CN115864897A - Three-dimensional magnetic suspension structure of diamagnetic particles - Google Patents

Abstract

The invention discloses a three-dimensional magnetic suspension structure of diamagnetic particles, which comprises the following components: permanent magnet, cone-shaped soft magnet, diamagnetic particles and nonmagnetic bracket; the permanent magnets are arranged in three pairs in the directions of x, y and z, wherein the magnetic pole directions of one and only two pairs of permanent magnets are the same; the conical soft magnets are three pairs and are provided with large end faces and small end faces, the large end faces are connected with one ends, facing the center, of the permanent magnets, and the small end faces face the center of the three-dimensional magnetic suspension structure; the diamagnetic particles are suspended in the center of a magnetic suspension structure formed by the permanent magnet and the soft magnet; the non-magnetic support is used for fixedly mounting the permanent magnet and the soft magnet. The invention fully utilizes the advantages of passive permanent magnetic suspension, low noise, strong environmental adaptability and the like, and has large compatible particle size range and high magnetic trap rigidity; the invention has the characteristic of non-directional suspension, and greatly widens the application of the diamagnetic particle magnetic suspension structure in the fields of maneuvering, rotating platforms and the like.

Description

Three-dimensional magnetic suspension structure of diamagnetic particles

Technical Field

The invention relates to the technical field of particle suspension, in particular to a three-dimensional magnetic suspension structure of diamagnetic particles.

Background

The suspension technology weakens the clamping thermal noise, vibration and other environmental factor interference which is difficult to avoid by the traditional oscillator, so the suspension sensor has extremely high measurement sensitivity and has wide application and attractive prospect in the aspects of cell biology, weak mechanical sensing, high-sensitivity acceleration sensing, quantum physics and the like.

The existing suspended particle system mainly comprises three methods of laser suspension, electrostatic suspension and superconducting suspension, wherein the laser suspension has the maximum bandwidth in the suspension system, but is limited by the particle size, so that the acceleration sensitivity is limited; the electrostatic suspension is the most developed technology, the suspension body is controlled by a feedback circuit, but the acceleration sensitivity is limited due to the influence of electronic noise; superconducting levitation is a brand new technology which is proposed recently, the theoretical sensitivity is high, however, the superconducting levitation requires the system to work under the low temperature condition (less than 10K), and the application field range is limited.

The diamagnetic suspension technology adopting the permanent magnet to form the magnetic trap can suspend particles with the diameter of hundred microns, and has extremely high theoretical acceleration sensitivity; compared with electrostatic suspension and optical suspension, external energy input is not required, and the main noise source of the suspension system is reduced; in addition, the diamagnetic levitation system does not need to depend on a low-temperature environment and does not have the application temperature environment limit of superconducting levitation.

Taking the article "Lens-free Optical Detection of Thermal Motion of a Sub-millimeter suspended vibrator in High Vacuum" (Phys. Rev. Applied 16, L011003) as an example, based on the potential important role of millimeter or Sub-millimeter suspended vibrator in researching various basic problems and practical applications, aiming at the key technical requirement of effective measurement of suspended vibrator Motion, a lensless Optical Detection scheme is theoretically provided to detect the Motion of millimeter or Sub-millimeter suspended vibrator and detect the Motion of millimeter or Sub-millimeter suspended vibratorThe quantum efficiency is close to the standard quantum limit, and the optical power is moderate. Experiments prove that the microsphere with the diameter of 0.5mm resists magnetic suspension under high vacuum and room temperature, and the thermal motion can be detected with high precision. Based on the system, the calculated acceleration sensitivity is 0.97 ng/V Hz, which is improved by more than one order of magnitude compared with the optimal value reported by the suspension mechanics system. Due to the stability of the system, the minimum resolution acceleration reaches 3.5pg, and the measurement time is 10 ⁵ And second. This result has potentially important applications in the implementation of compact gravimeters and accelerometers.

