Sweat detection device based on one-way drainage composite paper-based fiber membrane and preparation method thereof

Abstract

The application discloses a sweat detection device based on one-way liquid discharge composite paper-based fiber membrane and a preparation method, and relates to the technical field of sweat detection. The preparation method is as follows: SEBS is dissolved and then added into LiCl aqueous solution to prepare an electrospinning liquid, and the composite paper-based fiber membrane is prepared on a hydrophilic paper base layer through electrospinning; a microfluidic channel is written on the hydrophilic side of the composite paper-based fiber membrane; a bromocresol green aqueous solution is added into the microfluidic channel and dried to obtain a pH detection module; a mixed solution of ferric chloride and potassium ferricyanide is added into the microfluidic channel, a mixed solution of chitosan and sodium alginate is added after drying, and lactic acid oxidase or glucose oxidase is added, and a color developing agent is added after drying to obtain a lactic acid detection module and a glucose detection module respectively; the detection device has the characteristics of simple structure, convenient operation, high detection accuracy and good color developing effect, and can realize colorimetric detection of pH, lactic acid and glucose without cross interference.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sweat detection, in particular to a sweat detection device based on one-way liquid discharge composite paper-based fiber membrane and a preparation method. BACKGROUND

[0002] Sweat biomarker detection mainly relies on electrochemical sensors or microfluidic chips. Electrochemical sensors need to integrate electrodes and circuits, which are high in cost and difficult to be flexibly attached to the skin. Microfluidic chips can precisely control the flow and collection of sweat, avoid external environmental pollution of sweat, and achieve high-precision biomarker detection, so they occupy a very important position in wearable sensor sweat sampling.

[0003] The existing sweat detection microfluidic chip has the following shortcomings.

[0004] 1. Liquid is prone to backflow, and cross talk occurs in different reaction zones during multi-index synchronous detection.

[0005] 2. The substrates are mostly polydimethylsiloxane (PDMS), paper-based, polyurethane (PU), etc. Among them, PDMS lacks air permeability, which reduces the comfort of the user, causes sweat accumulation, and affects the detection results. In addition, expensive equipment and complex molding conditions are required during preparation, which has the disadvantages of complex preparation process and high cost; the fiber membrane prepared by electrospinning of PU solves the defect of poor air permeability of the PDMS substrate, but its wettability is single and it has hydrophobic properties. When collecting sweat samples, there is a natural macroscopic lyophobic force against sweat, which affects the flow of the liquid and the absorption of the sample by the detection area; paper-based materials have the advantages of easy availability of raw materials, simple preparation process, good air permeability, and high skin adhesion, so they are promising as detection substrates for sweat sensors.

[0006] However, on the one hand, the hydrophilic paper-based material is prone to adhesion to the skin, causing new and old sweat to accumulate at the junction between the paper-based material and the skin, affecting the detection results; on the other hand, the single-side hydrophobic modification of the paper-based material also requires a relatively complex operation and easily loses the advantage of good air permeability of the paper-based material; using hydrophobic electrospun micro-nano fibers to modify one side of the paper-based material is a convenient and effective method that can retain the advantages of air permeability and softness of the paper-based material while inhibiting the accumulation of sweat on the skin surface and enhancing the adhesion to the skin.

[0007] In addition, due to the differences in chain flexibility, polarity-interface interaction, and stress release capacity between the paper-based material and most elastomer materials, the stress between the two layers of fiber membranes (i.e., paper-based fibers and electrospun fibers) does not match, causing delamination of the composite fiber membrane, rupture of the membrane surface, and other problems, so the selection of hydrophobic fibers and the optimization of the preparation process are also required.

[0008] 3. Fluorescence colorimetric method, poor light stability, and needs to rely on professional spectrometer for analysis, high equipment cost, and complex operation. SUMMARY

[0009] The present application is to solve the technical problems of the existing sweat detection microfluidic chip, such as easy backflow of liquid, easy cross-talk in different reaction zones during multi-index synchronous detection, poor air permeability of the substrate, poor comfort, easy delamination of the multi-layer structure, and poor color development stability, and aims to provide a sweat detection device based on one-way liquid discharge composite paper-based fiber membrane and a preparation method, which has the characteristics of simple structure, convenient operation, strong bonding force between the SEBS fiber membrane and the hydrophilic paper base layer, and good color development effect.

[0010] The present application is realized by the following technical solutions.

[0011] The first object of the present application is to provide a preparation method of a sweat detection device based on one-way liquid discharge composite paper-based fiber membrane, comprising the following steps:

[0012] Dissolve SEBS in a mixed solvent of tetrahydrofuran and n-heptane, add LiCl aqueous solution, and prepare an electrospinning solution. A composite paper-based fiber membrane is prepared on one side of the hydrophilic paper base layer by electrospinning for 3-4 hours.

