A wide-adaptable electrode array with an outer dense and inner sparse radial anisotropic topology

Abstract

The application discloses a wide-adaptability electrode array with an outer dense and inner sparse radial heterogeneous topology, and belongs to the field of biomedical engineering. The electrode array comprises an electrode substrate and an electrode microneedle array. The electrode microneedle array is composed of a plurality of long and short electrode microneedles. The long electrode microneedles are uniformly arranged on the electrode substrate in a circumferential direction, thereby dividing the electrode substrate into a plurality of equal regions in the circumferential direction. The plurality of short electrode microneedles are evenly distributed in each region, and the short electrode microneedles in each region are uniformly arranged on the corresponding electrode substrate of the region. The long and short electrode microneedles are both composed of an electrode core and an insulating layer wrapping the electrode core. The top ends of the long and short electrode microneedles are exposed to the electrode core, and the electrode core is also exposed on the long electrode microneedle at a position away from the bottom end of the long electrode microneedle by a preset length. The application provides a more efficient and blind area smaller neural interface scheme for a visual prosthesis.

Description

Technical Field

[0001] This invention belongs to the field of biomedical engineering, specifically relating to a versatile electrode array with a radially heterogeneous topology that is dense on the outside and sparse on the inside. Background Technology

[0002] Visual prostheses are an important rehabilitation method to help blind people regain visual function. As a core component of neural interfaces, the performance of electrodes directly determines the final quality of artificial vision. The design of the electrode structure, especially its array arrangement and geometric matching with the optic nerve tissue, plays a crucial role in improving the coverage, resolution, and long-term stability of nerve stimulation after implantation.

[0003] However, existing optic nerve electrode technologies still have significant limitations in terms of coverage. While invasive electrodes (such as the Utah array, TIME (Translaminar Intracortical Microelectrode) electrodes, and LIFE (Long Intracortical Flexible Electrode) electrodes can penetrate deep into the nerve to produce high resolution, their traditional structural designs often fail to fully consider the anatomical characteristics of the optic nerve. Since the optic nerve cross-section is typically circular or elliptical, while most existing mainstream invasive electrodes use a rectangular grid arrangement, this severe geometric mismatch makes it difficult for the electrodes to effectively cover the peripheral regions of the optic nerve. This not only creates a large stimulation blind zone in the circumferential direction, severely limiting the recovery of peripheral vision, but also, although some specialized electrodes such as OpticSELINE have improved stability, their coverage area remains limited, failing to achieve a high proportion of coverage of the optic nerve cross-section.

[0004] More importantly, optic nerve tissue is extremely fragile. Simply increasing the number of electrodes or increasing the point stimulation current to improve coverage can easily cause irreversible nerve damage. Therefore, there is an urgent need for a new electrode array to break through the limitations of the traditional rectangular layout and construct an electrode array that highly conforms to the cylindrical shape of the optic nerve without increasing electrode invasiveness. This would solve the technical bottlenecks of poor geometric matching and insufficient coverage of traditional piercing electrodes, providing a more efficient neural interface solution with smaller blind spots for visual prostheses. Summary of the Invention

[0005] To address the problems in the prior art, the present invention provides a versatile electrode array with a radially heterogeneous topology that is dense on the outside and sparse on the inside.

[0006] The technical solution of the present invention is as follows: This invention discloses a versatile electrode array with a radially heterogeneous topology of dense outer layer and sparse inner layer. The electrode array is used to electrically stimulate nerve fibers on the surface of the intraorbital segment of the optic nerve near the retina at the back of the eyeball, thereby activating and transmitting signals across the entire optic nerve. The electrode array includes an electrode base and an electrode microneedle array. The electrode base is annular and designed to adhere to the surface of the optic nerve. The electrode microneedle array includes multiple long electrode microneedles and multiple short electrode microneedles. The long electrode microneedles are uniformly arranged circumferentially on the electrode base, dividing the electrode base into multiple equal regions. The multiple short electrode microneedles are evenly distributed within each region, and the short electrode microneedles within each region are uniformly arranged along the electrode base corresponding to that region. Both the long and short electrode microneedles are arranged radially along the electrode base. Both the long electrode microneedle and the short electrode microneedle consist of a battery cell and an insulating layer that encloses the battery cell. The battery cell is exposed at the top of both the long electrode microneedle and the short electrode microneedle. At the same time, the battery cell is exposed on the long electrode microneedle at a predetermined length from the bottom of the long electrode microneedle. This predetermined length is equal to the length of the short electrode microneedle.

