A magnetic field device for cell culture and a design method of a magnetic field coil thereof

Abstract

The application provides a magnetic field device for cell culture and a design method of a magnetic field coil thereof, a magnetic shielding box made of two layers of permalloy can effectively avoid the influence of a 50uT level geomagnetic field and an external interference magnetic field, a pair of three-direction double-plane magnetic field coils are arranged in the magnetic shielding box in an up-down mode, each three-direction double-plane magnetic field coil comprises three double-plane coils, the three double-plane coils are used for providing magnetic fields in three directions along three coordinate axes, the magnetic field strength in the three directions is less than 20nT, and the frequency, waveform and strength are all different; the application can be beneficial to cell culture, and can provide an experimental condition of an applied excitation magnetic field with different frequencies, waveforms and strengths, and the application will not be affected by the geomagnetic field and the interference magnetic field.

Description

Technical Field

[0001] This invention relates to the field of cell culture, and more specifically, to a magnetic field device for cell culture and a method for designing its magnetic field coil. Background Technology

[0002] Cell culture is a core technology in biotechnology. With the rapid development of life science research, it has become an important technique and method in disciplines such as genetics, immunology, cell biology, and molecular biology. In recent years, some studies have shown that extremely low-frequency, low-intensity magnetic fields are harmless to normal cells and may even be beneficial, while these fields can have a certain impact on some malignant tumor cells. Traditional magnetic field generating devices mostly use permanent magnets, solenoids, and triaxial Helmholtz coils to provide the external excitation magnetic field for cell culture experiments. Since permanent magnets can only provide static magnetic fields, solenoids and triaxial Helmholtz coils are easily affected by external magnetic fields when placed in open environments. Furthermore, they have low space utilization and are severely affected by the Earth's magnetic field and interfering magnetic fields, leading to inconsistent experimental results and poor reproducibility. Summary of the Invention

[0003] The problem solved by this invention is to provide a magnetic field device for cell culture and a design method for its magnetic field coil, which is beneficial to cell culture and provides experimental conditions for external excitation magnetic fields of different frequencies, waveforms and intensities, without being affected by the geomagnetic field and interfering magnetic fields.

[0004] To address the above problems, the present invention provides a magnetic field device for cell culture, comprising:

[0005] A box-shaped structure with a hollowed-out center forming a cavity that runs from front to back;

[0006] A magnetically shielded box contains an inner cavity for placing cell culture dishes. The box is made of two layers of permalloy and is positioned within the cavity, connected to its inner wall. Both the top and bottom plates of the box have several evenly distributed ventilation holes. A three-directional biplane magnetic field coil is located at the top and bottom of the inner cavity. Two of these coils generate a magnetic field in the middle of the cavity. Each coil comprises three biplane coils, each providing a magnetic field along three directions of a three-dimensional coordinate axis. The strength of each magnetic field is less than 0 nT, and their frequencies, waveforms, and intensities are all different. Gaps exist between the coils and the ventilation holes to allow for normal airflow.

[0007] A fluxgate sensor is set at the center of the inner cavity of the magnetic shielding box to convert the detected magnetic field signal into a first analog voltage signal.

[0008] A driving device is provided to provide a current signal to a three-directional dual-plane magnetic field coil to generate a magnetic field. The driving device includes a reference control signal module, a digital processor module, and a power amplifier circuit module that are connected in sequence. The digital processor module is electrically connected to a fluxgate sensor. The reference control signal module is used for the user to input a first digital voltage signal.

[0009] The beneficial effect of this device is that, since the magnetic field density is most uniform at the very center of the magnetic shielding box, the fluxgate sensor is set at the very center of the magnetic shielding box. The user actively inputs an electrical signal from the reference control signal module to form a first digital voltage signal. The fluxgate sensor converts the detected magnetic field signal into a first analog voltage signal. The first analog voltage signal and the first digital voltage signal enter the digital processor module for filtering and conversion, and are further transmitted to the power amplifier circuit module. The power amplifier circuit module amplifies the filtered and converted first analog voltage signal and the first digital voltage signal and then inputs them into the three-directional dual-plane magnetic field coil to form a magnetic field.