[0013] Write a plurality of hydrophobic microfluidic channels on the other side of the hydrophilic paper base layer of the composite paper-based fiber membrane;

[0014] Add bromocresol green aqueous solution to the hydrophobic microfluidic channel and dry to obtain a pH detection module;

[0015] Add a mixed solution of ferric chloride and potassium ferricyanide to the hydrophobic microfluidic channel, dry, add a mixed solution of chitosan and sodium alginate, and then add lactic acid oxidase or glucose oxidase. Dry and add a color developing agent to obtain a lactic acid detection module and a glucose detection module, respectively.

[0016] The present application uses a hydrophilic paper base layer as a substrate, which is easy to obtain, has good air permeability, and has high skin fit, thereby improving the comfort of the user. A layer of hydrophobic SEBS fiber membrane is prepared on it by the method of electrospinning, thereby forming a composite paper-based fiber membrane with one-way liquid guiding function. The experiment shows that the composite paper-based fiber membrane has good anti-gravity one-way liquid guiding performance. The one-way directional flow structure eliminates the backflow of sweat, avoids the pollution of the detection area, and ensures the accuracy of the detection result. At the same time, the hydrophobic SEBS fiber membrane has strong bonding force with the hydrophilic paper base layer, good stability, and is not easy to delaminate and break.

[0017] The present application writes a plurality of hydrophobic microfluidic channels on the hydrophilic side of the composite paper-based fiber membrane, which can simultaneously realize colorimetric detection of pH, lactic acid and glucose, and avoid detection result crosstalk caused by sweat sample flow.

[0018] In the preparation of the lactic acid detection module and the glucose detection module, a Prussian blue-developing agent-oxidase cascade colorimetric system is established, and lactic acid oxidase / glucose oxidase can specifically catalyze the conversion of lactic acid / glucose into H2O2, and Prussian blue (PB) particles can catalyze the color development of developing agents (such as TMB) to produce color changes in the presence of H2O2, thereby realizing quantitative analysis of lactic acid / glucose.

[0019] In the preparation process of the lactic acid detection module and the glucose detection module, the detection area is modified by using a chitosan solution and a sodium alginate solution, the cationic amino group of chitosan and the anionic carboxyl group of sodium alginate have electrostatic crosslinking effect, and a stable hydrogen bond network is formed through the synergistic effect of amino and carboxyl groups, providing rich hydrogen bond sites for enzymes to provide more attachment sites, at the same time, chitosan and sodium alginate form a nanoscale polyelectrolyte composite film on the surface of paper fibers through electrostatic layer-by-layer self-assembly, which "cages" the color developing molecules in the three-dimensional network pores through multiple point hydrogen bonds, van der Waals forces and physical entanglement, inhibits the driving force of capillary pumping and solute convection of the sweat front, anchors and does not migrate with the liquid flow, realizes uniform fixation of the color developing agent, shortens the reaction equilibrium time, and improves the color developing effect.

[0020] Further, the concentration of hydrogenated styrene-butadiene block copolymer (SEBS) in the mixed solvent is 10-14wt%, specifically, the concentration can be selected as 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, preferably 12wt%.

[0021] Further, the solute mass of the LiCl aqueous solution is 1-2%, and the volume ratio of the LiCl aqueous solution to the electrospinning solution is (0.5-1.5):100, and as preferred, the solute mass of the LiCl aqueous solution is 1%, and the volume ratio of the LiCl aqueous solution to the electrospinning solution is 1:100.

[0022] Further, the hydrophobic microfluidic channel writing adopts hydrophobic rosin ink. Among the many methods of constructing microfluidic channels on paper substrates, the commonly used method is to use PDMS ink to prepare microfluidic channels, but it requires complex preparation process (ratio and high temperature forming, etc.) and high cost (material cost and process cost). The method of the present application directly writes and prepares microfluidic channels by using rosin-based ink, and by reasonably adjusting the ratio of rosin solution and optimizing the writing parameters, it can construct microfluidic patterns on various paper bases with high precision. It has the advantages of simple operation, high precision and strong universality. Moreover, this method does not require professional skills from the operator, and can be used with only inexpensive materials. It is widely used and has high precision. It can be easily automated and mass-produced by loading the hydrophobic rosin ink into a writing machine, a dispensing machine, a 3D printer or other instruments, and has good universality.

[0023] Further, the hydrophobic rosin ink is prepared by dissolving rosin in ethanol with a concentration of 0.5-0.7 g / mL, and the preferred rosin concentration is 0.6 g / mL.

[0024] Further, the writing speed is 550-650 mm / min, and the preferred writing speed is 600 mm / min, and the writing frequency is 3 times.

[0025] Further, the mass ratio of ferric chloride and potassium ferricyanide is 1: (1.5-2.5), and the preferred mass ratio of the two is 1:2.

[0026] Further, the mass ratio of chitosan and sodium alginate is (1-2):(1-2), and the preferred mass ratio of the two is 1:1.

[0027] Further, in the preparation process of the lactic acid detection module, after adding the color developing agent, the dipotassium hydrogen phosphate and potassium dihydrogen phosphate buffer solution are added. The dipotassium hydrogen phosphate and potassium dihydrogen phosphate buffer solution has pH buffering capacity, which can stabilize the local microenvironment and avoid the interference of the paper base acidity and alkalinity fluctuation on the color developing signal, thereby ensuring the color developing effect.

