Particle sorting micro-fluidic chip based on viscoelastic iron fluid and preparation method thereof

Abstract

The invention provides a particle sorting micro-fluidic chip based on viscoelastic iron fluid and a preparation method of the particle sorting micro-fluidic chip. The particle sorting micro-fluidic chip comprises a first inlet, a branch channel, a magnet, a first sorting module and a second sorting module, the first inlet is connected with one end of the branch channel, and the first sorting module and the second sorting module are connected with the other end of the branch channel; the magnet is positioned between the first sorting module and the second sorting module; a mixed solution of viscoelastic iron fluid and two kinds of particles is injected from the first inlet and equivalently flows into the first sorting module and the second sorting module through the branch channel. The method can realize continuous and sheath-free separation of particles with different sizes, and has the advantages of high flux, small structure size, no need of magnetic bead modification, simple operation and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of CTC high-throughput sorting, and in particular to a particle sorting microfluidic chip based on viscoelastic ferrofluid and a preparation method thereof, in particular to a particle sorting microfluidic chip based on viscoelastic ferrofluid. Background Art

[0002] Cancer metastasis is the main cause of cancer-related deaths. If patients with early-stage cancer metastasis can receive timely treatment, the number of cancer deaths will be reduced by about 30%. Therefore, developing early cancer diagnosis and treatment technologies and studying the mechanism of cancer metastasis are important means for humans to fight cancer in the future. However, the tumor burden of patients with early-stage cancer metastasis is usually very low, making it difficult to locate metastatic lesions through traditional imaging methods, and it is impossible to extract tumor cells for analysis through puncture biopsy methods, which greatly limits the molecular diagnosis of early-stage metastatic tumors, precision treatment, and research on the mechanisms of cancer occurrence, development, and metastasis.

[0003] Circulating tumor cells (CTCs) refer to seed cells that fall off from primary or metastatic tumor lesions, undergo epithelial-mesenchymal transition and enter the peripheral blood circulation. A large number of studies have shown that CTCs already exist in the patient's peripheral blood in the early stages of cancer metastasis. Therefore, CTC liquid biopsy technology can break through the limitation that traditional tissue biopsy is only applicable to solid tumor tissues that can be detected by imaging. At the same time, with the advantages of convenient sampling, dynamic observation and non-invasiveness, it can comprehensively, real-time and accurately display the biological information of the tumor, showing unique advantages in the early diagnosis and treatment of cancer and prognosis evaluation.

[0004] However, due to the interference of high concentrations of blood cells in whole blood samples, accurate and rapid separation of CTCs still faces huge challenges. Cell sorting technology can be divided into two categories: active manipulation and passive manipulation. Active manipulation cell sorting technology relies on the action of external physical fields, and usually requires the use of complex precision instruments and equipment to complete the sorting of CTCs. Some active manipulation technologies also require magnetic beads and fluorescent labeling of cells. Therefore, active manipulation cell sorting methods usually face problems such as high technical costs, difficulty in small modularization, and long operation time. Passive manipulation cell sorting technology can avoid the disadvantages of the above-mentioned active manipulation methods, but this type of technology usually requires the introduction of sheath flow, which reduces the concentration of cells after sorting and the portability of operation. In addition, passive sorting technology also has problems such as low sorting purity, high shear stress, and severe clogging.

[0005] The patent document with the public number CN109550531A discloses a magnetic size-dependent microfluidic chip, including a cover sheet and a substrate, the cover sheet is located directly above the substrate, the cover sheet and the substrate are sealed and connected, a magnetophoresis separation structure and a size sorting channel for capturing magnetic microspheres of different sizes are opened on the lower surface of the cover sheet, the magnetophoresis separation structure includes a buffer moving channel, a sample moving channel, a confluence channel, a capture channel and a waste liquid discharge channel, the buffer moving channel and the sample moving channel merge at one end of the confluence channel, and one end of the waste liquid discharge channel and the capture channel merge at the other end of the confluence channel. The other end of the capture channel is connected to the entrance of the size sorting channel, a magnet is provided on the cover sheet, the magnet is located above the confluence channel, and the magnet is located on one side of the projection of the confluence channel on the upper surface of the cover sheet, the capture channel extends in the direction close to the magnet, and the waste liquid discharge channel extends in the direction away from the magnet, and a buffer injection port, a sample injection port, a first discharge port and a second discharge port are provided on the cover sheet, the buffer injection port is connected to the buffer movement channel, the sample injection port is connected to the sample movement channel, the first discharge port is connected to the waste liquid discharge channel, and the second discharge port is connected to the size sorting channel outlet. However, the patent document still has problems such as low sorting purity, high shear stress and serious blockage.

