Solid-liquid particle suspension device and method based on branched quadrupole electrodynamic balancer

Abstract

The application relates to a solid-liquid particle suspension device and method based on a branched quadrupole electrodynamics balancer, which comprises a branched quadrupole mechanism, a quadrupole main body arranged in a vertical direction, and a quadrupole branch in an inclined connection with the quadrupole main body; an adjustable laser emission mechanism at the top of the branched quadrupole mechanism, configured to generate a laser beam and introduced into the center of the branched quadrupole mechanism; a direct current balance plate at the bottom of the branched quadrupole mechanism; a particle sample introduction mechanism at the top of the quadrupole branch, configured to generate liquid droplets or solid particles to be observed; and a sealed cavity. Compared with the prior art, the application separates the paths of laser observation, particle sample introduction and charge application in space by using a branched structure, realizes independent capture, parallel operation and optical characterization of multiple particles.

Description

Technical Field

[0001] This invention belongs to the field of solid-liquid particle suspension technology, and relates to a solid-liquid particle suspension device and method based on a branched quadrupole electrodynamic balancer. Background Technology

[0002] Single-particle suspension technology refers to the use of non-contact potential wells such as light, sound, and electricity to "isolate" and stably suspend micro- and nano-particles (10 nm to 100 μm) from the environment, thereby achieving low-disturbance particle property characterization at the single-particle level. Electrodynamic balance (EDB) achieves stable single-particle suspension through the synergistic action of AC and DC electrodes. Existing electrodynamic balancers mainly include: (1) Double-ring electrodynamic balance. The double-ring electrodynamic balance combines an alternating electric field generated by a ring electrode with an electrostatic field, achieving stable suspension of particles in space while maintaining good optical accessibility. In the prior art, the double-ring electrodynamic balance usually generates an electrostatic force to balance the particle's gravity and aerodynamic drag by applying an AC voltage and superimposing a DC bias voltage on the ring electrode, thereby achieving non-contact suspension of single or multiple particles. When the device is placed in an experimental environment with controllable temperature and humidity, it can be used to simulate the physicochemical behavior of aerosol particles under atmospheric conditions and has been widely used in the study of particle hygroscopic characteristics, reaction processes and related properties. However, the stability of particles in the double-ring electrodynamic balance is poor, and the spatial distribution of particles in the electric field is difficult to control precisely when multiple single particles are suspended simultaneously.

[0003] (2) Linear Quadrupole Electrodynamic Balance (LQ-EDB). The linear quadrupole electrodynamic balance is a linearized electrodynamic suspension structure derived from the three-dimensional Paul ion trap. Its electrode configuration and working principle are inspired by the design of quadrupole mass filters in mass spectrometry, and optimized for the suspension requirements of aerosol particles under normal pressure conditions. In existing technologies, this type of device typically consists of four linear electrodes. By applying alternating voltage to the electrodes to generate a quadrupole electric field, the charged particles are stably suspended in the radial direction. Simultaneously, due to the damping effect of gas molecules, the particles are highly confined near the electrode axis in the electric field and can move freely in the axial direction, thus forming a radially confined and axially controllable suspension state. To maintain the stable position of the particles in the axial direction, existing LQ-EDB devices typically combine additional electrostatic forces to balance the gravity and aerodynamic drag on the particles, allowing the particles to remain stably suspended even when gas flow is introduced to regulate the experimental environment. Based on the above working mechanism, the linear quadrupole electrodynamic balancer has been used for non-contact suspension of single or multiple particles, and combined with optical or spectroscopic analysis methods to study the physicochemical properties of particles.

[0004] (3) Branched Quadrupole Electrodynamic Balance (BQ-EDB). This type of device, through branching or extending the quadrupole electrode structure, introduces multiple relatively independent operating channels and suspension regions while maintaining the radial constraint mechanism of the quadrupole electric field on charged particles, thereby achieving spatial separation between the droplet injection path and the laser incident path. This type of structure has the potential to expand the application of electrodynamic suspension technology in the study of multi-particle systems and complex processes, but its structural complexity also places higher demands on electric field uniformity, particle stability, and multi-channel coordinated control.

[0005] Overall, among the various electrodynamic balancers mentioned above, the BQ-EDB possesses the most complex and powerful functionality. In current research, this type of EDB is primarily used for the manipulation and analysis of liquid microdroplets (microdroplets). Droplet samples can be generated on demand and stably using a mature piezoelectric droplet generator, which then captures and maintains long-term stable suspension by the electrodynamic balancer. Based on this, and combined with the control of temperature, humidity, and reaction environment parameters, related technologies have been applied in the study of droplet evaporation behavior and reaction kinetics.

