Microalgae cell swelling inertia screening and impedance detection integrated microfluidic device

Abstract

The invention provides a microalgae cell swelling inertia screening and impedance detection integrated micro-fluidic device, and relates to the technical field of microalgae cell screening and detection. The microalgae cell swelling inertia screening and impedance detection integrated micro-fluidic device comprises a signal processing unit, the substrate is ITO (Indium Tin Oxide) conductive glass; the main micro-channel is of a micro-channel structure which is formed in a polydimethylsiloxane (PDMS) layer and is bonded on the substrate. According to the invention, the passive sorting module based on the expansion and contraction inertia effect and the differential impedance detection module are integrated in the single micro-fluidic chip, so that the full-process automation of'sample introduction-sorting-detection-output 'is realized. Sample loss, cross contamination and activity damage are avoided, interference of mixed cell populations on subsequent impedance signals is effectively eliminated through pre-sorting, and the accuracy of target microalgae detection is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of microalgae cell screening and detection technology, specifically to an integrated microfluidic device for screening and impedance detection of microalgae cell swelling and shrinkage inertia. Background Technology

[0002] Microalgae have wide applications in biotechnology, environmental remediation, medicine, and bio-microrobotics, making precise detection of their phenotypes and activities crucial. Currently, relevant detection methods can be mainly divided into two categories: "static detection" and "dynamic detection." Static detection techniques, such as patch-clamp, electrospinning, and dielectrophoresis, can achieve high-precision electrical property analysis at the single-cell level, but are difficult to apply to large-sample, high-throughput analysis due to severe interference from neighboring cells, extremely low sample throughput, and complex and time-consuming operations. Dynamic detection techniques, on the other hand, utilize flow systems, allowing microalgae to sequentially pass through the detection zone, enabling panoramic characterization of the cell population during continuous flow. Common dynamic methods include light scattering, optical imaging, and impedance flow cytometry. Light scattering technology obtains cell size, particle size, and cytoplasmic information by measuring changes in the intensity and angle of scattered light from cells, but it relies on high-power laser sources, which can easily cause cell membrane damage and cytoplasmic leakage. Optical imaging technology can directly acquire cell morphology, contour, and substructure information, but it requires high-performance microscopy systems and high-resolution cameras, making the equipment expensive and demanding in terms of operation and maintenance, thus failing to meet the needs of rapid on-site detection. In contrast, impedance cytometry extracts electrical information based on the impedance changes caused by cells passing through the microelectrode detection zone. It boasts advantages such as simple system structure, portability, no need for fluorescent labeling, and minimal impact on cell viability, showing great potential in the dynamic detection of microalgae. However, when dealing with mixed microalgae cells of various types and sizes often found in real-world samples, different cell types and sizes may produce similar impedance responses, resulting in significant signal overlap and making it difficult to accurately extract specific electrical information of target cells from mixed populations. To address these issues, cell sorting as a pre-processing step to separate mixed populations is an effective way to improve the targeting and accuracy of subsequent impedance detection. Passive inertial sorting technology, with its advantages of high throughput, no need for external field assistance, and the ability to separate cells of different sizes solely through channel structure design and flow rate adjustment, has become an ideal sorting solution. Nevertheless, existing technologies often implement sorting and detection functions separately on independent chips, which not only increases sample transfer loss and contamination risks but also increases the overall system size and reduces integration, making it difficult to achieve integrated rapid analysis from "sample in" to "result out." Therefore, there is an urgent need to develop a microfluidic device that can achieve a high degree of integration between efficient sorting of microalgae and accurate impedance detection, in order to overcome the problems of cumbersome operation, low integration, and difficulty in dealing with mixed samples and rapid on-site detection requirements in the existing technology. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides an integrated microfluidic device for screening microalgal cell swelling and contraction inertia and detecting impedance, thus solving the problems existing in the prior art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: an integrated microfluidic device for screening and impedance detection based on the inertial swelling and contraction of microalgal cells, including a signal processing unit; The substrate is ITO conductive glass; The main microchannel is a microchannel structure formed within a polydimethylsiloxane (PDMS) layer and bonded to the substrate; The main microchannel has a sample inlet at one end and a seventh sample outlet at the other end; Within the main microchannel, an expansion-contraction cavity array structure, a buffer deceleration zone, and an impedance detection module are sequentially arranged from upstream to downstream along the fluid flow direction. The expansion-contraction cavity array structure consists of multiple periodically arranged rectangular expansion cavities connected in series with rectangular contraction cavities, and is used to passively sort microalgal cells of different particle sizes based on fluid inertial force. The buffer deceleration zone is located downstream of the expansion-contraction chamber array structure and includes a first sample outlet and a second sample outlet, a third sample outlet and a fourth sample outlet, and a fifth sample outlet and a sixth sample outlet symmetrically distributed along both sides of the main microchannel. It is used to divert part of the fluid to reduce the flow rate of the main channel. The impedance detection module is located downstream of the buffer deceleration zone and includes a straight microchannel, two pairs of coplanar electrodes, and an external impedance measurement circuit. The straight microchannel connects the buffer deceleration zone and the seventh sample outlet. The two pairs of coplanar electrodes are located between the substrate and the main microchannel and are directly below the top view projection of the straight microchannel. Each pair of coplanar electrodes includes an excitation electrode and a receiving electrode for acquiring differential impedance signals flowing through the cells. The external impedance measurement circuit is electrically connected to the coplanar electrode and is used to apply an excitation signal and process impedance change signals. The signal processing unit is communicatively connected to the external impedance measurement circuit and is used to analyze the processed impedance signal to identify the type, particle size, or physiological state of microalgal cells.