[0028] The second object of the present application is to provide a sweat detection device based on a one-way drainage composite paper base fiber membrane, which is prepared by the above-mentioned method. The structure of the sweat detection device comprises:

[0029] A hydrophilic paper base layer;

[0030] A hydrophobic SEBS fiber membrane is arranged on one side of the hydrophilic paper base layer;

[0031] A plurality of hydrophobic microfluidic channels are arranged on the other side of the hydrophilic paper base layer;

[0032] The hydrophobic microfluidic channel comprises a pH detection module, a lactic acid detection module and a glucose detection module.

[0033] Compared with the prior art, the present application has the following advantages and beneficial effects.

[0034] 1. The present application adopts a hydrophilic paper base layer as a substrate, the raw material is easy to obtain, has good air permeability and high skin adhesion, improving the comfort of the user, and a layer of hydrophobic SEBS fiber membrane is prepared on it by the electrospinning method, thereby forming a composite paper base fiber membrane with unidirectional liquid guiding function, and the experiment measures that the composite paper base fiber membrane has good anti-gravity unidirectional liquid guiding performance, the unidirectional directional flow guiding structure eliminates the backflow of sweat, avoids the pollution of the detection area, guarantees the accuracy of the detection result, at the same time, the chitosan and sodium alginate are self-assembled on the surface of the paper fiber through the electrostatic layer to form a nanoscale polyelectrolyte composite membrane, the membrane locks the color developing molecules in the three-dimensional network pores through multiple point hydrogen bonds, van der Waals forces and physical entanglement, inhibits the driving force of the capillary pumping and solute convection of the sweat front, anchors the color developing molecules to prevent them from migrating with the liquid flow, realizes the uniform fixation of the color developing agent, shortens the reaction equilibrium time and improves the color developing effect.

[0035] 2. A plurality of hydrophobic microfluidic channels are written on the hydrophilic side of the composite paper base fiber membrane, so that the colorimetric detection of pH, lactic acid and glucose can be realized at the same time, and the detection result crosstalk caused by the flow of the sweat sample is avoided.

[0036] 3. In the preparation of the lactic acid detection module and the glucose detection module, a Prussian blue-color developing agent-oxidase cascade colorimetric system is established, and lactic acid oxidase / glucose oxidase can specifically catalyze the conversion of lactic acid / glucose into H2O2, and Prussian blue (PB) particles can catalyze the color developing agent (such as TMB) to develop color and produce color change in the presence of H2O2, thereby realizing the quantitative analysis of lactic acid / glucose.

[0037] 4. In the preparation process of the lactic acid detection module and the glucose detection module, the detection area is modified by using chitosan solution and sodium alginate solution, the cationic amino group of chitosan and the anionic carboxyl group of sodium alginate have electrostatic crosslinking effect, and a stable hydrogen bond network is formed through the synergistic effect of amino and carboxyl groups, providing rich hydrogen bond sites for enzymes to provide more attachment sites, at the same time, the color developing agent can be uniformly fixed and not migrate with the sweat flow, the reaction equilibrium time is shortened, the display stability is improved, in addition, the chitosan solution and the sodium alginate solution also have pH buffering capacity, which can stabilize the local microenvironment and avoid the interference of the fluctuation of the acid-base degree of the paper base on the color developing signal, thereby guaranteeing the color developing effect. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present application, the drawings required to be used in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be considered as a limitation to the scope. Other related drawings can also be obtained by those skilled in the art without any creative effort, based on the drawings. In the drawings:

[0039] Figure 1 Structure diagram of the sweat detection device of the present application;

[0040] Figure 2 pH detection standard curve of the present application;

[0041] Figure 3 Glucose detection standard curve of the present application;

[0042] Figure 4 Lactic acid detection standard curve of the present application;

[0043] Figure 5 Glucose standard curve without adding chitosan solution and sodium alginate solution;

[0044] Figure 6 Lactic acid standard curve without adding chitosan solution and sodium alginate solution;

[0045] Figure 7 Pearson coefficient evaluation results of the pH detection module of the present application and the conventional method;

[0046] Figure 8 Pearson coefficient evaluation results of the glucose detection module of the present application and the conventional method;

[0047] Figure 9 Pearson coefficient evaluation results of the lactic acid detection module of the present application and the conventional method;

[0048] Figure 10 Wettability characterization results of the hydrophilic paper base (filter paper), single-layer hydrophobic layer SEBS fiber membrane, and the composite fiber membrane of the present application;

[0049] Figure 11 Anti-gravity one-way liquid guiding performance results of the composite paper base fiber membrane of the present application;

[0050] Figure 12 Anti-gravity air permeability evaluation results of the composite paper base fiber membrane of the present application;

[0051] Figure 13 Results of the difference in liquid volume and the difference in hydrostatic pressure of the composite paper base fiber membrane with SEBS deposited for different time.

