Marine micro-plastic particle sorting and enriching integrated device and method based on bidirectional surface acoustic wave

Abstract

The invention discloses an ocean micro-plastic particle sorting and enriching integrated device and method based on bidirectional acoustic surface waves, and belongs to the crossing field of an acoustic micro-fluidic technology and ocean environment monitoring. According to the device, an inclined micro-channel design and a standing wave sound field coupling mechanism are adopted, flexible interdigital transducers which are symmetrically arranged in a sorting module are used for exciting surface acoustic waves with specific frequencies, and a high-strength sound pressure standing wave field is formed in a micro-channel. According to the particle size distribution characteristics of micro-plastic particles in the marine environment, efficient sorting of micro-plastic is achieved by accurately regulating and controlling acoustic radiation force parameters. And the sorted micro-plastics are directly introduced into the annular enrichment module, and the sound streaming effect generated by a traveling wave sound field is utilized to realize rapid enrichment of particles. According to the device, the technical bottleneck of sample transfer loss in the traditional method is overcome through the integrated design of the sorting and enriching process, and a high-sensitivity and low-cost pretreatment solution is provided for marine micro-plastic pollution monitoring.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of acoustic wave devices and microfluidic chips, and in particular to a marine microplastic particle sorting and enrichment integrated device and method based on bidirectional surface acoustic waves. BACKGROUND

[0002] In the field of marine environmental monitoring and microplastic pollution research, efficiently and low-loss sorting and enriching microplastic particles of different particle sizes is becoming a key and challenging core requirement. Traditional methods relying on density flotation and screening have obvious limitations, with low recovery rate and subsequent manual intervention. Microfluidic surface acoustic wave technology combines the precise fluid control of microfluidics and the non-contact manipulation ability of acoustic waves, and has unique advantages in marine microplastic monitoring due to its high efficiency, precision and miniaturization. However, traditional microfluidic technology usually uses independent operation processes for sorting and enriching microplastics, which significantly prolongs the sample processing period and greatly reduces the efficiency. More critically, when marine environmental samples are transferred between different functional modules or devices, microplastic particles are easily lost or diluted. This is particularly serious for low-concentration and wide-particle-size-distribution marine microplastic samples, as even a small loss can lead to distorted particle size distribution statistics or inaccurate pollutant quantification. At the same time, complex operation processes also introduce more potential human and system errors. Such losses and errors are unacceptable in marine microplastic pollution monitoring and source analysis, which can lead to pollution assessment bias or incorrect source tracing conclusions, seriously affecting the reliability of marine environmental monitoring data. SUMMARY

[0003] To solve the technical bottleneck in the sorting and enrichment of marine microplastics, the present application proposes a marine microplastic sorting and enrichment integrated device and method based on bidirectional surface acoustic waves. This technology forms a specific acoustic field distribution in the microfluidic channel and micro-ring by regulating two counter-propagating surface acoustic waves, achieving the simultaneous sorting and enrichment of microplastics of different particle sizes. The entire process is completed in a closed microfluidic system, avoiding the loss caused by sample transfer in traditional methods. This device is designed specifically for microplastics in the 1-50 μm particle size range in marine environments, and has the advantages of high processing efficiency, low sample loss, and simple operation compared to existing technologies. It provides a reliable pre-processing solution for marine microplastic pollution monitoring and has important application value in marine environmental investigation, microplastic source analysis, and ecological risk assessment.

[0004] The technical solutions of the present application are as follows:

[0005] A marine microplastic particle sorting and enrichment integrated device based on bidirectional surface acoustic waves, comprising a signal generation module, a sorting module, an enrichment module, and a suppression module.