[0005] Preferably, in the buffer deceleration zone, the first and second sample outlets are symmetrically arranged with respect to the center line of the main microchannel, and the angle between their connecting channels and the flow direction of the main channel is 25 to 45 degrees; the arrangement of the third, fourth, fifth, and sixth sample outlets is the same as that of the first and second sample outlets.

[0006] Preferably, the rectangular expansion cavity has a width of 0.8 mm and a length of 1.5 mm; the rectangular contraction cavity has a width of 0.04 mm and a length of 1 mm; and the main microchannel has a height of 0.07 mm.

[0007] Preferably, the width of both the excitation electrode and the receiving electrode of the coplanar electrode is 100 μm, and the distance between the excitation electrode and the receiving electrode in the same pair of electrodes is 100 μm.

[0008] Preferably, the external impedance measurement circuit includes a lock-in amplifier and a differential amplifier; the lock-in amplifier is used to apply an AC excitation signal with a frequency range of 50kHz to 1MHz and a voltage amplitude of 0.1V to 1V to the excitation electrode; the differential amplifier is used to amplify the differential signals acquired from the two pairs of receiving electrodes to suppress common-mode noise.

[0009] Preferably, the end of the expansion-contraction chamber array structure is directly connected to the beginning of the buffer deceleration zone, and the first and second sample outlets of the buffer deceleration zone also serve as sorting outlets of the expansion-contraction chamber array structure to discharge small-sized microalgae cells or impurities that have migrated to the sidewall of the channel after sorting.

[0010] Preferably, the device is configured to inject a microalgal cell sample suspension from the inlet at a flow rate of 50 µL / min to 200 µL / min under the drive of an external injection pump, and sequentially perform inertial sorting, buffer deceleration and impedance detection.

[0011] Preferably, the signal processing unit is specifically configured to: distinguish the cell activity state based on the difference in amplitude characteristics of the impedance signal pulses generated when live microalgal cells and dead cells pass through the straight microchannel.

[0012] Preferably, the polydimethylsiloxane (PDMS) layer is permanently sealed to the ITO conductive glass substrate through a plasma bonding process to form a closed microfluidic system.

[0013] Preferably, the overall layout of the main microchannel is as follows: the sample inlet, the expansion-contraction chamber array structure, the buffer deceleration zone, the straight microchannel and the seventh sample outlet are arranged in sequence to form an integrated flow path of "sample inlet-sorting-deceleration-detection-sample outlet".

[0014] This invention provides an integrated microfluidic device for screening and impedance detection based on the swelling and contraction inertia of microalgal cells. It offers the following advantages: 1. Compared with existing technologies, this microfluidic device integrates microalgal cell swelling and contraction inertia screening and impedance detection. It creatively integrates a passive sorting module based on the swelling and contraction inertia effect with a differential impedance detection module into a single microfluidic chip, achieving full automation of the "sample introduction-sorting-detection-output" process. This design not only avoids sample loss, cross-contamination, and activity damage common in traditional multi-step operations, but also effectively eliminates the interference of mixed cell populations on subsequent impedance signals through pre-sorting, significantly improving the accuracy of target microalgae detection. It truly achieves precise, label-free, and non-destructive analysis of microalgae species, particle size, and activity.

