A three-dimensional magnetic levitation structure of diamagnetic particles

Abstract

The application discloses a three-dimensional magnetic suspension structure of diamagnetic particles, comprising: permanent magnets, conical soft magnets, diamagnetic particles and non-magnetic supports; the permanent magnets are three pairs of permanent magnets installed in x, y and z orthogonal directions, wherein the magnetic pole directions of only two pairs of the permanent magnets are the same; the conical soft magnets are three pairs of conical soft magnets, which have large end faces and small end faces, the large end faces are connected with the one end of the permanent magnets which are towards the center, and the small end faces are towards the center of the three-dimensional magnetic suspension structure; the diamagnetic particles are suspended in the center of the magnetic suspension structure formed by the permanent magnets and the soft magnets; and the non-magnetic supports are used for fixing and installing the permanent magnets and the soft magnets. The application makes full use of the advantages of the permanent magnetic suspension, such as passive, low noise and strong environmental adaptability, and is compatible with a large particle size range and high magnetic trap stiffness; the application has the characteristics of non-directional suspension, and greatly widens the application of the diamagnetic particle magnetic suspension structure in the fields of mobile and rotating platforms.

Description

Technical Field

[0001] This invention relates to the field of particle levitation technology, specifically to a three-dimensional magnetic levitation structure for antimagnetic particles. Background Technology

[0002] Suspension technology reduces environmental interference such as clamping thermal noise and vibration that are difficult to avoid with traditional oscillators, thus having extremely high measurement sensitivity. It has wide applications and promising prospects in cell biology, weak mechanical sensing, high-sensitivity acceleration sensing and quantum physics.

[0003] Current suspended particle systems mainly include three methods: laser suspension, electrostatic suspension, and superconducting suspension. Among them, laser suspension has the largest bandwidth in suspension systems, but its acceleration sensitivity is limited by the size of the particles. Electrostatic suspension is the most mature technology, which relies on feedback circuits to control the suspended body, but its acceleration sensitivity is limited by electronic noise. Superconducting suspension is a newly proposed technology with theoretically high sensitivity; however, it requires the system to operate at low temperatures (below 10K), which limits its application range.

[0004] Antimagnetic levitation technology, which uses permanent magnets to form magnetic traps, can levitate particles with diameters on the order of hundreds of micrometers and has extremely high theoretical acceleration sensitivity. Compared with electrostatic levitation and optical levitation, it does not require external energy input, thus reducing the main source of noise in the levitation system. In addition, the antimagnetic levitation system does not rely on a low-temperature environment and does not have the application temperature environment limitations of superconducting levitation.

[0005] Taking the paper "Lens-free Optical Detection of Thermal Motion of a Sub-millimeter Sphere Diamagnetically Levitated in High Vacuum" (Phys. Rev. Applied 16, L011003) as an example, this paper explores the potential and important role of millimeter- or sub-millimeter-sized levitated oscillators in studying various fundamental problems and practical applications. Addressing the key technical requirements for the effective measurement of levitated oscillator motion, a lens-free optical detection scheme is theoretically proposed to detect the motion of millimeter- or sub-millimeter-sized levitated oscillators. The measurement efficiency approaches the standard quantum limit, and the optical power is moderate. Experimental verification was conducted on a 0.5 mm diameter microsphere, which exhibits antimagnetic levitation in high vacuum and at room temperature, allowing for high-precision detection of thermal motion. Based on this system, the calculated acceleration sensitivity is 0.97 ng / √Hz, more than an order of magnitude higher than the best value reported by the levitation mechanics system. Due to the system's stability, the minimum resolved acceleration reaches 3.5 pg, and the measurement time is 10 seconds. 5Seconds. This result has potentially important applications in the realization of compact gravimeters and accelerometers.