[0052] Markings in the drawings and corresponding names of parts:

[0053] 1-hydrophobic SEBS fiber membrane, 2-hydrophilic paper-based layer, 3-microfluidic channel, 4-pH detection module, 5-lactic acid detection module, 6-glucose detection module. DETAILED DESCRIPTION

[0054] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the embodiments and drawings. Obviously, the illustrative embodiments of the present application and their descriptions are only used to explain the present application and should not be regarded as a limitation to the present application.

[0055] The embodiments of the present application of a sweat detection device based on one-way drainage composite paper-based fiber membrane and a preparation method will be described in detail below with appropriate reference to the drawings. However, there will be cases where unnecessary detailed descriptions are omitted. For example, there will be cases where detailed descriptions of matters that are well known and repeated descriptions are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0056] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can include or not include the end value, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range.

[0057] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0058] If not specifically stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0059] If not specifically stated, the "includes" and "contains" mentioned in the present application mean open-ended, and can also be closed. For example, the "includes" and "contains" can mean that other substances not listed can also be included or contained, or only the listed substances can be included or contained.

[0060] If not otherwise specified, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0061] The technical solutions of the present application are further described in detail below in combination with examples.

[0062] It should be noted that the experimental methods used in the examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained by commercial channels by those skilled in the art.

[0063] Example 1

[0064] A sweat detection device based on one-way drainage composite paper-based fiber membrane, the structure is as follows Figure 1 The device comprises:

[0065] A hydrophilic paper-based layer 2;

[0066] A hydrophobic SEBS fiber membrane 1 is arranged on the bottom surface of the hydrophilic paper-based layer 2 by electrospinning method;

[0067] A plurality of hydrophobic microfluidic channels 3 are formed on the top surface of the hydrophilic paper-based layer 2 by direct writing method to form three circular hydrophobic microfluidic channels 3 with a diameter of 5 mm;

[0068] Among them, three circular hydrophobic microfluidic channels 3 are respectively added with components for detecting biological markers such as pH, lactic acid and glucose, thereby forming a pH detection module 4, a lactic acid detection module 5 and a glucose detection module 6.

[0069] It should be noted that the number of microfluidic channels 3 of the present application is not limited to three, and can be set as needed.

[0070] Detection principle:

[0071] The chromogenic agent in the pH detection module 4 is bromocresol green, and the chromogenic agent in the lactic acid detection module 5 and the glucose detection module 6 is tetramethyl benzidine (TMB). The microfluidic channel is arranged to define a plurality of detection areas, which is conducive to forming a closed microcavity on the paper base and strictly limiting the colorimetric reaction in the preset geometric area. The significance lies in that, on the one hand, the sample is uniformly spread on the fixed reaction surface by utilizing the capillary pumping effect, so as to eliminate the signal drift caused by edge diffusion and liquid accumulation; on the other hand, the different analysis areas are physically isolated to avoid cross contamination, so that the color intensity and the target concentration have a reproducible linear relationship, and portable, single-point or multiple quantitative detection is realized.

[0072] The detection device of the present application is based on the Janus structure and is conducive to the upward flow of excess sweat. At the same time, according to the needs, the reasonable design of the hydrophilic side microfluidic channel and the preparation method of the microfluidic channel of the present application can be combined to guide the sweat that seeps from the skin surface on the hydrophilic side of the paper base to flow into a specific sweat evaporation area, so as to discharge excess sweat, reduce the humidity at the skin interface and improve the comfort, and also improve the accuracy of detection.

[0073] The hydrophobic SEBS fiber membrane 1 and the hydrophilic paper base layer 2 form a composite paper base fiber membrane, which has an asymmetric wetting interface. The sweat secreted from the skin surface flows through the SEBS layer close to the skin side to the hydrophilic paper base layer, avoiding the accumulation of sweat at the interface between the skin and the device. The air permeability of the device also improves the comfort. After the sweat reaches the hydrophilic paper base layer, it flows into three colorimetric detection areas. Due to the existence of the hydrophobic boundary of the microfluidic channel 3, it will not exude, realizing the synchronous detection of three biomarkers with high stability and high sensitivity.

[0074] During detection, the colorimetric method is used for detection. The sample to be detected is added to the corresponding detection module. After the color is stable, it is placed in a black box. An image acquisition device such as a smart phone is used to acquire images of the detection area under a color temperature of 6500K. Then the RGB value is obtained for analysis, realizing the health supervision of the user. The operation is simple and does not require complex and expensive precision instruments.

[0075] Compared with the electrochemical method of the conventional sweat sensor, the device of the present application does not need to prepare a complex electrode circuit, is easy to use, can be judged by the naked eye, or can realize the collection and analysis of the sample by using a common and easily available mobile phone. Compared with the fluorescence colorimetric method, the cost is more low, and expensive instruments (enzyme-labeled instrument, ultraviolet spectrophotometer, etc. optical instrument) are not needed for analysis, the professional requirements for the user are low, and the operation is more simple.