[0010] Furthermore, the first digital voltage signal includes at least one of a sine wave signal, a square wave signal, and a pulse signal. The advantage of this configuration is that these three signals are the most commonly used waveform signals and are fully sufficient for most applications.

[0011] Furthermore, the digital processor module includes an ADC (Analog-to-Digital Converter), a PID controller, and a DAC (Analog-to-Digital Converter), while the power amplifier circuit module includes a power amplifier. The beneficial effect of this configuration is that the ADC converts a first analog voltage signal into a second digital voltage signal. The first and second digital voltage signals are then passed to the PID controller for filtering. The PID controller passes the filtered first and second digital voltage signals to the DAC for merging and conversion back into a filtered analog voltage signal. This filtered analog voltage signal is then used as a voltage-controlled current source, which is input to each of the three-directional biplane magnetic field coils through the power amplifier to form a magnetic field. The power amplifier can effectively generate the desired magnetic field through the principle of electromagnetism.

[0012] Furthermore, the front wall of the magnetic shielding box is slidably connected to the left and right walls for opening and closing. Three pairs of flanges, namely the first flange, second flange, and third flange, are arranged sequentially from top to bottom on the upper side wall of the inner cavity of the magnetic shielding box. A gap exists between the two first flanges and the top wall of the inner cavity. Three pairs of flanges, namely the fourth flange, fifth flange, and sixth flange, are arranged sequentially from top to bottom on the lower side wall of the inner cavity. A gap exists between the two sixth flanges and the bottom wall of the inner cavity. These six pairs of flanges are used to house six biplane coils. The beneficial effect of this arrangement is that it creates gaps between the three-directional biplane magnetic field coils and the upper and lower ventilation holes, allowing for normal airflow.

[0013] Furthermore, a pair of plastic support rods are provided on the side wall of the inner cavity of the magnetic shielding box. These two support rods clamp the fluxgate sensor, fixing it in place at the exact center of the inner cavity. The advantage of this design is that it effectively positions the fluxgate sensor at the exact center of the inner cavity, the plastic does not generate magnetic field interference, and it does not affect the fluxgate sensor's ability to sense magnetic fields. This location also ensures the most uniform magnetic field density, allowing the fluxgate sensor to effectively sense changes in the magnetic field throughout the entire inner cavity of the magnetic shielding box.

[0014] Furthermore, a plastic support frame is provided at the lower end of the magnetic shielding box. The support frame has a frame-like structure, exposing the ventilation holes on the lower surface of the magnetic shielding box. This allows for further support of the magnetic shielding box while ensuring normal air circulation. The beneficial effect of this design is that it effectively suspends the magnetic shielding box, allowing air to flow in naturally through the ventilation holes.

[0015] Furthermore, the present invention also provides a method for designing a magnetic field coil for a magnetic field device for cell culture, for designing the above-mentioned three-directional biplane magnetic field coil, comprising the following steps:

[0016] S1. Determine the space required for the fluxgate sensor within the magnetic shielding box;

[0017] S2. Discretize the space required by the fluxgate sensor into several target points at equal intervals according to the three-dimensional coordinate axis, and set the magnetic field strength of each target point to a specified constant to form the target magnetic field;

[0018] S3. Preset the stream function of the three-direction dual-plane magnetic field coil. The stream function contains an unknown matrix and Fourier coefficients to be determined. Determine the Fourier coefficients based on the symmetry characteristics of the target magnetic field. Establish the relationship between the stream function and the current density based on the current density of the target magnetic field.

[0019] S4. Establish the expression for the magnetic field generated by the current density based on the relationship between the stream function and the current density;

[0020] S5. Substitute each of the target points into the magnetic field expression to obtain the coefficient matrix of the unknown matrix. The unknown matrix, the coefficient matrix, and the magnetic field magnitude of each target point constitute a matrix equation.