[0006] Existing electrodynamic balancers are mainly built around liquid microdroplet systems, each with several shortcomings. First, while traditional dual-ring electrodynamic balancers possess three-dimensional adjustment capabilities, their suspended particle stability is poor. During multi-particle injection, particles easily aggregate and overlap within the potential well, making independent spatial arrangement impossible to control, which fundamentally contradicts the requirement for independent multi-channel control. Second, linear quadrupole electrodynamic balancers often employ dry powder blowing injection when manipulating solid particles at atmospheric pressure, easily causing particle aggregation at the nozzle, significantly reducing effective charge and capture success rate. Furthermore, in traditional linear structures, the injection path is coaxial with the laser path, lacking spatial separation and parallel operation capabilities; its design philosophy is incompatible with the parallel suspension and multi-channel control emphasized by branched structures. Finally, although branched quadrupole electrodynamic balancers are the preferred architecture for achieving multi-channel control, their existing structural parameters, voltage distribution, and simulation analyses are all optimized based on the dynamic behavior of spherical droplets. For solid particles with irregular morphology and varying dielectric properties, their trajectory in the bifurcation node region is greatly affected by dipole moment orientation and local electric field leakage, and there is currently a lack of corresponding theoretical and experimental support. No mature schemes with good reproducibility for achieving stable suspension of solid particles within this structure have been found in the published literature. Therefore, stable capture and manipulation of solid particles in branched architectures remains a technological gap. Summary of the Invention

[0007] The purpose of this invention is to provide a solid-liquid particle suspension device and method based on a branched quadrupole electrodynamic balancer, providing a universal containerless platform compatible with solid-liquid two-phase particles for in-situ characterization of air-suspended particles.

[0008] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a solid-liquid particle suspension device based on a branched quadrupole electrodynamic balancer, comprising: A branch-type quadrupole mechanism includes a quadrupole body arranged vertically and a quadrupole branch connected at an inclination to the quadrupole body. The top of the quadrupole body is provided with a first laser incident interface, and the quadrupole branch has an independent feeding channel. The adjustable laser emitting mechanism located at the top of the branched quadrupole mechanism is configured to generate a laser beam and introduce it into the center of the branched quadrupole mechanism via the first laser incident interface. The DC balance plate located at the bottom of the branched quadrupole mechanism includes a conductive plate and an insulating fixing plate that can fix the bottom of the quadrupole body. The conductive plate has a cross-shaped structure, with connection holes for connecting DC voltage at the ends and a central opening as a droplet drop hole. The insulating fixing plate is connected to the conductive plate, so that the conductive plate and the branched quadrupole mechanism are mutually insulated. The particle injection mechanism located at the top of the quadrupole branch is configured to generate droplets or solid particles to be observed. The system includes sealed chambers, comprising an upper chamber surrounding the upper part of the quadrupole body, a lower chamber surrounding the lower part of the quadrupole body, and side chambers surrounding the quadrupole branches. The upper chamber communicates with the lower chamber and the side chambers, respectively. Furthermore, both the quadrupole body and the quadrupole branches contain four poles, which are fixed with ceramic rings to ensure insulation between adjacent poles. Two diagonally opposite poles are connected by a conductive bridge and form a potential well by applying a unidirectional alternating current.

[0009] Furthermore, the particle injection mechanism includes a particle injector, a metal clip, and a particle charging unit. The particle injector is used to form droplets or solid particles, the metal clip is used to fix the particle injector, and the particle charging unit is used to apply high voltage and cause the droplets or solid particles to carry a charge opposite to or the same as that of the particle charging unit.

[0010] Furthermore, the metal clip is also grounded.

[0011] Furthermore, an upper chamber connecting plate and an upper chamber cover are sequentially arranged on the top of the upper chamber. The side panel of the upper chamber is also provided with several first BNC wire connection holes, each hole having a clearly defined function. For example, the first hole is connected to the positive terminal of the AC power supply, the second hole is connected to the negative terminal of the AC power supply, and the third hole is dedicated to connecting to the induction electrode on the side cavity. The lower chamber is also provided with several circular optical windows on its side for observing the suspension state of particles. The lower chamber is also provided with a second BNC wire connection hole on its side, and the top is connected to the upper chamber through a connecting screw hole. The side chamber is connected to the particle injection mechanism via a connecting plate.

[0012] Furthermore, the top of the upper chamber is also provided with an inlet for introducing reactive gas or a dry-wet mixed nitrogen gas. The lower chamber is also provided with a probe insertion hole on its side, which can be used to insert a humidity monitoring probe and monitor the relative humidity inside the sealed chamber. Furthermore, the adjustable laser emitting mechanism includes a laser generator, two plane mirrors, and a mounting bracket. The left-right deflection and up-down pitch angles of the two plane mirrors are adjustable to direct the laser beam generated by the laser generator into the mounting bracket at a preset horizontal height. One side surface of the mounting and adjusting frame is provided with a second laser incident interface for docking with the laser beam generated by the laser generator. Inside the mounting and adjusting frame, there is also an adjustable reflector mounting base with a reflective lens. The bottom of the mounting and adjusting frame is provided with an optical window. The laser beam introduced through the second laser incident interface is reflected by the reflective lens and output from the optical window at a preset angle, and then enters the branched quadrupole mechanism through the first laser incident interface.

