CN106179760A - A kind of dry type molecule separation method - Google Patents

Abstract

The invention provides a dry micro particle separation method. In this method, an upper plate, a lower plate, a particle pool, and a particle separator are arranged in the vacuum chamber, and a radio frequency power supply, a semiconductor laser, a chopper, and a beam expander are arranged outside the vacuum chamber; A uniform plasma is generated between them. The particle separator is located on the lower plate, which includes the ratchet surface groove in the middle and the collection boxes at both ends; the particles scattered from the particle pool can be in a suspended state in the ratchet surface groove; adjust the power of the semiconductor laser and the chopper Frequency, so that the laser is irradiating the particles, and the particles are driven to form oscillations of a specific frequency, so that particles of different sizes move in opposite directions in the groove of the ratchet surface to complete the separation. The invention can realize the separation of tiny particles with extremely low content. The invention is simple and convenient to operate, and provides a solution for rapid separation in laboratories and industrial fields.

Description

A dry microparticle separation method

technical field

The invention relates to a particle separation method, in particular to a dry micro particle separation method.

Background technique

The separation of one or several microparticles is a very meaningful work, and has great application prospects in sample storage, physical property analysis of particles, biochemical analysis, and further formation of functional integrated chips. The current separation methods are divided into dry method and wet method. Wet separation includes the method of separating particles in microflow. The more effective physical methods are usually electrophoresis technology using uniform electric field, dielectrophoresis technology based on inhomogeneous electric field, magnetophoresis technology based on inhomogeneous magnetic field, and acoustophoresis technology based on sound waves . In these methods, particles of different sizes flow to different channels under the action of force, so that spatial separation can be achieved.

In addition, a separation method based on the solubility and adsorption properties of substances is called chromatography. The separation principle is based on the difference between the components of the mixture and the two incompatible phases (stationary phase and mobile phase). Among them, wet-type high-performance liquid chromatography (HPLC) has the characteristics of high separation efficiency, fast speed, and high detection sensitivity, making it widely used and developing rapidly. However, the equipment of HPLC is expensive and the operation is strict. Dry gas chromatography is used to determine substances or compounds that can be vaporized or converted into gases, and is divided into gas-solid chromatography (GSC) and gas-liquid chromatography (GLC). It is worth mentioning that there is a method in dry separation called photochromatography, which is an optical separation technology that utilizes the balance between the light radiation pressure from a weakly focused beam and the drag force given by the fluid to achieve different size particles. Separation at different equilibrium positions. Similarly, the same chromatography cannot avoid the main disadvantage of complicated and strict operation. The cleaning of the chromatographic column is also complicated and time-consuming, and the separation difficulty suddenly increases when the content of the target substance is too low.

Contents of the invention

The purpose of the present invention is to provide a dry micro particle separation method to solve the problems of cumbersome operation, long processing time and low separation precision in the existing dry and wet separation techniques.

The present invention is achieved in this way: a dry micro particle separation method comprises the following steps:

a. A vacuum chamber is set, and two upper and lower pole plates are horizontally arranged in the vacuum chamber; the upper pole plate is grounded, the lower pole plate is connected to a power electrode of a radio frequency power supply, and the other electrode of the radio frequency power supply is grounded Wire;

b. A particle separator is arranged on the lower plate, and the particle separator includes a ratchet curved surface groove formed by successively adjacent concave ratchet teeth in the middle part and collection boxes at both ends;

c. A particle pool is set above the ratchet surface groove, and two different sizes of micron-scale particles to be separated are contained in the particle pool; the particle pool and the vibrating rod passing through the vacuum chamber connected;

d. Two opposite semiconductor lasers are arranged outside the vacuum chamber, and each semiconductor laser corresponds to a collection box in the particle separator; a chopper is respectively arranged in front of each semiconductor laser, and A beam expander mirror is arranged in front of each chopper;

e. Turn on the radio frequency power supply, and generate uniform plasma between the upper plate and the lower plate through gas discharge;