[0021] S6. Solve the matrix equation to obtain a unique stream function expression and stream function contour lines;

[0022] S7. Establish the equivalent discretized flow function and determine the coil constants.

[0023] Furthermore, the stream function expression in step S3 is:

[0024]

[0025] Where M and N are the design orders of the coil, L is the side length of the coil, and P mn Let x and y be the unknown matrix, where x and y are the planar coordinates of the coil.

[0026] Furthermore, the expression for the magnetic field in step S4 is:

[0027]

[0028] in, The magnetic field strength of the coil. Represents the current density in different directions, where μ0 is the free permeability. Let r be the vector pointing from the current element to the point to be determined, r be the distance from the current element to the point to be determined, and S be the area of ​​the coil.

[0029] Furthermore, in step S7, the equivalent formula is as follows:

[0030] S = S min +(i+1 / 2)I0,(i=0,1,2···,K-1),

[0031]

[0032] Among them, S max S is the maximum value of the flow function in the plane. min I0 is the minimum value of the in-plane flow function, K is the equivalent coil constant, and I0 is the magnitude of the excitation current.

[0033] The beneficial effects of this method are that it can effectively produce a three-directional biplane magnetic field coil with a magnetic field strength of less than 20 nT. Moreover, the magnetic field generated by the three-directional biplane magnetic field coil has different frequencies, waveforms, and intensities in the three directions of the three-dimensional coordinate axis. It can provide experimental conditions for external excitation magnetic fields with different frequencies, waveforms, and intensities, which is beneficial for cell culture and experiments. Attached Figure Description

[0034] Figure 1This is a three-dimensional schematic diagram of the magnetic field device for cell culture in this invention;

[0035] Figure 2 This is a perspective view of the inner cavity of the magnetic shielding box in this invention;

[0036] Figure 3 This is a schematic diagram of the operation of the driving device in this invention;

[0037] Figure 4 This is a cross-sectional view of the magnetic shielding box in this invention;

[0038] Figure 5 This is a three-dimensional schematic diagram of the magnetic shielding box of the present invention;

[0039] Explanation of reference numerals in the attached figures:

[0040] 1-Box body, 2-Magnetic shielding box, 2.1-Ventilation hole, 2.2-Support rod, 2.31-First flange, 2.32-Second flange, 2.33-Third flange, 2.34-Fourth flange, 2.35-Fifth flange, 2.36-Sixth flange, 3-Fluorescence gate sensor, 4-Drive device, 4.1-Reference control signal module, 4.2-Digital processor module, 4.3-Power amplifier circuit module, 5-Three-direction dual-plane magnetic field coil, 5.1-Dual-plane coil, 6-Support frame. Detailed Implementation

[0041] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0042] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed when in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0043] This invention provides a magnetic field device for cell culture, comprising:

[0044] A box 1, with a hollowed-out middle section forming a cavity 1.1 that runs through the front and back;

[0045] A magnetic shielding box 2 is provided, with an inner cavity for placing cell culture dishes. The magnetic shielding box 2 is made of two layers of permalloy and is placed in the cavity 1.1, connected to the inner wall of the cavity 1.1. The top and bottom plates of the magnetic shielding box 2 are provided with several evenly distributed ventilation holes 2.1. A three-directional dual-plane magnetic field coil 5 is provided at the top and bottom of the inner cavity of the magnetic shielding box 2. The two three-directional dual-plane magnetic field coils 5 are used to form a magnetic field in the middle part of the inner cavity of the magnetic shielding box 2. Each three-directional dual-plane magnetic field coil 5 includes three dual-plane coils 5.1, which are used to provide magnetic fields in three directions along the three-dimensional coordinate axes. The strength of the magnetic field in the three directions is less than 20 nT, and the frequency, waveform and strength are different. There is a gap between the three-directional dual-plane magnetic field coils 5 and the ventilation holes 2.1 to allow normal air circulation.

[0046] A fluxgate sensor 3 is set at the center of the inner cavity of the magnetic shielding box 2, and is used to convert the detected magnetic field signal into a first analog voltage signal.

