Wearable microfluidic fluorescence sensor based on Janus membrane for sweat analysis

Abstract

The invention relates to the field of physiological status detection, and provides a wearable microfluidic fluorescence sensor based on a Janus membrane for sweat analysis. The sensor comprises a Janus membrane-based micro-fluidic chip and a fluorescent sensing layer which are stacked, the Janus membrane-based micro-fluidic chip comprises a hydrophobic nanofiber membrane, a bottom polydimethylsiloxane layer, a hydrophilic nanofiber membrane and a top polydimethylsiloxane layer which are stacked, and the fluorescent sensing layer comprises three paper chips, the simultaneous fluorescence detection of chloride ions, glucose and pH of sweat is realized. The Janus membrane with the directional water conveying capacity is used as a substrate for preparing a micro-fluidic chip. In one aspect, sweat may be automatically delivered to an analysis zone along a designed path. On the other hand, sweat is transferred from a hydrophobic membrane close to the skin to a hydrophilic membrane, sweat accumulation is effectively avoided, and a comfortable skin microenvironment is promoted. A Janus membrane-based micro-fluidic chip is combined with fluorescence sensing, a micro-fluidic fluorescence sensor based on a Janus membrane is constructed, and simultaneous high-stability and high-accuracy analysis of multiple targets in human sweat is realized.

Description

Technical Field

[0001] The present invention belongs to the field of physiological state detection, and in particular relates to a wearable microfluidic fluorescence sensor based on a Janus membrane for sweat analysis. Background Art

[0002] Wearable sweat sensors can be worn directly on human skin to achieve real-time and continuous monitoring of sweat and provide real-time physiological information at the molecular level. Sweat sampling is a key step in wearable sensors and will affect the reliability and accuracy of the results. Commonly used sweat sampling devices in wearable sensors include absorbent materials and microfluidic chips. Among them, microfluidic chips play a very important role in sweat sampling in wearable sensors because they can accurately control the flow direction and volume of sweat, avoid contamination of sweat by the external environment, and reduce crosstalk between sensor units.

[0003] At present, the substrates of wearable microfluidic chips are mainly polydimethylsiloxane (PDMS) and paper. PDMS-based microfluidic chips mainly use the pressure generated by sweat secretion and capillary action to guide sweat from the secretion site to the sensing area. These chips have excellent flexibility and stretchability, and can work normally even under severe deformation without hurting the skin. However, the air permeability of PDMS-based chips is poor, which causes sweat to accumulate at the interface between the skin and the chip, thus affecting the wearing comfort. In addition, PDMS-based microfluidic chips mainly use soft lithography technology, resulting in high cost and complex process for chip manufacturing. Paper-based microfluidic chips mainly rely on hydrophilic filter paper as a medium to realize the transport of sweat, and have the characteristics of simple manufacturing process, low cost, good air permeability, and strong portability. Although the paper substrate has good air permeability, it generally has a single hydrophilic property, and the problem of sweat accumulation at the interface between the skin and the chip still exists. In addition, the composition of the paper substrate material is not easy to adjust, and double-sided tape or clamps are required to assemble the various layers of the chip, which will cause problems such as poor sealing, poor stability, poor repeatability and poor comfort. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a wearable microfluidic fluorescence sensor based on Janus membrane for sweat analysis.

[0005] The first object of the present invention is to provide a wearable microfluidic fluorescence sensor based on Janus membrane.

[0006] The second object of the present invention is to provide the wearable microfluidic fluorescence sensor based on Janus membrane for sweat component analysis.

[0007] A third object of the present invention is to provide a device for analyzing sweat components.

[0008] In order to achieve the above object, the present invention is implemented by the following scheme:

[0009] A wearable microfluidic fluorescence sensor based on a Janus membrane, comprising a stacked Janus membrane-based microfluidic chip and a fluorescence sensing layer;

[0010] The Janus membrane-based microfluidic chip comprises a stacked Janus membrane and two patterned polydimethylsiloxane (PDMS) layers.

[0011] The Janus membrane is composed of a layer of hydrophobic nanofiber membrane and a layer of hydrophilic nanofiber membrane;

[0012] The patterned PDMS layer comprises a bottom PDMS layer and a top PDMS layer, wherein the bottom PDMS is located between the hydrophobic nanofiber membrane and the hydrophilic nanofiber membrane, wherein the bottom PDMS comprises an inlet, a flow channel and an analysis area substrate, and the top PDMS is located on the hydrophilic nanofiber membrane, wherein the top PDMS comprises an inlet, three channels and three analysis areas;

[0013] The inlet of the top PDMS corresponds to the inlet of the bottom PDMS, the channel of the top PDMS corresponds to the bottom PDMS flow channel substrate, and the analysis area of ​​the top PDMS corresponds to the bottom PDMS analysis area substrate;

[0014] The fluorescent sensing layer comprises three paper analysis sheets, and the paper analysis sheets correspond to the analysis areas of the Janus membrane-based microfluidic chip.

