Microfluidic chip, microfluidic extraction system and extraction method

Abstract

This invention discloses a microfluidic chip, a microfluidic extraction system, and an extraction method, relating to the field of soil research technology. The microfluidic chip includes, from top to bottom, a sealing layer, a main chamber layer, a filter membrane layer, a secondary chamber layer, and a base plate, all connected in sequence. Each of the sealing layer, main chamber layer, filter membrane layer, and secondary chamber layer contains multiple processing spaces radially, and when stacked, there are at least three processing spaces radially. From the inside out, these spaces are a vortex mixing zone, a filtration separation zone, and a centrifugal enrichment zone. An inlet and an outlet are provided. The sample to be tested enters through the inlet and flows into the vortex mixing zone for vortex extraction. After extraction, the sample passes through the filter membrane layer to the main chamber layer, and under external force, moves from the main chamber layer to the filtration separation zone, finally reaching the centrifugal enrichment zone and being extracted through the outlet. This invention improves extraction efficiency and has a high degree of automation.

Description

Technical Field

[0001] This invention relates to the field of soil research technology, and in particular to a microfluidic chip, a microfluidic extraction system, and an extraction method. Background Technology

[0002] Traditional methods for extracting soluble heavy metals from soil in weakly acidic environments, such as the first step of the BCR or Tessier method, typically use weak acids (e.g., acetate solutions). However, these traditional methods generally suffer from the following technical problems: Excessive time consumption: Traditional extraction methods, especially those requiring inverted shaking, often require extraction times of up to 16 hours or longer to ensure complete dissolution of heavy metals, severely limiting detection efficiency and failing to meet the needs of rapid screening and emergency monitoring. Complex operation and high labor intensity: Traditional methods involve multiple steps, including sample weighing, adding the extraction solution, prolonged inverted shaking, centrifugation, and filtration. The entire process is cumbersome, requires extensive manual operation, is labor-intensive, and is prone to human error. Large and unportable equipment: Traditional laboratory equipment such as inverted shakers and centrifuges are bulky and typically require fixed locations in the laboratory, making rapid field or on-site detection difficult.

[0003] In recent years, ultrasonic-assisted extraction has been proposed as an alternative to reverse oscillation, offering a degree of speed. However, ultrasonic equipment also suffers from drawbacks such as large size and lack of portability. Furthermore, although ultrasound waves are inaudible to the human ear, their mechanical vibrations resonate with the device, resulting in significant noise that can negatively impact the laboratory environment. Most importantly, after ultrasonic extraction, subsequent solid-liquid separation processes such as centrifugation and filtration are still required, meaning true integration and automation are not achieved.

[0004] The limitations of existing technologies pose significant challenges to the rapid, accurate, and high-throughput detection of heavy metals in soil, particularly in fields such as agricultural environmental monitoring, food safety traceability, and contaminated site remediation assessment. There is an increasing need for more efficient, convenient, and intelligent pretreatment technologies. Therefore, a microfluidic chip, a microfluidic extraction system, and an extraction method are urgently needed to address these technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a microfluidic chip, a microfluidic extraction system, and an extraction method to solve the problems existing in the prior art, thereby achieving higher extraction efficiency and a higher degree of automation.

[0006] To achieve the above objectives, the present invention provides the following solution: This invention provides a microfluidic chip comprising, from top to bottom, a sealing layer, a main chamber layer, a filter membrane layer, a secondary chamber layer, and a base plate, all connected in sequence. Each of the sealing layer, the main chamber layer, the filter membrane layer, and the secondary chamber layer has multiple processing spaces radially, and when stacked, there are at least three processing spaces radially, which, from the inside out, are a vortex mixing zone, a filtration separation zone, and a centrifugal enrichment zone. The sealing layer has an inlet near its center and an outlet near its edge. The sample to be tested enters through the inlet and flows into the vortex mixing zone, where it undergoes vortex extraction. After extraction, the sample passes through the filter membrane layer to the secondary chamber layer and, under external force, returns from the secondary chamber layer to the main chamber layer, reaching the filtration separation zone and finally the centrifugal enrichment zone, where it is removed through the outlet.

[0007] In some embodiments, the sealing layer, the main chamber layer, the filter membrane layer, and the secondary chamber layer have multiple independent processing units along the circumferential direction, and each processing unit includes the vortex mixing zone, the filtration separation zone, the centrifugation enrichment zone, the sample inlet, and the sample outlet.

[0008] In some embodiments, the sealing layer includes a sealing upper layer, a sealing middle layer, and a sealing lower layer that are sequentially bonded together from top to bottom.

[0009] In some embodiments, the filter membrane layer includes an upper filter membrane layer, a middle filter membrane layer, and a lower filter membrane layer that are sequentially bonded together from top to bottom, wherein the upper filter membrane layer and the lower filter membrane layer can support the middle filter membrane layer.

[0010] In some embodiments, the filtration separation zone includes a first filtration separation zone and a second filtration separation zone in the radial direction, and both the first filtration separation zone and the second filtration separation zone are embedded with a secondary hydrophilic polytetrafluoroethylene filter membrane.

[0011] The present invention also provides a microfluidic extraction system, including a rotary drive device, a control system, and a microfluidic chip as described above. The output end of the rotary drive device can be connected to and fixed to the microfluidic chip. The rotary drive device is used to drive the microfluidic chip to perform vortex extraction or centrifugal separation. The control system is electrically connected to the rotary drive device.

[0012] In some embodiments, the device further includes a vortex base, a centrifugal base, and multiple positioning holes. The multiple positioning holes are distributed along the diameter direction of the microfluidic chip, and one positioning hole is provided at the center position. Positioning posts are provided on the vortex base and the centrifugal base. The positioning posts can be inserted into the positioning holes. Both the vortex base and the centrifugal base can be fixedly connected to the output end of the rotary drive device.

[0013] In some embodiments, the system also includes a power module, a display screen, and multiple control buttons. The power module provides power, the display screen shows the operating status, and the control buttons are used to adjust parameters.

[0014] The present invention also provides a microfluidic extraction method, which uses the microfluidic extraction system described above, and includes the following steps. S1: Prepare the sample to be tested; S2: Prepare the microfluidic chip, which is made of polymethyl methacrylate and whose internal channels are manufactured by laser processing; S3: The sample to be tested is added into the microfluidic chip through the injection port using a micro-injection pump or a manual injection device; S4: Connect the microfluidic chip to the rotary drive device and control the rotary drive device to rotate at a preset speed so that the sample to be tested and the vortex mixing zone generate vortices; S5: Adjust the rotation speed of the rotary drive device so that the sample to be tested is slowly centrifuged in the filtration and separation zone to initially separate the soil particles from the extract. S6: Adjust the rotation speed of the rotary drive device again so that the sample to be tested is centrifuged at high speed in the centrifugal enrichment zone to obtain a clear supernatant of heavy metal leaching solution. S7: The clarified supernatant of the heavy metal leachate is exported through the sample outlet and subjected to qualitative and quantitative analysis of heavy metals.