[0006] The signal generating module comprises an aluminum plate base, a radio frequency line, a piezoelectric material base and a flexible interdigital transducer; the aluminum plate base is provided with a long groove and a light hole; the piezoelectric material base is arranged in the long groove of the aluminum plate base; the flexible interdigital transducer extends positive and negative electrodes to both sides and is made on a flexible base and connected to an external circuit by welding; the spatial period of the interdigital electrode structure is determined according to different sizes of the particles to be processed;

[0007] The sorting module adopts a sorting microchannel bonded on the piezoelectric material base and arranged in the opposite area of the two flexible interdigital transducers; the included angle between the sorting microchannel and the flexible interdigital transducer is 10°-20°; the sorting microchannel comprises a channel inlet, a sorting channel and a channel outlet;

[0008] The enrichment module comprises two enrichment microloops arranged outside the flexible interdigital transducers and opposite to the light hole of the base; the channel outlet of the sorting microchannel is connected to the enrichment microloop through a hose;

[0009] The pressing module comprises a pressing plate, a square hole in the middle of the pressing plate accommodating the enrichment module and connected to the aluminum plate base by a screw, so that the lower flexible interdigital transducer is tightly attached to the piezoelectric material base.

[0010] Further, the sorting microchannel is provided with a first inlet, a second inlet and a third inlet; the second inlet is consistent with the direction of the sorting channel; the first inlet and the third inlet are symmetrically arranged on both sides of the first inlet; the channel outlet of the sorting microchannel comprises a first inlet and a second outlet; the two outlets are symmetrically arranged with the sorting channel as the axis.

[0011] Further, the included angle between the sorting microchannel and the flexible interdigital transducer is 15°.

[0012] Further, the flexible interdigital transducer adopts a bidirectional extension type; a gold / copper composite conductive layer is prepared on a polyimide flexible base by magnetron sputtering; the positive and negative electrodes are symmetrically extended to both sides to form two excitation zones; two beams interfere in the center of the sorting microchannel to form a high-intensity standing wave field to realize the sorting function; meanwhile, a directional traveling wave field is formed to realize the enrichment function; the interdigital spatial period λ=v / f is adjusted according to the particle size to be processed.

[0013] Further, the enrichment module comprises two independent enrichment microloops which form a one-to-one driving architecture with the two flexible interdigital transducers, i.e. each interdigital transducer independently excites a traveling wave sound field; the sound wave area of the enrichment microloop is arranged in the sound field and the evanescent area is arranged outside the sound field; the area of the sound wave area is greater than that of the evanescent area; a directional acoustic flow vortex is formed in the enrichment microloop.

[0014] Further, the sorting microchannel and the enrichment microloop are firmly combined with the piezoelectric material substrate through the oxygen plasma treatment technology to form Si-O-Si bonds.

[0015] Further, the piezoelectric material substrate is a 128° Y-X cut lithium niobate crystal, and the surface acoustic wave propagation direction is along the X axis, which is suitable for exciting a bidirectional surface acoustic wave with a frequency of 5-50 MHz.

[0016] The use method of the device is to synchronize the sorting and enrichment of particles of different sizes, which specifically includes the following steps:

[0017] S1. According to the particle size distribution range of the target microplastic of 1-50 μm, a sorting microchannel with a sound wave wavelength adapted to the enrichment microloop is selected, wherein the sorting microchannel adopts a piezoelectric material substrate with an inclination of 15°;

[0018] S2. A hose is used to connect the three inlets to the sheath flow injector and the sample injector, respectively, wherein the first inlet and the third inlet are connected to the sheath flow injector and control the flow rate, the second inlet is connected to the sample injector and controls the flow rate, and the flow rate ratio of the sheath flow injector to the sample injector is 3:1, and the first outlet and the second outlet are connected to the first enrichment microloop and the second enrichment microloop through the hose, respectively;

[0019] S3. According to the surface acoustic wave velocity and the set frequency, the space period between the two flexible interdigital transducers is set, the two electrodes are placed opposite to each other, and the interdigital electrode area is directed towards the sorting microchannel;

[0020] S4. Connect the circuit, input the radio frequency signal to the flexible interdigital transducer through the SMA interface, generate the surface acoustic wave on the piezoelectric material substrate, adjust the frequency and amplitude of the input signal, and simultaneously form a standing wave field for sorting and a traveling wave field for enrichment in the sorting microchannel and the enrichment microloop, wherein the standing wave field has a half wavelength between the sound pressure nodes;

