An experimental device and method for measuring the swimming characteristics of algae cells in shear flow

Abstract

The present invention discloses an experimental device and method for measuring the swimming characteristics of algae cells in shear flow. The experimental device includes an air pressure source, a pressure pump, a liquid storage bottle, a flow meter, a microchannel, and a waste liquid bottle connected in sequence. The method includes determining an average flow rate according to experimental working conditions to produce a stable shear flow, photographing an image sequence of the algae cell movement trajectory, obtaining the distribution of the algae cell migration velocity V through the observed algae cell movement trajectory, and calculating the algae cell flow velocity V using an analytical method. flow The distribution of the algae cells in the shear flow is then calculated to obtain the swimming characteristics, including their own swimming speed V s The present invention achieves high-precision measurement of algal cell motion in shear flow. By combining experimental and analytical methods, it addresses the inability of previous studies to obtain the algal cell's own swimming characteristics, such as swimming speed and angular velocity, and provides technical support for the development of microbial hydraulics at a more detailed microscopic scale.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental hydraulics, and in particular relates to an experimental device and method for measuring the swimming characteristics of algae cells in shear flow. Background Art

[0002] Currently, water pollution and ecological damage caused by algal blooms are becoming increasingly prominent. Therefore, clarifying the motility characteristics of algal cells is crucial for understanding their migration, aggregation, and distribution patterns, and, in turn, for predicting the occurrence and development of algal blooms. Dinoflagellate blooms occur extensively in riverine reservoirs and bays. These blooms are driven by their flagella, a process that is not only influenced by their own dynamic properties but also by external flow conditions.

[0003] Shear flows are widely present in natural and artificial environments, from ocean turbulence to river flow to liquid circulation in bioreactors, all of which contain significant shear effects. Therefore, precise observation of the movement of algal cells in shear flows is crucial to revealing the interaction between water flow and microalgae movement. The swimming characteristics of algal cells mainly include swimming speed, angular velocity, etc. However, at present, the use of microscale experiments to observe the swimming characteristics of algal cells in shear flow environments is still immature, and there are no corresponding research results in China. Therefore, how to measure the swimming characteristics of algal cells in shear flows is a technical problem that needs to be solved urgently. Summary of the Invention

[0004] The purpose of the present invention is to provide an experimental device and method for measuring the swimming characteristics of algae cells in shear flow, so as to solve the above technical problems.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention discloses an experimental device for measuring the swimming characteristics of algae cells in shear flow, the experimental device comprises an air pressure source, a pressure pump, a liquid storage bottle, a flow meter, a microchannel and a waste liquid bottle connected in sequence, the air pressure source and the pressure pump, the pressure pump and the liquid storage bottle are all connected through connecting pipes, the liquid storage bottle and the flow meter, the flow meter and the inlet of the microchannel, and the outlet of the microchannel and the waste liquid bottle are all connected through conduits, the device also comprises a connected fluorescence microscope and a high-speed camera, the high-speed camera is installed below the stage of the fluorescence microscope, and the microchannel is arranged on the stage of the fluorescence microscope; the air pressure source is used to provide basic pressure for the pressure pump; The pressure pump is used to output a set constant pressure to create an internal and external pressure difference in the liquid storage bottle; the liquid storage bottle is closed and contains an algae cell solution. Under the action of the internal and external pressure difference, the algae cell solution is transported to the microchannel through a catheter to form a shear flow; the flow meter is used to monitor the flow rate pumped by the pressure pump in real time; the microchannel is used to form a shear flow; the waste liquid bottle is used to collect the waste algae cell solution flowing out of the microchannel outlet; the fluorescence microscope is used to create a fluorescence field environment, induce the algae cells to produce characteristic fluorescence signals, and simultaneously achieve microscopic image amplification and filter out other stray light; the high-speed camera is used to capture a sequence of images of the algae cells in the shear flow.

[0007] Furthermore, the inlet and outlet of the microchannel are connected to the catheter via a Luer connector.

