Method for preparing electrode, electrode, method for preparing flexible electrode, flexible electrode and electrode array

Abstract

The invention provides a method for preparing an electrode, the electrode, a method for preparing a flexible electrode, the flexible electrode and an electrode array. A method of preparing an electrode includes: providing an insulating layer including a carbonizable material; positioning a focus of a laser beam inside the insulating layer, the laser beam configured to have a light intensity higher than a multi-photon absorption threshold of the carbonizable material in a focus region and a light intensity lower than the multi-photon absorption threshold of the carbonizable material in a non-focus region; and enabling the focal point of the laser beam to scan along a path located in the insulating layer, enabling the carbonizable material of the insulating layer on the path to generate multi-photon absorption under the irradiation of the laser beam so as to be carbonized, thereby forming a conductive circuit located in the insulating layer.

Description

Technical Field

[0001] This disclosure relates to the field of brain-computer interface technology, and more specifically, to a method for preparing an electrode, an electrode, a method for preparing a flexible electrode, a flexible electrode, and an electrode array. Background Technology

[0002] Electrodes, as the key interface connecting neural tissue to external devices, have always been a research focus in the field of brain-computer interface technology. Early methods primarily used rigid electrodes, which can be formed from metals (such as platinum and iridium) and silicon-based materials. These electrodes offer advantages such as high mechanical strength and stable conductivity, but suffer from poor biocompatibility and cannot adapt to even minute displacements within neural tissue (such as fluctuations of tens to hundreds of micrometers caused by breathing and heartbeat), easily leading to electrode displacement failure and / or damage to surrounding tissues. In recent years, flexible electrodes have gradually emerged, offering superior biocompatibility and long-term stability compared to traditional rigid electrodes, and are less prone to scarring within neural tissue. Summary of the Invention

[0003] A brief overview of this disclosure is given below to provide a basic understanding of some aspects of it. However, it should be understood that this overview is not an exhaustive summary of this disclosure. It is not intended to identify key or essential parts of this disclosure, nor is it intended to limit the scope of this disclosure. Its purpose is merely to present certain concepts of this disclosure in a simplified form as a prelude to the more detailed description that follows.

[0004] According to a first aspect of this disclosure, a method for fabricating an electrode is provided, the method comprising: providing an insulating layer comprising a carbonizable material; focusing a laser beam within the insulating layer, the laser beam being configured to have an intensity in a focused region higher than a multiphoton absorption threshold of the carbonizable material and an intensity in a non-focused region lower than the multiphoton absorption threshold of the carbonizable material; and scanning the focus of the laser beam along a path located within the insulating layer, such that the carbonizable material of the insulating layer along the path undergoes multiphoton absorption and carbonization under the irradiation of the laser beam, thereby forming a conductive circuit located within the insulating layer.

[0005] In some embodiments, the conductive line is a first conductive line, and the method further includes: forming a second conductive line in the insulating layer, the second conductive line being configured to extend at one end to the surface of the insulating layer to provide an electrode site, and at the other end to be connected to the first conductive line.

[0006] In some embodiments, the path is a first path, and the second conductive line is formed by scanning the focal point of the laser beam along a second path extending between the surface of the insulating layer and the first conductive line.

[0007] In some embodiments, the second conductive line is formed by depositing a conductive medium in a trench extending from the surface of the insulating layer to the first conductive line.

[0008] In some embodiments, the second conductive line is formed by a through-hole extending from the surface of the insulating layer to the first conductive line, the through-hole being capable of receiving a conductive medium therein to form the second conductive line.

[0009] In some embodiments, the method further includes forming a conductive plating layer over the electrode sites.

[0010] In some embodiments, when the focal point of the laser beam is scanned along the path, the focused spot of the laser beam at the scanned position on the path partially overlaps with the focused spot of the laser beam at the adjacent scanned position on the path.

[0011] In some embodiments, the path is a first path, and the method further includes: scanning the focal point of the laser beam along a third path located inside the insulating layer, such that the carbonizable material of the insulating layer on the third path undergoes multiphoton absorption and carbonization under the irradiation of the laser beam.

[0012] In some embodiments, the third path extends alongside the first path, and when the focus of the laser beam is scanned along the third path, the focused spot of the laser beam at the scanning position on the third path partially overlaps with the focused spot of the laser beam at the corresponding scanning position on the first path.

[0013] In some embodiments, the first path and the third path are located at different depths within the insulating layer.

[0014] In some embodiments, the first path and the third path are located at the same depth within the insulating layer and are spaced apart from each other.

[0015] In some embodiments, the path is a first path, the insulating layer is formed on a substrate, and the method further includes: positioning the focus of the laser beam on the lower surface of the insulating layer facing the substrate, and scanning the focus of the laser beam along a fourth path located on the lower surface, such that the carbonizable material of the insulating layer on the fourth path undergoes multiphoton absorption and carbonization under the irradiation of the laser beam; and separating the insulating layer, in which the conductive lines are formed and whose lower surface is at least partially carbonized, from the substrate.

[0016] In some embodiments, the laser beam is configured such that the carbonizable material has a transmittance of not less than 50% at the wavelength of the laser beam.

[0017] In some embodiments, the laser beam is configured to enable the carbonizable material to undergo two-photon absorption. In some embodiments, the laser beam is configured to enable the carbonizable material to undergo three-photon absorption.

[0018] In some embodiments, the wavelength of the laser beam is in the near-infrared band. In some embodiments, the wavelength of the laser beam is between 780 nanometers and 1064 nanometers.

[0019] In some embodiments, the focused spot of the laser beam has a diameter on the order of submicron to micron.

[0020] In some embodiments, the laser beam is configured to be focused by a lens with a numerical aperture between 0.8 and 1.4.

[0021] In some embodiments, the scanning speed is between 10 micrometers per second and 100 micrometers per second.

[0022] In some embodiments, the scan is performed 1 to 3 times along the path.

[0023] In some embodiments, the laser beam is configured as a femtosecond laser beam provided in pulsed form. In some embodiments, the pulse width of the femtosecond laser beam is between 50 femtoseconds and 200 femtoseconds. In some embodiments, the repetition frequency of the femtosecond laser beam is between 100 kHz and 1 MHz. In some embodiments, the single-pulse energy of the femtosecond laser beam is between 1 microjoule and 10 microjoules.

[0024] In some embodiments, the carbonizable material includes at least one of the following: polyimide, polylactic acid-glycolic acid copolymer, cellulose, chitosan, hyaluronic acid, collagen, gelatin, sodium alginate, polyurethane, polytetrafluoroethylene, expanded polytetrafluoroethylene, polylactic acid, L-polylactic acid, D-polylactic acid, polyglycolic acid, polycaprolactone, polyamide, polyterephthalic acid, ethylene glycol, polyether block polyamide, high-density polyethylene, thermoplastic polyurethane elastomer, polydimethylsiloxane, poly(p-xylene), epoxy resin, polyamide-imide, polylactic acid, polyterephthalate, SU8 photoresist, silicone, and silicone rubber.

[0025] According to a second aspect of this disclosure, a method for fabricating an electrode is provided, the method comprising: providing a first insulating layer comprising a first carbonizable material; focusing a first laser beam on an upper surface of the first insulating layer, the first laser beam being configured to have an intensity in a focused region higher than a first multiphoton absorption threshold of the first carbonizable material and an intensity in a non-focused region lower than the first multiphoton absorption threshold of the first carbonizable material; scanning the focus of the first laser beam along a path located on the upper surface of the first insulating layer, such that the first carbonizable material of the first insulating layer on the path undergoes multiphoton absorption and carbonization under the irradiation of the first laser beam, thereby forming a conductive line on the upper surface of the first insulating layer; and forming a second insulating layer on the first insulating layer on which the conductive line is formed.

[0026] In some embodiments, the method further includes: forming a metal layer on the first insulating layer on which the conductive lines are formed on the upper surface, prior to forming the second insulating layer, the metal layer being patterned to cover the conductive lines.

[0027] In some embodiments, the method further includes: subjecting the upper surface of the first insulating layer to plasma treatment prior to forming the metal layer.

[0028] In some embodiments, the method further includes one or more of the following: forming a functionalized molecular film on the upper surface of the first insulating layer before forming the second insulating layer, so that the first insulating layer and the second insulating layer are bonded together by the chemical bonding of the functionalized molecular film after the formation of the second insulating layer; or applying a photocurable adhesive to the upper surface of the first insulating layer before forming the second insulating layer, so that the first insulating layer and the second insulating layer are bonded together by curing the photocurable adhesive by ultraviolet light after the formation of the second insulating layer; or bonding the first insulating layer and the second insulating layer together by thermocompression bonding or ultrasonic welding after the formation of the second insulating layer.

[0029] In some embodiments, the conductive line is a first conductive line, and the method further includes: forming a second conductive line in the second insulating layer, the second conductive line being configured to extend at one end to the upper surface of the second insulating layer to provide an electrode site, and to be connected at the other end to the first conductive line.

[0030] In some embodiments, the path is a first path, and the second conductive line is formed by scanning the focus of a second laser beam along a second path extending between the upper surface of the second insulating layer and the first conductive line, the second insulating layer comprising a second carbideable material, the second laser beam being configured to have an intensity in the focused region higher than a second multiphoton absorption threshold of the second carbideable material, and an intensity in the unfocused region lower than the second multiphoton absorption threshold of the second carbideable material.

[0031] In some embodiments, the second conductive line is formed by depositing a conductive medium in a trench extending from the upper surface of the second insulating layer to the first conductive line.

[0032] In some embodiments, the second conductive line is formed by a through-hole extending from the upper surface of the second insulating layer to the first conductive line, the through-hole being capable of receiving a conductive medium therein to form the second conductive line.

[0033] In some embodiments, the method further includes forming a conductive plating layer over the electrode sites.

[0034] In some embodiments, the path is a first path, the conductive line is a first conductive line, and the method further includes: positioning the focus of the first laser beam inside the first insulating layer, and scanning the focus of the first laser beam along a third path located inside the first insulating layer, such that a first carbonizable material of the first insulating layer on the third path undergoes multiphoton absorption and carbonization under the irradiation of the first laser beam, thereby forming a third conductive line located inside the first insulating layer.

