Preparation method and application of trapezoidal paper-based sweat micro-fluidic patch

Abstract

The invention discloses a trapezoidal micro-fluidic patch and a preparation method thereof, is used for real-time sweat observation, and relates to the field of real-time sweat monitoring. The trapezoidal micro-fluidic patch comprises a paper-based monitoring layer, and is mainly used for carrying out visual monitoring by collecting biomarkers in sweat, and finally marking scales by using a distance method to obtain experimental data. The micro-fluidic patch is composed of an adhesion layer, a trapezoidal micro-fluidic chip layer, a scale layer and a packaging layer, the preparation process is simple, markers in human sweat can be rapidly monitored, and accurate reading can be achieved. The micro-fluidic chip adopts a novel channel design (an asymmetric trapezoidal channel), and how the geometric structure of the channel improves the analysis performance by influencing a distance signal is researched on the basis of a distance mu PAD. Trapezoidal channels (channel width linearly varies with height) are used to create paper surface (titrant) gradients that can be used for reactions, thereby reducing the distance of pigment in solution between the paper base upper tip and the liquid tip. Along with the increase of the channel width, the trapezoidal structure provides higher sensitivity and lower detection limit for chloride determination in a concentration range of 0.05-25mM. The preparation method mainly comprises the following steps: pre-printing the scale indicator and the detection reagent on the trapezoidal micro-fluidic chip layer, and finally drying and packaging. According to the technology, a traditional silver measuring method (Moire precipitation titration method) is converted into a small-sized, simple, portable and low-cost paper microfluid diagnosis device, and rapid and quantitative analysis can be provided.

Description

Technical Field

[0001] The invention relates to the technical field of sweat monitoring, in particular to a trapezoidal paper-based microfluidic patch sweat analysis and a preparation method thereof. Background Art

[0002] In recent years, with the rapid development of wearable health monitoring devices, sweat, as a non-invasive and biocompatible body fluid sample, has received widespread attention. Sweat is rich in electrolytes (such as sodium ions, potassium ions, chloride ions), metabolites (such as glucose, lactate), and hormones (such as cortisol) and other biomarkers. The concentration changes of these components are closely related to human health. Therefore, sweat-based instant detection devices have important application prospects in the fields of exercise monitoring, chronic disease management, and mental health assessment.

[0003] Paper-based microfluidic technology has become a potential tool in the field of sweat detection due to its low cost, portability and ease of operation. This technology uses capillary action to drive liquid flow, avoiding dependence on complex equipment, and is particularly suitable for resource-limited environments and point-of-care testing (POCT) needs. However, traditional paper-based microfluidic devices are usually designed as rectangular channels, which have limitations in fluid transfer rate, detection sensitivity and versatility, and are difficult to meet the precise detection of multiple biomarkers. In addition, traditional devices mostly use pigment channels to determine marker concentrations by colorimetry or distance methods, but the flow characteristics of the liquid in the paper-based device cause a distance deviation between the pigment front and the liquid front, resulting in inaccurate readings and affecting the reliability and accuracy of the detection.

[0004] Some studies have developed devices that can instantly detect chloride, glucose, lactate concentrations and pH values ​​in sweat. However, most of these devices rely on the assistance of additional equipment to accurately measure the concentrations of the corresponding markers. In addition, such devices can usually only provide the concentration of sweat components at a certain moment, lack in-depth analysis of sweat components, and cannot perform continuous monitoring at different times. This limits its potential for application in dynamic physiological states and makes it difficult to monitor real-time changes in biomarkers in sweat.

[0005] Patent CN 114942242 A uses a traditional rectangular structure device to analyze the chloride ion concentration in sweat. The patent mentions that the reagent reaction channel will change color after a period of time, which may cause the device to fail. In addition, the liquid inlet of the device is designed to be small, which takes a long time to collect sweat, thus limiting its convenience and efficiency in practical applications. Therefore, the device has obvious limitations in dynamic monitoring and real-time feedback, and may not meet the needs of rapid and continuous detection.

