Microfluidic detection system and liquid detection method

Abstract

The present application relates to the technical field of microfluidic detection, and discloses a microfluidic detection system and a liquid detection method, wherein the microfluidic detection system comprises a paper-based microfluidic chip with a detection cell (21) and a regulation unit, the regulation unit is configured to regulate at least one of the environmental temperature, air flow speed, humidity and vacuum degree of the area where the detection cell is located, so as to regulate the limited evaporation speed of the liquid in the detection cell through the vent hole. According to the migration mechanism of colorimetric on the paper chip, the evaporation speed of different positions of the detection cell is regulated by covering the non-water-permeable and air-permeable part with a vent hole on the detection cell, and at the same time, the evaporation speed of the liquid in the detection cell through the vent hole is regulated by using the regulation unit, so as to effectively improve the efficiency of the colorimetric migrating and enriching with the supplement of moisture to the position with faster evaporation speed in the evaporation process, improve the detection sensitivity and reduce the detection limit.

Description

Technical Field

[0001] This invention relates to microfluidic detection technology, specifically to a microfluidic detection system. Furthermore, this invention also relates to a liquid detection method based on a paper-based microfluidic chip. Background Technology

[0002] Microfluidic technology has broad application prospects in water quality testing, environmental monitoring, and food and medical fields due to its advantages such as rapid mass and heat transfer, high analytical efficiency, low reagent consumption, low analytical cost, environmental friendliness, and ease of integration, as well as its compatibility with small and portable testing and analysis instruments. While microfluidic technology provides a new direction for the development of testing and analysis instruments such as portable water quality analyzers, the additional fluid control requirements and the relatively large size of the testing equipment also present new challenges to achieving portability.

[0003] Paper-based microfluidic chips can effectively overcome this difficulty in fluid control. A paper-based microfluidic chip, or simply "paper chip," is a self-driven microfluidic analysis technology platform that relies on capillary forces. Compared to microfluidic chips based on other substrates, paper chips are characterized by low cost and high portability, showing great potential in water quality testing, environmental monitoring, and food and medical fields. With the continuous development and advancement of smartphone photography technology and software functions, images of the paper chip's detection cell can be captured by a mobile phone, allowing for colorimetric recognition and colorimetric analysis via built-in software. This eliminates the need for additional signal analysis equipment. The combination of paper chips and mobile phone image analysis can further promote the portability of detection equipment.

[0004] However, due to the limited reagent capacity, the inhomogeneity of paper materials, and the problems of insufficient color development, poor uniformity, and poor repeatability caused by capillary action (such as the coffee ring effect), paper chip detection suffers from low sensitivity and detection limit, as well as insufficient accuracy and repeatability. These issues have become common problems restricting the development of paper chip detection technology.

[0005] To improve the sensitivity and accuracy of paper-based microarray detection, researchers have made numerous efforts. For example, by designing bidirectional liquid inlet channels, reagents are pre-placed on both sides of the detection cell, and a dual-side injection method is adopted. This allows the reagents to enter the detection cell from both sides under the influence of the analyte liquid, reducing color diffusion towards the edge of the detection cell and thus improving color uniformity. Another example is utilizing the enrichment effect of the coffee ring effect, sampling color from the coffee rings formed after the colorimetric reaction, lowering the detection limit of the target analyte. Furthermore, existing technologies have proposed utilizing the adsorption of target analytes by noble metal nanoparticles and carbon quantum dots, loading these adsorbed substances onto the paper-based microarray for target enrichment, thereby improving detection sensitivity. However, these methods still have drawbacks: improving color uniformity can result in a more uniform color distribution, but it cannot improve detection sensitivity or lower the detection limit; quantification through coffee ring enrichment is problematic because the randomness and variability of coffee ring formation make it impossible to fix the sampling location, leading to significant color differences due to different sampling locations, which cannot guarantee the accuracy, repeatability, and operability of the detection. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of insufficient colorimetry and uneven colorimetric dispersion of existing colorimetric quantitative paper chips, which lead to insufficient detection limits and detection sensitivity, as well as low detection accuracy and repeatability. This invention provides a microfluidic detection system and liquid detection method that have high detection accuracy and sensitivity, can effectively reduce the detection limit of liquids, and have good operability and repeatability.