[0015] Preferably, the hydrophobic nanofiber membrane material is prepared from polyurethane.

[0016] More preferably, the hydrophobic nanofiber membrane is prepared from a polyurethane solution.

[0017] More preferably, the concentration of the polyurethane solution is 20-26 wt %.

[0018] More preferably, the concentration of the polyurethane solution is 24 wt %.

[0019] More preferably, the hydrophobic nanofiber membrane is prepared by using electrostatic spinning technology with a polyurethane solution as the spinning solution.

[0020] Preferably, the hydrophilic nanofiber membrane material is prepared from polyimide and sodium dodecyl sulfate.

[0021] More preferably, the hydrophilic nanofiber membrane material is prepared from polyimide and sodium dodecyl sulfate solution.

[0022] More preferably, the polyimide concentration in the polyimide and sodium dodecyl sulfate solution is 19 wt % to 21 wt %.

[0023] More preferably, the polyimide concentration in the polyimide and sodium dodecyl sulfate solution is 20 wt %.

[0024] More preferably, the concentration of sodium dodecyl sulfate in the polyimide and sodium dodecyl sulfate solution is 0.005 g / mL to 0.015 g / mL.

[0025] More preferably, the concentration of sodium dodecyl sulfate in the polyimide and sodium dodecyl sulfate solution is 0.01 g / mL.

[0026] More preferably, the hydrophilic nanofiber membrane is prepared by electrospinning technology using polyimide and sodium dodecyl sulfate solution as spinning liquid.

[0027] Preferably, the PDMS layer material is prepared from a precursor liquid and a curing liquid.

[0028] More preferably, the PDMS layer is prepared by ink direct writing technology, using precursor liquid and curing liquid as ink, nanofiber membrane as substrate, and heating to cure the PDMS.

[0029] More preferably, the heating temperature is 50-90°C.

[0030] More preferably, the heating temperature is 70°C.

[0031] Preferably, the number of the fluorescence detection paper analysis sheet is at least one.

[0032] More preferably, the number of the fluorescence detection paper analysis sheets is 3, which are used to detect chloride ions, glucose and pH in sweat samples respectively.

[0033] When in use, the sensor is attached to the skin surface, and the sweat on the skin reaches the analysis area through the entrance and contacts the fluorescent paper in the analysis area. The target in the sweat reacts with the analytical reagent on the paper to generate a fluorescent signal.

[0034] Compared with the prior art, the present invention has the following characteristics:

[0035] The present invention discloses a wearable microfluidic fluorescence sensor based on Janus membrane for sweat analysis. The invented wearable microfluidic fluorescence sensor based on Janus membrane includes a Janus membrane microfluidic chip and a fluorescent paper sheet, which realizes simultaneous fluorescence detection of chloride ions, glucose and pH in sweat. The Janus membrane with directional water transport capability is used as the substrate for constructing the microfluidic chip, which can quickly discharge sweat from the skin-chip interface and prevent sweat accumulation, thereby giving the chip excellent wearing comfort. On the other hand, the hydrophilic nanofibers embedded in the microfluidic channel allow the automatic transport of sweat. In addition, the integrated manufacturing of the microfluidic chip can be achieved by adopting a layer-by-layer manufacturing strategy based on electrospinning and ink direct writing technology, ensuring a strong connection between each layer. As a proof of concept, the developed microfluidic chip is integrated with a fluorescence analysis unit to establish a Janus membrane-based microfluidic sensor for analyzing multiple components in sweat. Subsequently, a portable 3D printing device with a smartphone interface is used to record the color signal of the sensing area and convert it into RGB values, thereby indicating the level of the analyte. The wearable microfluidic fluorescence sensor based on the Janus membrane of the present invention has excellent wearing comfort, good stability and high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the structure of a wearable microfluidic fluorescence sensor based on a Janus membrane in Example 1;

[0037] Figure 2 This is a physical picture of the wearable microfluidic fluorescence sensor based on the Janus membrane in Example 1;

[0038] Figure 3 This is a test of the in-body sweat directional transfer performance of the Janus membrane of Example 1.