[0006] The patent document with publication number US20220379312A1 discloses a magnetic separation microfluidic chip, and specifically discloses a magnetic separation microfluidic chip, including a substrate, a chip model material layer, a microchannel unit and a magnetic separation unit, the chip model material layer is arranged on the substrate, the microchannel unit and the magnetic separation unit are both arranged in the chip model material layer, the microchannel unit includes a separation channel and a magnetic pole channel; the separation channel has multiple separation channel entrances and multiple separation channel exits; the magnetic separation unit includes a permanent magnet, a high magnetic permeability alloy and a magnetic pole array arranged in the magnetic pole channel, and the high magnetic permeability alloy is used to conduct the magnetic field of the permanent magnet to the magnetic pole array, so that the magnetic pole array generates a magnetic field with opposite polarity at the left and right positions of the separation channel. However, the patent document still has problems such as low separation purity, high shear stress and severe blockage. Summary of the invention

[0007] In view of the defects in the prior art, the object of the present invention is to provide a particle sorting microfluidic chip based on viscoelastic ferrofluid and a preparation method thereof.

[0008] A particle sorting microfluidic chip based on viscoelastic ferrofluid provided by the present invention comprises: a first inlet, a branch channel, a magnet, a first sorting module and a second sorting module;

[0009] The first inlet is connected to one end of the branch channel, and the first sorting module and the second sorting module are connected to the other end of the branch channel;

[0010] The magnet is located between the first sorting module and the second sorting module;

[0011] A mixed solution of viscoelastic ferrofluid and two kinds of particles is injected from the first inlet and flows into the first sorting module and the second sorting module in equal amounts through the branch channel.

[0012] Preferably, the first sorting module and the second sorting module have the same structure, and the first sorting module and the second sorting module are symmetrically arranged in parallel.

[0013] Preferably, the first sorting module comprises a first straight channel section, a first enlarged section, a second straight channel section, a second enlarged section, a first outlet and a second outlet;

[0014] One end of the first straight channel section is connected to the other end of the branch channel, and the other end of the first straight channel section is connected to one end of the first amplifying section;

[0015] One end of the second straight channel section is connected to the other end of the first enlarged section, and the other end of the second straight channel section is connected to one end of the second enlarged section;

[0016] The first outlet and the second outlet are connected to the other end of the second amplifying section; and the magnet is located on one side of the second straight channel section.

[0017] Preferably, the viscoelastic ferrofluid is prepared by adding a water-based ferrofluid into a polyethylene oxide solution.

[0018] The present invention also provides a method for preparing a particle sorting microfluidic chip based on viscoelastic ferrofluid, which is used to prepare the above-mentioned particle sorting microfluidic chip based on viscoelastic ferrofluid, comprising the following steps:

[0019] Step 1: Mix polydimethylsiloxane and polydimethylsiloxane curing agent according to a preset mass ratio, stir with a glass rod for a preset time, mix thoroughly and place in a vacuum drying dish, and remove bubbles in the polydimethylsiloxane mixture by vacuuming;

[0020] Step 2: placing the silicon wafer with the channel pattern of the microfluidic chip in a cell culture dish, and slowly introducing the polydimethylsiloxane mixture after the bubbles are removed in step 1, and after the polydimethylsiloxane mixture completely and evenly covers the surface of the silicon wafer, placing it in a vacuum drying dish again to evacuate and remove bubbles between the silicon wafer and the bottom of the cell culture dish;

[0021] Step 3: placing the cell culture dish in step 2 in an oven for curing, separating the cured polydimethylsiloxane from the silicon wafer, cutting it into a preset shape, cutting a through hole for placing a magnet, and punching with a puncher to form a first inlet, a first outlet, and a second outlet;

[0022] Step 4: Use transparent tape to remove the pattern surface of the polydimethylsiloxane and the surface of the glass slide in step 3, and put the polydimethylsiloxane and the glass slide into a plasma cleaning machine;

[0023] Step 5: Turn on the vacuum pump connected to the plasma cleaning machine in step 4. When the pressure in the chamber of the plasma cleaning machine drops to a preset pressure, stop evacuating and turn on the glow. When the preset glow appears in the vacuum chamber, start timing. After the preset time, stop the glow and take out the two.

