Superfine particulate matter screening and conveying device and method

Abstract

The invention provides a screening and conveying device and method for ultrafine particles, and the device comprises a charge screening module which is used for carrying out the target particle size and charge screening of entering aerosol particles; the aerodynamic lens is used for focusing the screened charged particles and forming particle beams; the cooling bunching module comprises a radio frequency multi-pole rod and is used for cooling the charged particles in the transmission process and keeping the charged particles in an axial area; the differential transmission module comprises a radio frequency multi-pole rod, is arranged between the cooling bunching device and the trapping device, and is used for realizing air pressure transition and further constraining particles; and the trapping module comprises a linear ion trap and is used for trapping the charged particles. According to the invention, the particle loss of particles in the transmission process is effectively reduced, and the transmission efficiency and trapping rate of the particles are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mass spectrometers, in particular to a screening and transmission device and method for ultrafine particulate matter. BACKGROUND

[0002] Time-of-flight mass spectrometry (TOF-MS) is widely used in scientific research and industrial detection due to its high mass resolution, fast detection speed, and wide mass range. Existing systems usually configure ion lenses and DCQ optical elements between the ion source and the TOF analysis area, and use empirical formulas and local optimization algorithms for tuning. Although this method is simple to implement, it is prone to local optimization and difficult to improve both resolution and sensitivity in the multi-parameter coupling tuning space.

[0003] Global search algorithms can expand the optimization range, but due to the fact that the fitness function is based on a single signal indicator, there is a lack of real-time feedback on ion beam spatial distribution and divergence, which limits the convergence efficiency and tuning accuracy. Traditional TOF systems rely on the overall signal output by the end detector, which cannot obtain the beam width and intensity distribution before the ions enter the TOF, resulting in a blind area in the optimization process and poor stability of the tuning results.

[0004] Therefore, there is an urgent need for an adaptive tuning method that can obtain real-time data on beam width and intensity distribution before the TOF entrance, and combine it with multi-dimensional performance indicators to construct a fitness function, thereby achieving global fast optimization and stable reproduction. SUMMARY

[0005] The present application provides a screening and transmission device and method for ultrafine particulate matter, which effectively reduces particle loss during transmission, improves transmission efficiency and capture rate of particles.

[0006] The present application provides a screening and transmission device for ultrafine particulate matter, comprising: A charged screening module for target particle size and charged screening of incoming aerosol particles; An aerodynamic lens for focusing and forming a particle beam on the screened charged particles; A cooling and bunching module including a radio frequency multipole rod for cooling and maintaining charged particles in an axial region during transmission; A differential transmission module including a radio frequency multipole rod, arranged between the cooling and bunching device and the trapping device, for realizing air pressure transition and further constraining particles; A trapping module including a linear ion trap for trapping the charged particles.

[0007] In some embodiments, the charged particles are focused into a beam shape in the aerodynamic lens and obtain initial kinetic energy during outflow; The charged particles enter the cooling and bunching module, collide with gas molecules to be cooled, and are further focused in the radio frequency field formed by the radio frequency multipole rod, and the kinetic energy of the particles is reduced. The charged particles enter the trapping module, collide further with the buffer gas, and are captured by the linear ion trap.

[0008] In some embodiments, the working parameters of the cooling and bunching module, the differential transmission module and the trapping module are determined according to the particle size of the charged particles to be analyzed.

[0009] In some embodiments, the working conditions of the square wave radio frequency, the direct current voltage gradient and the square wave voltage of the cooling and bunching module are dynamically controlled according to the particle size; and the working gas pressure and the square wave radio frequency of the linear ion trap of the trapping module are dynamically adjusted according to the particle size.

[0010] In some embodiments, the screening and transmission device of ultrafine particulate matter includes a first mode and a second mode, the first mode is a single particle size transmission mode, only particles of a certain particle size enter within a preset time period, and the electronic control system sets fixed working parameters according to the particle size; The second mode is a continuous scanning mode, particles of different particle sizes continuously enter within a preset time, and the electronic control system dynamically adjusts the working parameters according to different particle sizes within the working time period of the second mode.

[0011] In some embodiments, the cooling and bunching module adopts a first quadrupole rod, and the differential transmission module adopts a second quadrupole rod. The length of the first quadrupole rod is not less than that of the second quadrupole rod, the first quadrupole rod adopts a segmented quadrupole rod and sets an equal-gradient direct current in each segment of the quadrupole rod to form a direct current gradient. Alternatively, the first quadrupole rod adopts a LINAC type quadrupole rod, and a direct current is added to the wedge-shaped planar electrode plate to form a direct current gradient.