f. Make the vibrating rod vibrate outside the vacuum chamber, and then drive the particle pool in the vacuum chamber to vibrate, so that the particles to be separated in the particle pool are scattered from the particle pool; the scattered particles are in the plasma region Negatively charged, and form a stable and dispersed suspension system in the ratchet curved groove near the top of the lower plate;

g. Turn on the switch of the semiconductor laser and the chopper, so that the laser light emitted by the semiconductor laser is irradiated on the suspended particles in the vacuum chamber;

h. Adjust the pulse frequency of the chopper so that the particles of two different sizes in the particles to be separated move in two opposite directions along the axis of the ratchet surface groove;

i. When the particles of two different sizes reach the top of the two collection boxes respectively, the radio frequency power supply is disconnected, and the particles freely fall into the corresponding collection boxes, thereby realizing the separation of the two different sizes of particles.

In the step e, the frequency of the radio frequency power supply is adjusted to 13.56MHz, and the power is 1~60W.

The semiconductor laser, the chopper and the beam expander are all arranged on an elevating platform, and the elevating platform is connected with a stepping motor.

The stepper motor, the semiconductor laser and the chopper are all connected to a controller, and the controller is used to control the operation of the stepper motor on the one hand to drive the lifting table to move up and down, thereby realizing the adjustment of the The height of the semiconductor laser, the chopper and the beam expander; on the other hand, it is used to control the irradiation time of the semiconductor laser and the pulse frequency of the chopper.

In step g, the center wavelength of the laser light emitted by the semiconductor laser is 532nm or 650nm, and the power range of the semiconductor laser is 0.01-2W.

The curved surface curvature of the ratchet curved groove is 180°.

The collection box is formed by setting semicircular short edges on both sides of the concave semicircular groove.

The tooth depth and tooth length ratio of the ratchet is 1:2.

The vacuum chamber is surrounded by a stainless steel cavity, and the stainless steel cavity is grounded; two opposite side windows are provided on the side wall of the stainless steel cavity, and each side window corresponds to a semiconductor laser; in step g, The laser light emitted by the semiconductor laser is irradiated onto the suspended particles in the vacuum chamber through the corresponding side window.

The particle pool is formed by pressing multilayer metal meshes of different meshes; the vibrating rod is arranged vertically, and the particle pool is connected to the vibrating rod through a horizontally arranged insulating rod.

In the present invention, an upper pole plate, a lower pole plate, a particle pool, and a particle separator are arranged in the vacuum chamber, and a radio frequency power supply, a semiconductor laser, a chopper, and a beam expander are arranged outside the vacuum chamber, and the radio frequency power supply is connected. A uniform plasma is generated between the upper and lower plates, and the components of the plasma mainly include electrons, ions and neutral molecules. When the tiny particles to be separated (usually micron-scale particles of two different sizes) are scattered from the particle pool into the plasma environment, the plasma will charge them. Since electrons diffuse faster than ions, particles carry a large negative charge when the flow of electrons and ions incident on the particle balances. When the particles fall into the sheath layer near the top of the lower plate due to gravity, and the gravity and electrostatic field force are balanced, the particles will be suspended near the top of the lower plate. At the same time, due to the high chargeability of the particles, the particles can be well dispersed to form a dispersed suspension system. Since the particle separator is located on the lower plate and is in the plasma environment, a ratchet-shaped plasma sheath is formed on the surface of the ratchet curved groove, which is a periodic potential that does not satisfy the inversion symmetry (in physics The ratchet potential satisfies symmetry breaking and can produce directional transport. The particles to be separated are dispersed and suspended in the ratchet-shaped plasma sheath. Particles of different sizes have different charged quantities, are suspended at different heights, and have different natural frequencies. The resonance frequency generated under laser pulse irradiation (the resonance frequency is inversely proportional to the particle radius and proportional to the particle charge) is also different. Through By adjusting the pulse frequency of the chopper, particles of two different sizes can be controlled to move in opposite directions, and finally the particles of two different sizes are collected by two collection boxes to realize the separation of tiny particles.