[0013] Furthermore, the angle between the quadrupole branch and the quadrupole body is 60°.

[0014] In a second aspect, the present invention provides a solid-liquid particle suspension method based on a branched quadrupole electrodynamic balancer, which is implemented based on the solid-liquid particle suspension device described in the first aspect above. The solid-liquid particle suspension method includes the following steps: S1. Adjust the laser incident direction of the adjustable laser emitting mechanism to ensure that the laser beam can pass through the middle cavity of the branched quadrupole mechanism and be focused on the preset particle suspension area. S2. Apply an AC voltage of predetermined frequency and amplitude to the poles of the branched quadrupole mechanism, and at the same time apply an initial DC voltage to the DC balance plate to construct a composite electric field environment that meets the requirements for particle suspension. S3. Droplets or solid particles are generated by the particle injection mechanism and introduced into the preset particle suspension area in S1. S4. Real-time observation of the motion and falling of droplets or solid particles in the intermediate cavity of the branched quadrupole mechanism.

[0015] Furthermore, in S4, based on the feedback observation results, the voltage value of the DC balance plate is adjusted until the solid-liquid particles can remain stably suspended above the DC balance plate and are within the preset target height range. The adjustment of the DC voltage value satisfies the following conditions: (a) The DC voltage value changes continuously or in steps during the adjustment process, and the direction and amplitude of the change are determined in real time according to the displacement deviation of the particles in the vertical direction; (b) The adjusted voltage value should balance the resultant force of electrostatic force, gravity and fluid resistance on the particles in the vertical direction; (c) The target height range is within the depth of field and field of view of the side optical window to ensure that the solid-liquid particles can be clearly observed and facilitate subsequent optical characterization operations.

[0016] The innovative aspects of the solid-liquid particle suspension device of this invention are described below: (a) Cross-shaped DC balance plate: DC balance board (e.g.) Figure 6The main body (as shown) is designed as a cross-shaped conductive structure with a central through-hole (e.g., 2 mm) serving as a channel for the suspended droplets to fall. Mounting holes are located at the four ends of the cross-shaped conductive structure. These mounting holes have a dual function: firstly, they are used to connect a DC high-voltage power supply, typically applying a DC voltage with the same polarity as the net charge of the particles to be suspended, generating an upward electrostatic force to balance the particle's gravity and aerodynamic force, achieving axial suspension; when particle detachment is required, a reverse voltage is applied. Secondly, the mounting holes are used to securely mount the entire cross-shaped voltage plate to the insulating base at the bottom using mechanical connectors (such as insulating screws). This fixing method not only ensures that the voltage plate does not shift during the experiment but also guarantees a high degree of repeatability and consistency in the spatial distribution and intensity of the electric field generated by this electrode structure in each suspension experiment, thus providing a reliable electric field environment for subsequent precision measurements or operations.

[0017] (b) "Tip-high voltage pulse charging" injection method for solid particles: This device employs a "tip-based high-voltage pulse charging" method for introducing solid particles, distinct from the "inductive charging" method used for liquid droplets. Specifically, an insulated micro-sampling tool (such as a sleeve-type conductive needle) is used to collect a trace amount of solid particle sample. A momentary high-voltage pulse is then applied to the metal tip of this tool. The high-voltage pulse generates a strong electric field at the tip, causing the solid particles attached to the tip to carry a net charge of the same polarity as the pulse voltage through corona discharge or field emission. The charged solid particles are then directly released and introduced into the established levitation electric field region under the influence of gravity and the electric field. This method achieves precise and controllable charging of solid particles, allowing them to be immediately captured by the levitation electric field after charging. It effectively avoids the drawbacks of traditional powder spraying or dispersion methods, such as the irregular diffusion and scattering of particles, which contaminate the internal optical windows and other clean areas of the device. This significantly improves the reliability, success rate, and cleanliness of the experimental environment for solid particle levitation.

[0018] (c) Can switch between different working modes In addition to its basic operating mode, where the laser is incident vertically downwards from above the device while solid or liquid particle samples are introduced through lateral branch channels for observation, the device can switch to other operating modes. For example, by adjusting the optical path, the laser can be incident vertically upwards from below the device. In this mode, particles can be introduced simultaneously through the top main channel and the side branch channels, allowing particles from both sources to converge in the central region of the quadrupole electric field trap, thus enabling controlled particle collision experiments. This feature expands the device's application range, enabling it to be used to study the interactions, coagulation, and kinetic reaction processes between particles of different phases.