[0012] In some embodiments, the first quadrupole rod uses air molecules output by the aerodynamic lens as a cooling medium.

[0013] In a second aspect, the application discloses a screening and transmission method of ultrafine particulate matter, which is applied to the screening and transmission device of ultrafine particulate matter as described above, and includes: The aerosol particles are charged and screened to obtain charged particles of a target particle size; When the charged particles are introduced into the aerodynamic lens, an electric field is applied to the aerodynamic lens during the transmission process to reduce the beam width. When the charged particles enter the cooling bunching module, a square wave radio frequency and a direct current voltage gradient are applied to the cooling bunching module, and the particles are gathered and cooled near the axis by controlling the collision of the charged particles with air molecules; When the charged particles are introduced into the trapping module through the differential transmission module, the radio frequency voltage, frequency and gas pressure conditions of the trapping module are adjusted according to the particle size, and trapping is performed.

[0014] In some embodiments, the radio frequency voltage, frequency and gas pressure conditions of the trapping module are adjusted according to the particle size, including: The working gas pressure and square wave radio frequency of the trapping module are adjusted according to the particle size of the charged particles, so that the working parameters match the particle size of the charged particles.

[0015] In some embodiments, the frequency of the square wave radio frequency increases as the particle size decreases, and the direct current voltage gradient decreases as the particle size decreases.

[0016] The present application provides a kind of screening and transmission device, method of ultrafine particulate matter, ultrafine particulate matter can be continuously controlled in the whole process of charging, transmission, cooling, transition and trapping, wherein aerodynamic lens cooperates with additional electric field to effectively reduce beam width and inhibit diffusion, cooling bunching module uses subsection quadrupole to realize stable focusing in combination with square wave radio frequency and dynamic direct current gradient, differential transmission module ensures that gas pressure is smoothly transitioned, linear ion trap is combined with dynamic adjustment to broaden trapping range.The present application effectively reduces particle loss during transmission process, improves particle transmission efficiency and trapping rate. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 a schematic view of the screening and transmission device of ultrafine particulate matter provided by the present application; Figure 2 a comparison schematic view of particle transmission efficiency provided by the present application; Figure 3 a schematic view of square wave radio frequency following particle size dynamic adjustment of radio frequency based on digital circuit provided by the present application; Figure 4 a schematic view of particle size and time, direct current gradient provided by the present application; Figure 5 a schematic view of particle size trapped by the trapping device of prior art; Figure 6 a schematic view of particle size trapped by the screening and transmission device of ultrafine particulate matter provided by the present application; Figure 7 a schematic view of dynamic adjustment of radio frequency electric field and gas pressure conditions with time and particle size change provided by the present application; Figure 8This is a schematic flowchart of the screening and transport method for ultrafine particles provided by the present invention. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings.

[0019] This application provides a screening and transport device for ultrafine particles, which effectively reduces particle loss during transport and improves particle transport efficiency and capture rate.

[0020] like Figure 1 As shown, the device provided in this application includes a charged sieving module, an aerodynamic lens, a cooling focusing module, a differential transmission module, and a trapping module. The charged sieving module is used to sieve the incoming aerosol particles according to their target size and charge; the aerodynamic lens is used to focus the sieved charged particles and form a particle beam; the cooling focusing module includes a radio frequency multipole for cooling the charged particles during transmission and keeping them in the axial region; the differential transmission module includes a radio frequency multipole, disposed between the cooling focusing device and the trapping device, for achieving air pressure transition and further confining the particles; the trapping module includes a linear ion trap for trapping the charged particles.

[0021] Since aerosol nanoparticles in the environment are inherently uncharged, the aerosol particles entering this device need to be charged by the device. The charged sieving module in this application includes a single-stage charger and an electrostatic classification unit. A 210Po radiation source is installed at the inlet of the single-stage charger. This radiation source emits alpha particles to ionize the aerosol particles, thus charging them. The charged particles pass through the electrostatic classification unit, where they are separated based on the different electromobilities of particles with different charge-to-mass ratios in the electrostatic field, thereby completing the sieving of particles of different sizes.