[0006] Taking the article "Cooling the motion of a silica microsphere in a magnetic gravitational trap in ultra-high vacuum" (Bradley R Slezak et al 2018 New J. Phys. 20 063028) as an example, this study investigates a magnetic gravitational trap in ultra-high vacuum. Unlike optical potential traps, this method utilizes the interaction between the magnetic field and gravity generated by a permanent magnet to create a completely passive potential trap for diamagnetic particles. The article demonstrates that, through optical feedback damping, the center-of-mass motion of the trapped silica microspheres can be cooled from ambient temperature to an effective temperature close to or below 1 mK for both degrees of freedom. Utilizing the advantages of levitation systems, especially particles in a vacuum, provides a unique platform for studying the mechanical behavior of objects well isolated from their environment, enabling the investigation of fundamental problems in quantum mechanics, gravity, and other weak forces. This overcomes the practical application challenges inherent in the optical trapping of nanoparticles, despite its typical levitation optical-mechanical system, due to the required high-intensity light heating, particularly when combined with a high-vacuum environment.

[0007] The paper "Room temperature test of the continuous spontaneous localization model using a levitated micro-oscillator" (Phys. Rev. Research 2, 013057) reports a proof-of-principle experiment using a diamagnetic levitation system to test a collapse model. Continuous spontaneous localization (CSL) models predict that weak random forces acting on a physical system will lead to minute violations of energy conservation. Mechanical oscillators are a suitable method for testing such forces, and levitated micro-oscillators, in particular, have recently been considered an ideal testing system. The paper reports a proof-of-principle experiment using a micro-oscillator consisting of a diamagnetic microsphere suspended in a high-vacuum magnetic gravitational trap. Due to its ultra-low mechanical dissipation, the levitated oscillator provides a new upper limit for the CSL collapse rate, increasing it by two orders of magnitude over the previous upper limit in the same frequency range, and partially achieving the enhanced collapse rate suggested by Adler. Although the experiment was conducted at room temperature, it has already shown advantages compared to experiments conducted at cryogenic temperatures. These experimental results demonstrate the strong potential of magnetically levitated mechanical oscillators as a promising method for testing collapse models.

[0008] However, current antimagnetic levitation systems are mainly focused on laboratory research, primarily on non-rotating, non-motorizing platforms. The magnetic levitation structures used are mostly designed to counteract gravity in one direction, with weak or no magnetic trapping force in other directions, failing to meet the requirements for gravitational balance. Furthermore, current antimagnetic levitation systems cannot effectively capture magnetic particles when the platform flips, severely limiting their application on rotating or maneuvering platforms. Simultaneously, simply replicating the magnetic pole structure of current antimagnetic levitation systems in the direction requiring gravity counteraction would lead to problems such as magnetic field cancellation and insufficient detection space.

[0009] Taking the article "Room temperature test of the continuous spontaneous localization model using a levitated micro-oscillator" as an example, a four-level magnetic field was designed to combine magnetic force and gravity to form a three-dimensional potential well to suspend diamagnetic particles.

[0010] For diamagnetic particles, the minimum magnetic potential energy trapped by the particle occurs at the minimum magnetic field. To construct a potential well, first consider a linear quadrupole magnetic field that is symmetric about a horizontal axis and remains invariant when translated along that axis. Due to the zero change along this axis, this magnetic field confines the particle to the axis of symmetry, but the particle is unconstrained in the direction of the axis. To create a fully three-dimensional potential well, the paper distorts the shape of the magnetic field, causing the zero-field region to bend upwards at both ends of the magnetic field. The particle's motion is still confined by the magnetic field, remaining near the zero-field region in the direction perpendicular to the axis of symmetry, while the Earth's gravity minimizes the potential energy at the center of the bending symmetry, thus creating a fully three-dimensional potential well. The potential well is realized using quadrupole-shaped magnetic poles fabricated from a ferromagnetic material with high saturation magnetization. Two SmCo permanent magnets are placed between the pole pairs to generate the magnetic field. To create the upward curvature of the zero-field region in the horizontal direction, the top pole is cut shorter in the horizontal axis than the bottom pole, breaking the quadrupole symmetry.

[0011] The detection and control of microparticles are achieved by combining 830nm and 660nm diode lasers. The two laser beams are first coupled through a single-mode fiber to obtain a Gaussian beam. Illumination is achieved by focusing the 830nm laser, directing it laterally into the potential trap. Light transmitted through the trapping region and light scattered from the microparticles are collected using a self-made objective. This detection scheme achieves dark-field imaging of the microparticles by blocking the transmitted light from the back of the objective and imaging the scattered light onto a high-speed camera or photodiode. Imaging the microsphere onto a four-quadrant photodiode generates three electrical signals; the signals generated by the left-right and top-bottom differential currents are proportional to the particle's displacement in the direction perpendicular to the optical axis. The third signal, summed across all quadrants, can be used to sense motion along the optical axis. The detection optical path for the microparticles requires sufficient space between the magnetic poles.

