Non-clogging multi-stage micro-plastic particle grading and sorting device based on centrifugal microfluidics and detection method

Abstract

The invention discloses a non-clogging multi-stage micro-plastic particle grading and sorting device based on centrifugal microfluidics, which belongs to the technical field of micro-plastic particle analysis in a water environment and comprises one or more analysis units arranged around a centrifugal axis on a centrifugal micro-fluidic chip, the analysis unit is composed of a digestion treatment module and a micro-plastic particle size sorting and capturing module, and the micro-plastic particle size sorting and capturing module comprises an enhancement liquid chamber, a particle size sorting area, an extrusion microfluid channel, a gradient particle size separation area and a waste liquid chamber. The micro-plastics in different particle size ranges are divided through coupling of centrifugal force and Coriolis force and the dihedral array, the included angle between the centrifugal force direction and the dihedral array is larger than 90 degrees, the effect that the array is not blocked is achieved, the capture rate of micro-plastic particles is high, and errors are small. And fine sorting is carried out on the micro-plastics in different particle size ranges according to the sizes through centrifugal force, and the problem that the particle size sorting range of the micro-plastic particles of a single chip is small is solved. The invention further discloses a non-clogging multistage micro-plastic particle detection method based on centrifugal microfluidics, target micro-plastic can be rapidly and accurately sorted and detected according to different particle sizes and components, and the method has huge advantages in the field rapid detection aspect of the micro-plastic.

Description

Technical Field

[0001] The present invention belongs to the technical field of microplastic particle analysis in water environment, and provides a centrifugal microfluidic non-clogging multi-stage microplastic particle grading and sorting device and a detection method. Background Art

[0002] As a new pollutant, microplastics already exist in every corner of the environment and have been widely detected in lakes, oceans, rivers, atmosphere, soil and organisms. The problem of MPs pollution is becoming more and more serious, and the environmental risks it brings are becoming more and more prominent. These microplastics will enter the water, soil, atmosphere and other media in the environment, and have potential impacts on the environment and ecosystems, such as affecting water quality, disturbing the balance of the ecosystem, and affecting human health.

[0003] At present, the analysis and research of microplastics focuses on three points: sampling, sample pretreatment and MPs identification. The traditional microplastic separation method is a filtration separation method based on membrane filtration, which is limited in its ability to effectively separate micron-sized particles. The loss rate of microplastics produced during separation is high, the superposition error is large, the accuracy is low, and there is a problem that small-particle microplastics below 50 microns are largely ignored during separation. In addition, in the process of digesting and separating microplastics, there is a phenomenon of secondary pollution, the operation steps are cumbersome, the time is long, and the filter is easy to clog.

[0004] The two most commonly used chemical identification techniques are Raman spectroscopy and Fourier transform infrared spectroscopy. The latter method is a reliable method for analyzing microplastics, but the requirement for relatively large samples (>10μm) limits its application. On the other hand, Raman spectroscopy has the advantages of higher resolution and easy sample preparation, and can identify particles with a size close to 1μm. What's more, the method is also applicable to liquid samples, even at the microscopic scale. Matching Raman spectra with reference spectra is now widely regarded as the gold standard method for identifying microplastics.

[0005] Centrifugal microfluidics is a type of microfluidics technology. It uses a motor to drive the microfluidic chip to rotate at high speed, exerting volume force on all media in the microfluidic chip to control the difference between flow and volume force to affect the movement of particles. It does not require an external pressure pump, and its control method is simpler than other methods. In addition, multiple microstructures can be arranged in the chip, which has significant advantages such as parallel high throughput, high efficiency, simple structure, and easy control. However, the existing single-separation chamber centrifugal microfluidic chip can only achieve a specific particle size and a rough division of particles in a small range, and the single-separation chamber centrifugal microfluidic chip cannot achieve the sorting of microplastic particles with a large particle size range in one chip in one step. To improve the sorting range and sorting accuracy, the only way is to increase the length of the separation chamber, increase the centrifugal radius, or increase the rotation speed. These methods are likely to cause the separation chamber to produce eddy currents that are sufficient to affect the sorting effect, reducing the sorting efficiency. Summary of the invention

[0006] In view of this, the present invention proposes a centrifugal microfluidic non-clogging multi-stage microplastic particle grading and sorting device and detection method to realize an integrated technology for rapid collection, processing and characterization of water samples, that is, it can realize a large particle size range of microplastic particles in water samples, without clogging, with small errors, quickly, accurately and effectively grading and detecting.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a non-clogging multi-stage microplastic particle grading and sorting device based on centrifugal microfluidics, comprising one or more analysis units arranged around the centrifugal axis on the centrifugal microfluidic chip, the analysis unit consisting of a digestion processing module and a microplastic particle size sorting and capturing module, wherein: the digestion processing module comprises a sample chamber, a digestion liquid chamber and a sample digestion chamber, the sample chamber and the digestion chamber are merged and connected to the sample digestion chamber; the microplastic particle size sorting and capturing module comprises an enhanced liquid chamber, a particle size sorting area, an extrusion microfluidic channel, a gradient particle size separation area and a waste liquid chamber, the enhanced liquid chamber and the sample digestion chamber are merged and connected to the particle size sorting area, the particle size sorting area is connected to the gradient particle size separation area through an extrusion microfluidic channel with a necking structure, and the gradient particle size separation area is connected to the waste liquid chamber; n+1 screening partitions are arranged in the particle size sorting area through n reverse angle separation arrays, and the corresponding gradient particle size separation area is arranged with n+1 centrifugal force separation chambers, and is connected to the n+1 screening partitions one by one through n+1 extrusion microfluidic channels, and n is a natural number greater than or equal to 2. By adopting the above scheme, the design of the device makes the entire operation process integrated and automated. It utilizes centrifugal microfluidics technology, the centrifugal force generated by high-speed rotation, and the coupling of centrifugal force and Coriolis force to achieve circumferential reverse motion of microplastics in the reverse angle array during the microplastic separation process, thereby achieving non-clogging particle size range division of microplastics. Combined with two-stage separation coupling, it can effectively separate microplastic particles of different particle sizes, especially for microplastics smaller than 100 microns. It has good separation efficiency and can complete the digestion and sorting of microplastic particles in a shorter time. The chip clogging rate is small, the recovery rate of microplastics is high, and the cumulative error is small, which greatly improves the analysis efficiency and accuracy. It is an efficient and convenient solution suitable for many fields such as environmental monitoring and research.