[0039] Figure 4 This is the anti-interference property of the wearable microfluidic fluorescence sensor based on Janus membrane in Example 1.

[0040] Figure 5 This is the stability of the wearable microfluidic fluorescence sensor based on Janus membrane in Example 1.

[0041] Figure 6 This is the actual detection situation of the wearable microfluidic fluorescence sensor based on Janus membrane in Example 1.

[0042] Figure captions: 1-Janus-based microfluidic chip; 2-fluorescent paper chip; 11-hydrophobic nanofiber layer; 12-bottom PDMS layer; 13-hydrophilic nanofiber layer; 14-top PDMS layer. DETAILED DESCRIPTION

[0043] The present invention is further described below in conjunction with the accompanying drawings and examples, but the examples are only used to explain the present invention and are not limited to the following examples. The large materials used in the following examples, unless otherwise specified, are all obtained from commercial sources.

[0044] Example 1 A wearable microfluidic fluorescence sensor based on Janus membrane

[0045] like Figure 1 As shown, a wearable microfluidic fluorescence sensor based on a Janus membrane comprises a Janus membrane microfluidic chip 1 and a fluorescent paper chip 2 stacked in sequence.

[0046] The Janus membrane microfluidic chip 1 comprises a hydrophobic nanofiber membrane 11, a bottom PDMS layer 12, a hydrophilic nanofiber membrane 13 and a top PDMS layer 14 which are stacked in sequence.

[0047] The inlet, channel, and analysis area of ​​the top PDMS layer 14 correspond to the inlet, flow channel base, and analysis area base of the bottom PDMS layer 12 , respectively.

[0048] The fluorescent paper chip 2 comprises three analysis paper chips for detecting chloride ions, glucose and pH, respectively, and the paper chips correspond to the analysis areas.

[0049] like Figure 2 The figure shows the actual sensor.

[0050] Example 2 Example 1 Preparation method of wearable microfluidic fluorescence sensor based on Janus membrane

[0051] 1. Preparation of Janus membrane microfluidic chip 1

[0052] (1) Preparation of polyurethane spinning solution

[0053] A certain amount of polyurethane powder was added into N,N-dimethylformamide solvent and magnetically stirred for 6 hours to form a polyurethane solution with a mass fraction of 24 wt%.

[0054] (2) A layer of polyurethane nanofiber membrane is deposited by electrospinning technology, namely the hydrophobic nanofiber membrane 11 of Example 1.

[0055] (3) Preparation of PDMS ink

[0056] The precursor liquid and curing agent were mixed (mass ratio 10:1), stirred for 30 minutes, and placed in a 4°C refrigerator to remove bubbles.

[0057] (4) With the hydrophobic nanofiber membrane 11 as the substrate, the bottom PDMS layer 12 is directly written on the hydrophobic nanofiber membrane 11 using the ink direct writing technology, and the substrate heating temperature is 70°C.

[0058] (5) Preparation of polyimide and sodium dodecyl sulfate spinning solution

[0059] Take 0.1 g of sodium dodecyl sulfate powder and add it to 10 mL of polyimide solution and stir for 5 h.

[0060] (6) A layer of polyimide and sodium dodecyl sulfate nanofiber membrane is deposited on the above layer using electrospinning technology, namely the hydrophilic nanofiber membrane 13 of Example 1.

[0061] (7) With the above layer as the substrate, the top PDMS layer 14 is directly written on the hydrophilic nanofiber membrane 13 using ink direct writing technology, and the substrate heating temperature is 70°C.

[0062] 2. Preparation of fluorescent paper chips

[0063] (1) Cut the filter paper into a circle with a diameter of mm and coat the corresponding analytical reagent on it to obtain the fluorescent paper chip 2.

[0064] (2) Preparation of analytical reagents

[0065] Glucose fluorescent paper chip: Dissolve 5.0 mg of glucose oxidase and 0.5 mg of horseradish peroxidase in 1 mL of phosphate buffer (pH = 7.0). Then, prepare a fluorescein solution (0.1 mM) and chitosan (1%) dissolved in 2% acetic acid. Pour 3 μL of glucose oxidase, horseradish peroxidase, fluorescein and chitosan solution onto filter paper. Chloride ion fluorescent paper chip: Pour 3 μL of quinine solution (0.5 mM in 0.1 M sulfuric acid) onto filter paper. pH fluorescent paper chip: The pH determination reagent consists of 0.2 mM fluorescein and 0.1 mM NaCl. Then adjust the pH of the solution to 4.0 with hydrochloric acid. Add 3 μL of the prepared solution onto the pH determination filter paper.