[0076] Example 2

[0077] A preparation method of a sweat detection device based on a one-way liquid discharge composite paper base fiber membrane, comprising the following steps:

[0078] (1) Preparation of composite paper-based fiber membrane

[0079] SEBS was used as a solute, and tetrahydrofuran: n-heptane (8:2) was used as a solvent to prepare a co-electrospinning solution, wherein the concentration of SEBS was 12 wt%, and 1% LiCl solution was further added, and the volume ratio of LiCl aqueous solution to the electrospinning solution was 1:100;

[0080] The prepared electrospinning solution was electrospun on Whatman No.2 filter paper under the conditions of a voltage of 18 KV, a receiving distance of 15 cm, a relative humidity of 40%, and a pushing speed of 1 mL / h for 3 h to prepare the composite paper-based fiber membrane.

[0081] (2) Preparation of hydrophobic rosin microfluidic channel

[0082] Rosin was dissolved in ethanol to prepare a hydrophobic rosin ink with a concentration of 0.6 g / ml, the ink was filled into the writing pen core, and a φ5 mm circular hydrophobic microfluidic channel was written on the hydrophilic paper base of the composite paper-based fiber membrane at a speed of 600 mm / min by using a direct writing method, the multi-index detection area was separated from each other by preparing a colorimetric detection area in the written φ5 mm circular area, and synchronous detection was realized without cross talk.

[0083] (3) Preparation of the pH detection part in sweat

[0084] 5 μL of standard bromocresol green aqueous solution with a concentration of 1 mg / mL was added dropwise into the pH detection area, and was dried at 40°C to complete the preparation, and was stored in a 4°C refrigerator after the preparation was completed;

[0085] The bromocresol green used in the application is a common acid-base indicator for detecting the pH in sweat.

[0086] (4) Preparation of the lactic acid detection part in sweat

[0087] 5 mM ferric chloride solution and 5 mM potassium ferricyanide solution were mixed uniformly, and 10 μL of the mixture was quickly added to the lactic acid detection area, and was naturally dried and placed overnight to ensure that Prussian blue (PB) particles were successfully prepared in situ in the detection area; then, 1 mg / mL chitosan solution and 1 mg / mL sodium alginate solution were added to the detection area, 4 μL of lactic acid oxidase was further added, and after drying, 1 wt% TMB was added as a color developing agent;

[0088] To avoid the rapid entry of lactic acid leading to rapid pH change and enzyme inactivation, 7 pH buffer solution of dipotassium hydrogen phosphate and potassium dihydrogen phosphate was further added and dried, and was stored in a 4°C refrigerator after the preparation was completed.

[0089] (5) Preparation of glucose detection part in sweat

[0090] A 5 mM ferric chloride solution was mixed with a 5 mM potassium ferricyanide solution, which was quickly added dropwise to the detection area of lactic acid at 10 μL, and after natural drying, it was placed overnight to ensure the successful preparation of Prussian blue (PB) particles in situ in the detection area. Then 1 mg / mL chitosan solution and 1 mg / mL sodium alginate solution were added to the detection area, followed by the addition of 4 μL glucose oxidase, and after drying, 1 wt% TMB was added as a color developing agent. After drying, the preparation was stored in a 4°C refrigerator.

[0091] The principle of lactic acid detection is consistent with that of glucose detection. Since PB nanoparticles can catalyze the oxidation of color developing substrates (such as TMB) in the presence of H2O2, through this principle, PB and lactic acid oxidase / glucose oxidase can be used to detect lactic acid / glucose in an enzyme-linked reaction:

[0092] Glucose oxidase can specifically catalyze the conversion of glucose to H2O2, and lactic acid oxidase can specifically catalyze the conversion of lactic acid to H2O2. At this time, PB nanoparticles catalyze the color development of TMB to produce color changes in the presence of H2O2, thereby realizing the quantitative analysis of lactic acid / glucose.

[0093] (6) Establishment of detection standard curve

[0094] For the pH detection part: 3.7, 4.4, 5.1, 5.8, 6.5, 7.2, and 7.9 sample liquids were added dropwise in sequence, and reacted for 10 min. After the color was stable, it was placed in a black box, and an image of the detection area was collected using a smartphone under a color temperature of 6500K. The RGB values were then obtained for analysis. The above operations were repeated three times. The results, as shown in Figure 2 , indicate that this pH colorimetric sensor part has good detection linearity;

[0095] For the glucose detection part: 100 μM-500 μM glucose sample liquids were added dropwise in sequence, and reacted for 10 min. After the color was stable, it was placed in a black box, and an image of the detection area was collected using a smartphone under a color temperature of 6500K. The RGB values were then obtained for analysis. The above operations were repeated three times. The results, as shown in Figure 3 , indicate that this glucose colorimetric sensor part has good detection linearity;

[0096] For the lactic acid detection part: sequentially add sample liquids with lactic acid concentrations of 5 mM-60 mM, react for 10 min, place the color-stable colorimetric detection area in a black box, and use a smartphone to collect images of the detection area under a color temperature of 6500K, then obtain the RGB values for analysis, and repeat the above operations three times. The results are shown in FIG. 6A. Figure 4 As shown in FIG. 6B, it is illustrated that the lactic acid colorimetric detection part has good detection linearity.