[0008] Furthermore, the microchannel is a rectangular parallelepiped structure with a length of 5 cm, a width of 600 μm, and a height of 150 μm; the microchannel is cast with PDMS material or etched with silicon material.

[0009] The present invention also discloses a method for measuring the swimming characteristics of algae cells in shear flow, the method comprising the following steps:

[0010] Step 1: Prepare algae cell solution of a certain concentration, connect the experimental device and check the air tightness of the experimental device;

[0011] Step 2: Adjust the position of the microchannel so that the center of the high-speed camera frame corresponds to the center of the microchannel, and the front and rear walls of the microchannel are parallel to the long frame of the frame;

[0012] Step 3: Determine the average flow rate according to the experimental working conditions, use a pressure pump to set the pressure in the liquid storage bottle, and continuously adjust the pressure according to the real-time flow rate monitored by the flow meter until the measured flow rate remains stable and consistent with the required average flow rate, thereby creating a stable shear flow;

[0013] Step 4: First, use a high-speed camera to capture an image in a bright field environment to calibrate the front and back walls of the microchannel, which correspond to the upper and lower boundaries of the captured image, respectively. Then, turn off the light source and capture a sequence of images in a fluorescent field environment. Each set of experiments is recorded for five minutes. Repeat the experiment multiple times until tens of thousands of valid algal cell movement trajectories are obtained.

[0014] Step 5: Process the captured image sequence, set diameter and brightness thresholds to identify algae cells, extract the coordinate data of the algae cell movement trajectory, and remove the trajectory outside the observation area according to the upper and lower boundaries of the calibrated captured image, and only retain the trajectory within the observation area;

[0015] Step 6: Obtain the distribution of the migration velocity V of the algae cells by observing the movement trajectory of the algae cells, and calculate the algae cell flow velocity V by combining the analytical method. flow The distribution of the algae cells in the shear flow is then calculated to obtain the swimming characteristics, including their own swimming speed V s and angular velocity ω; specifically comprising the following steps:

[0016] Step 61, calculate the migration velocity component of the algae cells: Based on the position coordinates of the algae cell movement trajectory observed in the experiment, except for the first point which uses forward difference and the last point which uses backward difference, the other points on the trajectory are calculated using the central difference format to obtain the migration velocity component V of the algae cells at different positions on each trajectory. x 、V y :

[0017] The first point:

[0018]

[0019] One last point:

[0020]

[0021] Other points:

[0022]

[0023] Where: x, y are the coordinates of the algae cell, and their subscripts represent the coordinates of different points, μm; V x 、V y are the migration velocity components, respectively, and their subscripts represent the migration velocity components at different points, μm / s; Δt is the time interval between adjacent points on the trajectory, s;

[0024] Step 62: Calculate the flow velocity distribution of algae cells: In a shear flow environment, the flow velocity at different positions along the width of the microchannel has a component V in the y direction of 0 and a component V in the x direction of 0. flow_xThe calculation formula is obtained by analytical method:

[0025]

[0026]

[0027] Where: a and b are half of the width and height of the microchannel, μm; is the pressure, Kgμm -1 s -2 ; μ is the dynamic viscosity of the liquid, Kgμm -1 s -1 ; i is the index variable for series summation; Q is the average flow rate, μm 3 / s;

[0028] Step 63: Calculate the algae cell's own swimming speed and its components: The migration speed V of the algae cell in the shear flow is divided into two parts. One is the swimming speed V s , that is, the swimming speed of algal cells actively generated by flagella, and the second is the flow velocity V flow , which is the water flow speed at the location of the algae cells; the migration speed V is the swimming speed V s , flow velocity V flow The superposition of , that is:

[0029] V=V s +V flow (6)

[0030] Where: V, V s 、V flow The unit is μm / s;

[0031] According to the migration speed of algae cells and the flow velocity at their location, the swimming speed V of the algae cells themselves is calculated. s and its component V s_x 、V s_y , the calculation formula is as follows:

[0032] V s_x =V x -V flow_x (7)

[0033] V s_y =V y (8)

[0034]

[0035] Step 64, calculate the angular velocity of the algae cell: calculate the moving direction θ according to the component of the swimming velocity of the algae cell, and the calculation formula is:

[0036]

[0037] According to the movement direction of each algae cell trajectory at different times, the change in the movement direction of the algae cell is calculated to obtain the angular velocity ω of the algae cell. The calculation method is to use the central difference format for the other points on the trajectory except for the forward difference format for the first point and the backward difference format for the last point:

[0038] The first point:

[0039]

[0040] One last point:

[0041]

[0042] Other points:

[0043]

[0044] Where: θ is the direction of movement of the algae cell, rad; ω is the angular velocity of the algae cell, rad / s; the subscripts represent the direction of movement and angular velocity at different points;

[0045] Step 65, measuring the swimming characteristics of algae cells: Based on the analysis of a large number of algae cell motion trajectories, the swimming speed and angular velocity of the algae cells at different positions along the width of the microchannel are counted and averaged to obtain the distribution of the swimming speed and angular velocity of the algae cells along the width of the microchannel. This realizes the measurement of the swimming characteristics of the algae cells under different shear rates.

[0046] Furthermore, the concentration of the algae cell solution prepared in step 1 is 1.2×10 5 pcs / ml.

[0047] Furthermore, the criteria for determining the effective algal cell trajectory in step 4 are:

[0048] 1) The duration of recording the trajectory of algal cells is greater than 10 seconds;

[0049] 2) The recorded trajectories do not include stationary trajectories and trajectories of impurities adhering to certain areas.

[0050] Furthermore, the diameter threshold in step 5 is set according to the algae cell type, and different types of algae cells have different sizes; the brightness threshold is set according to the wavelength, intensity and exposure time of the laser.

[0051] Furthermore, the large number of algae cell movement trajectories in step 65 is at least 10,000 algae cell movement trajectories.

[0052] The beneficial effects of the present invention are as follows:

[0053] 1. The present invention uses a pressure pump to create shear flow. The pressure pump outputs a constant pressure, driving the stable flow of algae liquid based on the pressure difference between the inside and outside of the sealed liquid storage bottle, achieving pulse-free fluid delivery. Compared to commonly used syringe pumps, the pressure pump has higher precision and better stability, thus ensuring the reliability of the shear flow environment during the experiment. In addition, the pressure pump is connected to a non-contact, highly sensitive flow meter, allowing real-time monitoring of flow changes during the experiment and appropriate adjustment of the pressure pump's output pressure.

[0054] 2. The present invention obtains the distribution of the migration velocity V of the algae cells by observing the movement trajectory of the algae cells, and calculates the algae cell flow velocity V by combining the analytical method. flow The distribution of the algae cell's own swimming speed V is then calculated. s and angular velocity ω, which enables the measurement of the swimming characteristics of algal cells;

[0055] 3. The present invention achieves high-precision measurement of the movement behavior of algal cells in shear flow, combining experimental methods with analytical methods, filling the gap in previous studies that could not obtain the swimming characteristics of algal cells themselves, such as swimming speed and angular velocity, and provides technical support for the development of microbial hydraulics at a more detailed microscopic scale.

[0056] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 Schematic diagram of the experimental device structure;

[0058] Figure 2 Schematic diagram of the microchannel structure;

[0059] Figure 3 This is a partial trajectory diagram of the algae cell movement observed in Example 1;

[0060] Figure 4 is the algae cell migration velocity component V in Example 1 x distribution map;

[0061] Figure 5 is the swimming velocity component V of the algae cell itself in Example 1 s_x distribution map;

[0062] Figure 6 is the swimming velocity component V of the algae cell itself in Example 1 s_y distribution map;

[0063] Figure 7 This is the distribution diagram of the angular velocity ω of the algae cells in Example 1.