[0021] S5. The sorting and enrichment process is monitored in real time under an inverted microscope, the sample is injected into the sorting channel from the second inlet by using the injection pump, the sheath flow is injected into the sorting channel from the first inlet and the third inlet by using the injection pump, and during the observation process, the observation platform is translated at any time according to the experimental requirements, so that the microscope field of view is switched between the standing wave node in the sorting area and the two enrichment microloop areas, and the synchronization of the sorting effect and the enrichment effect is realized. Visual monitoring;

[0022] S6. The target micro-particle in the center of the enrichment microloop area is transferred out by using a pipette gun, and the sorting and enrichment of the microplastic are completed.

[0023] Further, the first inlet and the third inlet are connected to the sheath flow injector and control the flow rate of 1.5 μL / min, and the second inlet is connected to the sample injector and controls the flow rate of 0.5 μL / min.

[0024] Specifically, the flexible interdigital transducer is a magnetron sputtered interdigital transducer on a polyimide or PET. The interdigital electrode forms a periodic acoustic pressure field in the microchannel by exciting high-frequency surface acoustic waves on a lithium niobate substrate. Under the action of acoustic radiation force, cells or particles are driven to the pressure node or anti-node due to differences in size, density and other characteristics, achieving sorting.

[0025] Specifically, while sorting is being performed, the two types of particles that have been sorted are introduced into two independent enrichment micro-rings through the hoses at the outlets, and a one-to-one driving architecture is formed with the two flexible interdigital transducers, i.e., each interdigital transducer independently excites a traveling wave acoustic field to form a directed acoustic flow vortex in the dedicated micro-ring, which respectively pushes the two types of particles sorted to the center region, completing the integration of sorting and enrichment.

[0026] Compared with the prior art, the present application has the following significant advantages:

[0027] (1) Compared with the separation process requiring multiple devices in series, the integrated design integrates the acoustic tweezer manipulation, sorting and enrichment functions in a single microfluidic platform, significantly reducing the sample transfer steps and operation time, avoiding sample loss and contamination risks caused by multiple device connections, and being particularly suitable for clinical and on-site rapid detection needs.

[0028] (2) The entire process only requires a pair of interdigital electrodes, and the sorting and enrichment functions can be simultaneously achieved by single frequency control, greatly improving the practicality and economy of the system. Compared with the design of multiple electrodes and complex frequency tuning in the traditional scheme, only one frequency setting is required in this technology. This simplified architecture makes the device directly compatible with the power supply and signal system of existing acoustic flow control platforms, without the need for additional modification, reducing the difficulty of experimental operation and use cost.

[0029] (3) Traditional flow cytometry relies on fluorescent labeling, and centrifugal separation relies on shear force, both of which will affect cell activity. The acoustic tweezer technology only uses acoustic radiation force for physical manipulation without any labeling or strong external force, maximizing cell integrity and function, and being particularly suitable for fragile cells and subsequent culture research.

[0030] (4) Traditional centrifugation relies on the sedimentation coefficient, and filter sorting is fixed in aperture, making it difficult to achieve continuous size coverage. The device can accurately sort a wide range of microparticles from nanoscale to micrometer scale by adjusting the parameters of the acoustic field.

[0031] (5) The replaceable microfluidic chip and interdigital transducer module can be quickly replaced with matching components according to different samples such as cell solutions and environmental samples, greatly expanding the application scenarios of the device. BRIEF DESCRIPTION OF DRAWINGS

[0032] The accompanying drawings are included to provide a further understanding of the present application, and are incorporated in and constitute a part of this specification. To clearly illustrate the technical solutions in the embodiments or in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced.

[0033] Figure 1 is an exploded view of a two-way surface wave-based ocean micro-plastic particle sorting and enrichment integrated device structure.

[0034] Figure 2 is a sorting experiment effect diagram.

[0035] Figure 3 is an enrichment experiment effect diagram.

[0036] Figure 4 is a sorting microchannel and enrichment microloop physical diagram.

[0037] Figure 5 is an experimental principle diagram.