[0022] Particles within the target particle size range, selected from the charged sieving module, enter the aerodynamic lens. Typically, a conventional aerodynamic lens consists of a buffer chamber (135mm long, 45mm inner diameter) and a lens assembly (typically 10mm inner diameter). Particles pass through the buffer chamber and lens assembly sequentially, being focused into a beam along the axial direction. This provides the particles with initial kinetic energy to facilitate subsequent transport and preliminary focusing. However, because the particles exiting the aerodynamic lens still exhibit some angular divergence, this type of lens primarily relies on the lens aperture and nozzle geometry to limit particle trajectory. This only improves axial transport to a certain extent, offering insufficient control over radial particle diffusion and failing to effectively reduce the impact of random Brownian motion disturbances. Therefore, the particle beam output from the lens still exhibits significant angular divergence, limiting its spatial focusing performance.

[0023] Therefore, the structure of the aerodynamic lens is improved in this application. The length of the buffer cavity is set to 150~210mm, the inner diameter of the buffer cavity is 23~26mm, and the inner diameter of the lens group is 15~18mm. The buffer cavity is designed to decelerate the aerosol particles entering from the front end, so that the particles obtain a more uniform velocity distribution before entering the lens group. By reducing the inner diameter of the buffer cavity, the velocity gradient inside the cavity can be reduced, thereby effectively controlling the generation of vortices in the local flow field and avoiding turbulence interfering with the particle trajectory.

[0024] The buffer cavity needs to be relatively long to ensure that ultrafine particles are sufficiently decelerated before entering the lens group. Therefore, in this application, the length of the buffer cavity is preferably 180 mm to balance stability under different airflow conditions. If the inner diameter of the buffer cavity is too large, particles are prone to generating annular vortices in the buffer section, causing some particles to deviate from the axis; if the inner diameter is too small, it will excessively restrict the gas flow channel, resulting in uneven airflow velocity distribution and reducing transmission efficiency. In this application, an inner diameter of 24 mm is used to maintain an approximately laminar flow state, ensuring stable axial transmission of particles. The inner diameter of the lens group matches the buffer cavity. If the deviation is large, particles are prone to streamline separation at the lens group inlet; if the deviation is too small, it will increase collision losses between particles and the channel wall. In this embodiment, the lens group is set with an inner diameter of 16 mm, which matches the 24 mm inner diameter of the buffer cavity, so that the particles form a good focusing effect within the lens group.

[0025] Furthermore, a pre-focusing assembly is added at the front end of the buffer cavity and lens group. This assembly consists of multi-stage cavities and perforated plates, with a focusing aperture at the tail end of each stage of the perforated plate. As the particle stream passes through each focusing aperture sequentially, the beam range narrows progressively, thereby controlling the initial beam width. This pre-focusing process provides the particles with a certain initial velocity distribution; therefore, a relatively long buffer section is set between the pre-focusing assembly and the lens group to further balance the flow field and ensure that the particles maintain a relatively stable flow state when entering the lens group.

[0026] The pre-focusing assembly includes three cavities arranged in series and a critical orifice plate. Each cavity has a focusing orifice at its tail end, and the focusing orifice, critical orifice plate, and gas delivery pipe inlet are all coaxially arranged along the central axis. This embodiment uses a pre-focusing assembly based on the same principle, but the relevant structural parameters have been optimized using FLUENT fluid simulation to suit the application scenario of this technology, while maintaining the same working principle. Specifically, when the particle stream enters the first cavity of the pre-focusing assembly with the gas stream, it exits through the focusing orifice at the tail end of the cavity, where the fluid streamlines are converged into a bundle, thereby reducing fluid broadening and initially controlling the bundle width. Subsequently, the particles enter the second cavity, and the bundle width is further reduced when passing through the focusing orifice at the tail end of the second cavity. The third cavity functions similarly to the first two stages, achieving multi-stage gradual contraction of the bundle. Each cavity has vortex chambers on both sides; when the fluid enters the vortex chambers, it forms vortices, creating a low-pressure zone near the central axis of the cavity. When particulate matter passes through a low-pressure area under the action of gas dynamics, it will accelerate, which will improve the permeability of particulate matter and the stability of the flow field, effectively reduce the initial beam width and improve the transmission performance of particulate matter.

[0027] The pre-focusing component, while compressing the beam width, also imparts a high initial velocity to the particles. To avoid the impact of high-speed particle motion on subsequent aerodynamic lens transmission, a relatively long buffer cavity is set between the pre-focusing component and the lens group. The inner diameter of the buffer cavity is optimized based on FLUENT simulation results to maintain laminar airflow and prevent the generation of vortices from reducing particle transmission efficiency.

