A microplastic sorting device and method based on microfluidic thermophoresis coupled deterministic lateral displacement

Abstract

The present invention provides a microplastic sorting device and method based on microfluidic thermophoresis coupled deterministic lateral displacement, which relates to the technical field of microplastic particle sorting in water, and comprises a primary sorting mold and a fine sorting module, wherein the primary sorting mold comprises a micro-nano bubble flotation zone and a thermophoresis microfluid lateral deviation zone; a lateral temperature gradient is formed in the thermophoresis microfluid lateral deviation zone by heating a copper electrode plate, and microplastic particles of different sizes are discharged from a sample outlet I or a sample outlet II. The present invention can not only sort microplastic particles of different particle sizes, but also sort microplastic particles of different forms. When the sorted granular microplastics enter a microcolumn array, the risk of blockage can be greatly reduced, and the obstruction of granular microplastics by irregular-shaped microplastics in the microcolumn array can be eliminated, thereby ensuring the sorting efficiency of the microplastic particles and improving the sorting accuracy of the microplastic particles.

Description

Technical Field

[0001] The present invention relates to the technical field of microplastic particle sorting in water, and in particular to a microplastic sorting device and method based on microfluidic thermophoresis coupled deterministic lateral displacement. Background Art

[0002] Microplastics, as garbage in waters, are far more harmful than ordinary-sized marine plastic garbage due to their nature, large quantity and wide sources. They are difficult to degrade in waters and tend to persistently absorb organic pollutants, heavy metal ions and microorganisms, which can cause certain toxic effects on marine organisms through mechanisms such as oxidative stress, nerve damage, endocrine disruption and immune system damage. They can also accumulate through the food chain and may paralyze the entire marine ecosystem.

[0003] At present, the technologies for detecting microplastics in water bodies include pyrolysis-gas chromatography / mass spectrometry, Fourier transform-infrared spectroscopy (FT-IR), Raman spectroscopy (Raman), etc. Among them, pyrolysis-gas chromatography / mass spectrometry has high detection cost, complex operation and long time consumption. Fourier transform-infrared spectroscopy (FT-IR) is not suitable for the detection of microplastics below 10μm and has limitations. Raman spectroscopy can detect microplastics with a particle size as low as 1μm, but this method has requirements for the concentration of microplastics. When the concentration of the detected microplastics is low, the Raman signal is weak, and traditional Raman spectroscopy cannot adapt to the detection of low-concentration microplastics. Therefore, it is particularly important to develop a device and method for sorting and detecting microplastic particles in aqueous solution, and to quickly and efficiently complete the relevant research on sorting and detecting microplastic particles.

[0004] A multi-stage microplastic particle sorting device with a publication number of "CN117619731A" in the prior art includes a primary lateral displacement sorting module, a buffer module and a fine-stage lateral displacement sorting module, which are connected to the fine-stage lateral displacement sorting module through the buffer module, and the external liquid is introduced into the primary lateral displacement sorting module through the sample inlet and the sheath liquid inlet; the initial sorting stage in the microfluidic channel is composed of a circular microcolumn array, and the fine sorting stage is composed of a triangular microcolumn array; the fine-stage lateral displacement sorting module is provided with a partition, and the partition separates the fine-stage lateral displacement sorting module into a large particle size sorting channel and a small particle size sorting channel, and the buffer module is separated into a large particle size buffer channel and a small particle size buffer channel, and the large particle size sorting channel and the small particle size sorting channel are respectively connected to different sample outlets. The above device can sort four types of microplastic particles in a single chip, and the microplastic particle sorting efficiency is high.

[0005] Although the above-mentioned device achieves low-cost sorting of microplastics, it still has obvious defects during use: since the microplastics in the water body exist not only in the form of particles, but also in large quantities in the form of flakes and rods, due to their special geometric structure, it is difficult for them to pass through the above-mentioned microcolumn array for sorting. After entering the microcolumn array, it is very easy to cause two-way blockage of the channel, which affects the overall sorting efficiency on the one hand, and the sorting accuracy of granular microplastics on the other hand. However, the existing microplastic sorting field has not proposed an effective solution to the problems caused by microplastics with this special geometric structure. Summary of the invention

[0006] The purpose of the present invention is to provide a microplastic sorting device and method based on microfluidic thermophoresis coupled deterministic lateral displacement to solve the problems raised in the above background technology.