Taking the article "coating the motion of a silica microsphere in a magnetic interaction trap in ultra-high vacuum" (Bradley R Slezak et al 2018 New J. Phys. 20 063028) as an example, magnetic attraction traps in ultra-high vacuum were studied. Unlike an optical potential well, a completely passive potential well is created for diamagnetic particles by the interaction of the magnetic field generated by the permanent magnet and the attractive force. The article demonstrates that the centroid motion of the captured silica microspheres is cooled from ambient temperature to an effective temperature with two degrees of freedom near or below 1mK by optical feedback damping. By utilizing the advantages of the suspension system, particularly the particles in vacuum, a unique platform is provided for researching the mechanical behavior of an object which is well isolated from the environment, and the basic problems of quantum mechanics, gravity and other weak forces can be researched. Overcomes the practical application problem of optical trapping of nanoparticles, as a typical suspended optical force system, due to the high light intensity heat required, especially when combined with a high vacuum environment.

Taking the article "from temperature test of the connected porous calibration model using a free micro-oscillator" (Phys. Rev. Research 2, 013057) as an example, a principle verification experiment for testing a collapse model by using an anti-magnetic suspension system is reported. Continuous Spontaneous Localization (CSL) models predict that small disruptions in energy conservation can be caused by weak random forces acting on the physical system. Mechanical vibrators are a suitable method of testing such forces, and suspended micro-vibrators in particular have recently been considered an ideal test system. The article reports a proof of principle experiment using a micro-oscillator suspended by a diamagnetic microsphere in a high vacuum magnetic attraction trap. Due to the ultra-low mechanical dissipation, the suspended vibrator provides a new upper limit for the CSL collapse rate, which is two orders of magnitude higher than the previous upper limit in the same frequency range, and partially reaches the enhanced collapse rate suggested by Adler. Although the experiment was performed at room temperature, advantages have been shown compared to experiments performed at low temperatures. The experiment result shows that the magnetic attraction suspension mechanical vibrator has strong potential as a promising method for testing the collapse model.

However, the current anti-magnetic suspension system mainly focuses on laboratory research, the platform is mostly a non-rotating and non-motorized platform, the adopted magnetic suspension structure is mostly a unidirectional counteracting gravity, and the other directions have no magnetic trap force or weak magnetic trap force, so that the requirement of gravity balance cannot be met. At present, the diamagnetic suspension system cannot capture diamagnetic particles when the platform is overturned, and the application of the diamagnetic particle suspension system on actual platforms such as rotating platforms and maneuvering platforms is severely limited. Meanwhile, if the magnetic pole structure form of the existing anti-magnetic suspension system is simply copied and installed in the direction needing gravity offset, the problems of magnetic field offset, insufficient detection space and the like can be caused.

Taking the article of road temperature test of the connected magnetic suspension model using a free magnetic-field, a four-level magnetic field is designed, and magnetic force and gravity are combined to form three-dimensional potential well suspended antimagnetic particles.

For diamagnetic particles, the magnetic field potential energy minimum at which the particle is trapped occurs at the magnetic field minimum. To construct a potential well, consider first a linear quadrupole magnetic field that is symmetric about a horizontal axis and does not change when translated along that axis. Such a magnetic field confines the particle to the axis of symmetry due to zero variation along the axis, but the particle is unconstrained in the direction of the axis. To make a full three-dimensional potential well, the article distorts the shape of the magnetic field, causing the zero-field region to bend upward at both ends of the magnetic field. The movement of the particles is still limited by the magnetic field, which remains 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 complete three-dimensional potential well. The potential well is realized by using magnetic poles with four-level shapes and is made of ferromagnetic materials with high saturation magnetization. Two SmCo permanent magnets are placed between the pole piece pair to generate a magnetic field. To create an 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 four-level symmetry.

Detection and control of particles is achieved by a combination of 830nm and 660nm diode lasers, the two laser beams being first coupled through a single mode fibre to obtain a gaussian beam. Illumination was achieved by focusing the 830nm laser, from the lateral direction into the potential well. Both the light transmitted through the capture zone and the light scattered from the microparticles are collected by the homemade objective lens. The detection scheme realizes dark field imaging of particles by blocking transmitted light at the back of an objective lens and imaging scattered light onto a high-speed camera or a photodiode. Imaging the microsphere onto a four-quadrant photodiode to generate three electrical signals; the signals generated by the left-right and up-down difference currents are respectively proportional to the displacement of the particles in the direction perpendicular to the optical axis. The third signal adds all quadrants and can be used to sense motion in the direction of the optical axis. The detection light path of the particles requires enough space for the magnetic poles.