[0015] In some implementations, step S1 includes S101: Collect soil samples from the target area, remove impurities, air-dry or oven-dry, and then grind them to sieve to ensure uniform sample particle size; S102: Prepare a weak acid extract.

[0016] The present invention achieves the following technical effects compared to the prior art: The microfluidic chip provided by this invention significantly reduces the extraction time—which typically takes 16 hours or more using traditional methods (such as vortex mixing)—to less than 10 minutes through high-speed vortex mixing within the chip, resulting in a substantial increase in efficiency. It integrates multiple independent and time-consuming operations, such as vortexing, filtration, and centrifugation, into a single microfluidic chip, reducing sample transfer and intermediate steps and greatly improving the overall process efficiency. It eliminates the need for repeated transport and offers a high degree of automation. The automated execution of extraction, filtration, and centrifugation steps reduces manual intervention and operational complexity. Furthermore, compared to the bulky and immobile nature of traditional vortex mixers or ultrasonic devices, this invention, based on a microfluidic chip, results in a compact, lightweight system that is easy to carry and deploy in the field, providing significant convenience for field or mobile laboratories. Furthermore, the primary filtration is completed by trapping large soil particles through a filter membrane layer, and then the primary filtration extract is clarified a second time by high-speed centrifugal force to remove ultrafine suspended particles. The final extract has higher clarity and can be directly connected to electrochemical, spectroscopic and other detection methods, avoiding problems such as solid particles contaminating the detection electrode and detection baseline drift, thereby improving the sensitivity and accuracy of subsequent detection. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the microfluidic chip structure in some embodiments of the present invention; Figure 2 This is an exploded view of the microfluidic chip in some embodiments of the present invention; Figure 3 This is a flowchart illustrating the microfluidic extraction system in some embodiments of the present invention; Figure 4 This is an exploded view of the microfluidic extraction system structure in some embodiments of the present invention; Figure 5 This is a schematic diagram of the microfluidic extraction system structure in some embodiments of the present invention; Figure 6 This is a diagram of SWASV data from ultrasonic extraction in some embodiments of the present invention; Figure 7 This is a SWASV data graph for vortex and oscillation extraction in some embodiments of the present invention; Figure 8 This is a schematic diagram of the swinging and pushing / pulling extraction motion trajectories in some embodiments of the present invention; Figure 9This is a diagram showing SWASV data from swing and push-pull extraction in some embodiments of the present invention; Figure 10 This is a comparison diagram of the extraction effects of various methods in some embodiments of the present invention; Figure 11 This is a schematic diagram of the output voltage waveforms of the electrochemical workstation at various stages in some embodiments of the present invention; Figure 12 This is a diagram showing the optimized concentration of acetate buffer solution in some embodiments of the present invention; Figure 13 This is a diagram showing the vortex time optimization in some embodiments of the present invention; Figure 14 This is a diagram showing the optimized solid-liquid ratio in some embodiments of the present invention; Figure 15 This is an optimized diagram of vortex rotation speed in some embodiments of the present invention.

[0019] In the diagram: 1-Vortex mixing zone; 2-First filtration separation zone; 3-Second filtration separation zone; 4-Centrifugation enrichment zone; 5-Inlet; 6-Outlet; 7-Pressure balance port; 8-Positioning hole; 9-Upper sealing layer; 10-Middle sealing layer; 11-Lower sealing layer; 12-Main chamber layer; 13-Upper filter membrane layer; 14-Middle filter membrane layer; 15-Lower filter membrane layer; 16-Secondary chamber layer; 17-Base plate; 101-Microfluidic chip; 102-Vortex base; 103-Rotation drive device; 104-Main chassis; 105-Power module; 106-Motor driver. Detailed Implementation

[0020] 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.

[0021] The purpose of this invention is to provide a microfluidic chip, a microfluidic extraction system, and an extraction method to solve the problems existing in the prior art, thereby achieving higher extraction efficiency and a higher degree of automation.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1 like Figures 1-2As shown, the present invention provides a microfluidic chip 101, comprising a sealing layer, a main chamber layer 12, a filter membrane layer, a secondary chamber layer 16, and a base plate 17 connected sequentially from top to bottom. The sealing layer, main chamber layer 12, filter membrane layer, and secondary chamber layer 16 each have multiple processing spaces along the radial direction, and after being stacked, there are at least three processing spaces along the radial direction. From the inside out, these are a vortex mixing zone 1, a filtration separation zone, and a centrifugal enrichment zone 4. The solution capacity of the centrifugal enrichment zone 4 is 3.2 ml. An inlet 5 is provided near the center of the sealing layer, and an outlet 6 is provided near the edge. The sample to be tested can enter through the inlet 5 and flow into the vortex mixing zone 1, where it undergoes vortex extraction. After extraction, the sample to be tested can pass through the filter membrane layer and, under external force, return from the main chamber layer 12 to the secondary chamber layer 16, reaching the filtration separation zone and finally the centrifugal enrichment zone 4, where it is removed through the outlet 6. By utilizing high-speed vortex mixing within the microfluidic chip 101, the extraction time required by traditional methods (such as vortex mixing) of 16 hours or even longer is significantly reduced to less than 10 minutes, resulting in a substantial increase in efficiency. Multiple independent and time-consuming operations, such as vortexing, filtration, and centrifugation, are integrated into a single microfluidic chip, reducing sample transfer and intermediate steps, greatly improving the overall process efficiency. No back-and-forth transport is required, resulting in a high degree of automation. The automated execution of extraction, filtration, and centrifugation steps reduces manual intervention and operational complexity. Furthermore, compared to the disadvantages of traditional vortex mixers or ultrasonic devices being bulky and difficult to move, this embodiment, based on the microfluidic chip 101, features a compact and lightweight system that is easy to carry and deploy in the field, providing great convenience for field or mobile laboratories. Furthermore, the primary filtration is completed by trapping large soil particles through a filter membrane layer, and then the primary filtration extract is clarified a second time by high-speed centrifugal force to remove ultrafine suspended particles. The final extract has higher clarity and can be directly connected to electrochemical, spectroscopic and other detection methods, avoiding problems such as solid particles contaminating the detection electrode and detection baseline drift, thereby improving the sensitivity and accuracy of subsequent detection.