[0047] A driving device 4 is used to provide a current signal to a three-directional dual-plane magnetic field coil 5 to generate a magnetic field. The driving device 4 includes a reference control signal module 4.1, a digital processor module 4.2, and a power amplifier circuit module 4.3 connected in sequence. The digital processor module 4.2 is electrically connected to the fluxgate sensor 3. The reference control signal module 4.1 is used for the user to input a first digital voltage signal.

[0048] Specifically, the first digital voltage signal includes at least one of a sine wave signal, a square wave signal, and a pulse signal. These three signals are the most commonly used waveform signals and are fully sufficient for the application.

[0049] Specifically, the digital processor module 4.2 includes an ADC analog-to-digital converter, a PID controller, and a DAC analog-to-digital converter, and the power amplifier circuit module 4.3 includes a power amplifier. The ADC is used to convert a first analog voltage signal into a second digital voltage signal. The first and second digital voltage signals are used as reference control signals and passed to the PID controller for filtering. The PID controller passes the filtered reference control signal to the DAC to convert it into a filtered analog voltage signal. The filtered analog voltage signal is used as a voltage-controlled current source and input to each of the three-directional dual-plane magnetic field coils 5 through the power amplifier circuit module 4.3 to form a magnetic field. The power amplifier is used to effectively amplify the power of the filtered analog voltage signal for electromagnetic conversion.

[0050] Preferably, the front sidewall of the magnetic shielding box 2 is slidably connected to the left and right sidewalls of the magnetic shielding box 2 for opening and closing; three pairs of flanges are arranged sequentially from top to bottom on the upper sidewall of the inner cavity of the magnetic shielding box 2, namely the first flange 2.31, the second flange 2.32, and the third flange 2.33, with a gap between the two first flanges 2.31 and the top wall of the inner cavity of the magnetic shielding box 2; three pairs of flanges are arranged sequentially from top to bottom on the lower sidewall of the inner cavity of the magnetic shielding box 2, namely the fourth flange 2.34, the fifth flange 2.35, and the sixth flange 2.36, with a gap between the two sixth flanges 2.36 and the bottom wall of the inner cavity of the magnetic shielding box 2; the six pairs of flanges are respectively used to place six biplane coils 5.1. (See attached diagram) Figure 5 As shown, grooves can be provided vertically on both the left and right sides of the magnetic shielding box 2. This allows the front sidewall of the magnetic shielding box 2 to be inserted along the grooves to seal it, and also to slide upwards along the grooves to open it. Six biplane coils 5.1 can be inserted and placed on their respective pairs of flanges, and can also be removed, facilitating the insertion and removal of cell culture dishes and fluxgate sensors 3. The six pairs of flanges can be designed as strips, with a length equal to the length of the sidewall of the magnetic shielding box 2, ensuring that each biplane coil 5.1 is securely placed on its corresponding pair of flanges.

[0051] Preferably, a pair of plastic support rods 2.2 are provided on the side wall of the inner cavity of the magnetic shielding box 2. The two support rods 2.2 are used to clamp the fluxgate sensor 3, so that the fluxgate sensor 3 is fixedly positioned in the exact center of the inner cavity of the magnetic shielding box 2. Plastic does not have magnetic or electrical conductivity, so it will not affect the internal magnetic field. When the fluxgate sensor 3 is clamped, it will not affect the effect of the fluxgate sensor in sensing the magnetic field. Moreover, this structure can effectively place the fluxgate sensor 3 in the exact center of the uniform magnetic field, so that the fluxgate sensor can effectively sense the changes in the magnetic field throughout the entire inner cavity of the magnetic shielding box.