[0015] 2. Compared with existing technologies, this microfluidic device integrates microalgal cell swelling and shrinkage inertial screening and impedance detection. It features a compact structure and simple operation, adapting to the sorting needs of microalgae of different particle sizes simply by adjusting the flow rate, and supporting continuous high-throughput processing. Furthermore, the entire system only requires an electric field, eliminating the need for other complex external fields (such as light or magnetism) or fluorescent labeling, thus reducing equipment costs and operational complexity while maintaining high cell viability. This highly integrated "lab-on-a-chip" platform demonstrates the unique advantages of microfluidic technology in automated and miniaturized bioanalysis, providing a novel, efficient, reliable, and easily field-deployable technological tool for biomedical research, environmental aquatic microbial monitoring, and the development of microrobots driven by microalgae, with broad application prospects. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 For the present invention Figure 1 A magnified view of a section at point A in the middle; Figure 3 This is a schematic diagram of cell separation according to the present invention; Figure 4 This is a schematic diagram of cell detection according to the present invention; Figure 5 This is a schematic diagram of the cell flow state within the expansion-contraction cavity array structure of the present invention; Figure 6 This is a schematic diagram of the cell flow state at the sorting outlet of the expansion-contraction cavity array structure of the present invention; Figure 7 This is the filtered cell impedance detection signal of this invention; Figure 8 This is a diagram showing the system setup of the present invention; Figure 9 This is a schematic diagram of the device structure of the present invention.

[0017] Among them, 1. substrate; 2. main microchannel; 3. sample inlet; 4. first sample outlet; 5. second sample outlet; 6. third sample outlet; 7. fourth sample outlet; 8. fifth sample outlet; 9. sixth sample outlet; 10. seventh sample outlet; 11. rectangular expansion cavity; 12. rectangular contraction cavity; 13. straight microchannel; 14. coplanar electrode.

[0018] Detailed Description of Embodiments The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0019] like Figures 1 to 9 As shown in the figure, this invention provides an integrated microfluidic device for screening microalgal cell swelling and shrinkage inertia and impedance detection. The specific implementation details are as follows: To achieve device integration and miniaturization, and to provide a structural basis for electrical detection, the device includes a signal processing unit, a substrate 1, and a main microchannel 2. The substrate 1 is made of indium tin oxide (ITO) conductive glass. The main microchannel 2 is formed within a polydimethylsiloxane (PDMS) layer and permanently sealed to the ITO conductive glass substrate 1 via plasma bonding, forming a closed microfluidic system. Through this structure, utilizing the biocompatibility and light transmittance of PDMS, and the conductivity and surface smoothness of ITO glass, the microfluidic chip and embedded detection electrode are integrated into a single unit.

[0020] To establish a complete sample introduction and output pathway, the main microchannel 2 has an inlet 3 at one end and a seventh outlet 10 at the other. The inlet 3 is used to connect to an external injection pump to inject the microalgal cell sample suspension to be analyzed; the seventh outlet 10 is used to collect the target cells after the entire analysis process or to discharge waste liquid. This structure establishes a unidirectional, sequential flow direction for sample processing within the chip.

[0021] To sort mixed microalgae samples by particle size without labeling, an expansion-contraction chamber array structure is installed in the upstream section of the main microchannel 2 near the inlet 3. This structure consists of multiple periodically arranged rectangular expansion chambers 11 and rectangular contraction chambers 12 connected in series. The rectangular expansion chambers 11 have a width of 0.8 mm and a length of 1.5 mm; the rectangular contraction chambers 12 have a width of 0.04 mm and a length of 1 mm; and the main microchannel 2 has a height of 0.07 mm. When the sample suspension flows through at a specific flow rate, the periodic changes in the chamber structure induce specific fluid shear forces and wall lift (inertial lift). Through this structure, cells of different sizes migrate laterally due to differences in inertial forces: larger cells (such as the target Haematococcus pluvialis) approach the center of the channel, while smaller cells (such as impurity algae) approach the sides of the channel, thus achieving passive, non-destructive inertial sorting.