[0064] In the figure: 1. Pressure pump; 2. Air pressure source; 3. Liquid storage bottle; 4. Flow meter; 5. Microchannel; 6. Luer connector; 7. Catheter; 8. Waste liquid bottle. DETAILED DESCRIPTION

[0065] The present invention discloses an experimental device and method for measuring the swimming characteristics of algae cells in shear flow, such as Figure 1 As shown, the experimental apparatus includes an air pressure source 2, a pressure pump 1, a liquid reservoir 3, a flowmeter 4, a microchannel 5, and a waste liquid bottle 8, which are connected in sequence. The air pressure source and the pressure pump, and the pressure pump and the liquid reservoir are connected by connecting tubes. The liquid reservoir and the flowmeter, the flowmeter and the inlet of the microchannel, and the outlet of the microchannel and the waste liquid bottle are connected by a conduit 7. The inlet and outlet of the microchannel and the conduit are connected by Luer connectors 6. The apparatus also includes a connected fluorescence microscope and a high-speed camera. The high-speed camera is mounted below the stage of the fluorescence microscope, and the microchannel is set on the stage of the fluorescence microscope. The air pressure source provides the basic pressure for the pressure pump; the pressure pump outputs a set constant pressure to create an internal and external pressure difference in the liquid storage bottle; the liquid storage bottle is closed and contains algae cell solution. Under the action of the internal and external pressure difference, the algae cell solution is transported to the microchannel through the catheter to form a shear flow; the flow meter is used to monitor the flow rate pumped in by the pressure pump in real time; the microchannel is the area where the algae solution flows, and cooperates with the pressure pump to create a stable and precise shear flow; the waste liquid bottle is used to collect the waste algae cell solution flowing out of the microchannel outlet; the fluorescence microscope is used to create a fluorescence field environment, induce the algae cells to produce characteristic fluorescence signals, and simultaneously achieve microscopic image amplification and filter out other stray light; the high-speed camera is used to capture the image sequence of algae cells in the shear flow.

[0066] like Figure 2 As shown, the microchannel is a rectangular parallelepiped structure with a length of 5 cm, a width of 600 μm, and a height of 150 μm. The microchannel is generally cast with PDMS material or etched with silicon material.

[0067] The present invention also discloses a method for measuring the swimming characteristics of algae cells in shear flow, the method comprising the following steps:

[0068] Step 1: Prepare algae cell solution of a certain concentration, connect the experimental device and check the air tightness of the experimental device;

[0069] Step 2: Adjust the position of the microchannel so that the center of the high-speed camera's frame corresponds to the center of the microchannel, the observation area is between the channel entrance and exit, and the front and rear walls of the microchannel are parallel to the long frame of the frame;

[0070] Step 3: Determine the average flow rate (or shear rate) according to the experimental conditions, use a pressure pump to set the pressure in the liquid storage bottle, and continuously adjust the pressure according to the real-time flow rate monitored by the flow meter until the measured flow rate remains stable and consistent with the required average flow rate, thereby creating a stable shear flow;

[0071] Step 4: First, use a high-speed camera to capture an image in brightfield conditions to demarcate the front and back walls of the microchannel, corresponding to the upper and lower boundaries of the image, respectively. Then, turn off the light source and capture a sequence of images in a fluorescent field. Each experiment lasts five minutes. Repeat the experiment until tens of thousands of valid algal cell trajectories are captured. Typically, the frame rate is 100, meaning 30,000 images are captured per experiment.

[0072] Specifically, the effective algae cell motion trajectory refers to the long-term algae cell motion trajectory within the observation area, which can reflect the normal movement of algae cells in shear flow. The following conditions must be met:

[0073] 1) The duration of recording the trajectory of algal cells should be greater than 10 seconds (the duration can be adjusted according to the specific experimental conditions);

[0074] 2) The recorded trajectories do not include trajectories of algae cells with weak motility (such as those that are stationary) and trajectories of algae cells that are misidentified (such as those that are attached to impurities in certain areas).

[0075] Step 5: Use the Trackmate open-source program to process the recorded image sequence, set appropriate diameter and brightness thresholds to identify algal cells, extract the coordinate data of the algal cell movement trajectory, and remove the trajectory outside the observation area based on the upper and lower boundaries of the calibrated captured image, retaining only the trajectory within the observation area;

[0076] The diameter threshold is set according to the algae cell type, as different algae cell types have different sizes. The brightness threshold is set according to the laser wavelength, intensity, and exposure time.