[0097] Comparative Example 1

[0098] The difference between this comparative example and Example 2 is that no chitosan solution and sodium alginate solution are added during the preparation of the lactic acid and glucose detection parts. The standard curve is established by the methods in (2) and (3) of Experimental Example 4.

[0099] As shown in FIG. 7A, it is the glucose standard curve without adding chitosan solution and sodium alginate solution. Figure 5 As shown in FIG. 7B, it is the glucose standard curve with adding chitosan solution and sodium alginate solution. Figure 5 Figure 3 As can be seen from the comparison between FIG. 7A and FIG. 7B, the goodness of fit R 2 of the glucose standard curve with adding chitosan solution and sodium alginate solution reaches 0.9928, while the goodness of fit R 2 of the glucose standard curve without adding chitosan solution and sodium alginate solution is only 0.97081.

[0100] As shown in FIG. 8A, it is the lactic acid standard curve without adding chitosan solution and sodium alginate solution. Figure 6 As shown in FIG. 8B, it is the lactic acid standard curve with adding chitosan solution and sodium alginate solution. Figure 6 Figure 4 As can be seen from the comparison between FIG. 8A and FIG. 8B, the goodness of fit R 2 of the lactic acid standard curve with adding chitosan solution and sodium alginate solution reaches 0.99322, while the goodness of fit R 2 of the lactic acid standard curve without adding chitosan solution and sodium alginate solution is only 0.73647.

[0101] In summary, the higher the R 2 value, the better the fitting effect of the model on the data, and the more sufficient the relationship between the biomarkers and the detection results can be explained. Therefore, in the colorimetric sensing area part of glucose and lactic acid, after adding chitosan and sodium alginate for modification, the goodness of fit R 2 is significantly improved and is closer to 1, indicating that the modified colorimetric group has a better color development effect.

[0102] The following are performance evaluation experiments of the composite paper-based fiber membrane and detection device of the present application.

[0103] Experimental Example 1

[0104] The accuracy of the detection standard curve in Example 2 above is evaluated. ​​

[0105] For the pH detection part: the artificial sweat is added in the detection area, the measured result is consistent with the result measured by the traditional method pH meter, and the evaluation result is the Pearson coefficient curve in the drawing Figure 7 As shown, the Pearson coefficient is 0.99397, indicating that the sensor has good consistency with the traditional detection method.

[0106] For the glucose detection part: the artificial sweat is added in the detection area, the measured result is consistent with the result measured by the traditional method glucose colorimetric kit, and the evaluation result is the Pearson coefficient curve in the drawing Figure 8 As shown, the Pearson coefficient is 0.99946, indicating that the sensor has good consistency with the traditional detection method.

[0107] For the lactic acid detection part: the artificial sweat is added in the detection area, the measured result is consistent with the result measured by the traditional method lactic acid colorimetric kit, and the evaluation result is the Pearson coefficient curve in the drawing Figure 9 As shown, the Pearson coefficient is 0.99717, indicating that the sensor has good consistency with the traditional detection method.

[0108] The Pearson coefficient is a statistical quantity used to measure the degree of linear correlation between two variables. Its value is between-1 and 1, and the absolute value of the Pearson coefficient is closer to 1, indicating that the linear relationship between the two variables is stronger. The Pearson coefficient is greater than 0.99, indicating that there is a strong linear correlation between the detection results of the new method and the old method, and the detection results of the two methods have high consistency.

[0109] Therefore, according to Figure 7 、 8 , the results of the present application show that the detection method has high consistency with the detection results of the traditional detection method (pH meter, glucose colorimetric kit, lactic acid colorimetric kit), indicating that the detection accuracy of the method is high, and compared with the traditional method, the method has the advantages of simple operation.

[0110] Experimental Example 2

[0111] The unidirectional liquid guiding effect of the composite paper-based fiber membrane is evaluated.

[0112] (1) Wetting analysis of the composite paper-based fiber membrane

[0113] For hydrophilic paper-based (filter paper) and single-layer hydrophobic SEBS fiber membranes, dynamic water contact angle (WAC) tests were performed by dropping 5 μL of deionized water onto the surface of the fiber membrane using a contact angle meter. For the composite paper-based fiber membrane of the present invention, dynamic water contact angle (WAC) tests were performed by dropping 5 μL of deionized water onto the surface of the hydrophobic SEBS side of the composite fiber membrane using a contact angle meter.