[0007] Furthermore, the length ratio of the long electrode microneedle to the short electrode microneedle is 7:4-11:1; the ratio between the length of the long electrode microneedle and the radius of the electrode substrate is 0.55:1-1:1.

[0008] Furthermore, the length of the short electrode microneedle is 100-400 μm.

[0009] Furthermore, the length of the long electrode microneedle is 700-1100 μm.

[0010] Furthermore, the exposed battery cell is 10-30 μm in length.

[0011] Furthermore, the electrode substrate is made of a biocompatible material, namely silicone.

[0012] Furthermore, the battery cell is made of a platinum-iridium alloy, and the insulating layer is made of a biocompatible material, namely silicone.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention, by adopting an innovative structure of "circular base-radial microneedles", achieves a high degree of fit between the electrode layout and the anatomical morphology of the optic nerve cylinder, fundamentally solving the problem of stimulation blind zone at the edge of the circular nerve cross section of traditional rectangular array electrodes, and improving the mechanical stability and biocompatibility after implantation.

[0014] In terms of stimulation efficacy, this invention utilizes a combined strategy of "long and short needles" and "single needle multi-point stimulation," employing a three-dimensional layout where the tip of the long needle penetrates deep into the center, and the middle section of the long needle and the tip of the short needle cover the superficial layer. This achieves a high proportion of activation of nerve fibers across the entire optic nerve without increasing the number of implanted needles or invasiveness.

[0015] Furthermore, this invention relies on a heterogeneous topology scheme of "dense outer layer and sparse inner layer" (such as 4 channels in the inner layer and 12 channels in the outer layer) determined by multi-physics coupling simulation to achieve the optimal configuration of stimulation resources. While keeping the total number of channels unchanged, it can significantly improve the activation coverage by about 25.4% compared with the traditional rectangular layout, providing a wider field of view, higher resolution and more clinically applicable neural interface scheme for visual prostheses. Attached Figure Description

[0016] Figure 1 This is a three-dimensional schematic diagram of a universal electrode array according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the electrode layout and activation range of a traditional rectangular array of puncture electrodes on the cross-section of the optic nerve. Figure 3 This is a schematic diagram of the electrode layout and activation range of the universal electrode array of the present invention on the cross-section of the optic nerve; Figure 4 This is a schematic diagram comparing the activation coverage of the activated axon area with the electrode arrangement scheme of the present invention, using a conventional electrode arrangement scheme and the electrode arrangement scheme of the present invention. Figure 5 This is a diagram showing the electrode distribution and activation coverage of a universal electrode array in another embodiment of the present invention. Figure 6 This is a schematic diagram of the electrode distribution and activation coverage of Comparative Example 1; Figure 7 This is a schematic diagram of the electrode distribution and activation coverage of Comparative Example 2; Figure 8 This is a schematic diagram of the electrode distribution and activation coverage of Comparative Example 3. Detailed Implementation

[0017] The present invention will be further described and illustrated below with reference to specific embodiments. The embodiments described are merely examples of the content of this disclosure and do not limit the scope of the invention. The technical features of each embodiment in the present invention can be combined accordingly, provided that there is no mutual conflict.

[0018] This invention proposes a design for a versatile electrode array with a radially heterogeneous topology that is dense on the outside and sparse on the inside. This design can effectively solve the problem of mismatch between the geometry of traditional rectangular grid electrodes and the circular optic nerve cross-section, and significantly improve the effective coverage of optic nerve fibers by the visual prosthesis.