[0038] The figure legend is shown as: 1. metal spring needle, 2. SMA interface, 3. pressing plate, 4. sorting microchannel, 4a. first inlet, 4b. second inlet, 4c. third inlet, 4d. first outlet, 4e. second outlet, 4f. sorting channel, 5. enrichment microloop, 5a. evanescent zone, 5b. acoustic wave zone, 501. first enrichment microloop, 502. second enrichment microloop, 6. flexible interdigital transducer, 7. piezoelectric material substrate, 8. aluminum plate base, 8a. long groove, 8b. light hole, 9. hose. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0040] Figure 1 and Figure 5 A two-way surface wave-based ocean micro-plastic particle sorting and enrichment integrated device is shown in the drawings, which comprises a signal generation module, a sorting module, an enrichment module and a pressing module.

[0041] The signal generating module comprises an aluminum plate base 8, a radio frequency line, a piezoelectric material base 7 and a flexible interdigital transducer 6. The aluminum plate base 8 is provided with a long groove 8a and a base through hole 8b. The piezoelectric material base 7 is arranged in the long groove 8a of the aluminum plate base 8. The flexible interdigital transducer 6 is made on a flexible substrate by extending the positive and negative electrodes of a traditional interdigital electrode structure to both sides and connecting with external circuits by welding. The space period of the interdigital electrode structure is determined according to the different sizes of the particles to be processed.

[0042] The sorting module adopts a sorting microchannel bonded on the piezoelectric material base 7. The channel outlet is connected with the enrichment module through a hose. The enrichment module adopts two enrichment micro-rings 5. The first enrichment micro-ring 501 and the second enrichment micro-ring 502 are respectively located on both sides of the piezoelectric material base 7 and opposite to the light through hole 8b of the base 8.

[0043] The pressing module comprises a pressing plate 3. The square hole in the middle of the pressing plate 3 accommodates the enrichment module and is connected with the aluminum plate base 8 through screws, so that the lowermost flexible interdigital transducer 6 is tightly attached to the piezoelectric material base 7.

[0044] The flexible interdigital transducer 6 adopts a bidirectional extension type innovative design. A gold / copper composite conductive layer is prepared on a polyimide flexible substrate by magnetron sputtering. The positive and negative electrodes of the traditional interdigital electrode structure are symmetrically extended to both sides to form two excitation zones. Two beams interfere in the center of the microchannel to form a high-intensity standing wave field to realize the sorting function. At the same time, each forms a directional traveling wave field to realize the enrichment function. The interdigital space period λ=v / f can be adjusted according to the particle size of 1-50 μm. The end is provided with a flip chip to ensure stable transmission of high-frequency signals and realize synchronous improvement of sorting and enrichment efficiency.

[0045] The enrichment module comprises two independent enrichment micro-rings, i.e. the first enrichment micro-ring 501 and the second enrichment micro-ring 502, which form a one-to-one driving architecture with the two flexible interdigital transducers 6, i.e. each interdigital transducer independently excites a traveling wave sound field. The sound wave area 5b of the enrichment micro-ring is placed in the sound field, and the evanescent area 5a is placed outside the sound field. The area of the sound wave area 5b is greater than that of the evanescent area 5a. A directional acoustic flow vortex is formed in the exclusive micro-ring, which improves the total throughput. At the same time, this parallel processing unit enables the sorted particles to enter the corresponding enrichment micro-rings simultaneously, thereby accelerating the speed of simultaneous enrichment of the two kinds of particles.

[0046] Si-O-Si bonds are formed by oxygen plasma treatment technology, so as to realize firm bonding between the sorting microchannel 4 and the enrichment micro-ring 5 and the substrate.

[0047] The piezoelectric material base 7 is a 128° Y-X cut lithium niobate crystal. The acoustic surface wave propagation direction is along the X axis, which is suitable for exciting a bidirectional acoustic surface wave with a frequency of 5-50 MHz.