[0035] In some embodiments, the path is a first path, the conductive line is a first conductive line, the second insulating layer includes a second carbonizable material, and the method further includes: positioning the focus of a second laser beam inside the second insulating layer, the second laser beam being configured to have an intensity in the focused region higher than a second multiphoton absorption threshold of the second carbonizable material, and an intensity in the unfocused region lower than the second multiphoton absorption threshold of the second carbonizable material; scanning the focus of the second laser beam along a fourth path located inside the second insulating layer, such that the second carbonizable material of the second insulating layer on the fourth path undergoes multiphoton absorption and carbonization under the irradiation of the second laser beam, thereby forming a fourth conductive line located inside the second insulating layer.

[0036] In some embodiments, the path is a first path, the first insulating layer is formed on a substrate, and the method further includes: positioning the focus of the first laser beam on a lower surface of the first insulating layer facing the substrate, and scanning the focus of the first laser beam along a fifth path located on the lower surface, such that a first carbonizable material of the first insulating layer on the fifth path undergoes multiphoton absorption and carbonization under the irradiation of the first laser beam; and separating the stack of the first insulating layer, on which the conductive lines are formed on its upper surface and whose lower surface is at least partially carbonized, from the substrate.

[0037] In some embodiments, the first laser beam is configured such that the first carbideable material has a transmittance of not less than 50% at the wavelength of the first laser beam.

[0038] In some embodiments, the first laser beam is configured to enable the first carbideable material to undergo two-photon absorption. In some embodiments, the first laser beam is configured to enable the first carbideable material to undergo three-photon absorption.

[0039] In some embodiments, the wavelength of the first laser beam is in the near-infrared band. In some embodiments, the wavelength of the first laser beam is between 780 nanometers and 1064 nanometers.

[0040] In some embodiments, the focused spot of the first laser beam has a diameter on the order of submicron to micron.

[0041] In some embodiments, the first laser beam is configured to be focused by a lens with a numerical aperture between 0.8 and 1.4.

[0042] In some embodiments, the scanning speed is between 10 micrometers per second and 100 micrometers per second.

[0043] In some embodiments, the scan is performed 1 to 3 times along the path.

[0044] In some embodiments, the first laser beam is configured as a femtosecond laser beam provided in pulsed form. In some embodiments, the pulse width of the femtosecond laser beam is between 50 femtoseconds and 200 femtoseconds. In some embodiments, the repetition frequency of the femtosecond laser beam is between 100 kHz and 1 MHz. In some embodiments, the single-pulse energy of the femtosecond laser beam is between 1 microjoule and 10 microjoules.

[0045] In some embodiments, the first carbonizable material includes at least one of the following: polyimide, polylactic acid-glycolic acid copolymer, cellulose, chitosan, hyaluronic acid, collagen, gelatin, sodium alginate, polyurethane, polytetrafluoroethylene, expanded polytetrafluoroethylene, polylactic acid, L-polylactic acid, D-polylactic acid, polyglycolic acid, polycaprolactone, polyamide, polyterephthalic acid, ethylene glycol, polyether block polyamide, high-density polyethylene, thermoplastic polyurethane elastomer, polydimethylsiloxane, poly(p-xylene), epoxy resin, polyamide-imide, polylactic acid, polyterephthalate, SU8 photoresist, silicone, and silicone rubber.

[0046] According to a third aspect of this disclosure, an electrode is provided, the electrode comprising: an insulating layer comprising a carbonizable material; and a conductive line located within the insulating layer, the conductive line being formed by scanning a focal point of a laser beam along a path located within the insulating layer, such that the carbonizable material of the insulating layer on the path undergoes multiphoton absorption and carbonization under irradiation by the laser beam, the laser beam being configured to have an intensity in a focused region higher than the multiphoton absorption threshold of the carbonizable material, and an intensity in a non-focused region lower than the multiphoton absorption threshold of the carbonizable material.

[0047] In some embodiments, the electrode is prepared by the method described in any embodiment of the first or second aspect of this disclosure.

[0048] According to a fourth aspect of this disclosure, a method for fabricating a flexible electrode is provided, the method comprising: providing a polyimide layer; positioning a focal point of a near-infrared femtosecond pulsed laser beam within the polyimide layer, the near-infrared femtosecond pulsed laser beam being configured to have an intensity in a focused region higher than a two-photon absorption threshold of the polyimide and an intensity in a non-focused region lower than the two-photon absorption threshold of the polyimide; and scanning the focal point of the near-infrared femtosecond pulsed laser beam along a path located within the polyimide layer, such that the polyimide in the polyimide layer along the path undergoes two-photon absorption and carbonization under irradiation by the near-infrared femtosecond pulsed laser beam, thereby forming a conductive circuit located within the polyimide layer.

[0049] According to a fifth aspect of this disclosure, a flexible electrode is provided, the flexible electrode comprising: a polyimide layer; and a conductive line located within the polyimide layer, the conductive line being formed by scanning a focal point of a near-infrared femtosecond pulsed laser beam along a path located within the polyimide layer, such that the polyimide in the polyimide layer along the path undergoes two-photon absorption and carbonization under irradiation by the near-infrared femtosecond pulsed laser beam, the near-infrared femtosecond pulsed laser beam being configured to have an intensity higher than the two-photon absorption threshold of the polyimide in the focused region and an intensity lower than the two-photon absorption threshold of the polyimide in the non-focused region.

[0050] According to a sixth aspect of this disclosure, an electrode array is provided, the electrode array comprising a plurality of electrodes, each of the plurality of electrodes being an electrode according to any embodiment of a third aspect of this disclosure, or a flexible electrode according to a fifth aspect of this disclosure, or an electrode prepared by a method according to any embodiment of a first or second aspect of this disclosure, or a flexible electrode prepared by a method according to a fourth aspect of this disclosure. Attached Figure Description

[0051] The foregoing and other features and advantages of this disclosure will become clear from the following description of embodiments illustrated in conjunction with the accompanying drawings. The drawings, incorporated herein and forming a part of the specification, are further used to explain the principles of this disclosure and to enable those skilled in the art to make and use it.

[0052] Figure 1 This is a flowchart illustrating a method for preparing an electrode according to some embodiments of the present disclosure.

[0053] Figures 2 to 4 These are examples of its applications. Figure 1 The diagram illustrates the corresponding steps of the example process of the method shown.

[0054] Figure 5 This is a schematic diagram illustrating an example process in which a method for preparing an electrode according to some embodiments of the present disclosure is applied.

[0055] Figure 6 This is a schematic diagram illustrating the structure of an electrode according to some embodiments of the present disclosure.

[0056] Figure 7 This is a schematic diagram illustrating the structure of an electrode according to some embodiments of the present disclosure.

[0057] Figure 8 This is a schematic diagram illustrating the structure of an electrode according to some embodiments of the present disclosure.

[0058] Figure 9 This is a schematic diagram illustrating an example process in which a method for preparing an electrode according to some embodiments of the present disclosure is applied.

[0059] Figure 10 This is a schematic diagram illustrating the structure of an electrode according to some embodiments of the present disclosure.

[0060] Figure 11 This is a schematic diagram illustrating the structure of an electrode according to some embodiments of the present disclosure.

[0061] Figure 12 This is a schematic diagram illustrating an example process in which a method for preparing an electrode according to some embodiments of the present disclosure is applied.

[0062] Figure 13 This is a flowchart illustrating a method for preparing an electrode according to some embodiments of the present disclosure.

[0063] Figures 14 to 17 These are examples of its applications. Figure 13 The diagram illustrates the corresponding steps of the example process of the method shown.

[0064] Figure 18 This is a schematic diagram illustrating the structure of an electrode according to some embodiments of the present disclosure.

[0065] Figure 19 This is a schematic diagram illustrating the structure of an electrode according to some embodiments of the present disclosure.

[0066] Figure 20 This is a schematic diagram illustrating an example process in which a method for preparing an electrode according to some embodiments of the present disclosure is applied.

[0067] Figure 21 This is a flowchart illustrating a method for preparing a flexible electrode according to some embodiments of the present disclosure.

[0068] Figure 22 This is a focused ion beam (FIB) image of an example of a flexible electrode according to some embodiments of the present disclosure.

[0069] Note that in the embodiments described below, the same reference numerals are sometimes used across different figures to denote the same parts or parts having the same function, and repeated descriptions are omitted. In this specification, similar reference numerals and letters are used to denote similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0070] For ease of understanding, the positions, dimensions, and extents of the structures shown in the accompanying drawings and other materials may not represent actual positions, dimensions, and extents. Therefore, the disclosed invention is not limited to the positions, dimensions, and extents disclosed in the accompanying drawings and other materials. Furthermore, the drawings are not necessarily drawn to scale, and some features may be enlarged to show details of specific components. Detailed Implementation

[0071] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present disclosure.

[0072] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this disclosure or its application or use. Those skilled in the art will understand that they merely illustrate exemplary ways that can be used to implement this disclosure, and are not exhaustive.

[0073] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0074] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0075] For ease of description, the semi-finished or finished electrode in this paper can be referred to as a device.

[0076] In the field of brain-computer interface technology, electrodes can be fabricated using Micro-Electromechanical System (MEMS) technology. Taking silicon-based electrodes as an example, a silicon wafer can be used as a substrate, and a layer of silicon dioxide can be thermally grown on the substrate. Then, a metal layer (such as platinum, iridium, gold, etc.) is formed on the substrate through physical vapor deposition or chemical vapor deposition, and the metal layer is patterned into conductive lines through photolithography and etching processes. Next, an insulating layer (such as silicon dioxide, polyimide, etc.) is formed on the patterned metal layer to isolate the conductive lines. Such MEMS processes require multiple layers of different materials to be stacked and bonded together. The difference in thermal expansion coefficients of these different materials can easily cause the fabricated multilayer structure to delaminate due to thermal stress during high-temperature processes (e.g., bonding, deposition, etc.). In addition, multilayer processing requires multiple deposition, photolithography, and etching processes. Such a cumbersome process can easily lead to the accumulation of material damage layer by layer, resulting in poor structural stability.