[0024] In some embodiments, the sealing layer, main chamber layer 12, filter membrane layer, and secondary chamber layer 16 contain multiple independent processing units along the circumference. Each processing unit includes a vortex mixing zone 1, a filtration separation zone, a centrifugal enrichment zone 4, a sample inlet 5, and a sample outlet 6. Preferably, four processing units are provided. The microfluidic chip 101 is disk-shaped, and the four processing units are located in four quadrants, enabling simultaneous processing of multiple soil samples. The four independent processing units arranged in a four-quadrant configuration can simultaneously complete the entire pretreatment process of vortex extraction, filtration separation, and centrifugal enrichment on the same chip, and can simultaneously process four soil samples with a single startup. Each processing unit is equipped with an independent sample inlet 5, vortex mixing zone 1, filtration separation zone, centrifugation enrichment zone 4, and sample outlet 6. The chambers and flow channels between units are completely independent, with no shared structures or connecting flow paths. Even if the heavy metal concentrations of soil samples from different units vary greatly (such as samples from heavily polluted sites and clean control sites), there will be no sample cross-contamination or contamination issues. This avoids the contamination risks associated with shared flow channels in traditional multi-channel chips, ensuring the authenticity and accuracy of the test results for each sample. The four processing units are integrated on the same disc chip and driven synchronously by the same motor. Key parameters such as vortex rotation speed, vortex time, centrifugal force, and extraction environment are completely uniform for all samples, eliminating systematic errors caused by different equipment and different batches in traditional methods. The relative standard deviation (RSD) of parallel sample test results is significantly reduced, and data repeatability and reliability are greatly improved. With just one clamping, one injection, and one start-up, the entire pretreatment process for four samples can be completed simultaneously, reducing the number of repetitive manual operations, lowering the labor intensity of operators, and reducing random errors caused by manual operation at the source. Even non-professionals can complete the standardized pretreatment of large batches of samples.

[0025] As a preferred embodiment, each processing unit is provided with a pressure balance port 7. Each processing unit has an independent balance port, which can discharge the air in the chamber in real time during sample injection and replenish the pressure simultaneously during sample discharge to eliminate air resistance.

[0026] In some embodiments, the sealing layer includes a sealing upper layer (1mm thick) 9, a sealing middle layer (2mm thick) 10, and a sealing lower layer (1mm thick) 11, which are sequentially bonded together from top to bottom. All three layers are made of rubber. Since all three layers are made of rubber, their coefficients of thermal expansion and elastic moduli are completely identical, preventing issues such as warping, separation, and gaps caused by temperature changes and uneven stress in plastic-rubber hybrid structures. The flexible bonding of the three layers completely fills the microscopic gaps between the chip layers, achieving a 360° full-coverage seal for leak-prone points such as the sample inlet 5, flow channel interface, and chamber edges. Even under the strong radial pressure and turbulent impact of high-speed centrifugation at 2500rpm and 8000rpm, zero leakage can be achieved throughout the entire process. From sample injection, vortex mixing, low-speed filtration to high-speed centrifugation, the internal fluid pressure is dynamically changing. The superimposed elasticity of the three-layer rubber structure has greater deformation and better resilience than that of a single-layer rubber. It can adaptively expand and contract with changes in internal pressure, withstand the instantaneous impact of vortex turbulence, and also withstand the continuous high pressure of centrifugal process. It will not have problems such as high pressure bursting or low pressure rebound failure, and maintains stable sealing of the interface throughout the process, ensuring the continuous operation of the pretreatment process.

[0027] In some embodiments, the filter membrane layer includes an upper filter membrane layer 13, a middle filter membrane layer 14, and a lower filter membrane layer 15, which are sequentially bonded together from top to bottom. The upper filter membrane layer 13 and the lower filter membrane layer 15 can support the middle filter membrane layer 14. The upper filter membrane layer 13 and the lower filter membrane layer form a symmetrical rigid clamping structure, which firmly fixes the functional middle filter membrane layer 14 in the middle, completely restricting its deformation space. This avoids the problems of bulging, denting, tearing, and edge curling that occur in unsupported / single-sided supported filter membranes under the strong radial pressure of 2500rpm vortex turbulence impact and 8000rpm high-speed centrifugation. At the same time, it avoids the problems of liquid flow short circuit (liquid flowing out from the edge gap of the filter membrane without filtration) and seal failure leakage caused by filter membrane displacement. Even under repeated variable speed centrifugation and bidirectional liquid flow impact, the filter membrane shape remains stable, ensuring the reliability of the chip's entire process operation.

[0028] In some embodiments, the filtration separation zone includes a first filtration separation zone 2 and a second filtration separation zone 3 in the radial direction. Both the first filtration separation zone 2 and the second filtration separation zone 3 are embedded with a secondary hydrophilic polytetrafluoroethylene (PTFE) filter membrane. The dual filtration zones connected in series from the inside to the outside in the radial direction form a two-stage gradient interception system of coarse filtration and fine filtration. The inner first filtration separation zone 2 is responsible for primary coarse filtration, which uses the secondary filter membrane to intercept large-particle aggregates of soil, sand, gravel, plant residues and other large-particle impurities, avoiding damage and blockage caused by large particles directly impacting the fine filter membrane. The outer second filtration separation zone 3 is responsible for deep fine filtration, which uses the secondary filter membrane to further remove ultrafine suspended particles, humic colloids, clay particles and other small impurities that are easy to interfere with detection in the leachate after primary filtration.

[0029] Example 2 like Figures 3-5 As shown, this embodiment also provides a microfluidic extraction system, including a rotary drive device 103, a control system, and the microfluidic chip 101 in Embodiment 1. The output end of the rotary drive device 103 can be connected and fixed to the microfluidic chip 101. The rotary drive device 103 is used to drive the microfluidic chip 101 to perform vortex extraction or centrifugal separation. The control system is electrically connected to the rotary drive device 103. Traditional pretreatment of weakly acidic soluble heavy metals in soil requires multiple independent devices such as vortex mixers, centrifuges, and filters, along with multiple manual sample transfers. The process is cumbersome, time-consuming, and carries a high risk of cross-contamination. However, this microfluidic extraction system can simultaneously achieve the entire process of vortex extraction, low-speed filtration separation, and high-speed centrifugal enrichment within the chip using only one rotary drive device 103. The sample can be injected and clamped once, and all pretreatment steps can be completed within a single chip. This eliminates sample loss and cross-contamination risks caused by switching multiple devices and multiple manual operations, compressing the original pretreatment process of several hours to less than 10 minutes, improving efficiency by more than 100 times.

[0030] In some embodiments, the microfluidic extraction system further includes a vortex base 102, a centrifuge base, and multiple positioning holes 8. The positioning holes 8 are distributed along the diameter of the microfluidic chip 101, with one positioning hole 8 located at the center. Positioning posts are provided on both the vortex base 102 and the centrifuge base, and these posts can be inserted into the positioning holes 8. Both the vortex base 102 and the centrifuge base can be fixedly connected to the output end of the rotary drive device 103. Both the vortex base 102 and the centrifuge base can be fixedly connected to the output end of the same rotary drive device 103. Only the base needs to be replaced; the entire pretreatment process—vortex extraction, low-speed filtration, and high-speed centrifugation—can be completed using the same drive system, eliminating the need for two separate drive devices for vortex and centrifugation. The positioning posts and positioning holes 8 adopt a tool-less plug-in design; simply align the positioning hole 8 of the chip with the positioning post on the base and insert it, making the operation simple and quick. The central arrangement features multiple positioning holes distributed along the diameter, ensuring that the fixing force is evenly distributed along the diameter after the chip is clamped, preventing issues such as unilateral force or clamping misalignment. This allows the chip's three-layer all-rubber sealing layer to be evenly pressurized, ensuring a tight seal at the sealing interface throughout the process. Even under conditions of high-speed rotation and internal pressure fluctuations, there will be no issues such as local sealing failure or sample leakage.