[0019] Compared with existing technologies, this invention utilizes a branched quadrupole mechanism to separate the laser observation, particle sample introduction, and charge application path space, thereby enabling independent capture, parallel manipulation, and optical characterization of multiple particles. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the solid-liquid particle suspension device of the present invention during droplet suspension; Figure 2 This is a schematic diagram of the solid-liquid particle suspension device of the present invention during solid particle suspension. Figure 3 This is a schematic diagram of a solid-liquid particle suspension device. Figure 4 A flowchart of a solid-liquid particle suspension method; Figure 5 This is a real-life image of droplets and solid particles suspended in the air; Figure 6 This is a schematic diagram of the DC balance plate. Figure 7 This is a partial optical path diagram of an adjustable laser emitting mechanism; Figure 8 This is a partial structural diagram of an adjustable laser emission mechanism. Explanation of markings in the diagram: 1-Branch-type quadrupole mechanism, 11-Quadrupole body, 12-Quadrupole branch, 13-Ceramic ring, 14-Conductive connecting bridge; 2-DC balance plate, 21-conductive plate, 22-insulating fixing plate; 3-Adjustable laser emitting mechanism, 31-Mounting and adjusting bracket, 32-Reflecting mirror, 33-Laser generator, 34-Plane mirror, 35-Optical window. 4-Particle injection mechanism, 41-Particle injector, 42-Metal buckle, 43-Particle charging unit; 5-Sealed chamber, 51-Upper chamber, 52-Lower chamber, 53-Side chamber, 54-First BNC wire connection hole, 55-Circular optical window, 56-Second BNC wire connection hole, 57-Upper chamber connection plate, 58-Upper chamber cover, 59-Probe insertion hole. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0022] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] Unless otherwise specified, the functional components or structures in the following embodiments or examples are conventional components or structures used in the art to achieve the corresponding functions.

[0025] To provide a universal containerless platform compatible with solid-liquid two-phase particles for in-situ characterization of airborne particles, this invention provides a solid-liquid particle suspension device based on a branched quadrupole electrodynamic balancer. Please refer to [link to relevant documentation]. Figures 1 to 3 As shown, it includes: A branched quadrupole mechanism includes a vertically oriented quadrupole body and a quadrupole branch inclinedly connected to the quadrupole body. The top of the quadrupole body is provided with a first laser incident interface, and the quadrupole branch has an independent feed channel. Furthermore, the quadrupole body and the quadrupole branch can be welded together first and then fixed using V-shaped connecting plates. In this invention, the quadrupole branch is dedicated to sample introduction, using an alternating current electric field to efficiently introduce charged liquid or solid samples into the system. The quadrupole body introduces laser light through the first laser incident interface at the top and generates a balanced electric field with the help of a DC balance plate at the bottom, interacting with the sample introduced by the quadrupole branch to ensure that the droplet remains stable in the central region of the quadrupole, thus providing conditions for subsequent analysis. An adjustable laser emitting mechanism located at the top of the branched quadrupole mechanism is configured to generate a laser beam and introduce it into the center of the branched quadrupole mechanism; The DC balance plate located at the bottom of the branched quadrupole mechanism includes a conductive plate and an insulating fixing plate that can fix the bottom of the quadrupole body. The conductive plate has a cross-shaped structure, with connection holes for connecting DC voltage at the ends and a central opening as a droplet drop hole. The insulating fixing plate is connected to the conductive plate, so that the conductive plate and the branched quadrupole mechanism are mutually insulated. The particle injection mechanism located at the top of the quadrupole branch is configured to generate droplets or solid particles to be observed. The system includes a sealed chamber, comprising an upper chamber surrounding the upper part of the quadrupole body, a lower chamber surrounding the lower part of the quadrupole body, and a side chamber surrounding the quadrupole branch. The upper chamber is connected to the lower chamber and the side chamber, respectively.

[0026] In some specific embodiments, both the quadrupole body and the quadrupole branches contain four poles, which are fixed with ceramic rings to ensure insulation between adjacent poles. Two diagonally opposite poles are connected by a conductive bridge, and a potential well is formed by applying a unidirectional alternating current, allowing the particle to remain horizontally stable at the center of the four poles. Here, the alternating current frequency is 1-2 kHz, and the voltage amplitude is 400-1200V. The diagonal pole spacing between the quadrupole body and the quadrupole branches can be set to 11.34 mm, the total length of the quadrupole body is 100 mm, and the length of the quadrupole branches is approximately 45 mm.