[0114] The results are as follows Figure 10 As shown, the water contact angle of the paper-based material is 45° at 0 s after contact with water, and it becomes 0° within 0.4 s, exhibiting very strong hydrophilicity; the water contact angle of the SEBS fiber membrane remains basically unchanged within 60 s and remains at around 118°, exhibiting a clear hydrophobic state; the initial water contact angle of the composite paper-based fiber membrane prepared in this invention is 120°, and the time required for its water contact angle to decrease to 90° is 1.26 s, at which point its water contact angle is 84.5°, and the time required for its water contact angle to decrease to 0° is 2.1 s.

[0115] (2) Characterization of antigravity unidirectional liquid guiding performance of composite paper-based fiber membrane

[0116] The composite paper-based fiber membrane of the present invention is cut into 18 mm × 6 mm test strips, and fixed horizontally to a glass slide support with the SEBS hydrophobic layer facing down to form a suspended test position. A 21G flat-tipped needle is connected to a micro-injection pump through a dispensing tube, with the needle vertically aligned below the test strip, and artificial sweat containing 1 wt% sodium fluorescein is pumped in (1.5 μL per injection).

[0117] Under ultraviolet excitation, the permeation trajectory of fluorescent droplets within the fiber membrane is captured in real time using a high-definition camera, enabling visual analysis. The results are as follows: Figure 11 As shown, the liquid begins to wet the composite paper-based fiber membrane at 0.11s, and the droplets are completely absorbed by the hydrophilic layer after passing through the hydrophobic layer at 6.83s, demonstrating its excellent anti-gravity unidirectional liquid guiding performance.

[0118] Experimental Example 3

[0119] Evaluation of the air permeability of the composite paper-based fiber membrane of the present invention.

[0120] Centrifuge tubes with 12 cm inside 3 CaCl2 desiccant was placed open as a blank control group. Composite paper-based fiber membrane, filter paper, SEBS, cotton fabric, commercial sports fabric, PU, ​​and PDMS were each cut into φ15 mm discs and sealed to the opening of centrifuge tubes containing desiccant. The weight increment of each group was recorded daily to evaluate gas permeability. Results are attached. Figure 12As shown, the air permeability of the device is close to that of traditional cotton fabric and commercial sports fabric, and is also close to that of the blank control group, indicating good air permeability.

[0121] The following is a screening experiment of the preparation conditions of the detection device of the application.

[0122] Experimental Example 4

[0123] In order to prove the technical effect of the composite paper-based fiber membrane of the application, the SEBS in the composite paper-based fiber membrane is replaced with PU, polystyrene (PS), polylactic acid (PLA), and polycaprolactone (PCL) to prepare a composite paper-based fiber membrane, and the combination of different hydrophobic membrane layers and paper bases is evaluated, and the results are shown in Table 1.

[0124] Table 1, combination of different hydrophobic membrane layers and paper bases

[0125]

[0126] Experimental Example 5

[0127] Preparation condition screening of the composite paper-based fiber membrane.

[0128] Since the thickness of the SEBS layer in the prepared composite paper-based fiber membrane has an important influence on the one-way effect of the droplet, the thickness of the hydrophobic fiber layer determines whether it can form a continuous "capillary cutoff valve" at the paper base pore. If it is too thin, the fiber cannot completely bridge the micron pores of the paper base, and the droplet can still pass through the uncovered pores and reverse seepage. If it is too thick, the fiber layer itself forms a continuous and dense network, and the overall hydrophobicity is too high, and the droplet is completely blocked and cannot penetrate in a directional manner. At the optimal thickness, the fiber layer can form a local hydrophobic barrier on the surface of the paper base, while retaining a small amount of pores that are not completely closed, so that an asymmetric capillary pressure difference is generated on both sides of the liquid surface, thereby realizing the one-way outward drainage function from the hydrophilic paper base to the hydrophobic surface. Therefore, the thickness of the SEBS layer in the prepared composite paper-based fiber membrane needs to be explored, and the optimal SEBS layer thickness of the composite paper-based fiber membrane that has both one-way liquid guiding performance and prevents reverse seepage of liquid is screened. Therefore, the inventors prepared composite paper-based fiber membranes with different hydrophobic layer thicknesses by electrospinning the SEBS layer for 1-10 h, and screened them by means of wettability characterization, anti-gravity one-way liquid guiding performance characterization, area quantitative analysis of one-way liquid guiding capacity, and hydrostatic pressure characterization. Through result analysis, the optimal preparation and deposition time of the electrospun SEBS layer is 3 h.

[0129] The greater the difference in hydrostatic pressure, the stronger the one-way water transport performance of the Janus membrane, that is, the membrane can more effectively prevent the reverse penetration of liquid from the hydrophilic side to the hydrophobic side, thereby exhibiting more excellent asymmetric permeation characteristics. Therefore, the greater the difference in hydrostatic pressure, the more excellent the one-way water transport performance of the Janus membrane; on the contrary, a smaller difference indicates insufficient one-way water transport capacity.