[0028] Furthermore, by superimposing an additional electric field within the lens channel, charged particles are subjected to an electric force during transmission, thereby limiting radial random motion, reducing the disturbance of particle trajectories by Brownian motion, and minimizing kinetic energy exchange between gas molecules and ultrafine particles. The particle beam transmitted through this lens exhibits significantly suppressed spatial diffusion and angular divergence compared to the condition without an applied electric field.

[0029] Through the above improvements, such as Figure 2 As shown in Tables 1 and 2, the particle transport efficiency can reach over 60%, and the relevant parameters were determined through FLUENT fluid simulation.

[0030] Table 1. Simulated state of ultrafine particles focused by aerodynamic lenses in existing technologies.

[0031] Table 2. State of ultrafine particles focused by the improved aerodynamic lens of this invention.

[0032] After exiting from the tail end of the aerodynamic lens, the particles first pass through a field-free region of approximately 6 mm, where the particle beam undergoes some diffusion. They then enter a cooled focusing device composed of cylindrical quadrupoles. In existing technology, cylindrical quadrupoles approximately 10 cm in length are typically used as particle guiding devices, with a sinusoidal radio frequency voltage of ±50V and a frequency of 50 kHz applied to them. However, the particles cannot be effectively focused near the axis of the device, instead generating strong oscillations in the electric field formed by the quadrupoles, thus affecting the beam stability and transmission efficiency.

[0033] To address the aforementioned issues, this embodiment incorporates a cooling focusing module, including a radio frequency (RF) multipole. Specifically, a first quadrupole is employed, to which a square wave RF voltage is applied. A DC gradient, dynamically controlled by a timing board, is applied to each segment of the first quadrupole, cooling the charged particles during collision and confining them to their position near the axis. The first quadrupole is a 15cm cylindrical quadrupole, with a square wave voltage of ±500V applied to its electrodes at a frequency of 50kHz. This first quadrupole consists of two sets of cylindrical electrodes, with each pair of opposing cylindrical electrodes receiving a square wave voltage of the same polarity, thus creating a stable quadrupole field within the device. Compared to traditional sinusoidal RF signals, the digital square wave signal exhibits less fluctuation during voltage switching, effectively improving the stability of the field distribution, reducing violent particle vibrations in the electric field, and enhancing the focusing effect.

[0034] Furthermore, the voltage value set at ±500V is not a fixed parameter, but rather a reference range proposed in this embodiment. Its design purpose is to ensure higher focusing efficiency of particles during transmission. The specific voltage value can be dynamically adjusted based on the particle transmission efficiency of different particle size ranges, combined with the results of ion optics simulation, to achieve optimal cooling and focusing effects.

[0035] In this electric field environment, charged particles can be well confined to the vicinity of the field's central axis, while their axial velocity is also reduced to some extent. Since the particles exiting the aerodynamic lens still carry high initial kinetic energy, they will be difficult to stably capture by subsequent devices without effective control. Generally, this is achieved by introducing inert argon (Ar) gas into the particle guiding device and controlling the internal pressure at approximately 2E-2 mbar. The introduced argon molecules collide with the charged particles, transferring some of the high-energy particles' kinetic energy to the argon molecules during the collision, converting it into thermal energy, thereby achieving particle cooling and focusing. The relevant collision process can be simulated and calculated using a hard-sphere collision model.

[0036] Considering the complexity of introducing argon gas path structure into the device design, this application directly utilizes air molecules flowing out of the aerodynamic lens as the cooling medium, while maintaining the cooling and focusing effect, and introduces them into the cooling and focusing device. During the collision process with the ultrafine particles, the air molecules do not change the chemical composition of the ultrafine particles and can be used as an inert gas to achieve the cooling effect, while also saving costs and simplifying the system structure.

[0037] Furthermore, this application employs a segmented cylindrical quadrupole instead of a traditional digital particle guiding device as the cooling and focusing assembly. The operating pressure of this device is maintained at approximately 10 Pa, which is more conducive to creating an effective collision cooling environment compared to the typical operating pressure of approximately 1E-3 Pa. Ultrafine particles of different sizes exhibit different transmission characteristics under different radio frequency voltages and frequencies. Therefore, based on a square wave radio frequency driven by digital circuits, the radio frequency is dynamically adjusted to adapt to the transmission requirements of particles of different sizes, achieving a more efficient cooling and focusing process.