[0024] Step 6: The patterned surface of the polydimethylsiloxane in step 5 is tightly attached to the glass slide, and after lightly pressing to remove bubbles between the surfaces, the surface is placed on a heating table to further strengthen the bonding effect;

[0025] Step 7: Insert the polytetrafluoroethylene capillary into the hole of the microfluidic chip, pour the polydimethylsiloxane mixture at the position, and place it in an oven to enhance the sealing performance of the entrance and exit positions;

[0026] Step 8: Place the magnets in the through-holes of the microfluidic chip.

[0027] Preferably, in step 1, the amounts of polydimethylsiloxane and polydimethylsiloxane curing agent used are 30 g and 3 g respectively, and the vacuuming time is 50 minutes to 80 minutes.

[0028] Preferably, in step 2, the vacuuming time is 20 minutes to 35 minutes.

[0029] Preferably, in step 3, the oven temperature is set to 80° C. and the time is 50 minutes to 70 minutes.

[0030] Preferably, in step 6, the temperature of the heating stage is set to 85° C., and the time is 40 minutes to 50 minutes.

[0031] Preferably, in step 7, the oven temperature is set to 80° C. and the time is 50 minutes to 70 minutes.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The microfluidic chip of the present invention uses viscoelastic ferrofluid as a particle transport medium and utilizes elastic force to achieve pre-focusing of particles without introducing sheath fluid, thereby increasing the particle concentration in the collection solution and avoiding the extrusion of particles and the channel wall.

[0034] 2. The magnetic field sorting module of the microfluidic chip of the present invention uses the ferrofluidic method to sort microspheres, without the need for magnetic bead labeling, thereby reducing the time and cost associated with labeling. In addition, the module is simple to operate and low in cost, and only a permanent magnet is required to achieve sorting.

[0035] 3. The microfluidic chip of the present invention utilizes the symmetry of the channel structure and the spatial magnetic field distribution to efficiently sort particles in the first sorting module and the second sorting module at the same time, thereby improving the sorting throughput.

[0036] 4. The microfluidic chip of the present invention uses the force of fluid acting on particles to achieve sorting, which effectively reduces the probability of particles directly colliding with the microstructure. When this technology is applied to sorting biological particles, it can reduce damage to biological particles and improve integrity. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0038] Figure 1 Schematic diagram of the structure of the microfluidic chip in an embodiment of the present invention.

[0039] Figure 2 Schematic diagram of the movement of particles in the first straight channel section in an embodiment of the present invention.

[0040] Figure 3 Schematic diagram of the movement of particles in the second straight channel section in an embodiment of the present invention.

[0041] Figure 4 Schematic diagram of the overall structure of the microfluidic chip in an embodiment of the present invention.

[0042] Figure 5 It is a schematic diagram of the local structure of the first amplification section in an embodiment of the present invention.

[0043] Figure 6 It is a schematic diagram of the local structure of the second amplification section in an embodiment of the present invention.

[0044] The figure shows:

[0045] First inlet 1 Second straight channel section 43

[0046] Branch channel 2 Second amplification section 44

[0047] Magnet 3 First outlet 45

[0048] First sorting module 4 Second exit 46

[0049] First straight channel section 41 Second sorting module 5

[0050] First amplification section 42 DETAILED DESCRIPTION

[0051] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0052] Embodiment 1:

[0053] like Figure 1-6 As shown, this embodiment provides a particle sorting microfluidic chip based on viscoelastic ferrofluid, comprising: a first inlet 1, a branch channel 2, a magnet 3, a first sorting module 4 and a second sorting module 5; the first inlet 1 is connected to one end of the branch channel 2, and the first sorting module 4 and the second sorting module 5 are connected to the other end of the branch channel 2; the magnet 3 is located between the first sorting module 4 and the second sorting module 5; a mixed solution of the viscoelastic ferrofluid and the two particles is injected from the first inlet 1, and flows into the first sorting module 4 and the second sorting module 5 in equal amounts through the branch channel 3. The first sorting module 4 and the second sorting module 5 have the same structure, and the first sorting module 4 and the second sorting module 5 are symmetrically arranged in parallel. The viscoelastic ferrofluid is prepared by adding a water-based ferrofluid to a polyethylene oxide solution.