The invention forms plasma through gas discharge in a vacuum chamber, and the particles to be separated are negatively charged in the plasma environment and form a stable and dispersed suspension system, which provides basic conditions for realizing the separation of particles. Because the plasma is used to disperse the particles and be in a stable suspension state, the separation process is a dry process. Compared with the wet process of the existing laser particle size analyzer, this dry process can avoid the problems caused by the existing wet process. A series of problems such as cumbersome measurement process and long measurement time. At the same time, particles of different sizes will enter the collection boxes at both ends of the ratchet surface groove respectively. After the particles are separated, just take out the particle separator. This is a pollution-free separation method, which avoids the need to clean the entire The cumbersome process of installation. Since the gas in the vacuum chamber is basically static, it can overcome the shortcoming of interference to the laser light path caused by gas flow in the existing dry process, and then can achieve accurate separation of particles. In addition, the invention can also realize the separation of extremely low content of tiny particles.

The design of the ratchet curved surface groove in the particle separator makes a ratchet-shaped plasma sheath formed on the surface, and the sheath has asymmetry, and dispersed and suspended particles are bound in the plasma sheath. Turn on the semiconductor laser and the chopper, and adjust the pulse frequency of the chopper. Under the impetus of the laser, the particles of different sizes move in two directions, so as to realize the separation of the particles. The invention is simple and convenient to operate, and provides a solution for rapid separation in laboratories and industrial fields.

Description of drawings

Fig. 1 is a schematic structural view of a dry microparticle separation device in the present invention.

Fig. 2 is a schematic diagram of a three-dimensional structure of the particle separator in Fig. 1 .

In the figure: 1. Vacuum chamber, 2. Upper plate, 3. Particle pool, 4. Vibrating rod, 5. Side window, 6. Particles to be separated, 7. Lifting platform, 8. Semiconductor laser, 9. Chopper , 10, beam expander, 11, lower plate, 12, particle separator, 12-1, ratchet surface groove, 12-2, collection box, 13, vacuum gauge, 14, radio frequency power supply, 15, controller.

detailed description

The dry microparticle separation method provided by the present invention relies on a dry microparticle separation device. As shown in Figure 1, the dry microparticle separation device includes a vacuum chamber 1, which is surrounded by a stainless steel cavity. Grounding wire; two upper and lower pole plates are arranged horizontally in the vacuum chamber 1 , namely the upper pole plate 2 and the lower pole plate 11 . In this embodiment, the upper pole plate 2 is composed of two pieces of ITO conductive glass stacked together, and the lower pole plate 11 is a flat metal plate. The upper plate 2 is grounded, the lower plate 11 is connected to the power electrode of the radio frequency power supply 14 , and the other electrode of the radio frequency power supply 14 is grounded. The radio frequency power supply 14 is located outside the vacuum chamber 1 . When the lower plate 11 is connected to the power electrode of the radio frequency power supply 14, the specific connection method is: drill a hole in the center of the bottom of the lower plate 11, insert an insulating sleeve in the drilled hole, and connect a metal wire in the insulating sleeve , the lower plate 11 is electrically connected to the power electrode of the radio frequency power supply 14 outside the vacuum chamber 1 through the metal wire in the insulating sleeve. Between the power electrode of the radio frequency power source 14 and the lower plate 11, a capacitor for adjusting power matching can be arranged. After the radio frequency power supply 14 is switched on, the voltage of the radio frequency power supply 14 changes polarity continuously. After several times of charging and discharging, the lower plate 11 will finally have a negative bias voltage. A uniform plasma is generated. The frequency of the radio frequency power supply 14 can be adjusted to 13.56MHz, and the power supply can be 1~60W.