[0031] In some embodiments, the microfluidic extraction system further includes a power module 105, a display screen, and multiple control buttons. The power module 105 provides power, the display screen shows the operating status, and the control buttons are used to adjust parameters. The power module 105 provides the system with completely independent power supply capabilities. It can have a built-in battery pack, eliminating the need for mains power or external host computer power. Even in passive environments such as remote farmland, polluted mining areas without power, or emergency monitoring sites, it can complete the entire pretreatment process normally. The display screen can display the system's full-dimensional operating information in real time and intuitively, including the current operating stage (vortex extraction / filtration separation / centrifugal enrichment), real-time rotation speed, remaining operating time, processed batches, remaining battery power, parameter settings, and other core information. Multiple control buttons enable on-site visual control of all parameters. In most cases, operators can adjust core pretreatment parameters such as vortex rotation speed / time, filtration speed / time, and centrifugation speed / time on-site without connecting to a computer or performing professional programming. This allows for rapid optimization of extraction conditions for different types of soil samples (sandy soil, clay soil, high organic matter soil, and heavily contaminated soil) without having to return to the laboratory to adjust the program. It is suitable for flexible on-site operations such as emergency monitoring and multi-point screening in complex sites.

[0032] In a preferred embodiment, the rotary drive 103 is a high-precision brushless DC motor or stepper motor, and is equipped with a main unit housing 104. The main unit housing 104 is cubic in shape, made of engineering plastic, and provides motor mounting slots and space for other components. It houses the main control chip circuitry, buttons, and a 1.8-inch display screen. The motor is installed internally, and external openings and interfaces are provided for power cable entry and connection to the motor driver 106. The top opening allows the motor shaft and vortex / centrifugal base to extend for mounting the microfluidic chip 101. The main unit housing 104 serves as the outer shell of the entire system, protecting the internal precision components from external environmental influences; it provides a stable mounting platform and integrates other electronic components into a compact and portable unit. The motor is also connected to the motor driver 106, which is an independent electronic module containing power amplifier circuitry and control logic for precisely controlling the motor's speed, direction, and start / stop. The motor driver 106 is connected to the electrical leads of the motor via a cable. The cable is led out from inside the main unit 104 and connected to the power module 105 to obtain working power. At the same time, it receives control signals from the control system and converts low-power control signals into high-power drive signals to precisely drive the motor to run according to preset parameters (such as vortex rotation speed and centrifugal speed).

[0033] Example 3 like Figure 1-15 As shown, this embodiment also provides a microfluidic extraction method, which uses the microfluidic extraction system in Embodiment 2, and includes the following steps. S1: Prepare the sample to be tested; S2: Prepare a microfluidic chip 101. The microfluidic chip 101 is made of polymethyl methacrylate and is generally flat and cylindrical. The internal flow channels are manufactured by laser processing, preferably using a 10640nm laser. S3: The sample to be tested is added into the microfluidic chip 101 through the injection port 5 using a micro-injection pump or a manual injection device. S4: Connect the microfluidic chip 101 to the rotary drive device 103 and control the rotary drive device 103 to rotate at a preset speed (2500 rpm) so that the sample to be tested and the vortex mixing zone 1 generate vortices. S5: Adjust the rotation speed (1000 rpm) of the rotary drive device 103 so that the sample to be tested is slowly centrifuged in the filtration separation zone to initially separate the soil particles from the extract. S6: Readjust the rotation speed of the rotary drive device 103 (8000 rpm) to centrifuge the sample to be tested at high speed in the centrifugation enrichment zone 4 to obtain a clear supernatant of heavy metal leaching solution. S7: The clarified supernatant of the heavy metal leachate is exported through the sample outlet 6 and subjected to qualitative and quantitative analysis of heavy metals.

[0034] After a single sample injection, the entire pretreatment process—including vortex extraction, filtration, and centrifugal enrichment—is completed within a single, enclosed microfluidic chip 101. This eliminates the need for switching between multiple devices such as vortex mixers, centrifuges, and filters required in traditional methods, as well as the need for multiple manual sample transfers. The pretreatment cycle, which typically takes over 16 hours using the traditional reverse oscillation method, is significantly reduced to less than 10 minutes. Polymethyl methacrylate (PMMA) does not leach impurities that interfere with heavy metal detection, exhibits strong chemical stability, and possesses excellent machinability, meeting the mechanical requirements of high-speed rotation. 10640nm laser processing enables micron-level precision in channel and chamber shaping, matching the flow field design of vortex, filtration, and centrifugation. The processing is simple, yields high quality, eliminates the need for expensive photolithography microfabrication equipment, and the chip can be used once, resulting in extremely low cost and suitability for large-scale mass production and grassroots deployment.

[0035] In some embodiments, step S1 includes S101: Collect soil samples from the target area, remove impurities, air-dry or oven-dry, and then grind them to pass through a sieve (50 mesh sieve) to ensure uniform sample particle size; S102: Prepare a weak acid extract, preferably a 0.6M acetic acid / sodium acetate solution (pH 5.0).

[0036] After grinding, the sample is passed through a 50-mesh sieve (corresponding to a particle size of approximately 300 μm), which allows for strict control of the maximum particle size of the soil sample. This matches the microchannel size of the microfluidic chip 101 and the pore size of the secondary PTFE filter membrane, preventing blockage of the chip channels and filter membrane due to excessively large particles, and avoiding punctures and scratches to the chamber by sharp sand and gravel particles. This avoids the problems of chip failure and sample waste caused by traditional non-standardized pretreatment, ensuring stable operation of the entire rapid extraction process within 10 minutes. This system is a standard extraction system for weakly acid-soluble heavy metals in the BCR continuous extraction method. It can specifically extract water-soluble, ion-exchangeable, and carbonate-bound heavy metals (i.e., bioavailable forms that are toxic to crops and organisms) from soil. It does not extract stable and non-toxic heavy metals such as iron-manganese oxide-bound or residual forms. This solves the problems of traditional strong acid digestion methods where soil samples exceed the permitted limits but rice samples do not, and the test results do not match the actual ecological risks. The test results can be directly used for soil pollution risk assessment.

[0037] Example 4 This embodiment provides the complete workflow of a microfluidic extraction system: 1. Start and System Initialization: 1.1 Turn on the power: The operator turns on the system power.

[0038] 1.2 Screen loading: The system display screen begins loading the startup interface and programs.