[0077] This disclosure utilizes a spatially focused laser beam to precisely trigger multiphoton absorption of the carbonizable material at a desired location within an insulating layer through localized high light intensity. This carbonizes the carbonizable material at the desired location, transforming it in situ into a conductive circuit. Simultaneously, the carbonizable material at other locations remains intact, serving as an insulating layer to isolate the conductive circuit. Because this conductive circuit is directly derived from a portion of the insulating layer, it exhibits strong adhesion to the surrounding insulating layer. Furthermore, since their interfaces are not exposed to the outside environment, they are less susceptible to deterioration or failure due to environmental factors such as moisture and pollution. The method of this disclosure features a simple process, is easily compatible with advanced manufacturing processes such as micro / nano fabrication and 3D printing, and the prepared electrodes exhibit excellent stability.

[0078] Figure 1 A method 100 for preparing an electrode according to some embodiments of the present disclosure is shown. For example... Figure 1 As shown, method 100 includes: in step S102, providing an insulating layer comprising a carbonizable material; in step S104, positioning a laser beam focal point inside the insulating layer, the laser beam being configured to have an intensity higher than the multiphoton absorption threshold of the carbonizable material in the focused region and an intensity lower than the multiphoton absorption threshold of the carbonizable material in the non-focused region; and in step S106, scanning the focal point of the laser beam along a path located inside the insulating layer, such that the carbonizable material of the insulating layer on the path undergoes multiphoton absorption and carbonization under the irradiation of the laser beam, thereby forming a conductive circuit located inside the insulating layer.

[0079] Carbonization refers to the process by which a material, under conditions such as high temperature, an inert atmosphere (e.g., nitrogen, argon), or an oxygen-deficient environment, undergoes pyrolysis to remove non-carbon elements such as hydrogen, oxygen, and nitrogen, ultimately forming a material with carbon as its main component (e.g., coke, activated carbon, graphitized carbon, carbon nanostructures, etc.). In various embodiments of this disclosure, a carbonizable material refers to a material capable of carbonization under certain conditions. Such a material may be insulating before carbonization and become conductive after carbonization. For example, carbonizable materials may include at least one of the following: polyimide, polylactic acid-glycolic acid copolymer, cellulose, chitosan, hyaluronic acid, collagen, gelatin, sodium alginate, polyurethane, polytetrafluoroethylene, expanded polytetrafluoroethylene, polylactic acid, L-polylactic acid, D-polylactic acid, polyglycolic acid, polycaprolactone, polyamide, polyterephthalic acid, ethylene glycol, polyether block polyamide, high-density polyethylene, thermoplastic polyurethane elastomer, polydimethylsiloxane, poly(p-xylene), epoxy resin, polyamide-imide, polylactic acid, polyterephthalate, SU8 photoresist, silicone, and silicone rubber.

[0080] Nonlinear absorption refers to the phenomenon where, during the interaction of light and matter, the absorption coefficient of a substance is no longer a constant value, but varies with the intensity of the incident light. The essence of nonlinear absorption stems from the nonlinear optical effects of light and matter, distinguishing it from the linear optical effect where the absorption coefficient of a substance is independent of the intensity of the incident light. Multiphoton absorption is a typical type of nonlinear absorption, defined as the simultaneous absorption of multiple photons by a substance under strong light excitation, transitioning from the ground state to an excited state. The absorption probability is proportional to the nth power of the incident light intensity (where n is the number of absorbed photons). For example, the absorption probability of two-photon absorption (n=2) is proportional to the square of the incident light intensity, and the absorption probability of three-photon absorption (n=3) is proportional to the cube of the incident light intensity.

[0081] Inducing multiphoton absorption in carbideable materials via laser beams presents two requirements. First, the laser beam wavelength must meet the following condition: while the energy of a single photon is insufficient to provide the energy required for the carbideable material to transition from its ground state to an excited state, the total energy of multiple photons must be sufficient for this transition. This is a prerequisite for multiphoton absorption in carbideable materials, but even with this energy requirement met, multiphoton absorption remains a low-probability event. Second, in addition to meeting the energy requirement, the incident light intensity must reach the multiphoton absorption threshold of the carbideable material. The multiphoton absorption threshold refers to the minimum light intensity required for significant multiphoton absorption (or phenomena induced by it, such as carbide in this paper) to occur under specific laser beam irradiation conditions. Only when the laser beam intensity exceeds the multiphoton absorption threshold will the probability of multiphoton absorption be high enough to be observed or produce a practical effect. The band gap of a material determines what kind of multiphoton absorption occurs (i.e., the value of n), which in turn determines the slope of the curve of multiphoton absorption probability versus light intensity, and consequently affects the location of the key inflection point, i.e., the determination of the multiphoton absorption threshold.

[0082] Therefore, in various embodiments of this disclosure, the characteristic that multiphoton absorption, a low-probability event, occurs significantly only under high light intensity conditions can be utilized to spatially focus the laser beam (e.g., using a high numerical aperture (NA) lens for focusing). This allows the laser beam to be configured to have an intensity higher than the multiphoton absorption threshold of the carbonizable material in the focused region and a intensity lower than the multiphoton absorption threshold of the carbonizable material in the non-focused region. This promotes carbonization of the carbonizable material in the focused region (converting it from insulation to conductivity), while preventing carbonization in the non-focused region (remaining as insulation), thereby directly converting a portion of the insulating layer into a conductive circuit in situ. Through spatially selective processing with a spatially focused laser beam, precise processing at desired locations can be achieved while causing little or no damage at undesired locations.

[0083] For illustrative purposes, Figures 2 to 4 Describes the use of Figure 1 The illustrated method is an example of the electrode fabrication process. In the figures, the z-direction indicates the thickness or depth direction of the device, and the x and y directions are each perpendicular to the z-direction and to each other.

[0084] like Figure 2 As shown, an insulating layer 210 comprising a carbonizable material is provided, and the focal point of a laser beam 220 is positioned within the insulating layer 210. The laser beam 220 is configured to have an intensity in the focused region 222 that is higher than the multiphoton absorption threshold of the carbonizable material of the insulating layer 210, and an intensity in the non-focused region (i.e., the region outside the focused region 222) that is lower than the multiphoton absorption threshold of the carbonizable material of the insulating layer 210.

[0085] like Figure 3 As shown, the focal point of the laser beam 220 is scanned along a path 230 located inside the insulating layer 210, causing the carbonizable material on the insulating layer 210 along the path 230 to undergo multiphoton absorption and carbonization under the irradiation of the laser beam 220. For example, the molecules of the carbonizable material along the path 230 can simultaneously absorb multiple photons and transition to an excited state under the irradiation of the laser beam 220, thereby generating free electron-hole pairs (plasma). The plasma rapidly absorbs the energy of the laser beam 220 and converts it into localized thermal energy, causing the carbonizable material in the focused area to instantly reach a high temperature (far exceeding the pyrolysis temperature), resulting in molecular chain breakage. Non-carbon elements such as hydrogen, oxygen, and nitrogen are removed, while the remaining carbon elements form a carbonized structure.

[0086] like Figure 4 As shown, after the focal point of the laser beam 220 traverses the path 230, the carbonized portion within the insulating layer 210 forms a conductive line 240, thereby obtaining an electrode 200 comprising the insulating layer 210 and the conductive line 240 located inside the insulating layer 210.

[0087] In some embodiments, the laser beam 220 is configured such that the carbonizable material has a transmittance of not less than 50% at the wavelength of the laser beam 220, for example, a transmittance of 50% to 85%. This reduces the linear absorption of the carbonizable material in the non-focused region by the laser beam 220, thereby improving spatial selectivity.

[0088] In some embodiments, the laser beam 220 is configured to enable the carbonizable material to undergo two-photon absorption (n=2). In some embodiments, the laser beam 220 is configured to enable the carbonizable material to undergo three-photon absorption (n=3). When n is too large, the probability of multiphoton absorption may be too low, or the required light intensity may be too high. For example, for carbonizable materials such as polyimide, carbonization can be induced by triggering their two-photon absorption using the laser beam 220.

[0089] In some embodiments, the wavelength of the laser beam 220 is in the infrared or near-infrared band. In some examples, the wavelength of the laser beam 220 can be between 780 nanometers and 1064 nanometers. For example, infrared photons (low energy) can be absorbed by two photons, causing matter to transition to an excited state that would otherwise require ultraviolet photons (high energy).

[0090] In some embodiments, the focused spot of the laser beam 220 has a diameter on the submicron to micron scale. In some examples, the diameter of the focused spot of the laser beam 220 is 2 to 5 micrometers. For example, the laser beam 220 can be configured to be focused by a lens (such as, but not limited to, a microscope objective) with an NA between 0.8 and 1.4, thereby achieving spatial lateral intensity compression. The lens (not shown) can converge the parallel-incident laser beam 220 to the focal plane. The minimum diameter d of the focused spot is determined according to the diffraction limit. min Satisfy the formula ,in λ is the wavelength of the laser beam 220, f is the focal length of the lens, and D is the diameter of the laser beam 220 when it is incident parallel to the ground. A lens with a higher focal length (NA) can obtain a smaller focused spot, thereby enhancing the concentration of light intensity and improving the carbonization accuracy.