[0007] To achieve the above objectives, the present invention provides a microfluidic detection system, comprising: a paper-based microfluidic chip, the paper-based microfluidic chip including a paper base layer having a detection pool, a bottom layer disposed on a first side of the paper base layer, and a cover layer disposed on a second side of the paper base layer opposite to the first side, the bottom layer and the cover layer having a non-permeable and permeable portion covering the detection pool, and the portion of the cover layer covering the detection pool having a vent hole; and a control unit configured to control at least one of the ambient temperature, air flow velocity, humidity, and vacuum degree in the area where the detection pool is located, so as to control the confined evaporation rate of liquid in the detection pool through the vent hole.

[0008] Preferably, the vent is a regular polygon or a circle. Preferably, the diameter of the vent or the diameter of its circumscribed circle is 0.5mm-5mm, and more preferably 1mm-3mm.

[0009] Preferably, the paper base layer is further provided with a sample application area and a diffusion channel connecting the sample application area and the detection pool; and a sample application hole is provided on the cover layer at a position corresponding to the sample application area.

[0010] Preferably, a colorimetric reagent is pre-placed in the detection cell and / or the diffusion channel.

[0011] Preferably, the paper substrate is further provided with a liquid storage tank arranged around the detection pool to be used for replenishing liquid to the detection pool.

[0012] Preferably, the control unit includes a heating plate, which is configured to maintain the ambient temperature of the area where the detection pool is located within a predetermined temperature range of 25°C to 60°C.

[0013] Preferably, the control unit includes a ventilation device configured to release pressurized gas above the detection pool and / or displace the air above the detection pool.

[0014] Preferably, the control unit includes a vacuum drying oven, and the paper-based microfluidic chip is arranged inside the vacuum drying oven.

[0015] A second aspect of the present invention provides a liquid detection method, comprising:

[0016] S1. The liquid to be tested is introduced into the detection cell of the paper-based microfluidic chip, wherein the paper-based microfluidic chip includes a paper base layer on which the detection cell is formed, a bottom layer disposed on a first side of the paper base layer, and a cover layer disposed on a second side of the paper base layer opposite to the first side. The bottom layer and the cover layer have a non-water-permeable and air-permeable portion covering the detection cell, and the portion of the cover layer covering the detection cell is formed with a vent hole.

[0017] S2. The paper-based microfluidic chip is left to stand for a predetermined time, wherein at least one of the ambient temperature, air flow speed, humidity and vacuum level in the area where the detection cell is located is adjusted;

[0018] S3. Perform colorimetric identification and / or colorimetric analysis on the predetermined area within the detection pool.

[0019] Preferably, in step S2, the ambient temperature of the area where the detection pool is located is between 25°C and 60°C.

[0020] Through the above technical solution, this invention, based on the migration mechanism of color on a paper chip, regulates the evaporation rate at different locations in the detection cell by covering the detection cell with a non-permeable and permeable part formed with vent holes. At the same time, the control unit regulates (increases) the evaporation rate of the liquid in the detection cell through the vent holes, thereby effectively improving the efficiency of color migration and enrichment as water is replenished to locations with faster evaporation during the evaporation process. Ultimately, color spots are formed in the detection cell, thereby improving the color and uniformity per unit area under the premise of the same concentration of the target analyte, improving detection sensitivity and reducing the detection limit, while increasing the sampling range and improving the operability of sampling and detection repeatability. Attached Figure Description

[0021] Figure 1 This is an exploded view of a paper-based microfluidic chip according to a preferred embodiment of the present invention;

