阅读说明：本技术 一种基于微型led阵列的光神经接口优化设计方法 (Optical neural interface optimization design method based on micro LED array ) 是由 康晓洋 乐松 张圆 王爱萍 刘鲁生 于 2021-08-17 设计创作，主要内容包括：本发明属于光遗传学技术领域,具体为一种基于微型LED阵列的光神经接口优化设计方法。本发明利用吸收层来模拟神经组织,分析光神经接口中微型LED阵列的辐照度分布,通过改变吸收层间距、LED尺寸大小和排列间隔,得到有效光刺激体积与作用范围,得到光神经接口的数学模型,为光神经接口中微型LED阵列设计提供依据；具体包括：建立LED阵列的仿真模型、设置并定义光学材料、进行光线追迹、对模拟结果进行平滑化处理,最后归纳总结得出数学模型,从而在提高光神经接口的空间分辨率和避免串扰方面提供设计指导。(The invention belongs to the technical field of optogenetics, and particularly relates to an optical neural interface optimization design method based on a micro LED array. The absorption layer is utilized to simulate nerve tissues, the irradiance distribution of the micro LED array in the optical nerve interface is analyzed, the effective light stimulation volume and action range are obtained by changing the interval of the absorption layer, the size of the LED and the arrangement interval, a mathematical model of the optical nerve interface is obtained, and a basis is provided for the design of the micro LED array in the optical nerve interface; the method specifically comprises the following steps: establishing a simulation model of the LED array, setting and defining optical materials, performing ray tracing, smoothing a simulation result, and finally summarizing to obtain a mathematical model, thereby providing design guidance in the aspects of improving the spatial resolution of the optical neural interface and avoiding crosstalk.)

1. An optical neural interface optimization design method based on a micro LED array comprises the following specific steps:

(1) building a simulation model of the optical neural interface LED array; specifically, various components are simulated by using geometric bodies with different shapes, including: simulating an optical neural interface substrate by using a square geometry, simulating a micro LED array by using a square or cylindrical array with the same physical size as the micro LED, and simulating neural tissue by using a thin plate;

(2) setting an optical material according to the simulation model; specifically, the upper surfaces of the square block and the cylindrical array geometric body of the simulated micro LED array are surface light sources, and the lower surface of the thin plate geometric body of the simulated nerve tissue is an ideal absorption layer without scattering and reflection;

(3) defining light source parameters according to a simulation model, wherein:

defining the central wavelength of the LED light emission to be 460 nm;

the optical power density of the surface light source is defined to be 300-400mW/mm²；

Defining the total light number range of each LED geometric body model to be 1-100 ten thousand;

(4) processing and analyzing the simulation result, including smoothing and regional coordinate processing on the irradiance/illuminance analysis graph; wherein:

setting a minimum absorption threshold of irradiance to 1mW/mm²；

Setting the range of pixel points of the analysis graph to be 10-200;

(5) obtaining a mathematical model of the micro LED array design, and guiding the array design by adopting different mathematical models for LEDs with different shapes and sizes; the specific expression form is as follows:

the mathematical model for two circular surface light sources is:

the mathematical model for two square surface light sources is:

wherein λ is a parameter representing the rate of change of the effective illuminated area per unit light source perimeter and per unit absorption layer spacing, the value of which is determined by the light source characteristics, and R₁And R₂Respectively representing the radii of the effective illumination circles, r, of the two micro-LEDs₁And r₂Respectively represent the radii of two micro LED surface light sources, a₁And a₂，b₁And b₂Respectively representing the length and width of two micro LED surface light sources, H₁And H₂Respectively represent the vertical spacing between the upper surfaces of the two micro LEDs and the nervous tissue, L and L_minRespectively representing the center-to-center distance of two circular surface light sources and the minimum center-to-center distance of two square surface light sources arranged in the same horizontal plane.

Technical Field

The invention belongs to the technical field of optogenetics, and particularly relates to an optimal design method of an optical neural interface.