[0019] This invention employs a "ring-shaped base-radial microneedles" structural design: the ring-shaped electrode base adapts to and wraps around the peripheral shape of the optic nerve, providing excellent mechanical stability; compared to other geometric base shapes, the circular base naturally conforms to the cylindrical anatomical structure of the optic nerve, completely avoiding tissue compression and poor adhesion that may be caused by irregular corners; the radially distributed array of electrode microneedles points towards the center, ensuring that the electrode points naturally form a concentric stimulation field that highly matches the cross-section of the optic nerve after implantation. In practical applications, this array is designed to adhere to the surface of the optic nerve, closer to the retina, behind the posterior end of one eyeball on each side, requiring only one implantation per optic nerve to establish a complete neural interface.

[0020] This invention proposes a layered insertion strategy combining long and short electrode microneedles to achieve uniform activation of the entire optic nerve cross-section: the inner layer of long electrode microneedles is inserted into the deep part of the nerve to cover the central area; the outer layer of short electrode microneedles is inserted into the superficial part of the nerve to cover the edge area, thereby eliminating the huge stimulation blind zone in the circumferential direction of traditional electrodes.

[0021] To ensure good biocompatibility and conductivity, the electrode substrate is made of biocompatible materials (such as silicone), and the internal electrode core (the main supporting structure) is made of conductive materials with strong charge injection capabilities, such as platinum-iridium alloy. Its outer surface is wrapped with a biocompatible insulating layer. The insulating layer is removed only at specific discharge sites to expose the internal conductive material for precise application of electrical stimulation.

[0022] Figure 1 This is an embodiment of the present invention, which is a schematic diagram of an insertable electrode array for an optic nerve prosthesis. (See diagram below.) Figure 1 As shown, it includes an electrode base 1 and an electrode microneedle array. Considering the average anatomical size of the adult optic nerve, the inner radius of the base is approximately 1340 μm, the thickness is 50–150 μm, and the width is 50–150 μm. The electrode microneedle array includes multiple long electrode microneedles 3 and multiple short electrode microneedles 2. The tail of the short electrode microneedle 2 is connected to the electrode base 1, with a length of 100–400 μm, and the tip of the microneedle is exposed for 10–30 μm for precise application of electrical stimulation. The tail of the long electrode microneedle 3 is connected to the base, with a length of 700–1100 μm, and its tip and a distance of 100–400 μm from the tail are exposed for 10–30 μm for precise application of electrical stimulation. That is, the ratio between the exposed length and the length of the short electrode microneedle is 1:110–3:70.

[0023] Specifically, long electrode microneedles 3 are uniformly arranged circumferentially on the electrode substrate 1, dividing the annular electrode substrate 1 into multiple equal arc segments. Multiple short electrode microneedles 2 are evenly distributed on each arc segment, and the short electrode microneedles 2 on each arc segment are uniformly arranged along the electrode substrate corresponding to that arc segment. That is, firstly, long electrode microneedles 3 are uniformly arranged circumferentially on the electrode substrate 1. Then, due to this arrangement, the annular electrode substrate 1 is divided into multiple arc segments, and all short electrode microneedles 2 are evenly distributed on each arc segment. That is, the number of short electrode microneedles 2 on each arc segment is the total number of short electrode microneedles 2 divided by the total number of arc segments. Finally, all short electrode microneedles 2 on each arc segment are uniformly arranged along the electrode substrate corresponding to that arc segment.

[0024] Both the long electrode microneedle 3 and the short electrode microneedle 2 point radially toward the center of the annular electrode substrate. Both the long electrode microneedle 3 and the short electrode microneedle 2 consist of a battery cell and an insulating layer enclosing the battery cell. The tips of both the long electrode microneedle 3 and the short electrode microneedle 2 expose a 10-30 μm battery cell. At the same time, a 10-30 μm battery cell is exposed on the long electrode microneedle 3 at a position 100-400 μm away from the bottom of the long electrode microneedle 3.

[0025] Define the number of inner layer electrodes as The number of outer electrodes is The total number of electrodes is The electrode array covered by this invention satisfies < .

