Microfluidic chip for particle sorting based on viscoelastic ferrofluid and preparation method thereof

Abstract

The application provides a kind of particle sorting microfluidic chip based on viscoelastic ferrofluid and its preparation method, comprising: first inlet, branch channel, magnet, first sorting module and second sorting module;The first inlet is connected with one end of the branch channel, the first sorting module and the second sorting module are connected with the other end of the branch channel;The magnet is located between the first sorting module and the second sorting module;Viscoelastic ferrofluid and the mixed solution of two kinds of particles are injected from the first inlet, and flow into the first sorting module and the second sorting module equally via the branch channel.The application can realize continuous, 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.

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 leading cause of cancer-related deaths. If patients with early-stage metastatic cancer could receive timely treatment, the number of cancer deaths could be reduced by approximately 30%. Therefore, developing early cancer diagnosis and treatment technologies and studying the mechanisms of cancer metastasis are crucial for humanity's future fight against cancer. However, patients with early-stage metastatic cancer often have an extremely low tumor burden, making it difficult to locate metastatic lesions using traditional imaging methods and extract tumor cells for analysis through puncture biopsies. This significantly limits the molecular diagnosis of early-stage metastatic tumors, precision treatment, and research into the mechanisms of cancer occurrence, development, and metastasis.

[0003] Circulating tumor cells (CTCs) are seed cells that shed from primary or metastatic tumor lesions, undergo epithelial-mesenchymal transition, and enter the peripheral blood circulation. Numerous studies have demonstrated that CTCs are already present in patients' peripheral blood during the early stages of cancer metastasis. Therefore, CTC liquid biopsy technology can overcome the limitations of traditional tissue biopsies, which are limited to imaging-detectable solid tumor tissue. Furthermore, with its advantages of convenient sampling, dynamic observation, and non-invasiveness, it can comprehensively, accurately, and in real time present tumor biological information, demonstrating unique advantages in the precise diagnosis and treatment of early-stage cancers and prognostic assessment.

[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 technologies 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-scale 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] A patent document with the public number CN109550531A discloses a magnetic size-dependent microfluidic chip, which comprises a cover sheet and a substrate. The cover sheet is located directly above the substrate, and the cover sheet and the substrate are sealingly connected. The lower surface of the cover sheet is provided with a magnetophoretic separation structure and a size sorting channel for capturing different size magnetic microspheres. The magnetophoretic separation structure comprises a buffer moving channel, a sample moving channel, a merging 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 merging channel. The waste liquid discharge channel and the capture channel merge at the other end of the merging channel. The other end of the capture channel is in communication with the inlet of the size sorting channel. A magnet is arranged on the cover sheet, which is located above the merging channel and on one side of the projection of the merging channel on the upper surface of the cover sheet. The capture channel extends towards the direction close to the magnet, and the waste liquid discharge channel extends away from the magnet. The cover sheet is provided with a buffer inlet, a sample inlet, a first outlet and a second outlet. The buffer inlet is in communication with the buffer moving channel. The sample inlet is in communication with the sample moving channel. The first outlet is in communication with the waste liquid discharge channel. The second outlet is in communication with the outlet of the size sorting channel. However, the patent document still has problems such as low sorting purity, high shear stress and serious blockage.

[0006] A patent document with the publication number US20220379312A1 discloses a magnetic separation microfluidic chip, and specifically discloses a magnetic separation microfluidic chip, which comprises 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 comprises a sorting channel and a magnetic pole channel. The sorting channel has a plurality of sorting channel inlets and a plurality of sorting channel outlets. The magnetic separation unit comprises a permanent magnet, a high magnetic permeability alloy and a magnetic pole array arranged in the magnetic pole channel. 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 magnetic fields with opposite polarities at the left and right positions of the sorting channel. However, the patent document still has problems such as low sorting purity, high shear stress and serious blockage. SUMMARY

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

[0008] According to the particle sorting microfluidic chip based on viscoelastic ferrofluid provided by the present application, 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.

[0009] 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.