[0012] If the four poles are rotated 90 degrees so that the axis of symmetry becomes vertical and in the same direction as gravity, the curvature of the zero-field region caused by the asymmetry of the magnetic poles will be insufficient to generate a magnetic force equal to gravity. This will prevent the stable capture of particles and limit the application of this magnetic levitation structure in mobile platforms. If the magnetic levitation structure is simply copied and rotated 90 degrees to balance gravity along the axis of symmetry, it will interfere with the original magnetic poles.

[0013] Taking "An Acceleration Measurement Method Based on an Antimagnetic Levitation System" (CN113484538A) as an example, the magnetic levitation structure is designed as an upper and lower double magnet layer with opposite polarization directions. On the one hand, the lower eight-level magnets converge magnetic field lines in the central region, generating a vertical magnetic field and magnetic field gradient, producing antimagnetic force to overcome the gravity of the antimagnetic particles, thus providing vertical constraint. On the other hand, by opening through holes in the geometric center of the upper eight-level magnets, horizontal constraint is provided, thereby forming a stable magnetic potential well. Permanent magnets are used to construct the antimagnetic levitation potential well. The permanent magnets are processed as follows: First, the permanent magnets are processed using a CNC machine tool and magnetized according to the design direction; second, the permanent magnets are assembled and fine-tuned, preferably using a metal support structure to assemble the permanent magnets, and the position of the permanent magnets is fine-tuned using screws, etc.; finally, the permanent magnets are encapsulated with epoxy resin. The antimagnetic microparticles are made of transparent antimagnetic materials, preferably graphite, quartz, PMMA (polymethyl methacrylate), or antimagnetic polymers.

[0014] The position measurement module inputs a laser signal to the diamagnetic particles. The measurement method for changes in laser intensity involves placing at least one set of optical fibers emitting the laser input signal on both sides of the diamagnetic particles, with each pair of fibers parallel to the others. The diamagnetic particles are designed as spherical, and a laser detection method is used, leveraging the focusing effect of the diamagnetic mass for transmission. When the diamagnetic mass shifts position under acceleration, it causes a change in the laser intensity in the output optical fiber of the diamagnetic particles. The position of the optical fiber emitting the laser input signal is fixed as follows: First, the fiber is moved to both sides of the spherical diamagnetic mass using a displacement manipulator for adjustment; second, the fiber is fixed when the dependence of the light intensity signal on the fiber position reaches its maximum. Two preferred methods for fixing the fiber are: passive fixing, i.e., permanently fixing the fiber position using epoxy resin or other adhesives; and a piezoelectric positioning device that finely adjusts the fiber position in real time according to environmental changes to ensure it is at the optimal operating point. When the optical fiber at the optimal operating point is fixed, the sphere suspended in the center of the antimagnetic levitation potential trap is a diamagnetic particle made of transparent diamagnetic material. When the laser signal is input from the left, it is converged by the diamagnetic particle and output to the right optical fiber, and then further transmitted to the photoelectric detection system.

[0015] This structure has the advantage of suspending large-sized particles, but when the structure is flipped, the direction of the vertical magnetic field gradient changes accordingly. The vertical antimagnetic force is in the same direction as gravity, which cannot provide a confinement effect on the particles. If a copy of this structure is made and symmetrically installed on top of the original structure, the magnetic potential trap region will form a closed space, making it impossible to achieve functions such as particle support and detection.

