Uniform magnetic field generation device based on micro electromagnet array

Abstract

A uniform magnetic field generating device based on a miniature electromagnet array comprises an electromagnet array module and a current control module, the electromagnet array module comprises a plurality of electromagnet units in a honeycomb array, and the ratio of the center distance of any two adjacent electromagnet units to the diameter of the electromagnet units is smaller than or equal to 2. Each electromagnet unit comprises an iron core, a coil is wound on the iron core, the number of turns of the coil is 195-205, the wire diameter of the coil is 0.05 mm, and the current of the peripheral electromagnet units is gradually reduced along with the increase of the center distance between the peripheral electromagnet units and the central electromagnet unit. Magnetic field force lines generated after each electromagnet unit is electrified are overlapped with magnetic field force lines of the surrounding electromagnet units, a magnetic field overlapping blind area is effectively eliminated, through gradient current distribution, smooth transition with magnetic field distribution of a central area is achieved, the fringe effect is eliminated, and the magnetic field effect is improved. And uniform distribution and uniform sorting of magnetic beads in a sorting flow channel of the magnetic control micro-fluidic chip are completed through the uniform magnetic field.

Description

Technical Field

[0001] The present invention relates to the field of physics, in particular to microfluidic technology, and more particularly to a uniform magnetic field generating device based on a microelectromagnet array. Background Art

[0002] The concept of a micro total analysis system is to integrate the functions of an entire analytical laboratory into a portable device or even a tiny chip. Therefore, the micro total analysis system is also known as "Lab-on-a-chip (LOC)". A microfluidic chip is an important part of LOC, and its main feature is that the effective structures for accommodating fluids (including channels, reactors, and other functional units) are micron-sized in at least one dimension. Based on microelectromechanical processing technology, microfluidic chips fabricate channels and integrate driving and detection devices on materials such as silicon wafers, glass, or PDMS. By controlling the fluids in the channels, basic operation units such as sample preparation, separation, detection, and biological and chemical reactions are integrated onto a chip of a few square centimeters (or even smaller) to complete different biological or chemical reaction processes and analyze their products. Due to its great potential in the fields of biology, chemistry, medicine, etc., it has developed into a brand-new research field that intersects multiple disciplines such as biology, chemistry, medicine, fluidics, electronics, materials, and machinery.

[0003] Microfluidic sorting is to make particles / cells with different characteristics move differentially in a flow field through an external force field (such as a magnetic field), thereby achieving separation.

[0004] In the prior art, there are the following two solutions for electromagnets.

[0005] Solution 1: A single large-sized electromagnet, with a coil wound around a toroidal or U-shaped iron core, and generating a magnetic field by driving with a high current (>100A). Disadvantages: Poor magnetic field uniformity (in the central region, ΔB / B0≈±2%, and in the edge region, it can reach ±10%, where ΔB is the absolute value of the maximum deviation of the magnetic field intensity (B) at any point in the region from B0 (ΔB = |B - B0|)).

[0006] Solution 2: A traditional electromagnet array, with electromagnet units arranged in a regular matrix and each unit powered independently. Disadvantages: The distance between electromagnet units is too large (usually >5 cm), the magnetic field superposition effect is poor, the distance between electromagnet units does not match the size of the electromagnets, resulting in blind spots in the magnetic field superposition region; the magnetic field gradient in the edge region is low, making it difficult to meet the high requirements for gradient fields in applications such as magnetic sorting and magnetic manipulation; there is a lack of compensation design for edge units, exacerbating the edge effect. Edge effect: The phenomenon of magnetic field intensity attenuation caused by the divergence of magnetic field lines in the edge region of an electromagnet, which is the main factor affecting uniformity. Summary of the Invention

[0007] The object of the present invention is to provide a uniform magnetic field generating device based on a micro electromagnet array. The uniform magnetic field generating device based on the micro electromagnet array is to solve the technical problems in the prior art that there are blind areas in the magnetic field superposition region, the magnetic field gradient in the edge region is relatively low and difficult to meet magnetic separation requirements, and the edge effect is relatively serious.