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

[0011] A mixed solution of viscoelastic iron fluid and two types 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 includes a first straight channel section, a first amplifying section, a second straight channel section, a second amplifying 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 amplifying section, and the other end of the second straight channel section is connected to one end of the second amplifying 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 viscoelastic ferrofluid-based particle sorting microfluidic chip, which is used to prepare the above-mentioned viscoelastic ferrofluid-based particle sorting microfluidic chip, 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 to remove bubbles in the polydimethylsiloxane mixture by vacuuming;

[0020] Step 2: Place the silicon wafer with the microfluidic chip channel pattern 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 and evacuate to 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 predetermined shape, cutting a through hole for placing the magnet, and punching it with a punch 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 plasma cleaning chamber drops to a preset pressure, stop pumping and turn on the glow. Start timing when the preset glow appears in the vacuum chamber. 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 and pour the polydimethylsiloxane mixture at the location. 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 heating 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 particle pre-focusing without the need to introduce sheath fluid, thereby increasing the particle concentration in the collected 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 ferrohydrodynamics to sort microspheres, eliminating the need for magnetic bead labeling, thereby reducing labeling-related time and costs. In addition, the module is simple to operate and low-cost, requiring only a permanent magnet 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 simultaneously, 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, effectively reducing 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 their integrity. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0043] Figure 6 Schematic diagram of the partial structure of the second amplification section in an embodiment of the present invention.

[0044] The figure shows:

[0045] DETAILED DESCRIPTION

[0046] The present invention will be described in detail below with reference to specific embodiments. The following examples 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 skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0047] Example 1:

[0048] As Figure 1-6 shown, the embodiment provides a kind of particle sorting microfluidic chip based on viscoelastic ferrofluid, comprising: first inlet 1, branch channel 2, magnet 3, first sorting module 4 and second sorting module 5;First inlet 1 is connected with one end of branch channel 2, first sorting module 4 and second sorting module 5 are connected with the other end of branch channel 2;Magnet 3 is located between first sorting module 4 and second sorting module 5;Viscoelastic ferrofluid and the mixed solution of two kinds of particles are injected from first inlet 1, and flow into first sorting module 4 and second sorting module 5 by branch channel 2 in equal amounts. First sorting module 4 and second sorting module 5 are the same structure, first sorting module 4 and second sorting module 5 are symmetrically arranged in parallel. Viscoelastic ferrofluid is prepared by adding water-based ferrofluid into polyethylene oxide solution.

[0049] First sorting module 4 includes first straight channel section 41, first amplification section 42, second straight channel section 43, second amplification section 44, first outlet 45 and second outlet 46;One end of first straight channel section 41 is connected with the other end of branch channel 2, and the other end of first straight channel section 41 is connected with one end of first amplification section 42;One end of second straight channel section 43 is connected with the other end of first amplification section 42, and the other end of second straight channel section 43 is connected with one end of second amplification section 44;First outlet 45 and second outlet 46 are connected with the other end of second amplification section 44;Magnet 3 is located on one side of second straight channel section 43.

[0050] The flow cross section of first amplification section 42 gradually increases along the fluid direction, and gradually increases along the direction perpendicular to the fluid direction. First amplification section 42 is used to connect the first straight channel section 41 with smaller width and the second straight channel section 43 with larger width, and the purpose is to widen the width of second straight channel section 43 to provide enough space for the transverse migration of particles.

[0051] The flow cross section of second amplification section 44 gradually increases along the fluid direction, and gradually increases along the direction perpendicular to the fluid direction. The current second amplification section 44 is used to further expand the transverse position difference of particles, because small and large size particles have already generated a certain transverse position difference when passing through second straight channel section 43, in order to further improve the sorting effect, second amplification section 44 is arranged to increase the transverse distance between large and small particles.

[0052] The embodiment also provides a preparation method of particle sorting microfluidic chip based on viscoelastic ferrofluid, which is used for preparing the above-mentioned particle sorting microfluidic chip based on viscoelastic ferrofluid, comprising the following steps:

[0053] 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, place in a vacuum drying dish, and remove bubbles in the polydimethylsiloxane mixture by vacuuming; 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;

[0054] Step 2: Place the silicon wafer with the microfluidic chip channel pattern in a cell culture dish and slowly introduce the polydimethylsiloxane mixture after removing bubbles 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 and vacuum it to remove bubbles between the silicon wafer and the bottom of the cell culture dish. The vacuuming time is 20-35 minutes.