[0016] Therefore, to meet the requirements of three-dimensional antimagnetic particle suspension, it is necessary to design a new magnetic pole structure that can counteract gravity in an omnidirectional manner while taking into account the requirements of particle size and detection space, so as to meet the comprehensive application needs of high-sensitivity acceleration sensing systems. Summary of the Invention

[0017] To address the shortcomings of existing technologies, the present invention aims to provide a three-dimensional magnetic levitation structure for diamagnetic microparticles, thereby solving the problems mentioned in the background section. This invention, by proposing a three-dimensional diamagnetic microparticle magnetic levitation structure, fully utilizes the advantages of permanent magnet levitation, such as being passive, low-noise, and highly adaptable to various environments. It is compatible with a wide range of microparticle sizes and has high magnetic trap stiffness. Compared to existing four-stage and eight-stage magnetic levitation structures that can only counteract gravity in a specific direction, the three-dimensional magnetic levitation structure proposed in this invention has the characteristic of omnidirectional levitation, greatly expanding the application of diamagnetic microparticle magnetic levitation structures in fields such as motorized and rotating platforms.

[0018] The technical solution for achieving the objective of this invention is as follows: A three-dimensional magnetic levitation structure for diamagnetic microparticles includes: a permanent magnet, a cone-shaped soft magnet, diamagnetic microparticles, and a non-magnetic support. The permanent magnets described herein have three pairs installed in orthogonal directions of x, y, and z, wherein only two pairs of permanent magnets have the same magnetic pole direction; The cone-shaped soft magnet has three pairs, with a large end face and a small end face. The large end face is connected to the end of the permanent magnet facing the center, and the small end face faces the center of the three-dimensional magnetic levitation structure. The aforementioned antimagnetic particles are suspended at the center of the magnetic levitation structure composed of the permanent magnet and the soft magnet; The non-magnetic bracket is used to fix and install the permanent magnet and the soft magnet.

[0019] The permanent magnet has an axisymmetric structure, including cylinders and square prisms.

[0020] The permanent magnet is made of high-strength permanent magnet materials, including rubidium iron boron and samarium cobalt.

[0021] The permanent magnet is equidistant from the center of the three-dimensional magnetic levitation structure.

[0022] The permanent magnet has two pairs of N poles and one pair of S poles facing the center of the assembly structure; or the permanent magnet has two pairs of S poles and one pair of N poles facing the center of the assembly structure.

[0023] The soft magnet has a conical axisymmetric structure, including cones and square pyramids.

[0024] The soft magnet is made of a high magnetic susceptibility soft magnetic material, including an iron-cobalt alloy.

[0025] The materials used for the antimagnetic particles are antimagnetic materials, including silicon, silicon dioxide, and plexiglass.

[0026] The diameter of the antimagnetic particles is 100 nanometers to 500 micrometers.

[0027] The present invention has at least the following beneficial effects: 1. The three-dimensional magnetic levitation structure of antimagnetic microparticles proposed in this invention does not require external energy input and has low noise characteristics compared to electrostatic levitation and optical levitation; the proposed antimagnetic levitation does not rely on a low temperature environment and can autonomously and effectively reduce system power consumption, and meets the characteristics of working at room temperature or low temperature environment compared to superconducting levitation. 2. This invention effectively concentrates the magnetic field strength by designing a structure of a strong permanent magnet plus a conical soft magnet, resulting in high magnetic trap stiffness. Under high-intensity magnetic field conditions, the magnetic trap space range can be adjusted by adjusting the spacing between the small ends of the soft magnet, which is compatible with a wide range of particle sizes and is beneficial for improving acceleration sensitivity. 3. The present invention has a strong magnetic field gradient in three orthogonal directions. Compared with existing four-level, eight-level, and double-layer magnetic levitation structures that can only counteract gravity in specific directions, the three-dimensional magnetic levitation structure proposed in this invention has the characteristic of non-directional levitation and can counteract gravity in any direction, which greatly broadens the application of antimagnetic microparticle magnetic levitation structures in fields such as motorized and rotating platforms. 4. The non-magnetic support structure proposed in this invention is compact. Compared with the simple replication and assembly of magnetic poles in existing magnetic levitation structures, it fully considers the space requirements of modules such as detection and cooling, and has strong practicality in antimagnetic levitation systems. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the magnetic structure of the three-dimensional magnetic levitation structure of the antimagnetic microparticles proposed in one embodiment of the present invention.

[0029] Figure 2 This is a partial enlarged view of the microparticle portion of the three-dimensional magnetic levitation structure of the antimagnetic microparticles proposed in one embodiment of the present invention.

