A microfluidic chip structure and particle manipulation method based on swirl double stagnation point

Abstract

The present invention discloses a microfluidic chip structure and particle manipulation method based on swirl double stagnation point, which relates to the fields of microfluidics, particle manipulation methods, etc., and mainly includes a microfluidic chip. The microfluidic chip includes a substrate, and the upper surface of the substrate is provided with three flow channels and a guide wall. The outlets of the second flow channel and the third flow channel are parallel to each other and are located below the outlet of the first flow channel. The guide wall is located at the center where the central axes of the second flow channel and the third flow channel are connected, and is on the same horizontal plane as the outlet end face. The structure consists of three flow channels and a circular guide wall located in the middle area. The particle manipulation method is to uniformly spray fluid from the three flow channels so that the microfluid forms a swirl low-pressure zone on the left and right sides of the circular guide wall, thereby entraining, capturing, and stably rotating the particles. The present structure and method can perform non-destructive manipulation of particles.

Description

Technical Field

[0001] The present invention belongs to the field of microfluidics and relates to a particle manipulation technology, in particular to a microfluidic chip structure based on swirl double stagnation points and a particle manipulation method. Background Art

[0002] Particle manipulation is a key technology in micromanipulation and the core technology of microfluidic chips. It is now widely used in biomedicine, materials science and other fields (Wu Chunhui, Jiang Youwei, Cheng Xin. Application of microfluidic chips in single cell capture [J]. Science and Technology Herald, 2018, 36(16):7.). Yang Chaoyong et al. from Xiamen University proposed a microfluidic chip for precise manipulation and pairing of single particles. The chip includes a channel layer and a control layer. The channel layer includes multiple units for capturing and transferring single particles. Each unit consists of a capture channel, a capture chamber, a capture gap, a transfer channel, a pairing chamber, and a pairing gap. The control layer is located below the capture channel and the pairing channel, perpendicular to the capture channel and the pairing channel and separated by a diaphragm. The microfluidic chip can efficiently and precisely control the capture and transfer of single particles, and after different rounds of single particle capture and transfer, high-throughput and high-efficiency single particle pairing can be achieved, and the number and type of paired particles can be controlled. (Yang Chaoyong, Liu Weizhi, Li Xingrui, et al. A microfluidic chip for precise manipulation and pairing of single microparticles and its application, CN109722385A[P]. 2019.) However, this method can only capture and transfer single particles and cannot conduct multi-particle interaction research. Xing Xiaoxing et al. disclosed a microfluidic chip for cell-microbead capture and pairing, comprising a dielectrophoresis capture section and a microwell collection section with a lysis buried electrode section. Microbeads and cells are captured using the dielectrophoretic force generated by the double-layer structure electrodes of the dielectrophoretic capture section and the periodic capture grooves of the electrodes, achieving dual, efficient capture and pairing of cells and microbeads. After capture, the dielectrophoretic excitation is stopped, and gravity causes the microbeads and cells to settle into the microwells of the microwell collection section, forming a one-to-one pairing collection of the microbeads and cells in the microwells of the microwell collection section. After pairing is complete, the lysis electrode, consisting of the double-layer structure electrodes of the dielectrophoretic capture section and the liquid electrode of the lysis buried electrode section, is energized to lyse the cells. This invention uses an active control mechanism of dielectrophoresis to control the trajectory and ultimately capture cells and microbeads, enabling the processing of high-throughput samples and shortening capture time, thereby reducing R&D and manufacturing time and costs (Xing Xiaoxing, Liu Zhuzhu, Cai Yao, et al. A microfluidic chip for cell-microbead capture pairing, CN115007231A[P].2022.). Cheng Xin et al. provide a cell array capture and pairing microfluidic chip, comprising arrayed cell pair units, each of which is provided with a large microwell, three small microwells within the large microwell and spaced apart at a depth, three sets of electrode pairs, and a shielding electrode between adjacent small microwells, wherein the small microwells are located between corresponding electrode pairs.The cell capture and pairing microfluidic chip of this invention can capture three types of cells on the chip in succession to realize a large-scale triple cell array; in the array, one of the three cells is taken from each other and arranged in pairs in a group of three, which can provide great convenience and possibility for studying cell-to-cell interactions such as three-cell paracrine or cell fusion (Cheng Xin, Tao Chaoran, Wu Chunhui, et al. A cell capture and pairing microfluidic chip, CN114891628A[P].2022.). The above method can realize the capture and control of two microparticles, but it involves the use of electric fields, the device is relatively complex, and the effect of electric fields on active biological cells is unclear. This method adopts a swirl control stationary point method without an external force field, and realizes the capture and control of double microparticles based on fluid dynamics and structural design, which is low in cost and higher in safety.