A particle separator 12 is arranged on the lower plate 11, and the particle separator 12 is made of insulating material, and its specific structure is shown in FIG. 2 . The bottom of the particle separator is a planar structure, and the upper part is a channel structure with an open top and a concave cavity. The channel structure specifically includes a ratchet curved groove 12-1 in the middle and collection boxes 12-2 at both ends. The ratchet curved surface groove 12-1 is formed by a number of concave evenly arranged ratchets adjacent to each other in turn. The cross-section of the ratchet is an inclined asymmetric structure. Or called the steep slope) and the long side after the ratchet is inclined (also called the tooth length of the ratchet, or called the gentle slope) ratio is 1:2. Both ends of each ratchet are bent upwards, and the curved surface of the ratchet curved groove 12-1 is curved at 180°, so as to bind the particles to be separated. The two collection boxes 12-2 are respectively located at the left and right ends of the ratchet curved surface groove 12-1 along the axial direction of the ratchet curved surface groove 12-1, and each collection box 12-2 passes through the concave semicircle The left and right sides of the groove are formed by setting semicircular short edges respectively. After the particle separator 12 is in the plasma environment between the upper and lower plates, a concave, ratchet-shaped plasma sheath can be formed on the surface of the ratchet curved groove 12-1, and the plasma sheath in the collection box 12-2 The bottom surface of the box forms a concave, semicircular plasma sheath.

Above the ratchet surface groove 12-1 and below the upper pole plate 2, a particle pool 3 is provided, and the particle pool 3 holds the particles 6 to be separated. The particles 6 to be separated are generally two types of micron-scale particles of different sizes. . The particle pool 3 is formed by pressing multilayer metal meshes of different meshes; the surface of the particle pool 3 is preferably in a horizontal state, and the center of the particle pool 3 is preferably on the axis of the upper and lower plates. The particle pool 3 is connected to the vertical vibrating rod 4 through a horizontal connecting rod, and the vibrating rod 4 passes out of the vacuum chamber 1 . Outside the vacuum chamber 1, the particle pool 3 can be moved up and down by moving the vibrating rod 4 up and down; outside the vacuum chamber 1, the particle pool 3 can be moved left and right by rotating the vibrating rod 4; outside the vacuum chamber 1, the vibrating rod 4 can be made to vibrate. The to-be-separated particles 6 in the particle pool 3 are scattered out of the particle pool 3, and the vibration of the vibrating rod 4 can be manually operated or electrically operated, and the frequency of the electric operation can be 1-10 Hz. The connecting rod between the particle pool 3 and the vibrating rod 4 is an insulating rod, and its material may be polytetrafluoroethylene; the insulating rod can prevent the particle pool 3 from damaging the vibrating rod 4 due to conduction in the plasma region. The to-be-separated particles 6 scattered from the particle pool 3 are negatively charged in the plasma environment, and are finally suspended in the ratchet-shaped plasma sheath above the lower plate 11 .

An air inlet and an air outlet are opened on the cavity of the vacuum chamber 1 . Air or argon can be filled into the vacuum chamber 1 through the air inlet; a vacuum gauge 13 for measuring the air pressure in the vacuum chamber 1 is installed at the gas outlet. The air pressure in the vacuum chamber 1 is generally controlled between 5-200Pa.

There are two opposite side windows 5 on the cavity of the vacuum chamber 1, and the connection line of the two side windows 5 is just on the axis of the particle separator 12, so that each side window 5 corresponds to a collection box. A semiconductor laser 8 is arranged outside the vacuum chamber 1 corresponding to each side window 5. The power range of the semiconductor laser 8 is 0.01~2W, and the center wavelength of the laser emitted by the semiconductor laser 8 is 532nm or 650nm. A chopper 9 is provided in front of each semiconductor laser 8 (that is, the side facing the side window), and a beam expander 10 is provided in front of each chopper 9 . The semiconductor laser 8 outside the side window 5, the chopper 9 and the beam expander 10 constitute a photodynamic system. The photodynamic system is arranged on the lifting platform 7, and the lifting platform 7 is connected with the stepping motor. In this embodiment, the minimum step length of the stepping motor can reach the order of microns, so the particles of the order of microns can be accurately scanned so as to better observe the particles. The stepping motor, the semiconductor laser 8 and the chopper 9 are all connected to the controller 15 (such as a computer). The controller 15 controls the pulse number and frequency of the stepping motor on the one hand to drive the lifting table 7 to move up and down, thereby realizing Adjust the heights of the semiconductor laser 8 , the chopper 9 and the beam expander 10 so that the laser light emitted by the semiconductor laser 8 can be irradiated into the ratchet concave groove in the vacuum chamber 1 . On the other hand, the controller 15 also controls the irradiation time of the semiconductor laser 8 and the pulse frequency of the chopper 9 . The setting should ensure that the laser light emitted by the two semiconductor lasers 8 is on the same straight line, and the light intensity of the laser light emitted by the two semiconductor lasers 8 is equal.