[0027] In some specific embodiments, the particle injection mechanism includes a particle injector, a metal clip, and a particle charging unit. The particle injector is used to form droplets or solid particles, the metal clip is used to fix the particle injector, and the particle charging unit is used to apply high voltage and cause the droplets or solid particles to carry a charge opposite to or the same as that of the particle charging unit. Here, the configuration of the particle injection mechanism varies depending on whether the formed particles are droplets or solid particles. For example, for droplets, the particle injector can be a nozzle capable of generating droplets, with an orifice diameter of 32-50 μm. After passing through a particle charging unit (which can be an inductive electrode) with applied high voltage, the droplet carries a static charge opposite to that of the inductive electrode. The droplet with a net charge can be suspended above it by a DC balance plate with the same voltage. For solid particles, the particle injector can be a needle capable of picking up solid particles. By applying a high-voltage pulse to the other end of the needle (the corresponding particle charging unit is the other end of the needle that picks up the particles), solid particles with the same charge as the high-voltage pulse are generated. Similarly, the charged solid particles can also be suspended above them by a DC balance plate with the same voltage. It should be noted that switching from liquid to solid requires removing the piezoelectric nozzle and inserting a solid injection needle.

[0028] In some specific embodiments, the metal clip is also grounded.

[0029] In some specific embodiments, the top of the upper chamber is sequentially provided with an upper chamber connecting plate and an upper chamber cover. The side panel of the upper chamber is also provided with several first BNC wire connection holes, each hole having a clearly defined function. For example, the first hole is connected to the positive terminal of the AC power supply, the second hole is connected to the negative terminal of the AC power supply, and the third hole is dedicated to connecting to the sensing electrode on the side cavity. The side of the lower chamber is also provided with several circular optical windows for observing the suspension state of the particles. The side of the lower chamber is also provided with second BNC wire connection holes, and its top is connected to the upper chamber through connecting screw holes. The side chamber is connected to the particle injection mechanism through a connecting plate.

[0030] In some specific embodiments, the top of the upper chamber is also provided with an inlet for introducing reactive gas or a dry-wet mixed nitrogen gas; The lower chamber is also provided with a probe insertion hole on its side, which can be used to insert a humidity monitoring probe and monitor the relative humidity inside the sealed chamber. In some specific embodiments, the adjustable laser emitting mechanism includes a laser generator, two plane mirrors and a mounting and adjustment frame. The left and right deflection and up and down pitch angles of the two plane mirrors are adjustable so that the laser beam generated by the laser generator is incident on the mounting and adjustment frame at a preset height in a horizontal orientation. One side surface of the mounting and adjusting frame is provided with a second laser incident interface for docking with the laser beam generated by the laser generator. Inside the mounting and adjusting frame, there is also an adjustable reflector mounting base with a reflective lens. The bottom of the mounting and adjusting frame is provided with an optical window. The laser beam introduced through the second laser incident interface is reflected by the reflective lens and output from the optical window at a preset angle, and then enters the branched quadrupole mechanism through the first laser incident interface.

[0031] It should be noted here that the plane mirror can achieve deflection and pitch angle adjustment through an independent conventional mechanical structure. This invention does not require the specific structure of the mechanical structure used for adjustment, and will not be elaborated here.

[0032] In addition, the reflector mount, like a plane mirror, has independent and precise two-dimensional adjustment capability for tilt angles in two orthogonal directions (such as pitch and yaw), which can ultimately achieve precise control and calibration of the laser emission direction. Its specific structure is a conventional setup in this field and will not be elaborated here.

[0033] In some specific implementations, the angle between the quadrupole branch and the quadrupole body is 60°.

[0034] Each of the above implementation methods can be implemented individually, or in any combination of two or more without violating logic.

[0035] The above implementation methods will be described in more detail below with reference to specific embodiments.

[0036] Example 1: To provide a universal containerless platform compatible with solid-liquid two-phase particles for in-situ characterization of airborne particles, this invention provides a solid-liquid particle suspension device based on a branched quadrupole electrodynamic balancer. Please refer to [link to relevant documentation]. Figures 1 to 3 As shown, it includes: A branch-type quadrupole mechanism includes a quadrupole body arranged vertically and a quadrupole branch connected at an inclination to the quadrupole body. The top of the quadrupole body is provided with a first laser incident interface, and the quadrupole branch has an independent feeding channel. The adjustable laser emitting mechanism located at the top of the branched quadrupole mechanism is configured to generate a laser beam and introduce it into the center of the branched quadrupole mechanism via the first laser incident interface. The DC balance plate located at the bottom of the branched quadrupole mechanism includes a conductive plate and an insulating fixing plate that can fix the bottom of the quadrupole body. The conductive plate has a cross-shaped structure, with connection holes for connecting DC voltage at the ends and a central opening as a droplet drop hole. The insulating fixing plate is connected to the conductive plate, so that the conductive plate and the branched quadrupole mechanism are mutually insulated. The particle injection mechanism located at the top of the quadrupole branch is configured to generate droplets or solid particles to be observed. The system includes a sealed chamber, comprising an upper chamber surrounding the upper part of the quadrupole body, a lower chamber surrounding the lower part of the quadrupole body, and a side chamber surrounding the quadrupole branch. The upper chamber is connected to the lower chamber and the side chamber, respectively.