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

[0008] A microplastic sorting device based on microfluidic thermophoresis coupled deterministic lateral displacement, comprising a primary sorting module and a fine sorting module, wherein the primary sorting module and the fine sorting module are interconnected, and a sample inlet channel and a sheath liquid inlet channel are arranged at the front end of the primary sorting module;

[0009] The primary sorting module includes a micro-nano bubble flotation zone and a thermophoretic microfluid lateral deviation zone;

[0010] A micro-nano bubble generating plate is arranged at the bottom of the micro-nano bubble flotation zone, and an ultrasonic vibration device is also connected to the micro-nano bubble generating plate. The bubble columns arranged on the micro-nano bubble generating plate extend into the micro-nano bubble flotation zone. A primary sorting port is opened above the micro-nano bubble flotation zone, and sheet-shaped and rod-shaped microplastics are moved out of the micro-nano bubble flotation zone through the primary sorting port.

[0011] A copper electrode plate is attached to the top of the lateral deviation zone of the thermophoretic microfluid, and a lateral temperature gradient is formed in the lateral deviation zone of the thermophoretic microfluid by heating the copper electrode plate, thereby finally driving microplastic particles of different particle sizes to undergo lateral thermophoretic coupling motion before entering the fine sorting module;

[0012] A micro-column array is arranged inside the fine sorting module. The fine sorting module is also connected to the sample outlet channel I and the sample outlet channel II at one end away from the primary sorting module. The sample outlet channel I and the sample outlet channel II are respectively provided with sample outlet I and sample outlet II. When microplastic particles flow through the micro-column array, microplastic particles larger than a critical size will produce lateral displacement after colliding with the micro-column array, thereby changing the motion trajectory. Microplastic particles smaller than the critical size will not produce lateral displacement after colliding with the micro-column array, and will still flow along the lateral streamline. After passing through the channel of the micro-column array, microplastic particles of different sizes are discharged from the sample outlet I or the sample outlet II.

[0013] The rear end of the micro-nano bubble flotation zone is also equipped with an inclined micro-nano filter screen, the upper end of the inclined micro-nano filter screen is far away from the lateral deviation zone of the thermophoretic microfluid, and the lower end is close to the lateral deviation zone of the thermophoretic microfluid, and the micro-nano bubble generating plate and the bubble column extend to one side of the bottom of the micro-nano filter screen;

[0014] The front, middle and rear sections of the primary sorting module are all provided with buffer and shock absorbing channels, wherein the sample inlet channel, the sheath liquid inlet channel and the fine sorting module on the separated sides of the front and rear buffer and shock absorbing channels are fixedly arranged, and the buffer and shock absorbing channel in the middle section separates the micro-nano bubble flotation area and the thermophoretic microfluid lateral deviation area, and the primary sorting module vibrates synchronously during the vibration process of the ultrasonic vibration device.

[0015] Preferably, the main structures of the primary sorting module and the fine sorting module and the sample inlet channel, the sheath liquid inlet channel, the sample outlet channel I and the sample outlet channel II are all made of polydimethylsiloxane material and are manufactured by a soft lithography casting process.

[0016] Preferably, the angle between the sample inlet channel and the sheath liquid inlet channel in the primary sorting module is 60°.

[0017] Preferably, the micropillars of the micropillar array are composed of a circular micropillar array, a triangular micropillar array, a rectangular micropillar array or a combination thereof.

[0018] Preferably, the microcolumn array adopts a circular microcolumn array, the diameter of the circular microcolumns of the circular microcolumn array is 60 μm, the spacing is 30 μm, the angle between the line connecting each row of circular microcolumns and the central axis of the fine sorting module is 2.86°, and the critical size is 10 μm.

[0019] Preferably, the angle formed by the sample outlet channel I and the sample outlet channel II at the end of the fine sorting module is 60°.

[0020] Preferably, the micro-column array extends to the inlet end of the sample outlet channel I, and three rows of micro-column arrays are arranged at the inlet end.

[0021] Preferably, the fine sorting module is composed of a plurality of periodic arrays arranged in a staggered manner, and the arrangement of the micro-column array in a subsequent periodic array is shifted downward by one row as a whole relative to a previous periodic array.