[0038] like Figure 3 The diagram illustrates a square wave radio frequency (RF) frequency dynamically adjusted based on particle size using digital circuitry to follow particle size. The RF frequency decreases as the particle size increases. Compared to traditional particle guiding quadrupoles, the first quadrupole of the cooling focusing device employs segmented cylindrical electrodes. The cylindrical quadrupole is segmented at equal intervals, and a specific DC gradient is applied to each segment of the annular electrode. This DC gradient is not a fixed value, but rather varies as shown in the diagram. Figure 4 As shown, the DC voltage gradient is adjusted according to the particle size of the charged particles, and decreases as the particle size decreases, so that the optimal transmission and focusing effect can be obtained under different particle size conditions.

[0039] Specifically, a timing control board can be set in the circuit to achieve time-division control of the DC voltage of the cylindrical electrodes in different segments. The optimal DC voltage parameters for each particle size range are calculated by ion optics simulation, enabling the timing control board to dynamically adjust the DC gradient according to preset logic. In this way, ultrafine particles with a particle size range of 1~50nm can move in the cooling and focusing device under optimal transmission and focusing conditions. However, considering the technical difficulty of adding DC gradients to segmented quadrupoles, in some embodiments, the first quadrupole can be a LINAC type quadrupole. A square wave radio frequency is added to the cylindrical electrode plate according to the above method, and DC current is added to the four wedge-shaped planar electrode plates in the asymptotic direction to achieve the superposition of DC gradients. The LINAC type quadrupole consists of four round rods and four square rods, wherein the four round rods are axially parallel and apply radio frequency voltage to bind ions, and the four square rods are at an angle of 0.2° relative to the axis. The four square rods can also be replaced with wedge-shaped planar electrode plates, as long as the same effect of forming a DC gradient is achieved. In this application, wedge-shaped planar electrode plates are used.

[0040] like Figure 5 As shown in the diagram, the red shaded area represents particles that can be captured by subsequent capture devices. Traditional particle guiding modules can only capture particles with a diameter of 10-30 nm, and ultrafine particles cannot be sufficiently cooled to increase the range of particle sizes that can be captured. Figure 6 As shown, the cooling and focusing module provided in this application can effectively capture particles with a diameter of 10~50nm by the subsequent capturing module and cool the kinetic energy of the ultrafine particles to about 10eV. It is superior to traditional guiding modules in terms of transmission range and cooling efficiency.

[0041] After passing through the cooling and focusing module, the particles enter the differential transmission module. The differential transmission module, located between the cooling and focusing module and the trapping module, includes an RF multipole located at the outlet of the cooling and focusing module, forming a pressure transition zone and further focusing the particles. In this module, the RF multipole is a second quadrupole, which is a differential quadrupole, located at the outlet of the cooling and focusing module. It functions as a transmission device that gradually transitions from low pressure to vacuum conditions, with its operating pressure differing from the pressure in the cooling and focusing device by approximately two orders of magnitude. Figure 1 As shown, the length of the first quadrupole is no less than that of the second quadrupole. Compared to traditional aerodynamic lenses and particle digital guidance devices, where there is a pressure difference of more than three orders of magnitude between them, stable pressure transition is easier to achieve.

[0042] A square-wave radio frequency field is introduced inside the differential quadrupole to further constrain the particle flow state, achieving particle re-bundling and reducing their initial kinetic energy before entering the linear ion trap. Compared with existing technologies that use an electrostatic lens with a width of approximately 2.5 nm and apply a DC gradient, this device has higher transmission efficiency, reduces particle loss during transmission, and improves the subsequent trapping performance of the linear ion trap.

[0043] However, the particles exiting the differential transmission module still have a certain divergence angle, resulting in a deflection relative to the axial direction. This deflection causes the particles to enter the subsequent trapping device with a certain incident angle, increasing the probability of effective capture. In the particle trapping stage, a circular quadrupole is traditionally used as the trapping device. A square wave voltage of -507V / +504V is applied to the circular electrodes at both ends, and a pulsed DC current of +1300V / -500V is applied at the end cap to form a confinement field. This confines particles within a specific size range and causes them to vibrate back and forth along the Z-direction in the electric field. This trapping module composed of a quadrupole is called an ion trap. This invention uses a linear ion trap composed of four planar rectangular electrode plates, which offers advantages such as simple fabrication, easy access to the electrode plates, and further reduced particle loss.