[0022] Figure 2 It is a scatter plot showing the relationship between the color enrichment effect and the vent diameter;

[0023] Figure 3 This is a schematic diagram of a paper-based microfluidic chip according to another preferred embodiment of the present invention;

[0024] Figure 4 It is a display Figure 3 Detection results of paper-based microfluidic chips;

[0025] Figure 5 This is a comparison chart of the color enrichment effects of different paper-based microfluidic chips;

[0026] Figure 6 This is a schematic diagram of a paper-based microfluidic chip according to another preferred embodiment of the present invention;

[0027] Figure 7 This is a detection cell distribution diagram of a paper-based microfluidic chip according to another preferred embodiment of the present invention;

[0028] Figure 8 It is a scatter plot showing the relationship between colorimetric enrichment effect and detection time under different ambient temperatures;

[0029] Figure 9 This is an exploded view of a paper-based microfluidic chip according to Embodiment 1 of the present invention;

[0030] Figure 10 yes Figure 9 A schematic diagram of the color enrichment effect of a paper-based microfluidic chip;

[0031] Figure 11 This is a schematic diagram of the structure of a paper-based microfluidic chip according to Embodiment 2 of the present invention;

[0032] Figure 12 yes Figure 11 A schematic diagram of the color enrichment effect of a paper-based microfluidic chip;

[0033] Figure 13 and Figure 14 The figures are quantitative curves of the paper-based microfluidic chip of Embodiment 3 of the present invention.

[0034] Explanation of reference numerals in the attached figures

[0035] 1-Bottom layer; 2-Paper base layer; 21-Detection pool; 22-Sample application area; 23-Diffusion channel; 24-Liquid storage pool; 3-Cover layer; 31-Ventilation hole; 32-Sample application hole; 4-Liquid. Detailed Implementation

[0036] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0037] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0038] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. They can refer to a mechanical connection or an electrical connection. They can refer to a direct connection or an indirect connection through an intermediate medium, and they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0039] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0040] The following provides many different embodiments or examples for implementing various structures of the present invention. To simplify the disclosure of the invention, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0041] In this invention, the endpoints of the disclosed ranges and any values ​​are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0042] A first aspect of the present invention provides a microfluidic detection system, including a paper-based microfluidic chip and a control unit. Figure 1 The diagram shows an exploded view of a paper-based microfluidic chip used in a preferred embodiment of the microfluidic detection system of the present invention. The paper-based microfluidic chip includes a paper base layer 2 and a bottom layer 1 and a top layer 3 respectively covering both sides of the paper base layer 2. The paper base layer 2 can be made of paper / paper-like materials such as filter paper or cellulose membranes. As a technical platform for microfluidic analysis, such as liquid detection, it has advantages over ordinary microfluidic chips, including lower cost, no need for external drive, good biocompatibility, and high portability. The paper-based microfluidic chip may have one or more paper base layers 2, and the thickness of the paper base layer 2 is generally not particularly required. In the various embodiments shown in the accompanying drawings of the present invention, only the case of a single paper base layer 2 is schematically shown for clarity of the relevant structures.

[0043] The paper substrate 2 has a detection pool (not shown). The liquid 4 to be tested (such as sewage, food or pharmaceutical solution) can be passed into the detection pool to detect / analyze the composition, concentration and other information of the liquid 4 through colorimetric identification, colorimetric analysis and other means described later.