[0022] A method for sorting microplastics based on microfluidic thermophoresis coupled with deterministic lateral displacement, using the above-mentioned microplastic sorting device based on microfluidic thermophoresis coupled with deterministic lateral displacement, comprises the following steps:

[0023] S1: First, the bonded device is subjected to hydrophilic treatment, and then Tween alcohol solution is injected into the primary sorting module and the fine sorting module to completely infiltrate the internal channels;

[0024] S2: Prepare the sample solution and sheath solution of microplastic particles to be separated;

[0025] S3: Use a syringe pump to inject the sample solution into the sample inlet channel and inject the sheath solution into the sheath solution inlet channel;

[0026] S4: The sample solution and the sheath solution merge at the front end of the primary sorting module and flow into the primary sorting module;

[0027] S5: When the solution passes through the micro-nano bubble flotation zone of the primary sorting module, the micro-nano bubbles generated by the micro-nano bubble generating plate are used for primary sorting. At this time, micro-nano bubbles are attached to the surfaces of granular, flake and rod-shaped microplastics. Since the attachment area of ​​the granular microplastic surface is small, while the attachment area of ​​the other two forms of microplastics is large, the more micro-nano bubbles attached to the surface, the greater the buoyancy generated. This characteristic is used to perform primary sorting of flake and rod-shaped microplastics. The floating microplastics are collected through the primary sorting port, and the granular microplastics continue to move to the rear end with the flow of the solution;

[0028] S6: The granular microplastics after primary sorting then enter the lateral deviation zone of the thermophoretic microfluidic system. The microplastic solution is heated using a copper electrode plate, so that there are at least two temperature steps inside the solution. The microplastic particles in the solution move along the temperature gradient. At this time, microplastics of different particle sizes in the microplastic solution produce lateral displacement differences, and finally complete the lateral deviation before entering the fine sorting module.

[0029] S7: After the microplastic particles enter the fine sorting module after lateral displacement, the microplastic particles larger than the critical size collide and produce lateral displacement when passing through the microcolumn array, changing the movement trajectory. The microplastic particles smaller than the critical size do not produce lateral displacement after colliding with the microcolumn array and still flow along the original streamline. After being sorted by the fine sorting module, microplastic particles of different sizes move to different exits and are finally sorted.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention can not only sort microplastic particles of different particle sizes, but also sort microplastic particles of different shapes. The risk of blockage can be greatly reduced when the sorted granular microplastics enter the microcolumn array. At the same time, it can also eliminate the obstruction of granular microplastics by irregular-shaped microplastics in the microcolumn array, thereby ensuring the sorting efficiency of microplastic particles and improving the sorting accuracy of microplastic particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0033] Figure 2 Attached to the instruction manual Figure 1 A schematic diagram of the enlarged structure of the middle A area;

[0034] Figure 3 It is a schematic diagram of the structure of the primary sorting module and the fine sorting module of the present invention;

[0035] Figure 4 It is a schematic diagram of the structure of the micro-nano bubble flotation area and the thermophoretic microfluid lateral deviation area of ​​the present invention;

[0036] Figure 5 Schematic diagram of the staggered arrangement of several periodic arrays of the present invention.

[0037] In the figure: 1 primary sorting module, 2 fine sorting module, 3 sample inlet channel, 4 sheath liquid inlet channel, 5 micro-nano bubble flotation area, 6 thermophoresis microfluidic lateral deviation area, 7 micro-nano bubble generating plate, 8 bubble column, 9 primary sorting port, 10 copper electrode plate, 11 micro-column array, 12 sample outlet channel I, 13 sample outlet channel II, 14 sample outlet I, 15 sample outlet II, 16 micro-nano filter, 17 buffer shock absorption channel. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] See also Figure 1-5 , the present invention provides a technical solution:

[0040] Embodiment 1:

[0041] A microplastic sorting device based on microfluidic thermophoresis coupled deterministic lateral displacement, comprising a primary sorting module 1 and a fine sorting module 2, the primary sorting module 1 and the fine sorting module 2 are interconnected, and a sample inlet channel 3 and a sheath liquid inlet channel 4 are arranged at the front end of the primary sorting module 1;