[0026] In this embodiment, to balance coverage and the risk of tissue damage, the total number of electrodes in the electrode array is limited to 16. The inner layer (tip of the long electrode microneedle) has 4 electrodes, and the outer layer (tip of the short electrode microneedle and the tail end of the long electrode microneedle) has 12 electrodes, used to apply electrical stimulation. The inner layer electrodes consist of the exposed portion of the long electrode microneedle tip, and are distributed at 90 degrees to each other on the optic nerve cross-section, aiming to penetrate deep into the optic nerve and cover the central region of the optic nerve cross-section. The outer layer electrodes consist of the exposed portion of the short electrode microneedle tip and the exposed portion of the long electrode microneedle at 100–400 μm from the tail end, and are distributed at 30 degrees to each other on the optic nerve cross-section, aiming to penetrate superficially into the optic nerve, forming a dense ring-shaped stimulation network in the superficial optic nerve tissue, covering the edge region of the optic nerve cross-section.

[0027] The specific long and short electrode distribution topology in this embodiment is not based on simple geometric equalization, but rather optimized using a method of multi-physics coupling and neurodynamics co-simulation. This process incorporates electrode position parameters, the activation status of myelinated axons in NEURON, and extracellular potential calculated by COMSOL into a closed loop. An optimizer is built using Python, with the optimization objective being to maximize axon activation coverage. The final output indicates that, compared to the traditional simple uniform electrode distribution topology, the heterogeneous distribution topology of this embodiment is the globally optimal solution. On the optic nerve cross-section, the distribution density of outer layer electrodes is higher than that of inner layer electrodes. This "sparse in the center, dense around the periphery" layout aims to utilize the limited number of channels to preferentially fill the stimulation blind spots at the circumferential edge, while ensuring the connectivity of the central visual field through the inner layer of long microneedles.

[0028] To verify the effectiveness of the 16-channel dual-layer electrode array designed in the above embodiments, especially its advantages in coverage, this invention uses a multi-physics coupling and neurodynamics co-simulation method for evaluation.

[0029] A three-dimensional finite element model (FEM) of the optic nerve was constructed using COMSOL software. The optic nerve diameter was set to 2.68 mm in the model, and corresponding conductivity parameters were assigned to the nerve bundle, nerve sheath, and surrounding cerebrospinal fluid. The double-layered ring electrode (16 channels) of this invention and a conventional 4x4 rectangular grid electrode were implanted into the model, respectively, and the extracellular potential distribution after applying current to the electrodes was calculated. The electrode distribution methods of the conventional electrode array and the novel electrode array used in this invention on the cross-section of the optic nerve are as follows: Figure 2 and Figure 3 As shown. Figure 2 and Figure 3 In the figure, reference numeral 4 represents a cross-section of the human optic nerve, reference numeral 5 represents the electrode array structure proposed in this invention, and reference numeral 6 represents the stimulation site on the electrode microneedle.

[0030] Using the NEURON simulation environment, a myelinated axon model was constructed based on the MRG (McIntyre–Richardson-Grill) model, with 10,000 axons randomly distributed on the optic nerve cross section to simulate real nerve fiber bundles.

[0031] Extracellular potential data calculated by COMSOL is imported into the NEURON environment via a Python interface and used as an external stimulus on each axon model. The change in axon membrane potential is calculated to determine whether it is activated (generating an action potential). The proportion of activated axons to the total number of axons is used as an indicator to quantify electrode coverage (i.e., activation coverage).

[0032] Simulation results show that the electrode array proposed in this embodiment exhibits a significant advantage in activation coverage on optic nerve fibers.

[0033] like Figure 4 As shown, the simulation assumes that the stimulation current values ​​applied to a single electrode channel are strictly equal for both methods. Under this premise, for the traditional 4x4 rectangular grid insertion electrode, due to the mismatch between its rectangular geometric layout and the circular optic nerve cross-section, and the uniform electrode needle length, a large area of ​​inactive "blind zone" exists in the circumferential edge region of the optic nerve. Under the set stimulation threshold conditions, it successfully activated only 5756 axons out of 10000 randomly distributed axons, with an activation coverage rate of only 57.56%.