[0009] Optionally, the digestion processing module also includes a sample inlet and a sample chamber air outlet connected to the sample chamber, a digestion liquid inlet and a digestion liquid chamber air outlet connected to the digestion liquid chamber, and a digestion chamber air outlet connected to the sample digestion chamber; the microplastic particle size sorting and capturing module also includes an enhancement liquid inlet and an enhancement liquid chamber air outlet connected to the enhancement liquid chamber, and a waste liquid chamber air outlet connected to the waste liquid chamber. In this way, by adding these optional components, the operation of the digestion processing module and the microplastic particle size sorting and capturing module becomes more flexible and efficient. The setting of these inlets and outlets can not only improve the loading and processing efficiency of the sample, but also effectively control the gas flow during the digestion and sorting process to ensure the stability of the reaction conditions. In addition, users can conveniently adjust the types and concentrations of digestion liquids and enhancement liquids according to different experimental requirements to further optimize the digestion and sorting effects of microplastics.

[0010] Optionally, the array spacings of the n reverse angle separation arrays are reduced in sequence, i.e., D1>D2>Dn, and the array spacing of the first reverse angle separation array is the equivalent diameter D of the maximum volume of microplastics to be separated. MThe angle between the array and the liquid flow direction is determined by subtracting 5 to 20 μm, and the array spacing reduction value between two adjacent reverse angle separation arrays is between 5 and 20 μm. The openings of each reverse angle separation array have a reverse slope with an angle of 95 to 130° with the centrifugal force direction of the centrifugal microfluidic chip. That is, the reverse slopes in the opening direction of each reverse angle separation array are at an angle of 95° to 130° with the centrifugal force direction of the centrifugal microfluidic chip, or at an angle with the liquid flow direction. In this way, by using the characteristic that the angle between the array angle and the liquid flow direction is greater than 90°, and utilizing the coupling of centrifugal force and Coriolis force, the microplastics can produce circumferential reverse motion when arrayed, and the microplastics smaller than the reverse angle array spacing enter the next level, while the microplastics larger than the reverse angle array spacing enter the current level of sorting with the water flow. The reverse angle design prevents clogging at the array, and the step-by-step reduction spacing design enables the reverse angle separation array to more accurately sort microplastics of different particle sizes, thereby improving the efficiency and accuracy of sorting. The design of the angle between the reverse angle separation array and the chip diameter helps to optimize the flow path, reduce dead zones in liquid flow, avoid blockages, and ensure that each reverse angle separation array can fully exert its screening function, thereby improving the overall sorting effect. The problem of small sorting particle size range in a single separation chamber has been solved. To increase the separation range, one can only increase the separation chamber or increase the separation speed. When the separation chamber is too large or the speed is too high, and the liquid flow rate in the chip is too high, eddies will be generated in the separation chamber, reducing the sorting efficiency. By dividing the particle size range and performing graded separation, the problem of eddies being generated in the separation chamber and reducing the sorting efficiency when the separation chamber is too large or the speed is too high, and the liquid flow rate in the chip is too high has been solved, and the particle size range of a single chip in sorting microplastics has been increased.

[0011] Optionally, the number n of reverse-angle separation arrays is set to 3, which are composed of reverse-angle separation array I, reverse-angle separation array II, and reverse-angle separation array III, whose array spacing is successively reduced and arranged in the radial direction of the centrifugal microfluidic chip as gradually outward away from the centrifugal axis, and the array spacing can be changed according to the particle size requirements of microplastic separation, such as the array spacing of reverse-angle separation array I, reverse-angle separation array II, and reverse-angle separation array III are 40μm, 30μm, and 20μm, respectively; the corresponding number n+1 of centrifugal separation chambers is set to 4, which is composed of centrifugal separation chamber I, centrifugal separation chamber II, centrifugal separation chamber III, and centrifugal separation chamber IV, whose microplastic particle size separation is gradually reduced and arranged in the radial direction of the centrifugal microfluidic chip as gradually outward away from the centrifugal axis.

[0012] Optionally, the length-to-width ratio of the n+1 centrifugal separation chambers is between 0.5 and 0.75, and the length of each is the equivalent diameter D of the maximum volume of the microplastics to be separated. MThe length and width of centrifugal separation chamber I, centrifugal separation chamber II, centrifugal separation chamber III, and centrifugal separation chamber IV are 3900μm*800μm, 3700μm*700μm, 3600μm*600μm, and 3450μm*600μm, respectively. In this way, through the design of centrifugal separation chambers with gradually increasing sizes, microplastic particles of different particle sizes can be effectively separated to ensure the maximum efficiency of each separation chamber. This combination of layout and design allows microplastic particles to be better separated and identified, improving the accuracy and reliability of subsequent analysis.

[0013] Optionally, the inner bottoms of the n+1 centrifugal separation chambers are all provided with sawtooth grooves for paving the microplastic particle sizes step by step. The sawtooth groove design enhances the particle retention effect, helps to effectively separate and capture microplastics, and reduces the overlap of particles during the separation process.