[0048] The sorting module is located in the area directly opposite the pair of flexible interdigital transducers 6, and the channel inclination angle is 15°. The 15° offset microchannel design is mainly to optimize the synergy of the sound field and the flow field through the inclined structure, thereby improving the sorting efficiency and accuracy. This angle design breaks the symmetry of the traditional straight channel, making it easier for particles to move to the side and be sorted out, while avoiding excessive angle-induced fluid disturbance or energy loss. The 15° inclination angle is precisely balanced to maximize the efficiency of the sound field on the particles while ensuring the stability of the laminar flow. This angle design avoids both the insufficient manipulation force caused by a small angle and the flow field disturbance caused by a large angle, allowing the system to achieve efficient and accurate particle sorting.

[0049] The two enrichment micro-rings of the enrichment module 5 are placed with an offset, as shown in Figure 5 That is, the inner part of the micro-ring needs to cover the main area of sound wave propagation, and the outer edge extends to the evanescent zone of the sound wave field, forming a gradient energy distribution, which can make the micro-ring in the transition area with the maximum sound pressure gradient, thereby realizing the enrichment function. This layout not only avoids interference from sound wave reflection, but also takes advantage of the directional vortex effect generated by the traveling wave sound flow to achieve a balance between sound energy utilization and enrichment performance.

[0050] A method for using a two-way surface acoustic wave-based ocean micro-plastic particle sorting and enrichment integrated device synchronously processes the sorting and enrichment of particles of different sizes, including the following steps:

[0051] S1. According to the particle size distribution range of the target micro-plastic, 1-50 μm, select a sorting micro-channel 4 and an enrichment micro-ring 5 with specific sound wave wavelength adaptation parameters, wherein the micro-channel adopts a 15° inclination design, and the microfluidic component is firmly bonded to the surface of the lithium niobate piezoelectric material substrate through oxygen plasma treatment to form a uniform Si-O-Si covalent bond interface layer.

[0052] S2. During the fluid pipeline connection stage, a hose is used to connect the three inlets to the sheath flow injector and the sample injector, respectively, wherein the first inlet 4a and the third inlet 4c are connected to the sheath flow injector and control the flow rate to be 1.5 μL / min, the second inlet 4b is connected to the sample injector and controls the flow rate to be 0.5 μL / min, ensuring that the flow rate ratio of the sheath flow to the sample is 3:1, achieving good sorting results, and the first outlet 4d and the second outlet 4e are connected to the first enrichment micro-ring 501 and the second enrichment micro-ring 502 through the hose 9.

[0053] S3. During the assembly of the two-way sound field module, first, select a flexible interdigital transducer with a suitable spatial period according to the sound surface wave speed and the set frequency, place the two electrodes directly opposite each other and make the interdigital electrode area face the center of the microchannel, then assemble the PDMS buffer layer, the silicon plate and the aluminum alloy pressing plate in turn, and finally fix them with a torque screw.

[0054] S4. Connecting circuit, inputting radio frequency signal to flexible interdigital transducer 6 through SMA interface 2, generating acoustic surface wave on piezoelectric material base 7, adjusting frequency and amplitude of input signal, simultaneously forming standing wave field for sorting and traveling wave field for enrichment in microchannel and microloop, wherein acoustic pressure node spacing of standing wave field is half wavelength;

[0055] S5. Sorting and enrichment process is monitored in real time under inverted microscope, sample is slowly injected into microchannel from second inlet 4b, sheath flow is slowly injected into microchannel from first inlet 4a and third inlet 4c through injection pump, during observation, observation platform can be translated at any time according to experimental requirements, so that microscope field of view is switched between observation through central light hole in standing wave node in sorting area and observation through two light holes on both sides in two enrichment microloop areas, so that synchronous visual monitoring of sorting effect and enrichment effect is realized;

[0056] S6. Target microparticles in the center of enrichment area are transferred out by using a pipette gun.