[0003] Particle manipulation methods based on stagnation points in swirling flow do not cause mechanical damage to the particles and have advantages such as a simple control system and high sample processing throughput. However, current research on using stagnation points in swirling flow regions for micromanipulation is not mature, which limits its further application. In the field of micromanipulation using stagnation points in fluids, Safavieh et al. at McGill University designed a multi-microtubule, mobile, channel-free microfluidic device that achieves mobile manipulation of stagnation points by changing the position and flow rate of the microtubules (Safavieh, M., et al., Two-Aperture Microfluidic Probes as Flow Dipoles: Theory and Applications (vol 5, 11943, 2015). Scientific Reports, 2015.5.). Yaxiaer Yalikun et al. from Osaka University in Japan formed a reflux on a vertical plane by spraying fluid onto the top of a microfluidic chip, and used the reflux to realize the rotation of particles of different sizes on the vertical plane (Yalikun, Y., Y. Kanda, and K. Morishima, Hydrodynamic vertical rotation method for a single cell in an open space. Microfluidics and Nanofluidics, 2016. 20 (5).). The swirl drive structure was proposed by Professor Zhang Qin of South China University of Technology (Zhang Q, Fan J, Aoyama H. ​​Manipulation of particles based on swirl [J]. Japanese Journal of Applied Physics, 2018, 57 (1): 017202.). Two microtubes placed opposite each other will generate a swirl in the plane where the two microtubes are located. The area near the center of the swirl has the characteristics of low pressure, low flow rate, and a large pressure difference with the periphery of the swirl field. The vortex center region entrains particles within the vortex, trapping them and forcing them into the center. If the parameters of the vortex field match those of the particles, the particles, driven by viscous forces, will rotate along their own axes and remain within the vortex center. By controlling the speed difference between three microtubes within the flow field, particles can simultaneously rotate and follow the vortex center in any direction within the flow field. By controlling the stationary point at the vortex center, particle capture, movement, and rotation can be achieved.

[0004] The existing methods for controlling microparticles are difficult to achieve a series of operations such as capturing, moving and rotating microparticles at the same time, and the microfluidic chips based on the principle of swirl stagnation can only control single particles. Compared with existing technologies, the proposed solution has the characteristics of simple control, strong anti-interference ability, and easy integration. The research results solve the problem of microparticle posture adjustment, and achieve a series of actions such as capturing, moving and adjusting the posture of microparticles at the same time. On this basis, the present invention proposes a microfluidic chip structure and a microparticle manipulation method based on swirl double stagnation points, which uses two swirl low-pressure areas formed in the flow domain to capture and control two microparticles at the same time, thereby expanding its applicability. Summary of the Invention

[0005] Given the limited availability of non-destructive techniques for particle manipulation and the lack of systematic and mature research on stagnation-point microparticle manipulation using swirl flow, this paper proposes a microfluidic chip structure and particle manipulation method based on swirl flow dual-stagnation points. This design employs a microfluidic chip structure that forms two stagnation points in a swirl flow low-pressure zone, enabling the simultaneous capture and control of two particles. This dual-stagnation-point model can be used for fluid-directed assembly of multiple particles in solution, providing a particle manipulation method for fundamental research on multi-particle manipulation and assembly, as well as particle-particle interactions.

[0006] The present invention is achieved through at least one of the following technical solutions.

[0007] A microfluidic chip structure based on swirl double stagnation points includes a microfluidic chip, which includes a substrate. The upper surface of the substrate is provided with three flow channels and a guide wall. The outlets of the second flow channel and the third flow channel are parallel to each other and are located below the outlet of the first flow channel. The guide wall is located at the center where the central axes of the second flow channel and the third flow channel are connected, and is on the same horizontal plane as the outlet end surface.

[0008] Furthermore, the three flow channels are in the same plane, and the outlet end surface of the first flow channel and the central axes of the second flow channel and the third flow channel form a closed rectangle.

[0009] Furthermore, the cross-sectional shapes of the outlet ends of the three flow channels are all rectangular, and the interior transitions from a rectangle to a circular hole, ensuring that the flow rate of the fluid is equal during the flow channel structure transition.