[0052] Preferably, the lower end of the magnetic shielding box 2 is provided with a plastic support frame 6. The support frame 6 has a frame-like structure, which exposes the ventilation holes 2.1 on the lower surface of the magnetic shielding box 2, so as to further support the magnetic shielding box 2 while ensuring normal air circulation. (See attached...) Figure 1 As shown, the support frame 6 is a frame structure that can be assembled from ten strip-shaped plastic parts or integrally injection molded. The purpose is to suspend the magnetic shielding box 2 in the air so as not to affect the magnetic field. At the same time, the ventilation holes 2.1 on the lower surface of the magnetic shielding box 2 are exposed. Since each of the two-plane coils 5.1 in the three-directional two-plane magnetic field coils 5 has gaps, the support frame 6 can further support the magnetic shielding box 2 while allowing air to flow naturally from the ventilation holes 2.1 on the lower surface of the magnetic shielding box 2.

[0053] When in use, the user needs to input the initial first digital voltage signal, or the program can set the input of the first digital voltage signal automatically. The first digital voltage signal includes at least one of sine wave signal, square wave signal and pulse signal. The first digital voltage signal is first filtered by the PID controller. The filtering process is to eliminate the error between the first digital voltage signal and the second digital voltage signal so that they can be merged later. Since no magnetic field is generated initially, the fluxgate sensor (3) will not generate the first analog voltage signal and therefore will not generate the second digital voltage signal. So the initial first digital voltage signal is directly converted into an analog voltage signal by the DAC analog-to-digital converter after passing through the PID controller, and then enters the two three-direction dual-plane magnetic field coils (5) through the power amplifier to generate the initial magnetic field. At this time, the fluxgate sensor (3) senses the magnetic field. The field is induced and the sensed magnetic field is converted into a corresponding first analog voltage signal. The first analog voltage signal enters the ADC analog-to-digital converter and is converted into a second digital voltage signal. The user can continue to input the first digital voltage signal, or the program can set to automatically continue to input the first digital voltage signal. The first digital voltage signal and the second digital voltage signal enter the PID controller. At this time, the PID controller will eliminate the error between the first digital voltage signal and the second digital voltage signal to complete the filtering operation. The filtered first digital voltage signal and the second digital voltage signal are transmitted to the DAC analog-to-digital converter for conversion and merging to form a filtered analog voltage signal. Then, the frequency of the filtered analog voltage signal is amplified by the power amplifier so that it enters two three-directional dual-plane magnetic field coils (5) to continuously generate a magnetic field. The same applies to the following, and will not be repeated.

[0054] This invention also provides a method for designing a magnetic field coil for a magnetic field device used in cell culture, for designing the aforementioned three-directional biplane magnetic field coil 5, comprising the following steps:

[0055] S1. Determine the space required for the fluxgate sensor 3 within the inner cavity of the magnetic shielding box 2;

[0056] S2. Discretize the space required by the fluxgate sensor 3 into several target points at equal intervals according to the three-dimensional coordinate axis, and set the magnetic field strength of each target point to a specified constant to form the target magnetic field;

[0057] S3. Preset the stream function of the three-direction dual-plane magnetic field coil 5. The stream function contains an unknown matrix and Fourier coefficients to be determined. Determine the Fourier coefficients based on the symmetry characteristics of the target magnetic field. Establish the relationship between the stream function and the current density based on the current density of the target magnetic field.

[0058] S4. Establish the expression for the magnetic field generated by the current density based on the relationship between the stream function and the current density;

[0059] S5. Substitute each of the target points into the magnetic field expression to obtain the coefficient matrix of the unknown matrix. The unknown matrix, the coefficient matrix, and the magnetic field magnitude of each target point constitute a matrix equation.

[0060] S6. Solve the matrix equation to obtain a unique stream function expression and stream function contour lines;

[0061] S7. Establish the equivalent discretized flow function and determine the coil constants.