[0077] Step 6: Obtain the distribution of the migration velocity V of the algae cells by observing the movement trajectory of the algae cells, and calculate the algae cell flow velocity V by combining the analytical method. flow The distribution of the algae cells in the shear flow is then calculated to obtain the swimming characteristics, including their own swimming speed V s and angular velocity ω; specifically comprising the following steps:

[0078] Step 61, calculate the migration velocity component of the algae cells: Based on the position coordinates of the algae cell movement trajectory observed in the experiment, except for the first point which uses forward difference and the last point which uses backward difference, the other points on the trajectory are calculated using the central difference format to obtain the migration velocity component V of the algae cells at different positions on each trajectory. x、V y :

[0079] The first point:

[0080]

[0081] One last point:

[0082]

[0083] Other points:

[0084]

[0085] Where: x, y are the coordinates of the algae cell, and their subscripts represent the coordinates of different points, μm; V x 、V y are the migration velocity components respectively, and their subscripts represent the migration velocity components at different points, μm / s; Δt is the time interval between adjacent points on the trajectory, s.

[0086] Step 62: Calculate the flow velocity distribution of algae cells: In a shear flow environment, the flow velocity at different positions along the width of the microchannel has a component in the y direction of 0 and a component in the x direction, i.e., V flow_x The calculation formula is obtained by analytical method:

[0087]

[0088]

[0089] Where: a and b are half of the width and height of the microchannel, μm; is the pressure, Kgμm -1 s -2 ; μ is the dynamic viscosity of the liquid, Kgμm -1 s -1 ; i is the index variable for series summation; Q is the average flow rate, μm 3 / s.

[0090] Step 63: Calculate the algae cell's own swimming speed and its components: The migration speed V of the algae cell in the shear flow is divided into two parts. One is the swimming speed V s , that is, the swimming speed of algal cells actively generated by flagella, and the second is the flow velocity V flow , which is the water flow speed at the location of the algae cells; the migration speed V is the swimming speed V s , flow velocity V flow The superposition of , that is:

[0091] V=V s +V fl ow (6)

[0092] Where: V, V s 、V flow The unit is μm / s.

[0093] According to the migration speed of algae cells and the flow velocity at their location, the swimming speed V of the algae cells themselves is calculated. s and its component V s_x 、V s_y , the calculation formula is as follows:

[0094] V s_x =V x -V flow_x (7)

[0095] V s_y =V y (8)

[0096]

[0097] Step 64, calculate the angular velocity of the algae cell: calculate the moving direction θ according to the component of the swimming velocity of the algae cell, and the calculation formula is:

[0098]

[0099] According to the movement direction of each algae cell trajectory at different times, the change in the movement direction of the algae cell is calculated to obtain the angular velocity ω of the algae cell. The calculation method is the same as the calculation speed. Except for the first point using forward difference and the last point using backward difference, the other points on the trajectory are calculated using the central difference format:

[0100] The first point:

[0101]

[0102] One last point:

[0103]

[0104] Other points:

[0105]

[0106] Where: θ is the direction of movement of the algae cell, rad; ω is the angular velocity of the algae cell, rad / s; the subscripts represent the movement direction and angular velocity at different points.

[0107] Step 65: Measure algal cell swimming characteristics: Because the water velocity along the width of the microchannel is parabolic, the shear rate varies at different locations along the width. By analyzing a large number of algal cell motion trajectories (at least 10,000), the algal cell swimming speed and angular velocity at different locations along the width of the microchannel are calculated and averaged to obtain the distribution of the algal cell swimming speed and angular velocity across the width of the microchannel. This allows for measurement of the algal cell swimming characteristics at different shear rates.

[0108] Example 1

[0109] This embodiment is an application example of the above method.

[0110] The concentration of the algae cell solution configured in this embodiment is 1.2×10 5 / ml, the algae cell type used is Heterosigma akashiwo, with a cell diameter of about 10 μm. In this example, the average flow rate is 9×10 6 μm 3 Taking the shear flow of / s as an example, the swimming characteristics of algae cells are measured.