[0014] Optionally, the length-to-width ratio of the sample chamber, the digestion fluid chamber, and the enhancement fluid chamber is between 1.2 and 1.6, and the length of each is the equivalent diameter D of the maximum volume of the microplastics to be separated. M 120 to 160 times of the maximum volume of microplastics to be separated; such as length>4000μm, width>3500μm; the widths of the microchannels connected to the sample chamber, digestion chamber, enhancement chamber, sample digestion chamber and waste chamber are equal, and the widths of each are the equivalent diameter D of the maximum volume of microplastics to be separated M The microchannel is 3.5 to 4 times of the original size and between 100 and 300 μm, such as 200 μm; the microchannel is made of PDMS material and is made by soft lithography casting process. In this way, the appropriate microchannel size ensures the rapid flow of samples and digestive fluids and optimizes the working efficiency of the entire system. The use of PDMS material ensures the biocompatibility of the system and is suitable for microplastic detection involving biological samples. The application of soft lithography technology ensures the high precision and consistency of the microchannel structure, reduces the variability in the manufacturing process, and improves the reliability of the equipment.

[0015] Optionally, the microchannel includes a meandering mixed microfluidic channel for connecting the sample chamber with the digestion chamber after the sample chamber merges with the digestion chamber, and a U-shaped siphon microfluidic channel for connecting the gradient particle size separation zone with the waste liquid chamber. The corresponding siphon microfluidic channels are arranged in n+1 numbers and are connected one-to-one with the n+1 centrifugal separation chambers. In this way, the meandering mixed microfluidic channel and the U-shaped siphon microfluidic channel jointly optimize the sample processing process and improve the efficiency and accuracy of the analysis. The corresponding number design of the siphon microfluidic channels enables the system to flexibly respond to different experimental requirements and is suitable for various types of microplastic analysis.

[0016] Optionally, the microplastic particle sorting and detection device also includes a portable Raman spectrometer for detecting microplastics of different particle sizes and compositions in each centrifugal separation chamber in the gradient particle size separation zone. Combined with Raman spectroscopy and other technologies, the sorted microplastic particles can be quickly detected and characterized in a short time, thereby improving the efficiency of the experiment. The device integrates the sorting and detection processes of microplastics, simplifies the operation process, and improves the efficiency of the overall analysis process.

[0017] The present invention also provides a detection method using the above-mentioned non-clogging multi-stage microplastic particle grading and sorting device based on a centrifugal microfluidic chip, comprising the following steps:

[0018] S1: Prepare the sample solution of microplastic particles to be separated, digestion reagent, and SERS enhancement reagent;

[0019] S2: Use a syringe to fill the sample chamber with a set amount of the sample solution of the microplastic particles to be separated, inject a set amount of the digestion reagent into the digestion liquid chamber, and inject a set amount of the enhancement reagent into the enhancement liquid chamber;

[0020] S3: Use tape to seal the waste liquid chamber outlet, and centrifuge the centrifugal microfluidic chip. After the separated microplastic particle sample solution is mixed with the digestion reagent, it enters the digestion liquid chamber and completes sufficient microplastic digestion treatment, and then the waste liquid chamber outlet is opened;

[0021] S4: centrifuging the centrifugal microfluidic chip again, and the digested sample flow in the digestion liquid chamber is mixed with the enhancement reagent in the enhancement liquid chamber to form a mixed solution;

[0022] S5: The mixed liquid under centrifugal force enters the particle size sorting area, and screens the microplastics of different particle sizes in the mixed liquid through n reverse angle separation arrays to complete the initial screening and separation of microplastic particles. Then, the n+1 screening partitions formed in the particle size sorting area correspond to each other through the extrusion microfluidic channels respectively flowing into the n+1 centrifugal separation chambers in the gradient particle size separation area, so that the microplastic particles after the initial screening are again flattened and separated step by step in their respective centrifugal separation chambers according to the different particle size densities under the action of multi-force coupling; the waste liquid formed in each centrifugal separation chamber enters the waste liquid chamber through the corresponding siphon microfluidic channels respectively;

[0023] S6: A portable Raman spectrometer focuses on the microplastics in each centrifugal separation chamber in the gradient particle size separation zone to obtain Raman characteristic spectra of different microplastic particle sizes to complete the detection.

[0024] In simple terms, after the microplastics are digested and surface impurities are removed in the digestion chamber, the particle size sorting area can produce circumferential reverse motion under the coupling of centrifugal force and Coriolis force, so that through the reverse angle array, the particle size of the microplastics can be screened and separated without clogging according to the particle size of the microplastics, and the microplastics are subjected to centrifugal force F in the centrifugal microfluid in the gradient particle size separation area. C , Coriolis force F Co and Euler F E The multi-force coupling composed of equal volume force, drag force, buoyancy and other interaction forces between liquid and microplastic particles causes the microplastic particles to settle to the outermost side of their respective centrifugal separation chambers under the combined action of drag force, centrifugal force, buoyancy and other forces, and microplastic particles of different densities are eventually distributed in different areas or positions in space through movement; the remaining waste liquid and impurities are brought into the waste liquid chamber by the water flow through the siphon microfluidic channel; finally, the microplastics settled in each centrifugal separation chamber in the gradient particle size separation area are detected by a portable Raman spectrometer, and the corresponding Raman spectrum is obtained through the SERS enhancement brought by silver nanosol, thereby realizing the rapid sorting and detection of microplastics of different particle sizes and compositions.

[0025] The beneficial effects of the present invention are:

[0026] 1. Pre-treatment and characterization integration: This solution uses SERS technology combined with centrifugal microfluidics to combine the digestion of microplastics, separation of different components and characterization steps to achieve an integrated technology for rapid processing and characterization of microplastics in the environment. At the same time, a portable Raman spectrometer is used to characterize the separated microplastics, without the need to label the microplastic particles, reducing cumbersome processing steps and enabling rapid detection of microplastics on site.

[0027] 2. Non-clogging microplastic particle size range classification: Different traditional arrays are used to screen particles. This chip uses a reverse-angle array with an angle greater than 90° (95°-130°) to the water flow direction. Under the action of centrifugal force and Coriolis force, microplastics produce circumferential reverse motion as the liquid flows, thereby achieving non-clogging particle size range classification of microplastics through the reverse-angle array.

