Centrifugal microfluidic non-clogging multi-stage microplastic particle grading and sorting device and detection method

Abstract

This invention discloses a non-clogging, multi-stage microplastic particle grading and sorting device based on centrifugal microfluidics, belonging to the field of microplastic particle analysis technology in aquatic environments. It includes one or more analysis units arranged around the centrifugal axis of a centrifugal microfluidic chip. Each analysis unit consists of a digestion module and a microplastic particle size sorting and capture module. The microplastic particle size sorting and capture module includes an enhanced liquid chamber, a particle size sorting zone, a squeezing microfluidic channel, a gradient particle size separation zone, and a waste liquid chamber. This invention utilizes the coupling of centrifugal force and Coriolis force, along with an anti-angle array, to classify microplastics of different particle size ranges. The angle between the centrifugal force direction and the anti-angle array is greater than 90°, achieving a non-clogging effect on the array, resulting in a high microplastic particle capture rate and small error. Furthermore, centrifugal force is used to achieve fine sorting of microplastics within different particle size ranges based on size, improving the problem of small particle size sorting range for microplastics on a single chip. This invention also discloses a non-clogging, multi-stage microplastic particle detection method based on centrifugal microfluidics, which can rapidly and accurately sort and detect target microplastics of different particle sizes and compositions, offering significant advantages in rapid on-site detection of microplastics.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microplastic particle analysis in water environment, and provides a centrifugal microfluidic non-blocking multi-stage microplastic particle sorting device and detection method. BACKGROUND

[0002] As a new pollutant, microplastics have been found 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 risk problem it brings is also becoming more and more prominent. These microplastics will enter the water, soil and atmosphere in the environment and have potential impact on the environment and ecological system, such as affecting water quality, interfering with the balance of the ecological system, affecting human health, etc.

[0003] Currently, the analysis and research of microplastics focuses on three points: sampling, sample pretreatment and MPs identification. The traditional microplastic separation method is membrane filtration-based filtration separation method, which is limited in the ability to effectively separate micron-sized small particles, has high loss rate of microplastics during separation, large superimposed error, low precision, and the problem of a large number of small particle microplastics below 50 microns being ignored during separation. And there is a phenomenon of secondary pollution in the process of digestion and separation of microplastics, and the operation steps are complicated, time-consuming, and the filter is easy to block.

[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 of relatively large samples (> 10 μm) limits its application. On the other hand, Raman spectroscopy has the advantages of high resolution and easy sample preparation, and can identify particles with a size close to 1 μm. More importantly, this method is also suitable for liquid samples, even at the microscale. Matching Raman spectra with reference spectra is now widely recognized as the gold standard method for identifying microplastics.

[0005] Centrifugal microfluidic technology is one of the microfluidic technologies, which drives the microfluidic chip to rotate at high speed by motor, applies volume force to all media in the microfluidic chip to control the flow and the difference of volume force to affect the movement of particles. It does not need external pressure pump, its control method is also relatively simple than other methods, and multiple microstructures can be arranged in the chip, which has the advantages of parallel high throughput, high efficiency, simple structure, easy control and so on. However, the existing single separation chamber centrifugal microfluidic chip can only realize the rough division of particles with specific particle size and small range, and the single separation chamber centrifugal microfluidic chip cannot realize the sorting of microplastic particles with large particle size range in one step in one chip. To improve the sorting range and sorting accuracy, the length of the separation chamber, the centrifugal radius or the rotation speed must be increased, but these methods are easy to produce vortex in the separation chamber which can affect the sorting effect and reduce the sorting efficiency. SUMMARY

[0006] Therefore, the present application provides a centrifugal microfluidic non-blocking multi-stage microplastic particle grading and sorting device and detection method based on the centrifugal microfluidic technology, which can realize the integrated technology of rapid collection, processing and characterization of water samples, that is, it can realize the large particle size range, non-blocking, small error, rapid, accurate and effective grading, sorting and detection of microplastic particles in water samples.

[0007] To achieve the above purpose, the present application provides the following technical solutions:

[0008] The application provides a centrifugal microfluidic non-blocking multi-stage microplastic particle classification and separation device based on a centrifugal microfluidic chip, which comprises one or more analysis units arranged around a centrifugal shaft on the centrifugal microfluidic chip, and each analysis unit is composed of a digestion processing module and a microplastic particle size separation and capture module. The digestion processing module comprises a sample chamber, a digestion liquid chamber and a sample digestion chamber, and the sample chamber and the digestion chamber are connected to the sample digestion chamber. The microplastic particle size separation and capture module comprises an enhancer liquid chamber, a particle size separation zone, an extrusion microfluidic channel, a gradient particle size separation zone and a waste liquid chamber, the enhancer liquid chamber is connected to the particle size separation zone through the sample digestion chamber, the particle size separation zone is connected to the gradient particle size separation zone through the extrusion microfluidic channel with a neck structure, and the gradient particle size separation zone is connected to the waste liquid chamber. The particle size separation zone is provided with n+1 screening sub-zones through n anti-angle separation arrays, the corresponding gradient particle size separation zone is provided with n+1 centrifugal force separation chambers, and the n+1 centrifugal force separation chambers are connected to the n+1 screening sub-zones in one-to-one correspondence through n+1 extrusion microfluidic channels, and n is a natural number greater than or equal to 2. The device is designed to integrate and automate the entire operation process, utilizes the centrifugal microfluidic technology, uses the centrifugal force generated by high-speed rotation, utilizes the coupling of the centrifugal force and the Coriolis force, and realizes the circumferential reverse movement of the microplastics in the anti-angle array during the microplastic separation process, thereby realizing the non-blocking particle size range division of the microplastics, and combining the two-stage separation coupling, the microplastics with different particle sizes can be effectively separated, especially the microplastics with a particle size less than 100 microns have a good separation efficiency, the digestion and separation of the microplastic particles can be completed in a short time, the chip clogging rate is small, the microplastic recovery rate is high, the cumulative error is small, the analysis efficiency and accuracy are greatly improved, and the device is a high-efficiency and convenient solution, and is suitable for multiple fields such as environmental monitoring and research.

[0009] Optionally, the digestion processing module further comprises a sample inlet and a sample chamber gas outlet in communication with the sample chamber, a digestion liquid inlet and a digestion liquid chamber gas outlet in communication with the digestion liquid chamber, and a digestion chamber gas outlet in communication with the sample digestion chamber. The microplastic particle size separation and capture module further comprises an enhancer liquid inlet and an enhancer liquid chamber gas outlet in communication with the enhancer liquid chamber, and a waste liquid chamber gas outlet in communication with the waste liquid chamber. Thus, by adding these optional components, the operation of the digestion processing module and the microplastic particle size separation and capture module becomes more flexible and efficient. The arrangement of these inlets and outlets not only improves the loading and processing efficiency of the sample, but also effectively controls the gas flow during the digestion and separation process, ensuring the stability of the reaction conditions.

[0010] Optionally, the array spacing of the n anti-angle separation arrays decreases in turn, i.e. MThe array gap between adjacent two anti-angle separation arrays is reduced by 5-20 pm, and the opening of each anti-angle separation array has an anti-inclined surface with an angle of 95-130° with the centrifugal force direction of the centrifugal microfluidic chip. That is, the angle between the opening direction of each anti-angle separation array and the centrifugal force direction of the centrifugal microfluidic chip is 95° to 130°, or the angle with the liquid flow direction. In this way, by the feature that the angle between the array angle and the liquid flow direction is greater than 90°, the coupling of centrifugal force and Coriolis force is utilized to realize the circumferential reverse movement of microplastics in the array, and the microplastics smaller than the anti-angle array gap enter the next stage, and the microplastics larger than the anti-angle array gap enter the current stage with the water flow. The design of the anti-angle makes it impossible to block the array, and the gradually reduced gap design enables the anti-angle separation array to more accurately separate microplastics of different particle sizes, improving the efficiency and accuracy of separation. The design of the angle between the anti-angle separation array and the chip diameter helps to optimize the flow path, reduce the dead zone in the liquid flow, avoid blockage, and ensure that each anti-angle separation array can fully play its screening role, thereby improving the overall separation effect. The problem of small particle size range in a single separation chamber is solved. To increase the separation range, the separation chamber must be enlarged or the separation speed must be increased. However, when the separation chamber is too large or the speed is too high, the liquid flow rate in the chip is too large, and vortexes are generated in the separation chamber, reducing the separation efficiency. By dividing the particle size range and grading separation, the problem of vortexes in the separation chamber when the separation chamber is too large or the speed is too high is solved, and the particle size range of a single chip in separating microplastics is increased.

[0011] Optionally, the number n of anti-angle separation arrays is set to 3, the array gaps are sequentially reduced, and the anti-angle separation array I, the anti-angle separation array II, and the anti-angle separation array III are arranged in the radial direction of the centrifugal microfluidic chip to gradually move away from the centrifugal shaft center. The array gap of the anti-angle separation array I, the anti-angle separation array II, and the anti-angle separation array III is 40 pm, 30 pm, and 20 pm, respectively. The number n+1 of centrifugal force separation chambers is set to 4, the particle size separation of the centrifugal force separation chambers gradually decreases, and the centrifugal force separation chamber I, the centrifugal force separation chamber II, the centrifugal force separation chamber III, and the centrifugal force separation chamber IV are arranged in the radial direction of the centrifugal microfluidic chip to gradually move away from the centrifugal shaft center.

[0012] Optionally, the length-width ratio of the n+1 centrifugal force separation chambers is between 0.5 and 0.75, and the length of each is the maximum volume equivalent diameter D M60-80 times. The length and width of centrifugal separation chamber I, centrifugal separation chamber II, centrifugal separation chamber III, and centrifugal separation chamber IV are 3900 μm*800 μm, 3700 μm*700 μm, 3600 μm*600 μm, and 3450 μm*600 μm, respectively. In this way, through the design of centrifugal separation chambers with gradually increasing centrifugal force, microplastic particles of different particle sizes can be effectively separated, and the efficiency of each separation chamber is maximized. The combination of this layout and design makes it possible to better separate and identify microplastic particles, improving the accuracy and reliability of subsequent analysis.