If the four stages are rotated by 90 degrees, so that the symmetry axis is changed into a vertical direction, which is the same as the gravity direction, the bending curvature of a zero field area caused by the asymmetry of the magnetic poles is not enough to generate a magnetic force equal to the gravity, particles cannot be stably captured, and the application of the magnetic suspension structure on a mobile platform is limited. If the magnetic suspension structure is simply copied and installed by rotating 90 degrees in order to balance the gravity in the direction of the symmetry axis, the magnetic suspension structure interferes with the original magnetic pole.

Taking "an acceleration measurement method based on an anti-magnetic levitation mechanics system" (CN 113484538 a) as an example, by designing a magnetic levitation structure as an upper and lower double-magnet layer with opposite polarization directions, on one hand, a lower eight-stage magnet converges magnetic lines of force in a central area to generate a magnetic field and a magnetic field gradient in a vertical direction, so as to generate an anti-magnetic force for overcoming the gravity of anti-magnetic particles and provide a constraint in the vertical direction; on the other hand, a through hole is formed in the geometric center direction of the upper eight-level magnet, so that horizontal constraint is provided, and a stable magnetic potential well is formed. Adopting a permanent magnet to form a diamagnetic suspension potential well, and processing the permanent magnet: firstly, processing a permanent magnet by using a numerical control machine tool, and magnetizing the permanent magnet according to a design direction; secondly, the permanent magnets are combined and finely adjusted, preferably, the permanent magnets are installed and combined through a metal supporting structure, and the positions of the permanent magnets are finely adjusted through screws and the like; finally, the permanent magnet is encapsulated by epoxy. The diamagnetic particles are made of transparent diamagnetic materials, and the preferred diamagnetic materials are graphite, quartz, organic glass PMMA or diamagnetic high polymer materials.

The position measurement module inputs laser signals to the diamagnetic particles, and the change of the laser light intensity is measured in a mode that at least one group of optical fibers for transmitting the laser input signals are arranged on two sides of the diamagnetic particles, wherein every two optical fibers are relatively parallel; the diamagnetic particles are designed to be spherical, and transmission is realized by the focusing effect of the diamagnetic mass body by adopting a laser detection method; when the diamagnetic mass is displaced under the acceleration, the intensity of the laser light in the optical fiber outputting the diamagnetic particles is changed. The optical fiber position fixing mode for transmitting the laser input signal is as follows: firstly, moving the position of an optical fiber to two sides of a spherical diamagnetic mass body through a displacement operating platform for adjustment; secondly, when the dependency of the light intensity signal and the optical fiber position reaches the maximum, the optical fiber is fixed. The fixing method of the optical fiber is preferably two methods: on the one hand, passive fixation, i.e., permanent fixation of the fiber position using epoxy or other adhesive; on the other hand, the position of the optical fiber is finely adjusted in real time according to the change of the environment through a piezoelectric positioning device, so that the optical fiber is positioned at the optimal working point. When the optical fiber of the optimal working point is fixed, the ball suspended in the center of the diamagnetic suspension potential well is diamagnetic particles and is made of transparent diamagnetic materials, when a laser signal is input from the left side, the laser signal is output to the right optical fiber through convergence of the diamagnetic particles and is further transmitted to the photoelectric detection system.

The structure has the advantage of large size of suspended particles, but when the structure is turned over, the gradient direction of a magnetic field in the vertical direction is changed along with the structure, the coercive force in the vertical direction is the same as the gravity direction, and the particle cannot be restrained. If the structure is copied and symmetrically arranged on the upper part of the original structure, the magnetic potential trap area forms a closed space, and the functions of supporting and detecting particles cannot be realized.