[0037] Please see again. Figures 1 to 3 As shown, both the quadrupole body and the quadrupole branches contain four poles, which are fixed with ceramic rings to ensure insulation between adjacent poles. Two diagonally opposite poles are connected by a conductive bridge, and a potential well is formed by applying a unidirectional alternating current, allowing the particle to remain horizontally stable at the center of the four poles. Here, the alternating current frequency is 1-2 kHz, and the voltage amplitude is 400-1200V. The diagonal pole spacing between the quadrupole body and the quadrupole branches can be set to 11.34 mm. The total length of the quadrupole body is 100 mm, and the length of the quadrupole branches is approximately 45 mm.

[0038] Please see again. Figure 1 and Figure 2As shown, the particle injection mechanism includes a particle injector, a metal clip, and a particle charging unit. The particle injector is used to form droplets or solid particles, the metal clip is used to fix the particle injector, and the particle charging unit is used to apply high voltage and cause the droplets or solid particles to carry a charge opposite to or the same as that of the particle charging unit. Furthermore, the configuration of the particle injection mechanism varies depending on whether the formed particles are droplets or solid particles. For example, for droplets, the particle injector can be a nozzle capable of generating droplets, with an orifice diameter of 32-50 μm. After passing through a particle charging unit (which can be an induction electrode) with applied high voltage, the droplet carries a static charge opposite to that of the induction electrode. The droplet with a net charge can be suspended above a DC balance plate with the same voltage. For solid particles, the particle injector can be a sampling needle capable of picking up solid particles. By applying a high-voltage pulse current to the other end of the sampling needle (the corresponding particle charging unit is the other end of the needle that picks up the particles), solid particles with the same charge as the high-voltage current are generated. Similarly, the charged solid particles can also be suspended above a DC balance plate with the same voltage. Furthermore, the metal clip is grounded.

[0039] Please see again. Figures 1 to 3 As shown, the top of the upper chamber is sequentially provided with an upper chamber connecting plate and an upper chamber cover. The side panel of the upper chamber is also provided with several first BNC wire connection holes, each hole having a clearly defined function. For example, the first hole is connected to the positive terminal of the AC power supply, the second hole is connected to the negative terminal of the AC power supply, and the third hole is dedicated to connecting to the sensing electrode on the side cavity. The side of the lower chamber is also provided with several circular optical windows for observing the suspension state of the particles. The side of the lower chamber is also provided with second BNC wire connection holes, and its top is connected to the upper chamber through connecting screw holes. The side chamber is connected to the particle injection mechanism through a connecting plate.

[0040] The top of the upper chamber is also provided with an inlet for introducing reactive gas or a dry-wet mixed nitrogen gas, which, together with the sealed chamber, can achieve the required observation environment; The lower chamber is also provided with a probe socket on its side, which can be used to insert a humidity monitoring probe and monitor the relative humidity in the sealed chamber. The probe socket can be made of rubber material commonly used in the field. It is sealed under normal conditions. The humidity monitoring probe can be squeezed into the socket structure and kept sealed with the help of the rubber material.

[0041] Furthermore, two sides of the upper chamber can be designed as transparent panels, which not only facilitates observation of the interior but also allows for easy disassembly for installation work such as connecting internal wiring. Additionally, the adjustable laser emitting mechanism includes a laser generator, two plane mirrors, and a mounting bracket. The left-right deflection and up-down pitch angles of the two plane mirrors are adjustable to direct the laser beam generated by the laser generator into the mounting bracket at a preset horizontal height. One side surface of the mounting bracket is provided with a second laser incident interface for connecting to the laser beam generated by the laser generator. Inside the mounting bracket is an adjustable reflector mounting base with a reflective mirror. The bottom of the mounting bracket has an optical window. The laser beam introduced through the second laser incident interface is reflected by the reflective mirror and output from the optical window at a preset angle, then enters the branched quadrupole mechanism through the first laser incident interface. The angle between the quadrupole branch and the quadrupole body is 60°.

[0042] The specific usage process of the device in this embodiment is as follows: Step 101: Precisely adjust the laser incident direction to ensure that the laser beam can accurately pass through the middle cavity of the branched quadrupole mechanism and focus on the preset particle suspension area at the bottom, so as to conduct optical observation and characteristic analysis of the suspended particles in the future.

[0043] Step 102: Apply an AC voltage of a specific frequency and amplitude to the branched quadrupole mechanism, and simultaneously apply an initial DC voltage to the DC balance plate to construct a composite electric field environment within the cavity that meets the requirements for particle suspension.

[0044] Step 103: Sample injection operation. The following methods are used for different types of particles: For solid particles: Use a micro-sampling tool to pick up a small amount of solid sample powder; apply a high voltage to the tip of the sampling needle to charge the solid particles using the tip discharge effect; then carefully introduce the charged solid particles into the cavity electric field region of the branched quadrupole mechanism.