[0006] In the past, when paper-based microfluidic chips were used to detect sweat or other liquids, pigments were usually used as feedback. However, most traditional papers use regular channel designs, which results in a large gap between the front of the pigment and the front of the liquid. If the liquid flow exceeds the limit of the pigment, the pigment may stagnate, which in turn affects the accuracy of the experimental results. This phenomenon makes it difficult to accurately read the specific distance of the pigment, thereby reducing the reliability of the detection and limiting the application effect of paper-based microfluidic technology in biomarker analysis.

[0007] Current sweat flow rate detection patches still have many defects, mainly including low sweat collection efficiency, large amount of sweat required, and serious material waste. In addition, the preparation process of existing patches is relatively complicated, making it difficult to achieve the requirements of miniaturization and high-precision detection. These problems limit the effectiveness of sweat detection patches in practical applications, and there is an urgent need to improve the design and process to enhance its performance and user experience. Summary of the invention

[0008] In view of the problems existing in the above-mentioned technologies, the present invention is proposed.

[0009] The first object of the present invention is to provide a paper-based microfluidic patch based on a trapezoidal structure for sweat analysis and a preparation method thereof. The patch consists of an adhesive layer, a microfluidic main layer, a scale layer and an encapsulation layer. The microfluidic chip has the advantages of a simple structure, can effectively meet the needs of trace detection, and provide intuitive detection results. This design not only improves the analysis efficiency, but also enhances the user experience, and is suitable for wide application in the field of sweat detection.

[0010] The second purpose of the present invention is to provide a paper-based microfluidic chip that can be used for a long time and has a long shelf life, so as to solve the problem that traditional paper-based chips will become ineffective after a period of use. By optimizing materials and design, the chip can maintain stable performance for a longer period of time, ensuring its reliability and effectiveness in practical applications. This innovation will significantly enhance the application potential of paper-based microfluidic technology in long-term monitoring and analysis.

[0011] The third object of the present invention is to provide a method for preparing a paper-based microfluidic chip with intuitiveness and high accuracy for detecting the composition and volume of human sweat. The method first pre-coats the detection reagent on the paper base, washes it with water three times and then dries it, then applies a pigment on the trapezoidal paper base and dries it again, and finally encapsulates it. This process ensures the high sensitivity and accuracy of the chip, enabling it to effectively detect the composition and volume of sweat, and improves the user experience.

[0012] The fourth object of the present invention is to provide a paper-based microfluidic chip that can intuitively detect the concentration of human chloride ions, thereby helping to observe whether humans suffer from the genetic disease cystic fibrosis. By optimizing the design of the paper-based channel and the detection reagent, the chip can detect the concentration range of chloride ions in real time and intuitively. This design not only improves the convenience of detection, but also enables users to quickly judge the health status, which has important clinical application value.

[0013] The fifth object of the present invention is to provide a microfluidic main layer chip with an inverted trapezoidal structure. Compared with the traditional rectangular, serpentine and regular trapezoidal structures, the chip can effectively reduce the excessive distance between the pigment front end and the liquid front end, thereby improving the fluid transportation efficiency. This design can provide a higher quality liquid transmission effect, ensure the accuracy and reliability of the test results, and thus improve the application performance of paper-based microfluidic technology in biomarker analysis.

[0014] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0015] (1) Preparation of a detection solution: Cl - : Prepare potassium chromate solution and silver nitrate solution. Note that the silver nitrate solution needs to be stored away from light;

[0016] (2) Cutting of a filter paper structure: the filter paper is inkjet printed, the detection reagent is placed in the ink cartridge, and after a certain number of inkjet printings, a precipitate capable of detecting some biomarkers in human sweat is generated on the filter paper, and then the filter paper is cut using a CO2 laser to form the desired structure;

[0017] (3) Preparation of a trapezoidal paper-based microfluidic sweat patch: The potassium chromate solution and silver nitrate solution in the above (1) are printed on filter paper respectively. After a certain number of times, the required structure is drawn using CAD, and the structure is printed using a laser printer as the microfluidic main layer; it is placed on a 3M primer through a mold as an adhesion layer; there is also a scale layer and a packaging layer.