The chopper 9 is located in front of the semiconductor laser 8, and its function is to adjust the pulse frequency of the laser light emitted by the semiconductor laser 8; the beam expander 10 is used to expand the beam of the laser light emitted by the semiconductor laser 8, so that the laser can irradiate the ratchet curved surface All suspended particles to be separated in the tank. Under the irradiation of laser light, coupled with the effect of the ratchet-shaped plasma sheath formed by the ratchet surface groove in the plasma environment, by adjusting the pulse frequency of the chopper 9 (that is, to realize the adjustment of the laser pulse frequency), select An appropriate frequency of the chopper can make two kinds of particles of different sizes among the particles to be separated 6 move in opposite directions along the axis of the ratchet surface groove, so as to achieve the purpose of separation. Due to the different natural frequencies of particles of different sizes, each ratchet in the groove of the ratchet surface has asymmetry, that is, the slopes on both sides of the ratchet are different; for large-sized particles, the natural frequency is low and the period is long, and the position is relatively low. It is easier to pass through the gentle slope, so the large-sized particles move toward the side of the gentle slope; for the small-sized particles, their natural frequency is higher, the period is shorter, and the position is higher, so it is easier to pass through the steep slope, so the small-sized particles are oriented toward the side of the steep slope move. And the particles with small size move relatively fast, and the particles with large size move relatively slowly. As the particle moves into the plasma sheath above the collection box, the particle will no longer move due to the loss of the ratchet plasma sheath. After the large-size particles and small-size particles enter the plasma sheath above the two collection boxes, turn off the radio frequency power supply so that no plasma is generated between the upper and lower plates, that is, the plasma above the collection box The sheath disappears, and the large-size particles and small-size particles will fall freely at this time, and then the two collection boxes collect the particles of two different sizes respectively.

The process of separating micron-scale particles of two different sizes in the present invention will be described below with a specific example.

a. Set a vacuum chamber 1, the vacuum chamber 1 is surrounded by a stainless steel cavity, and the stainless steel cavity is grounded; adjust the air pressure in the vacuum chamber 1 to 10Pa. In the vacuum chamber 1, two upper and lower pole plates are horizontally arranged; the upper pole plate 2 is grounded, the lower pole plate 11 is connected to the power electrode of a radio frequency power supply 14, and the other electrode of the radio frequency power supply 14 is grounded. The length of the lower pole plate 11 is 100mm.

b. A particle separator 12 is arranged on the lower plate 11, and the length of the particle separator 12 is 100 mm. The particle separator 12 is made of insulating material, and its specific structure is shown in FIG. 2 . In this embodiment, the particle separator 12 is made of glass, the bottom of which is a plane structure, and the upper part is a channel structure with an open top and a concave channel. The channel structure specifically includes a ratchet curved groove 12-1 in the middle and two end of the collection box 12-2. The curved surface of the ratchet curved groove has a curvature of 180 degrees, the number of ratchets in the ratchet curved groove is 18, the tooth depth of each ratchet is 3mm, and the tooth length is 6mm. The collection box 12-2 is formed by setting semicircular short edges on the left and right sides of the concave semicircular groove respectively.

c. A particle pool 3 is set above the ratchet curved surface groove, and two different sizes of micron-scale particles 6 to be separated are contained in the particle pool 3; in this embodiment, the particles 6 to be separated include two different sizes particles, one of which has a particle size of 23 μm and the other has a particle size of 10 μm (in addition, the inventors have also separated particles of two sizes of 23 μm and 3 μm). The particle pool 3 is formed by pressing multi-layer metal meshes of different meshes; the particle pool 3 is connected to the vertical vibrating rod 4 through a horizontal insulating rod, and the vibrating rod 4 passes out of the vacuum chamber 1 .

d, two opposite semiconductor lasers 8 are arranged outside the vacuum chamber 1, and each semiconductor laser 8 corresponds to a collection box in the particle separator 12; a chopper 9 is respectively arranged in front of each semiconductor laser 8 , a beam expander 10 is respectively arranged in front of each chopper 9 .