[0091] Building upon spatial focusing, time compression can be utilized to further enhance light intensity and promote multiphoton absorption. In some embodiments, the laser beam 220 is configured as a femtosecond laser beam provided in pulsed form. A femtosecond laser beam is an ultrashort pulse laser beam with a pulse width on the order of femtoseconds. Femtosecond laser beams are characterized by energy compression in the time domain; their pulse widths are extremely small, allowing them to generate extremely high peak power even with low single-pulse energy. For example, it can be approximated that... ,in Peak power (in watts). Pulse width (in seconds) This refers to the single-pulse energy (in joules). A smaller pulse width results in higher peak power and a smaller heat-affected zone, thus preventing undesirable diffusion of carbonized regions. Through a combination of spatial focusing and time compression, the intensity of a femtosecond laser beam within the focused region can be approximated as... ,in Let A be the peak light intensity and d be the area of ​​the focused spot (assumed to be circular). By matching the single-pulse energy, pulse width, and focused spot diameter, a light intensity exceeding the multiphoton absorption threshold can be achieved within the focused region. It is important to note that if the light intensity is too low, sufficient carbonization may not be possible, while if the light intensity is too high, thermal damage outside the focused region can easily occur. In some examples, the pulse width of the femtosecond laser beam is between 50 and 200 femtoseconds. In some examples, the single-pulse energy of the femtosecond laser beam is between 1 and 10 microjoules. For deep processing of thick insulating layers, the repetition frequency of the femtosecond laser beam can be reduced to decrease heat accumulation. In some cases, the repetition frequency of the femtosecond laser beam can be increased to improve processing efficiency, but care must be taken to control the energy to avoid undesirable thermal diffusion. In some embodiments, the repetition frequency of the femtosecond laser beam is between 100 kHz and 1 MHz.

[0092] The scanning speed of the laser beam 220's focal spot should not be too fast, otherwise it may lead to insufficient energy accumulation and incomplete carbonization, thereby affecting the conductivity stability of the formed conductive line 240. The scanning speed of the laser beam 220's focal spot should also not be too slow, otherwise it may cause the carbonized area to expand and the processing accuracy to decrease. In some embodiments, the scanning speed of the laser beam 220's focal spot is between 10 micrometers per second and 100 micrometers per second.

[0093] The focus of the laser beam 220 can be scanned along path 230 once or multiple times, for example, 1 to 3 times. "Small number of scans" can promote full carbonization while controlling energy to avoid unwanted thermal diffusion.

[0094] In some embodiments, when the focal point of the laser beam 220 is scanned along the path 230, the focused spot of the laser beam 220 at the scanning position on the path 230 partially overlaps with the focused spot of the laser beam 220 at the adjacent scanning position on the path 230. For example, the overlap rate can be 30% to 50% to promote carbonization continuity and improve the conductivity stability of the formed conductive line 240.

[0095] Because the focused spot of the laser beam 220 is small, the size of the conductive line 240 obtained by scanning the focal point of the laser beam 220 along path 230 may be small in the zy plane. In some cases, it may be desirable for the conductive line 240 to have a larger cross-sectional area, for example, to reduce resistance. In some embodiments, such as... Figure 5As shown, the focal point of the laser beam 220 can also be scanned along a path 232 extending parallel to the path 230 within the insulating layer 210, causing the carbonizable material of the insulating layer on the path 232 to undergo multiphoton absorption and carbonize under the irradiation of the laser beam 220. Specifically, the focused spot of the laser beam 220 at the scanning position on the path 232 and the corresponding scanning position of the laser beam 220 on the path 230 (refer to...) Figure 5 The focused spots at the two scanning positions (meaning "aligned with each other in the x-direction") partially overlap each other. For example, the overlap rate can be 30% to 50% to promote carbonization continuity and improve the conductivity stability of the formed conductive line 240. This allows for a thickened conductive line 240 in the z-direction. The focal point of the laser beam 220 can be scanned as described above along one or more additional paths adjacent to path 230 in the z-direction and / or one or more additional paths adjacent to path 230 in the y-direction, as needed, to achieve a conductive line 240 with a desired cross-sectional area.

[0096] In some embodiments, path 230 may be configured to extend from the interior of insulating layer 210 to the side surface of insulating layer 210, such that the end of the formed conductive line 240 is exposed on the side surface. This may, for example, allow the end of conductive line 240 to provide an electrode site or a rear end site. In some embodiments, both ends of the formed conductive line 240 may be exposed on the side surface of insulating layer 210, thereby providing an electrode site and a rear end site, respectively. For example, when electrode 200 is implanted into nerve tissue, the electrode site may be used to acquire electrical signals from and / or apply electrical signals to the nerve tissue, and the rear end site may be used to realize bidirectional electrical signal transmission between the electrode site and the rear end circuit via conductive line 240. The rear end circuit may refer to circuitry located at the rear end of the electrode, such as signal recording circuitry, signal processing circuitry, signal generation circuitry, etc., associated with the signal from the electrode.

[0097] In other embodiments, such as reference Figure 6 Conductive lines 242 can be formed in the insulating layer 210, which are configured to extend at one end to the surface of the insulating layer 210 to provide electrode sites and connect at the other end to the conductive lines 240.

[0098] In some examples, the conductive line 242 can be formed by scanning the focal point of the laser beam 220 along a path extending between the surface of the insulating layer 210 and the conductive line 240. The specific process is similar to forming the conductive line 240 by scanning the focal point of the laser beam 220 along path 230, and will not be elaborated further here. In such examples, the surface of the insulating layer 210 can be the upper surface of the insulating layer 210 (e.g., Figure 6The surface shown (or the lower surface) can be any side surface of the insulating layer 210. Conductive lines 242 provide electrode sites 250 at the surface of the insulating layer 210. In some cases, the focal point of the laser beam 220 can be scanned in the region corresponding to the electrode sites 250 on the surface of the insulating layer 210, such that the carbonizable material in that region is carbonized under the irradiation of the laser beam 220 to form electrode sites 250 with the desired shape and size. Additionally, refer to... Figure 7 Furthermore, a conductive coating 260 can be formed on the electrode site 250 to reduce the impedance at the electrode site 250, improve conductivity, and construct a stable electrode-tissue electrochemical interface. The conductive coating 260 can be formed using conductive metallic or non-metallic materials, including polyethylene dioxythiophene (PEDOT), iridium oxide, etc.

[0099] In some examples, the conductive line 242 can be formed by depositing a conductive medium (such as, but not limited to, a metallic material) in a trench extending from the surface of the insulating layer 210 to the conductive line 240. This can be achieved, for example, by photolithography, etching, and deposition processes. The electrode site 250 with a desired shape and size can be achieved by controlling the shape and size of the trench at the surface of the insulating layer 210. Alternatively, in such examples, a conductive plating layer 260 can be formed over the electrode site 250 to reduce the impedance at the electrode site 250, improve conductivity, and construct a stable electrode-tissue electrochemical interface.

[0100] In some examples, the conductive line 242 may be formed through a via extending from the surface of the insulating layer 210 to the conductive line 240, the via being able to receive a conductive medium to form the conductive line 242. For example, when the electrode 200 is not implanted into the nerve tissue, the via is empty, and the conductive line 242 is not formed; when the electrode 200 is implanted into the nerve tissue, conductive tissue fluid enters and fills the via to form the conductive line 242.

[0101] refer to Figure 8 In some embodiments, a conductive line 244 may be formed in the insulating layer 210, configured to extend at one end to the surface of the insulating layer 210 to provide a rear end point 270, and connect at the other end to the conductive line 240. The conductive line 244 may be formed using a method similar to that used to form the conductive line 242, which will not be elaborated here. In some examples, a conductive plating layer 280 may also be formed over the rear end point 270 to reduce the impedance at the rear end point 270. Although Figure 8 The electrode site 250 and the rear end site 270 are depicted as being located on the same surface of the insulating layer 210, but this is merely exemplary and not limiting. The electrode site 250 and the rear end site 270 may be arranged at desired locations as needed.

[0102] refer to Figure 9 and Figure 10 In some embodiments, the focal point of the laser beam 220 can be scanned along a path 236 located inside the insulating layer 210 and at a different depth from the path 230. This causes the carbonizable material of the insulating layer 210 on the path 236 to undergo multiphoton absorption and carbonization under the irradiation of the laser beam 220, thereby forming a conductive line 246 located inside the insulating layer 210. Figure 10 As shown, similar to how conductive lines 242 are used to lead conductive lines 240 located inside the insulating layer 210 to electrode sites 250 located on the surface of the insulating layer 210, additional conductive lines 246 can be used to lead conductive lines 246 located inside the insulating layer 210 to electrode sites 256 located on the surface of the insulating layer 210. These additional conductive lines can be formed using a method similar to that used for forming conductive lines 242, which will not be elaborated upon here.

[0103] refer to Figure 11 In some embodiments, the focal point of the laser beam 220 can be scanned along a path 238 located inside the insulating layer 210 and at the same depth as the path 230 but spaced apart from it (in the y-direction). This causes the carbonizable material of the insulating layer 210 on the path 238 to undergo multiphoton absorption and carbonize under the irradiation of the laser beam 220, thereby forming a conductive line 248 located inside the insulating layer 210. Similar to using conductive line 242 to lead the conductive line 240 located inside the insulating layer 210 to the electrode site 250 located on the surface of the insulating layer 210, an additional conductive line can be used to lead the conductive line 248 located inside the insulating layer 210 to the electrode site 258 located on the surface of the insulating layer 210. This additional conductive line can be formed using a method similar to that used for forming conductive line 242, which will not be described in detail here.

[0104] Combination Figure 10 and Figure 11 The illustrated embodiment can be adapted to several additional embodiments. By forming multiple conductive lines extending in the x-direction and spaced apart from each other in the z-direction and / or y-direction, multiple electrode sites can be provided respectively, thereby enabling multi-channel signal transmission within a single electrode.

[0105] refer to Figure 12 In some embodiments, an insulating layer 210 is formed on a substrate 290. The substrate 290 may include, but is not limited to, silicon wafers, glass sheets, flexible polymer films (such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN)), etc., and is not particularly limited thereto. The substrate 290 can provide support during electrode fabrication and can be removed when electrode fabrication is complete. In some embodiments, such as Figure 12As shown, the focal point of the laser beam 220 can be positioned on the lower surface of the insulating layer 210 facing the substrate 290, and the focal point of the laser beam 220 can be scanned along the path 234 located on the lower surface. This causes the carbonizable material of the insulating layer 210 on the path 234 to undergo multiphoton absorption and carbonize under the irradiation of the laser beam 220, and separates the insulating layer 210, which has conductive lines formed inside and whose lower surface is at least partially carbonized, from the substrate 290. Since the purpose of at least partially carbonizing the lower surface of the insulating layer 210 is to promote the separation of the insulating layer 210 from the substrate 290, rather than to form conductive lines, these carbonized portions do not need to be continuous; for example, they can be discrete. When the substrate 290 is made of a light-transmitting material such as a glass plate, the laser beam 220 can be incident from the substrate 290 to reduce the influence of the laser beam 220 on the rest of the insulating layer 210.