[0066] Example 3 Example 1 In-body sweat directional transfer performance of Janus membrane

[0067] 1. Experimental Methods

[0068] Cotton fiber, filter paper and the Janus membrane of Example 1 were attached to the sweating skin surface of human body respectively, and the directional water transfer performance of the three matrices was compared by observing the sweat conditions at the interface between the three matrices and the skin.

[0069] 2. Experimental Results

[0070] Sweat residues appeared at the interface between the cotton fiber and the filter paper and the skin, while the interface between the Janus membrane of Example 1 and the skin remained dry, indicating that the Janus membrane of Example 1 had the function of preventing sweat accumulation.

[0071] Example 4: Anti-interference performance of the sensor

[0072] 1. Experimental Methods

[0073] Select common substances in sweat 10mM Na + , 10mM K + 、10mM NO 3 - , 1 mM uric acid, 20 mM lactic acid, 10 mM ascorbic acid, and 10 mM urea were used as interfering substances, and relevant solutions were prepared and added to the paper chip in the analysis area of ​​the sensor in Example 1 respectively.

[0074] 2. Experimental Results

[0075] The results are as follows Figure 4 As shown, the sensor target of Example 1 alone produces a significant color response, while the signal change caused by the interfering substance is negligible. The T-test also shows that no statistical difference is found within the 95% confidence interval, confirming that the sensor of Example 1 has excellent anti-interference ability.

[0076] Example 5 Sensor Stability

[0077] 1. Experimental Methods

[0078] The sensor of Example 1 was placed in a 4°C environment, and a reagent containing chloride ions and glucose (with a certain concentration and pH) was used to detect changes in the sensor signal within 10 days.

[0079] 2. Experimental Results

[0080] The results are as follows Figure 5 As shown, the relative standard deviation of each target signal within 10 days is within 3.15%. The results show that the sensor of Example 1 has good stability.

[0081] Example 6 Actual Sample Analysis

[0082] 1. Experimental Methods

[0083] Volunteers were recruited, the sensor of Example 1 was worn on the forearm of the volunteer, and the volunteer was asked to exercise. After 15 minutes of exercise, the signal was captured from the analysis area using a portable 3D printing device, and then converted into concentration data according to the curve obtained above.

[0084] 2. Experimental Results

[0085] The results are as follows Figure 6As shown, the ranges of chloride ion, glucose and pH value in the sweat of volunteers measured by the sensor of Example 1 were 33.4-50.2 mM, 67.1-105.2 μM and 4.9-5.5, respectively. In addition, sweat was collected and analyzed with laboratory instruments. The data obtained by the sensor of Example 1 were consistent with the data of the standard method. The results show the feasibility of the sensor of Example 1 in actual detection of sweat.

[0086] Finally, it should be noted that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto, and any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A wearable microfluidic fluorescence sensor based on Janus membrane, characterized in that: It includes a Janus membrane-based microfluidic chip layer and a fluorescent sensing layer. The Janus membrane-based microfluidic chip comprises a stacked Janus membrane and two patterned polydimethylsiloxane (PDMS) layers; The Janus membrane is composed of a layer of hydrophobic nanofiber membrane and a layer of hydrophilic nanofiber membrane; The fluorescent sensing layer comprises three paper analysis chips.

2. A wearable microfluidic fluorescence sensor based on a Janus membrane according to claim 1, characterized in that: The patterned PDMS layer comprises a bottom PDMS layer and a top PDMS layer; The bottom PDMS is located between the hydrophobic nanofiber membrane and the hydrophilic nanofiber membrane; The bottom PDMS includes an inlet, flow channel and analysis area substrate; The top PDMS is located on the hydrophilic nanofiber membrane; The top PDMS comprises an inlet, three channels and three analysis areas; The inlet of the top PDMS corresponds to the inlet of the bottom PDMS; The channel of the top PDMS corresponds to the bottom PDMS flow channel substrate; The analysis area of ​​the top PDMS corresponds to the bottom PDMS analysis area substrate.

3. A wearable microfluidic fluorescence sensor based on a Janus membrane according to claim 1, characterized in that: The paper analysis sheet corresponds to the analysis area of ​​the Janus membrane-based microfluidic chip.

4. A wearable microfluidic fluorescence sensor based on a Janus membrane according to claim 1, characterized in that: The detection liquid is sweat.

5. A device for analyzing sweat components, characterized in that: The device comprises the sensor according to any one of claims 1 to 3.

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