[0054] The first sorting module 4 includes a first straight channel section 41, a first enlarging section 42, a second straight channel section 43, a second enlarging section 44, a first outlet 45 and a second outlet 46; one end of the first straight channel section 41 is connected to the other end of the branch channel 2, and the other end of the first straight channel section 41 is connected to one end of the first enlarging section 42; one end of the second straight channel section 43 is connected to the other end of the first enlarging section 42, and the other end of the second straight channel section 43 is connected to one end of the second enlarging section 44; the first outlet 45 and the second outlet 46 are connected to the other end of the second enlarging section 44; the magnet 3 is located on one side of the second straight channel section 43.

[0055] The flow cross section of the first enlarged section 42 gradually increases along the flow direction of the fluid and gradually increases along a side direction perpendicular to the flow direction. The first enlarged section 42 is used to connect the first straight channel section 41 with a smaller width and the second straight channel section 43 with a larger width, so as to widen the width of the second straight channel section 43 and provide sufficient space for the lateral migration of particles.

[0056] The flow cross section of the second enlarged section 44 gradually increases along the flow direction of the fluid, and gradually increases along the two sides perpendicular to the flow direction. The second enlarged section 43 is currently used to further expand the lateral position difference of the particles, because the small-sized and large-sized particles have already produced a certain lateral position difference when passing through the second straight channel section 43. In order to further improve the sorting effect, the second enlarged section 44 is set to increase the lateral distance between the large and small particles.

[0057] This embodiment also provides a method for preparing a particle sorting microfluidic chip based on viscoelastic ferrofluid, which is used to prepare the above-mentioned particle sorting microfluidic chip based on viscoelastic ferrofluid, comprising the following steps:

[0058] Step 1: Mix polydimethylsiloxane and polydimethylsiloxane curing agent according to a preset mass ratio, stir with a glass rod for a preset time, and place in a vacuum drying dish after fully mixing, and remove bubbles in the polydimethylsiloxane mixture by vacuuming; the amounts of polydimethylsiloxane and polydimethylsiloxane curing agent are 30g and 3g respectively, and the vacuuming time is 50 minutes to 80 minutes;

[0059] Step 2: Place the silicon wafer with the channel pattern of the microfluidic chip in a cell culture dish, and slowly introduce the polydimethylsiloxane mixture after the bubbles are removed in step 1. After the polydimethylsiloxane mixture completely and evenly covers the surface of the silicon wafer, place it in a vacuum drying dish again to remove the bubbles between the silicon wafer and the bottom of the cell culture dish; the vacuuming time is 20 minutes to 35 minutes;

[0060] Step 3: Place the cell culture dish in step 2 in an oven for curing, separate the cured polydimethylsiloxane from the silicon wafer, cut it into a preset shape, cut a through hole for placing the magnet 3, and use a puncher to punch holes to form a first inlet 1, a first outlet 45, and a second outlet 46; the oven temperature is set to 80°C, and the time is 50 minutes to 70 minutes;

[0061] Step 4: Use transparent tape to remove the pattern surface of polydimethylsiloxane and the surface of the glass slide in step 3, and put the polydimethylsiloxane and the glass slide into a plasma cleaning machine;

[0062] Step 5: Turn on the vacuum pump connected to the plasma cleaning machine in step 4. When the pressure in the chamber of the plasma cleaning machine drops to the preset pressure, stop evacuating and turn on the glow. When the preset glow appears in the vacuum chamber, start timing. After the preset time, stop the glow and take out the two.

[0063] Step 6: The patterned surface of the polydimethylsiloxane in step 5 is tightly attached to the glass slide, and after lightly pressing to remove bubbles between the surfaces, it is placed on a heating table to further strengthen the bonding effect; the temperature of the heating table is set to 85°C, and the time is 40 minutes to 50 minutes;

[0064] Step 7: insert the polytetrafluoroethylene capillary into the hole of the microfluidic chip, and pour the polydimethylsiloxane mixture at the position, and place it in an oven to enhance the sealing performance of the entrance and exit positions; the oven temperature is set to 80°C, and the time is 50 minutes to 70 minutes;

[0065] Step 8: Place the magnet 3 in the through hole of the microfluidic chip.