[0044] The bottom layer 1 can be attached to the lower side (first side) of the paper base layer 2 by means of adhesion or other methods, and the top layer 3 can also be attached to the upper side (second side) of the paper base layer 2 by means of adhesion or other methods. The top layer 3 and the bottom layer 1 can form a non-permeable and permeable portion, either entirely or only partially covering the detection cell. For example, the top layer 3 and the bottom layer 1 can be made entirely of a non-permeable and permeable material, or only partially covering the detection cell. Specifically, the non-permeable and permeable material can be polyvinyl chloride, polyethylene, polypropylene, polystyrene, silicone, polytetrafluoroethylene, etc. Alternatively, the top layer 3 and the bottom layer 1, which are made of permeable materials, can be treated to be hydrophobic, such as by coating filter paper with wax and heating it to allow the wax to penetrate the filter paper, or by immersing the filter paper in a plastic solution dissolved in an organic solvent and then drying it. The bottom layer 1 and the top layer 3 can be in contact with each other or not. Their areas and shapes are not required to be the same, nor are they required to be larger than the paper base layer 2, but both must completely cover the detection cell. Furthermore, the bottom layer 1 and the top layer 3 can be made of transparent or opaque materials, preferably transparent materials.

[0045] The capping layer 3, covering the detection pool, has vent holes 31, allowing the liquid in the detection pool to evaporate within a confined area. Thus, the vent holes 31 guide the liquid in the detection pool to converge towards them during evaporation, thereby enriching the color at that location. Specifically, the capping layer 3 covers the edge of the detection pool, preventing liquid from evaporating from the edge. Simultaneously, the vent holes 31 on the capping layer 3 connect the detection pool to the external space, ensuring that the liquid in the detection pool can only evaporate outwards through these vent holes 31. Therefore, during evaporation, the moisture near the vent holes 31 evaporates faster, and moisture from the edge replenishes the area near the vent holes 31, carrying color to that location and forming color-enriched spots.

[0046] Importantly, the microfluidic detection system of the present invention includes a control unit for regulating the confined evaporation rate of liquid in the detection cell through the vent 31. This control unit can be configured to regulate at least one of the ambient temperature, airflow velocity, humidity, and vacuum level in the area where the detection cell is located. Therefore, during the evaporation process, the efficiency of color migration and accumulation as moisture is replenished to areas with faster evaporation rates can be effectively improved, ultimately forming color spots in the detection cell. This increases color intensity and uniformity per unit area while maintaining the same concentration of the analyte, thereby improving detection sensitivity and lowering the detection limit. Simultaneously, it increases the sampling range, improving sampling operability and detection repeatability.

[0047] In the microfluidic detection system of the present invention, the control unit can be configured in various appropriate forms according to the control method. For example, in a preferred embodiment, the control unit may include a heating plate to raise or maintain the ambient temperature of the area where the detection cell is located through heat exchange. Preferably, the heating plate is capable of maintaining the ambient temperature of the area where the detection cell 21 is located within a predetermined temperature range of 25°C to 60°C, which is beneficial for improving the color enrichment efficiency and shortening the detection time.

[0048] In another preferred embodiment, the control unit may include a venting device that can accelerate the gas flow rate above the vent 31 by releasing pressurized gas above the detection pool, thereby accelerating liquid evaporation. Alternatively, the venting device may be configured to displace the air above the detection pool to reduce the humidity of the gas above the vent 31.

[0049] In another preferred embodiment, the control unit may further include a vacuum drying oven, whereby the paper-based microfluidic chip can be placed inside the vacuum drying oven during the detection process, thereby reducing the air pressure of the environment in which the detection cell is located and effectively increasing the speed at which the liquid in the detection cell evaporates outward through the vent.

[0050] It is understood that the aforementioned different control units can be used individually or in combination, and all of them can improve the migration and enrichment efficiency of color by accelerating the evaporation rate of the liquid, thereby improving detection sensitivity and lowering the detection limit. In the following description, the advantages of the present invention will be illustrated primarily by taking the control of ambient temperature as an example.