[0055] Step 3: Place the cell culture dish prepared in step 2 in an oven for curing, separate the cured polydimethylsiloxane from the silicon wafer, cut it into a predetermined shape, cut a through hole for placing the magnet 3, and use a punch to punch holes to form a first inlet 1, a first outlet 45, and a second outlet 46; set the oven temperature to 80°C for 50-70 minutes;

[0056] Step 4: Use transparent tape to remove the patterned surface of the polydimethylsiloxane and the surface of the glass slide in step 3, and place the polydimethylsiloxane and the glass slide together in a plasma cleaning machine;

[0057] Step 5: Turn on the vacuum pump connected to the plasma cleaning machine in step 4. When the pressure in the plasma cleaning chamber drops to the preset pressure, stop pumping and turn on the glow. Start timing when the preset glow appears in the vacuum chamber. After the preset time, stop the glow and take out the two.

[0058] Step 6: Place the polydimethylsiloxane pattern surface in step 5 tightly against the glass slide, gently press to remove air bubbles between the surfaces, and then place on a heating table to further strengthen the bonding effect; the temperature of the heating table is set to 85°C for 40-50 minutes;

[0059] Step 7: Insert the polytetrafluoroethylene capillary into the hole of the microfluidic chip and pour the polydimethylsiloxane mixture into the hole. Place the capillary in an oven to enhance the sealing performance of the entrance and exit. The oven temperature is set to 80°C for 50-70 minutes.

[0060] Step 8: Place the magnet 3 in the through-hole of the microfluidic chip.

[0061] Silicon wafers with microfluidic channel patterns are prepared using the following process:

[0062] The microfluidic chip is fabricated using soft lithography, where the channel shape is transferred onto a photoresist layer on a silicon wafer via photolithography. PDMS is then poured onto the silicon wafer and cured. All channels in the microfluidic chip are fabricated simultaneously. The channel pattern includes: branch channel 2, first straight channel segment 41, first amplification segment 42, second straight channel segment 43, second amplification segment 44, and the channels within the second sorting module 5.

[0063] In this embodiment, the microfluidic chip uses viscoelastic ferrofluid as a particle transport medium and utilizes elastic force to achieve particle pre-focusing without the need to introduce sheath fluid, thereby increasing the particle concentration in the collected solution and avoiding the squeezing of particles against the channel wall.

[0064] In this embodiment, the magnetic field sorting module of the microfluidic chip uses ferrohydrodynamics to sort microspheres, eliminating the need for magnetic bead labeling, thereby reducing the time and cost associated with labeling. Furthermore, the module is simple to operate and low-cost, requiring only a permanent magnet to achieve sorting.

[0065] 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 simultaneously, thereby improving the sorting throughput.

[0066] In this embodiment, the microfluidic chip uses the force exerted by the fluid on the particles to achieve sorting, which effectively reduces the probability of direct collision between the particles and the microstructure. When this technology is applied to sorting biological particles, it can reduce damage to the biological particles and improve their integrity.

[0067] Example 2:

[0068] Those skilled in the art may understand this embodiment as a more specific description of Embodiment 1.

[0069] This embodiment provides a particle sorting microfluidic chip based on viscoelastic ferrofluid. The microfluidic chip includes a first inlet 1, a branch channel 2, a neodymium iron boron permanent magnet, a first sorting module 4, and a second sorting module 5. The first sorting module 4 and the second sorting module 5 have the same structure and are arranged symmetrically in parallel. The first sorting module 4 consists 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. 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. The width of the amplifying section is 1 mm.

[0070] The viscoelastic ferrofluid exerts an elastic force on the particles in the first straight channel section 41, driving the particles to gradually converge 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:

[0071]

[0072] in, 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 transverse coordinate of the particle in the channel (the origin of the coordinate is located at the center line of the channel), e j is the horizontal unit vector, w is the width of the first straight channel section 41, h is the channel height.

[0073] The NdFeB permanent magnets generate a nonuniform magnetic field in the second straight channel section 43, which in turn generates a negative magnetophoretic force on the particles, driving them in the opposite direction. This magnetophoretic force is related to the particle volume, causing two particles of different sizes to form a lateral position difference in the second straight channel section 43. This lateral position difference is further amplified as the particles pass through the second amplification section 44, enabling separation of the two sized particles. The negative magnetophoretic force on the particles can be expressed by the following formula:

[0074]

[0075] in, V p is the particle volume, μ 0 is the vacuum permeability, M is the effective magnetization of the ferrofluid, and H is the magnetic field strength.