[0028] 3. Improve the particle size range of chip sorting: Different from the chip with a single separation chamber, it can only sort the particle size of microplastics within a specific range. If you want to improve the particle size sorting range of the single separation chamber chip, you can only increase the length of the separation chamber or increase the rotation speed during separation, which will cause eddy currents in the separation chamber, thereby reducing the separation efficiency. Multi-grade microplastics use particle size classification chambers to divide the particle size range of microplastics. Microplastics of different particle size ranges enter separation chambers with different centrifugal radii for particle size separation. Microplastics of different particle size ranges can produce fine separation at different centrifugal radii, and ensure that no eddy currents that are sufficient to affect the separation effect are generated in the separation chamber, solving the defect that a single chip cannot sort microplastic particles in a larger particle size range.

[0029] 4. Rapid sorting: Using centrifugal microfluidic technology, without the need for an external pump, the centrifugal force, Coriolis force, Euler force and other volume forces, drag force, buoyancy and other combined forces of microplastic particles in the microfluidic channel are utilized, and the microplastics of different particle sizes and compositions are separated in a short time according to the density differences caused by different types of microplastics. Different from the traditional screening and filtration method, the filtration effect is greatly affected by the material of the filter membrane, the pore size or mesh size has limitations on the size of the separated microplastics, the loss rate of microplastics is high during sorting, the error is large, and different types of microplastics cannot be separated. This device can quickly and effectively separate microplastic particles of different sizes and types through the two-stage separation coupling linkage.

[0030] In general, this technical solution combines SERS technology and centrifugal microfluidic technology to carry out rapid pre-treatment, screening, separation and detection of microplastics in the environment, realizing an integrated technology for rapid processing and characterization of microplastics in the environment. It can realize on-site rapid detection of microplastics in the environment, and has important application value and broad development prospects in the field of sorting and detection of microplastic particles.

[0031] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0033] Figure 1 This is a schematic diagram of the structure of the centrifugal microfluidic non-clogging multi-stage microplastic particle classification and sorting device of the present invention;

[0034] Figure 2 for Figure 1Schematic diagram of the structure of a single analysis unit in;

[0035] Figure 3 for Figure 2 A magnified schematic diagram of part A in FIG.

[0036] Figure 4 for Figure 2 A magnified schematic diagram of part B in FIG.

[0037] Figure numerals: 0-centrifugal axis, 1-analysis unit, 2-centrifugal microfluidic chip; 10-microplastic particle size sorting and capture module, 20-digestion treatment module; 101-enhanced liquid inlet, 102-enhanced liquid chamber, 103-enhanced liquid chamber outlet, 104-particle size sorting area, 105-extrusion microfluidic channel, 106-gradient particle size separation area, 107-siphon microfluidic channel, 108-waste liquid chamber, 109-waste liquid chamber outlet; 1021-capillary regulating valve; 1041-reverse angle separation array I, 10 42-reverse angle separation array II, 1043-reverse angle separation array III; 1061-centrifugal force separation chamber I, 1062-centrifugal force separation chamber II, 1063-centrifugal force separation chamber III, 1064-centrifugal force separation chamber IV, 1065-sawtooth groove; 201-sample inlet, 202-sample chamber, 203-sample chamber air outlet, 204-digestion fluid inlet, 205-digestion fluid chamber, 206-digestion fluid chamber air outlet, 207-digestion chamber air outlet, 208-mixing microfluidic channel, 209-sample digestion chamber. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with specific implementation methods. The accompanying drawings are only used for exemplary descriptions and are only schematic diagrams, not actual drawings, and cannot be understood as limiting this patent; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted.