[0051] In this invention, the vent 31 can be a regular polygon or a circle, and its diameter or circumscribed circle diameter can be 0.5mm-5mm, preferably 1mm-3mm. The vent 31 can be positioned above the center of the detection cell to ensure uniform color enrichment during the liquid evaporation process within the detection cell. The pore size of the vent 31 has a significant impact on the color enrichment effect, such as... Figure 2 As shown, within a certain range (before the color reaches saturation), the smaller the aperture of the vent, the higher the color of the resulting spot. For example, when the vent aperture is 3mm, the enriched color (distance) is only about 120; while when the vent aperture is 1.5mm, the enriched color (distance) can reach over 200. Therefore, to achieve a better color enrichment effect, the diameter or circumscribed circle diameter of the vent 31 can be set to 1mm-3mm, but this may require a longer enrichment time. To address this, the control unit of this invention can accelerate liquid evaporation by controlling the ambient temperature, humidity, and vacuum level in the area where the detection cell is located. This can compensate for the adverse effects of the small aperture of the vent 31 on the evaporation rate and color enrichment efficiency.

[0052] Figure 3 An improved embodiment of the paper-based microfluidic chip of the present invention is shown, which provides a chip structure with a gain effect. Specifically, the paper-based microfluidic chip has a liquid reservoir 24 arranged around the detection cell 21 on the paper base layer 2. When the liquid in the detection cell 21 cannot fully migrate to the vicinity of the vent hole 31 due to the excessively fast evaporation rate, colorless liquid can be added to the liquid reservoir 24 to replenish the liquid that needs to be evaporated in the detection cell 21, thereby continuing to drive the color to migrate to the vicinity of the vent hole 31. As a channel for replenishing the liquid, one or more openable and closable liquid replenishment holes can be formed on the portion of the cover layer 3 covering the liquid reservoir 24. The liquid replenishment holes can be opened when liquid replenishment is needed and closed after liquid replenishment is completed. In actual detection, the colorless liquid added to the liquid reservoir 24 can be water or a mixture of different solvents, but the added liquid needs to be able to dissolve / carry the color and not interact with other parts of the chip. The detection effect of the paper-based microfluidic chip with added liquid reservoir 24 is as follows: Figure 4 As shown; Figure 5 A comparison of the color enrichment effect of paper-based microfluidic chips with and without the liquid reservoir 24 is shown. It can be seen that by adding supplementary liquid to the liquid reservoir 24, the enrichment degree of color near the vent can be significantly improved. Under the same conditions, the chip without the liquid reservoir (chip 2) enriches the color from 48.2 to 190.3, while the chip with the liquid reservoir (chip 1) enriches the color from 49.4 to 257.4.

[0053] In some embodiments of the present invention, the liquid to be tested can be directly added to the detection pool 21 from above, for example, the aforementioned vent 31 can be used as a sample addition port. In other embodiments, a sample addition area 22 can be provided at other locations on the paper base layer 2 that are separated from the detection pool 21, and the sample addition area 22 and the detection pool 21 can be connected by a diffusion channel 23. Correspondingly, a sample addition port 32 can be provided on the cover layer 3 at the position corresponding to the sample addition area 22, such as... Figure 6 As shown. Thus, the liquid to be tested can be injected into the sample application area 22 through the sample application port 32, and under self-driving action, enter the detection cell 21 through the diffusion channel 23, where it will then undergo subsequent color enrichment and detection processes. In some embodiments of the present invention, such as... Figure 7 As shown, the detection cells 21 can be configured in multiple ways, and the number can be determined according to the number of samples to be detected and / or the number of parameters to be detected. Preferably, each detection cell 21 is equidistant from the sample application area 22, meaning that the lengths of each diffusion channel 23 are equal. Seven detection cells 21 are arranged around the central sample application area 22, so that when multiple samples need to be detected in parallel or repeated tests are required, detection can be completed in a single chip test, improving detection throughput and further reducing errors between parallel tests.

[0054] To facilitate detection, a colorimetric reagent can be pre-placed in the detection pool 21 or the aforementioned diffusion channel 23. This colorimetric reagent can make the liquid in the detection pool 21 exhibit a clearly visible color through methods such as chemical reactions, so as to perform colorimetric identification and colorimetric analysis.