[0013] Optionally, the inner bottom of the n+1 centrifugal separation chambers is provided with a sawtooth groove for the gradual flattening of microplastic particle sizes. The sawtooth groove design enhances the retention effect of particles, helping to effectively separate and capture microplastics and reducing particle overlap during the separation process.

[0014] Optionally, the length to width ratio of the sample chamber, the digestion liquid chamber, and the enhancement liquid chamber is between 1.2-1.6, and the length of each is 120-160 times the maximum volume equivalent diameter D M of the microplastics to be separated; for example, the length is greater than 4000 μm, and the width is greater than 3500 μm. The width of the microchannels connecting the sample chamber, the digestion liquid chamber, the enhancement liquid chamber, the sample digestion chamber, and the waste liquid chamber is equal, and the width of each is 3.5-4 times the maximum volume equivalent diameter D M of the microplastics to be separated, and is between 100-300 μm, for example, 200 μm. The microchannels are made of PDMS material and are produced using soft lithography casting process. In this way, appropriate microchannel dimensions ensure the rapid flow of samples and digestion liquids, optimizing the overall system efficiency. The use of PDMS material ensures the biocompatibility of the system, making it suitable for microplastic detection involving biological samples. The application of soft lithography technology ensures the high precision and consistency of the microchannel structure, reducing variability during the manufacturing process and improving the reliability of the equipment.

[0015] Optionally, the microchannels include a meandering mixing microfluidic channel connecting the sample chamber and the digestion liquid chamber after they merge and connecting the sample digestion chamber, and a U-shaped siphon microfluidic channel connecting the gradient particle size separation zone and the waste liquid chamber. The corresponding siphon microfluidic channels are set to n+1 and are connected one by one to the n+1 centrifugal separation chambers. In this way, the meandering mixing microfluidic channel and the U-shaped siphon microfluidic channel together optimize the sample processing process, improving the efficiency and accuracy of the analysis. The corresponding number of siphon microfluidic channels allows the system to flexibly respond to different experimental needs and is suitable for various types of microplastic analysis.

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

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

[0018] S1: configure the microplastic particle sample solution to be separated, the digestion reagent, and the SERS enhancement reagent;

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

[0020] S3: use adhesive tape to seal the exhaust port of the waste liquid chamber, and centrifuge the centrifugal microfluidic chip. After the microplastic particle sample solution to be separated is mixed with the digestion reagent, it enters the digestion liquid chamber and completes the digestion of the microplastics. Then, the exhaust port of the waste liquid chamber is opened;

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

[0022] S5: under the centrifugal force, the mixed solution enters the particle size sorting zone and is filtered by the n anti-angle separation array to separate microplastics of different particle sizes in the mixed solution, to complete the initial screening and separation of microplastics. Then, the n+1 extrusion microfluidic channels corresponding to the n+1 screening sub-zones formed in the particle size sorting zone flow into the n+1 centrifugal force separation chambers in the gradient particle size separation zone, respectively, to separate the microplastic particles after initial screening in each centrifugal force separation chamber under the action of multiple forces according to the difference in particle size and density. The waste liquid formed in each centrifugal force separation chamber enters the waste liquid chamber through the corresponding siphon microfluidic channel;

[0023] S6: focus the portable Raman spectrometer on the microplastics in each centrifugal force separation chamber in the gradient particle size separation zone to obtain the Raman characteristic spectrum of different microplastic particle sizes, and complete the detection.

[0024] Simply speaking, after the microplastics are digested to remove surface impurities in the digestion chamber, the circumferential reverse motion is generated in the particle size sorting area under the coupling of centrifugal force and Coriolis force, so that the microplastics are screened and separated without blockage according to the particle size of the microplastics through the reverse angle array, and the microplastics in the centrifugal microfluid are subjected to centrifugal force F C , Coriolis force F Co and Euler force F E , and the interaction forces between the liquid and the microplastic particles such as drag force and buoyancy force, so that the microplastic particles are settled to the outermost side of the respective centrifugal force separation chamber under the action of the resultant force of the drag force, centrifugal force, buoyancy force and the like, and the microplastic particles with different densities are finally distributed in different areas or positions through movement; and the remaining waste liquid and impurities are brought into the waste liquid chamber by the water flow through the siphon microfluid channel; finally, the microplastics settled in the gradient particle size separation area are detected by the portable Raman spectrometer, and the corresponding Raman spectrum is obtained through the SERS enhancement of silver nanosol to realize the rapid sorting and detection of microplastics with different particle sizes and components.

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

[0026] 1. Pretreatment and characterization integration: the present application adopts the method of combining SERS technology and centrifugal microfluidic to combine the digestion treatment, different component separation and characterization steps of microplastics, so as to realize the rapid treatment and characterization integration technology of microplastics in the environment. At the same time, the portable Raman spectrometer is used to characterize the separated microplastics, without labeling the microplastic particles, reducing the cumbersome processing steps, and realizing the on-site rapid detection of microplastics.