[0034] In contrast, the 16-channel dual-layer concentric electrode array designed in this embodiment achieves full coverage of the optic nerve cross-section through a unique strategy of "combining long and short needles" and "single-needle multi-point stimulation": four long electrode microneedles with a length of 700-1100 μm penetrate deep into the center of the optic nerve, effectively activating deep axons; 12 outer electrode points (composed of the tips of short electrode microneedles and the exposed cores of long electrode microneedles at a distance of 100-400 μm from the tail) form a dense ring-shaped stimulation network in the superficial region below the optic nerve sheath, filling the marginal blind spots. Statistics show that the electrode array in this embodiment successfully activated 7220 axons, increasing the activation coverage rate to 72.2%.

[0035] Data shows that, compared to traditional methods, this invention increases the number of effectively activated nerve fibers by approximately 25.4% while maintaining the same number of electrode channels and without significantly increasing implantation invasiveness. This result quantitatively confirms that the specific spatial layout of 4 electrodes in the inner layer and 12 electrodes in the outer layer (including long needle reuse points), with a sparse center and dense periphery, can greatly improve the visual field and resolution of the visual prosthesis. The comparison results are as follows... Figure 4 As shown.

[0036] This invention is not only applicable to For the case where the value is 16, for any value less than or equal to 16 As long as the non-uniform distribution principle of "sparse in the center and dense around the edges" is followed, it falls within the protection scope of this invention.

[0037] Example 2 For example, when the total number of electrodes When the value is 12, three long electrode microneedles are used, each exposing one electrode point at its tip, distributed at 120° intervals on a 360° circumference, resulting in four inner layer electrodes. Three short electrode microneedles are also used, resulting in nine outer layer electrode points, consisting of six short electrode microneedles with their tip electrodes and three long electrode microneedles with electrodes exposed at 100–400 μm from the tail. These outer layer stimulation points are evenly distributed at 40° intervals on the circumference, forming a closed, shallow stimulation ring. Their distribution… Figure 5 As shown.

[0038] Depend on Figure 5 Simulation results show that, under the same current stimulation, the 12-electrode channel scheme achieves an activation coverage of approximately 55.8% in a model with 10,000 axons. Although the total number of electrodes is reduced by four compared to the 16-electrode channel scheme, its activation coverage is only slightly different from that of the traditional 16-channel rectangular array (57.56%). This further confirms the universal advantage of the proposed heterogeneous layout scheme of "sparse at the center and dense around the perimeter" in improving coverage regardless of the total number of channels.

[0039] To further demonstrate the superiority of the heterogeneous electrode layout design (4 electrodes in the inner layer and 12 electrodes in the outer layer) proposed in this invention, under the premise of maintaining a total number of channels of 16 and the applied current being constant, the following three sets of comparative examples were set up for coverage simulation comparison.

[0040] Comparative Example 1 This comparative example uses an evenly distributed electrode layout, with 8 electrodes in the inner layer and 8 electrodes in the outer layer, as shown in the figure. Figure 6 As shown. Simultaneously from Figure 6 The simulation results show that the overall activation coverage of this electrode layout scheme is 63.4%.

[0041] This is because, although increasing the number of inner layer electrode points theoretically improves the sampling rate in the central region, the reduction in outer layer electrode points (only 8) results in excessively large spacing along the circumferential direction at the edge of the optic nerve, leading to a noticeable "jagged" blind spot in the peripheral region. This indicates that simply distributing electrode points evenly cannot simultaneously meet the high coverage requirements at the edges.

[0042] Comparative Example 2 This comparative example uses a non-optimal and asymmetrical electrode layout, with 6 electrodes in the inner layer and 10 electrodes in the outer layer. The electrode distribution is as follows: Figure 7 As shown. Simultaneously from Figure 7 The simulation results show that the overall activation coverage of this electrode layout scheme is 66.65%.

[0043] Compared to the evenly distributed electrode pattern, this scheme improves the overall activation rate by increasing the number of outer electrodes, but it is still lower than the optimal solution of this invention. Experiments showed that when there are more than 4 inner electrodes, the stimulation field in the central region overlaps, resulting in redundancy in charge injection capability, while the 10 points on the outer layer still cannot completely eliminate the activation gap at the circumferential edge.