Background

The optogenetic technology is a new neural regulation and control means combining genetic engineering and optical technology, and greatly promotes the development of neuroscience. And the optical neural interface with the functions of neural regulation and neural signal recording is an essential tool in optogenetics. The light transmission mode of the optical nerve interface is developed by a laser fiber optical pole, a waveguide coupling optical pole, an LD/LED integrated optical pole and a micro LED implantation and fitting optical pole, and the micro LED is widely applied and integrated in the optical nerve interface used in optogenetics because of the tiny size and the excellent luminous performance. Therefore, the propagation and action processes of the light emitted by the micro LED in the brain tissue are known, and the real implantation state of the device is simulated by creating a physical model, so that the design cycle time is greatly reduced, and the design of the optical neural interface device is optimized, thereby having remarkable significance.

The micro LED array-based neural interface for the field of optogenetics comprises a flexible circuit board substrate, a micro LED array arranged on the substrate, and corresponding neural tissue. Two major challenges are currently faced: firstly, how to reduce the size of the device as much as possible while improving the optical stimulation spatial resolution; and secondly, the crosstalk of the light field of each unit is avoided while the integration density of the micro LED is improved. Therefore, it is urgently needed to understand the propagation process of light generated by the micro LEDs in brain tissue, eliminate optical field crosstalk between the micro LED array units, and further optimize the design of the optical neural interface device, so as to effectively improve the optical stimulation resolution of the optical neural interface used in the field of optogenetics, which is helpful to reduce the size of the device and facilitate surgical implantation.

Disclosure of Invention

The invention aims to provide an optical neural interface optimization design method based on a micro LED array, so as to improve the spatial resolution of the optical neural interface and avoid optical field crosstalk between micro LED array units.

The optical neural interface optimization design method based on the micro LED array provided by the invention has the advantages that the absorption layer is utilized to simulate neural tissues, the irradiance distribution of the micro LED array in the optical neural interface is analyzed, the effective light stimulation volume and action range are obtained by changing the distance between the absorption layers, the size and the arrangement interval of the LEDs, a mathematical model of the optical neural interface is obtained, and a basis is provided for the design of the micro LED array in the optical neural interface; the method comprises the following specific steps:

(1) building a simulation model of the optical neural interface LED array; specifically, various components are simulated by using geometric bodies with different shapes, including: simulating an optical neural interface substrate by using a square geometry, simulating a micro LED array by using a square and a cylindrical array which have the same physical size with the micro LED, and simulating neural tissue by using a thin plate;

specifically, for example, an optical neural interface substrate is simulated with a square geometry of 3mm × 3mm × 0.6mm size, a micro LED array is simulated with a square and cylindrical array in conformity with the physical dimensions of the micro LEDs, the three dimensions being 90 μm × 110 μm × 50 μm, 220 μm × 270 μm × 50 μm, and 320 μm × 390 μm × 50 μm, respectively, neural tissue is simulated with a thin plate absorption layer, the absorption layer adopting the dimensions of 600 μm × 600 μm × 10 μm and 3000 μm × 3000 μm × 10 μm, respectively; and so on.

(2) Setting an optical material according to the simulation model; specifically, the upper surfaces of the square and cylindrical array geometric bodies for simulating the micro LED array are surface light sources, and the lower surfaces of the thin plate geometric bodies for simulating the nerve tissue are ideal absorption layers without scattering and reflection.

(3) Defining light source parameters according to a simulation model, wherein:

defining the central wavelength of LED light emission as 460nm, which is determined by the effective blue light wavelength range in the field of optogenetics and the simulated commercial LED light emission wavelength, wherein the model of the miniature LED can be Cree C460TR 2432;

the optical power density of the surface light source is defined to be 300-400mW/mm²This is determined by the range of optical power densities of the micro LEDs being simulated;

the total number of rays defining each LED geometry model is in the range of 1-100 ten thousand, which is determined by the light source characteristics of the simulated micro-LEDs, and irradiance distributions beyond this range can affect the simulation accuracy of the simulation.

(4) And processing and analyzing the simulation result, including smoothing and regional coordinate processing on the irradiance/illuminance analysis graph, wherein:

setting a minimum absorption threshold of irradiance to 1mW/mm²The threshold value is the minimum optical power density value which guarantees the effectiveness of optical stimulation in the technical field of optogenetics and is also a critical value which is used for judging whether an illumination area is effective or not;

the range of the pixel points of the analysis chart is set to be 10-200, the range is determined by the light source characteristics of the micro LED simulated by the model, and the simulation result beyond the range is distorted.