[0066] Silicon wafers with microfluidic chip channel patterns are prepared by the following process:

[0067] The microfluidic chip is prepared by soft lithography, that is, the channel shape is transferred to the photoresist by photolithography on the silicon wafer, and then PDMS is poured on the silicon wafer and cured. All channels in all microfluidic chips are completed at the same time, and the channel pattern includes: branch channel 2, first straight channel section 41, first enlarged section 42, second straight channel section 43, second enlarged section 44, and the channel included in the second sorting module 5.

[0068] In this embodiment, the microfluidic chip uses viscoelastic ferrofluid as a particle transport medium and utilizes elastic force to achieve pre-focusing of particles without introducing sheath fluid, thereby increasing the particle concentration in the collection solution and avoiding the squeezing of particles and the channel wall.

[0069] In this embodiment, the magnetic field sorting module of the microfluidic chip uses ferrofluidic dynamics to sort microspheres, without the need for magnetic bead labeling, thereby reducing the time and cost associated with labeling. In addition, the module is simple to operate and low in cost, and only requires a permanent magnet to achieve sorting.

[0070] In this embodiment, the microfluidic chip utilizes the symmetry of the channel structure and the spatial magnetic field distribution to efficiently sort particles in the sorting module 1 and the sorting module 2 at the same time, thereby improving the sorting throughput.

[0071] In this embodiment, the microfluidic chip uses the force of fluid acting on particles to achieve sorting, which effectively reduces the probability of particles directly colliding with the microstructure. When this technology is applied to sorting biological particles, it can reduce damage to the biological particles and improve their integrity.

[0072] Embodiment 2:

[0073] Those skilled in the art may understand this embodiment as a more specific description of Embodiment 1.

[0074] The present embodiment provides a particle sorting microfluidic chip based on viscoelastic ferrofluid, the microfluidic chip comprises a first inlet 1, a branch channel 2, a NdFeB permanent magnet 3, a first sorting module 4 and a second sorting module 5, wherein the first sorting module 4 and the second sorting module 5 have the same structure and are symmetrically arranged in parallel, and the first sorting module 4 is composed of a first straight channel section 41, a first enlarged section 42, a second straight channel section 43, a second enlarged section 44, a first outlet 45 and a second outlet 46. The channel height in the microfluidic chip is 50 μm, the length and width of the first straight channel section 41 are 20 mm and 50 μm respectively, the length and width of the second straight channel section 43 are 15 mm and 500 μm respectively, and the width of the enlarged section is 1 mm.

[0075] The viscoelastic ferrofluid generates an elastic force on the particles in the first straight channel section 41, driving the particles to gradually focus toward the center of the channel, so that the two particles have the same lateral position when they reach the end of the first straight channel section 41. The elastic force of the viscoelastic ferrofluid on the particles can be expressed by the following formula:

[0076]

[0077] Among them, a p is the particle diameter, c is the PEO concentration, Q is the flow rate at the first inlet 1, y p is the lateral coordinate of the particle in the channel (the origin of the coordinate is located at the center line of the channel), e j is a transverse unit vector, w is the width of the first straight channel section 41, and h is the channel height.

[0078] The NdFeB permanent magnet 3 will generate a non-uniform magnetic field in the second straight channel section 43, thereby generating a negative magnetophoretic force on the particles, driving the particles to move in the opposite direction. The magnetophoretic force is related to the volume of the particles, so that two particles of different sizes will form a lateral position difference in the second straight channel section 43, and the lateral position difference will be further amplified when the particles pass through the second amplification section 44, so as to achieve the separation of the two particles of different sizes. The negative magnetophoretic force on the particles can be expressed by the following formula:

[0079]

[0080] Among them, V p is the particle volume, μ0 is the vacuum magnetic permeability, M is the effective magnetization intensity of the ferrofluid, and H is the magnetic field intensity.

[0081] The viscoelastic ferrofluid injected from the first inlet 1 is prepared by adding a water-based ferrofluid to a polyethylene oxide (PEO) solution, the diameter of the nanomagnetic beads is 8nm-12nm, the concentration of the magnetic beads is 0.11% v / v, and the PEO solution is prepared by dissolving 2000kDa PEO powder in deionized water, and the solubility is 0.1% w / w-0.2% w / w.

[0082] The flow rate of the first inlet 1 is 1.5 mL / h-3 mL / h, and the length of the magnet 3 is 4 mm-6 mm.