[0027] 2. Non-blocking microplastic particle size range division: different traditional arrays are used to screen particles, and the reverse angle array with an angle greater than 90° (95°-130°) between the angle and the direction of water flow is used in the present chip to realize the circumferential reverse motion of the microplastics when the liquid flows, so that the microplastics are screened and separated without blockage through the reverse angle array.

[0028] 3. Improve the chip sorting particle size range: distinguish from single separation chamber chip, only to the microplastic specific range particle size sorting, want to improve the single separation chamber chip particle size sorting range can only through increasing the length of separation chamber or improve the separation speed, and this will lead to the separation chamber produces vortex, thus reducing the separation efficiency. Multistage microplastic utilizes the particle size grading chamber to divide the microplastic particle size range, and the microplastic in different particle size range enters the separation chamber in different centrifugal radius to carry out particle size separation. Different particle size range microplastic in different centrifugal radius can produce fine separation, and it is ensured that vortex which can affect the separation effect does not occur in the separation chamber, solving the defect that single chip cannot sort microplastic particles in a larger particle size range.

[0029] 4. Fast sorting: using centrifugal microfluidic technology, without external connection pump, using the volume force and drag force, buoyancy force and other forces which the microplastic particles receive in the microfluidic channel, and according to the density difference caused by different types of microplastics, the microplastic separation of different particle size and different composition is completed in a short time. Different from the traditional screening and filtering method, the filtering effect is greatly affected by the filter membrane material, the pore size or grid size has size limitation on the separation of microplastics, the loss rate of microplastics is high during sorting, the error is large and different types of microplastics cannot be separated. The two-stage separation coupling linkage of the device can quickly and effectively separate microplastic particles of different sizes and different types.

[0030] In general, the technical scheme combines SERS technology and centrifugal microfluidic technology to quickly pretreat, screen, separate and detect the microplastics in the environment, realizes the rapid processing and characterization integration technology of the microplastics in the environment, can realize the on-site rapid detection of the microplastics in the environment, and has important application value and broad development prospect in the field of microplastic sorting and detection.

[0031] Other advantages, objects and features of the present application will be apparent from the following specification, and such advantages, objects and features will be within the purview of one skilled in the art, based on the teachings herein, or will be learned from practice of the present application. The objects and other advantages of the present application will be realized and attained by the methods and instrumentalities set forth in the following specification. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to make the objects, technical solutions and advantages of the present application clearer, the preferred detailed description of the present application will be combined with the drawings to make the objects, technical solutions and advantages of the present application clearer, wherein:

[0033] Figure 1 The structure diagram of the present application based on centrifugal microfluidic non-blocking multistage microplastic particle grading and sorting device is shown in the figure.

[0034] Figure 2 The structure diagram of the present application based on centrifugal microfluidic non-blocking multistage microplastic particle grading and sorting device is shown in the figure. Figure 1Single analysis unit structure schematic diagram in the figure;

[0035] Figure 3 As Figure 2 A enlarged schematic diagram of part B in the figure;

[0036] Figure 4 As Figure 2 A enlarged schematic diagram of part B in the figure;

[0037] Figure: 0 - centrifugal shaft center, 1 - analysis unit, 2 - centrifugal microfluidic chip; 10 - microplastic particle size sorting and capturing module, 20 - digestion processing module; 101 - enhanced liquid inlet, 102 - enhanced liquid chamber, 103 - enhanced liquid chamber gas 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 gas outlet; 1021 - capillary valve; 1041 - anti-angle separation array I, 1042 - anti-angle separation array II, 1043 - anti-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 gas outlet, 204 - digestion liquid inlet, 205 - digestion liquid chamber, 206 - digestion liquid chamber gas outlet, 207 - digestion chamber gas outlet, 208 - mixing microfluidic channel, 209 - sample digestion chamber. DETAILED DESCRIPTION

[0038] The application will be further described below in conjunction with specific embodiments. Among them, the drawings are only used for exemplary description, and the representation is only a schematic diagram, not a physical diagram, and cannot be understood as a limitation of the patent; in order to better illustrate the embodiments of the application, some components of the drawings will 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 in the drawings and their descriptions can be omitted.