[0055] The microfluidic detection system of the present invention may also have other related equipment used in conjunction with the above-mentioned paper-based microfluidic chip, such as chip carriers, cameras, etc.

[0056] Figure 8 The relationship between chromaticity distance and detection time is shown at ambient temperatures of 25℃, 35℃, and 45℃. It can be seen that the chromaticity enrichment rate at ambient temperatures of 35℃ and 45℃ is significantly higher than that at 25℃, while the final enrichment levels are essentially the same. Therefore, by setting appropriate control units, detection efficiency can be effectively improved.

[0057] A second aspect of the present invention also provides a liquid detection method, comprising the following steps: S1. Introducing the liquid to be tested into the detection cell 21 of a paper-based microfluidic chip, wherein the paper-based microfluidic chip includes a paper base layer 2 on which the detection cell 21 is formed, a bottom layer 1 disposed on a first side of the paper base layer 2, and a cover layer 3 disposed on a second side of the paper base layer 2 opposite to the first side, the bottom layer 1 and the cover layer 3 having a non-water-permeable and air-permeable portion covering the detection cell 21, and the portion of the cover layer 3 covering the detection cell 21 having a vent hole 31; S2. Allowing the paper-based microfluidic chip to stand for a predetermined time, wherein at least one of the ambient temperature, air flow velocity, humidity and vacuum degree of the area where the detection cell 21 is located is controlled, for example, maintaining the ambient temperature of the area where the detection cell 21 is located between 25°C and 60°C (preferably 35°C and 45°C); S3. Performing colorimetric identification and / or colorimetric analysis on a predetermined area within the detection cell 21.

[0058] The present invention will be described in detail below through embodiments, wherein the contact angle is measured by an OCA200 fully automatic single fiber contact angle measuring instrument.

[0059] Example 1

[0060] Figure 9The paper-based microfluidic chip shown in this embodiment includes a bottom layer 1, a paper base layer 2, and an enrichment layer 25. The paper base layer 2 has six detection cells 21 arranged in a ring array and a blank control detection cell located in the middle; the enrichment layer 25 is an enrichment carrier attached to each detection cell 21, which is located in the middle of the detection cell 21 (including but not limited to the center). The detection cells 21 are made of a material with a large contact angle (such as filter paper modified with fluorinated silane reagents or plastic sheets with a large contact angle), and the enrichment carrier is made of a material with a smaller contact angle (such as filter paper, cellulose filter membrane, or other materials treated with plasma or surface modified). The enrichment carrier is smaller than the detection cells 21 and forms a second contact angle region with a smaller contact angle, which is generally preferably circular or regular polygonal with a circumscribed circle diameter of 1mm-3mm; the other parts within the detection cells 21 form a first contact angle region with a larger contact angle. The enrichment carrier, detection cells, and bottom layer are adhered to each other by adhesive or other means.

[0061] The reacted colored solutions (e.g., a 0.1% dye solution, or a mixture of analyte solutions of different concentrations and specific reagents) were added dropwise to the detection cells arranged in a ring array. The central detection cell served as a blank control. The color enrichment effect was as follows: Figure 10 As shown in the table below. After colorimetric enrichment under specific conditions (e.g., 35℃, 10 min), the detection cell was photographed under natural light, and the RGB values ​​of the photographs were analyzed to calculate the colorimetric distance D. The colorimetric values ​​after enrichment with a 0.1% red dye solution are shown in the table below:

[0062]

[0063] Example 2

[0064] This embodiment uses a three-layer paper chip as the base chip for color enhancement and an aqueous solution with added dye as the sample. This is to illustrate that the present invention can enhance the color of all color-based solutions and to show that the color enrichment phenomenon occurs in any small area that is open to the atmosphere, without needing to be coaxial with the sample well.