[0042] The primary sorting module 1 includes a micro-nano bubble flotation zone 5 and a thermophoretic microfluid lateral deviation zone 6;

[0043] A micro-nano bubble generating plate 7 is provided at the bottom of the micro-nano bubble flotation zone 5, and an ultrasonic vibration device is also connected to the micro-nano bubble generating plate 7. The bubble column 8 arranged on the micro-nano bubble generating plate 7 extends into the micro-nano bubble flotation zone 5. A primary sorting port 9 is provided above the micro-nano bubble flotation zone 5, and the sheet-shaped and rod-shaped microplastics are moved out of the micro-nano bubble flotation zone 5 through the primary sorting port 9.

[0044] A copper electrode plate 10 is attached to the top of the lateral deviation zone 6 of the thermophoretic microfluid. By heating the copper electrode plate 10, a lateral temperature gradient is formed in the lateral deviation zone 6 of the thermophoretic microfluid, and finally the microplastic particles of different particle sizes are driven to undergo lateral thermophoretic coupling movement before entering the fine sorting module 2.

[0045] A micro-column array 11 is arranged inside the fine sorting module 2. The end of the fine sorting module 2 away from the primary sorting module 1 is also connected to the sample outlet channel Ⅰ12 and the sample outlet channel Ⅱ13. The sample outlet channel Ⅰ12 and the sample outlet channel Ⅱ13 are respectively provided with sample outlets Ⅰ14 and Ⅱ15. When the microplastic particles flow through the micro-column array 11, the microplastic particles larger than the critical size will produce lateral displacement after colliding with the micro-column array 11, thereby changing the motion trajectory. The microplastic particles smaller than the critical size will not produce lateral displacement after colliding with the micro-column array 11, and will still flow along the lateral streamline. After passing through the channel of the micro-column array 11, microplastic particles of different sizes are discharged from the sample outlet Ⅰ14 or the sample outlet Ⅱ15.

[0046] Among them, the rear end of the micro-nano bubble flotation zone 5 is also equipped with an inclined micro-nano filter 18, the upper end of the inclined micro-nano filter 16 is far away from the thermophoretic microfluid lateral deviation zone 6, and the lower end is close to the thermophoretic microfluid lateral deviation zone 6, and the micro-nano bubble generating plate 7 and the bubble column 8 extend to one side of the bottom of the micro-nano filter 16;

[0047] The front, middle and rear sections of the primary sorting module 1 are all provided with buffer shock absorbing channels 17, wherein the sample inlet channel 3, the sheath liquid inlet channel 4 and the fine sorting module 2 on the separated sides of the front and rear buffer shock absorbing channels 17 are fixedly arranged, and the buffer shock absorbing channel 17 in the middle section separates the micro-nano bubble flotation area 5 and the thermophoretic microfluid lateral deviation area 6, and the primary sorting module 1 vibrates synchronously during the vibration process of the ultrasonic vibration device.