[0039] 1.3 Low Battery Warning: The system performs a self-check to determine if the current battery level is sufficient. If the battery is low, the operator is prompted to charge or replace the battery; if the battery level is normal, proceed to the next step.

[0040] 1.4 System Initialization: The system performs self-checks, parameter loading, and other preparatory work to ensure that all functional modules are in normal standby mode.

[0041] 2. Sample loading and vortex immersion preparation: 2.1 Prompt to check if the tray is in place: The system prompts the operator to check whether the microfluidic extraction chip (or sample tray) has been correctly placed in the rotating platform of the drive and control module.

[0042] 2.2 Vortex: The system awaits operator confirmation that the sample tray has been placed and is ready for vortex extraction. This step can directly connect to the other three operating states.

[0043] 2.3 Vortex Direction Setting: The operator sets the vortex rotation direction through the user interface.

[0044] 2.4 Vortex Duration Setting: The operator sets the duration of vortex extraction.

[0045] 2.5 Vortex speed setting: The operator sets the rotation speed of the vortex extraction.

[0046] 2.6 Parameter Confirmation: The system prompts the operator to confirm whether the currently set vortex direction, duration, and speed parameters are correct.

[0047] 2.7 System Startup: After confirming that everything is correct, the microcontroller unit (MCU) of the drive and control module issues a command to start the precision micro motor.

[0048] 2.8 Screen Display of Vortex Extraction Completion: The motor drives the microfluidic extraction chip to rotate at high speed, achieving vigorous mixing of the sample and the extraction solution in the vortex mixing chamber inside the chip, thus completing the extraction of weakly acid-soluble heavy metals. After the preset time has elapsed, the system display screen indicates that the vortex extraction is complete.

[0049] 3. Filtration and separation: 3.1 Low-speed filtration: After the vortex cycle is complete, the system automatically or under operator command performs filtration at a low speed, initially separating solids and liquids through the filtration separation zone within the chip. Alternatively, it can operate in direct centrifugation mode.

[0050] 3.2 Filtration speed setting: The operator can set the rotation speed of the filtration stage.

[0051] 3.3 Filtering duration setting: The operator sets the duration of the filter.

[0052] 3.4 Filtering direction setting: The operator sets the rotation direction of the filtering stage.

[0053] 3.5 Confirm Parameters: The system prompts the operator to confirm the filtering parameters.

[0054] 3.6 System Startup: After confirming that everything is correct, restart the motor to perform filtering.

[0055] 3.7 Screen Display Filtering Completed: After the filtering operation is completed, the system display screen will indicate that the filtering is complete.

[0056] 4. High-speed centrifugation: 4.1 High-speed centrifugation: After filtration, the system automatically or under operator instruction performs high-speed centrifugation to further clarify the extract. Alternatively, the process can be completed directly.

[0057] 4.2 Centrifugation direction setting: The operator sets the rotation direction during the centrifugation stage.

[0058] 4.3 Centrifugation duration setting: The operator sets the duration of centrifugation.

[0059] 4.4 Centrifugation speed setting: The operator sets the centrifugation speed.

[0060] 4.5 Confirm Parameters: The system prompts the operator to confirm the centrifugation parameters.

[0061] 4.6 System Startup: After confirming that everything is correct, restart the motor to perform high-speed centrifugation.

[0062] 4.7 Centrifugation Completed on Screen: After the centrifugation operation is completed, the system display screen will indicate that centrifugation is complete. At this time, the clarified heavy metal extract is ready to be exported through the sample outlet channel for detection by various methods.

[0063] 5. Follow-up processing and termination: 5.1 Should the next sample be tested? The system asks the operator whether they need to continue testing the next sample.

[0064] Yes: If you select "Yes", the system will return to "Screen loading" and prepare to process the next sample.

[0065] No: If "No" is selected, the system will enter the end state.

[0066] 5.2 Replace the sample tray module: Before the next sample test, the system prompts the operator to replace the processed sample tray and load the new sample tray to be tested.

[0067] The core advantage of the entire process lies in the automation and integration of complex operations such as vortex mixing, low-speed filtration and high-speed centrifugation inside the microfluidic extraction chip through precise control of the drive and control modules. This simplifies the traditional time-consuming and complex multi-step pretreatment process into a single process that is guided by the system and completed quickly, greatly improving efficiency and convenience.

[0068] Example 5 This embodiment explains the reason for using vortex mixing in the extraction step and provides a comparison of various methods.

[0069] Ultrasonic extraction method The leaching curves of heavy metals in contaminated soil samples extracted by ultrasonic methods are shown below. Figure 6 As shown in the left figure, signals of both heavy metals Cd and Cu can be detected simultaneously in the leachate obtained by the ultrasonic method, but the baseline exhibits some fluctuations, which may be due to the interference of the complex soil matrix on the electrode interface. However, with the addition of Bi... 3+ After the solution was transferred to the leaching solution, the signals of heavy metals Zn, Cd, Pb, and Cu could all be detected simultaneously, with a significant enhancement in the main peak current, a sharper and more symmetrical peak shape, a reduced full width at half maximum (FWHM), and a more stable background current, resulting in a significantly improved signal-to-noise ratio. This is because Bi... 3+ During the electrodeposition stage, a bismuth film can be formed in situ on the surface of the working electrode, a behavior similar to that of a traditional mercury film electrode. The formation of the bismuth film enhances the deposition efficiency of heavy metals by increasing the hydrogen evolution potential and decreasing the surface energy, meaning the amount of heavy metals deposited on the electrode per unit time increases. Furthermore, during the dissolution stage, heavy metals are simultaneously oxidized from the Cd-Bi and Pb-Bi alloys, resulting in a more concentrated dissolution process, narrower peaks for heavy metals, and faster electron transfer kinetics. Figure 6 (Right figure) shows the peak height and peak area of ​​various heavy metals. Overall, Bi 3+ The introduction of this significantly improved the enrichment and leaching efficiency of heavy metals, effectively alleviated the passivation effect of complex matrix in soil leachate on the electrode surface, and made the detection system exhibit higher sensitivity.

[0070] The presence of five heavy metal ions in the SWASV signal indicates that ultrasonic leaching can extract these five heavy metals from soil. This is because ultrasound can generate cavitation in liquids, causing countless tiny bubbles to form, grow, and burst. This process is accompanied by localized high temperature, high pressure, and shock waves, which can break up soil particle aggregates, increase the contact area between the soil and the leachate, and promote the dissolution and diffusion of heavy metals in the soil. Based on the ultrasonic cavitation effect, ultrasonic leaching can improve the leaching effect of some insoluble or tightly bound heavy metals. Furthermore, ultrasonic methods have advantages such as simple operation and short processing time, leading to their rapid development and application in recent years. However, ultrasonic leaching is often closer to "enhanced extraction." During the ultrasonic leaching of heavy metals in soil, the localized high temperature, high pressure, and microjets generated by ultrasonic cavitation can damage the soil microstructure, potentially releasing metals that are not originally bioavailable. Although ultrasound is inaudible to the human ear, the secondary harmonics and mechanical vibration noise generated by the ultrasonic generator can reach over 80 dB, which may damage the operator's hearing or cause nerve fatigue leading to improper operation. Therefore, there is an urgent need for an efficient and healthy soil extraction method to achieve rapid preparation of soil extract.