(5) The method is used for obtaining a mathematical model of the micro LED array design, and guiding the array design by adopting different mathematical models for LEDs with different shapes and sizes, and comprises the following specific processes: changing the vertical spacing of the absorption layers, gradually increasing from 5 mu m to 100 mu m, simulating the thickness range of a real PDMS packaging layer, changing the size of a model simulating the micro LED under the condition of keeping the light source characteristics and the light power density unchanged, obtaining the effective illumination range and distribution under different absorption layer spacings and different micro LED sizes, and obtaining a mathematical model through repeated iterative analysis and summarization. The specific expression form is as follows:

the mathematical model for two circular surface light sources is:

the mathematical model for two square surface light sources is:

wherein λ is a parameter representing the rate of change of the effective illuminated area per unit light source perimeter and per unit absorption layer spacing, the value of which is determined by the light source characteristics, and R₁And R₂Respectively representRadius of effective illumination circle, r, of two kinds of micro-LEDs₁And r₂Respectively represent the radii of two micro LED surface light sources, a₁And a₂，b₁And b₂Respectively representing the length and width of two micro LED surface light sources, H₁And H₂Respectively represent the vertical spacing between the upper surfaces of the two micro LEDs and the nervous tissue, L and L_minRespectively representing the center-to-center distance of two circular surface light sources and the minimum center-to-center distance of two square surface light sources arranged in the same horizontal plane.

The invention utilizes the absorption layer to simulate the nerve tissue, analyzes the irradiance distribution of the micro LED array in the optical nerve interface, obtains the effective light stimulation volume and action range by changing the interval of the absorption layer, the size of the LED and the arrangement interval, and provides a basis for the design of the micro LED array in the optical nerve interface.

Drawings

Fig. 1 is a 3 × 3 micro LED array model diagram of the optical neural interface.

FIG. 2 is a graph of a 10 thousand ray trace model with an absorber layer added.

Fig. 3 is a graph of irradiance analysis of a single LED illumination.

Fig. 4 is an irradiance analysis plot after smoothing and region-coordinating processing.

Fig. 5 is a 3D irradiance aided illustration of a single LED lighting.

Fig. 6 is a contour plot and a profile curve of irradiance.

Fig. 7 is an irradiance analysis chart of nine LEDs simultaneously.

Fig. 8 is a 3D irradiance aided illustration of nine LED lighting.

FIG. 9 is a line graph of effective irradiance range versus vertical spacing for different size LEDs.

Fig. 10 is a trend line graph of effective irradiation range versus vertical spacing for circular LEDs of different diameters.

Detailed Description

The present invention is further described below by using specific embodiments, in which a general mathematical model is obtained by performing analysis processing after ray tracing based on a built physical model and summarizing rules and giving an optimized design process, but the scope of the present invention is not limited to the following embodiments.

Example 1

The irradiance analysis process for a single LED illumination is as follows:

(1) firstly, inserting a square geometric simulation flexible optical neural interface substrate with the thickness of 3 multiplied by 0.6 mm; simulating miniature LEDs of different sizes by using squares of different sizes, and inserting each simulation body into a designed position; defining the sizes of three micro LEDs which are 90 multiplied by 110 multiplied by 50 mu m, 220 multiplied by 270 multiplied by 50 mu m and 320 multiplied by 390 multiplied by 50 mu m respectively; the thickness of the micro LED chip is uniformly set to be 50 μm, and LEDs with different heights can also be truly simulated by changing the distance between the absorption layers;

fig. 1 is a model diagram of a 3 × 3 micro LED array of a created optical neural interface, wherein nine micro LEDs with three different sizes are disposed on a substrate block of a flexible circuit board of the optical neural interface;

(2) then, adding a thin plate absorption layer on one of the LEDs to simulate nervous tissue, defining the surface properties of each material, and applying the surface properties to the proper object and surface in the simulation body; the main definitions are light source characteristics of the upper surfaces of nine blocks simulating the micro LEDs and the lower surface properties of a thin plate absorption layer simulating nerve tissues;

the lower surface of the nerve tissue geometry simulator is defined as an ideal absorption layer without scattering and reflection, the emission form of the surface light source on the square block simulating the miniature LED is defined as light source characteristics, specifically, the light source characteristics adopt Cree C460TR2432, the light emitting wavelength of the LED is defined as 460nm, and the optical power density range of the surface light source is set to be 354mW/mm²The total light number range of each LED geometric solid simulator is 1-100 ten thousand;