Therefore, aiming at the three-dimensional anti-magnetic particle suspension requirement, a new magnetic pole structure form needs to be designed, the requirements of particle size, detection space and the like can be considered while the gravity is counteracted in a non-directional manner, and the comprehensive application requirement of the high-sensitivity acceleration sensing system is met.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a three-dimensional magnetic suspension structure of diamagnetic particles so as to solve the problems in the background technology. By providing the three-dimensional diamagnetic particle magnetic suspension structure, the invention fully utilizes the advantages of passive permanent magnetic suspension, low noise, strong environmental adaptability and the like, and has large compatible particle size range and high magnetic trap rigidity; compared with the existing four-stage and eight-stage magnetic suspension structures which can only counteract the gravity in a specific direction, the three-dimensional magnetic suspension structure provided by the invention has the characteristic of non-directional suspension, and the application of the diamagnetic particle magnetic suspension structure in the fields of maneuvering, rotating platforms and the like is greatly widened.

The technical scheme for realizing the purpose of the invention is as follows:

a three-dimensional magnetically levitated structure of diamagnetic particles comprising: permanent magnet, cone-shaped soft magnet, diamagnetic particles and nonmagnetic bracket;

the permanent magnets are provided with three pairs, are arranged in the x, y and z orthogonal directions, and the magnetic pole directions of only two pairs of permanent magnets are the same;

the conical soft magnets are provided with three pairs of large end faces and small end faces, the large end faces are connected with one ends, facing the center, of the permanent magnets, and the small end faces face the center of the three-dimensional magnetic suspension structure;

the diamagnetic particles are suspended in the center of a magnetic suspension structure formed by the permanent magnet and the soft magnet;

the non-magnetic support is used for fixedly mounting the permanent magnet and the soft magnet.

The permanent magnet is of an axisymmetric structure and comprises a cylinder and a quadrangular prism.

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

And the distances between the permanent magnet and the center of the three-dimensional magnetic suspension structure are equal.

The two pairs of N poles and the one pair of S poles of the permanent magnet face the center of the structure of the assembly body; or two pairs of S poles and one pair of N poles of the permanent magnet face the center of the structure of the assembly body.

The soft magnet is in a cone-shaped axisymmetric structure and comprises a cone and a rectangular pyramid.

The soft magnet is made of a high-magnetic-susceptibility soft magnetic material comprising iron-cobalt alloy.

The diamagnetic particles are made of diamagnetic materials including silicon, silicon dioxide and organic glass.

The diamagnetic particles have a diameter of 100 nanometers to 500 micrometers.

The invention at least comprises the following beneficial effects:

1. compared with electrostatic suspension and optical suspension, the three-dimensional magnetic suspension structure of the diamagnetic particles does not need external energy input, and has the characteristic of low noise; the proposed diamagnetic suspension does not need to depend on a low-temperature environment, can independently and effectively reduce the power consumption of a system, and meets the characteristic of working at room temperature or low-temperature environment relative to superconducting suspension;

2. according to the invention, by designing the structure of the strong magnetic permanent magnet and the cone-shaped soft magnet, the magnetic field intensity is effectively converged, and the rigidity of the magnetic trap is high; under the condition of a high-strength magnetic field, the space range of the magnetic trap can be adjusted by adjusting the plane distance of the small end of the soft magnet, the compatible particle size range is large, and the acceleration sensitivity is favorably improved;

3. the three-dimensional magnetic suspension structure has the characteristic of non-directional suspension, can counteract the gravity in any direction, and greatly broadens the application of the magnetic suspension structure of diamagnetic particles in the fields of maneuvering, rotating platforms and the like;

4. compared with the simple copy assembly of the magnetic pole of the existing magnetic suspension structure, the non-magnetic bracket provided by the invention has a compact structure, fully considers the space requirements of modules such as detection, cooling and the like, and has strong practicability in a magnetic suspension resisting system.

Drawings

Fig. 1 is a schematic view of a magnetic structure portion of a three-dimensional magnetic suspension structure of diamagnetic particles according to an embodiment of the invention.

Fig. 2 is a partially enlarged view of a particle portion of a three-dimensional magnetic levitation structure of the diamagnetic particles according to an embodiment of the invention.

Fig. 3 is a schematic diagram of an overall structure of a three-dimensional magnetic levitation structure of diamagnetic particles according to an embodiment of the present invention.