[0030] Figure 3 This is a schematic diagram of the overall structure of the three-dimensional magnetic levitation structure of the antimagnetic microparticles proposed in one embodiment of the present invention.

[0031] Figure 4 This is a curve showing the change of vertical magnetic potential energy of the three-dimensional magnetic levitation structure of the antimagnetic microparticles proposed in one embodiment of the present invention as a function of distance from the center.

[0032] Figure 5 This is a curve showing the change of the horizontal magnetic potential energy of the three-dimensional magnetic levitation structure of the antimagnetic microparticles proposed in one embodiment of the present invention with the distance from the center.

[0033] Figure 6 This is a curve showing the change of the vertical magnetic trapping force of the three-dimensional magnetic levitation structure of antimagnetic microparticles as a function of the distance from the center, as proposed in one embodiment of the present invention.

[0034] In the diagram: 1. Upper z-axis permanent magnet; 2. Upper z-axis soft magnet; 3. Rear y-axis permanent magnet; 4. Rear y-axis soft magnet; 5. Right x-axis soft magnet; 6. Right x-axis permanent magnet; 7. Lower z-axis soft magnet; 8. Lower z-axis permanent magnet; 9. Front y-axis permanent magnet; 10. Front y-axis soft magnet; 11. Left x-axis permanent magnet; 12. Left x-axis soft magnet; 13. Diamagnetic microparticles; 14. Non-magnetic support frame; 15. Non-magnetic support end cap. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and embodiments. Addressing the problems of existing magnetic levitation structures, the main improvement of this invention is the design of symmetrically converging magnetic field lines in the vertical direction. This allows suspended particles to be stably captured even without considering gravity, thus eliminating dependence on gravity or the placement orientation of the magnetic levitation structure. To reduce the influence of the magnet on the optical path for particle position detection, this invention uses simulation calculations to optimize and reduce the space occupied by the magnet while meeting the capture requirements. It combines the advantages of permanent magnets and soft magnets, using permanent magnets to provide the magnetic field and soft magnets to converge the magnetic field lines, optimizing magnetic field performance while facilitating process implementation.

[0036] The present invention provides a three-dimensional magnetic levitation structure for antimagnetic microparticles, comprising: three pairs of permanent magnets installed in orthogonal directions, two pairs of magnetic poles having the same direction and a different direction from the third pair of magnetic poles; and three pairs of cone-shaped soft magnets installed in orthogonal directions, wherein the large end face of the cone-shaped soft magnets is in contact with the permanent magnets, and the small end face faces the center of the magnetic levitation structure. Figure 1 The components are, respectively, the upper z-axis permanent magnet 1, the upper z-axis soft magnet 2, the rear y-axis permanent magnet 3, the rear y-axis soft magnet 4, the right x-axis soft magnet 5, the right x-axis permanent magnet 6, the lower z-axis soft magnet 7, the lower z-axis permanent magnet 8, the front y-axis permanent magnet 9, the front y-axis soft magnet 10, the left x-axis permanent magnet 11, and the left x-axis soft magnet 12.

[0037] Figure 2 As shown, the antimagnetic particles 13 are suspended near the center of the magnetic levitation structure composed of the permanent magnet and the soft magnet.

[0038] Figure 3 As shown, the non-magnetic support includes a non-magnetic support frame 14 and a non-magnetic support end cap 15, which positions and installs the permanent magnet and soft magnet at the required positions, and reserves enough space to meet the functional requirements such as detection.

[0039] The main factor affecting the performance of a magnetic levitation system is the gradient of the square of the magnetic flux density. This invention improves the magnetic flux density by employing high-strength permanent magnets and by optimizing the structure of soft magnets to increase the rate of change of magnetic flux density with space. The permanent magnets described in this invention have an equiaxially symmetrical structure, such as cylindrical or quadrangular prisms. The permanent magnets are made of high-strength permanent magnet materials such as neodymium iron boron and samarium cobalt. The distance between the permanent magnets and the center of symmetry of the assembly is equal. The two pairs of N poles and one pair of S poles of the permanent magnets face the center of the assembly structure, or the two pairs of S poles and one pair of N poles of the permanent magnets face the center of the assembly structure.

[0040] The soft magnet has a cone-shaped axisymmetric structure, such as a cone or a square pyramid, and the material of the soft magnet is a soft magnetic material with high magnetic susceptibility, such as an iron-cobalt alloy.