[0130] The hydrostatic pressure of the fiber membrane is tested by using a hydrostatic pressure testing device, and the results of the liquid bearing volume difference and the hydrostatic pressure difference of the composite paper-based fiber membrane of SEBS deposited for different times are shown in Figure 13 It can be seen from Figure 13 that when the electrospinning time of the SEBS layer is 3h, the liquid bearing difference and the hydrostatic pressure difference are the largest, indicating that the unidirectional water transport performance of the paper-based composite fiber membrane prepared under this condition is excellent, therefore, the optimal preparation deposition time of the electrospinning SEBS layer of the present application is 3h.

[0131] Experimental Example 6

[0132] Preparation condition screening of microfluidic channel.

[0133] The inventors explored the concentration of the main component of hydrophobic rosin ink, which is rosin, and configured its concentration to be 0.4 g / mL to 1 g / mL. They drew a hydrophobic circle area on paper-based by writing five times at a low writing speed (150 mm / min), and added ordinary ink in it. The selection was carried out by the ink infiltration. Next, by writing dumbbell-shaped channels with a diameter of 1 mm, the writing speed (150 mm / min to 1200 mm / min) and the writing number (1-5 times) were selected. When the writing speed is slow, the ink has more time to form a uniform layer on the surface of the paper, which helps to improve the waterproof effect. On the contrary, if the writing speed is too fast, the ink may not be able to fully penetrate into the paper fibers, and the formed layer may not be uniform enough, thus weakening the waterproof effect. In addition, fast writing may cause the pattern formed by the ink on the paper to have unclear and uneven edges, further affecting the waterproof effect, leading to channel blockage or liquid leakage. When the rosin ink is written with different numbers of times for the same pattern, the waterproof effect may be different. This is because each writing will add a new resin layer on the original rosin resin film, gradually increasing the thickness and density of the film. With the increase of writing times, the film becomes more compact and firm, thus improving the waterproof effect.

[0134] Therefore, the optimal writing speed of the present application is 600 mm / min, the writing number is 3 times, and the optimal concentration of rosin in the ink is 0.6 g / mL.

[0135] Finally, it should be noted that the above specific examples are only used to explain the purposes, technical solutions and beneficial effects of the present application in detail, and it should be understood that the above description is only a specific embodiment of the present application and does not limit the protection scope of the present application; although the present application has been described in detail with reference to the foregoing specific embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement, improvement, etc. to part or all of the technical features; and these modifications, equivalent replacement, improvement do not make the essence of the corresponding technical solution deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and description of the present application.

Claims

1. A method for preparing a sweat detection device based on a unidirectional drainage composite paper-based fibrous membrane, characterized in that, The method comprises the following steps: SEBS is dissolved in a mixed solvent of tetrahydrofuran and n-heptane, an aqueous LiCl solution is added, and an electrospinning solution is prepared to prepare a composite paper-based fiber membrane on one side of a hydrophilic paper base layer by electrospinning for 3-4 h; A plurality of hydrophobic microfluidic channels are written on the other side of the hydrophilic paper base layer of the composite paper-based fiber membrane, and the hydrophobic microfluidic channels are written using hydrophobic rosin ink, wherein the hydrophobic rosin ink is prepared by dissolving rosin in ethanol at a concentration of 0.5-0.7 g / mL; A pH detection module is obtained by adding a bromocresol green aqueous solution to the hydrophobic microfluidic channels and drying; A lactic acid detection module and a glucose detection module are respectively obtained by adding a mixed solution of ferric chloride and potassium ferricyanide to the hydrophobic microfluidic channels, drying, adding a mixed solution of chitosan and sodium alginate, adding lactic acid oxidase or glucose oxidase, and then adding a color developing agent. The sweat detection device synchronously detects pH, lactic acid and glucose in sweat based on colorimetry.

2. The method of claim 1, wherein the method is characterized by: The concentration of SEBS in the mixed solvent is 10-14 wt%.

3. The method of claim 1, wherein the method is characterized by: The solute mass fraction of the aqueous LiCl solution is 1-2%, and the volume ratio of the aqueous LiCl solution to the electrospinning solution is (0.5-1.5):

100.

4. The method of claim 1, wherein the method is characterized by: The writing speed is 550-650 mm / min.

5. The method of claim 1, wherein the method is characterized by: The mass ratio of ferric chloride to potassium ferricyanide is 1:(1.5-2.5).

6. The method of claim 1, wherein the method is characterized by: The mass ratio of chitosan to sodium alginate is (1-2):(1-2).

7. The method of claim 1, wherein the method is characterized by: In the preparation process of the lactic acid detection module, a buffer solution of dipotassium hydrogen phosphate and potassium dihydrogen phosphate is added after the color developing agent is added.

8. A sweat detection device based on a unidirectional drainage composite paper-based fibrous membrane, characterized by The sweat detection device is prepared by the method of any one of claims 1-7, and the structure of the sweat detection device comprises: a hydrophilic paper base layer; a hydrophobic SEBS fiber membrane arranged on one side of the hydrophilic paper base layer; a plurality of hydrophobic microfluidic channels arranged on the other side of the hydrophilic paper base layer; wherein the hydrophobic microfluidic channels comprise a pH detection module, a lactic acid detection module and a glucose detection module.

Images