Fig. 4 is a graph showing the variation of vertical magnetic potential energy of the three-dimensional magnetic suspension structure of diamagnetic particles according to the off-center distance in an embodiment of the present invention.

Fig. 5 is a graph showing the variation of the horizontal magnetic potential energy of the three-dimensional magnetic suspension structure of the diamagnetic particles according to the off-center distance in an embodiment of the present invention.

Fig. 6 is a vertical magnetic trapping force curve with respect to the distance from the center of the bias for the three-dimensional magnetic suspension structure of anti-magnetic particles according to an embodiment of the present invention.

In the figure: the device comprises a z-axis upper permanent magnet 1, a z-axis upper soft magnet 2, a y-axis rear permanent magnet 3, a y-axis rear soft magnet 4, an x-axis right soft magnet 5, an x-axis right permanent magnet 6, a z-axis lower soft magnet 7, a z-axis lower permanent magnet 8, a y-axis front permanent magnet 9, a y-axis front soft magnet 10, an x-axis left permanent magnet 11, an x-axis left soft magnet 12, diamagnetic particles 13, a nonmagnetic support frame 14 and a nonmagnetic support end cover 15.

Detailed Description

The invention is further illustrated below with reference to the figures and examples. Aiming at the problems of the existing magnetic suspension structure, the invention mainly improves the idea that magnetic lines of force are symmetrically converged up and down in the vertical direction, so that suspended particles can be stably captured without considering the gravity, thereby getting rid of the dependence on the gravity or the arrangement direction of the magnetic suspension structure. In order to reduce the influence of the magnet on the particle position detection light path, the invention optimizes and reduces the occupied space of the magnet by a simulation calculation method under the condition of meeting the requirement of a capturing condition; the advantages of the permanent magnet and the soft magnet are combined, the permanent magnet is used for providing a magnetic field, and the soft magnet is used for gathering magnetic lines of force, so that the process implementation is facilitated while the performance of the magnetic field is optimized.

The invention provides a three-dimensional magnetic suspension structure of diamagnetic particles, which comprises: three pairs of permanent magnets are arranged in the orthogonal direction, and the directions of the two pairs of magnetic poles are the same and are different from the direction of the third pair of magnetic poles; the large end face of the cone-shaped soft magnet is contacted with the permanent magnet, and the small end face of the cone-shaped soft magnet faces to the center of the magnetic suspension structure; in fig. 1, there are a z-axis upper permanent magnet 1, a z-axis upper soft magnet 2, a y-axis rear permanent magnet 3, a y-axis rear soft magnet 4, an x-axis right soft magnet 5, an x-axis right permanent magnet 6, a z-axis lower soft magnet 7, a z-axis lower permanent magnet 8, a y-axis front permanent magnet 9, a y-axis front soft magnet 10, an x-axis left permanent magnet 11, and an x-axis left soft magnet 12, respectively.

As shown in fig. 2, diamagnetic particles 13 are suspended near the center of the magnetic suspension structure formed by the permanent magnets and the soft magnets.

As shown in fig. 3, the nonmagnetic support comprises a nonmagnetic support frame 14 and a nonmagnetic support end cover 15, the permanent magnet and the soft magnet are positioned and installed at a required position, and enough space is reserved to meet functional requirements such as detection.

The factors influencing the performance of the magnetic suspension system are mainly the square gradient of the magnetic induction intensity, on one hand, the magnetic induction intensity is improved by adopting a high-intensity permanent magnet, and on the other hand, the change rate of the magnetic induction intensity along with the space is improved by optimizing the structural form of a soft magnet. The permanent magnet is in a cylindrical and quadrangular equiaxial symmetric structure, the permanent magnet is made of high-strength permanent magnet materials such as rubidium, iron, boron, samarium, cobalt and the like, the distances between the permanent magnet and the symmetric center of an assembly body are equal, two pairs of N poles and one pair of S poles of the permanent magnet face to the center of the structure of the assembly body, or two pairs of S poles and one pair of N poles of the permanent magnet face to the center of the structure of the assembly body.