[0018] As a preferred embodiment, the sweat physiological markers mainly include: sweat volume and chloride ion concentration.

[0019] As a preferred solution, the paper-based microfluidic sweat patch structure is: an adhesion layer, a microfluidic main layer, a scale layer and a packaging layer. The microfluidic main layer is a dual-channel model of a regular trapezoid, a rectangle and an inverted trapezoid. The adhesion layer, the microfluidic main layer, the scale layer and the packaging layer are stacked in sequence from bottom to top.

[0020] As a preferred solution, the adhesive layer is provided with a liquid inlet, and the shape of the liquid inlet is provided with a fan-shaped structure, which can collect sweat in a larger range and prevent the disadvantage of insufficient sweat.

[0021] As a preferred embodiment, the microfluidic main layer is provided with a liquid inlet area, a pigment area, a reagent area, a reaction channel and a reference channel. The liquid inlet area is located directly above the liquid inlet of the adhesion layer and coincides with the fan-shaped top of the liquid inlet; the pigment area, reference channel, reagent area and reaction channel are independently located on both sides of the liquid inlet area.

[0022] As a preferred solution, the concentration of the potassium chromate solution in the detection solution of step (1) is 5-50mM, and the concentration of the silver nitrate solution is 100-250mM. By fixing the number of printing times and then adding chloride ion solution of the same volume and concentration, the optimal detection concentration is found to be 50mM potassium chromate and 200mM silver nitrate solution.

[0023] As a preferred solution, a laser is used to cut the printed filter paper into different shapes, namely, a regular trapezoid, a rectangle and an inverted trapezoid. When the same volume of 60 mM chloride ion solution is added, the inverted trapezoid filter paper generates the highest concentration of precipitation. Similarly, the inverted trapezoid requires the least amount of liquid for the same distance.

[0024] As a preferred solution, in order to obtain a paper-based microfluidic chip for measuring the chloride ion concentration in human sweat that can be used and stored for a long time, the cut microfluidic main layer needs to be processed. 50 mL of deionized water is measured in three beakers respectively. The cut microfluidic main layer is washed in three beakers in turn with tweezers, and each beaker is kept for no less than three minutes. Finally, the washed microfluidic main layer is placed in a drying oven at 50°C for five minutes, and then taken out and stored in a dark place.

[0025] As a preferred solution, the present invention also provides a detailed method for preparing an inverted trapezoidal paper-based microfluidic chip, the main steps are: mainly for the detection of chloride ion concentration in sweat, the preparation process is: 1) first select filter paper for printing, respectively place 50mM potassium chromate solution and 200mM silver nitrate solution in two ink cartridges, first print the shape with potassium chromate 20 times, and dry it between each time. After the filter paper is dried, print the silver nitrate solution 20 times, and the two generate yellow silver chromate precipitates, which also need to be dried; 2) then use a laser to print out an inverted trapezoidal microfluidic main layer, and wash it three times with deionized water and dry it; 3) cut the adhesion layer and set the liquid inlet area into a fan-shaped structure; 4) drip the pigment in the pigment area of ​​the microfluidic main layer; 5) all reagents are completely dried, and the adhesion layer, microfluidic main layer, scale layer, and packaging layer are packaged in sequence to obtain.

[0026] The above technical solution has the following beneficial effects:

[0027] (1) The paper-based microfluidic patch provided by the present invention requires a small amount of sweat and can achieve the effect of quickly collecting sweat.