[0083] This embodiment provides a method for preparing the above-mentioned microfluidic chip, comprising the following steps:

[0084] Step 1, mixing polydimethylsiloxane and polydimethylsiloxane curing agent in a mass ratio of 10:1, and stirring with a glass rod for 7 minutes to 10 minutes, and placing in a vacuum drying dish after fully mixing, and removing bubbles in the polydimethylsiloxane mixture by vacuuming;

[0085] Step 2, placing the silicon wafer with the channel pattern of the microfluidic chip in a cell culture dish, and slowly introducing the polydimethylsiloxane mixed solution after the bubbles are removed in step 1, and after the polydimethylsiloxane mixed solution completely and evenly covers the surface of the silicon wafer, placing it in a vacuum drying dish again to evacuate and remove bubbles between the silicon wafer and the bottom of the cell culture dish;

[0086] Step 3, placing the cell culture dish in step 2 in an oven for curing, separating the cured polydimethylsiloxane from the silicon wafer, cutting it into a regular rectangular shape, cutting out a rectangular through hole for placing the magnet 3, and using a puncher to punch holes at the positions of the first inlet 1, the first outlet 45 and the second outlet 46;

[0087] Step 4: Use transparent tape to remove the pattern surface of the polydimethylsiloxane and the surface of the glass slide in step 3, and put the polydimethylsiloxane and the glass slide into a plasma cleaning machine;

[0088] Step 5, turn on the vacuum pump connected to the plasma cleaning machine in step 4, and when the pressure in the plasma cleaning machine chamber drops to 200Pa, stop evacuating and turn on the glow. Start timing when a purple-red glow appears in the vacuum chamber, stop the glow after 45 seconds and take out the two;

[0089] Step 6, closely attaching the patterned surface of the polydimethylsiloxane in step 5 to the glass slide, lightly pressing to remove bubbles between the surfaces, and then placing on a heating table to further strengthen the bonding effect;

[0090] Step 7, inserting a polytetrafluoroethylene capillary into the punched hole of the microfluidic chip, pouring a small amount of polydimethylsiloxane mixed liquid at the position, and placing it in an oven to enhance the sealing performance of the inlet and outlet positions;

[0091] Step 8: Place the NdFeB permanent magnet 3 in the rectangular through hole of the microfluidic chip.

[0092] In step 1, the amount of polydimethylsiloxane and polydimethylsiloxane curing agent is 30g and 3g respectively, and the vacuuming time is 50 minutes to 80 minutes. The vacuuming time in step 2 is 20 minutes to 35 minutes. In step 3, the oven temperature is set to 80°C for 50 minutes to 70 minutes. In step 6, the temperature of the heating table is set to 85°C for 40 minutes to 50 minutes. In step 7, the oven temperature is set to 80°C for 50 minutes to 70 minutes.

[0093] This embodiment discloses a particle sorting microfluidic chip based on viscoelastic ferrofluid, comprising a first inlet 1, a branch channel 2, a NdFeB permanent magnet 3, a first sorting module 4 and a second sorting module 5, wherein the first sorting module 4 and the second sorting module 5 have the same structure and are symmetrically arranged in parallel, and the first sorting module 4 is composed of a first straight channel section 41, a first amplifying section 42, a second straight channel section 43, a second amplifying section 44, a first outlet 45 and a second outlet 46. A mixed solution of viscoelastic ferrofluid and two particles is injected from the first inlet 1, and flows into the first sorting module 4 and the second sorting module 5 in equal amounts through the branch channel 2. The particles in the first sorting module 4 will be focused on the centerline position of the channel in the first straight channel section 41 due to the elastic force of the viscoelastic ferrofluid, and will flow into the second straight channel section 43 after passing through the first amplifying section 42. The NdFeB permanent magnet 3 will form a non-uniform magnetic field in the second straight channel section 43, thereby generating a negative magnetophoretic force on the particles, driving the particles to move in the opposite direction. Negative magnetophoretic force is related to the volume of particles, so two particles of different sizes will form a lateral position difference in the second straight channel section 43, and will be further amplified in the second amplification section 44, so that large-sized particles and small-sized particles flow out from the first outlet 45 and the second outlet 46 respectively, thereby achieving particle sorting. The present invention can achieve continuous, sheath-free sorting of particles of different sizes, and has the advantages of high throughput, small structural size, no need for magnetic bead modification, and simple operation.