The soft magnet is in a conical axisymmetric structure such as a cone, a rectangular pyramid and the like, and the material of the soft magnet is a high-magnetic-susceptibility soft magnet material such as iron-cobalt alloy and the like.

The diamagnetic particle material is a diamagnetic material such as silicon, silicon dioxide and organic glass, and the diameter range of the particles is not less than 100 nanometers-500 micrometers.

The characteristic parameters of the diamagnetic particles are determined by the sensitivity index requirements of the suspension system and the detection scheme. The magnetic induction intensity distribution result design of the suspension area is calculated by finite element simulation on the basis of determining the characteristic parameters of diamagnetic particles, and the magnetic induction intensity distribution result design is verified by experiments.

The installation steps of the three-dimensional magnetic suspension structure of the diamagnetic particles shown in the figure 1 are as follows:

1) Soft magnets and permanent magnets in three orthogonal directions are respectively installed in a non-magnetic bracket according to the drawing of figure 1, and an end cover is used for crimping and fixing in time after one direction is installed. In the process of mounting the permanent magnet, the direction of the magnetic pole is the same as the design, and the materials of the end cover and the fixed accessory are non-magnetic materials. And the alignment precision of each pair of soft magnets is regulated in real time, and a spacer can be adopted to regulate the structural gap if necessary.

2) The diamagnetic particles are supported near the center of the suspension structure so as to be captured by the magnetic trap, and the supporting method can be various supporting methods such as a vibration desorption method and a spray suspension method.

The diamagnetic particle three-dimensional magnetic suspension structure is based on passive materials such as permanent magnets, soft magnets and the like, does not need external energy input relative to electrostatic suspension and optical suspension, and has the characteristic of low noise; the anti-magnetic suspension does not need to depend on a low-temperature environment, can independently and effectively reduce the power consumption of the system, and meets the characteristic of working at room temperature or low-temperature environment compared with superconducting suspension.

According to the invention, by designing the structure of the strong magnetic permanent magnet and the cone-shaped soft magnet, the magnetic field intensity is effectively converged, and the rigidity of the magnetic trap is high; under the condition of a high-strength magnetic field, the space range of the magnetic trap can be adjusted by adjusting the plane distance of the small end of the soft magnet, the compatible particle size range is large, and the acceleration sensitivity of a system is favorably improved; under the condition of the same magnetic field intensity requirement of suspension, compared with a magnetic pole structure formed by densely arranging permanent magnets, the magnetic pole structure has the characteristics of small magnetic field offset, high space utilization rate and compact structure.

The three-dimensional magnetic suspension structure provided by the invention has the characteristic of non-directional suspension, can counteract the gravity in any direction, and greatly widens the application of the magnetic suspension structure for resisting magnetic particles in the fields of maneuvering, rotating platforms and the like.

Compared with the simple copy assembly of the magnetic pole of the existing magnetic suspension structure, the non-magnetic bracket provided by the invention has a compact structure, fully considers the space requirements of modules such as detection, cooling and the like, and has strong practicability in a magnetic suspension resisting system.

Examples

As shown in fig. 1, a three-dimensional magnetic suspension structure based on a ru-fe-b quadrangular permanent magnet and an iron-cobalt alloy quadrangular pyramid soft magnet is designed by taking spherical particles with a diameter of 500 μm as an example.

The magnetic induction intensity is obtained by finite element simulation calculation. The magnetic induction intensity reaches the maximum value at the end face of the soft magnet close to the center of the magnetic trap due to the convergence effect of the cone-shaped soft magnet on magnetic lines; by selecting the rubidium iron boron permanent magnetic material and matching with the iron cobalt alloy soft magnetic material, the maximum value of the magnetic induction intensity can reach 4.18T. Because the pair of permanent magnets in each direction generate mutual repulsion action of magnetic field directions, the magnetic induction intensity reaches the minimum value at the center of the magnetic trap, the variation value of the magnetic induction intensity in the range of +/-0.5 mm at the center of the magnetic trap can reach 3T, and basic conditions are provided for capturing diamagnetic particles.