[0022] To receive the sorting results and achieve the physical separation of cells with different migration trajectories, the end of the expansion-contraction chamber array structure is directly connected to a buffer deceleration zone. This buffer deceleration zone has multiple pairs of sample outlets symmetrically arranged on both sides of the main microchannel 2, with the upstream pair being the first sample outlet 4 and the second sample outlet 5. These sample outlets directly serve as the sorting outlets of the expansion-contraction chamber array structure, with the first and second sample outlets 4 and 5 configured to separate small cells and impurities. Through this structure, small cells and impurities that have migrated to both sides are discharged from the system through the first and second sample outlets 4 and 5, while the target large cells remaining in the central flow continue to flow downstream, completing the initial screening and enrichment.

[0023] To reduce cell flow rate and improve the accuracy of subsequent electrical detection, the buffer deceleration zone also functions as a fluid diversion and deceleration area. This zone includes a third sample outlet 6, a fourth sample outlet 7, a fifth sample outlet 8, and a sixth sample outlet 9. These outlets are symmetrically distributed on both sides of the main microchannel 2, and the angle between their connecting channels and the main channel flow direction is between 25 and 45 degrees. When the fluid flows through, some of the fluid is diverted from these lateral outlets, effectively reducing the flow rate of the remaining sample in the main channel. Through this structure, the slower flow rate prolongs the time it takes for a single cell to pass through the downstream detection zone, enabling the detection system to acquire higher resolution impedance signals and significantly improve detection accuracy.

[0024] To perform impedance detection on sorted single cells, an impedance detection module is located downstream of the buffer deceleration zone. This module includes a straight microchannel 13, two pairs of coplanar electrodes 14, and an external impedance measurement circuit. The straight microchannel 13 connects the buffer deceleration zone and the seventh sample outlet 10. The two pairs of coplanar electrodes 14 are fabricated on an ITO substrate 1 and are precisely located directly below the top-view projection of the straight microchannel 13. Each pair of coplanar electrodes 14 includes an excitation electrode and a receiving electrode, both with a width of 100 μm and a spacing of 100 μm between electrodes within the same pair. Through this structure, when cells flow through the straight microchannel 13, the electric field between the electrodes is disturbed, generating impedance change signals related to cell electrical properties such as size and membrane integrity. The use of a differential electrode pair design effectively suppresses environmental common-mode noise.

[0025] To drive the detection and extraction of high-quality electrical signals, the device is connected to an external impedance measurement circuit. This circuit mainly consists of a lock-in amplifier and a differential amplifier. The lock-in amplifier applies an AC excitation signal with a frequency of 50 kHz to 1 MHz and an amplitude of 0.1 V to 1 V to the excitation electrode of the coplanar electrode 14. The differential amplifier receives and amplifies the differential signals from the two pairs of receiving electrodes. Through this structure, the lock-in amplifier can demodulate the minute impedance changes caused by cells with high sensitivity, while the differential amplifier suppresses common-mode interference while amplifying the effective signal, providing raw data with excellent signal-to-noise ratio for subsequent analysis.

[0026] To ultimately achieve automated cell identification, the device also includes a signal processing unit. This unit is communicatively connected to an external impedance measurement circuit and receives the processed impedance signal. The signal processing unit is configured to analyze the transient impedance pulse characteristics (such as amplitude) generated when each cell passes through. In particular, it can effectively distinguish the physiological activity state of cells based on the significant difference in impedance pulse amplitude generated by living cells (intact membranes) and dead cells (ruptured membranes). By comparing the signal characteristics with a preset database, cell type and particle size can be further identified.

[0027] To ensure device performance, its workflow has been optimized. The device is configured to be driven by an external injection pump to inject samples from inlet 3 at a flow rate of 50 µL / min to 200 µL / min. This flow rate range is key to balancing sorting efficiency and detection accuracy, ensuring continuous, automated, and efficient operation of the entire process from "sample injection" to "sample effluent" within the chip.

[0028] In summary, the overall layout of the main microchannel 2 of this microfluidic device is as follows: the sample inlet 3, the expansion-contraction chamber array structure, the buffer deceleration zone, the straight microchannel 13, and the seventh sample outlet 10 are arranged in sequence. Through the above layout, an integrated flow path of "sample injection-sorting-deceleration-detection-sample outlet" is physically realized, which greatly simplifies the operation and improves the reliability and throughput of the analysis.