[0062] Specifically, the coordinates of each target point are as follows:

[0063] r ti =(z ti y yi z ti |,i=1,2,3,…,S,

[0064] Assume the magnetic field strength at S coordinate points is:

[0065]

[0066] The preset process for the stream function S(x,y) of the three-directional dual-plane magnetic field coil 5 is as follows: with z = ±a determined, a = 0.75m, representing the distance between the three-directional dual-plane magnetic field coil 5 and the fluxgate sensor 3, the arbitrary stream function S(x,y) is expanded according to the two-dimensional Fourier coefficients as follows:

[0067]

[0068] Where M and N are the coil design orders, and α n β n γ m δ m The Fourier coefficients to be determined represent the weights of different harmonic components of the target magnetic field, and their magnitudes are determined based on the symmetry of the target magnetic field. The Fourier coefficients are determined based on the symmetry of the target magnetic field. The symmetry and antisymmetry of the four-directional magnetic field coils are shown below:

[0069]

[0070] With B X Taking the coil as an example, B X Since the x-axis is antisymmetric, the cosine function is an even function. Therefore, the coefficient of the cosine function in the first row of equation (1) is 0, i.e., a n =0, similarly, B X Since the function is symmetric about the y-axis, the coefficient of the sin function in the second row of equation (1) is 0, i.e., δ m =0; therefore B X The coil current function is preset to:

[0071]

[0072] Where M and N are the design orders of the coil, L is the side length of the coil, and P mn Let be an unknown matrix, and x and y be the planar coordinates of the coil. In the stream function, The parentheses are The parentheses are The reason is related to the boundary conditions:

[0073] 1. It is necessary to ensure that the direction of the conductor at the boundary x = L is inward, that is, the function value of the stream function is 0 at the boundary.

[0074] 2. Minimum frequency criterion: Selecting the fundamental frequency with the smallest trigonometric function can effectively reduce the complexity of the coil.

[0075] In the pre-defined stream function equation, the parameters to be solved are the unknown matrix Pmn that satisfies the magnetic field requirements of the target region.

[0076] The relationship between the stream function S and the current density J is as follows: Right now:

[0077]

[0078] Taking the target magnetic field coil in the x-direction as an example, we have:

[0079]

[0080]

[0081] The expression for the magnetic field is obtained based on Biot-Savart's law.

[0082]

[0083] ,in,

[0084]

[0085] Therefore,

[0086]

[0087] Furthermore,

[0088]

[0089] in,

[0090] r t and r s These are the coordinates of each target point and the coordinates of the current source, respectively.

[0091] rt =(x t y y z t ), r s =(x s y s z s ), J = (J x J y J z ).

[0092] With B X For example, substituting J y From (x, y), we can obtain...

[0093]

[0094] in,

[0095] Bx is actually formed by the superposition of the magnetic fields of two planar coils. The derivation only calculates the magnetic field of one coil. Let matrix A = {A...} mn,i}∈R mn×s P = {P} mn}∈R mn×1 Therefore, we only need to solve the matrix equation AP = b, where A is the coefficient matrix and P is the unknown column vector. In practical coil design, the design order is generally mn < S, so the equation is usually an overdetermined equation with no solution. A stable solution cannot be obtained; only the optimal solution with the minimum error can be found. Therefore, solving the overdetermined equation is an optimization problem.

[0096] According to the theorem: If X * It is the normal system of equations G T GX = G T If the solution to b is X, then X * It is the least squares solution to the overdetermined system of equations GX = b. Therefore, when the error is located using the least squares method, the least squares solution to the equation is the solution to equation (13).

[0097]

[0098] The coefficient matrix of a system of linear equations

[0099] The condition matrix is ​​defined as: cond(K) = ||K||·||K -1 ||,

[0100] When the condition number of the coefficient matrix is ​​too large, it indicates that the coefficient matrix is ​​severely ill-conditioned. In coil design, the calculation of matrix A often has deviations. For severely ill-conditioned matrix equations, even a small deviation in the coefficient matrix can lead to significant errors. To reduce the impact of ill-conditioned equations, a suitable regularization method is generally used to find an optimal solution. To mitigate the effects of ill-conditioned equations, the Tikhonov regularization operator can be introduced. On the one hand, it can reduce the ill-conditioned nature of the equations, making the final coil system design simpler; on the other hand, depending on the selected regularization operator, different performance characteristics of the coil system can be constrained to achieve optimality.

