaging layer 30; Step (2) Spin coat photoresist on the surface of the etching hard mask layer, and perform photolithography, development, hardening and other steps in one go to form a photoresist pattern, that is, there is no photoresist in the electrode contact area 24 and the electrode solder joint area 25, while there is photoresist in the rest of the area; Step (3) Transfer the photoresist pattern to the surface of the etching hard mask material by wet or dry etching process, and remove the photoresist; Step (4) Etch the flexible packaging layer 30 down to the metal lead layer 20 by introducing O2 or a mixture of O2+CF4 or O2+CF4+Ar by reactive ion etching process; Step (5) Remove the etching hard mask material layer.

[0182] Another specific implementation process is as follows:

[0183] Step (1) Photolithography is performed on the flexible packaging layer 30 to form a photoresist pattern. Specifically, the photoresist pattern is formed in the electrode contact area 24 and the electrode solder joint area 25, while the rest of the area is free of photoresist. Step (2) Etching hard mask materials such as silicon dioxide, silicon nitride, chromium, or aluminum are deposited on the photoresist pattern. Step (3) Plasma etching hard mask layer is formed by lift-off process. Step (4) O2 or a mixture of O2+CF4 or O2+CF4+Ar is introduced by reactive ion etching process to etch the flexible packaging layer 30 down to the metal lead layer 20. Step (5) The etching hard mask material layer is removed.

[0184] In some embodiments, after the step of creating an opening in the flexible encapsulation layer 30, the fabrication method further includes:

[0185] S23 covers the exposed electrode contact 21 with an electrode modification layer 40, for details please refer to Figure 15 .

[0186] For example, the electrode modification layer 40 is a single or multi-layer composite structure, which helps to reduce the surface impedance of the electrode, improve the signal-to-noise ratio of nerve signal acquisition, and increase the charge injection capability during the nerve stimulation phase.

[0187] 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 deposition process of the electrode modification layer 40 includes electron beam evaporation, magnetron sputtering, and electrodeposition. The patterning process of the electrode modification layer 40 includes etching and lift-off processes. It is understood that the electrode modification layer 40 deposits metal on the electrode contacts 21 of the flexible cortical electrode 100, thereby adding a metal layer to the electrode contacts 21. This makes the electrode contacts 21 flush with or higher than the flexible encapsulation layer 30, making the flexible cortical electrode 100 more conducive to the acquisition of neural signals, thereby improving the signal-to-noise ratio of neural signal acquisition and electrode biocompatibility.

[0188] In some examples, photolithography is performed on the flexible encapsulation layer 30 to expose the electrode contacts 21 and their 5-50 μm outward extension regions. Then, titanium / platinum metal layers are deposited by electron beam evaporation, and patterning is achieved through a lift-off process. Finally, porous platinum is deposited on the patterned surface using an electrodeposition process to achieve electrode modification. Of course, in other embodiments of this application, at least one of porous gold, PEDOT, or a PEDOT / CNTs composite layer can also be deposited on the patterned surface using an electrodeposition process to achieve electrode modification.

[0189] In some embodiments, photolithography is performed on the flexible encapsulation layer 30 to expose the electrode contacts 21 and their 5-50 μm outward extension regions. Subsequently, titanium / iridium oxide is deposited by magnetron sputtering, and electrode modification is achieved through a lift-off process.

[0190] In some embodiments, the preparation method further includes:

[0191] S24 etches the contact area 24 of the flexible skin electrode 100 to create a through hole 50.

[0192] Combination Figure 1 and Figure 16As shown. Silicon dioxide, metallic chromium, or metallic aluminum, or other plasma-resistant etching-resistant materials, are deposited on the flexible encapsulation layer 30 as an etching mask layer. The etching mask layer is patterned using etching or lift-off processes. Reactive ion etching is used to create through-holes 50 in the electrode contact region 24 of the flexible cortical electrode 100 where there are no electrode contacts 21. The etching depth of the through-holes 50 is the sum of the thickness of the flexible encapsulation layer 30 and the shape of the through-holes 50 can be circular, rectangular, triangular, or various irregular shapes. The through-holes 50 are distributed in the electrode contact region 24, more specifically, between electrode contacts 21. By forming several through-holes 50 in the electrode contact region 24 of the flexible cortical electrode 100, it helps to better maintain a good brain environment and increases the overall flexibility of the flexible cortical electrode 100, allowing for good adhesion with brain tissue. Meanwhile, the open-hole design of the electrode contact area 24 can promote the flow of cerebrospinal fluid, which helps maintain brain health, promotes brain cleanliness and normal function, thereby reducing the abnormal deposition and accumulation of harmful proteins and reducing the risk of other brain diseases.

[0193] In some embodiments, the preparation method further includes:

[0194] S25 etches an electrode release trench (not shown) in the outer region of the electrode edge.

[0195] The electrode release trench is a region extending 50-500 μm outward from the electrode edge, with a structure similar to that of the perforated hole 50. Its purpose is to facilitate the overall release of the flexible skin electrode 100 from the substrate 200. Both the electrode release trench and the partial perforated hole 50 are formed by etching through the flexible encapsulation layer 30 and the flexible support layer 10 using reactive ion etching.

[0196] The specific implementation process is as follows:

[0197] Step (1) Photolithography is performed on the flexible packaging layer 30 to form the shape of electrode release trenches and hollow holes 50; Step (2) Etching masking layer material such as silicon dioxide, silicon nitride, chromium or aluminum is deposited; Step (3) The etching masking layer is patterned by lift-off process; Step (4) The flexible packaging layer 30 and flexible support layer 10 are etched through by reactive ion etching in the area of ​​electrode release trenches and hollow holes 50; Step (5) The etching masking layer is removed.

[0198] In some embodiments, the preparation method further includes:

[0199] S26 The flexible support layer 10 is peeled off from the silicon substrate 200, releasing the flexible skin electrode 100, as follows: Figure 17 As shown.

[0200] Optionally, in some embodiments, a sacrificial layer is provided between the silicon substrate 200 and the flexible support layer 10, and the silicon substrate 200 with the sacrificial layer is placed in an acidic or alkaline solution, so that the flexible support layer 10 is released from the silicon substrate 200 by reacting the sacrificial layer with the acidic or alkaline solution.

[0201] The technical solutions provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope, and the technical features of different embodiments can be freely combined. Therefore, the content of this specification should not be construed as a limitation of this 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 is 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; 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 and the flexible encapsulation layer form a clamping on the metal lead layer; The first fitting part is a groove, the second fitting part is a protrusion, the protrusion comprises the 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; The flexible encapsulation layer comprises an encapsulation body layer and the protrusion arranged on the side of the encapsulation body layer facing the flexible support layer, the protrusion comprises a protruding part embedded in the groove and the protrusion and the encapsulation body layer are connected by the protrusion.

2. The flexible skin layer electrode according to claim 1, wherein The number of the first fitting parts is a plurality, and the plurality of first fitting parts are arranged in the second area.

3. The flexible skin electrode of claim 1, wherein, The vertical cross section of the groove is at least one of trapezoidal, circular arc, zigzag and square; And / or, the depth of the groove ranges from 0.1 μm to 50 μm.

4. The flexible skin electrode of claim 3, 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 alternately combining the outward concave curve and the inward concave curve one or more times.

5. The flexible skin electrode of claim 1, 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 protrusion and the encapsulation body layer are an integral structure.

6. The flexible skin electrode of claim 5, 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.

7. A method of making the flexible skin electrode of any one of claims 1-6, 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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