[0045] For liquid droplets: an appropriate voltage is applied to the induction electrode (i.e., the particle charging unit) to assist in the formation and charging of droplets; then the piezoelectric spray device is started and stabilized to atomize the liquid sample into tiny droplets through the piezoelectric effect. These droplets carry a net charge under the action of the induction electrode and the nozzle (i.e., the particle injector) and are guided into the cavity with the electric field environment that has been constructed.

[0046] Step 104: Observe the movement and falling of particles in the cavity in real time using a laser observation system; adjust the voltage value of the DC balance plate precisely based on the observation results.

[0047] This invention, for the first time, extends the branched quadrupole electrodynamic balancer (BQ-EDB) from droplet suspension to solid particle suspension. It utilizes 60° branched electrodes to introduce particles, employing high-voltage pulse charging on solid particles and inductive charging on droplets. A highly uniform potential trap is constructed vertically and superimposed with a DC balancing plate to achieve stable particle suspension. The branched configuration spatially decouples laser observation and particle introduction path, ensuring that droplets and solid particles can be introduced and manipulated independently within the same cavity, and optical characterization is performed using laser scattering. Overall, this invention provides a universal containerless platform compatible with both solid and liquid phase particles for in-situ characterization of air-suspended particles.

[0048] The innovative aspects of the solid-liquid particle suspension device of this invention are described below: (a) Cross-shaped DC balance plate: DC balance board (e.g.) Figure 6 The main body (as shown) is designed as a cross-shaped conductive structure with a central through-hole (e.g., 2 mm) serving as a channel for the suspended droplets to fall. Mounting holes are located at the four ends of the cross-shaped conductive structure. These mounting holes have a dual function: firstly, they are used to connect a DC high-voltage power supply, typically applying a DC voltage with the same polarity as the net charge of the particles to be suspended, generating an upward electrostatic force to balance the particle's gravity and aerodynamic force, achieving axial suspension; when particle detachment is required, a reverse voltage is applied. Secondly, the mounting holes are used to securely mount the entire cross-shaped voltage plate to the insulating base at the bottom using mechanical connectors (such as insulating screws). This fixing method not only ensures that the voltage plate does not shift during the experiment but also guarantees a high degree of repeatability and consistency in the spatial distribution and intensity of the electric field generated by this electrode structure in each suspension experiment, thus providing a reliable electric field environment for subsequent precision measurements or operations.

[0049] (b) "Tip-high voltage pulse charging" injection method for solid particles: This device employs a "tip-based high-voltage pulse charging" method for introducing solid particles, distinct from the "inductive charging" method used for liquid droplets. Specifically, an insulated micro-sampling tool (such as a sleeve-type conductive needle) is used to collect a trace amount of solid particle sample. A momentary high-voltage pulse is then applied to the metal tip of this tool. The high-voltage pulse generates a strong electric field at the tip, causing the solid particles attached to the tip to carry a net charge of the same polarity as the pulse voltage through corona discharge or field emission. The charged solid particles are then directly released and introduced into the established levitation electric field region under the influence of gravity and the electric field. This method achieves precise and controllable charging of solid particles, allowing them to be immediately captured by the levitation electric field after charging. It effectively avoids the drawbacks of traditional powder spraying or dispersion methods, such as the irregular diffusion and scattering of particles, which contaminate the internal optical windows and other clean areas of the device. This significantly improves the reliability, success rate, and cleanliness of the experimental environment for solid particle levitation.

[0050] (c) Can switch between different working modes In addition to its basic operating mode, where the laser is incident vertically downwards from above the device while solid or liquid particle samples are introduced through lateral branch channels for observation, the device can switch to other operating modes. For example, by adjusting the optical path, the laser can be incident vertically upwards from below the device. In this mode, particles can be introduced simultaneously through the top main channel and the side branch channels, allowing particles from both sources to converge in the central region of the quadrupole electric field trap, thus enabling controlled particle collision experiments. This feature expands the device's application range, enabling it to be used to study the interactions, coagulation, and kinetic reaction processes between particles of different phases.

[0051] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A solid-liquid particle suspension device based on a branched quadrupole electrodynamic balancer, characterized in that, include: A branch-type quadrupole mechanism includes a quadrupole body arranged vertically and a quadrupole branch connected at an inclination to the quadrupole body. The top of the quadrupole body is provided with a first laser incident interface, and the quadrupole branch has an independent feeding channel. The adjustable laser emitting mechanism located at the top of the branched quadrupole mechanism is configured to generate a laser beam and introduce it into the center of the branched quadrupole mechanism via the first laser incident interface. The DC balance plate located at the bottom of the branched quadrupole mechanism includes a conductive plate and an insulating fixing plate that can fix the bottom of the quadrupole body. The conductive plate has a cross-shaped structure, with connection holes for connecting DC voltage at the ends and a central opening for droplet drop holes. The insulating fixing plate is connected to the conductive plate, so that the conductive plate and the branched quadrupole mechanism are mutually insulated. The particle injection mechanism located at the top of the quadrupole branch is configured to generate droplets or solid particles to be observed. The system includes a sealed chamber, comprising an upper chamber surrounding the upper part of the quadrupole body, a lower chamber surrounding the lower part of the quadrupole body, and a side chamber surrounding the quadrupole branch. The upper chamber is connected to the lower chamber and the side chamber, respectively.