[0057] Example 1

[0058] Please refer to Figure 5 , Figure 5 The structure and principle diagram of the device for sorting and enriching marine microplastic particles based on bidirectional acoustic surface wave is shown in the figure. Two flexible interdigital transducers 6 are placed opposite to each other, and the spacing between them is determined according to the size of the sorting microchannel 4. The spacing should be as close to the microchannel as possible to make the experimental results more obvious. The size of the microchannel used in the experiment is 800 μm in width and 100 μm in height. The enrichment microloop 5 of the enrichment module should be offset from the center of the interdigital transducer, and the diameter of the microloop is 10 mm.

[0059] Input radio frequency signal, adjust the frequency and amplitude of the input electrical signal, so that the difference between the input and output power meter readings is maximum, and the input signal reaches 25 dBm. Connect the injection pump, the inlet hose and the microchannel. Place the entire sorting and enrichment integrated device under the microscope, and adjust the platform height to make the image clear.

[0060] Inject a mixed solution of 1 μm and 20 μm microparticles from the second inlet 4b of the microchannel through the injection pump and the inlet hose, and inject sheath flow from the first inlet 4a and the third inlet 4c of the microchannel. The diameter of the microloop is 10 mm.

[0061] Move the observation platform to observe the sorting and enrichment effects in real time, such as Figure 3 is the sorting experiment effect diagram of the mixed solution of 1 μm and 20 μm microparticles, Figure 4 are the enrichment effect diagrams of 1 μm and 20 μm microparticles, respectively.

[0062] Finally, the target particles in the enrichment area are sucked by a pipette, and thus a high-concentration target particle solution is obtained for subsequent research.

[0063] The application provides a two-way surface acoustic wave-based ocean micro-plastic sorting and enrichment integrated device and method, a specific acoustic field is formed by two-way excitation of an interdigital transducer surface acoustic wave, and synchronous sorting and enrichment of micro-plastics with different particle sizes are realized.

[0064] Finally, it should be noted that the scope of protection of the present application is not limited to the applications and technical solutions disclosed in the embodiments. Any person skilled in the art can make appropriate changes and substitutions within the scope of the technology disclosed in the present application according to specific application requirements and environmental conditions. These possible changes and substitutions, including but not limited to material selection, structure adjustment, function extension and integration with other technologies, should be considered as part of the scope of protection of the present application.

Claims

1. An integrated device for sorting and enriching marine microplastic particles based on two-way surface acoustic waves, characterized in that: It includes a signal generation module, a sorting module, an enrichment module, and a suppression module; The signal generation module includes an aluminum plate base (8), a piezoelectric material substrate (7), and a flexible interdigital transducer (6); the aluminum plate base (8) is provided with a long groove (8a) and a light-transmitting hole (8b); the piezoelectric material substrate (7) is disposed in the long groove (8a) of the aluminum plate base (8); the flexible interdigital transducer (6) extends the positive and negative electrodes to both sides and is fabricated on the flexible substrate, and is connected to the external circuit by welding, and the spatial period of the interdigital electrode structure is determined according to the size of the particles to be processed; In the sorting module, the sorting microchannel (4) is bonded to the piezoelectric material substrate (7) and placed in the area directly opposite to the two flexible interdigital transducers (6); the angle between the sorting microchannel (4) and the flexible interdigital transducers (6) is 10°-20°; the sorting microchannel (4) includes a channel inlet, a sorting channel and a channel outlet; The enrichment module includes two enrichment microrings, which are placed outside the flexible interdigital transducer (6) and directly opposite the light-transmitting hole (8b) of the base (8); the channel outlet of the sorting microchannel (4) is connected to the enrichment microrings via a flexible tube (9); The pressing module includes a pressing plate (3), the square hole in the middle of the pressing plate (3) accommodates the enrichment module, and is connected to the aluminum plate base (8) by screws, so that the flexible interdigital transducer (6) below is tightly attached to the piezoelectric material substrate (7).

2. The apparatus according to claim 1, characterized in that: The sorting microchannel (4) is provided with a first inlet (4a), a second inlet (4b) and a third inlet (4c). The second inlet (4b) is in the same direction as the sorting channel (4f). The first inlet (4a) and the third inlet (4c) are symmetrically arranged on both sides of the first inlet (4b). The channel outlet of the sorting microchannel (4) includes a first inlet (4d) and a second outlet (4e). The two outlets are symmetrically arranged about the sorting channel (4f) as an axis.