[0101] Using a power operator as a penalty term, the total power of the coil is:

[0102]

[0103] Where δ and t are the resistivity and thickness of the coil, respectively, and G is the power canonical operator, expressed as follows:

[0104]

[0105]

[0106] Finally, the design problem of the coil became,

[0107] Find suitable P stmin{AP-b|| 2 +αp T GP},

[0108] It can be seen that when

[0109] P=(A T A+αG) T ·A T b, ||AP-b|| 2 +αP T By selecting an appropriate regularization parameter α, a suitable stream function can be designed from GP→min. When the P matrix is ​​determined, the expression for the stream function is also uniquely expressed, and its stream function contour lines represent the wiring shape of the coil.

[0110] The stream function can be represented by the discrete conductor current, as shown in the following equivalent formula.

[0111]

[0112] Coil constant

[0113] The K value is a constant that affects the number of turns of the equivalent coil. A larger K value results in a denser equivalent coil, and the magnetic field generated by the coil is closer to the true value. However, an excessively large K value leads to overly dense equivalent lines, affecting manufacturing. The coil constant C represents the relationship between the current flowing through the planar coil and the magnetic field strength generated. A larger K value results in a smaller I0 and a larger coil constant C. To generate a magnetic field within the μT range, a planar coil carrying a 1A current needs to generate 10000nT, or 10μT, of magnetic field. The coil can only carry a current of 4-5A. If 1A of current generates 1μT, it does not meet the experimental requirements. Therefore, the minimum coil constant C is 10μT corresponding to a 1A current. The coil constant C is also related to the distance s between the coil and the shielding layer. The closer the distance, the larger the coil constant C. However, too close a distance will affect the coil installation; the uniformity of the coil needs to be considered.

[0114]

[0115] And the coil constant C > 10000nT is used as the optimization objective. Wherein, B x (x,y,z) represents the magnetic field generated by the planar coil at each target point within the target region, and B0(0,0,0) represents the magnetic field at the center point of the target region. At this point, a set of usable coil designs is complete.

[0116] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A magnetic field device for cell culture, characterized in that, include: A box (1), wherein the middle part of the box (1) is hollowed out to form a cavity (1.1) that runs through the front and back; A magnetic shielding box (2) is provided, the magnetic shielding box (2) having an inner cavity for placing cell culture dishes. The magnetic shielding box (2) is made of two layers of permalloy. The magnetic shielding box (2) is placed in the cavity (1.1) and connected to the inner wall of the cavity (1.1). The top and bottom plates of the magnetic shielding box (2) are provided with several evenly distributed ventilation holes (2.1). The top and bottom of the inner cavity of the magnetic shielding box (2) are respectively provided with a three-directional dual-plane magnetic field coil (5). Two of the three-directional dual-plane magnetic... The field coil (5) is used to form a magnetic field in the middle part of the inner cavity of the magnetic shielding box (2). Each of the three-direction biplane magnetic field coils (5) includes three biplane coils (5.1). The three biplane coils (5.1) are used to provide magnetic fields in three directions along the three-dimensional coordinate axis. The strength of the magnetic fields in the three directions is less than 20nT, and the frequency, waveform and strength are different. A gap is provided between the three-direction biplane magnetic field coil (5) and the ventilation hole (2.1) to allow normal air circulation. A fluxgate sensor (3) is disposed at the center of the inner cavity of the magnetic shielding box (2) and is used to convert the detected magnetic field signal into a first analog voltage signal. A driving device (4) is provided to provide a current signal to the three-direction dual-plane magnetic field coil (5) to generate a magnetic field. The driving device (4) includes a reference control signal module (4.1), a digital processor module (4.2) and a power amplifier circuit module (4.3) connected in sequence. The digital processor module (4.2) is electrically connected to the fluxgate sensor (3). The reference control signal module (4.1) is used for the user to input a first digital voltage signal.

2. The magnetic field device for cell culture according to claim 1, characterized in that, The first digital voltage signal includes at least one of a sine wave signal, a square wave signal, and a pulse signal.