2. The solid-liquid particle suspension device based on a branched quadrupole electrodynamic balancer according to claim 1, characterized in that, Both the main body and branches of the quadrupole contain four poles, which are fixed by ceramic rings to ensure that adjacent poles are insulated from each other. Among the four poles, the two diagonally opposite poles are connected by a conductive bridge and form a potential well by applying alternating current in the same direction.

3. The solid-liquid particle suspension device based on a branched quadrupole electrodynamic balancer according to claim 1, characterized in that, The particle injection mechanism includes a particle injector, a metal clip, and a particle charging unit. The particle injector is used to form droplets or solid particles, the metal clip is used to fix the particle injector, and the particle charging unit is used to apply high voltage and cause the droplets or solid particles to carry a charge opposite to or the same as that of the particle charging unit.

4. A solid-liquid particle suspension device based on a branched quadrupole electrodynamic balancer according to claim 3, characterized in that, The metal clip is also grounded.

5. A solid-liquid particle suspension device based on a branched quadrupole electrodynamic balancer according to claim 1, characterized in that, The top of the upper chamber is provided with an upper chamber connecting plate and an upper chamber cover in sequence, and the side panel of the upper chamber is also provided with a first BNC wire connection hole; The lower chamber is also provided with several circular optical windows on its side for observing the suspension state of particles. The lower chamber is also provided with a second BNC wire connection hole on its side, and the top is connected to the upper chamber through a connecting screw hole. The side chamber is connected to the particle injection mechanism via a connecting plate.

6. A solid-liquid particle suspension device based on a branched quadrupole electrodynamic balancer according to claim 1, characterized in that, The top of the upper chamber is also provided with an inlet for introducing reactive gas or a dry-wet mixed nitrogen gas. The side of the lower chamber is also provided with a probe insertion hole for inserting a humidity monitoring probe and monitoring the relative humidity inside the sealed chamber.

7. A solid-liquid particle suspension device based on a branched quadrupole electrodynamic balancer according to claim 1, characterized in that, The adjustable laser emitting mechanism includes a laser generator, two plane mirrors and a mounting and adjusting frame. The left and right deflection and up and down tilt angles of the two plane mirrors are adjustable so that the laser beam generated by the laser generator is incident into the mounting and adjusting frame at a preset height in a horizontal posture. One side surface of the mounting and adjusting frame is provided with a second laser incident interface for docking with the laser beam generated by the laser generator. Inside the mounting and adjusting frame, there is also an adjustable reflector mounting base with a reflective lens. The bottom of the mounting and adjusting frame is provided with an optical window. The laser beam introduced through the second laser incident interface is reflected by the reflective lens and output from the optical window at a preset angle, and then enters the branched quadrupole mechanism through the first laser incident interface.

8. A solid-liquid particle suspension device based on a branched quadrupole electrodynamic balancer according to claim 1, characterized in that, The angle between the quadrupole branch and the quadrupole body is 60°.

9. A method for suspending solid-liquid particles based on a branched quadrupole electrodynamic balancer, implemented using the solid-liquid particle suspension device as described in any one of claims 1-8, characterized in that, The solid-liquid particle suspension method includes the following steps: S1. Adjust the laser incident direction of the adjustable laser emitting mechanism to ensure that the laser beam can pass through the middle cavity of the branched quadrupole mechanism and be focused on the preset particle suspension area. S2. Apply an AC voltage of predetermined frequency and amplitude to the poles of the branched quadrupole mechanism, and at the same time apply an initial DC voltage to the DC balance plate to construct a composite electric field environment that meets the requirements for particle suspension. S3. Droplets or solid particles are generated by the particle injection mechanism and introduced into the preset particle suspension area in S1. S4. Real-time observation of the motion and falling of droplets or solid particles in the intermediate cavity of the branched quadrupole mechanism.

10. A method for suspending solid-liquid particles based on a branched quadrupole electrodynamic balancer according to claim 9, characterized in that, In S4, the voltage value of the DC balance plate is adjusted according to the feedback observation results until the droplets or solid-liquid particles can remain stably suspended above the DC balance plate and within the preset target height range. The adjustment of the DC voltage value satisfies the following conditions: (a) The DC voltage value changes continuously or in steps during the adjustment process, and the direction and amplitude of the change are determined in real time according to the displacement deviation of the particles in the vertical direction; (b) The adjusted voltage value should balance the resultant force of electrostatic force, gravity and fluid resistance on the particles in the vertical direction; (c) The height range of the target droplet or solid-liquid particle ensures that it can be clearly observed and facilitates subsequent optical characterization operations.

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