[0076] The viscoelastic ferrofluid injected from the first inlet 1 is prepared by adding a water-based ferrofluid to a polyethylene oxide (PEO) solution, wherein the diameter of the nanomagnetic beads is 8 nm–12 nm and the concentration of the magnetic beads is 0.11% v / v. The PEO solution is prepared by dissolving 2000 kDa PEO powder in deionized water with a solubility of 0.1% w / w–0.2% w / w.

[0077] 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.

[0078] This embodiment provides a method for preparing the above-mentioned microfluidic chip, comprising the following steps:

[0079] Step 1. Mix polydimethylsiloxane and polydimethylsiloxane curing agent in a mass ratio of 10:1, stir with a glass rod for 7 to 10 minutes, mix thoroughly, and place in a vacuum drying dish to remove bubbles in the polydimethylsiloxane mixture by vacuuming;

[0080] Step 2: placing the silicon wafer with the microfluidic chip channel pattern in a cell culture dish and slowly introducing 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, the silicon wafer is again placed in a vacuum drying dish and vacuumed to remove bubbles between the silicon wafer and the bottom of the cell culture dish.

[0081] Step 3: Place the cell culture dish prepared in step 2 in an oven for curing, separate the cured polydimethylsiloxane from the silicon wafer, cut it into a regular rectangular parallelepiped shape, cut out a rectangular through hole for placing the magnet 3, and use a punch to punch holes at the positions of the first inlet 1, the first outlet 45, and the second outlet 46;

[0082] 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;

[0083] Step 5: Turn on the vacuum pump connected to the plasma cleaner in Step 4. When the pressure in the plasma cleaner chamber drops to 200 Pa, stop pumping and turn on the glow light. Start timing when a purple-red glow appears in the vacuum chamber. After 45 seconds, stop the glow light and remove the two devices.

[0084] 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;

[0085] Step 7: insert a polytetrafluoroethylene capillary into the punched hole of the microfluidic chip, pour a small amount of polydimethylsiloxane mixture at the location, and place it in an oven to enhance the sealing performance of the inlet and outlet positions;

[0086] Step 8: Place the NdFeB permanent magnet in the rectangular through-hole of the microfluidic chip.

[0087] In step 1, the amount of polydimethylsiloxane and polydimethylsiloxane curing agent used is 30 g and 3 g, respectively, and the vacuuming time is 50 to 80 minutes. The vacuuming time in step 2 is 20 to 35 minutes. In step 3, the oven temperature is set to 80°C for 50 to 70 minutes. In step 6, the temperature of the heating plate is set to 85°C for 40 to 50 minutes. In step 7, the oven temperature is set to 80°C for 50 to 70 minutes.

[0088] The embodiment discloses a particle sorting microfluidic chip based on a viscoelastic ferrofluid, which comprises a first inlet 1, a branch channel 2, a neodymium-iron-boron permanent magnet, a first sorting module 4 and a second sorting module 5, wherein the first sorting module 4 and the second sorting module 5 are symmetrical and arranged in parallel, and the first sorting module 4 is composed of a first straight channel segment 41, a first amplification segment 42, a second straight channel segment 43, a second amplification segment 44, a first outlet 45 and a second outlet 46. The viscoelastic ferrofluid and a mixed solution of two kinds of particles are injected from the first inlet 1 and flow into the first sorting module 4 and the second sorting module 5 through the branch channel 2. The particles in the first sorting module 4 are focused on the center line of the channel due to the elastic force of the viscoelastic ferrofluid in the first straight channel segment 41, and flow into the second straight channel segment 43 after passing through the first amplification segment 42. The neodymium-iron-boron permanent magnet forms a non-uniform magnetic field in the second straight channel segment 43, thereby generating a negative magnetophoretic force on the particles and driving the particles to move in the opposite direction. The negative magnetophoretic force is related to the volume of the particles, so that the two kinds of particles with different sizes form a transverse position difference in the second straight channel segment 43, and are further amplified in the second amplification segment 44, so that the large-size particles and the small-size particles flow out from the first outlet 45 and the second outlet 46 respectively, thereby realizing the sorting of the particles. The present application can continuously and sheathlessly sort particles of different sizes, and has the advantages of high throughput, small structure size, no need for magnetic bead modification and simple operation.