[0039] like Figure 1-4As shown, the present invention mentions a centrifugal microfluidic non-clogging multi-stage microplastic particle grading and sorting device, including one or more analysis units 1 arranged around the centrifugal axis 0 on the centrifugal microfluidic chip 2, and the analysis unit 1 is composed of a digestion processing module 20 and a microplastic particle size sorting and capturing module 10, wherein: the digestion processing module is a microplastic digestion processing module, in which the sample is digested and processed, so that the microplastic particles can be effectively released and prepared for subsequent sorting, including a sample chamber 202, a digestion liquid chamber 205 and a sample The digestion chamber 209, the sample chamber 202 and the digestion liquid chamber 205 merge and are connected to the sample digestion chamber 209; the microplastic particle size sorting and capturing module 10 is a two-stage linkage sorting and capturing module based on the microplastic size and density difference sorting, including an enhanced liquid chamber 102, a particle size sorting area 104, an extruded microfluidic channel 105, a gradient particle size separation area 106 and a waste liquid chamber 108. The enhanced liquid chamber 102 provides the necessary enhanced liquid to improve the sorting efficiency, and merges with the sample digestion chamber 209 and is connected to the particle size sorting area 104. The particle size sorting area 104 is connected to the gradient particle size separation area 106 through an extruded microfluidic channel 105 with a necking structure. After the mixed liquid passes through the extruded microfluidic channel 105 and is subjected to the centrifugal force, the microplastic particles are squeezed to the outermost side of the channel for arrangement, which can effectively control the flow of the fluid and further enhance the effect of particle size sorting. The gradient particle size separation area 106 separates different microplastic particles according to the differences in particle size and density, and is connected to the waste liquid chamber 108 to collect the sorted particles. The waste liquid generated during the process can be kept clean by the system; the particle size sorting area 104 is provided with n+1 screening partitions through n reverse-angle separation arrays, and the corresponding gradient particle size separation area 106 is provided with n+1 centrifugal separation chambers, and is connected to the n+1 screening partitions one by one through n+1 extrusion microfluidic channels 105, and n is a natural number greater than or equal to 2. Such a design can achieve efficient sorting of microplastic particles of various different particle sizes, improve the sorting range of microplastic particle sizes of a single chip, and enhance the flexibility and adaptability of detection. The length and width of the sample chamber 202, the digestion liquid chamber 205 and the enhancement liquid chamber 102 are: 4200μm*3600μm. This size design ensures sufficient volume to accommodate samples and digestion liquids, and also provides convenience for subsequent processing and sorting. The length and width can be increased according to the size of the processing volume. The reference length is 20 times the width of the microchannel; the height and width of the microchannel connected to the sample chamber 202, the digestion liquid chamber 205, the enhancement liquid chamber 102, the sample digestion chamber 209 and the waste liquid chamber 108 are: 200μm (300μm>microchannel height and width>100μm), and the height and width of the microchannel are the equivalent diameter D of the maximum volume of the microplastics to be separated M3.5 to 4 times of the diameter of the microchannel. This size can ensure smooth flow of fluid in the microchannel, reduce flow resistance, and ensure rapid delivery and effective mixing of liquids. The microchannel is made of PDMS material and is made of soft photolithography casting process, that is, it is made of polydimethylsiloxane (PDMS) material. PDMS has good biocompatibility, transparency and excellent elasticity, and is suitable for microfluidic devices. Manufacturing process: The microchannel is made of soft photolithography casting process. This process can achieve high-precision microstructure manufacturing, and at the same time has good repeatability and stability, which is suitable for large-scale production such as microchannels. The microchannel includes a mixing microfluidic channel 208 which is connected to the sample digestion chamber 209 after the sample chamber 202 and the digestion liquid chamber 205 are merged and is in a zigzag shape, and a siphon microfluidic channel 107 which is connected to the gradient particle size separation area 106 and the waste liquid chamber 108 and is in a U-shape. The tortuous channel shape can increase the shear force of the fluid, promote the uniform mixing of the sample and the digestion liquid, and improve the efficiency of the digestion process. The tortuous design helps to reduce the dead zone of the fluid in the channel and ensure the uniform flow of the sample. Therefore, this tortuous design helps to increase the mixing effect of the fluid and ensure that the sample and the digestion liquid are fully contacted and reacted before entering the sample digestion chamber; and the U-shaped channel design helps to control the flow path of the fluid, while avoiding fluid backflow and ensuring the effective discharge of the waste liquid. By corresponding to different centrifugal separation chambers, it can achieve efficient separation and capture of microplastics of different particle sizes, thereby effectively guiding the separated liquid to flow to the waste liquid chamber, ensuring the efficient operation of the system. The corresponding siphon microfluidic channels 107 are set to n+1 and connected to n+1 centrifugal separation chambers one by one. This design ensures that the separation products of each centrifugal separation chamber can be discharged smoothly, thereby achieving efficient sorting and processing. The microplastic particle sorting and detection device also includes a portable Raman spectrometer (not shown) for detecting the microplastics of different particle sizes and components on the outermost side of each centrifugal separation chamber in the gradient particle size separation zone 106. It is an existing conventional device, and the wavelength used by the portable Raman spectrometer is 785nm, the excitation power is 25mW, and the excitation time is 5s. The portable Raman spectrometer can detect the particle size and composition of microplastic particles in different centrifugal separation chambers in real time during the sorting and capture of microplastic particles. By using Raman spectroscopy technology, the chemical composition of microplastics can be accurately analyzed, and information about the type of microplastics can be provided, thereby helping researchers understand the source and environmental impact of microplastics.

[0040] In this embodiment, the sample inlet 201 is connected to the sample chamber 202, allowing the user to conveniently introduce the water sample to be processed into the sample chamber 202, that is, through the sample inlet 201, the sample can be loaded quickly and effectively, reducing the time of sample processing; and the sample chamber air outlet 203 is connected to the sample chamber 202. During the process of injecting the sample into the sample chamber 202, the gas in the sample chamber can be discharged through the sample chamber air outlet 203 to keep the pressure in the sample chamber 202 stable and avoid gas accumulation affecting subsequent steps; and the digestion liquid inlet 204 is connected to the digestion liquid chamber 205, which is convenient for adding digestion liquid to the digestion liquid chamber, and the type and concentration of the digestion liquid can be adjusted as needed to meet the digestion requirements of microplastics in different water samples and improve the digestion effect; and the digestion liquid chamber air outlet 206 is connected to the digestion liquid chamber 205, so that during the digestion process, the gas in the digestion liquid chamber can be discharged in time, ensuring smooth gas exchange during the digestion process and preventing gas accumulation from causing excessive pressure; and the digestion chamber air outlet 207 is directly connected to the sample digestion chamber 209 , so that after digestion is completed, the gas in the sample digestion chamber 209 can be discharged, maintain the normal pressure of the system, and prepare for the subsequent sorting process; and the enhancement liquid inlet 101 is connected to the enhancement liquid chamber 102, so that the user can easily add enhancement liquid to the enhancement liquid chamber to improve the fluid dynamics during the sorting process, and the user can select the appropriate enhancement liquid type and concentration according to different experimental requirements, so as to optimize the sorting effect of microplastic particles; and the enhancement liquid chamber outlet 103 is directly connected to the enhancement liquid chamber 102, so that the gas in the enhancement liquid chamber 102 can be discharged in time. During the sorting process, the gas in the enhancement liquid chamber can be discharged through the outlet, maintaining the flow stability of the liquid, and reducing the interference of bubbles on the sorting results, so as to ensure the uniform distribution of the enhancement liquid in the sorting area and improve the sensitivity of the sorting; and the waste liquid chamber outlet 109 is connected to the waste liquid chamber 108, so that the gas in the waste liquid chamber 108 can be discharged in time, maintaining the fluidity and smooth discharge of the waste liquid, and avoiding the pressure increase caused by the accumulation of waste liquid. It can also prevent laboratory environmental pollution caused by gas accumulation.