FIG. 2 is a graph of a 10 million ray trace model with an absorbing layer added, where an ideal non-reflective and non-scattering absorbing layer is added over the center micro LED to analyze irradiance thereat;

(3) finally, analyzing and processing the light tracking result; the method mainly comprises irradiance distribution, illuminance analysis, light source characteristic analysis, amplitude/luminance analysis, 3D irradiance analysis, optical path analysis and the like.

Fig. 3 is an irradiance analysis plot of the central micro-LED illumination, here image pixel point 200.

As shown in FIG. 4, the minimum threshold value of 1mW/mm of the light source in optogenetics was set²Changing the pixel point to 20, and obtaining an irradiance analysis chart after processing the simulation result by checking smoothing and regional coordination.

Fig. 5 is a supplementary illustration of 3D irradiance for a single LED emitting light, clearly showing the irradiance distribution.

The simulation results are further processed to obtain a contour map and a profile curve of irradiance, as shown in fig. 6. So that specific coordinate values and optical power density values can be obtained in the distribution map or in a derived data file.

Example 2

(1) First, nine LEDs were analyzed for irradiance for simultaneous ray tracing, as shown in FIG. 7, emission patterns were each defined as a light source characteristic, emission wavelengths were each 460nm, and the optical power density of each micro LED was set to 354mW/mm²The total number of light rays is 90 ten thousand;

FIG. 8 is a 3D irradiance auxiliary plot of nine LED emissions, clearly illustrating the individual micro-LED irradiance distributions and overlapping crosstalk;

(2) then, the size of the micro LED and the vertical distance between the upper surface of the light source and the nerve tissue are continuously changed, the obtained detailed data are integrated and analyzed, and the summary is 1mW/mm²The relationship of the effective illumination areas, as shown in fig. 9, obtains the line graphs of the effective illumination ranges and the vertical distances of the LEDs with different sizes;

(3) finally, further summarizing the relation and the rule among all the parameters, converting the equal area of the square micro LED surface light source into a circle, building a model to define optical parameters, then performing ray tracing, analyzing the relation between the effective illumination area and the diameter and the vertical distance of the circular surface light source according to irradiance distribution data, as shown in fig. 10, obtaining trend graphs of the effective illumination range and the vertical distance of the circular LED with different sizes, and obtaining a mathematical model of the circular LED surface light source as follows:

where the lambda value is determined by the light source characteristics, a typical light source characteristic lambda value is about 117.89, and R is₁And R₂Respectively representing the radii of the effective illumination circles, r, of the two micro-LEDs₁And r₂Respectively represent the radii of two micro LED surface light sources, H₁And H₂Respectively represent the vertical spacing between the upper surfaces of the two micro LEDs and the nervous tissue.

For a square micro LED surface light source, the length of a diagonal line of a square can be calculated as the diameter of a round LED, and a mathematical model is obtained as follows:

where λ is a parameter representing the rate of change of the effective illuminated area per unit of light source perimeter and per unit of absorption layer spacing, and its value is determined by the light source characteristics, typical light source characteristics λ have a value of about 117.89, a₁And b₁，a₂And b₂Respectively representing the length and width of two micro LED surface light sources, H₁And H₂Respectively represent the vertical spacing between the upper surfaces of the two micro LEDs and the nervous tissue, L and L_minRespectively representing the center-to-center distance of two circular surface light sources and the minimum center-to-center distance of two square surface light sources arranged in the same horizontal plane.

From the above embodiments, the invention establishes a modeling and simulation method for guiding the layout design of the micro LED array aiming at the micro LED array design of the optical neural interface in the field of optogenetics, and can obtain the theoretical minimum center distance of the used micro LEDs through physical and mathematical models to obtain the effective light stimulation volume and action range, thereby providing design guidance in the aspects of improving the spatial resolution of the optical neural interface and avoiding crosstalk.

While the details of the present invention have been presented in example 1 and example 2, the above description should not be construed as limiting the invention. Accordingly, the scope of the invention should be determined from the following claims.