[0039] As Figures 1-4As shown, the present application refers to a centrifugal microfluidic non-blocking multi-stage microplastic particle sorting device, which comprises one or more analysis units 1 arranged around the centrifugal axis 0 of the centrifugal microfluidic chip 2, 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, which performs digestion processing on the sample, 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 digestion chamber 209, the sample chamber 202 is connected to the sample digestion chamber 209 in conjunction with the digestion liquid chamber 205; the microplastic particle size sorting and capturing module 10 is a two-stage linkage sorting and capturing module based on the size and density difference of microplastic, which includes an enhancing liquid chamber 102, a particle size sorting area 104, an extrusion microfluidic channel 105, a gradient particle size separation area 106 and a waste liquid chamber 108, the enhancing liquid chamber 102 provides the necessary enhancing liquid to improve the sorting efficiency, and is connected to the particle size sorting area 104 in conjunction with the sample digestion chamber 209, through the introduction of the enhancing liquid, the preliminary sorting of the microplastic particles is carried out; the particle size sorting area 104 is connected to the gradient particle size separation area 106 through the extrusion microfluidic channel 105 with a neck structure, the mixed liquid passes through the extrusion microfluidic channel 105 under the action of centrifugal force, the microplastic particles are extruded to the outermost side of the channel, which can effectively control the flow of fluid and further enhance the effect of particle size sorting, the gradient particle size separation area 106 separates different microplastic particles according to the difference in particle size and density, and is connected to the waste liquid chamber 108 to collect the waste liquid generated during the sorting process and keep the system clean; n+1 screening subareas are arranged in the particle size sorting area 104 through n anti-angle separation arrays, and n+1 centrifugal force separation chambers are arranged in the gradient particle size separation area 106, and n+1 extrusion microfluidic channels 105 are connected to the n+1 screening subareas one by one, n is a natural number greater than or equal to 2, such design can realize efficient sorting of various microplastic particles with different particle sizes, improve the sorting range of a single chip for microplastic particle size, and enhance the flexibility and adaptability of detection. The length and width of the sample chamber 202, the digestion liquid chamber 205 and the enhancing liquid chamber 102 are 4200μm*3600μm, such size design ensures sufficient volume to accommodate the sample and the digestion liquid, and also provides convenience for subsequent processing and sorting, the length and width can be increased according to the size of the processing amount, the length can be 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 enhancing liquid chamber 102, the sample digestion chamber 209 and the waste liquid chamber 108 are all 200μm(300μm>microchannel height and width>100μm), and the microchannel height and width are the maximum volume equivalent diameter D M3.5-4 times the size of the sample chamber 202, which ensures smooth fluid flow in the microchannel, reduces flow resistance, and ensures rapid delivery and efficient mixing of the liquid; the microchannel is made of PDMS material and is manufactured using a soft lithography casting process, i.e., using polydimethylsiloxane (PDMS) material. PDMS has good biocompatibility, transparency, and excellent elasticity, making it suitable for use in microfluidic devices. Manufacturing process: the microchannel is manufactured using a soft lithography casting process. This process enables high-precision microstructure manufacturing, with good repeatability and stability, making it suitable for large-scale production such as microchannels. The microchannel includes a mixing microfluidic channel 208 that connects the sample chamber 202 and the digestion liquid chamber 205 and is in a meandering shape, and a siphon microfluidic channel 107 that connects the gradient particle size separation zone 106 and the waste liquid chamber 108 and is in a U shape. The meandering shape of the channel can increase the shear force of the fluid, promote uniform mixing of the sample and the digestion liquid, and improve the efficiency of the digestion process. The meandering design helps to reduce the dead zone of the fluid in the channel, ensuring uniform flow of the sample, thereby the meandering design helps to increase the mixing effect of the fluid, ensuring that the sample and the digestion liquid are fully contacted and reacted before entering the sample digestion chamber. The U-shaped channel design helps to control the flow path of the fluid, while avoiding backflow of the fluid, ensuring efficient discharge of the waste liquid, and by corresponding to different centrifugal force separation chambers, it can achieve efficient separation and capture of microplastics of different particle sizes, thereby effectively guiding the flow of the separated liquid to the waste liquid chamber, ensuring efficient operation of the system. The corresponding siphon microfluidic channel 107 is arranged as n+1 and connected one by one with n+1 centrifugal force separation chambers. This design ensures that the separation products of each centrifugal force separation chamber can be smoothly discharged, thereby achieving efficient sorting and processing. The microplastic particle sorting and detection device further includes a portable Raman spectrometer (not shown) for detecting different particle sizes and components of microplastics in the outermost centrifugal force separation chambers in the gradient particle size separation zone 106. The portable Raman spectrometer is a conventional device, and the wavelength used by the portable Raman spectrometer is 785 nm, the excitation power is 25 mW, and the excitation duration is 5 s. The portable Raman spectrometer can detect the particle size and composition of microplastic particles in different centrifugal force 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, providing information about the type of microplastics, thereby helping researchers understand the source and environmental impact of microplastics.