[0048] In this embodiment, the main structures of the primary sorting module 1 and the fine sorting module 2, as well as the sample inlet channel 3, the sheath liquid inlet channel 4, the sample outlet channel I 12, and the sample outlet channel II 13 are all composed of polydimethylsiloxane material and are made by soft photolithography casting process. The material has good light transmittance, biocompatibility, good chemical inertness, toughness, etc. Different from the prior art, the primary sorting module 1 in the present invention adopts a front and back two-stage design of a micro-nano bubble flotation zone 5 and a thermophoretic microfluidic lateral deviation zone 6, wherein a GWNB type micro-nano aerator provided by Wuxi Gongyuan Environmental Technology Co., Ltd. is used to aerate the micro-nano bubble flotation zone 5, and the aerated micro The size of the nanobubbles can reach below 5 μm, and the aeration volume is relatively easy to adjust. The sorting accuracy can be effectively controlled by adjusting the aeration volume, so that the flake and rod-shaped microplastics can float effectively without causing the floating of granular microplastics, thereby losing the meaning of sorting. Microplastics of different forms can be sorted in the micro-nano bubble flotation zone 5. This sorting step is of great significance for the sorting of granular microplastics at the back end. The risk of blockage can be greatly reduced when the sorted granular microplastics enter the microcolumn array. At the same time, the obstruction of the granular microplastics by the irregular-shaped microplastics in the microcolumn array can be eliminated, thereby ensuring the sorting efficiency of the microplastic particles while improving the sorting accuracy of the microplastic particles. A thermophoretic microfluid lateral deviation zone 6 is also provided. After the granular microplastics enter the thermophoretic microfluid lateral deviation zone 6, they are heated by the copper electrode plate 10 to form a lateral temperature gradient in the thermophoretic microfluid lateral deviation zone 6, and finally drive the microplastic particles of different particle sizes to undergo lateral thermophoretic coupling movement before entering the fine sorting module 2. The significance of this step is to pre-sort the microplastic particles of different particle sizes, so that they are moved to a certain distance laterally at the front end of the fine sorting module 2, thereby reducing the probability of collision and deviation in the fine sorting module 2, thereby achieving the purpose of improving the sorting efficiency of the device. In addition, the rear end of the micro-nano bubble flotation zone 5 is also equipped with an inclined setting The micro-nano filter 18 is used to further intercept the irregular microparticles. At the same time, an ultrasonic vibration device is set in the primary sorting module 1 to prevent the micro-nano filter 18 from being blocked by ultrasonic vibration and promote the floating of bubbles. The special inclined structure of the micro-nano filter 18 is matched with the bubble generating device at the bottom thereof, which can promote the solution to pass through the through holes on the micro-nano filter 18. In addition, the solution can be defoamed before entering the fine sorting module 2. The fine sorting module 2 in this embodiment is composed of several periodic arrays arranged in a staggered manner. The arrangement of the micro-column array 11 in the latter periodic array is shifted downward by one row relative to the previous periodic array as a whole. Refer to the attached manual Figure 5The fine sorting module 2 forms a stepped downward periodic array. The advantage of this arrangement is that the sorting accuracy of microplastic particles in multiple periodic arrays can be effectively improved. The microcolumn array 11 adopts a circular microcolumn array. The diameter of the circular microcolumns in the circular microcolumn array is 60μm, the spacing is 30μm, and the angle between the connecting line of each row of circular microcolumns and the central axis of the fine sorting module is 2.86°. The critical size is 10μm. Since the arrangement of the microcolumn array 11 is in the prior art, it will not be repeated here.

[0049] Embodiment 2:

[0050] The micro-pillars of the micro-pillar array 11 are composed of a circular micro-pillar array, a triangular micro-pillar array, a rectangular micro-pillar array or a combination thereof.

[0051] The angle between the sample inlet channel 3 and the sheath liquid inlet channel 4 in the primary sorting module 1 is 60°.

[0052] The angle formed by the sample outlet channel I 12 and the sample outlet channel II 13 at the end of the fine sorting module 2 is 60°.

[0053] In this embodiment, the microcolumn array 11 can also be formed by microcolumns with different cross-sectional shapes or a combination of multiple microcolumn array shapes, which is also widely used in the prior art. At the same time, the inlet and outlet form a preset angle to ensure that the mixing and sorting process of the solution can be carried out accurately.

[0054] Embodiment three:

[0055] The micro-column array 11 extends to the inlet end of the sample outlet channel I 12, and three rows of micro-column arrays 11 are arranged at the inlet end. The advantage of such arrangement is that it can effectively prevent particle jumping caused by unstable flow resistance at the outlet.

[0056] A method for sorting microplastics based on microfluidic thermophoresis coupled with deterministic lateral displacement, using the above-mentioned microplastic sorting device based on microfluidic thermophoresis coupled with deterministic lateral displacement, comprises the following steps:

[0057] S1: First, the bonded device is subjected to hydrophilic treatment, and then Tween alcohol solution is injected into the primary sorting module 1 and the fine sorting module 2 to completely infiltrate the internal channels;

[0058] S2: Prepare the sample solution and sheath solution of microplastic particles to be separated;

[0059] S3: Use a syringe pump to inject the sample solution into the sample inlet channel 3 and inject the sheath solution into the sheath solution inlet channel 4;

[0060] S4: the sample solution and the sheath solution merge at the front end of the primary sorting module 1 and flow into the primary sorting module 1;