[0044] An appropriate amount of argon gas is introduced into the linear ion trap, allowing charged particles to be further cooled and focused through collisions, thereby confining as many particles as possible within the trap. Subsequently, a high-energy laser is used to irradiate the central region of the trap; the irradiated ions are ionized under the laser's influence. Furthermore, as... Figure 7 As shown, the operating parameters of the linear ion trap can be dynamically set according to the particle size of the analyte, including the frequency of the radio frequency voltage and gas pressure conditions. A timing control board is introduced into the connection circuit, which can dynamically adjust the voltage, frequency, and DC gradient of the ion trap and cooling focusing device according to different sample particle sizes, ensuring that the operating parameters match the particle size characteristics. Under these power conditions, optimal transport, cooling focusing, and collection efficiency can be achieved for ultrafine particles in the 1–50 nm particle size range. Unlike existing technologies where voltage and frequency conditions are fixed, this method breaks through the limitation of particle collection range being limited to 20–30 nm, achieving effective cooling and efficient collection across the entire particle size range of 1–50 nm, reducing particle loss during transport. The collected particles then enter a mass analyzer for mass analysis.

[0045] During operation, charged particles are focused into a beam within the aerodynamic lens and gain initial kinetic energy as they flow out. After passing through the aerodynamic lens, the charged particles enter the cooling and focusing module, where they collide with gas molecules and are cooled. They are further focused by the electric field in the radio frequency field formed by the radio frequency multipole, further reducing their kinetic energy. After entering the trapping module, the charged particles are further cooled by collisions with the buffer gas and are then captured by the linear ion trap.

[0046] The ultrafine particle screening and transport device provided in this application has its operating parameters for the cooling focusing module, differential transport module, and collection module determined according to the particle size of the charged particles to be analyzed. Specifically, the operating conditions of the cooling focusing module, including its square wave radio frequency, DC voltage gradient, and square wave voltage, are dynamically controlled based on the particle size; the operating gas pressure and square wave radio frequency of the linear ion trap in the collection module are dynamically adjusted according to the particle size.

[0047] Based on the above adjustment process, the ultrafine particle screening and transport device includes a first mode and a second mode. The first mode is a single particle size transport mode, in which only particles of one size enter within a preset time period. The electronic control system sets fixed operating parameters according to this particle size. After detecting or setting the particle size, the electronic control system fixes the radio frequency voltage and DC voltage gradient of the cooling clustering module, as well as the radio frequency and gas pressure conditions of the linear ion trap, to optimal values ​​that match the particle size. When charged particles pass through the cooling clustering module under these fixed conditions, they collide with gas molecules and are cooled, and are constrained in the axial region under the action of a stable electric field, eventually entering the linear ion trap and being effectively captured. The principle of this mode is that the fixed parameters correspond to a single particle size, eliminating the need for frequent switching of control conditions, ensuring stable operation, and making it suitable for efficient detection and analysis of particles of a specific size.

[0048] The second mode is a continuous scanning mode, in which particles of different sizes continuously enter within a preset time period. During the second mode's operating time, the electronic control system dynamically adjusts the operating parameters according to the different particle sizes. The charged sieving module continuously outputs charged particles of different sizes. The electronic control system, using a pre-stored parameter table, dynamically switches the radio frequency and DC voltage gradient at the timing point when the particles enter the cooling and focusing module, ensuring that particles of different sizes are cooled and focused under optimal conditions. Subsequently, when the particles enter the linear ion trap, the electronic control system continues to dynamically adjust the radio frequency and gas pressure conditions inside the trap according to the entering particle size, maintaining a match between the electric field distribution inside the trap and the particle size characteristics. By using a timing board to programmatically schedule the operating parameters, rapid switching across multiple particle size ranges can be achieved in a short time, enabling continuous scanning and efficient collection of ultrafine particles from 1 to 50 nm, avoiding the limitations of traditional screening devices that can only handle a limited particle size range. Through these two operating modes, this device can ensure stability and accuracy in a single particle size mode, while also achieving dynamic adaptation and high-efficiency detection across a wide particle size range in continuous scanning mode, improving the applicability and flexibility of the device.