[0041] The antimagnetic microparticle material is an antimagnetic material such as silicon, silicon dioxide, or plexiglass, and the diameter of the microparticles ranges from 100 nanometers to 500 micrometers.

[0042] The characteristic parameters of the antimagnetic particles are determined by the sensitivity requirements of the levitation system and the detection scheme. The structure, material parameters, and assembly relationships of the permanent magnets and soft magnets in the magnetic levitation structure assembly are designed based on the characteristic parameters of the antimagnetic particles, using finite element simulation calculations of the magnetic induction intensity distribution in the levitation region, and verified experimentally.

[0043] Figure 1 The installation steps for the three-dimensional magnetic levitation structure of the antimagnetic particles shown are as follows: 1) Arrange the three orthogonal soft magnets and permanent magnets according to... Figure 1 As shown, install the non-magnetic bracket, and immediately secure it with the end cap after each direction is installed. During the installation of the permanent magnets, ensure the magnetic pole direction is consistent with the design. All end caps and fixing accessories used are made of non-magnetic materials. Pay attention to adjusting the alignment accuracy of each pair of soft magnets in real time; if necessary, shims can be used to adjust the structural gaps.

[0044] 2) Support the antimagnetic particles near the center of the suspension structure so that they can be captured by the magnetic trap. The support method can be a variety of support methods such as vibration desorption method and spray suspension method.

[0045] The three-dimensional magnetic levitation structure of antimagnetic particles proposed in this invention is based on passive materials such as permanent magnets and soft magnets. Compared with electrostatic levitation and optical levitation, it does not require external energy input and has the characteristics of low noise. The proposed antimagnetic levitation does not rely on a low temperature environment and can autonomously and effectively reduce system power consumption. Compared with superconducting levitation, it meets the characteristics of working at room temperature or low temperature.

[0046] This invention effectively concentrates magnetic field strength and achieves high magnetic trap stiffness by designing a structure of strong permanent magnets plus conical soft magnets. Under high magnetic field conditions, the magnetic trap space range can be adjusted by adjusting the spacing between the small ends of the soft magnets, accommodating a wide range of particle sizes and improving the system's acceleration sensitivity. Under the same levitation magnetic field strength requirements, compared to a magnetic pole structure composed of closely packed permanent magnets, this invention features less magnetic field cancellation, higher space utilization, and a more compact structure.

[0047] This invention features strong magnetic field gradients in three orthogonal directions. Compared to existing four-level, eight-level, and double-layer magnetic levitation structures that can only counteract gravity in specific directions, the three-dimensional magnetic levitation structure proposed in this invention has the characteristic of omnidirectional levitation and can counteract gravity in any direction, greatly expanding the application of antimagnetic microparticle magnetic levitation structures in fields such as motorized and rotating platforms.

[0048] The non-magnetic support structure proposed by the present invention is compact. Compared with the simple replication and assembly of magnetic poles in the existing magnetic levitation structure, it fully considers the space requirements of modules such as detection and cooling, and has strong practicability in the anti-magnetic levitation system. Embodiment

[0049] As Figure 1 shown, taking a spherical particle made of silicon with a diameter of 500 microns as an example, a three-dimensional magnetic levitation structure based on a neodymium iron boron quadrangular prism permanent magnet and an iron cobalt alloy quadrangular pyramid soft magnet is designed.

[0050] The magnetic induction intensity is obtained by finite element simulation calculation. Due to the converging effect of the conical soft magnet on the magnetic force lines, the magnetic induction intensity reaches the maximum value at the end face of the soft magnet close to the center of the magnetic trap; by selecting rubidium iron boron permanent magnetic material and cooperating with iron cobalt alloy soft magnetic material, the maximum value of the magnetic induction intensity can reach 4.18 T. Due to the repulsive effect of the magnetic field directions generated by a pair of permanent magnets in each direction, the magnetic induction intensity reaches the minimum value at the center of the magnetic trap, and the change value of the magnetic induction intensity within the range of ±0.5 mm from the center of the magnetic trap can reach 3 T, providing the basic conditions for the capture of anti-magnetic particles.