[0028] (2) In the technical solution provided by the present invention, the patch is a dual-channel microfluidic patch with a trapezoidal structure, which is composed of an adhesion layer, a microfluidic main layer, a scale layer and an encapsulation layer. It has a simple structure and has the advantages of long-term storage and ready use. In the measurement of chloride ions, the patch can ensure the accuracy of the sample and effectively solve the defects of the silver titration method in the paper-based microfluidic chip, such as the blackening of the reagent area and the unclear sample effect. This innovative design significantly improves the reliability and repeatability of the detection and broadens its potential in practical applications.

[0029] (3) The technical solution provided by the present invention can quickly identify the concentration of chloride ions in human sweat and achieve accurate measurement. The patch can not only read the amount of sweat and chloride ion concentration in real time, but also support adjustment according to demand. This makes it show broad application prospects in the fields of real-time human motion monitoring and medical health testing, and can provide effective solutions for health management and disease monitoring.

[0030] (4) The technical solution provided by the present invention can effectively reduce the loss of solute mass and reduce the separation distance between the front end of the pigment and the front end of the liquid, thereby ensuring the flow distance of the pigment. This design helps to prevent the decrease in measurement accuracy, improves the reliability of the test results, and provides a more accurate solution for the analysis of biomarkers in sweat. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 : is a schematic diagram of the structure of the device of the present invention in Example 1 of the present invention;

[0032] Figure 2 : It is the result diagram of Example 2 in the present invention.

[0033] Figure 3 : It is the result diagram of Example 3 in the present invention.

[0034] Figure 4 : It is the result diagram of Example 4 in the present invention.

[0035] Figure 5 : It is the result diagram of Example 5 in the present invention.

[0036] Figure 6 : It is the result diagram of Example 6 in the present invention. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all.

[0038] Embodiment 1: The bottom of the sweat microfluidic patch structure is an adhesion layer, and a fan-shaped hole is cut out of the adhesion layer by laser as a liquid inlet; the adhesion layer is the microfluidic main layer, and the main layer structure is a special double-channel inverted trapezoidal structure, and two liquid inlet areas, a pigment area, a reagent area, a reference channel, and a reaction channel are arranged on the main layer, wherein the pigment solution needs to be dripped in the pigment area and printed on the filter paper in the reagent area; above the microfluidic main layer is the scale area, which is provided with a reference scale, a health reminder scale area and a sweat marker concentration scale; above the scale area is the encapsulation layer.

[0039] Example 2: The relationship between the change in RGB value of the trapezoidal dual-channel sweat microfluidic patch over time during long-term storage. Usually when making a sample chip, if the chip is not treated in any way, the sample chip will naturally turn black in less than a day, thus affecting the reading. In order to solve this problem, we adopted a water washing process. The specific process is: first, use an inkjet printer and a laser cutter to make the required chip structure. Then, prepare three beakers, place 50mL of deionized water in each beaker, and place the printed chip structure in the three beakers for water washing, and each washing time is not less than three minutes. After the water washing is completed, place the chip in a constant temperature drying oven and dry it for about five minutes. Finally, use a brown sealing bag to vacuum seal it and store it in a brown bottle to ensure long-term storage. In Figure 2 In the experiment, Adobe Photoshop was used to extract the values ​​of the three colors R (red), G (green), and B (blue), and the RGB values ​​of the same sample were measured at 10 different locations at 1, 3, 5, 7, 9, and 15 days. The results showed that the RGB value changes remained relatively stable, and the color of the sample also changed very slowly from the naked eye, indicating that the sample can be used for a long time without significant fading.

[0040] Example 3: Currently, in the research on paper-based chips for detecting chloride ions using silver titration, the usage time of the samples has not been directly mentioned. The experimental results show that most samples will turn black after more than one week on the surface of the reagent area, and the blackened chip will have a significant impact on the accurate reading of chloride ions. After washing with water, we vacuum-sealed the samples for storage. Figure 3 The validation experiment of the reagent zone is shown. The sealed treated samples were titrated at 1, 3, 5, 7, 9 and 15 days. Each experiment was repeated 10 mL of 60 mM chloride solution and the results showed that the reaction distance remained at 1 cm.