3. A magnetic field device for cell culture according to claim 2, characterized in that, The digital processor module (4.2) includes an ADC analog-to-digital converter, a PID controller, and a DAC analog-to-digital converter, and the power amplifier circuit module (4.3) includes a power amplifier.

4. A magnetic field device for cell culture according to claim 3, characterized in that, The front sidewall of the magnetic shielding box (2) is slidably connected to the left and right sidewalls of the magnetic shielding box (2) for opening and closing; three pairs of flanges are arranged from top to bottom on the upper sidewall of the inner cavity of the magnetic shielding box (2), namely the first flange (2.31), the second flange (2.32) and the third flange (2.33), and there is a gap between the two first flanges (2.31) and the top wall of the inner cavity of the magnetic shielding box (2); three pairs of flanges are arranged from top to bottom on the lower sidewall of the inner cavity of the magnetic shielding box (2), namely the fourth flange (2.34), the fifth flange (2.35) and the sixth flange (2.36), and there is a gap between the two sixth flanges (2.36) and the bottom wall of the inner cavity of the magnetic shielding box (2); the six pairs of flanges are respectively for placing the six dual-plane coils (5.1).

5. A magnetic field device for cell culture according to claim 4, characterized in that, A pair of plastic support rods (2.2) are provided on the side wall of the inner cavity of the magnetic shielding box (2). The two support rods (2.2) are used to clamp the fluxgate sensor (3) so that the fluxgate sensor (3) is fixedly set in the center of the inner cavity of the magnetic shielding box (2).

6. A magnetic field device for cell culture according to claim 1, characterized in that, The magnetic shielding box (2) is provided with a plastic support frame (6) at the lower end. The support frame (6) has a frame structure, which exposes the ventilation holes (2.1) on the lower surface of the magnetic shielding box (2) to further support the magnetic shielding box (2) while ensuring normal air circulation.

7. A method for designing a magnetic field coil for a magnetic field device for cell culture as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Determine the space required for the fluxgate sensor (3) to occupy inside the magnetic shielding box (2); S2. The space required by the fluxgate sensor (3) is discretized into several target points at equal distances in three directions according to the three-dimensional coordinate axis in three-dimensional space, and the magnetic field strength of each target point is set to a specified constant to form a target magnetic field; S3. Preset the stream function of the three-direction dual-plane magnetic field coil (5), the stream function contains an unknown matrix and Fourier coefficients to be determined, determine the Fourier coefficients according to the symmetry characteristics of the target magnetic field, and establish the relationship between the stream function and the current density according to the current density of the target magnetic field. S4. Establish the magnetic field expression for the target magnetic field based on the relationship between the stream function and the current density; S5. Substitute each of the target points into the magnetic field expression to obtain the coefficient matrix of the unknown matrix. The unknown matrix, the coefficient matrix, and the magnetic field magnitude of each target point constitute a matrix equation. S6. Solve the matrix equation to obtain a unique stream function expression and stream function contour lines; S7. Establish the equivalent discretized flow function and determine the coil constants.

8. The method for designing a magnetic field coil for cell culture according to claim 7, characterized in that, The stream function expression in step S3 is, Where M and N are the design orders of the coil, L is the side length of the coil, and P mn Let x and y be the unknown matrix, where x and y are the planar coordinates of the coil.

9. The design method of a magnetic field coil for cell culture according to claim 8, characterized in that, The expression for the magnetic field in step S4 is as follows: in, The magnetic field strength of the coil. Represents the current density in different directions, where μ0 is the free permeability. Let r be the vector pointing from the current element to the point to be determined, r be the distance from the current element to the point to be determined, and S be the area of ​​the coil.

10. The design method of a magnetic field coil for cell culture according to claim 9, characterized in that, In step S7, the equivalent formula is as follows: S=S min +(i+1 / 2)I0,(i=0,1,2···,K-1), Among them, S max S is the maximum value of the flow function in the plane. min I0 is the minimum value of the in-plane flow function, K is the equivalent coil constant, and I0 is the magnitude of the excitation current.

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