[0049] like Figure 8 As shown, this application also provides a method for screening and transporting ultrafine particles, applied to an ultrafine particle screening and transport device as described above, comprising the following steps: Step S1: Charge and sieve the aerosol particles to obtain charged particles of the target particle size. Step S2: When charged particles are introduced into the aerodynamic lens, an electric field is applied to the aerodynamic lens during transmission to reduce the beam width; Step S3: When charged particles enter the cooling focusing module, a square wave radio frequency and a DC voltage gradient are applied to the cooling focusing module, and the particles are gathered and cooled near the axis by controlling the collision between charged particles and air molecules. Step S4: When charged particles are introduced into the collection module through the differential transmission module, the radio frequency voltage, frequency and air pressure conditions of the collection module are adjusted according to the particle size to perform collection.

[0050] First, the aerosol particles are charged, and charged particles of the target size are screened out by an electrostatic classifier. The charged particles are then introduced into a buffer chamber and transported through a lens group and a pre-focusing airflow channel. Simultaneously, an electric field is applied within the lens structure to constrain the particle flow and reduce the beam width. Next, the particles enter a cooling and focusing module composed of segmented cylindrical quadrupoles. Cooling and focusing are achieved through the combined action of a square wave radio frequency voltage and a variable DC voltage gradient, utilizing air molecule collisions. The particles are then introduced into a differential transmission module, where a square wave radio frequency voltage continues to be applied in the pressure transition zone between low pressure and vacuum to maintain stable particle transport. Finally, the particles enter a collection device, where the radio frequency voltage frequency and pressure conditions are dynamically adjusted according to the particle size to collect particles ranging from 1 to 50 nm. The collected particles are then subjected to laser ionization for mass analysis by a mass analyzer.

[0051] Optimal voltage and frequency conditions for the transport and cooling of charged particles of different sizes were established through ion optics simulation. For a particle size range of 1–50 nm, the simulation yielded the RF voltage and frequency range, the optimal DC voltage gradient distribution within the cooling focusing module, and the optimal operating pressure conditions of the ion trap for each particle size interval. The simulation results were stored in the form of a parameter table and written into the timing control board program. Ultrafine particles in the 1–50 nm particle size range could move under optimal transport and focusing conditions in the cooling focusing device. During particle transport, the corresponding parameter table was automatically invoked based on the output target particle size range. The timing control board adjusted the DC voltage gradient on each segment of the electrodes in the cooling focusing module according to the data in the parameter table, ensuring that the particles gradually decelerated, cooled, and remained near the axis in different segments. The RF frequency applied to the first quadrupole was synchronously adjusted to match the optimal constraint frequency for the specified particle size. After the particles enter the linear ion trap, the amplitude and frequency of the radio frequency voltage on the linear ion trap electrodes are adjusted according to the particle size range of the input particles, and the gas pressure conditions inside the trap are set to match the electric field distribution with the particle characteristics, thereby improving the particle capture stability. Through the above dynamic adjustment mechanism, the system can adapt to particles in the full range of 1~50nm, ensuring that both the cooling and focusing process and the ion trap capture process operate under optimal parameters. Unlike the fixed voltage and frequency methods of existing technologies, dynamic control avoids the defect of inaccurate capture of particles at both ends of the particle size range, enabling efficient transport, cooling, and capture of ultrafine particles throughout the entire range.

[0052] The apparatus and method provided by this invention enable continuous control of ultrafine particles throughout the entire process of charging, transport, cooling, transition, and collection. An aerodynamic lens, combined with an additional electric field, effectively reduces beam width and suppresses diffusion. The cooling and focusing module employs a segmented quadrupole combined with square wave radio frequency and dynamic DC gradient to achieve stable focusing. The differential transmission module ensures smooth pressure transition, and the linear ion trap, combined with dynamic adjustment, widens the collection range. This invention effectively reduces particle loss during transport, improving particle transport efficiency and collection rate.

[0053] Based on the same inventive concept, this application also provides an apparatus, which may include: a memory storing executable program code; A processor coupled to memory; A transceiver used to communicate with other devices or communication networks and to receive or send network messages; A bus used to connect memory, processor, and transceiver for internal communication.

[0054] The transceiver receives messages transmitted over the network and passes them to the processor via the bus. The processor then calls the executable program code stored in the memory via the bus to process the messages and transmits the processing results back to the transceiver via the bus, thereby realizing the ultrafine particle screening and transmission method provided in the above embodiments of this application.

[0055] The present invention discloses a computer-readable storage medium storing a computer program for electronic data interchange, wherein the computer program causes a computer to execute the described method for screening and transporting ultrafine particles.

[0056] The present invention discloses a computer program product comprising a non-transitory computer-readable storage medium storing a computer program operable to cause a computer to perform the ultrafine particle screening and transport method.