[0071] Vortex and oscillation extraction methods Vortexing and oscillation are two commonly used mechanical mixing methods in the laboratory. They apply mechanical force to the sample through different motion patterns, thereby promoting the extraction of heavy metals. The SWASV curves and extraction peak heights and areas under vortex and oscillation extraction treatments are observed, such as... Figure 7 As shown, both methods can extract signals of the four heavy metal ions, and the extraction effects of the two methods are similar. However, there are two differences. First, the peak area of ​​Cd obtained by the oscillating extraction method is larger, because its peak width is larger when the peak height is constant. Second, the relative standard deviation of the extract signal obtained by the oscillating extraction method is larger at the peak value, indicating that the solution system is less stable, which is also one of the reasons for its larger peak width.

[0072] Although both involve mechanical stirring, their mechanisms of action and extraction efficiencies differ. The shaking extraction method generates macroscopic convection and shear forces in the solution through the overall movement of the container, promoting thorough contact between the liquid and solid particles. Shaking extraction helps reduce diffusion distance, accelerating the dissolution of soluble components and desorption from the solid particle surface. The vortex extraction method utilizes a motor and eccentric shaft to create a vigorous vortex around the center point of high-speed rotation of the sample tube. This high-speed rotation generates very strong shear forces and localized turbulence, rapidly mixing the sample and promoting mass transfer. The mixing intensity in localized areas is generally stronger during vortex extraction than during shaking. However, the data shows that the two methods yield similar extraction results, which is related to the parameters used in shaking and vortexing. Currently, the shaking frequency is relatively high (motor rotation frequency of 6000 rpm). If the vibration frequency is reduced, the soil in the solution does not experience sufficient force and remains at the bottom of the container, failing to achieve uniform contact with the buffer solution. The vortex frequency is lower, only 2000 rpm; further increasing the vortex frequency may result in better vortex extraction. It's worth noting that in oscillating extraction, an eccentric iron block is attached to the outside of the motor. The continuous eccentric force of the eccentric iron block causes the module to oscillate at high frequency. This oscillation of the eccentric iron block causes the entire device to oscillate. On the one hand, the entire device needs to be fixed with heavy objects; on the other hand, the continuous oscillation generates high-frequency noise. In contrast, the vortex extraction method is very quiet and has minimal impact on the hearing health of operators.

[0073] Swing and push-pull extraction methods The two mechanical extraction methods, rocking and pushing / pulling, simulate physical disturbances under environmental conditions. For example... Figure 8 As shown, the rocking motion primarily promotes mixing of solution and solid particles at a macroscopic level by changing the direction of the liquid-solid interface and applying a periodic gravitational component. While the shear force generated is relatively weak, its advantage lies in achieving gentle and uniform mixing throughout the entire sample container, avoiding the localized concentration problems that can occur with vortices. Furthermore, the rocking motion focuses on promoting the slow release of heavy metals through prolonged interface refresh and convection. The key to the push-pull motion lies in its directional reciprocating shearing and compression effects. During the push-pull process, localized stress concentrations may occur in certain areas, which helps to break down aggregates or desorb them.

[0074] Observe the SWASV curves and extraction peak heights and areas under the swing and push-pull extraction treatments, such as Figure 9As shown, signals for all four heavy metals were detected under the swing extraction method; however, the signals for Zn, Cd, Pb, and Cu were all at low levels. This may be because the swing motion generates weak mechanical disturbance, making it difficult to effectively break up soil aggregates and provide sufficient energy to overcome the binding energy between heavy metals and soil particles. This indirectly reflects that heavy metals need to overcome certain energy barriers and diffusion resistance to desorb from the surface of soil particles and diffuse into the solution. Similar to the swing extraction method, although the Zn and Cd signals under the push-pull extraction method were slightly higher than those under the swing method, the overall signal strength was weaker. This indicates that the directional shear force generated by the push-pull method is more effective in promoting the release of heavy metals than simple swinging, but its overall effect is still relatively low. It is worth noting that the motor speed in both the swing and push-pull motion experiments was lower than that of other methods, which may be one of the main reasons for the poor extraction effect. However, at the currently used speed, the detection equipment already exhibits significant oscillations and mechanical noise, which limits the application and promotion of both methods in soil pretreatment.

[0075] Comparison of extraction effects of various methods A comprehensive comparison of the five extraction methods—ultrasound, vibration, vortex, rocking, and push-pull—shows that... Figure 10 As shown in the left figure, the influence of different physical forces on the leaching effect of heavy metals in soil can be understood more comprehensively. Overall, the dissolution currents of all four heavy metal ions were detected in the leachates obtained from the five leaching methods, indicating that all four heavy metal ions were leached from the soil samples. In wet sample preparation, the added content of heavy metal Cd was twice that of Zn, Pb, and Cu. However, the peak area and peak height signal of heavy metal Cd were not twice that of Zn, Pb, and Cu, but rather much stronger. This indicates that a series of reactions occurred between the heavy metals and the soil during wet sample preparation. Zn and Cd typically have high bioavailability or relatively unstable bound forms in soil, which are more easily released by physical disturbances. Pb often forms stable compounds with phosphates and iron / manganese oxides / hydroxides in the soil, or is strongly adsorbed.

[0076] like Figure 10As shown in the right figure, the extraction efficiency of these five methods can be ranked (from high to low): ultrasound ≈ vortex > oscillation > push-pull > rocking. Relying on the high-energy microjets and shock waves generated by cavitation, ultrasonic extraction achieves the best extraction effect. Vortex extraction, through eddies, local turbulence, and strong shear force, can also peel heavy metals from the surface of soil particles and disperse them into the solution, with an extraction effect similar to that of the ultrasonic method. This indicates that strong hydrodynamic shear force is effective in extracting heavy metals from soil; further increasing the vortex speed or extending the vortex time may further improve the soil extraction effect. Oscillating extraction mainly relies on macroscopic convection and shear force; although its energy density and local intensity are slightly weaker, the extraction effect is still considerable. However, due to the need for a high-strength fixing scheme and the influence of high-frequency noise, it is difficult to gain favor in the development of smart agriculture. The oscillating and push-pull extraction method simulates the physical operation of mixing liquids by humans, continuously and directionally shaking the container to induce reciprocating shearing and compression in the soil. This promotes inter-particle friction and desorption of heavy metals to some extent, but the method is inefficient and the extraction effect is not good. Therefore, the vortex extraction method will be further studied and combined with microfluidic-like devices for rapid soil pretreatment, promoting the rapid detection of key indicators in soil, such as heavy metals, and driving the development of smart agriculture.