[0094] In order to overcome the technical bottleneck of existing sorting methods, this embodiment provides a microfluidic chip that can conveniently sort micron-sized particles without a sheath, provide technical support for the separation of biological particles such as CTCs, and promote further research and clinical application of CTC liquid biopsy technology.

[0095] Embodiment 3:

[0096] Those skilled in the art may understand this embodiment as a more specific description of Embodiment 1.

[0097] like Figure 1 As shown, this embodiment proposes a particle sorting microfluidic chip based on viscoelastic ferrofluid, which mainly includes a first inlet 1, a branch channel 2, a NdFeB permanent magnet 3, a first sorting module 4 and a second sorting module 5, wherein the first sorting module 4 and the second sorting module 5 have the same structure and are symmetrically arranged in parallel, and the first sorting module 4 is composed of a first straight channel section 41, a first amplifying section 42, a second straight channel section 43, a second amplifying section 44, a first outlet 45 and a second outlet 46. A sample of a mixture of two particles of different sizes and viscoelastic ferrofluid is injected into the microfluidic chip from the first inlet 1 by a syringe pump.

[0098] like Figure 2 As shown, the positions of the two particles of different sizes in the cross section at the beginning of the first straight channel section 41 are randomly distributed. Under the action of the elastic force, the particles are gradually focused to the center of the channel, so that the two particles have the same lateral position when they reach the end of the first straight channel section 41.

[0099] like Figure 3 As shown, after the particles flow out of the first straight channel section 41, they will enter the second straight channel section 43 through the first enlarged section 42. The NdFeB permanent magnet 3 will generate a non-uniform magnetic field in the second straight channel section 43, attracting the viscoelastic ferrofluid to move toward the NdFeB permanent magnet 3, thereby generating a negative magnetophoretic force on the particles, driving the particles to move in the opposite direction. Since the negative magnetophoretic force is related to the volume of the particles, large-sized particles will produce a larger lateral displacement and eventually flow out of the first outlet 45, while small-sized particles will flow out of the second outlet 46, thereby achieving the separation of two particles of different sizes.

[0100] like Figure 4-Figure 6 As shown, the length and width of the first straight channel section 41 are 20 mm and 50 μm respectively, the length and width of the second straight channel section 43 are 15 mm and 500 μm respectively, and the width of the second enlarged section 44 is 1 mm.

[0101] Working principle of the present invention:

[0102] A mixed solution of viscoelastic ferrofluid and two particles of different sizes is injected from the first inlet 1, and flows into the first sorting module 4 and the second sorting module 5 in equal amounts through the branch channel 2. The particles in the first sorting module 4 will be focused on the centerline of the channel in the first straight channel section 41 due to the elastic force of the viscoelastic ferrofluid, and will flow into the second straight channel section 43 after passing through the first amplification section 42. The NdFeB permanent magnet 3 will form a non-uniform magnetic field in the second straight channel section 43, thereby generating a negative magnetophoretic force on the particles, driving the particles to move in the opposite direction. The negative magnetophoretic force is related to the volume of the particles, so the two particles of different sizes will form a lateral position difference in the second straight channel section 43, and will be further amplified in the second amplification section 44, so that the large-sized particles and the small-sized particles will flow out from the first outlet 45 and the second outlet 46 respectively, thereby realizing the sorting of the particles.

[0103] The present invention can realize continuous and sheath-free sorting of particles of different sizes, and has the advantages of high throughput, small structure size, no need for magnetic bead modification, and simple operation.

[0104] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0105] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A particle sorting microfluidic chip based on viscoelastic ferrofluid, characterized in that: include: A first inlet (1), a branch channel (2), a magnet (3), a first sorting module (4) and a second sorting module (5); The first inlet (1) is connected to one end of the branch channel (2), and the first sorting module (4) and the second sorting module (5) are connected to the other end of the branch channel (2); The magnet (3) is located between the first sorting module (4) and the second sorting module (5); A mixed solution of viscoelastic ferrofluid and two types of particles is injected from the first inlet (1) and flows into the first sorting module (4) and the second sorting module (5) in equal amounts through the branch channel (3).

2. The particle sorting microfluidic chip based on viscoelastic ferrofluid according to claim 1, characterized in that: The first sorting module (4) and the second sorting module (5) have the same structure, and the first sorting module (4) and the second sorting module (5) are symmetrically arranged in parallel.