[0029] III. Working Principle This invention is based on an integrated strategy of "pre-cleaning by inertial sorting and subsequent fine analysis by impedance detection," and its working principle is as follows: 1. Inertial Sorting and Sieving: The mixed microalgae sample is injected into the chip at an optimized flow rate of 50-200 µL / min, driven by an external injection pump. As it flows through the expansion-contraction chamber array structure, the inertial lift induced by the specific geometry causes cells of different sizes to migrate laterally. Larger cells are retained in the center, while smaller cells are shifted to the sides. At the end of the structure, smaller cells and impurities that have shifted to the sidewalls are directly discharged through the first outlet 4 and the second outlet 5 in the buffer deceleration zone, completing the first step of passive, label-free sieving.

[0030] 2. Flow Rate Buffering and Re-purification: The target cells enriched in the central flow enter the buffer and deceleration zone. This zone actively reduces the main channel flow rate through the diversion effect of multiple pairs of lateral sample outlets, creating conditions for subsequent high-precision detection. At the same time, the diversion process helps to further stabilize the flow field, ensuring that cells enter the detection zone in a single, uniform manner.

[0031] 3. Differential Impedance Detection: After deceleration, the single cells flow sequentially through the straight microchannel 13. Below it, two pairs of coplanar electrodes 14, under AC excitation provided by a lock-in amplifier, form a sensitive detection electric field. As the cell passes through, its dielectric properties perturb the electric field, generating a weak differential impedance signal. This signal is amplified by the differential amplifier and noise suppressed before being demodulated with high precision by the lock-in amplifier.

[0032] 4. Signal Processing and Recognition: The demodulated impedance pulse signal is transmitted to the signal processing unit. This unit analyzes the pulse's amplitude, waveform, and other characteristics. Based on the essential difference in impedance amplitude between live and dead cells, cell activity can be accurately determined. Furthermore, by comparing the signal characteristics with a database of known cell types' "electrical fingerprints," automated identification and counting of cell types and sizes can be achieved.

[0033] 5. Integrated Output: The entire "sorting-detection-analysis" process is automatically completed within a single integrated PDMS-ITO device. Ultimately, the physical sample of the target cell is obtained from the seventh sampling port 10, while its complete electrical characterization data is output by the signal processing unit. This invention achieves high-throughput, non-destructive, integrated phenotypic analysis of microalgal cells through microchannel structure design and multi-technology integration.

[0034] Explanation of detection principle: The detection area can be abstracted as an equivalent circuit, composed of the resistance and capacitance generated by the solution and the target algal cells. The signal generated within the detection area is transmitted to the computer via an external circuit. When cells pass through the detection area, they disturb the electric field and induce impedance signals, thus characterizing the microalgae. The entire detection area is equivalent to a circuit composed of capacitance and resistance. According to Maxwell's mixing theory, its equivalent complex permittivity is: in, The complex permittivity of the dielectric is represented by the dielectric constant. This represents the volume proportion of microalgal cells in the detection area. It is the Clausius-Mossotti factor.

[0035] The recombinant resistance of a cell-mixed system can be expressed as: Where S represents the electrode tip area, D is the electrode spacing, and k is the cell constant determined by cell geometry. According to Maxwell's approximation, the conductivity of the fluid-cell mixture is: The complex impedance of the square planar electrode is: The complex impedance within the electrical detection region can be expressed as: Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A microfluidic device integrating microalgal cell swelling and contraction inertial screening and impedance detection, characterized in that, include: Signal processing unit; Substrate (1), wherein the substrate (1) is ITO conductive glass; The main microchannel (2) is a microchannel structure formed in the polydimethylsiloxane (PDMS) layer and bonded to the substrate (1); One end of the main microchannel (2) is provided with a sample inlet (3), and the other end is provided with a seventh sample outlet (10). The main microchannel (2) is provided with an expansion-contraction cavity array structure, a buffer deceleration zone and an impedance detection module in sequence from upstream to downstream along the fluid flow direction; The expansion-contraction cavity array structure is composed of multiple periodically arranged rectangular expansion cavities (11) and rectangular contraction cavities (12) connected in series, which are used to passively sort microalgal cells of different particle sizes based on fluid inertial force. The buffer deceleration zone is located downstream of the expansion-contraction cavity array structure and includes a first sample outlet (4) and a second sample outlet (5), a third sample outlet (6) and a fourth sample outlet (7), and a fifth sample outlet (8) and a sixth sample outlet (9) symmetrically distributed along both sides of the main microchannel (2), which are used to divert part of the fluid to reduce the flow rate of the main channel; The impedance detection module is located downstream of the buffer deceleration zone and includes a straight microchannel (13), two pairs of coplanar electrodes (14) and an external impedance measurement circuit. The straight microchannel (13) connects the buffer deceleration zone and the seventh sample outlet (10). The two pairs of coplanar electrodes (14) are located between the substrate (1) and the main microchannel (2) and are located directly below the top view projection of the straight microchannel (13). Each pair of coplanar electrodes (14) includes an excitation electrode and a receiving electrode for collecting differential impedance signals flowing through the cells. The external impedance measurement circuit is electrically connected to the coplanar electrode (14) and is used to apply an excitation signal and process impedance change signals. The signal processing unit is communicatively connected to the external impedance measurement circuit and is used to analyze the processed impedance signal to identify the type, particle size, or physiological state of microalgal cells.