[0041] Example 4: The sweat microfluidic patch is fabricated by laser and structural design, so it has high scalability. We studied the performance of three structural channels with the same area: inverted trapezoidal, rectangular, and regular trapezoidal. Despite the different designs, the total surface area of ​​all channels remained exactly the same (Figure A = B = C = 61.25 cm 2 ) to allow for a valid comparison based solely on differences in channel geometry. The experimental results show that while the solvent (water) front reaches almost the end of all channel types, the dye front stops before reaching the end. This phenomenon is due to intermolecular interactions between the dye molecules and the paper surface, which causes the dye molecules to be adsorbed and retained on the paper. We can view this phenomenon as a distance-based detection model, where the paper surface acts as a deposited reactant and the dye is the analyte captured by the cellulose fibers. Figure 4 The time course of mass (dye) transport on different channel geometries is described. In the A-type dye, the dye front moves the longest distance despite the lower initial flow rate. Experiments using 10mL of dye solution ultimately show that the dye in the A-structure moves the farthest distance with a slower flow rate. This suggests that there is less paper surface area available to capture the dye at the beginning of the channel, so more free dye molecules are able to move a longer distance along the channel. Therefore, among the differently designed paper microfluidic channels with the same total surface area, the A-type provides the highest mass transfer. Compared to other traditional shapes, when using these structures, the dye stops flowing quickly, which has an impact on the distance-based detection of chloride ion concentration.

[0042] Example 5: There is a linear relationship between the amount of solution absorbed by the reference channel of the dual-channel sweat microfluidic patch and the distance. During the experiment, we added 5μL, 7μL, 10μL, 12μL, 15μL, 18μL and 20μL of deionized water respectively, and observed and measured the distance that the sweat pigment moved on the reference channel as the amount of solution increased. The experiment was repeated six times for each solution amount. By linearly fitting the data of solution amount (5μL to 18μL) and movement distance, the linear equation was obtained: y=0.0988x+0.24606(R 2 =0.9988), such as Figure 5 As shown. It can be seen that within this liquid volume range, there is a good linear relationship between the solution volume and the pigment movement distance. Therefore, we can reflect the sweat volume based on the movement distance of the liquid volume in the reference scale area.

[0043] Example 6: There is a linear relationship between the concentration of chloride ions absorbed and reacted by the reagent channel of the trapezoidal dual-channel microfluidic patch and the distance. In the experiment, we dripped 5μL, 7μL, 10μL, 12μL, 15μL and 18μL of 60mM chloride ion solution respectively, and observed and measured the length of the precipitation generated on the reagent channel. The experiment was repeated six times at each concentration point, and a linear fit was obtained between different solution amounts and the length of the generated precipitation. The linear equation obtained was y=0.1195x-0.3726(R 2 =0.9986). R 2 A value greater than 0.95 indicates a good linear fit, indicating that within the range of 5 μL to 18 μL, there is a linear relationship between the concentration of the 60 mM chloride ion solution and the length of the generated precipitation. In human sweat, when the chloride ion concentration is greater than 60 mM, the probability of suffering from cystic fibrosis increases significantly. Therefore, when the length of the generated precipitation is above the linear equation, it may indicate that the patient has cystic fibrosis; otherwise, the patient may not have the disease. The scale line of 60 mM chloride ion corresponds to the reference scale line on the left. When the reference scale where the front end of the left pigment is located is equal to the 60 mM chloride ion scale value where the front end of the silver chloride precipitation is located on the right, it indicates that the chloride ion concentration is 60 mM at this time; when the reference scale value of the front end of the left pigment is higher than the 60 mM scale value on the right, it indicates that the chloride ion concentration exceeds 60 mM, and the test subject is very likely to suffer from cystic fibrosis.