3. The particle sorting microfluidic chip based on viscoelastic ferrofluid according to claim 2, characterized in that: The first sorting module (4) comprises a first straight channel section (41), a first enlarged section (42), a second straight channel section (43), a second enlarged section (44), a first outlet (45) and a second outlet (46); One end of the first straight channel section (41) is connected to the other end of the branch channel (2), and the other end of the first straight channel section (41) is connected to one end of the first enlarged section (42); One end of the second straight channel section (43) is connected to the other end of the first enlarged section (42), and the other end of the second straight channel section (43) is connected to one end of the second enlarged section (44); The first outlet (45) and the second outlet (46) are connected to the other end of the second enlarged section (44); and the magnet (3) is located on one side of the second straight channel section (43).

4. The particle sorting microfluidic chip based on viscoelastic ferrofluid according to claim 1, characterized in that: The viscoelastic ferrofluid is prepared by adding a water-based ferrofluid into a polyethylene oxide solution.

5. A method for preparing a particle sorting microfluidic chip based on viscoelastic ferrofluid, characterized in that: The method for preparing the particle sorting microfluidic chip based on viscoelastic ferrofluid according to claim 3 comprises the following steps: Step 1: Mix polydimethylsiloxane and polydimethylsiloxane curing agent according to a preset mass ratio, stir with a glass rod for a preset time, mix thoroughly and place in a vacuum drying dish, and remove bubbles in the polydimethylsiloxane mixture by vacuuming; Step 2: placing the silicon wafer with the channel pattern of the microfluidic chip in a cell culture dish, and slowly introducing the polydimethylsiloxane mixture after the bubbles are removed in step 1, and after the polydimethylsiloxane mixture completely and evenly covers the surface of the silicon wafer, placing it in a vacuum drying dish again to evacuate and remove bubbles between the silicon wafer and the bottom of the cell culture dish; Step 3: placing the cell culture dish in step 2 in an oven for curing, separating the cured polydimethylsiloxane from the silicon wafer, cutting it into a preset shape, cutting a through hole for placing the magnet (3), and punching it with a puncher to form a first inlet (1), a first outlet (45) and a second outlet (46); Step 4: Use transparent tape to remove the pattern surface of the polydimethylsiloxane and the surface of the glass slide in step 3, and put the polydimethylsiloxane and the glass slide into a plasma cleaning machine; Step 5: Turn on the vacuum pump connected to the plasma cleaning machine in step 4. When the pressure in the chamber of the plasma cleaning machine drops to a preset pressure, stop evacuating and turn on the glow. When the preset glow appears in the vacuum chamber, start timing. After the preset time, stop the glow and take out the two. Step 6: The patterned surface of the polydimethylsiloxane in step 5 is tightly attached to the glass slide, and after lightly pressing to remove bubbles between the surfaces, the surface is placed on a heating table to further strengthen the bonding effect; Step 7: Insert the polytetrafluoroethylene capillary into the hole of the microfluidic chip, pour the polydimethylsiloxane mixture at the position, and place it in an oven to enhance the sealing performance of the entrance and exit positions; Step 8: Place the magnet (3) in the through hole of the microfluidic chip.

6. The method for preparing a particle sorting microfluidic chip based on viscoelastic ferrofluid according to claim 5, characterized in that: In the step 1, the amounts of polydimethylsiloxane and polydimethylsiloxane curing agent used are 30 g and 3 g respectively, and the vacuuming time is 50 minutes to 80 minutes.

7. The method for preparing a particle sorting microfluidic chip based on viscoelastic ferrofluid according to claim 5, characterized in that: In step 2, the vacuuming time is 20 minutes to 35 minutes.

8. The method for preparing a particle sorting microfluidic chip based on viscoelastic ferrofluid according to claim 5, characterized in that: In step 3, the oven temperature is set to 80° C. and the time is 50 minutes to 70 minutes.

9. The method for preparing a particle sorting microfluidic chip based on viscoelastic ferrofluid according to claim 5, characterized in that: In step 6, the temperature of the heating stage is set to 85° C., and the time is 40 minutes to 50 minutes.

10. The method for preparing a particle sorting microfluidic chip based on viscoelastic ferrofluid according to claim 5, characterized in that: In step 7, the oven temperature is set to 80° C. and the time is 50 minutes to 70 minutes.

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