[0040] In the present embodiment, the sample inlet 201 is connected with the sample chamber 202, allowing the user to conveniently introduce the water sample to be treated into the sample chamber 202, i.e. through the sample inlet 201, the sample can be quickly and effectively loaded, reducing the time for sample treatment; while the sample chamber gas outlet 203 is connected with 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 gas outlet 203, keeping the pressure in the sample chamber 202 stable, avoiding the accumulation of gas affecting the subsequent steps; while the digestion liquid inlet 204 is connected with the digestion liquid chamber 205, which is convenient for adding digestion liquid to the digestion liquid chamber, and can adjust the type and concentration of the digestion liquid according to the needs, to adapt to the digestion needs of microplastics in different water samples, and improve the digestion effect; while the digestion liquid chamber gas outlet 206 is connected with the digestion liquid chamber 205, so that the gas in the digestion liquid chamber can be discharged in time during the digestion process, ensuring smooth gas exchange during the digestion process, and preventing excessive pressure caused by gas accumulation; while the digestion chamber gas outlet 207 is directly connected with the sample digestion chamber 209, to allow the gas in the sample digestion chamber 209 to be discharged after digestion is completed, keeping the normal pressure of the system, and preparing for the subsequent sorting process; while the reinforcing liquid inlet 101 is connected with the reinforcing liquid chamber 102, to allow the user to conveniently add reinforcing liquid to the reinforcing liquid chamber to improve the hydrodynamic characteristics in the sorting process, and the user can select the appropriate type and concentration of reinforcing liquid according to different experimental needs, thereby optimizing the sorting effect of microplastic particles; while the reinforcing liquid chamber gas outlet 103 is directly connected with the reinforcing liquid chamber 102, to allow the gas in the reinforcing liquid chamber 102 to be discharged in time, and the gas in the reinforcing liquid chamber can be discharged through the gas outlet during the sorting process, keeping the flow stability of the liquid, reducing the interference of bubbles on the sorting result, which can ensure the uniform distribution of the reinforcing liquid in the sorting area, and improve the sensitivity of the sorting; while the waste liquid chamber gas outlet 109 is connected with the waste liquid chamber 108, to allow the gas in the waste liquid chamber 108 to be discharged in time, keeping the flowability of the waste liquid and the smoothness of the discharge, avoiding the increase of pressure 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 anti-angle separation arrays is set to 3, and the anti-angle separation array I 1041, the anti-angle separation array II 1042, and the anti-angle separation array III 1043, which are gradually reduced in size of microplastic particle size screening, are combined to realize efficient particle size sorting. The anti-angle separation array I 1041, the anti-angle separation array II 1042, and the anti-angle separation array III 1043 are arranged in parallel to the long direction of the particle size sorting area 104 in the particle size sorting area 104, and the array spacing is 40 μm, 30 μm, and 20 μm, respectively, to be used for screening microplastic particles of large size, medium size, and small size, respectively. The anti-angle surface (array gap opening direction angle) of each anti-angle separation array is opposite to the centrifugal force direction of the centrifugal microfluidic chip 2, and the included angle is > 90°, preferably 95° to 130°. This angle design can optimize the fluid dynamics. Through the anti-angle array with an angle greater than 90° (95°-130°) with the water flow direction, the microplastics produce circumferential reverse motion when flowing with the liquid under the action of centrifugal force and Coriolis force, thereby passing through the anti-angle array and realizing the division of the non-blocking particle size range of the microplastics. This helps the microplastic particles of different particle sizes to be more effectively captured and separated during the flow process, reduces experimental errors, and is preferably 118°. Each anti-angle separation array in the particle size sorting area 104 is composed of a hexagonal microcolumn. This shape helps to maximize the flow efficiency of the fluid and improve the particle capture ability. The microcolumn has a lower base length of 110 μm, an upper base length of 150 μm, a height of 100 μm, and a hypotenuse length of 54 μm. This setting can flexibly adjust the number and spacing of the anti-angle separation arrays according to different experimental requirements to adapt to the analysis needs of microplastics in different types of water samples. The design of the hexagonal microcolumn allows the fluid to form a good flow pattern during the sorting process, reduces flow dead zones, and ensures that microplastic particles can be effectively captured and separated. The design of the larger upper base increases the contact area with the fluid, which helps to enhance the interaction force between the microplastic particles and the microcolumn, thereby improving the sorting sensitivity. The moderate height and hypotenuse design can effectively prolong the residence time of microplastic particles in the microcolumn, so that particles of different particle sizes can be better screened.

[0042] The number n+1 of corresponding centrifugal force separation chambers is set to 4, and the centrifugal force separation chambers I 1061, centrifugal force separation chambers II 1062, centrifugal force separation chambers III 1063, and centrifugal force separation chambers IV 1064 are composed of gradually decreasing centrifugal force separation chambers according to the size of the microplastic particles, which helps to effectively capture and separate particles of different sizes, and the length and height of the centrifugal force separation chambers I 1061, centrifugal force separation chambers II 1062, centrifugal force separation chambers III 1063, and centrifugal force separation chambers IV 1064 are 3900 μm*800 μm, 3700 μm*700 μm, 3600 μm*600 μm, and 3450 μm*600 μm, respectively, for capturing microplastics of large, medium, small, and minimum particle sizes, respectively. The outer capture interval of the centrifugal force separation chambers I 1061, centrifugal force separation chambers II 1062, centrifugal force separation chambers III 1063, and centrifugal force separation chambers IV 1064 is 200 μm, 180 μm, 160 μm, and 140 μm, respectively, and the radius of the capture arc in the interval is 54 μm, 44 μm, 34 μm, and 24 μm, respectively. By setting different capture interval and arc radius, microplastic particles of different sizes can be better captured and separated, and the problem of not being able to sort microplastics of a larger particle size range in a single chip is solved. The larger capture interval provides sufficient space for larger particles, while the smaller capture arc radius effectively captures smaller particles, ensuring that no vortex is generated in the centrifugal separation chamber that can affect the sorting effect. The centrifugal force separation chambers I 1061, centrifugal force separation chambers II 1062, centrifugal force separation chambers III 1063, and centrifugal force separation chambers IV 1064 are arranged radially from the centrifugal microfluidic chip 2 to gradually deviate from the centrifugal shaft 0, which can effectively separate microplastics of different sizes during centrifugation by taking advantage of the difference in centrifugal force. The tube diameter of the corresponding four siphon microfluidic channels 107 connected to the centrifugal force separation chambers I 1061, centrifugal force separation chambers II 1062, centrifugal force separation chambers III 1063, and centrifugal force separation chambers IV 1064 is 150 μm, 140 μm, 130 μm, and 120 μm, respectively. The design of the siphon microfluidic channel takes into account the channel diameter, which can optimize the flow speed of the fluid and ensure the flow state of the microplastic particles when passing through the channel, to achieve efficient sorting and transmission.