[0111] The above experimental device was used to observe the trajectory of algal cells. Figure 3 The figure shows a randomly selected portion of the trajectory. The circle in the figure indicates the initial position of the trajectory. The diameter threshold is set to 12 pixels and the brightness threshold is set to 20. Figure 4 is the algal cell migration velocity component V measured by experimental method x Distribution map. Figure 5 、 Figure 6 are the algae cell swimming velocity components V obtained by the above method. s_x 、V s_y Distribution map. Figure 7 The distribution diagram of the angular velocity ω of algae cells obtained by the above method.

[0112] Finally, it should be noted that the above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Although the present invention has been described in detail with reference to the preferred arrangement scheme, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for measuring the swimming characteristics of algal cells in shear flow, characterized in that: The method is based on an experimental device, which includes an air pressure source, a pressure pump, a liquid storage bottle, a flow meter, a microchannel, and a waste liquid bottle, which are connected in sequence. The air pressure source and the pressure pump, and the pressure pump and the liquid storage bottle are all connected via connecting pipes. The liquid storage bottle and the flow meter, the flow meter and the inlet of the microchannel, and the outlet of the microchannel and the waste liquid bottle are all connected via conduits. The device also includes a connected fluorescence microscope and a high-speed camera, the high-speed camera is installed below the stage of the fluorescence microscope, and the microchannel is set on the stage of the fluorescence microscope. The air pressure source is used to provide a base pressure for the pressure pump; the pressure pump is used to output a set constant pressure to create an internal and external pressure difference in the liquid storage bottle. The liquid storage bottle is sealed and contains algae cell solution. Under the action of the internal and external pressure difference, the algae cell solution is transported to the microchannel through the catheter to form a shear flow. The flow meter is used to monitor the flow rate of the pressure pump in real time; the microchannel is used to form a shear flow; the waste liquid bottle is used to collect the algae cell waste solution flowing out of the microchannel outlet; the fluorescence microscope is used to create a fluorescence field environment, induce the algae cells to generate characteristic fluorescence signals, and simultaneously achieve microscopic image amplification and filter out other stray light; the high-speed camera is used to capture a sequence of images of the algae cells in the shear flow; The method comprises the following steps: Step 1: Prepare algae cell solution of a certain concentration, connect the experimental device and check the air tightness of the experimental device; Step 2: Adjust the position of the microchannel so that the center of the high-speed camera frame corresponds to the center of the microchannel, and the front and rear walls of the microchannel are parallel to the long frame of the frame; Step 3: Determine the average flow rate according to the experimental working conditions, use a pressure pump to set the pressure in the liquid storage bottle, and continuously adjust the pressure according to the real-time flow rate monitored by the flow meter until the measured flow rate remains stable and consistent with the required average flow rate, thereby creating a stable shear flow; Step 4: First, use a high-speed camera to capture an image in a bright field environment to calibrate the front and back walls of the microchannel, which correspond to the upper and lower boundaries of the captured image, respectively. Then, turn off the light source and capture a sequence of images in a fluorescent field environment. Each set of experiments is recorded for five minutes. Repeat the experiment multiple times until tens of thousands of valid algal cell movement trajectories are obtained. Step 5: Process the captured image sequence, set diameter and brightness thresholds to identify algae cells, extract the coordinate data of the algae cell movement trajectory, and remove the trajectory outside the observation area according to the upper and lower boundaries of the calibrated captured image, and only retain the trajectory within the observation area; Step 6: Obtain the distribution of the migration velocity V of the algae cells by observing the movement trajectory of the algae cells, and calculate the algae cell flow velocity V by combining the analytical method. flow The distribution of the algae cells in the shear flow is then calculated to obtain the swimming characteristics, including their own swimming speed V s and angular velocity ω; specifically comprising the following steps: Step 61, calculate the migration velocity component of the algae cells: Based on the position coordinates of the algae cell movement trajectory observed in the experiment, except for the first point which uses forward difference and the last point which uses backward difference, the other points on the trajectory are calculated using the central difference format to obtain the migration velocity component V of the algae cells at different positions on each trajectory. x 、V y : The first point: One last point: Other points: Where: x, y are the coordinates of the algae cell, and their subscripts represent the coordinates of different points, μm; V x 、V y are the migration velocity components, respectively, and their subscripts represent the migration velocity components at different points, μm / s; Δt is the time interval between adjacent points on the trajectory, s; Step 62: Calculate the flow velocity distribution of algae cells: In a shear flow environment, the flow velocity at different positions along the width of the microchannel has a component V in the y direction of 0 and a component V in the x direction of 0. flow_x The calculation formula is obtained by analytical method: Where: a and b are half of the width and height of the microchannel, μm; is the pressure, Kgμm -1 s -2 ; μ is the dynamic viscosity of the liquid, Kgμm -1 s -1 ; i is the index variable for series summation; Q is the average flow rate, μm 3 / s; Step 63: Calculate the algae cell's own swimming speed and its components: The migration speed V of the algae cell in the shear flow is divided into two parts. One is the swimming speed V s , that is, the swimming speed of algal cells actively generated by flagella, and the second is the flow velocity V flow , which is the water flow speed at the location of the algae cells; the migration speed V is the swimming speed V s , flow velocity V flow The superposition of , that is: V=V s +V flow (6) Where: V, V s 、V flow The unit is μm / s; According to the migration speed of algae cells and the flow velocity at their location, the swimming speed V of the algae cells themselves is calculated. s and its component V s_x 、V s_y , the calculation formula is as follows: V s_x =V x -V flow_x (7) V s_y =V y (8) Step 64, calculate the angular velocity of the algae cell: calculate the moving direction θ according to the component of the swimming velocity of the algae cell, and the calculation formula is: According to the movement direction of each algae cell trajectory at different times, the change in the movement direction of the algae cell is calculated to obtain the angular velocity ω of the algae cell. The calculation method is to use the central difference format for the other points on the trajectory except for the forward difference format for the first point and the backward difference format for the last point: The first point: One last point: Other points: Where: θ is the direction of movement of the algae cell, rad; ω is the angular velocity of the algae cell, rad / s; the subscripts represent the direction of movement and angular velocity at different points; Step 65, measuring the swimming characteristics of algae cells: Based on the analysis of a large number of algae cell motion trajectories, the swimming speed and angular velocity of the algae cells at different positions along the width of the microchannel are counted and averaged to obtain the distribution of the swimming speed and angular velocity of the algae cells along the width of the microchannel. This realizes the measurement of the swimming characteristics of the algae cells under different shear rates.