[0065] The structure of a paper chip is as follows Figure 11As shown, transparent, non-breathable films are applied to the upper and lower sides of a paper substrate prepared by cutting. The upper film (cover layer) has ventilation holes at the corresponding detection cells. Sample application holes are located at the same distance from each detection cell. A dye solution is injected through the sample application holes, distributing along hydrophilic diffusion channels and reaching each detection cell 1-7. The paper chip is placed naturally (ambient temperature 26℃, humidity 70%). After a period of time (10 min–60 min), chromaticity is enriched in the ventilation hole areas of the detection cells. Over time, the chromaticity of the enriched areas becomes increasingly distinct from that of other areas. RGB values ​​of the chromaticity in different detection cells and multiple areas within the same detection cell are read, and the results are shown in the table below. Figure 12 As shown:

[0066]

[0067]

[0068] As can be seen from the table above, the R, G, and B values ​​are similar between different detection pools and between different regions of the same detection pool. Furthermore, the standard deviation of the R, G, and B values ​​between different detection pools and between different regions of the same detection pool is less than 3%, indicating that the color enhancement and liquid detection method proposed in this invention has good uniformity and repeatability.

[0069] Example 3

[0070] This example illustrates how the chromatic enrichment structure reduces the limit of nickel detection in water.

[0071] The paper-based microfluidic chip used in this embodiment has a bottom layer of transparent, non-permeable membrane. The paper base layer is a hydrophobically modified filter paper (the sample application area, diffusion channel, and detection cell remain hydrophilic, while the remaining areas are modified to be hydrophobic; the detection cell is pre-filled with a compound reagent with dimethylglyoxime as the main component, which can undergo a specific colorimetric reaction with nickel). The top layer is a transparent, non-permeable membrane with a sample application port communicating with the sample application area and a vent communicating with the detection cell. The detection cell has a diameter of 4 mm, and the vent has a pore size of 2 mm.

[0072] During testing, a nickel-containing aqueous sample is injected through the sample loading port. The sample flows along the diffusion channel to the detection cell and reacts with the compound reagent to generate a pink substance. After the chip is left to stand for a period of time, water vapor evaporates along the vent holes on the cover layer. The colorimetric components diffuse and accumulate in the color-rich area under the influence of evaporation, gradually deepening the color. After the reaction is complete, the color-rich area of ​​the paper chip is photographed, and the colorimetric information of this area is extracted using MATLAB for quantitative calculation.

[0073] according to Figure 13 and Figure 14It can be seen that the detection limit of ordinary paper chips for nickel in water is relatively high; after color enrichment, the detection limit of nickel in water is reduced to 0.1 mg / L, showing a significant reduction in the detection limit. Standard curve fitting was performed on nickel solutions within the linear range, revealing a very significant improvement in the linearity of the fitted lines.

[0074] Example 4

[0075] This embodiment illustrates the reduction in the detection limit of chromium in water resulting from a color enrichment structure.

[0076] The paper-based microfluidic chip used in this embodiment has a bottom layer of transparent, non-permeable membrane, an intermediate layer of hydrophobically modified filter paper (the sample application area, diffusion channel, and detection cell remain hydrophilic, while the remaining areas are modified to be hydrophobic; the detection cell is pre-filled with a compound reagent mainly composed of diphenylcarbazide, which can undergo a specific colorimetric reaction with chromium), and a top layer of transparent, non-permeable membrane with a sample application port communicating with the sample application area and a vent port communicating with the detection cell. The detection cell has a diameter of 4 mm, and the vent port has a diameter of 2.5 mm.

[0077] During testing, a chromium-containing aqueous sample is injected into the sample application area. The sample flows along the diffusion channel to the detection cell and reacts with the compound reagent to generate a pink substance. After the chip is left for a period of time, water vapor evaporates along the vent holes on the cover layer. Driven by evaporation, the colorimetric components diffuse and accumulate in the color-rich area, and the color gradually deepens.

