Sweat microfluidic sensor and method of making same

Abstract

The application provides a sweat micro-fluidic sensor and a preparation method thereof, which comprises a substrate layer and a detection electrode; the substrate layer is provided with a sweat collection area, a waste liquid collection area, N side flow control cavities and N+1 flow control channels; the side flow control cavities are located between the sweat collection area and the waste liquid collection area, and the detection electrode is correspondingly located in each side flow control cavity; the sweat collection area and the waste liquid collection area are connected and communicated through the flow control channels connected at the head and tail, the first N flow control channels close to the sweat collection area are respectively communicated with the N side flow control cavities, the first end of the second flow control channel to the N+1 flow control channel is provided with a buffer barrier area, and the part of the flow control channel except the buffer barrier area and the side flow control cavity are hydrophilic areas; the buffer barrier area has hydrophobicity, or the buffer barrier area is provided with a heating electrode and a heat-sensitive gel layer, the heat-sensitive gel layer is dissolved by heat to make the corresponding flow control channel conductive, and the sequence flow control of the sweat is realized through the hydrophilic and hydrophobic effect or the opening sequence of the heating electrode.

Description

Technical Field

[0001] This invention relates to the field of sweat biodetection and microfluidics, and in particular to a sweat microfluidic sensor and its preparation method. Background Technology

[0002] Sweat, a non-invasive biofluid, contains various chemical substances (such as electrolytes like sodium, potassium, and chloride ions, as well as cortisol) and small amounts of macromolecules (such as proteins and nucleic acids). It can be used to monitor health status, stress levels, exercise activity, and nutritional information. Sweat detection has great potential, especially wearable sweat sensors, which offer significant advantages for in-situ sweat analysis. Detection can be performed directly on the body without the need for collection, storage, or remote testing, greatly reducing material and time costs. Wearable sweat sensors can automatically and continuously analyze sweat samples, providing faster insights into the user's health.

[0003] Cortisol, also known as the stress hormone, helps maintain the body's physiological balance under stress. It's a biosignaling molecule that reflects physiological and psychological states. Under stress, the body needs cortisol to maintain normal physiological functions and respond quickly. However, prolonged strenuous exercise can lead to persistently high cortisol levels after reaching the fatigue stage, resulting in a weakened immune system and decreased bone density. Furthermore, chronic high levels of cortisol due to excessive psychological stress can cause immune disorders. Therefore, real-time monitoring of sweat cortisol is crucial for adjusting exercise performance and monitoring psychological stress levels, preventing physical damage caused by overtraining and excessive psychological stress. Additionally, sweat estrogen levels can reflect the body's hormonal metabolic cycle. Sweat proteins, such as interleukin-6 (IL-6), can monitor skin inflammation. However, in-situ sweat analysis technology also faces challenges, such as the mixing of old and new sweat, making it difficult to analyze fresh sweat and affecting the accuracy of the results.

[0004] Therefore, it is necessary to provide a new technical solution to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a sweat microfluidic sensor capable of sequential flow control and its preparation method. This sweat microfluidic sensor can avoid the mixing of new and old sweat and improve the accuracy of detection results.

[0006] This invention provides a sweat microfluidic sensor, comprising a substrate layer and an electrode layer located on the substrate layer, wherein the electrode layer includes a detection electrode;

[0007] The substrate layer is provided with a sweat collection area, a waste liquid collection area, N side flow control cavities, and N+1 flow control channels, where N is a positive integer greater than or equal to 2. The sweat collection area and the waste liquid collection area are arranged opposite each other at one end of the substrate layer. The N side flow control cavities are distributed at intervals between the sweat collection area and the waste liquid collection area, and the detection electrode is correspondingly arranged in each side flow control cavity. The sweat collection area and the waste liquid collection area are connected by N+1 flow control channels connected end to end in sequence. The first N flow control channels near the sweat collection area are respectively connected to the N side flow control cavities. The first ends of the second flow control channel to the N+1 flow control channel are provided with buffer barriers. The parts of the N+1 flow control channels other than the buffer barriers and the N side flow control cavities are all hydrophilic areas.