[0010] Furthermore, the three flow channels are independently controlled by three syringe pumps to provide microfluidics as fluid inlets.

[0011] Furthermore, the guide wall is located between the second flow channel and the third flow channel, and the lower end of the guide wall is tangent to the line connecting the outlet end faces of the second flow channel and the third flow channel.

[0012] Furthermore, the guide wall is a circular guide wall.

[0013] Furthermore, the inlets of the three flow channels are connected to a syringe.

[0014] Furthermore, positioning grooves are provided on both sides of the base plate, and the base plate is installed in the clamping platform through the positioning grooves.

[0015] Furthermore, the microfluidic chip is installed in the container through a leaf spring press.

[0016] The method for controlling particles based on a swirl double-stationary point microfluidic chip structure is characterized by comprising the following steps:

[0017] 1) Use the positioning groove to fix the microfluidic chip on the clamping platform. Connect the flow input ports of the three flow channels (1, 3, 4) to the syringe (12). The syringe (6) is connected to the hose and fixed to the clamping platform. Adjust the microfluidic chip to ensure that the top surface of the chip is in a horizontal state.

[0018] 2) Before the formal experiment, the air in the pipeline should be purged with fluid to prevent bubbles from affecting the continuous input and output of the fluid in the microtube;

[0019] 3) Using a syringe pump, inject microfluids into the three flow channels through a syringe and a hose, forming two vortex flow areas within the flow domain surrounded by the three flow channels; at the same time, a liquid aspiration syringe extracts liquid from the clamping platform;

[0020] 4) Release micron particles into the swirling low-pressure area;

[0021] 5) The particles are observed to be captured and stably maintained in the low-pressure region of the vortex, and then observed with the aid of a microscope;

[0022] 6) By changing the injection speed of the fluid in the second flow channel and the third flow channel, the rotation speed of the captured particles in the two flow domains is controlled respectively.

[0023] Furthermore, the three flow channels are connected to the hoses through adapters, and the hoses are clamped in the grooves of the clamping platform. It should be ensured that the three hoses are on the same horizontal line as much as possible and are not entangled with each other.

[0024] Furthermore, by adjusting the flow rate of the two lower flow channels, the swirl intensity at the stagnation point is controlled, thereby achieving the capture of particles of different sizes.

[0025] Furthermore, by changing the cross-sectional area of ​​the flow channel, the structure can be adapted to capture and manipulate particles of different sizes, thereby expanding the applicable objects of the structure.

[0026] Compared with the existing technology, the beneficial effects of the present invention are:

[0027] 1. Taking into account the natural unloading of the fluid, the interference of the velocity outlet on the flow field is minimized as much as possible;

[0028] 2. The cyclonic double-stationary point structure can capture and control two particles at the same time, improving the sample processing throughput. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the microfluidic chip structure of the present invention;

[0030] Figure 2 is a cross-sectional view of the microfluidic chip structure of the present invention;

[0031] Figure 3 This is a schematic diagram of the microfluidic chip experimental device based on swirl double stationary points;

[0032] Figure 4 This is a microscope image of the experiment of swirl double-stationary point particle manipulation;

[0033] Among them, 1-first flow channel, 3-second flow channel, 4-third flow channel, 2-guide wall, 5-substrate; 6-aspiration syringe, 7-control panel, 8-computer, 9-clamping platform, 10-microfluidic chip, 11-microscope, 12-liquid inlet syringe, 13-injection pump. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. The present invention will be further described in detail below in conjunction with the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0035] As attached Figure 1 As shown, this embodiment provides a microfluidic chip structure based on a swirl double stagnation point, including a microfluidic chip 10, the microfluidic chip 10 includes a substrate 5, and three flow channels (1, 3, 4) and a guide wall 2 are provided on the upper surface of the substrate 5. The substrate 5, the three flow channels (1, 3, 4) and the guide wall 2 are an integrated structure.

[0036] The outlets of the second and third flow channels 3 and 4 are parallel to each other and located below the outlet of the first flow channel 1. The outlet end face of the first flow channel 1 forms a closed rectangle with the central axes of the second and third flow channels 3 and 4. The guide wall 2 is located at the center of the connection between the central axes of the second and third flow channels 3 and 4 and is coplanar with the outlet end face. The inlets of the three flow channels (1, 3, 4) are connected to the inlet of the syringe 12 located on the side end face of the base plate 5.