[0041] Specifically, the number n of the reverse angle separation arrays is set to 3, which are composed of reverse angle separation array I 1041, reverse angle separation array II 1042, and reverse angle separation array III 1043, whose microplastic particle size screening size is gradually reduced, so as to achieve efficient particle size sorting, and the reverse angle separation array I 1041, reverse angle separation array II 1042, and reverse angle separation array III 1043 are arranged equidistantly in the particle size sorting area 104 parallel to the length of the particle size sorting area 104, and the array spacings are 40 μm, 30 μm, and 20 μm respectively, so as to screen larger sizes and medium sizes, respectively. The reverse slope (array gap opening direction angle) of each reverse angle separation array is opposite to the centrifugal force direction of the centrifugal microfluidic chip 2, and the angle is greater than 90°, preferably 95° to 130°. This angle design can optimize fluid dynamics, and through the reverse angle array with an angle greater than 90° (95°-130°) with the water flow direction, the microplastics can produce circumferential reverse motion when flowing with the liquid under the action of centrifugal force and Coriolis force, thereby realizing the division of the non-blocking particle size range of microplastics through the reverse angle array. It helps microplastic particles of different particle sizes to be captured and separated more effectively during the flow process, reducing experimental errors, preferably 118°; each reverse angle separation array in the particle size sorting area 104 is composed of hexagonal microcolumns, which helps to maximize the flow efficiency of the fluid and improve the capture ability of particles; and the microcolumn has a lower base length of 110μm, an upper base length of 150μm, a height of 100μm, and a hypotenuse length of 54μm. This setup can flexibly adjust the number and spacing of the reverse-angle separation arrays according to different experimental requirements to meet the analysis requirements of microplastics in different types of water samples. The design of the hexagonal microcolumns allows the fluid to form a good flow pattern during the sorting process, reducing the flow dead zone and ensuring that microplastic particles can be effectively captured and separated. The larger upper base design increases the contact area with the fluid, which helps to enhance the interaction force between microplastic particles and microcolumns, thereby improving the sensitivity of sorting. The moderate height and bevel design can effectively extend the residence time of microplastic particles between microcolumns, allowing particles of different particle sizes to be better screened.

[0042] The number n+1 of the corresponding centrifugal separation chambers is set to 4, which are composed of centrifugal separation chamber I 1061, centrifugal separation chamber II 1062, centrifugal separation chamber III 1063, and centrifugal separation chamber IV 1064, each of which is designed to separate microplastic particles of different particle sizes, and the gradual reduction helps to effectively capture and separate particles of different sizes. The length and height of centrifugal separation chamber I 1061, centrifugal separation chamber II 1062, centrifugal separation chamber III 1063, and centrifugal separation chamber IV 1064 are: 3900μm*800μm, 3700μm*700μm, 3600μm*600μm, 345 0μm*600μm, to capture microplastics of larger particle size, medium particle size, smaller particle size and smallest particle size respectively; the outer capture interval intervals of centrifugal separation chamber Ⅰ1061, centrifugal separation chamber Ⅱ1062, centrifugal separation chamber Ⅲ1063 and centrifugal separation chamber Ⅳ1064 are 200μm, 180μm, 160μm and 140μm respectively, and the radius of the capture arc in the interval is 54μm, 44μm, 34μm and 24μm respectively. By setting different capture interval intervals and arc radius, microplastic particles of different particle sizes can be better captured and separated, solving the problem that microplastics with a larger particle size range cannot be sorted in a single chip. The larger capture interval interval provides enough space for particles with larger particle sizes, while the smaller capture arc radius can effectively capture particles with smaller particle sizes, ensuring that no eddy currents that are sufficient to affect the sorting effect are generated in the centrifugal separation chamber. Centrifugal separation chamber I 1061, centrifugal separation chamber II 1062, centrifugal separation chamber III 1063, and centrifugal separation chamber IV 1064 are arranged in the radial direction of the centrifugal microfluidic chip 2 to gradually deviate from the centrifugal axis 0. Such a layout can utilize the difference in centrifugal force so that microplastics of different particle sizes can be effectively separated during the centrifugation process. The corresponding four siphon microfluidic channels 107 are respectively connected to the centrifugal separation chamber I 1061, the centrifugal separation chamber II 1062, the centrifugal separation chamber III 1063, and the centrifugal separation chamber IV 1064 with a diameter of 150 μm, 140 μm, 130 μm, and 120 μm. The design of the siphon microfluidic channel takes into account the diameter of the channel, which can optimize the flow velocity of the fluid and ensure the flow state of the microplastic particles when passing through the channel, so as to achieve efficient sorting and transmission.

[0043] In another embodiment, the inner bottom of each centrifugal separation chamber is provided with a sawtooth groove 1065 for tiling the microplastic particle size step by step. The design of the sawtooth groove 1065 can further increase the contact area between the microplastic particles and the bottom, and promote the separation and capture of the particles. At the same time, the presence of the sawtooth groove can help the microplastic particles to form an orderly arrangement in the separation chamber, which is convenient for subsequent detection and analysis. Further, the outer capture sawtooth grooves 1065 of the centrifugal separation chamber I 1061, the centrifugal separation chamber II 1062, the centrifugal separation chamber III 1063, and the centrifugal separation chamber IV 1064 are spaced 200 μm, 180 μm, 160 μm, and 140 μm, respectively, and the radius of the capture arc in a single interval is 54 μm, 44 μm, 34 μm, and 24 μm, respectively. Different arc radii are set according to the different spacings of the reverse angle array. By setting different capture intervals and arc radii, microplastic particles of different particle sizes can be better captured and separated. A larger capture interval provides sufficient space for larger particles, while a smaller capture arc radius can effectively capture smaller particles.