[0051] The formula for calculating the magnetic potential energy of the particle in this magnetic trap is: In the formula, χ is the magnetic susceptibility of the anti-magnetic material of the particle, B is the magnetic induction intensity of the magnetic field where the particle is located, V is the volume of the particle, μ 0 is the vacuum magnetic permeability. Substituting the calculation result of the magnetic induction intensity into the above formula, the magnetic potential energy of the magnetic trap shown in Figure 1 can be calculated.

[0052] The curves of the magnetic potential energy in the vertical direction and the horizontal direction changing with the distance from the center are respectively as shown in Figure 4 and Figure 5 shown. It can be seen that the depth of the magnetic potential energy of this magnetic trap is much greater than the kinetic energy of the thermal motion of the particle k B T , where k B is the Boltzmann constant, T is the absolute temperature. Therefore, it is very difficult for the captured particle to escape from the magnetic trap.

[0053] The condition for particle capture is that the magnetic trap force is balanced with the gravity, and the expression formula is: Where m is the mass of the particle, g is the gravitational acceleration, y is the vertical coordinate, yeq is the coordinate of the equilibrium position between the magnetic trap force and the gravity. Based on the above formula, according to Figure 4 the curve of the vertical magnetic potential energy varying with the distance from the center shown, the curve of the vertical magnetic trap force varying with the distance from the center can be calculated, as Figure 6 shown. The calculated gravity of the particle is 1.6975875e-6. At the Figure 6 curve, the equilibrium position with the particle gravity is found to be about 130 microns below the center of the structure. Therefore, Figure 1 the magnetic trap shown can balance the gravity and suspend a 500-micron silicon particle. And from Figure 6 it can be seen that the monotonicity of the magnetic trap force is good within a range of 920 microns in the vertical direction, and the diamagnetic suspension system has a large linear measurement range.

[0054] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the appended claims.

Claims

1. A three-dimensional magnetic levitation structure for diamagnetic microparticles, characterized in that, include: Permanent magnets, cone-shaped soft magnets, diamagnetic microparticles, non-magnetic scaffolds; The permanent magnets are in three pairs, installed in orthogonal directions of x, y, and z, with only two pairs of permanent magnets having the same magnetic pole direction; The cone-shaped soft magnets are in three pairs, each with a large end face and a small end face. The large end face is connected to the end of the permanent magnet facing the center, and the small end face faces the center of the three-dimensional magnetic levitation structure. The aforementioned antimagnetic microparticles are suspended at the center of the magnetic levitation structure composed of the permanent magnet and the soft magnet; the diameter of the antimagnetic microparticles is 100 nanometers to 500 micrometers. The non-magnetic bracket is used to fix and install the permanent magnet and the soft magnet.

2. The three-dimensional magnetic levitation structure of diamagnetic microparticles as described in claim 1, characterized in that, The permanent magnet has an axisymmetric structure, including cylinders and square prisms.

3. The three-dimensional magnetic levitation structure of diamagnetic microparticles as described in claim 1, characterized in that, The permanent magnet is made of high-strength permanent magnet materials, including rubidium iron boron and samarium cobalt.

4. The three-dimensional magnetic levitation structure of diamagnetic microparticles as described in claim 1, characterized in that, The permanent magnet is equidistant from the center of the three-dimensional magnetic levitation structure.

5. The three-dimensional magnetic levitation structure of diamagnetic microparticles as described in claim 1, characterized in that, The permanent magnet has two pairs of N poles and one pair of S poles facing the center of the assembly structure; or the permanent magnet has two pairs of S poles and one pair of N poles facing the center of the assembly structure.

6. The three-dimensional magnetic levitation structure of diamagnetic microparticles as described in claim 1, characterized in that, The soft magnet has a conical axisymmetric structure, including cones and square pyramids.

7. The three-dimensional magnetic levitation structure of diamagnetic microparticles as described in claim 1, characterized in that, The soft magnet is made of a high magnetic susceptibility soft magnetic material, including an iron-cobalt alloy.

8. The three-dimensional magnetic levitation structure of diamagnetic microparticles as described in claim 1, characterized in that, The materials used for the antimagnetic particles are antimagnetic materials, including silicon, silicon dioxide, and plexiglass.

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