[0037] The cross-sectional shapes of the outlet ends of the three flow channels (1, 3, 4) are all rectangular, and the interior transitions from a rectangle to a circular hole to facilitate adaptation to an external circular hose, ensuring equal flow rates of the fluids during the flow channel structure transition process.

[0038] As a preferred embodiment, the cross-sectional dimensions of the outlet ends of the three flow channels (1, 3, 4) are all 0.5*1.5mm. 2 The enclosed rectangle has dimensions of 3 x 6 mm. The three flow channels (1, 3, and 4) are independently controlled by three syringe pumps to provide microfluidics as fluid inlets. Different flow channel cross-sectional areas can be designed based on the size of the particles to be captured, expanding its applicability. The guide wall 2 is a circular guide wall 2 with a radius of 0.5 mm.

[0039] The microfluidic chip has an open structure, and the outlet adopts a natural unloading method. The microfluid flows from the upper surface of the substrate 5 into the clamping disc container. The upper surface of the substrate 5 is a horizontal surface. When the deionized water on the upper surface of the substrate reaches a certain liquid level, it overflows into the clamping platform container 9.

[0040] As a preferred embodiment, the substrate 5 is provided with positioning grooves on both sides, and is mounted in the clamping container through the positioning grooves. In addition to using the positioning grooves to clamp and fix the microfluidic chip, a leaf spring pressure piece is also required to further fix the microfluidic chip.

[0041] As attached Figure 3 As shown, the microfluidic chip 10 is fixed on the clamping platform 9 by using the positioning groove, and the three flow channels (1, 3, 4) inlet of the microfluidic chip 10 are connected to the syringe 12 through the external hose of the adapter. The injection speed of the fluid in the syringe 12 is preset by the control panel 7, and the syringe pump 13 is driven to feed at a certain speed to push the syringe 12 to move, so that the liquid in the syringe 12 enters the three flow channels at the set injection speed. At the same time, the liquid suction syringe 6 can extract the liquid in the clamping platform 9, thereby ensuring the stability of the fluid flow in the chip. The three syringe pumps provide liquid to the three flow channels respectively, and two vortex low-pressure areas will be formed on the left and right sides of the guide wall 2, thereby capturing particles. A microscope 11 is installed above the clamping platform 9 for real-time observation. The microscope and the syringe pump are both connected to the computer 8, and the vortex area on the microfluidic chip platform can be observed in real time.

[0042] Attachment Figure 2 The figure shows a cross-sectional view of a microfluidic chip structure based on a swirl double-stationary point. During processing, high requirements are placed on the flatness and smoothness of the middle rectangular area. Particle manipulation experiments must ensure the stability of the flow domain within the middle rectangular area. The size of the rectangle can be adjusted according to the size and range of movement of the particles.

[0043] The particle manipulation method based on the microfluidic chip structure with double stagnation points of swirl flow comprises the following steps:

[0044] 1) Use the positioning groove to fix the microfluidic chip (10) on the clamping platform (9). Connect the flow input ports of the three flow channels (1, 3, 4) to the syringe (12). The syringe (6) is connected and fixed to the clamping platform (9) through a hose. Adjust the microfluidic chip to ensure that the top surface of the chip is in a horizontal state;

[0045] 2) Before the formal experiment, the air in the pipeline should be purged with fluid to prevent bubbles from affecting the continuous input and output of the fluid in the microtube;

[0046] 3) Using a syringe pump (13), the microfluid is injected into the three flow channels (1, 3, 4) at a certain speed (25-60 mm / s) through a syringe (12) and a hose, forming two vortex flow areas in the flow domain surrounded by the three flow channels (1, 3, 4); at the same time, the liquid aspiration syringe (6) extracts the liquid in the clamping platform (9);

[0047] 4) Release micron particles into the swirling low-pressure area;

[0048] 5) The particles are observed to be captured and stably maintained in the low-pressure area of ​​the vortex, which can be observed with the help of a microscope;

[0049] 6) By varying the injection velocity of the fluid in the two lower flow channels (3, 4), the rotational speed of the captured particles in the two flow regions is controlled. By adjusting the flow velocity in the two lower flow channels (3, 4), the swirl intensity at the stagnation point is controlled, thereby enabling the capture of particles of different sizes or masses.

[0050] Attachment Figure 4 Shown is a microscope image of a particle manipulation experiment based on a swirl double-stationary point. Given the fluid velocities in the three flow channels, the particles are captured in the low-pressure region of the swirl, a process that can persist for hours without external interference. Note the liquid level during the experiment; the particles used in the experiment have a diameter of 100 μm.