2. The integrated microfluidic device for screening and impedance detection of microalgal cell swelling and contraction inertia according to claim 1, characterized in that, In the buffer deceleration zone, the first sample outlet (4) and the second sample outlet (5) are symmetrically arranged with respect to the center line of the main microchannel (2), and the angle between their connecting channel and the flow direction of the main channel is 25 to 45 degrees; the arrangement of the third sample outlet (6), the fourth sample outlet (7), the fifth sample outlet (8), and the sixth sample outlet (9) is the same as that of the first sample outlet (4) and the second sample outlet (5).

3. The integrated microfluidic device for screening and impedance detection of microalgal cell swelling and contraction inertia according to claim 1, characterized in that, The rectangular expansion cavity (11) has a width of 0.8 mm and a length of 1.5 mm; the rectangular contraction cavity (12) has a width of 0.04 mm and a length of 1 mm; and the main microchannel (2) has a height of 0.07 mm.

4. The integrated microfluidic device for screening and impedance detection of microalgal cell swelling and contraction inertia according to claim 1, characterized in that, The width of both the excitation electrode and the receiving electrode of the coplanar electrode (14) is 100 μm, and the distance between the excitation electrode and the receiving electrode in the same pair of electrodes is 100 μm.

5. The integrated microfluidic device for microalgal cell swelling and contraction inertia screening and impedance detection according to claim 1, characterized in that, The external impedance measurement circuit includes a lock-in amplifier and a differential amplifier; the lock-in amplifier is used to apply an AC excitation signal with a frequency range of 50kHz to 1MHz and a voltage amplitude of 0.1V to 1V to the excitation electrode; the differential amplifier is used to amplify the differential signals acquired from the two pairs of receiving electrodes to suppress common-mode noise.

6. The integrated microfluidic device for screening and impedance detection of microalgal cell swelling and contraction inertia according to claim 1, characterized in that, The end of the expansion-contraction cavity array structure is directly connected to the beginning of the buffer deceleration zone, and the first sample outlet (4) and the second sample outlet (5) of the buffer deceleration zone also serve as the sorting outlets of the expansion-contraction cavity array structure to discharge the small-sized microalgae cells or impurities that have migrated to the side wall of the channel after sorting.

7. The integrated microfluidic device for screening and impedance detection of microalgal cell swelling and contraction inertia according to claim 1, characterized in that, The device is configured to inject a microalgal cell sample suspension from the inlet (3) at a flow rate of 50 µL / min to 200 µL / min under the drive of an external injection pump, and perform inertial sorting, buffer deceleration and impedance detection in sequence.

8. The integrated microfluidic device for microalgal cell swelling and contraction inertial screening and impedance detection according to claim 1, characterized in that, The signal processing unit is specifically configured to distinguish the active state of cells based on the difference in amplitude characteristics of the impedance signal pulses generated when live microalgae cells and dead cells pass through the straight microchannel (13).

9. The integrated microfluidic device for microalgal cell swelling and contraction inertial screening and impedance detection according to claim 1, characterized in that, The polydimethylsiloxane (PDMS) layer is permanently sealed to the ITO conductive glass substrate (1) by plasma bonding process to form a closed microchannel system.

10. The integrated microfluidic device for screening and impedance detection of microalgal cell swelling and contraction inertia according to claim 1, characterized in that, The overall layout of the main microchannel (2) is as follows: the inlet (3), the expansion-contraction cavity array structure, the buffer deceleration zone, the straight microchannel (13) and the seventh outlet (10) are arranged in sequence to form an integrated flow path of "inlet-sorting-deceleration-detection-outlet".

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