[0044] The present invention also provides a detection method using the above-mentioned non-clogging multi-stage microplastic particle grading and sorting device based on a centrifugal microfluidic chip, comprising the following steps:

[0045] S1: Prepare a sample solution of microplastic particles to be separated, wherein the particle size of the microplastic is selected to be 10-100 μm, a digestion reagent (Fenton reagent, pH=5), and a SERS enhancement reagent (silver nanosol, prepared by trisodium citrate reduction method);

[0046] S2: Use a syringe to fill the sample chamber 202 with a set amount of the sample solution of the microplastic particles to be separated through the sample inlet 201, and inject a set amount of the digestion reagent into the digestion liquid chamber 205 through the digestion liquid inlet 204, and inject a set amount of the enhancement reagent into the enhancement liquid chamber 102 through the enhancement liquid inlet 101;

[0047] S3: Use tape (pressure valve) to seal the waste liquid chamber outlet 109, and centrifuge the centrifugal microfluidic chip 2 at 500r / min for 10s. After the microplastic particle sample solution to be separated and the digestion reagent are fully mixed through the mixing microfluidic channel 208, the tape on the waste liquid chamber outlet 109 is used to maintain the pressure of the entire system to complete the microplastic digestion treatment in the digestion liquid chamber 205, and the mixed solution cannot continue to flow downward under the action of centrifugal force. Then wait for the centrifugation to be temporarily stopped and tear off the tape (pressure valve) to open the waste liquid chamber outlet 109;

[0048] S4: centrifuging the centrifugal microfluidic chip 2 at 3000 r / min, and the digested sample flow in the digestion liquid chamber 205 is mixed with the enhancement reagent released by the capillary regulating valve 1021 in the enhancement liquid chamber 102 to form a mixed solution;

[0049] S5: The mixed liquid under centrifugal force enters the particle size sorting zone 104, and the microplastics in the mixed liquid are screened by the reverse angle separation array Ⅰ1041, the reverse angle separation array Ⅱ1042, and the reverse angle separation array Ⅲ1043 to complete the non-blocking primary screening separation of microplastic particles. Then, the extruded microfluidic channels 105 corresponding to the four screening partitions formed in the particle size sorting zone 104 flow into the centrifugal force separation chamber Ⅰ1061, the centrifugal force separation chamber Ⅱ1062, the centrifugal force separation chamber Ⅲ1063, and the centrifugal force separation chamber Ⅳ1064 in the gradient particle size separation zone 106, respectively, so as to subject the microplastic particles after the primary screening to the centrifugal force F C , Coriolis force F Co and Euler F E The three body forces and the coupling between them and the liquid: drag force and buoyancy. According to the equations of the body force and the drag force, the relative velocity between the particle and the liquid is related to the particle size, density and centrifugal acceleration: u = F s / 6πμr=2r 2 (ρ p -ρ f )ω 2 R / 9μ. In the formula, u is the relative movement speed of particles in water, F s represents the combined force of centrifugal force and buoyancy on the particle, r is the radius of the particle, ρ p is the density of microplastics, ρ f is the density of the liquid, R is the centrifugal radius, μ is the viscosity coefficient of the liquid, and ω is the rotation speed of the centrifugal microfluidic chip. Under the multi-force coupling, the microplastics with different particle sizes and densities are spread out and separated again step by step according to the difference in centrifugal force and fluid resistance on the sawtooth grooves 1065 inside and outside the respective centrifugal separation chambers; the waste liquid formed in each centrifugal separation chamber enters the waste liquid chamber 108 through the corresponding siphon microfluidic channel 107;

[0050] S6: A portable Raman spectrometer is used to focus on the microplastics on the outermost sawtooth grooves 1065 in each centrifugal separation chamber in the gradient particle size separation zone 106, and excites them with a wavelength of 785nm, an excitation power of 25mW, and an excitation time of 5s to obtain the Raman characteristic spectra of microplastics with different particle sizes and compositions to complete the detection.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A centrifugal microfluidic non-clogging multi-stage microplastic particle classification and sorting device, comprising one or more analysis units (1) arranged around a centrifugal axis (0) on the centrifugal microfluidic chip (2), characterized in that: The analysis unit (1) is composed of a digestion processing module (20) and a microplastic particle size sorting and capturing module (10), wherein: The digestion processing module comprises a sample chamber (202), a digestion liquid chamber (205) and a sample digestion chamber (209), wherein the sample chamber (202) and the digestion liquid chamber (205) are connected to the sample digestion chamber (209); The microplastic particle size sorting and capturing module (10) comprises an enhanced liquid chamber (102), a particle size sorting zone (104), an extruded microfluidic channel (105), a gradient particle size separation zone (106) and a waste liquid chamber (108); the enhanced liquid chamber (102) merges with the sample digestion chamber (209) and is connected to the particle size sorting zone (104); the particle size sorting zone (104) is connected to the gradient particle size separation zone (106) via the extruded microfluidic channel (105) having a necking structure; and the gradient particle size separation zone (106) is connected to the waste liquid chamber (108); The particle size sorting area (104) is provided with n+1 screening partitions through n reverse angle separation arrays, and the corresponding gradient particle size separation area (106) is provided with n+1 centrifugal separation chambers, and is connected to the n+1 screening partitions in a one-to-one correspondence through n+1 extrusion microfluidic channels (105), where n is a natural number greater than or equal to 2.

2. The centrifugal microfluidic non-clogging multi-stage microplastic particle grading and sorting device according to claim 1 is characterized in that: The digestion processing module (20) also includes a sample inlet (201) and a sample chamber air outlet (203) connected to the sample chamber (202), a digestion liquid inlet (204) and a digestion liquid chamber air outlet (206) connected to the digestion liquid chamber (205), and a digestion chamber air outlet (207) connected to the sample digestion chamber (209); the microplastic particle size sorting and capturing module (10) also includes an enhancement liquid inlet (101) and an enhancement liquid chamber air outlet (103) connected to the enhancement liquid chamber (102), and a waste liquid chamber air outlet (109) connected to the waste liquid chamber (108).