[0008] A uniform magnetic field generating device based on a micro electromagnet array of the present invention includes an electromagnet array module and a current control module. The electromagnet array module includes a number of electromagnet units arranged in a honeycomb array. The ratio of the center distance between any two adjacent electromagnet units to the diameter of the electromagnet unit is less than or equal to 2. Any one electromagnet unit includes an iron core, and a coil is wound around the iron core. The number of turns of the coil is 195 - 205, the wire diameter of the coil is 0.05 mm, the coil is electrically connected to the current control module, the current of the edge electromagnet unit decreases as the center distance from the central electromagnet unit increases. An outer electromagnetic ring is arranged on the outer periphery of the electromagnet array module, and a magnetic field detection sensor is arranged outside the electromagnet array module. The magnetic field detection sensor is electrically connected to the current control module.

[0009] Further, the diameter of any one electromagnet unit is less than 1 mm.

[0010] Further, in the path from the electromagnet unit at the center position of the honeycomb array to the peripheral electromagnet units, the current decreasing gradient in each electromagnet unit is ΔI = 0.05I0 / mm.

[0011] Further, it further includes a magnetic shielding layer, and the magnetic shielding layer wraps the electromagnet array module and the outer electromagnetic ring.

[0012] Further, the magnetic shielding layer is made of nickel - iron alloy.

[0013] Further, the current control module is equipped with a thermal management module. The thermal management module includes a temperature sensor, a cooling module and a temperature controller. The temperature sensor and the cooling module are both electrically connected to the temperature controller. The temperature sensor is used to monitor the temperature of the current control module, and the cooling module is used to cool and dissipate heat from the current control module.

[0014] Further, a double - sided micro - channel layer is integrated in the cooling module.

[0015] Compared with the prior art, the effects of the present invention are positive and obvious. After each electromagnet unit is powered on, the magnetic field lines generated by it are superimposed with the magnetic field lines of the surrounding electromagnet units, effectively eliminating the blind area of magnetic field superposition and forming a continuous magnetic field distribution. The symmetry of the hexagonal arrangement ensures the uniform distribution of magnetic field lines in space. Through the close contact and symmetry design of the hexagonal arrangement, the edge effect is significantly reduced. By optimizing the coil parameter design, the inductance L is reduced, enabling the coil to quickly respond to current changes under high-frequency driving. Through the gradient current distribution, the magnetic field distribution in the central region is smoothly transitioned, eliminating the edge effect, and the uniform distribution and uniform sorting of magnetic beads in the sorting channel of the magneto-controlled microfluidic chip are completed through the uniform magnetic field. Brief Description of the Drawings

[0016] Figure 1 It is a schematic diagram of a uniform magnetic field generating device based on a micro electromagnet array of the present invention. Detailed Embodiment

[0017] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited to these embodiments. Any similar changes made using the present invention should be included in the protection scope of the present invention. The use of directions such as up, down, front, back, left, right, middle, inside, and outside in the present invention is only for the convenience of clear description and does not limit the technical solution of the present invention.

[0018] As Figure 1 shown, a uniform magnetic field generating device based on a micro electromagnet array of the present invention includes an electromagnet array module and a current control module. The electromagnet array module includes a plurality of electromagnet units 1 arranged in a honeycomb array. The ratio of the center distance between any two adjacent electromagnet units 1 to the diameter of the electromagnet unit 1 is less than or equal to 2. Any one electromagnet unit 1 includes an iron core, and a coil is wound around the iron core. The number of turns of the coil is 195 - 205, the wire diameter of the coil is 0.05 mm, the coil is electrically connected to the current control module, and the current of the electromagnet units 1 at the edge decreases with the increase of the center distance from them to the central electromagnet unit 1. An outer peripheral electromagnetic ring 3 is provided on the outer periphery of the electromagnet array module, and a magnetic field detection sensor 2 is provided outside the electromagnet array module. The magnetic field detection sensor 2 is electrically connected to the current control module.

[0019] Further, the diameter of any one electromagnet unit 1 is less than 1 mm.

[0020] Further, in the path from the electromagnet unit 1 at the center position of the honeycomb array to the electromagnet units 1 at the periphery, the current decreasing gradient of each electromagnet unit 1 is ΔI = 0.05I0 / mm.

[0021] Further, it further includes a magnetic shielding layer that wraps the electromagnet array module and the outer peripheral electromagnetic ring 3.