[0089] In order to overcome the technical bottleneck of the existing sorting method, the embodiment provides a microfluidic chip capable of sheathlessly and conveniently sorting micron-level particles, which provides technical support for the separation of biological particles such as CTC and promotes the further research and clinical application of CTC liquid biopsy technology.

[0090] Example 3:

[0091] Those skilled in the art can understand the embodiment as a more specific description of embodiment 1.

[0092] As Figure 1 shown, the embodiment provides a particle sorting microfluidic chip based on a viscoelastic ferrofluid, which mainly comprises a first inlet 1, a branch channel 2, a neodymium-iron-boron permanent magnet, a first sorting module 4 and a second sorting module 5, wherein the first sorting module 4 and the second sorting module 5 are symmetrical and arranged in parallel, and the first sorting module 4 is composed of a first straight channel segment 41, a first amplification segment 42, a second straight channel segment 43, a second amplification segment 44, a first outlet 45 and a second outlet 46. A mixture sample of two kinds of particles with different sizes and a viscoelastic ferrofluid is injected into the microfluidic chip from the first inlet 1 by using a syringe pump.

[0093] As Figure 2As 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 gradually focus 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.

[0094] like Figure 3 As shown, after exiting the first straight channel section 41, the particles pass through the first amplifying section 42 and enter the second straight channel section 43. The NdFeB permanent magnets generate a non-uniform magnetic field in the second straight channel section 43, attracting the viscoelastic ferrofluid toward the NdFeB permanent magnets. This in turn generates a negative magnetophoretic force on the particles, driving them in the opposite direction. Because the negative magnetophoretic force is related to particle volume, larger particles experience greater lateral displacement, ultimately exiting through the first outlet 45, while smaller particles exit through the second outlet 46, achieving separation of particles of different sizes.

[0095] 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.

[0096] Working principle of the present invention:

[0097] 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 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 amplification section 42. The neodymium iron boron permanent magnet 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 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 achieving particle sorting.

[0098] The present invention can realize continuous and 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.

[0099] In the description of this application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0100] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

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 iron fluid 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 (2); The first sorting module (4) comprises 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); 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 amplifying section (42); One end of the second straight channel section (43) is connected to the other end of the first amplifying section (42), and the other end of the second straight channel section (43) is connected to one end of the second amplifying section (44); The first outlet (45) and the second outlet (46) are connected to the other end of the second amplifying section (44); the magnet (3) is located on one side of the second straight channel section (43).

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 1, characterized in that: The viscoelastic ferrofluid is prepared by adding a water-based ferrofluid into a polyethylene oxide solution.

4. 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 1 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 to remove bubbles in the polydimethylsiloxane mixture by vacuuming; Step 2: Place the silicon wafer with the microfluidic chip channel pattern 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 and evacuate to 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 predetermined shape, cutting a through hole for placing the magnet (3), and punching it with a punch 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 plasma cleaning chamber drops to a preset pressure, stop pumping and turn on the glow. Start timing when the preset glow appears in the vacuum chamber. 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, and pour the polydimethylsiloxane mixture into the hole. Place it in an oven to enhance the sealing performance of the entrance and exit positions; Step 8: Place the magnet (3) into the through-hole of the microfluidic chip.

5. The method for preparing a particle sorting microfluidic chip based on viscoelastic ferrofluid according to claim 4, 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.

6. The method for preparing a particle sorting microfluidic chip based on viscoelastic ferrofluid according to claim 4, characterized in that: In step 2, the vacuuming time is 20 minutes to 35 minutes.

7. The method for preparing a particle sorting microfluidic chip based on viscoelastic ferrofluid according to claim 4, characterized in that: In step 3, the oven temperature is set to 80° C. and the drying time is 50 minutes to 70 minutes.

8. The method for preparing a particle sorting microfluidic chip based on viscoelastic ferrofluid according to claim 4, characterized in that: In step 6, the temperature of the heating stage is set to 85° C., and the heating time is 40 minutes to 50 minutes.

9. The method for preparing a particle sorting microfluidic chip based on viscoelastic ferrofluid according to claim 4, characterized in that: In step 7, the oven temperature is set to 80° C. and the drying time is 50 minutes to 70 minutes.

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