[0051] In this method, by adjusting the flow rate in the two lower flow channels and controlling the swirl intensity at the stagnation point, particles of varying sizes and masses can be captured. Changing the syringe pump feed rate changes the fluid velocity within the flow channels, thereby shifting the particle capture location. The circular guide wall can be slightly moved up and down, left and right, adjusting the specific location where particles are captured.

[0052] The present invention can be used for the fluid-directed assembly of multiple particles in a solution. The swirling low-pressure areas on both sides can realize the simultaneous control of cells and drug particles. By changing the flow input of the three flow channels or the position of the guide wall, the distance between the two stationary points can be adjusted to realize the study of the interaction effect between particles, providing a new method for pharmaceutical chemical analysis.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention within the scope disclosed by the present invention, which fall within the scope of protection of the present invention.

Claims

1. A microfluidic chip structure based on swirl double stagnation point, characterized in that: The microfluidic chip (10) includes a substrate (5), and the upper surface of the substrate (5) is provided with three flow channels (1, 3, 4) and a guide wall (2). The outlets of the second flow channel (3) and the third flow channel (4) are parallel to each other and are located below the outlet of the first flow channel (1). The guide wall (2) is located at the center where the central axes of the second flow channel (3) and the third flow channel (4) are connected. The three flow channels (1, 3, 4) are in the same plane. Three injection pumps respectively supply liquid to the three flow channels, and two vortex low-pressure areas are formed on the left and right sides of the guide wall (2).

2. The microfluidic chip structure based on swirl double stagnation point according to claim 1, characterized in that: The outlet end surface of the first flow channel (1) and the central axes of the second flow channel (3) and the third flow channel (4) form a closed rectangle.

3. The microfluidic chip structure based on swirl double stagnation point according to claim 1, characterized in that: The cross-sectional shapes of the outlet ends of the three flow channels (1, 3, 4) are all rectangular, and the interior transitions from a rectangle to a circular hole, ensuring that the flow rate of the fluid is equal during the flow channel structure transition.

4. The microfluidic chip structure based on swirl double stagnation point according to claim 1, characterized in that: The three flow channels (1, 3, 4) are independently controlled by three syringe pumps to provide microfluidics as fluid inlets.

5. The microfluidic chip structure based on swirl double stagnation point according to claim 1, characterized in that: The guide wall (2) is located between the second flow channel (3) and the third flow channel (4), and the lower end of the guide wall (2) is tangent to the line connecting the outlet end faces of the second flow channel (3) and the third flow channel (4).

6. The microfluidic chip structure based on swirl double stagnation point according to claim 1, characterized in that: The guide wall (2) is a circular guide wall (2).

7. The microfluidic chip structure based on swirl double stagnation point according to claim 1, characterized in that: The flow input ports of the three flow channels (1, 3, 4) are connected to the liquid inlet syringe (12).

8. The microfluidic chip structure based on swirl double stagnation points according to any one of claims 1 to 7, characterized in that: Positioning grooves are provided on both sides of the base plate (5), and the base plate (5) is mounted in the clamping platform (9) through the positioning grooves.

9. The microfluidic chip structure based on swirl double stagnation points according to any one of claims 1 to 7, characterized in that: The microfluidic chip (10) is installed in the container via a leaf spring press.

10. Implementing the particle manipulation method based on a swirl double-stationary point microfluidic chip structure as claimed in claim 8, characterized in that: The following steps are involved: 1) Using the positioning groove, fix the microfluidic chip (10) on the clamping platform (9), connect the flow input ports of the three flow channels (1, 3, 4) to the liquid inlet syringe (12), and connect the liquid aspiration syringe (6) to the hose and fix it to the clamping platform; adjust the microfluidic chip to ensure that the top surface of the chip is in a horizontal state; 2) Before the formal experiment, use fluid to empty the air in the pipeline; 3) Using a syringe pump (13), the microfluid is injected into the three flow channels through the liquid inlet syringe (12) and the hose, forming two vortex areas in the flow domain surrounded by the three flow channels; at the same time, the liquid aspiration syringe (6) extracts the liquid in the clamping platform (9); 4) Release micron particles into the swirling low-pressure area; 5) The particles are observed to be captured and stably maintained in the vortex low-pressure area, and then observed with the help of a microscope; 6) By changing the injection speed of the fluid in the second flow channel (3) and the third flow channel (4), the rotation speed of the captured particles in the two flow domains is controlled respectively.

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