[0044] Comparative Example 3 This comparative example uses an electrode layout with extremely dense edge electrodes, specifically two electrodes in the inner layer and fourteen electrodes in the outer layer. The electrode distribution is as follows: Figure 8 As shown. Simultaneously from Figure 8 The simulation results show that the overall activation coverage of this electrode layout scheme is 60.7%.

[0045] While this approach tilts the electrode distribution towards the edges, the presence of only two electrodes in the inner layer prevents the activation field in the central region of the optic nerve cross-section from connecting, resulting in a distinct linear strip-shaped inactive area running through the center of the plane. This means that although the peripheral areas are filled to some extent, the central visual field exhibits severe "central scotomas" or "central gaps," significantly disrupting the integrity of visual reconstruction. The effect is far inferior to the electrode layout proposed in this invention, which uses four electrodes in the inner layer and twelve electrodes in the outer layer.

[0046] This invention proposes a microneedle array electrode based on concentric radial distribution. This design aims to overcome the limitations of traditional rectangular layouts and, without increasing electrode invasiveness, solve the technical bottlenecks of poor geometric matching and insufficient coverage of traditional puncture electrodes by constructing an electrode array that highly conforms to the cylindrical shape of the optic nerve. This provides a more efficient neural interface solution for visual prostheses with smaller blind spots.

[0047] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A versatile electrode array with a radially heterogeneous topology of dense outer layer and sparse inner layer, the electrode array being used to electrically stimulate nerve fibers on the surface of the intraorbital segment of the optic nerve near the retina at the posterior end of the eyeball, thereby achieving activation and signal transduction across the entire optic nerve profile; characterized in that, The electrode array includes an electrode substrate and an electrode microneedle array; The electrode base is circular and designed to fit the surface of the optic nerve. The electrode microneedle array includes multiple long electrode microneedles and multiple short electrode microneedles. The long electrode microneedles are uniformly arranged on the electrode base in the circumferential direction, dividing the electrode base into multiple equal regions in the circumferential direction. The short electrode microneedles are evenly distributed in each region, and the short electrode microneedles in each region are evenly arranged along the electrode substrate corresponding to that region; the long electrode microneedles and the short electrode microneedles are both arranged along the radial direction of the electrode substrate. Both the long electrode microneedle and the short electrode microneedle consist of a battery cell and an insulating layer that encloses the battery cell. The battery cell is exposed at the top of both the long electrode microneedle and the short electrode microneedle. At the same time, the battery cell is exposed on the long electrode microneedle at a predetermined length from the bottom of the long electrode microneedle. This predetermined length is equal to the length of the short electrode microneedle.

2. The electrode array according to claim 1, characterized in that, The length ratio of long electrode microneedles to short electrode microneedles is 7:4-11:1; the ratio between the length of long electrode microneedles and the radius of the electrode substrate is 0.55:1-1:

1.

3. The electrode array according to claim 1, characterized in that, The length of the short electrode microneedles is 100-400 μm.

4. The electrode array according to claim 1, characterized in that, The length of the long electrode microneedle is 700-1100 μm.

5. The electrode array according to claim 1, characterized in that, The exposed battery cell is 10-30 μm in length.

6. The electrode array according to claim 1, characterized in that, The electrode substrate is made of a biocompatible material, namely silicone.

7. The electrode array according to claim 1, characterized in that, The battery cell is made of platinum-iridium alloy, and the insulating layer is made of a biocompatible material, namely silicone.

8. The electrode array according to claim 1, characterized in that, The inner radius of the annular electrode substrate is 500-2000um, the thickness is 50-150um, and the width is 50-150um.

9. The electrode array according to claim 1, characterized in that, The total number of exposed cells in the long electrode microneedles and short electrode microneedles is equal to 16.

10. The electrode array according to claim 1, characterized in that, The number of short electrode microneedles is 8, and the number of long electrode microneedles is 4.

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