There are two opposite side windows 5 (the side windows 5 are made of quartz glass) on the cavity of the vacuum chamber 1, and the connecting line of the two side windows 5 is just on the axis of the particle separator 12, so that Each side window 5 corresponds to a collection box. The connection line of the two semiconductor lasers 8 coincides with the axis of the particle separator 12 by setting. The semiconductor laser 8, the chopper 9 and the beam expander 10 are arranged on the lifting platform 7, and the lifting platform 7 is connected with the stepping motor. The stepping motor, semiconductor laser 8 and chopper 9 are all connected to the controller 15. The controller 15 is used to control the stepping motor on the one hand to drive the lifting platform 7 to move up and down, and then realize the adjustment of the semiconductor laser 8, chopper The height of the device 9 and the beam expander 10; on the other hand, it is used to control the irradiation time of the semiconductor laser 8 and the pulse frequency of the chopper 9.

e. Turn on the radio frequency power supply 14, set the frequency of the radio frequency power supply 14 to 13.56MHz, and the power to 20W, so that the lower plate 11 has a negative bias voltage, and generate uniform plasma between the upper and lower plates through high frequency discharge.

f. Electrically operate the vibrating rod 4 outside the vacuum chamber 1 so that the particle pool 3 is at the center of the upper and lower plates. Make the vibration rod 4 vibrate, and then drive the particle pool 3 in the vacuum chamber 1 to vibrate, so that the particles 6 to be separated in the particle pool 3 are scattered from the particle pool 3; after the particles are sprinkled, turn the vibration rod 4 to remove the particle pool 3 plasma region.

The scattered particles 6 to be separated enter the plasma region, and the negatively charged electrons and positively charged ions in the plasma will accumulate on the particles 6 to be separated. Since the moving speed of the electrons is much greater than that of the ions, when the accumulated When the electron flow and ion flow on the particle 6 to be separated reach equilibrium, the particle will generally carry a certain amount of negative charge. Particles in the plasma region will move downward due to the action of gravity; when the particles to be separated 6 fall near the groove of the ratchet surface, since the lower plate 11 has a negative potential, the particles will be subjected to an upward electrostatic field force. When the gravitational force and electrostatic field force on the particles are balanced, the particles will be suspended and bound in the curved ratchet-shaped glass trough. At the same time, since the particles all carry negative charges, they will repel each other and thus disperse to form a good dispersion suspension system.

g. Turn on the semiconductor laser 8 and the chopper 9, set the power of the semiconductor laser 8 to 50 mW, and the center wavelength of the laser light emitted by the semiconductor laser 8 to be 532 nm. It is ensured that the laser light emitted by the two semiconductor lasers 8 is on the same straight line, and the light intensity of the laser light emitted by the two semiconductor lasers 8 is equal. The laser beam emitted by the semiconductor laser 8 is expanded by the beam expander 10 to form a laser beam. By adjusting the horizontal position of the beam expander 10 , the laser beam formed by the laser passing through the beam expander 10 can cover the width range of the groove on the ratchet curved surface. Control the pulse number and frequency of the stepping motor, adjust the height of the lifting platform 7, so that the horizontal plane laser beam can irradiate the suspended particles in the groove of the ratchet curved surface in the vacuum chamber 1.

h. Adjust the pulse frequency of the chopper 9 so that the particles of two different sizes in the particles to be separated move in two opposite directions along the axis of the ratchet surface groove, so as to separate the particles of different sizes the goal of.

i. When the particles of two different sizes reach the top of the two collection boxes respectively, the radio frequency power supply 14 is disconnected, and the particles freely fall into the corresponding collection boxes, thereby realizing the separation of the particles of two different sizes.