[0057] The embodiments described above are merely illustrative. The modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical modules. They may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0058] Through the detailed description of the above embodiments, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, including read-only memory (ROM), random access memory (RAM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), one-time programmable read-only memory (OTPROM), electrically-Erasable Programmable Read-Only Memory (EEPROM), compact disc read-only memory (CD-ROM) or other optical disc storage, disk storage, magnetic tape storage, or any other computer-readable medium that can be used to carry or store data.

[0059] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A device for screening and conveying ultrafine particles, characterized in that, include: The charged sieving module is used to sieve the incoming aerosol particles according to their target particle size and charge. Aerodynamic lenses are used to focus sieved charged particles and form a particle beam. The cooling beam-gathering module includes an RF multipole for cooling charged particles during transmission and keeping them in the axial region; The differential transmission module, including an RF multipole, is positioned between the cooling focusing device and the trapping device to achieve air pressure transition and further confine the particles; The trapping module includes a linear ion trap for trapping the charged particles.

2. The ultrafine particle screening and conveying device as described in claim 1, characterized in that, The charged particles are focused into a beam in the aerodynamic lens and gain initial kinetic energy during the outflow process; After passing through the aerodynamic lens, the charged particles enter the cooling and focusing module, where they collide with gas molecules and are cooled. They are further focused by the electric field in the radio frequency field formed by the radio frequency multipole, and the kinetic energy of the particles is reduced. After entering the trapping module, charged particles are further cooled by collisions with the buffer gas and then captured by the linear ion trap.

3. The ultrafine particle screening and conveying device as described in claim 1, characterized in that, The operating parameters of the cooling focusing module, differential transmission module, and trapping module are determined based on the particle size of the charged particles to be analyzed.

4. The ultrafine particle screening and conveying device as described in claim 3, characterized in that, The operating conditions of the cooling and focusing module, including the square wave radio frequency, DC voltage gradient, and square wave voltage, are dynamically controlled according to the particle size; the operating pressure and square wave radio frequency of the linear ion trap of the trapping module are dynamically adjusted according to the particle size.

5. The ultrafine particle screening and conveying device as described in claim 1, characterized in that, The ultrafine particle screening and conveying device includes a first mode and a second mode. The first mode is a single particle size conveying mode, in which only particles of one size enter within a preset time period. The electronic control system sets fixed operating parameters according to the particle size. The second mode is a continuous scanning mode, in which particles of different sizes continuously enter within a preset time period. The electronic control system dynamically adjusts the working parameters according to the different particle sizes during the working time period of the second mode.

6. The ultrafine particle screening and conveying device as described in claim 1, characterized in that, The cooling beam-gathering module uses a first quadrupole, and the differential transmission module uses a second quadrupole. The length of the first quadrupole is not less than that of the second quadrupole. The first quadrupole is a segmented quadrupole and a DC current of equal gradient is set in each segment of the quadrupole to form a DC gradient. Alternatively, the first quadrupole can be a LINAC type quadrupole, with DC current added to the wedge-shaped planar electrode plate to form a DC gradient.

7. The ultrafine particle screening and conveying device as described in claim 6, characterized in that, The first quadrupole uses air molecules output from the aerodynamic lens as a cooling medium.

8. A method for screening and transporting ultrafine particles, characterized in that, The device for screening and conveying ultrafine particles as described in any one of claims 1 to 7 includes: Aerosol particles are charged and sieved to obtain charged particles of the target particle size. When charged particles are introduced into the aerodynamic lens, an electric field is applied to the aerodynamic lens during transmission to reduce the beam width; When charged particles enter the cooling focusing module, a square wave radio frequency and a DC voltage gradient are applied to the cooling focusing module, and the particles are gathered and cooled near the axis by controlling the collision between the charged particles and air molecules. When charged particles are introduced into the collection module through the differential transmission module, the radio frequency voltage, frequency, and air pressure conditions of the collection module are adjusted according to the particle size to perform collection.

9. The method for screening and transporting ultrafine particles as described in claim 8, characterized in that, Adjusting the radio frequency voltage, frequency, and gas pressure conditions of the trapping module according to particle size includes: The working pressure and square wave radio frequency of the trapping module are adjusted according to the particle size of the charged particles so that the working parameters match the particle size of the charged particles.

10. The method for screening and transporting ultrafine particles as described in claim 8, characterized in that, The frequency of the square wave radio frequency increases as the particle size decreases, and the DC voltage gradient decreases as the particle size decreases.

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