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

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

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

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

[0047] S3: using adhesive tape (pressure valve) to seal the waste liquid chamber gas outlet 109, and centrifuging the centrifugal microfluidic chip 2 at 500 r / min for 10 s. After the sample solution of microplastic particles to be separated and the digestion reagent are mixed in the mixing microfluidic channel 208, the entire system pressure is maintained by the adhesive tape on the waste liquid chamber gas outlet 109 to complete the digestion of the microplastic in the digestion liquid chamber 205, and the mixed solution cannot continue to flow downward under the action of centrifugal force. Then, the centrifugation is temporarily stopped and the adhesive tape (pressure valve) is torn off to open the waste liquid chamber gas outlet 109;

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

[0049] S5: The mixture under centrifugal force enters the particle size sorting zone 104, and is screened by the anti-angle separation array I 1041, anti-angle separation array II 1042, and anti-angle separation array III 1043 to complete the non-clogging initial screening separation of microplastic particles. Then, the extrusion microfluidic channels 105 corresponding to the four screening zones formed in the particle size sorting zone 104 flow into the centrifugal separation chambers I 1061, II 1062, III 1063, and IV 1064 in the gradient particle size separation zone 106, respectively, so that the microplastic particles after the initial screening are subjected to centrifugal force F. C Coriolis force F Co And Euler F E The effects of three volume forces and their coupling with the liquid: drag force and buoyancy. Based on the equations for the resultant force of volume forces and 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. Where u is the relative velocity of the particle in the water, and F... s This represents the resultant force of centrifugal force and buoyancy on the particle, where r is the radius of the particle, and ρ is the resultant force. p ρ is the density of the microplastics. f R is the density of the liquid, μ is the centrifugal radius, μ is the viscosity coefficient of the liquid, and ω is the rotational speed of the centrifugal microfluidic chip. Under multi-force coupling, microplastics with different particle sizes and densities are further separated by stepwise spreading on the serrated grooves 1065 on the outside and outside of their respective centrifugal separation chambers according to the different centrifugal forces and fluid resistances; 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 focuses on the microplastics on the outermost serrated grooves 1065 of 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, thus completing the detection.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A centrifugal microfluidic clog-free multistage microplastic particle fractionation device based on, comprising one or more analysis units (1) arranged around a centrifugal axis (0) on a 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), 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 enhancing liquid chamber (102), a particle size sorting area (104), an extrusion microfluidic channel (105), a gradient particle size separation area (106) and a waste liquid chamber (108), the enhancing liquid chamber (102) is connected to the particle size sorting area (104) through the sample digestion chamber (209), the particle size sorting area (104) is connected to the gradient particle size separation area (106) through the extrusion microfluidic channel (105) with a neck structure, and the gradient particle size separation area (106) is connected to the waste liquid chamber (108). The particle size sorting area (104) is provided with n+1 screening subareas through n reverse angle separation arrays, the gradient particle size separation area (106) is provided with n+1 centrifugal force separation chambers, and n+1 extrusion microfluidic channels (105) are connected to n+1 screening subareas one by one, and n is a natural number greater than or equal to 2.

2. The centrifugal microfluidic clog-free multistage microplastic particle fractionation device based on the centrifugation according to claim 1, characterized in that, The digestion processing module (20) further comprises a sample inlet (201) and a sample chamber gas outlet (203) in communication with the sample chamber (202), a digestion liquid inlet (204) and a digestion liquid chamber gas outlet (206) in communication with the digestion liquid chamber (205), and a digestion chamber gas outlet (207) in communication with the sample digestion chamber (209); the microplastic particle size sorting and capturing module (10) further comprises an enhancing liquid inlet (101) and an enhancing liquid chamber gas outlet (103) in communication with the enhancing liquid chamber (102), and a waste liquid chamber gas outlet (109) in communication with the waste liquid chamber (108).