[0022] Further, the magnetic shielding layer is made of nickel-iron alloy.

[0023] Further, the current control module is equipped with a thermal management module. The thermal management module includes a temperature sensor, a cooling module, and a temperature controller. The temperature sensor and the cooling module are both electrically connected to the temperature controller. The temperature sensor is used to monitor the temperature of the current control module, and the cooling module is used to cool and dissipate heat from the current control module. The cooling module adopts a circulating water cooling method.

[0024] Further, a double-sided microchannel layer is integrated in the cooling module. The channel width of the double-sided microchannel layer is 100 μm, and the circulating water cooling is used to achieve a temperature control accuracy of ±0.5 °C.

[0025] Specifically, for the current control module, the electromagnet unit 1, the iron core, the coil, the peripheral electromagnetic ring 3, the magnetic field detection sensor 2, the magnetic shielding layer, the thermal management module, the temperature sensor, the cooling module, and the double-sided microchannel layer in the present invention, the specific structures and principles and other unelaborated parts all adopt the well-known solutions in the prior art, which are already understood by those skilled in the art and will not be elaborated herein.

[0026] Uniform magnetic field: It refers to a magnetic field environment in a specific region where the vector direction and magnitude of the magnetic field intensity (B) are both consistent. Its uniformity is usually quantified by the relative deviation percentage (ΔB / B0×100%).

[0027] Electromagnet array: A system composed of multiple electromagnet units 1 arranged in a specific spatial pattern. The magnetic field superposition and regulation are achieved by adjusting the current, spacing, and geometric parameters of each unit.

[0028] Honeycomb arrangement: The electromagnet unit 1 adopts a hexagonal close-packed structure. The diameter of the electromagnet unit 1 is 1 mm, and the center-to-center distance is 2 mm. The center-to-center distance (d) and the diameter (D) satisfy d / D≤2. The magnetic field lines generated by each electromagnet unit 1 after being energized are superimposed with the magnetic field lines of the surrounding electromagnet units 1, effectively eliminating the magnetic field superposition blind area and forming a continuous magnetic field distribution. The symmetry of the hexagonal arrangement ensures the uniform distribution of the magnetic field lines in space. The hexagonal arrangement significantly reduces the edge effect through close contact and symmetry design.

[0029] Miniaturized unit: The diameter of the electromagnet is ≤1 mm, the number of turns of the coil is 200±5, the wire diameter is 0.05 mm, and the coil is manufactured by a copper-based microfabrication process. In applications such as microfluidic chip sorting and cell manipulation, it is required that the magnetic field can change rapidly to achieve precise manipulation of the target object. Reducing the inductance value can reduce the inductive reactance (XL = 2πfL), where XL is the inductive reactance, f is the alternating current frequency, and L is the inductance. Through the optimization of the coil parameter design, the inductance L is reduced, enabling the coil to respond rapidly to current changes under high-frequency driving.

[0030] The current control module includes independent constant current output terminals equal in number to the number of electromagnet units 1. Any one of the independent constant current output terminals is electrically connected to an electromagnet unit 1 respectively. Under the control of the controller in the current control module, the current of any one electromagnet unit 1 is independently controlled, so as to realize the dynamic switching between the uniform field mode and the gradient field mode. The uniform field mode is the uniform magnetic field, and the gradient field mode is the magnetic field decreasing or increasing according to the gradient. In the present invention, the current control module can be equipped with 256 independent constant current sources, and each independent constant current source can independently control each electromagnet unit 1.

[0031] Gradient current distribution: The current of the electromagnet units 1 at the edge decreases according to the distance gradient (such as ΔI = 0.05I0 / mm), that is, the farther the electromagnet unit 1 is from the center, the smaller its current. Through the gradient current distribution, it smoothly transitions with the magnetic field distribution in the central region, eliminates the edge effect, and realizes a high-uniformity magnetic field distribution (ΔB / B0 < ±0.5%) within a 100×100 mm working area. The uniform distribution of magnetic beads and the uniform sorting in the sorting channel of the magneto-controlled microfluidic chip are completed through the uniform magnetic field. B0 is the magnetic field intensity at the reference point (usually taking the center point of the target area). ΔB is the absolute value of the maximum deviation between the magnetic field intensity (B) at any point in the area and B0 (ΔB = |B - B0|).