[0078] The results showed that before color enrichment, the detection limit for chromium on ordinary paper chips was 0.05 mg / L; after enhanced color development based on the paper chips of this embodiment, the detection limit decreased to 0.03 mg / L.

[0079] Example 5

[0080] This example illustrates how the color enrichment structure reduces the detection limit of nitrite in water.

[0081] The paper-based microfluidic chip used in this embodiment has a bottom layer of transparent, non-permeable membrane. The paper base layer is hydrophobically modified filter paper (the sample application area, diffusion channel, and detection cell remain hydrophilic, while the remaining areas are modified to be hydrophobic; the detection cell is pre-filled with Gliese reagent, which can undergo a specific colorimetric reaction with nitrite). The top layer is a transparent, non-permeable membrane with a sample application port communicating with the sample application area and a vent hole communicating with the detection cell. The detection cell has a diameter of 5 mm, and the vent hole has a diameter of 2 mm.

[0082] During testing, a chromium-containing aqueous sample is added from the sample application area. The sample flows along the diffusion channel to the detection cell and reacts with the compound reagent to generate a pink substance. After the chip is left for a period of time, water vapor evaporates along the vent holes on the cover layer. The color-developing components diffuse and accumulate in the color-rich area under the influence of evaporation, and the color gradually deepens.

[0083] The results showed that before color enrichment, the detection limit for chromium on ordinary paper chips was 0.1 mg / L. After enhanced color development based on the paper chips of this embodiment, the detection limit decreased to 0.05 mg / L.

[0084] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0085] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. However, these simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A microfluidic detection system, characterized in that, include: A paper-based microfluidic chip includes a paper base layer (2) having a detection pool (21), a bottom layer (1) disposed on a first side of the paper base layer (2), and a cover layer (3) disposed on a second side of the paper base layer (2) opposite to the first side. The bottom layer (1) and the cover layer (3) have non-permeable and permeable portions covering the detection pool (21), and the portion of the cover layer (3) covering the detection pool (21) has a vent hole (31). The paper base layer (2) is also provided with a liquid reservoir (24) arranged around the detection pool (21) for replenishing liquid to the detection pool (21), and the portion of the cover layer (3) covering the liquid reservoir (24) has one or more openable and closable liquid replenishment holes. as well as, The control unit is configured to control at least one of the ambient temperature, air flow speed, humidity and vacuum degree of the area where the detection pool (21) is located, so as to control the confined evaporation rate of the liquid in the detection pool (21) through the vent (31).

2. The microfluidic detection system according to claim 1, characterized in that, The vent (31) is a regular polygon or a circle.

3. The microfluidic detection system according to claim 2, characterized in that, The diameter or circumscribed circle diameter of the vent (31) is 0.5mm-5mm.

4. The microfluidic detection system according to claim 3, characterized in that, The diameter or circumscribed circle diameter of the vent (31) is 1mm-3mm.

5. The microfluidic detection system according to claim 1, characterized in that, The paper base layer (2) is also provided with a sample feeding area (22) and a diffusion channel (23) connecting the sample feeding area (22) and the detection pool (21). Furthermore, a sample feeding hole (32) is provided on the cover layer (3) at the position corresponding to the sample feeding area (22).

6. The microfluidic detection system according to claim 5, characterized in that, The detection pool (21) and / or the diffusion channel (23) are pre-filled with colorimetric reagents.

7. The microfluidic detection system according to claim 1, characterized in that, The control unit includes a heating plate, which is configured to maintain the ambient temperature of the area where the detection pool (21) is located within a predetermined temperature range of 25°C to 60°C.

8. The microfluidic detection system according to claim 1, characterized in that, The control unit includes a ventilation device configured to release pressurized gas and / or displace the air above the detection pool (21) above the detection pool (21).

9. The microfluidic detection system according to claim 1, characterized in that, The control unit includes a vacuum drying chamber, and the paper-based microfluidic chip is arranged inside the vacuum drying chamber.

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