[0106] Figure 13 A method 300 for preparing an electrode according to some embodiments of the present disclosure is shown. For example... Figure 13 As shown, method 300 includes: in step S302, providing a first insulating layer, the first insulating layer including a first carbonizable material; in step S304, positioning the focus of a first laser beam on the upper surface of the first insulating layer, the first laser beam being configured to have a light intensity in the focused region higher than a first multiphoton absorption threshold of the first carbonizable material, and a light intensity in the non-focused region lower than the first multiphoton absorption threshold of the first carbonizable material; in step S306, scanning the focus of the first laser beam along a path located on the upper surface of the first insulating layer, causing the first carbonizable material of the first insulating layer on the path to undergo multiphoton absorption and carbonization under the irradiation of the first laser beam, thereby forming a conductive line on the upper surface of the first insulating layer; and forming a second insulating layer on the first insulating layer on which the conductive line is formed.

[0107] For illustrative purposes, Figures 14 to 17 Describes the use of Figure 13 The method shown is an example of the process for preparing electrodes.

[0108] like Figure 14 As shown, a first insulating layer 410 comprising a first carbable material is provided, and the focal point of a first laser beam 420 is positioned on the upper surface of the first insulating layer 410. The first laser beam 420 is configured to have a light intensity in a focused region 422 that is higher than a first multiphoton absorption threshold of the first carbable material of the first insulating layer 410, and a light intensity in a non-focused region (i.e., a region outside the focused region 422) that is lower than the first multiphoton absorption threshold of the first carbable material of the first insulating layer 410.

[0109] like Figure 15 and Figure 16As shown, the focal point of the first laser beam 420 is scanned along a path 430 located on the upper surface of the first insulating layer 410. This causes the first carburizable material of the first insulating layer 410 on the path 430 to undergo multiphoton absorption and carbonization under the irradiation of the first laser beam 420, thereby forming a conductive line 440 located on the upper surface of the first insulating layer 410. The configuration of the parameters of the first laser beam 420 and its scanning can be similar to that of the laser beam 220, and will not be described in detail here.

[0110] like Figure 17 As shown, a second insulating layer 412 is formed on top of a first insulating layer 410 on which conductive lines 440 are formed, thereby obtaining an electrode 400 comprising the first insulating layer 410, the second insulating layer 412, and the conductive lines 440 located therebetween. The second insulating layer 412 may have the same or different material as the first insulating layer 410.

[0111] In some embodiments, prior to forming the second insulating layer 412, a metal layer (not shown) may be formed on the first insulating layer 410, on which conductive lines 440 are formed, and this metal layer is patterned to cover the conductive lines 440. Specifically, the patterned metal layer may have a pattern corresponding to the conductive lines 440 and may act as a backup conductive line to promote the stability of the conductivity and signal transmission capability of the electrode 400. For example, the metal layer may be implemented as a thin film of gold, copper, and / or titanium with a thickness of 50 nanometers to 200 nanometers. In some embodiments, prior to forming the metal layer, the upper surface of the first insulating layer 410 may be subjected to plasma treatment to improve the adhesion between the metal layer and the first insulating layer 410.

[0112] The stability of the multilayer structure of electrode 400 can be enhanced through various suitable bonding processes. In some embodiments, a functionalized molecular film is formed on the upper surface of the first insulating layer 410 before the formation of the second insulating layer 412, so that the first insulating layer 410 and the second insulating layer 412 are bonded together by the chemical bonding of the functionalized molecular film after the formation of the second insulating layer 412. Additionally or alternatively, in some embodiments, a photocurable adhesive is applied to the upper surface of the first insulating layer 410 before the formation of the second insulating layer 412, so that the first insulating layer 410 and the second insulating layer 412 are bonded together by curing the photocurable adhesive by ultraviolet light after the formation of the second insulating layer 412. Additionally or alternatively, in some embodiments, after the formation of the second insulating layer 412, the first insulating layer 410 and the second insulating layer 412 are bonded together by thermocompression bonding or ultrasonic welding.

[0113] In some embodiments, such as reference Figure 18Conductive lines 442 can be formed in the second insulating layer 412, which are configured to extend at one end to the upper surface of the second insulating layer 412 to provide electrode sites and to be connected at the other end to conductive lines 440.

[0114] In some examples, the conductive line 442 may be formed by scanning the focal point of a second laser beam along a path extending between the surface of the second insulating layer 412 and the conductive line 440. The second insulating layer 412 may include a second carbideable material. The second laser beam may be configured to have an intensity higher than a second multiphoton absorption threshold of the second carbideable material in the focused region and an intensity lower than the second multiphoton absorption threshold of the second carbideable material in the unfocused region. The specific process may be similar to scanning the focal point of a first laser beam 420 along path 430 to form the conductive line 440, and will not be elaborated further here. In such an example, the surface of the second insulating layer 412 may be the upper surface of the second insulating layer 412 (e.g., Figure 18 (As shown), or any side surface of the second insulating layer 412. Conductive lines 442 provide electrode sites 450 at the surface of the second insulating layer 412. In some cases, the focal point of the second laser beam can be scanned in the region corresponding to the electrode site 450 on the surface of the second insulating layer 412, such that the carbonizable material in that region is carbonized under the irradiation of the second laser beam to form electrode sites 450 with the desired shape and size. Additionally, refer to... Figure 18 Furthermore, a conductive coating 460 can be formed on the electrode site 450 to reduce the impedance at the electrode site 450, improve conductivity, and build a stable electrode-tissue electrochemical interface.

[0115] When the second carbideable material is the same as the first carbideable material, the second multiphoton absorption threshold can be the same as the first multiphoton absorption threshold, thus the second laser beam can be the same as the first laser beam 420. When the second carbideable material is different from the first carbideable material, the second multiphoton absorption threshold may not be the same as the first multiphoton absorption threshold, and therefore the second laser beam may not be the same as the first laser beam 420. The parameter configuration of the second laser beam and its scanning can also be similar to that of laser beam 220, and will not be elaborated further here.

[0116] In some examples, the conductive line 442 can be formed by depositing a conductive medium (such as, but not limited to, a metallic material) in a trench extending from the upper surface of the second insulating layer 412 to the conductive line 440. This can be achieved, for example, by photolithography, etching, and deposition processes. The electrode site 450 with a desired shape and size can be achieved by controlling the shape and size of the trench at the upper surface of the second insulating layer 412. Additionally, in such examples, a conductive plating layer 460 can be formed over the electrode site 450 to reduce the impedance at the electrode site 450, improve conductivity, and construct a stable electrode-tissue electrochemical interface.

[0117] In some examples, the conductive line 442 may be formed by a through-hole extending from the upper surface of the second insulating layer 412 to the conductive line 440, the through-hole being able to receive a conductive medium therein to form the conductive line 442. For example, when the electrode 400 is not implanted into the nerve tissue, the through-hole is empty, and the conductive line 442 is not formed; when the electrode 400 is implanted into the nerve tissue, conductive tissue fluid enters and fills the through-hole to form the conductive line 442.

[0118] Still referencing Figure 18 In some embodiments, a conductive line 444 may be formed in the second insulating layer 412, configured to extend at one end to the surface of the second insulating layer 412 to provide a rear end point 470, and to connect at the other end to the conductive line 440. The conductive line 444 may be formed using a method similar to that used to form the conductive line 442, which will not be elaborated here. In some examples, a conductive plating layer 480 may also be formed over the rear end point 470 to reduce the impedance at the rear end point 470. Although Figure 18 The electrode site 450 and the rear end site 470 are depicted as being located on the same surface of the second insulating layer 412, but this is merely exemplary and not limiting. The electrode site 450 and the rear end site 470 can be arranged at desired locations as needed. Additionally, although... Figure 18 The electrode site 450 and its associated conductive line 442, and the rear end site 470 and its associated conductive line 444 are all depicted as being disposed at the second insulating layer 412, but this is merely exemplary and not limiting, and they may each be disposed at the first insulating layer 410 and / or the second insulating layer 412.

[0119] refer to Figure 19In some embodiments, the focus of the first laser beam 420 can be positioned inside the first insulating layer 410, and the focus of the first laser beam 420 can be scanned along a path located inside the first insulating layer 410, causing the first carburizable material of the first insulating layer 410 on this path to undergo multiphoton absorption and carbonization under the irradiation of the first laser beam 420, thereby forming a conductive line 446 located inside the first insulating layer 410. Additionally or alternatively, in some embodiments, the focus of the second laser beam can be positioned inside the second insulating layer 412, and the focus of the second laser beam can be scanned along a path located inside the second insulating layer 412, causing the second carburizable material of the second insulating layer 412 on this path to undergo multiphoton absorption and carbonization under the irradiation of the second laser beam, thereby forming a conductive line 448 located inside the second insulating layer 412. Figure 19 As shown, similar to how conductive line 440 located between the first insulating layer 410 and the second insulating layer 412 is led out to electrode site 450 located on the upper surface of the second insulating layer 412 using conductive line 442, conductive line 446 located inside the first insulating layer 410 can be led out to electrode site 456 located on the upper surface of the second insulating layer 412 using a first additional conductive line, and conductive line 448 located inside the second insulating layer 412 can be led out to electrode site 458 located on the upper surface of the second insulating layer 412 using a second additional conductive line. These additional conductive lines can be formed using a method similar to that used to form conductive line 442, which will not be elaborated here.