2. The method for measuring the swimming characteristics of algal cells in shear flow according to claim 1, characterized in that: The inlet and outlet of the microchannel are connected to the catheter via a Luer connector.

3. The method for measuring the swimming characteristics of algal cells in shear flow according to claim 1, characterized in that: The microchannel is a rectangular parallelepiped structure with a length of 5 cm, a width of 600 μm, and a height of 150 μm. The microchannel is cast with PDMS material or etched with silicon material.

4. The method for measuring the swimming characteristics of algal cells in shear flow according to claim 1, characterized in that: The concentration of the algae cell solution prepared in step 1 is 1.2×10 5 pcs / ml.

5. The method for measuring the swimming characteristics of algal cells in shear flow according to claim 1, characterized in that: The criteria for determining the effective algal cell trajectory in step 4 are: 1) The duration of recording the trajectory of algal cells is greater than 10 seconds; 2) The recorded trajectories do not include stationary trajectories and trajectories of impurities adhering to certain areas.

6. The method for measuring the swimming characteristics of algal cells in shear flow according to claim 1, characterized in that: The diameter threshold in step 5 is set according to the algae cell type, and different types of algae cells have different sizes; the brightness threshold is set according to the laser band, strength and exposure time.

7. The method for measuring the swimming characteristics of algae cells in shear flow according to claim 1, characterized in that: The large number of algae cell movement trajectories in step 65 is at least 10,000 or more algae cell movement trajectories.

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