[0061] S5: When the solution passes through the micro-nano bubble flotation zone 5 of the primary sorting module 1, the micro-nano bubbles generated by the micro-nano bubble generating plate 7 are used for primary sorting. At this time, micro-nano bubbles are attached to the surfaces of granular, sheet-shaped and rod-shaped microplastics. Since the attachment area of ​​the granular microplastic surface is small, while the attachment area of ​​the other two forms of microplastics is large, the more micro-nano bubbles attached to the surface, the greater the buoyancy generated. The primary sorting of sheet-shaped and rod-shaped microplastics is carried out through this characteristic, and the floating microplastics are collected through the primary sorting port 9, and the granular microplastics continue to move to the rear end with the flow of the solution;

[0062] S6: The granular microplastics after primary sorting then enter the thermophoretic microfluidic lateral deviation zone 6, and the microplastic solution is heated using a copper electrode plate 10, so that there are at least two temperature step changes inside the solution, and the microplastic particles in the solution move along the temperature gradient. At this time, microplastics of different particle sizes in the microplastic solution produce lateral displacement differences, and finally complete the lateral deviation before entering the fine sorting module 2;

[0063] S7: After the microplastic particles enter the fine sorting module 2 after lateral displacement, the microplastic particles larger than the critical size collide and produce lateral displacement when passing through the microcolumn array 11, changing the movement trajectory. The microplastic particles smaller than the critical size do not produce lateral displacement after colliding with the microcolumn array 11, and still flow along the original streamline. After being sorted by the fine sorting module 2, microplastic particles of different sizes move to different exits and are finally sorted.

[0064] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A microplastic sorting device based on microfluidic thermophoresis coupled deterministic lateral displacement, comprising a primary sorting module and a fine sorting module, characterized in that: The primary sorting module and the fine sorting module are connected to each other, and a sample inlet channel and a sheath liquid inlet channel are arranged at the front end of the primary sorting module; The primary sorting module includes a micro-nano bubble flotation zone and a thermophoretic microfluid lateral deviation zone; A micro-nano bubble generating plate is arranged at the bottom of the micro-nano bubble flotation zone, and an ultrasonic vibration device is also connected to the micro-nano bubble generating plate. The bubble columns arranged on the micro-nano bubble generating plate extend into the micro-nano bubble flotation zone. A primary sorting port is opened above the micro-nano bubble flotation zone, and sheet-shaped and rod-shaped microplastics are moved out of the micro-nano bubble flotation zone through the primary sorting port. A copper electrode plate is attached to the top of the lateral deviation zone of the thermophoretic microfluid, and a lateral temperature gradient is formed in the lateral deviation zone of the thermophoretic microfluid by heating the copper electrode plate, thereby finally driving microplastic particles of different particle sizes to undergo lateral thermophoretic coupling motion before entering the fine sorting module; A micro-column array is arranged inside the fine sorting module, and the fine sorting module is also connected to the sample outlet channel I and the sample outlet channel II at one end away from the primary sorting module. The sample outlet channel I and the sample outlet channel II are provided with sample outlet I and sample outlet II in a one-to-one correspondence. When microplastic particles flow through the micro-column array, microplastic particles larger than a critical size produce lateral displacement after colliding with the micro-column array, thereby changing the motion trajectory. Microplastic particles smaller than the critical size do not produce lateral displacement after colliding with the micro-column array, and still flow along the lateral streamline. After passing through the channel of the micro-column array, microplastic particles of different sizes are discharged from the sample outlet I or the sample outlet II; The rear end of the micro-nano bubble flotation zone is also equipped with an inclined micro-nano filter screen, the upper end of the inclined micro-nano filter screen is far away from the lateral deviation zone of the thermophoretic microfluid, and the lower end is close to the lateral deviation zone of the thermophoretic microfluid, and the micro-nano bubble generating plate and the bubble column extend to one side of the bottom of the micro-nano filter screen; The front, middle and rear sections of the primary sorting module are all provided with buffer and shock absorbing channels, wherein the sample inlet channel, the sheath liquid inlet channel and the fine sorting module on the separated sides of the front and rear buffer and shock absorbing channels are fixedly arranged, and the buffer and shock absorbing channel in the middle section separates the micro-nano bubble flotation area and the thermophoretic microfluid lateral deviation area, and the primary sorting module vibrates synchronously during the vibration process of the ultrasonic vibration device.