[0120] By forming multiple conductive lines extending in the x-direction and spaced apart from each other in the z-direction and / or y-direction, multiple corresponding electrode sites can be provided, thereby enabling multi-channel signal transmission within a single electrode. These conductive lines can be distributed inside the first insulating layer 410, between the first insulating layer 410 and the second insulating layer 412, and / or inside the second insulating layer 412.

[0121] refer to Figure 20 In some embodiments, a first insulating layer 410 is formed on a substrate 490. The substrate 490 may be similar to substrate 290, and is not particularly limited thereto. The substrate 490 may provide support during electrode fabrication and may be removed when electrode fabrication is complete. In some embodiments, such as Figure 20As shown, the focus of the first laser beam 420 can be positioned on the lower surface of the first insulating layer 410 facing the substrate 490, and the focus of the first laser beam 420 can be scanned along a path 434 located on the lower surface. This causes the carbonizable material of the first insulating layer 410 on the path 434 to undergo multiphoton absorption and carbonize under the irradiation of the first laser beam 420, and separates the stack of the first insulating layer 410, on which the conductive line 440 is formed on its upper surface and whose lower surface is at least partially carbonized, from the substrate 490. Since the purpose of at least partially carbonizing the lower surface of the first insulating layer 410 is to promote the separation of the insulating layer stack from the substrate 490, rather than to form conductive lines, these carbonized portions do not need to be continuous; for example, they can be discrete. When the substrate 490 is made of a light-transmitting material such as a glass plate, the first laser beam 420 can be incident from the substrate 490 to reduce the influence of the first laser beam 420 on the remaining portion of the first insulating layer 410.

[0122] Compared to Method 300, Method 100 allows the conductive lines to be formed directly within the insulating layer without the need for an additional insulating layer to isolate the conductive lines, and also eliminates the need for additional bonding processes to improve structural stability. Apart from this, Method 300 is essentially similar to Method 100; therefore, please refer to the preceding descriptions of various embodiments of Method 100, which will not be repeated here.

[0123] It is understood that although dashed lines are used to indicate paths in the accompanying drawings, this is merely illustrative and not restrictive. Actual paths can be continuous or discontinuous, depending on specific needs. Furthermore, while various paths are depicted as straight lines in the drawings, in practical applications, a wide variety of paths can be designed according to specific requirements, including but not limited to straight lines, polygonal lines, curves, or combinations thereof. For example, computer-aided design (CAD) software (such as AutoCAD, L-Edit) can be used to design the required conductive circuit patterns, including interdigitated, spiral, and grid patterns, and the designed patterns can be converted into file formats (such as DXF, G-code) recognizable by laser processing equipment, thereby controlling the laser beam focus scanning path.

[0124] This disclosure also provides an electrode comprising: an insulating layer comprising a carbonizable material; and a conductive line located within the insulating layer. The conductive line is formed by scanning a path located within the insulating layer with a focal point of a laser beam, causing the carbonizable material in the insulating layer along this path to undergo multiphoton absorption and carbonize under the irradiation of the laser beam. The laser beam is configured to have an intensity higher than the multiphoton absorption threshold of the carbonizable material in the focused region and an intensity lower than the multiphoton absorption threshold of the carbonizable material in the non-focused region. For example, the electrode may be an electrode (e.g., electrode 200, 400) prepared by a method for preparing an electrode according to any embodiment of this disclosure (e.g., method 100, 300).

[0125] When the carbonizable material is a flexible material, the method disclosed herein can be used to fabricate flexible electrodes. For example, Figure 21 A method 500 for fabricating a flexible electrode according to some embodiments of the present disclosure is shown. For example... Figure 21 As shown, method 500 includes: in step S502, providing a polyimide layer; in step S504, positioning the focus of a near-infrared femtosecond pulsed laser beam inside the polyimide layer, the near-infrared femtosecond pulsed laser beam being configured to have an intensity higher than the two-photon absorption threshold of the polyimide in the focused region and an intensity lower than the two-photon absorption threshold of the polyimide in the unfocused region; and in step S506, scanning the focus of the near-infrared femtosecond pulsed laser beam along a path located inside the polyimide layer, such that the polyimide in the polyimide layer on the path undergoes two-photon absorption and carbonization under the irradiation of the near-infrared femtosecond pulsed laser beam, thereby forming a conductive circuit located inside the polyimide layer.

[0126] For purposes of non-limiting illustration, an example process for preparing a flexible electrode using method 500 is described below.

[0127] A substrate is provided. The substrate can be a silicon wafer, glass sheet, or flexible polymer film (such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN)), and can be cleaned. For example, it can be cleaned sequentially with acetone and ethanol for 10 to 15 minutes to remove surface contaminants, then rinsed with deionized water and dried in a vacuum drying oven at 60 to 80 degrees Celsius for 2 to 3 hours to ensure a clean and dry substrate surface, thus providing favorable conditions for subsequent coating adhesion.

[0128] Polyimide resin solutions are uniformly coated onto a substrate surface using processes such as spin coating, blade coating, or spray coating. For example, the polyimide resin solution can have a solid content of 10% to 20%, and the solvent is N,N-dimethylacetamide (DMAc). Polyimide exhibits excellent high-temperature resistance, good flexibility, and chemical stability. Taking spin coating as an example, the spin coating parameters can be adjusted according to the desired coating thickness. For instance, when a polyimide layer of 5 to 10 micrometers is desired, the spin coating speed can be set to 2000 to 3000 rpm, and the spin time to 30 to 60 seconds.

[0129] After coating, a thermosetting process can be performed. For example, the substrate coated with a polyimide resin solution can be baked at 80 degrees Celsius for 10 to 15 minutes to remove most of the solvent, then heated to 150 degrees Celsius and baked for 15 to 20 minutes to allow the polyimide to undergo initial cross-linking, and finally heated to 300 degrees Celsius and baked for 30 to 40 minutes to complete the full curing of the polyimide, thereby forming a dense, uniform, and insulating polyimide layer. The imidization reaction can be carried out under a nitrogen atmosphere.

[0130] Next, the near-infrared femtosecond pulsed laser beam is focused on the interior or surface of the polyimide layer and scanned along a predetermined path to convert the polyimide in situ into conductive carbides, thereby forming a conductive circuit. For example, under the irradiation of the near-infrared femtosecond pulsed laser beam, the polyimide in the focused region undergoes two-photon absorption, and its imide ring (-CO-N-CO-) breaks first, releasing small molecules such as CO2 and CO. The carbon-nitrogen bonds (CN) on the molecular chain break, generating aromatic ring segments containing free radicals. These free radicals collide with each other to form carbon-carbon (CC) covalent cross-linking bonds, constructing an amorphous carbon skeleton prototype. At this point, the interface between the carbonized part (amorphous carbon) and the uncarbonized polyimide is connected through the unbroken aromatic ring segments and the newly generated CC cross-linking bonds, which is a molecular-level physical-chemical intercalation with high bonding strength.

[0131] Near-infrared femtosecond pulsed laser beams can have wavelengths ranging from 780 nm to 1064 nm. Polyimide exhibits high transmittance in this wavelength band, thereby reducing linear absorption in unfocused areas and improving spatial selectivity in processing. Furthermore, near-infrared femtosecond pulsed laser beams can have pulse widths between 50 and 200 femtoseconds and single-pulse energies between 1 and 10 microjoules. Additionally, lenses with a focal length (NA) between 0.8 and 1.4 can be used to focus the near-infrared femtosecond pulsed laser beam into a spot with a diameter of 2 to 5 micrometers. By controlling the diameter of the focused spot, precise control of the linewidth of the conductive circuit can be achieved. Through a combination of spatial focusing and time compression, high light intensity far exceeding the two-photon absorption threshold can be formed in the focused region to trigger carbonization of the polyimide within the focused region. Laser beam parameters and scanning parameters can be specifically set according to the thickness of the polyimide layer and the desired conductive circuit configuration. For example, the repetition frequency of a near-infrared femtosecond pulsed laser beam can be between 100 kHz and 1 MHz, the scanning speed can be between 10 μm / s and 100 μm / s, the number of scans can be 2 to 3, and the overlap rate between adjacent scan points or adjacent scan lines can be 30% to 50%. A scanning accuracy of ±1 μm can be achieved through a high-precision galvanometer scanning system.

[0132] When conductive lines are formed directly inside a polyimide layer, the focal depth of the laser beam within the polyimide layer can be adjusted according to the thickness of the polyimide layer. The adjustment range of the focal position can reach hundreds of micrometers, which can fully cover the precision processing requirements of polyimide layers of various thicknesses.

[0133] When forming conductive lines on the surface of a polyimide layer, plasma activation can be performed on the locally carbonized polyimide layer surface (e.g., using argon plasma with a processing power of 50 to 100 watts and a processing time of 1 to 2 minutes). Then, a patterned metal layer is formed on the plasma-treated polyimide layer surface according to the conductive line pattern to further improve conductivity. For example, a gold or copper film with a thickness of 50 to 200 nanometers can be deposited by electron beam evaporation (the vacuum level during deposition can be controlled at 10). -3(Below the Pa), titanium or platinum films can also be deposited by magnetron sputtering at a power of 100 to 200 watts in an argon flow rate of 10 standard cubic centimeters per minute (sccm) to 20 sccm. Next, another layer of polyimide resin solution is coated and thermosetting is performed to form an additional polyimide layer for isolating the conductive lines. Subsequently, bonding between the polyimide layers on the upper and lower sides of the conductive lines can be achieved through a hot-pressing process to enhance the stability of the multilayer structure and suppress delamination. For example, the temperature of the hot-pressing process can be between 200 and 300 degrees Celsius (below the glass transition temperature of polyimide, 350 degrees Celsius), the pressure can be between 1 MPa and 5 MPa, and the holding time can be between 10 and 30 minutes. Alternatively or additionally, bonding between the polyimide layers on the upper and lower sides of the conductive lines can be achieved using molecular self-assembly processes, ultrasonic welding processes, or photopolymerization bonding processes. For example, silane coupling agents (such as 3-aminopropyltriethoxysilane) can be used to self-assemble on the surface of a polyimide layer to form an amino-functionalized layer, which bonds to the polyimide layers on both sides through chemical bonding. During self-assembly, molecules spontaneously arrange themselves into an ordered structure, enhancing interfacial bonding and reducing interfacial energy, effectively suppressing delamination. Ultrasonic welding can generate high-frequency vibrations using an ultrasonic transducer, creating frictional heat and mechanical pressure at the interface of the two polyimide layers, promoting intermolecular diffusion and fusion, achieving a strong bond. Ultrasonic welding features short heating time and low temperature, avoiding the impact of high temperatures on the properties of polyimide, making it particularly suitable for temperature-sensitive material systems. It also effectively improves interlayer bonding strength and reduces the risk of delamination. Photocurable bonding processes can uniformly coat a photocurable adhesive (such as acrylate-based adhesives) between two polyimide layers and then cure it under ultraviolet light. By adjusting the formulation and curing parameters (such as light intensity and light exposure time) of the UV-curable adhesive, the curing speed and performance of the UV-curable adhesive can be controlled, achieving good adhesion with polyimide, while avoiding delamination problems caused by solvent evaporation or curing shrinkage of traditional adhesives.