3. The apparatus according to claim 1, characterized in that: The angle between the sorting microchannel (4) and the flexible interdigital transducer (6) is 15°.

4. The apparatus according to claim 1, characterized in that, The flexible interdigital transducer (6) is bidirectionally extended. A gold / copper composite conductive layer is prepared on a polyimide flexible substrate by magnetron sputtering. The positive and negative electrodes are symmetrically extended to both sides to form two excitation regions: the two beams interfere at the center of the sorting microchannel to form a high-intensity standing wave field to achieve the sorting function, and at the same time, they each form a directional traveling wave field to achieve the enrichment function; its interdigital spatial period λ=v / f is adjusted according to the particle size of the processed particles.

5. The apparatus according to claim 1, characterized in that, The enrichment module contains two independent enrichment microrings, which are respectively connected to two flexible interdigital transducers to form a one-to-one driving architecture. That is, each interdigital transducer independently excites a traveling wave sound field. The acoustic region (5b) of the enrichment microring is placed inside the sound field, and the evanescent region (5a) is placed outside the sound field. The area of ​​the acoustic region (5b) is larger than the area of ​​the evanescent region (5a), forming a directional acoustic vortex inside the enrichment microring.

6. The apparatus according to claim 1, characterized in that, The sorting microchannels (4) and enrichment microrings (5) are firmly bonded to the piezoelectric material substrate (7) by forming Si-O-Si bonds through oxygen plasma treatment technology.

7. The apparatus according to claim 1, characterized in that, The piezoelectric material substrate (7) is a 128°YX tangential lithium niobate crystal, and its surface acoustic wave propagation direction is along the X-axis, which is suitable for excitation frequency of bidirectional surface acoustic waves of 5-50MHz.

8. The method of using the device according to any one of claims 1-7, characterized in that, The sorting and enrichment of particles of different sizes are processed simultaneously, specifically including the following steps: S1. Based on the particle size distribution range of the target microplastics (1-50 μm), select sorting microchannels and enrichment microrings with suitable acoustic wavelengths, wherein the sorting microchannels use a piezoelectric material substrate tilted at 15°. S2. In the fluid pipeline connection stage, the three inlets are connected to the sheath flow injector and the sample injector respectively using a hose. The first inlet (4a) and the third inlet (4c) are connected to the sheath flow injector and the flow rate is controlled. The second inlet (4b) is connected to the sample injector and the flow rate is controlled. The flow rate ratio between the sheath flow injector and the sample injector is 3:

1. The first outlet (4d) and the second outlet (4e) are connected to the first enrichment microring (501) and the second enrichment microring (502) respectively through the hose (9). S3. Set the spatial period between the two flexible interdigital transducers (6) according to the surface acoustic wave velocity and the set frequency, place the two electrodes facing each other and make the interdigital electrode area face the sorting microchannel (4). S4. Connect the circuit and input the radio frequency signal to the flexible interdigital transducer (6) through the SMA interface (2) to generate surface acoustic waves on the piezoelectric material substrate (7). Adjust the frequency and amplitude of the input signal to simultaneously form a standing wave field for sorting and a traveling wave field for enrichment in the sorting microchannel and enrichment microring, wherein the acoustic pressure node spacing of the standing wave field is half a wavelength. S5. The sorting and enrichment process is monitored in real time under an inverted microscope. The observation platform can be moved at any time according to experimental needs, so that the microscope field of view can be switched between the standing wave node of the sorting area and the two enrichment micro-ring areas, realizing synchronous visualization and monitoring of sorting and enrichment effects. S6. Use a pipette to transfer the target microparticles from the center of the enriched microring region to complete the sorting and enrichment of microplastics.

9. The working method according to claim 8, characterized in that: The first inlet (4a) and the third inlet (4c) are connected to the sheath flow injector and the flow rate is controlled at 1.5 μL / min. The second inlet (4b) is connected to the sample injector and the flow rate is controlled at 0.5 μL / min.

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