3. The centrifugal microfluidic non-clogging multi-stage microplastic particle grading and sorting device according to claim 1 is characterized in that: The array spacing of the n anti-angle separation arrays is reduced successively, that is, D1>D2>D n , and the array spacing of the first reverse angle separation array is determined by the equivalent diameter of the maximum volume of the microplastics to be separated minus 5 to 20 μm, and the array spacing reduction value between two adjacent reverse angle separation arrays is between 5 and 20 μm, and the openings of each reverse angle separation array have a reverse slope that is at an angle of 95 to 130° with the centrifugal force direction of the centrifugal microfluidic chip (2).

4. The centrifugal microfluidic non-clogging multi-stage microplastic particle grading and sorting device according to claim 3 is characterized in that: The number n of the reverse angle separation arrays is set to 3, and is composed of reverse angle separation array I (1041), reverse angle separation array II (1042), and reverse angle separation array III (1043), whose array spacings are successively reduced and arranged in the radial direction of the centrifugal microfluidic chip (2) to gradually move outward away from the centrifugal axis (0); the number n+1 of the centrifugal separation chambers is correspondingly set to 4, and is composed of centrifugal separation chamber I (1061), centrifugal separation chamber II (1062), centrifugal separation chamber III (1063), and centrifugal separation chamber IV (104), whose microplastic particle size separation is gradually reduced and arranged in the radial direction of the centrifugal microfluidic chip (2) to gradually move outward away from the centrifugal axis (0).

5. The centrifugal microfluidic non-clogging multi-stage microplastic particle grading and sorting device according to claim 1 is characterized in that: The length-to-width ratio of the n+1 centrifugal separation chambers is between 0.5 and 0.75, and the length of each is 60 to 80 times the equivalent diameter of the maximum volume of microplastics to be separated.

6. The centrifugal microfluidic non-clogging multi-stage microplastic particle grading and sorting device according to claim 1 is characterized in that: The inner bottoms of the n+1 centrifugal separation chambers are all provided with sawtooth grooves (1065) for gradually spreading the particle sizes of microplastics.

7. The centrifugal microfluidic non-clogging multi-stage microplastic particle classification and sorting device according to claim 1 is characterized in that: The length-to-width ratio of the sample chamber (202), digestion fluid chamber (205) and enhancement fluid chamber (102) is between 1.2 and 1.6, and the length of each is 120 to 160 times the equivalent diameter of the maximum volume of microplastics to be separated; the widths of the microchannels connected to the sample chamber (202), digestion fluid chamber (205), enhancement fluid chamber (102), sample digestion chamber (209) and waste fluid chamber (108) are equal, and the width of each is 3.5 to 4 times the equivalent diameter of the maximum volume of microplastics to be separated, and is between 100 and 300 μm; the microchannels are made of PDMS material and are manufactured using a soft photolithography casting process.

8. The centrifugal microfluidic non-clogging multi-stage microplastic particle classification and sorting device according to claim 7 is characterized in that: The microchannel includes a mixing microfluidic channel (208) which is connected to the sample digestion chamber (209) after the sample chamber (202) and the digestion fluid chamber (205) merge and is in a zigzag shape, and a siphon microfluidic channel (107) which is connected to the gradient particle size separation area (106) and the waste liquid chamber (108) and is in a U-shape. The corresponding siphon microfluidic channels (107) are arranged in n+1 numbers and are connected to the n+1 centrifugal separation chambers in a one-to-one correspondence.

9. The centrifugal microfluidic non-clogging multi-stage microplastic particle grading and sorting device according to any one of claims 1 to 8, characterized in that: The microplastic particle sorting and detection device also includes a portable Raman spectrometer for detecting microplastics of different particle sizes and compositions in each centrifugal separation chamber in the gradient particle size separation zone (106).

10. A detection method using the centrifugal microfluidic non-clogging multi-stage microplastic particle classification and sorting device as claimed in claim 9, characterized in that: The steps include: S1: Prepare the sample solution of microplastic particles to be separated, digestion reagent, and SERS enhancement reagent; S2: Use a syringe to fill the sample chamber (202) with a set amount of the sample solution of the microplastic particles to be separated, inject a set amount of the digestion reagent into the digestion liquid chamber (205), and inject a set amount of the enhancement reagent into the enhancement liquid chamber (102); S3: Use tape to seal the waste liquid chamber outlet (109), and centrifuge the centrifugal microfluidic chip (2). After the separated microplastic particle sample solution is mixed with the digestion reagent, it enters the digestion liquid chamber (205) and completes sufficient microplastic digestion treatment, and then opens the waste liquid chamber outlet (109); S4: centrifuging the centrifugal microfluidic chip (2) again, and mixing the digested sample flow in the digestion liquid chamber (205) with the enhancement reagent in the enhancement liquid chamber (102) to form a mixed solution; S5: The mixed liquid under centrifugal force enters the particle size sorting zone (104), and the microplastics of different particle sizes in the mixed liquid are screened respectively through n reverse angle separation arrays to complete the initial screening and separation of the microplastic particles. Then, the extrusion microfluidic channels (105) corresponding to the n+1 screening partitions formed in the particle size sorting zone (104) flow into the n+1 centrifugal separation chambers in the gradient particle size separation zone (106) respectively, so that the microplastic particles after the initial screening are again layered and separated step by step in their respective centrifugal separation chambers according to the different particle size densities under the action of multi-force coupling; the waste liquid formed in each centrifugal separation chamber enters the waste liquid chamber (108) through the corresponding siphon microfluidic channels (107); S6: A portable Raman spectrometer is used to focus on the microplastics in each centrifugal separation chamber in the gradient particle size separation zone (106) to obtain Raman characteristic spectra of different microplastic particle sizes to complete the detection.

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