[0134] Next, the prepared electrode can be cleaned, for example by ultrasonic cleaning with deionized water for 5 to 10 minutes to remove debris and residues. The prepared electrode can also be vacuum annealed, for example by holding it at 200 to 250 degrees Celsius for 1 to 2 hours, to optimize the crystal structure of the conductive carbide.

[0135] Finally, the substrate can be peeled off. For example, the focus of a near-infrared femtosecond pulsed laser beam can be scanned at the interface between the polyimide layer and the substrate to at least partially carbonize the lower surface of the polyimide layer, thereby facilitating substrate peeling.

[0136] Method 500 can be described with reference to the various embodiments of methods 100 and 300 described above, and will not be repeated here.

[0137] Accordingly, this disclosure also provides a flexible electrode comprising: a polyimide layer; and conductive lines located within the polyimide layer. The conductive lines are formed by scanning a path located within the polyimide layer with the focal point of a near-infrared femtosecond pulsed laser beam, causing the polyimide in the polyimide layer along this path to undergo two-photon absorption and carbonization under the irradiation of the near-infrared femtosecond pulsed laser beam. The near-infrared femtosecond pulsed laser beam is configured to have an intensity higher than the two-photon absorption threshold of the polyimide in the focused region and an intensity lower than the two-photon absorption threshold of the polyimide in the non-focused region.

[0138] Figure 22 FIB images of a flexible electrode prepared using method 500 are shown. The flexible electrode comprises a polyimide layer and conductive lines derived in situ from the polyimide located within it. Testing revealed that the polyimide flexible electrode obtained by practicing the teachings of this disclosure achieves a sheet resistance of less than 100 ohms / square (measured by the four-probe method), a bond strength of more than 5 MPa (measured by the cross-cut test (ISO 2409 standard) or peel test), and a delamination rate of less than 5% (measured by 100 thermal cycles from -40°C to 125°C).

[0139] This disclosure also provides an electrode array that may include a plurality of electrodes. Each of these electrodes may be an electrode or a flexible electrode according to any embodiment of this disclosure, or an electrode (such as electrode 200, 400) prepared by a method for preparing an electrode according to any embodiment of this disclosure (such as method 100, 300), or an electrode prepared by a method for preparing a flexible electrode according to any embodiment of this disclosure (such as method 500).

[0140] The terms “left,” “right,” “front,” “back,” “top,” “bottom,” “upper,” “lower,” “high,” “lower,” etc., used in the specification and claims, if present, are for descriptive purposes and not necessarily for describing unchanging relative positions. It should be understood that such terms are interchangeable where appropriate, enabling embodiments of this disclosure described herein to operate, for example, in orientations different from those shown or otherwise described herein. For example, when the device in the drawings is reversed, a feature previously described as “above” other features may now be described as “below” other features. The device may also be oriented in other ways (rotated 90 degrees or in other orientations), in which case the relative spatial relationships will be interpreted accordingly.

[0141] In the specification and claims, when an element is described as being "on top of," "attached to," "connected to," "coupled to," or "in contact with" another element, the element may be directly located on top of, directly attached to, directly connected to, directly coupled to, or directly in contact with the other element, or one or more intermediate elements may be present. Conversely, when an element is described as being "directly" located on top of, directly attached to, directly connected to, directly coupled to, or directly in contact with another element, no intermediate elements are present. In the specification and claims, when a feature is arranged "adjacent" to another feature, it may mean that a feature has a portion overlapping with the adjacent feature or a portion located above or below the adjacent feature.

[0142] As used herein, the term “exemplary” means “serving as an example, instance, or illustration” and not as a “model” to be precisely copied. Any implementation described herein by example is not necessarily to be construed as preferred or advantageous over other implementations. Moreover, this disclosure is not limited to any theory expressed or implied as given in the field of art, background art, summary of invention, or detailed description.

[0143] As used herein, the term "substantially" means any minor variation resulting from design or manufacturing defects, device or component tolerances, environmental influences, and / or other factors. The term "substantially" also allows for differences from the perfect or ideal situation due to parasitic effects, noise, and other practical considerations that may exist in the actual implementation.

[0144] Additionally, terms such as “first,” “second,” etc., may be used herein for reference only and are therefore not intended to be limiting. For example, unless the context clearly indicates otherwise, the words “first,” “second,” and other such numerical terms relating to structures or elements do not imply order or sequence. It should also be understood that the term “including / contains,” when used herein, indicates the presence of the indicated feature, whole, step, operation, unit, and / or component, but does not preclude the presence or addition of one or more other features, wholes, steps, operations, units, and / or components, and / or combinations thereof.

[0145] In this disclosure, the term “provide” is used broadly to cover all ways of obtaining an object, and therefore “provide an object” includes, but is not limited to, “purchasing,” “preparing / manufacturing,” “arranging / setting up,” “installing / assembling,” and / or “ordering” an object.

[0146] As used herein, the term “and / or” includes any and all combinations of one or more of the listed items in association. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. As used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise.

[0147] Those skilled in the art will recognize that the boundaries between the above operations are merely illustrative. Multiple operations may be combined into a single operation, a single operation may be distributed among additional operations, and operations may be performed with at least partial overlap in time. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be changed in various other embodiments. However, other modifications, variations, and substitutions are equally possible. Aspects and elements of all the embodiments disclosed above may be combined in any way and / or in combination with aspects or elements of other embodiments to provide multiple additional embodiments. Therefore, this specification and the accompanying drawings should be considered illustrative rather than restrictive.

[0148] While specific embodiments of this disclosure have been described in detail by way of example, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of this disclosure. The various embodiments disclosed herein can be combined in any way without departing from the spirit and scope of this disclosure. Those skilled in the art should also understand that various modifications can be made to the embodiments without departing from the scope and spirit of this disclosure. The scope of this disclosure is defined by the appended claims.

Claims

1. A method for preparing an electrode, characterized in that, The method includes: An insulating layer is provided, the insulating layer comprising a carbonizable material; The laser beam is focused within the insulating layer, and the laser beam is configured to have an intensity higher than the multiphoton absorption threshold of the carbonizable material in the focused region and an intensity lower than the multiphoton absorption threshold of the carbonizable material in the unfocused region; and The laser beam is focused along a path located inside the insulating layer, causing the carbonizable material in the insulating layer along the path to undergo multiphoton absorption and carbonize under the irradiation of the laser beam, thereby forming a conductive circuit located inside the insulating layer.

2. The method according to claim 1, characterized in that, The conductive line is a first conductive line, and the method further includes: A second conductive line is formed in the insulating layer, the second conductive line being configured to extend at one end to the surface of the insulating layer to provide an electrode site, and at the other end to connect to the first conductive line.

3. The method according to claim 2, characterized in that: The path is a first path, and the second conductive line is formed by scanning the focal point of the laser beam along a second path extending between the surface of the insulating layer and the first conductive line, or The second conductive line is formed by depositing a conductive medium in a trench extending from the surface of the insulating layer to the first conductive line, or The second conductive line is formed by a through-hole extending from the surface of the insulating layer to the first conductive line, the through-hole being able to receive a conductive medium therein to form the second conductive line.

4. The method according to claim 2, characterized in that, The method further includes: A conductive plating layer is formed on the electrode sites.

5. The method according to claim 1, characterized in that, When the focal point of the laser beam is scanned along the path, the focused spot of the laser beam at the scanned position on the path partially overlaps with the focused spot of the laser beam at the adjacent scanned position on the path.

6. The method according to claim 1, characterized in that, The path is the first path, and the method further includes: The laser beam is focused along a third path located inside the insulating layer, causing the carbonizable material of the insulating layer along the third path to undergo multiphoton absorption and carbonize under the irradiation of the laser beam.

7. The method according to claim 6, characterized in that: The third path extends alongside the first path, and when the focal point of the laser beam is scanned along the third path, the focused spot of the laser beam at the scanning position on the third path partially overlaps with the focused spot of the laser beam at the corresponding scanning position on the first path. or The first path and the third path are located at different depths within the insulating layer; or The first path and the third path are located at the same depth inside the insulating layer and are spaced apart from each other.

8. The method according to claim 1, characterized in that, The path is a first path, the insulating layer is formed on the substrate, and the method further includes: The laser beam is focused on the lower surface of the insulating layer facing the substrate, and the focus of the laser beam is scanned along a fourth path located on the lower surface, causing the carbonizable material of the insulating layer along the fourth path to undergo multiphoton absorption and carbonize under the irradiation of the laser beam; and The insulating layer, in which the conductive lines are formed and whose lower surface is at least partially carbonized, is separated from the substrate.