[0077] Example 6 This embodiment provides optimization of multiple parameters in vortex mixing operations. By systematically optimizing key parameters such as solid-liquid ratio, vortex time, vortex rotation speed, and extract concentration, this invention can achieve more efficient and complete extraction of target heavy metals, ensuring the accuracy and representativeness of subsequent analytical results.

[0078] Detection techniques and methods This patent is based on the optimization results of various parameters analyzed by electrochemical square-wave pulsed anodic stripping voltammetry (SWASV). According to the order of ion redox activity, SWASV can achieve qualitative and quantitative measurement of heavy metals (HMs). SWASV measurement mainly includes two processes: deposition and dissolution. In the deposition stage, by applying a constant negative potential, trace heavy metal ions in the solution undergo reduction reactions on the working electrode surface and are pre-enriched in the form of elemental metals. This process is essentially a coupling of the Faraday process and the mass transfer process; therefore, the deposition potential, deposition time, and solution stirring speed directly determine the enrichment amount of the target metal on the electrode surface. Subsequently, in the settling stage, the solution is stopped from stirring to eliminate convection interference and ensure that the diffusion layer on the electrode surface tends to stabilize. Finally, in the dissolution stage, a square-wave pulse voltage scanning in the positive direction is applied, causing the elemental metals deposited on the electrode surface to be re-oxidized into ions and dissolved back into the solution. The resulting oxidation peak current is the quantitative analytical signal.

[0079] The output voltage waveform of the electrochemical workstation is as follows: Figure 11 As shown. The specific electrochemical detection was as follows: Pre-enrichment deposition was performed for 180 s at a constant potential of -1.2 V (vs. Ag / AgCl) under constant magnetic stirring at 300 r / min. After deposition, the system was allowed to stand for 10 s to balance the concentration gradient on the electrode surface. Subsequently, anodic scanning was performed in SWASV mode within a potential window from -1.2 V to 0.2 V, with a dissolution voltage pulse amplitude ΔE of 25 mV, a square wave frequency f of 25 Hz, and a potential increment ΔEstep of 5 mV. Furthermore, after each measurement, the electrode was held at a strong oxidation potential of 0.4 V for 120 s to completely oxidize and remove any residual metal deposits on the electrode surface, restoring the electrode to its initial state for the next measurement.

[0080] Figure 11 and Figure 12 Together, they revealed the effects of different buffer concentrations on the extraction efficiency of five heavy metals: zinc (Zn), cadmium (Cd), lead (Pb), bismuth (Bi), and copper (Cu).

[0081] Overview and Methodology Confirmation: Figure 12 (Top Left): Current / Voltage Curves: This graph shows the square wave stripping voltammetry (SWV) curves of mixed heavy metals under different buffer concentrations (0.2M, 0.4M, 0.6M, 0.8M, 1.0M). Each metal exhibits an oxidation peak at a specific potential, and the peak height and peak area represent the concentration of the corresponding heavy metal in the extract. We can clearly see the changes in peak shape and peak height at different concentrations.

[0082] Figure 12 (The remaining five bar charts): These correspond to five metal ions—Zn, Cd, Pb, Bi, and Cu—and detail the trends in peak height (µA) and peak area (µA·V) of their dissolution peaks at different buffer concentrations. Error bars are included to indicate the reproducibility of the experiments. Peak height usually directly reflects the metal concentration, while peak area may better reflect the total amount dissolved.

[0083] This invention, through systematic optimization of different buffer concentrations, discovered that the optimal extraction concentrations for different heavy metals vary. For example, zinc and bismuth exhibit the highest extraction efficiency in 0.4M buffer; cadmium shows the best results at 0.6M; while lead and copper show better extraction effects in high-concentration (e.g., 1.0M) buffers.

[0084] Considering that multiple heavy metals often need to be detected simultaneously in practical applications, this invention allows for the selection of an optimized buffer concentration based on actual needs. For example, if the focus is on Zn and Bi, 0.4M is preferred; if the focus is on Cd, 0.6M is preferred; and if Pb and Cu need to be considered simultaneously, 1.0M is preferred. In some embodiments, for balance considerations, the buffer concentration can be preferably between 0.4M and 0.6M, for example, 0.5M, to achieve a better overall extraction effect among most heavy metals.

[0085] Vortex time optimization (e.g.) Figure 13 (As shown) To determine the optimal vortex extraction time in the microfluidic chip 101 extraction system of this invention, in order to maximize the extraction efficiency of heavy metals and achieve rapid analysis, this study investigated the effects of different vortex times (5 min, 10 min, 15 min, 20 min, and 25 min) on the extraction efficiency of various typical heavy metals. The experiments were conducted using a 0.2 M acetate buffer solution at a constant vortex speed of 2000 rpm. The content of heavy metals in the extract was determined by electrochemical square wave stripping voltammetry (SWV), with peak height and peak area used as evaluation indicators.

[0086] The microfluidic vortex leaching method of this invention achieves extremely rapid heavy metal leaching rates. Within just 5 to 10 minutes, the leaching efficiency of most heavy metals (such as Zn, Pb, Bi, and Cu) reaches a high level, even approaching or reaching its maximum. For cadmium, the optimal leaching time is slightly longer, approximately 15 minutes. Considering that practical applications often require the simultaneous detection of multiple heavy metals and a balance between leaching efficiency and detection speed, the preferred vortex leaching time of this invention is 10 minutes. At this time point, zinc, lead, bismuth, and copper have achieved good leaching results, while cadmium also shows a significant improvement (though not optimal, it is close). Compared to traditional methods that involve reverse oscillation leaching for several hours (e.g., 16 hours), this invention drastically reduces the pretreatment time to only 10 minutes, increasing efficiency by hundreds of times, fully demonstrating its technical advantage of "rapid leaching." In specific application scenarios where extremely high cadmium leaching efficiency is required, the leaching time can be appropriately extended to 15 minutes. However, for routine multi-element rapid detection, 10 minutes is sufficient to provide satisfactory overall performance.

[0087] Solid-liquid ratio optimization (e.g.) Figure 14 (As shown) To optimize the ratio of soil sample to leachate in the microfluidic chip 101 extraction system of this invention, and to maximize sample and reagent savings while ensuring high extraction efficiency, this study investigated the effects of different solid-liquid ratios (1:80, 1:40, 1:20, 1:10, 1:5) on the extraction efficiency of various typical heavy metals. The experiments were conducted at a buffer concentration of 0.2 M, vortexing time of 10 minutes, and a vortex speed of 2000 rpm. The heavy metal content in the leachate was determined by electrochemical square wave stripping voltammetry (SWV), with peak height and peak area used as evaluation indicators.