When the invention is used to separate particles of two different sizes, the operation is simple, fast, and pollution-free, and the separation of tiny particles of different sizes in the micron range is well realized.

Claims (10)

1. A dry microparticle separation method is characterized in that it comprises the steps of: a. A vacuum chamber is set, and two upper and lower pole plates are horizontally arranged in the vacuum chamber; the upper pole plate is grounded, the lower pole plate is connected to a power electrode of a radio frequency power supply, and the other electrode of the radio frequency power supply is grounded Wire; b. A particle separator is arranged on the lower plate, and the particle separator includes a ratchet curved surface groove formed by successively adjacent concave ratchet teeth in the middle part and collection boxes at both ends; c. A particle pool is set above the ratchet surface groove, and two different sizes of micron-scale particles to be separated are contained in the particle pool; the particle pool and the vibrating rod passing through the vacuum chamber connected; d. Two opposite semiconductor lasers are arranged outside the vacuum chamber, and each semiconductor laser corresponds to a collection box in the particle separator; a chopper is respectively arranged in front of each semiconductor laser, and A beam expander mirror is arranged in front of each chopper; e. Turn on the radio frequency power supply, and generate uniform plasma between the upper plate and the lower plate through gas discharge; f. Make the vibrating rod vibrate outside the vacuum chamber, and then drive the particle pool in the vacuum chamber to vibrate, so that the particles to be separated in the particle pool are scattered from the particle pool; the scattered particles are in the plasma region Negatively charged, and form a stable and dispersed suspension system in the ratchet curved groove near the top of the lower plate; g. Turn on the switch of the semiconductor laser and the chopper, so that the laser light emitted by the semiconductor laser is irradiated on the suspended particles in the vacuum chamber; h. Adjust the pulse frequency of the chopper so that the particles of two different sizes in the particles to be separated move in two opposite directions along the axis of the ratchet surface groove; i. When the particles of two different sizes reach the top of the two collection boxes respectively, the radio frequency power supply is disconnected, and the particles freely fall into the corresponding collection boxes, thereby realizing the separation of the two different sizes of particles. 2. The dry microparticle separation method according to claim 1, characterized in that, in the step e, the frequency of the radio frequency power supply is adjusted to 13.56MHz, and the power is 1~60W. 3. The dry micro particle separation method according to claim 1, characterized in that, the semiconductor laser, the chopper and the beam expander are all arranged on a lifting platform, and the lifting platform and the stepping The motor is connected. 4. The dry microparticle separation method according to claim 3, characterized in that, the stepper motor, the semiconductor laser and the chopper are all connected to a controller, and the controller uses To control the work of the stepping motor, to drive the lifting platform to move up and down, and then realize the adjustment of the height of the semiconductor laser, the chopper and the beam expander; on the other hand, it is used to control the irradiation of the semiconductor laser time as well as the pulse frequency of the chopper. 5. The dry microparticle separation method according to claim 1, wherein in step g, the center wavelength of the laser light emitted by the semiconductor laser is 532nm or 650nm, and the power range of the semiconductor laser is 0.01~2W. 6 . The dry microparticle separation method according to claim 1 , wherein the curvature of the ratchet curved groove is 180°. 7 . 7. The dry micro particle separation method according to claim 6, characterized in that, the collection box is formed by setting semicircular short edges on both sides of the concave semicircular groove. 8 . The dry microparticle separation method according to claim 1 , wherein the ratio of tooth depth to tooth length of the ratchet is 1:2. 9. The dry microparticle separation method according to claim 1, characterized in that, the vacuum chamber is surrounded by a stainless steel cavity, and the stainless steel cavity is grounded; the side wall of the stainless steel cavity is provided with Two opposite side windows, each of which corresponds to a semiconductor laser; in step g, the laser light emitted by the semiconductor laser is irradiated onto the suspended particles in the vacuum chamber through the corresponding side windows. 10. The dry micro particle separation method according to claim 1, characterized in that, the particle pool is formed by pressing multilayer metal meshes of different meshes; the vibrating rod is vertically arranged, and the particle pool The vibration rod is connected to the vibration rod by a horizontally arranged insulating rod.