3. The centrifugal microfluidic clog-free multistage microplastic particle fractionation device based on the centrifugal microfluidic according to claim 1, characterized in that, The array spacing of the n reverse angle separation arrays is sequentially reduced, that is, D1>D2>D n The array spacing of the first reverse angle separation array is determined by subtracting 5-20 μm from the maximum volume equivalent diameter of the microplastics to be separated, and the array spacing reduction value between adjacent two reverse angle separation arrays is between 5-20 μm, and the opening of each reverse angle separation array has an inverse slope with an angle of 95-130° with the centrifugal force direction of the centrifugal microfluidic chip (2).

4. The centrifugal microfluidic clog-free multistage microplastic particle fractionation device based on centrifugation according to claim 3, wherein, The number n of the reverse angle separation arrays is set to 3, the array spacing is sequentially reduced, and the reverse angle separation arrays I (1041), the reverse angle separation arrays II (1042) and the reverse angle separation arrays III (1043) are arranged in the radial direction of the centrifugal microfluidic chip (2) to gradually move away from the centrifugal shaft center (0); correspondingly, the number n+1 of the centrifugal force separation chambers is set to 4, the microplastic particle size separation is gradually reduced, and the centrifugal force separation chamber I (1061), the centrifugal force separation chamber II (1062), the centrifugal force separation chamber III (1063) and the centrifugal force separation chamber IV (104) are arranged in the radial direction of the centrifugal microfluidic chip (2) to gradually move away from the centrifugal shaft center (0).

5. The centrifugal microfluidic clog-free multistage microplastic particle fractionation device based on the centrifugal microfluidic according to claim 1, characterized in that, The length-width ratio of the n+1 centrifugal force separation chambers is between 0.5 and 0.75, and the length of each is 60-80 times the maximum volume equivalent diameter of the microplastics to be separated.

6. The centrifugal microfluidic clog-free multistage microplastic particle fractionation device based on fractionation of claim 1, wherein, The inner bottom of each of the n+1 centrifugal force separation chambers is provided with a sawtooth groove (1065) for gradually laying microplastic particles.

7. The centrifugal microfluidic clog-free multistage microplastic particle fractionation device based on the centrifugal microfluidic according to claim 1, characterized in that, The length-width ratio of the sample chamber (202), the digestion liquid chamber (205) and the enhancement liquid chamber (102) is between 1.2 and 1.6, and the length of each is 120-160 times the maximum volume equivalent diameter of the microplastics to be separated; the width of the microchannels connected with 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) is equal, and the width of each is 3.5-4 times the maximum volume equivalent diameter of the microplastics to be separated, and is between 100 and 300 microns; the microchannels are made of PDMS material and are made by soft photolithography pouring process.

8. The centrifugal microfluidic clog-free multistage microplastic particle fractionation device based on centrifugation according to claim 7, wherein, The microchannels include a mixed microfluidic channel (208) connecting the sample chamber (202) and the digestion liquid chamber (205) with the sample digestion chamber (209) after merging and in a meandering shape, and a siphon microfluidic channel (107) connecting the gradient particle size separation zone (106) with the waste liquid chamber (108) and in a U shape, and the corresponding siphon microfluidic channels (107) are arranged as n+1 and connected with n+1 centrifugal force separation chambers one by one.

9. The centrifugal microfluidic non-clogging multistage microplastic particle fractionation device based on the claims 1-8, characterized in that, The microplastic particle sorting and detection device further comprises a portable Raman spectrometer for detecting different particle sizes and components of microplastics in each centrifugal force separation chamber in the gradient particle size separation zone (106).

10. A detection method employing the centrifugal microfluidic clog-free multistage microplastic particle fractionation device according to claim 9, characterized in that, The method comprises the following steps: S1: configure the microplastic particle sample solution to be separated, the digestion reagent, and the SERS enhancement reagent; S2: use a syringe to fill the sample chamber (202) with a set amount of the microplastic particle sample solution 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 adhesive tape to seal the waste liquid chamber gas outlet (109), and perform centrifugation on the centrifugal microfluidic chip (2), so that the microplastic particle sample solution to be separated mixes with the digestion reagent, enters the digestion liquid chamber (205), and completes the digestion treatment of the microplastics, and then the waste liquid chamber gas outlet (109) is opened; S4: perform centrifugation on the centrifugal microfluidic chip (2) again, so that the digested sample solution in the digestion liquid chamber (205) mixes with the enhancement reagent in the enhancement liquid chamber (102) to form a mixed solution; S5: under the centrifugal force, the mixed solution enters the particle size sorting zone (104), and is filtered by n anti-angle separation arrays to complete the initial screening and separation of the microplastics, and then the n+1 extrusion microfluidic channels (105) formed by the n+1 screening sub-zones in the particle size sorting zone (104) respectively flow into the n+1 centrifugal force separation chambers in the gradient particle size separation zone (106), so that the microplastic particles after the initial screening are separated again in the respective centrifugal force separation chambers under the action of multiple forces according to the difference in particle size and density; the waste liquid formed in each centrifugal force separation chamber enters the waste liquid chamber (108) through the corresponding siphon microfluidic channel (107). S6: Focus on the microplastics in each centrifugal force separation chamber in the gradient particle size separation zone (106) by the portable Raman spectrometer to obtain the Raman characteristic spectrum of different microplastic particle sizes, complete the detection.

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