[0088] For most heavy metals (Zn, Cd, Cu, Pb), a higher solid-liquid ratio (i.e., a relatively larger amount of leachate) is beneficial for the thorough extraction of heavy metals. At a solid-liquid ratio of 1:40, zinc, cadmium, and copper exhibit the best or near-optimal extraction effect. Lead is slightly better at 1:80, but maintains a good level at 1:40. Bismuth also performs well at 1:40. Considering the characteristics of microfluidic systems and the need to balance the extraction efficiency of multiple heavy metals, while also taking into account reagent consumption and waste liquid generation, the preferred solid-liquid ratio of this invention is 1:40. At this solid-liquid ratio, the extraction efficiency of most heavy metals reaches the optimal or near-optimal level, while saving half the amount of leachate compared to 1:80. When the solid-liquid ratio is lower than 1:20 (e.g., 1:10 or 1:5), the extraction efficiency of all heavy metals decreases significantly; therefore, excessively low solid-liquid ratios should be avoided in practical applications.

[0089] Vortex rotation speed optimization (e.g.) Figure 15 (As shown) To determine the optimal vortex speed in the microfluidic chip 101 extraction system of this invention to maximize extraction efficiency and ensure thorough mixing of the sample and the extract, this study investigated the effects of different vortex speeds (500 rpm, 1000 rpm, 1500 rpm, 2000 rpm, and 2500 rpm) on the extraction efficiency of various typical heavy metals. The experiments were conducted with a buffer concentration of 0.2 M, vortexing time of 10 minutes, and a solid-liquid ratio of 1:40. The heavy metal content in the extract was determined by electrochemical square wave stripping voltammetry (SWV), with peak height and peak area used as evaluation indicators.

[0090] Overall, increasing the vortex rotation speed significantly improves the leaching efficiency of heavy metals, demonstrating the crucial role of vortex mixing in this invention. The optimal vortex rotation speed varies among different heavy metals: Zn performs best at 1000 rpm, Pb and Cu at 1500 rpm, and Cd and Bi at 2000 rpm. Considering the need for simultaneous detection of multiple heavy metals and balancing the leaching efficiency of each element in practical applications, the preferred vortex rotation speed in this invention is between 1500 rpm and 2000 rpm. For example, choosing 1500 rpm can provide good leaching efficiency for Cd and Bi while maintaining optimal performance for Zn, Pb, and Cu. If Cd and Bi are the primary targets, the rotation speed can be optimized to 2000 rpm. Rotations below 1000 rpm (e.g., 500 rpm) are ineffective for most heavy metals and should be avoided. For some heavy metals (e.g., Cu), the leaching efficiency decreases at excessively high rotation speeds, which may be related to excessive vortex shear force leading to uneven sample dispersion or affecting the stability of the leachate. Therefore, higher rotational speed is not always better. Specific examples have been used in this invention to illustrate its principles and implementation methods. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of this invention; furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A microfluidic chip, characterized in that: The system comprises, from top to bottom, a sealing layer, a main chamber layer, a filter membrane layer, a secondary chamber layer, and a base plate, all connected in sequence. Each of the sealing layer, the main chamber layer, the filter membrane layer, and the secondary chamber layer has multiple processing spaces along the radial direction, and when stacked, there are at least three processing spaces along the radial direction, which are, from the inside out, a vortex mixing zone, a filtration separation zone, and a centrifugal enrichment zone. The sealing layer has a sample inlet near the center and a sample outlet near the edge. The experimental sample can enter through the sample inlet and flow into the vortex mixing zone for vortex extraction. After extraction, the experimental sample can pass through the filter membrane layer and, under external force, reach the filtration separation zone from the main chamber layer, and finally reach the centrifugal enrichment zone and be taken out through the sample outlet.

2. The microfluidic chip according to claim 1, characterized in that: The sealing layer, the main chamber layer, the filter membrane layer, and the secondary chamber layer have multiple independent processing units along the circumference. Each processing unit includes the vortex mixing zone, the filtration separation zone, the centrifugation enrichment zone, the sample inlet, and the sample outlet.

3. The microfluidic chip according to claim 1, characterized in that: The sealing layer comprises an upper sealing layer, a middle sealing layer, and a lower sealing layer that are sequentially bonded together from top to bottom.

4. The microfluidic chip according to claim 1, characterized in that: The filter membrane layer includes an upper filter membrane layer, a middle filter membrane layer, and a lower filter membrane layer that are sequentially bonded together from top to bottom. The upper filter membrane layer and the lower filter membrane layer can support the middle filter membrane layer.

5. The microfluidic chip according to claim 1, characterized in that: The filtration separation zone includes a first filtration separation zone and a second filtration separation zone in the radial direction, and both the first filtration separation zone and the second filtration separation zone are embedded with a secondary hydrophilic polytetrafluoroethylene filter membrane.

6. A microfluidic extraction system, characterized in that: The device includes a rotary drive, a control system, and a microfluidic chip as described in any one of claims 1-5. The output end of the rotary drive can be connected to and fixed to the microfluidic chip. The rotary drive is used to drive the microfluidic chip to perform vortex extraction or centrifugal separation. The control system is electrically connected to the rotary drive.

7. The microfluidic extraction system according to claim 6, characterized in that: It also includes a vortex base, a centrifugal base, and multiple positioning holes. The multiple positioning holes are distributed along the diameter direction of the microfluidic chip, and one positioning hole is provided at the center position. Positioning posts are provided on the vortex base and the centrifugal base. The positioning posts can be inserted into the positioning holes. Both the vortex base and the centrifugal base can be fixedly connected to the output end of the rotary drive device.

8. The microfluidic extraction system according to claim 6, characterized in that: It also includes a power module, a display screen, and multiple control buttons. The power module is used to supply power, the display screen is used to display the operating status, and the control buttons are used to adjust parameters.

9. A microfluidic extraction method, characterized in that: The extraction is performed using the microfluidic extraction system as described in claim 6, comprising the following steps: S1: Prepare the sample to be tested; S2: Prepare the microfluidic chip, which is made of polymethyl methacrylate and whose internal channels are manufactured by laser processing; S3: The sample to be tested is added into the microfluidic chip through the injection port using a micro-injection pump or a manual injection device; S4: Connect the microfluidic chip to the rotary drive device and control the rotary drive device to rotate at a preset speed so that the sample to be tested and the vortex mixing zone generate vortices; S5: Adjust the rotation speed of the rotary drive device so that the sample to be tested is slowly centrifuged in the filtration and separation zone to initially separate the soil particles from the extract. S6: Adjust the rotation speed of the rotary drive device again so that the sample to be tested is centrifuged at high speed in the centrifugal enrichment zone to obtain a clear supernatant of heavy metal leaching solution. S7: The clarified supernatant of the heavy metal leachate is exported through the sample outlet and subjected to qualitative and quantitative analysis of heavy metals.

10. The microfluidic extraction method according to claim 1, characterized in that: Step S1 includes S101: Collect soil samples from the target area, remove impurities, air-dry or oven-dry, and then grind them to sieve to ensure uniform sample particle size; S102: Prepare a weak acid extract.

Images