The magnetic potential energy of the particles in the magnetic trap is calculated by the formula:

in the formula (I), the compound is shown in the specification,χis the magnetic susceptibility of the particulate diamagnetic material,Bis the magnetic induction of the magnetic field in which the particles are located,Vis the volume of the particles,μ ₀ is a vacuum magnetic permeability. The magnetic potential of the magnetic trap shown in fig. 1 can be calculated by substituting the magnetic induction calculation result into the above formula.

Magnetic potential energy variation curve between vertical direction and horizontal direction along with off-center distanceAs shown in FIGS. 4 and 5, it can be seen that the magnetic potential of the magnetic trap is far greater than the kinetic energy of the thermal motion of the particlesk _B TWhereink _B Is the boltzmann constant, and is,Tabsolute temperature, trapped particles are difficult to escape the magnetic trap.

The condition of particle capture is the balance of magnetic trap force and gravity, and the expression is as follows:

whereinmThe mass of the particles is the mass of the particles,gin order to be the acceleration of the gravity,yis a coordinate in the vertical direction and is,y _eq is the magnetic trap force and gravity equilibrium position coordinate. Based on the above formula, according to the curve of the magnetic potential energy in the vertical direction along with the distance from the center as shown in fig. 4, the curve of the magnetic trap force in the vertical direction along with the distance from the center can be calculated as shown in fig. 6. The particle gravity is calculated to be 1.6975875e-6, and a position which is about 130 microns below the center of the structure and is balanced with the particle gravity is found on the curve of fig. 6, so that the magnetic trap shown in fig. 1 can exert a balancing force to suspend 500 micron silicon particles, and as can be seen from fig. 6, the monotonicity of the magnetic trap force in the range of 920 microns in the vertical direction is good, and the antimagnetic suspension system has a large linear measurement range.

The above examples are merely illustrative of several embodiments of the present invention, and the description thereof is more specific and detailed, but not to be construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims (9)

1. A three-dimensional magnetic suspension structure of diamagnetic particles, it is characterized by comprising: permanent magnet, cone-shaped soft magnet, diamagnetic particles and nonmagnetic bracket;

the permanent magnets are three pairs, are arranged in the orthogonal directions of x, y and z, and the magnetic pole directions of only two pairs of permanent magnets are the same;

the conical soft magnets are three pairs and are provided with large end faces and small end faces, the large end faces are connected with one ends, facing the center, of the permanent magnets, and the small end faces face the center of the three-dimensional magnetic suspension structure;

the diamagnetic particles are suspended in the center of a magnetic suspension structure formed by the permanent magnets and the soft magnets;

the non-magnetic bracket is used for fixedly mounting the permanent magnet and the soft magnet.

2. The three-dimensional magnetic levitation structure of diamagnetic particles according to claim 1, wherein the permanent magnet is an axisymmetric structure comprising a cylinder and a quadrangular prism.

3. The three-dimensional magnetic levitation structure of diamagnetic particles as recited in claim 1 wherein the permanent magnets are made of high strength permanent magnet materials comprising rubidium iron boron and samarium cobalt.

4. Three-dimensional magnetic levitation structure of diamagnetic particles according to claim 1, wherein the permanent magnets are equidistant from the center of the three-dimensional magnetic levitation structure.

5. The three-dimensional magnetic levitation structure of diamagnetic particles according to claim 1, wherein two pairs of N poles and one pair of S poles of the permanent magnets face to the center of the assembly structure; or two pairs of S poles and one pair of N poles of the permanent magnet face the center of the structure of the assembly body.

6. Three-dimensional magnetic levitation structure of diamagnetic particles according to claim 1, wherein the soft magnet is a cone-shaped axisymmetric structure comprising a cone and a rectangular pyramid.

7. Three-dimensional magnetic levitation structure of diamagnetic particles according to claim 1, wherein the material of the soft magnet is a high-magnetic-susceptibility soft magnetic material comprising an iron-cobalt alloy.

8. The three-dimensional magnetic levitation structure of diamagnetic particles as claimed in claim 1, wherein the diamagnetic particles are made of diamagnetic materials including silicon, silicon dioxide and organic glass.

9. The three-dimensional magnetic levitation structure of diamagnetic particles according to claim 1, wherein the diamagnetic particles have a diameter of 100 nm to 500 μm.

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