Claims

1. A trapezoidal paper-based microfluidic patch for sweat analysis and a preparation method thereof, characterized in that: include, 1) By testing some characteristic biological data contained in sweat; 2) Using a water washing process to obtain a microfluidic patch with a long service life; 3) obtaining characteristic physiological data related to the visualization scale of the trapezoidal microfluidic patch and processing them; 4) Establish a visualization standard model with sweat physiological data in low and high concentration detection range and microfluidic patch scale; 5) Perform performance testing and parameter optimization on the visualization model in 4).

2. A trapezoidal paper-based microfluidic patch for sweat analysis and a preparation method thereof according to claim 1, characterized in that: The sweat physiological data includes sweat volume and chloride ion concentration.

3. A trapezoidal paper-based visualized microfluidic patch according to claim 1, characterized in that: The physiological index is related to characteristic physiological data of the visualized scale of the trapezoidal microfluidic patch: the change of the scale of the microfluidic patch with the change of the sweat volume, and the change of the scale of the microfluidic patch with the change of the chloride ion concentration.

4. A trapezoidal paper-based microfluidic patch for sweat analysis and a method for preparing the same, characterized in that: The visualization standard model according to any one of claims 1 to 3 comprises: an adhesion layer (6), a microfluidic chip layer (5), a visualization scale layer (2) and a packaging layer (1); the microfluidic chip layer is one of a single-channel, dual-channel and multi-channel parallel structure, and is designed so that the adhesion layer (6), the microfluidic chip layer (5), the scale layer (2) and the packaging layer (1) are formed from bottom to top by a pressing method, the adhesion layer (1) comprises a liquid inlet (7), and the microfluidic chip layer comprises a reference / pigment channel (3) and a reagent channel (4).

5. A trapezoidal paper-based microfluidic patch for sweat analysis and a method for preparing the same, characterized in that; The microfluidic patch structure is one of a regular trapezoid, a traditional rectangle, and an inverted trapezoid.

6. A trapezoidal paper-based microfluidic patch for sweat analysis and a method for preparing the same, characterized in that: Trapezoidal channels (channel width varies linearly with height) are used to create a gradient of paper surface (titrant) available for reaction, compared to typical uniform rectangular channels (constant channel width). The trapezoidal shape provides higher sensitivity and lower detection limits for chloride determination in the concentration range of 0.05–25 mM.

7. A trapezoidal paper-based microfluidic patch for sweat analysis and a method for preparing the same, characterized in that: Titrations of different concentrations (AgNO3) were used, allowing chloride to be determined over a wider dynamic range (up to 150 mM).

8. A paper-based visualized microfluidic patch trapezoidal paper-based microfluidic patch sweat analysis and a preparation method thereof according to claim 4 or 5, characterized in that: The adhesion layer of the model is provided with a fan-shaped liquid inlet; the microfluidic chip layer is provided with a liquid inlet area, a reference scale area, a printing reagent area, a reference channel and a reaction channel: the liquid inlet area is located directly above the fan-shaped liquid inlet of the adhesion layer; the reference scale area and the printing reagent area are divided and independent of the two sides of the liquid inlet; the reference channel is located in the reference scale area and connected to the liquid inlet area; one end of the printing reagent area is connected to the liquid inlet area, and the other end is located in the reaction channel.

9. A trapezoidal paper-based microfluidic patch for sweat analysis and a method for preparing the same according to claim 7, characterized in that: The scale layer is provided with a reference scale, a health reminder scale area and a marker concentration scale area; the reference scale is located on one side of the reference channel, the marker concentration scale is located on one side of the reaction channel, and the health reminder scale is located between the reference scale and the marker concentration scale.

10. A trapezoidal paper-based microfluidic patch for sweat analysis and a method for preparing the same according to claims 4-9, characterized in that: include: The detection reagents are respectively injected into the reagent area of ​​the microfluidic main layer, and then washed and dried, and finally packaged to obtain the model.

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