2. According to claim 1, a microplastic sorting device based on microfluidic thermophoresis coupled deterministic lateral displacement is characterized by: The main structures of the primary sorting module and the fine sorting module and the sample inlet channel, the sheath liquid inlet channel, the sample outlet channel I and the sample outlet channel II are all made of polydimethylsiloxane material and are manufactured by a soft photolithography casting process.

3. A microplastic sorting device based on microfluidic thermophoresis coupled deterministic lateral displacement according to claim 1 or 2, characterized in that: The angle between the sample inlet channel and the sheath liquid inlet channel in the primary sorting module is 60°.

4. A microplastic sorting device based on microfluidic thermophoresis coupled deterministic lateral displacement according to claim 3, characterized in that: The micro-pillars of the micro-pillar array are composed of a circular micro-pillar array, a triangular micro-pillar array, a rectangular micro-pillar array or a combination thereof.

5. The microplastic sorting device based on microfluidic thermophoresis coupled deterministic lateral displacement according to claim 4, characterized in that: The microcolumn array adopts a circular microcolumn array, the diameter of the circular microcolumns of the circular microcolumn array is 60 μm, the spacing is 30 μm, the angle between the connecting line of each row of circular microcolumns and the central axis of the fine sorting module is 2.86°, and the critical size is 10 μm.

6. The microplastic sorting device based on microfluidic thermophoresis coupled deterministic lateral displacement according to claim 5, characterized in that: The angle formed by the sample outlet channel I and the sample outlet channel II at the end of the fine sorting module is 60°.

7. The microplastic sorting device based on microfluidic thermophoresis coupled deterministic lateral displacement according to claim 6, characterized in that: The micro-column array extends to the inlet end of the sample outlet channel I, and three rows of micro-column arrays are arranged at the inlet end.

8. The microplastic sorting device based on microfluidic thermophoresis coupled deterministic lateral displacement according to claim 7, characterized in that: The fine sorting module is composed of a plurality of periodic arrays arranged in a staggered manner, and the arrangement of the micro-pillar array in a subsequent periodic array is shifted downward by one row relative to the previous periodic array as a whole.

9. A method for sorting microplastics based on microfluidic thermophoresis coupled with deterministic lateral displacement, using the microplastic sorting device based on microfluidic thermophoresis coupled with deterministic lateral displacement according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1: First, the bonded device is subjected to hydrophilic treatment, and then Tween alcohol solution is injected into the primary sorting module and the fine sorting module to completely infiltrate the internal channels; S2: Prepare the sample solution and sheath solution of microplastic particles to be separated; S3: Use a syringe pump to inject the sample solution into the sample inlet channel and inject the sheath solution into the sheath solution inlet channel; S4: The sample solution and the sheath solution merge at the front end of the primary sorting module and flow into the primary sorting module; S5: When the solution passes through the micro-nano bubble flotation zone of the primary sorting module, the micro-nano bubbles generated by the micro-nano bubble generating plate are used for primary sorting. At this time, micro-nano bubbles are attached to the surfaces of granular, flake and rod-shaped microplastics. Since the attachment area of ​​the granular microplastic surface is small, while the attachment area of ​​the other two forms of microplastics is large, the more micro-nano bubbles attached to the surface, the greater the buoyancy generated. This characteristic is used to perform primary sorting of flake and rod-shaped microplastics. The floating microplastics are collected through the primary sorting port, and the granular microplastics continue to move to the rear end with the flow of the solution; S6: The granular microplastics after primary sorting then enter the lateral deviation zone of the thermophoretic microfluidic system. The microplastic solution is heated using a copper electrode plate, so that there are at least two temperature steps inside the solution. The microplastic particles in the solution move along the temperature gradient. At this time, microplastics of different particle sizes in the microplastic solution produce lateral displacement differences, and finally complete the lateral deviation before entering the fine sorting module. S7: After the microplastic particles enter the fine sorting module after lateral displacement, the microplastic particles larger than the critical size collide and produce lateral displacement when passing through the microcolumn array, changing the movement trajectory. The microplastic particles smaller than the critical size do not produce lateral displacement after colliding with the microcolumn array and still flow along the original streamline. After being sorted by the fine sorting module, microplastic particles of different sizes move to different exits and are finally sorted.

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