9. The method according to claim 1, characterized in that: The laser beam is configured such that the carbonizable material has a transmittance of not less than 50% at the wavelength of the laser beam; and / or The laser beam is configured to enable the carbonizable material to undergo two-photon absorption, or is configured to enable the carbonizable material to undergo three-photon absorption; and / or The wavelength of the laser beam is in the near-infrared band, or between 780 nanometers and 1064 nanometers; and / or The focused spot of the laser beam has a diameter on the order of submicron to micron; and / or The laser beam is configured to be focused by a lens with a numerical aperture between 0.8 and 1.4; and / or The scanning speed is between 10 micrometers per second and 100 micrometers per second; and / or The scan is performed 1 to 3 times along the path; and / or The laser beam is configured as a femtosecond laser beam provided in pulse form, wherein: The pulse width of the femtosecond laser beam is between 50 femtoseconds and 200 femtoseconds, and / or The repetition frequency of the femtosecond laser beam is between 100 kHz and 1 MHz, and / or The single-pulse energy of the femtosecond laser beam is between 1 microjoule and 10 microjoules.

10. The method according to claim 1, characterized in that, The carbonizable material includes at least one of the following: Polyimide, polylactic acid-glycolic acid copolymer, cellulose, chitin, hyaluronic acid, collagen, gelatin, sodium alginate, polyurethane, polytetrafluoroethylene, expanded polytetrafluoroethylene, polylactic acid, L-polylactic acid, D-polylactic acid, polyglycolic acid, polycaprolactone, polyamide, polyterephthalic acid, ethylene glycol, polyether block polyamide, high-density polyethylene, thermoplastic polyurethane elastomer, polydimethylsiloxane, parylene, epoxy resin, polyamide-imide, polylactic acid, polyterephthalate, SU8 photoresist, silicone and silicone rubber.

11. A method for preparing an electrode, characterized in that, The method includes: A first insulating layer is provided, the first insulating layer comprising a first carbonizable material; The focus of the first laser beam is positioned on the upper surface of the first insulating layer. The first laser beam is configured to have a light intensity in the focused region that is higher than the first multiphoton absorption threshold of the first carbonizable material, and a light intensity in the non-focused region that is lower than the first multiphoton absorption threshold of the first carbonizable material. The focal point of the first laser beam is scanned along a path located on the upper surface of the first insulating layer, causing the first carbable material of the first insulating layer along the path to undergo multiphoton absorption and carbonization under the irradiation of the first laser beam, thereby forming a conductive line on the upper surface of the first insulating layer; and A second insulating layer is formed on the first insulating layer on which the conductive lines are formed.

12. The method according to claim 11, characterized in that, The method further includes: Before forming the second insulating layer, a metal layer is formed on the first insulating layer on which the conductive lines are formed, and the metal layer is patterned to cover the conductive lines.

13. The method according to claim 12, characterized in that, The method further includes: Before forming the metal layer, the upper surface of the first insulating layer is subjected to plasma treatment.

14. The method according to claim 11, characterized in that, The method also includes one or more of the following: Before forming the second insulating layer, a functionalized molecular film is formed on the upper surface of the first insulating layer, so that the first insulating layer and the second insulating layer can be bonded together by the chemical bonding of the functionalized molecular film after the formation of the second insulating layer; or Before forming the second insulating layer, a photocurable adhesive is applied to the upper surface of the first insulating layer so that the first insulating layer and the second insulating layer can be bonded by curing the photocurable adhesive with ultraviolet light after the second insulating layer is formed; or After the second insulating layer is formed, the first insulating layer is bonded to the second insulating layer by thermo-press bonding or ultrasonic welding.

15. The method according to claim 11, characterized in that, The conductive line is a first conductive line, and the method further includes: A second conductive line is formed in the second insulating layer, the second conductive line being configured to extend at one end to the upper surface of the second insulating layer to provide an electrode site, and at the other end to connect to the first conductive line.

16. The method according to claim 15, characterized in that: The path is a first path, and the second conductive line is formed by scanning the focal point of a second laser beam along a second path extending between the upper surface of the second insulating layer and the first conductive line. The second insulating layer comprises a second carbable material. The second laser beam is configured to have an intensity higher than a second multiphoton absorption threshold of the second carbable material in the focused region and an intensity lower than the second multiphoton absorption threshold of the second carbable material in the unfocused region. The second conductive line is formed by depositing a conductive medium in a trench extending from the upper surface of the second insulating layer to the first conductive line, or The second conductive line is formed by a through-hole extending from the upper surface of the second insulating layer to the first conductive line, the through-hole being capable of receiving a conductive medium therein to form the second conductive line; or The method further includes forming a conductive plating layer on the electrode sites.

17. The method according to claim 11, characterized in that, The path is a first path, the conductive line is a first conductive line, and the method further includes: The focal point of the first laser beam is positioned inside the first insulating layer, and the focal point of the first laser beam is scanned along a third path located inside the first insulating layer, so that the first carbonizable material of the first insulating layer on the third path undergoes multiphoton absorption and carbonization under the irradiation of the first laser beam, thereby forming a third conductive line located inside the first insulating layer.

18. The method according to claim 11, characterized in that, The path is a first path, the conductive line is a first conductive line, the second insulating layer comprises a second carbonizable material, and the method further includes: The focus of the second laser beam is positioned inside the second insulating layer. The second laser beam is configured to have a light intensity in the focused region that is higher than the second multiphoton absorption threshold of the second carbideable material, and a light intensity in the non-focused region that is lower than the second multiphoton absorption threshold of the second carbideable material. The focus of the second laser beam is scanned along a fourth path located inside the second insulating layer, causing the second carbonizable material of the second insulating layer on the fourth path to undergo multiphoton absorption and carbonize under the irradiation of the second laser beam, thereby forming a fourth conductive line located inside the second insulating layer.

19. The method according to claim 11, characterized in that, The path is a first path, the first insulating layer is formed on the substrate, and the method further includes: The focus of the first laser beam is positioned on the lower surface of the first insulating layer facing the substrate, and the focus of the first laser beam is scanned along a fifth path located on the lower surface, such that the first carbideable material of the first insulating layer along the fifth path undergoes multiphoton absorption and carbonization under the irradiation of the first laser beam; and The stack of the first insulating layer, on which the conductive lines are formed on its upper surface and whose lower surface is at least partially carbonized, and the second insulating layer are separated from the substrate.

20. The method according to claim 11, characterized in that: The first laser beam is configured such that the first carbideable material has a transmittance of not less than 50% at the wavelength of the first laser beam; and / or The first laser beam is configured to enable the first carbideable material to undergo two-photon absorption, or is configured to enable the first carbideable material to undergo three-photon absorption; and / or The wavelength of the first laser beam is in the near-infrared band, or between 780 nanometers and 1064 nanometers; and / or The focused spot of the first laser beam has a diameter on the order of submicron to micrometer; and / or The first laser beam is configured to be focused by a lens with a numerical aperture between 0.8 and 1.4; and / or The scanning speed is between 10 micrometers per second and 100 micrometers per second; and / or The scan is performed 1 to 3 times along the path; and / or The first laser beam is configured as a femtosecond laser beam provided in pulse form, wherein: The pulse width of the femtosecond laser beam is between 50 femtoseconds and 200 femtoseconds, and / or The repetition frequency of the femtosecond laser beam is between 100 kHz and 1 MHz, and / or The single-pulse energy of the femtosecond laser beam is between 1 microjoule and 10 microjoules; and / or The first carbonizable material includes at least one of the following: polyimide, polylactic acid-glycolic acid copolymer, cellulose, chitosan, hyaluronic acid, collagen, gelatin, sodium alginate, polyurethane, polytetrafluoroethylene, expanded polytetrafluoroethylene, polylactic acid, L-polylactic acid, D-polylactic acid, polyglycolic acid, polycaprolactone, polyamide, polyterephthalic acid, ethylene glycol, polyether block polyamide, high-density polyethylene, thermoplastic polyurethane elastomer, polydimethylsiloxane, poly(p-xylene), epoxy resin, polyamide-imide, polylactic acid, polyterephthalate, SU8 photoresist, silicone, and silicone rubber.

21. An electrode, characterized in that, The electrode includes: An insulating layer, the insulating layer comprising a carbonizable material; and The conductive lines located inside the insulating layer are formed by scanning a path located inside the insulating layer with the focus of a laser beam, causing the carbonizable material of the insulating layer on the path to carbonize under the irradiation of the laser beam through multiphoton absorption. The laser beam is configured to have a light intensity in the focused region that is higher than the multiphoton absorption threshold of the carbonizable material, and a light intensity in the non-focused region that is lower than the multiphoton absorption threshold of the carbonizable material.

22. The electrode according to claim 21, characterized in that, The electrode is prepared by the method according to any one of claims 1 to 20.

23. A method for preparing a flexible electrode, characterized in that, The method includes: Provide a polyimide layer; The focal point of a near-infrared femtosecond pulsed laser beam is positioned within the polyimide layer. The near-infrared femtosecond pulsed laser beam is configured to have an intensity higher than the two-photon absorption threshold of the polyimide in the focused region and an intensity lower than the two-photon absorption threshold of the polyimide in the unfocused region; and The focal point of the near-infrared femtosecond pulsed laser beam is scanned along a path located inside the polyimide layer, causing the polyimide in the polyimide layer on the path to undergo two-photon absorption and carbonization under the irradiation of the near-infrared femtosecond pulsed laser beam, thereby forming a conductive circuit located inside the polyimide layer.

24. A flexible electrode, characterized in that, The flexible electrode includes: Polyimide layer; and The conductive lines located inside the polyimide layer are formed by scanning a path located inside the polyimide layer with the focal point of a near-infrared femtosecond pulsed laser beam, causing the polyimide in the polyimide layer on the path to undergo two-photon absorption and carbonization under the irradiation of the near-infrared femtosecond pulsed laser beam. The near-infrared femtosecond pulsed laser beam is configured to have a light intensity higher than the two-photon absorption threshold of the polyimide in the focused region and a light intensity lower than the two-photon absorption threshold of the polyimide in the non-focused region.

25. An electrode array, characterized in that, The electrode array includes a plurality of electrodes, each of which is an electrode according to claim 21 or 22, or a flexible electrode according to claim 24, or an electrode prepared by the method according to any one of claims 1 to 20, or a flexible electrode prepared by the method according to claim 23.

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