[0032] The gradient current distribution forms a stronger magnetic field gradient in the edge region, meets the high requirements for the gradient field in applications such as magnetic separation, and meets the gradient adjustment of 0.115 T / m; T / m is the unit of magnetic field gradient, indicating that the magnetic field intensity changes by 0.115 Tesla (Tesla) per meter of distance, and is used to quantify the spatial change rate of the magnetic field.

[0033] Real-time feedback: The magnetic field data is collected once every 10 ms through the magnetic field detection sensor, and the current distribution is dynamically adjusted through the current control module.

[0034] High-throughput magnetic separation enhancement: An outer electromagnetic ring 3 is added. When the outer electromagnetic ring 3 is energized, it generates a magnetic field, which enhances the magnetic field gradient at the edge. Specifically, the outer electromagnetic ring 3 "focuses" the magnetic field lines on the edge region, reduces the divergence of the magnetic field lines, and thus forms a stronger magnetic field intensity in the edge region. In addition, the magnetic field generated by the outer electromagnetic ring 3 is superimposed on the magnetic field of the electromagnet array module, forming an obvious change in the magnetic field intensity, that is, a higher magnetic field gradient, in the edge region.

[0035] The electromagnet array module is responsible for generating a uniform magnetic field, and the outer electromagnetic ring 3 superimposes a directional gradient field, and realizes the mode switching of "uniform distribution and directional sorting" in a short time through current coordination.

[0036] The magnetic shielding layer is μmetal (nickel-iron alloy), which can suppress environmental interference.

[0037] Thermomagnetic coupling real-time control: The temperature sensor is used to monitor the temperature of the current control module, and the cooling module is used to cool and dissipate heat from the current control module. By combining the data from the temperature sensor and the magnetic field detection sensor 2, the drive current of the current control module and the coolant flow rate of the cooling module are dynamically adjusted to control the magnetic field deviation caused by thermal disturbances within a small range.

Claims

1. A uniform magnetic field generating device based on a microelectromagnet array, characterized in that, It includes an electromagnet array module and a current control module. The electromagnet array module includes a number of electromagnet units arranged in a honeycomb array. The ratio of the center distance between any two adjacent electromagnet units to the diameter of the electromagnet unit is less than or equal to 2. Any one electromagnet unit includes an iron core, and a coil is wound around the iron core. The number of turns of the coil is 195 - 205, the wire diameter of the coil is 0.05 mm, the coil is electrically connected to the current control module, the current of the peripheral electromagnet units decreases as the center distance from the central electromagnet unit increases. An outer electromagnetic ring is provided on the outer periphery of the electromagnet array module, and a magnetic field detection sensor is provided outside the electromagnet array module. The magnetic field detection sensor is electrically connected to the current control module.

2. The uniform magnetic field generating device based on a micro electromagnet array according to claim 1, characterized in that: The diameter of any one electromagnet unit is less than 1 mm.

3. The uniform magnetic field generating device based on a micro electromagnet array according to claim 1, wherein: In the path from the electromagnet unit 1 at the center position of the honeycomb array to the peripheral electromagnet unit 1, the current decreasing gradient in each electromagnet unit 1 is ΔI = 0.05I0 / mm.

4. A uniform magnetic field generating device based on a micro electromagnet array according to claim 1, characterized in that: It also includes a magnetic shielding layer, and the magnetic shielding layer wraps the electromagnet array module and the outer electromagnetic ring.

5. The uniform magnetic field generating device based on a micro electromagnet array according to claim 4, characterized in that: The magnetic shielding layer is made of permalloy.

6. The uniform magnetic field generating device based on a micro electromagnet array according to claim 1, characterized in that: The current control module is equipped with a thermal management module. The thermal management module includes a temperature sensor, a cooling module and a temperature controller. The temperature sensor and the cooling module are both electrically connected to the temperature controller. The temperature sensor is used to monitor the temperature of the current control module, and the cooling module is used to cool and dissipate heat from the current control module.

7. The uniform magnetic field generating device based on a microelectromagnet array according to claim 6, wherein: A double-sided microchannel layer is integrated in the cooling module.

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