[0008] The buffer barrier region is hydrophobic. Under the hydrophilic-hydrophobic interaction, sweat flows sequentially from the sweat collection area through the flow control channel and enters the corresponding side flow control cavity. The sweat parameters are detected by the detection electrode. Alternatively, the buffer barrier region is provided with a heating electrode and a thermosensitive gel layer. The heating electrode is located on the electrode layer, and the thermosensitive gel layer is located on the heating electrode. Multiple heating electrodes are turned on sequentially. The corresponding thermosensitive gel layer dissolves upon heating, thereby opening the corresponding flow control channel. Sweat flows sequentially from the sweat collection area through the flow control channel and enters the corresponding side flow control cavity. The sweat parameters are detected by the detection electrode.

[0009] According to the sweat microfluidic sensor provided by the present invention, each of the side flow control cavities is further provided with a water-absorbing layer, the water-absorbing layer being located at one end of the side flow control cavity away from the flow control channel, and the orthographic projection of the water-absorbing layer on the substrate layer at least partially overlaps with the orthographic projection of the detection electrode on the substrate layer.

[0010] According to the sweat microfluidic sensor provided by the present invention, a portion of the side flow control cavity is further provided with the test strip, which is used to detect parameters of sweat. The test strip includes a sample pad, a detection band, and a quality control band. The sample pad is provided with a labeled antibody, the detection band is provided with an aptamer adapted to the labeled antibody, and the quality control band is provided with an anti-antibody.

[0011] The test strip is disposed in the same layer as the detection electrode, and the orthographic projection of the absorbent layer on the substrate layer at least partially overlaps with the orthographic projection of the test strip on the substrate layer.

[0012] According to the sweat microfluidic sensor provided by the present invention, the electrode layer further includes a plurality of counter electrodes and a reference electrode, the reference electrode being disposed in the sweat collection area, and the plurality of counter electrodes being disposed in N side flow control cavities in a one-to-one correspondence.

[0013] The other end of the substrate layer is provided with multiple electrode interfaces, and the detection electrode, the counter electrode and the reference electrode are respectively connected to the multiple electrode interfaces one by one.

[0014] According to the sweat microfluidic sensor provided by the present invention, the electrode layer further includes a plurality of sweat rate electrodes, which are disposed one-to-one in N side flow control cavities. The sweat rate electrodes are used to monitor the amount and rate of sweat secretion. The sweat rate electrodes are located at one end of the side flow control cavity near the flow control channel, and the plurality of sweat rate electrodes are connected in series with each other and connected to the corresponding electrode interface.

[0015] According to the sweat microfluidic sensor provided by the present invention, a sweat drug electropermeability enhancement module is further disposed on the substrate layer, the sweat drug electropermeability enhancement module is located corresponding to the sweat collection area, the sweat drug electropermeability enhancement module includes a permeability enhancement gel layer and a permeability enhancement electrode, the permeability enhancement gel layer includes a gel material and a permeability enhancement agent;

[0016] The permeation-promoting gel layer is provided with multiple sweat-guiding grooves, one end of each of the multiple sweat-guiding grooves extending toward the flow control channel.

[0017] This invention also provides a method for preparing a sweat microfluidic sensor, comprising the following steps:

[0018] Step 1, provide a base layer, on which a sweat collection area and a waste liquid collection area are provided opposite to each other, and N side flow control chambers are located between the sweat collection area and the waste liquid collection area, where N is a positive integer greater than or equal to 2;

[0019] Step 2: An electrode layer and an insulating layer are sequentially fabricated on the substrate layer. The electrode layer includes a detection electrode located in each of the side flow control cavity regions. The insulating layer exposes the electrode layer.

[0020] Step 3: Prepare N side flow control cavities corresponding to the N side flow control cavity areas, and prepare N+1 flow control channels connected end to end between the sweat collection area and the waste liquid collection area. The sweat collection area and the waste liquid collection area are connected through the N+1 flow control channels, and the first N flow control channels near the sweat collection area are respectively connected to the N side flow control cavities.

[0021] Step 4: The first ends of the second flow control channel to the N+1th flow control channel all include a buffer barrier area. The N+1 flow control channels, excluding the buffer barrier area, and the N side flow control cavities are hydrophilically modified.

[0022] Step 5: Perform hydrophobic modification on the buffer barrier region; or, the electrode layer may further include a heating electrode disposed corresponding to the buffer barrier region, and prepare a thermosensitive gel layer on the heating electrode.

[0023] The method for preparing the sweat microfluidic sensor according to the present invention further includes the following steps:

[0024] Step 6: Place the test strip in the side flow control cavity and fix it. The test strip is in the same layer as the detection electrode and is spaced apart from each other. The test strip includes a sample pad, a detection band and a control band. The sample pad contains a labeled antibody, the detection band contains an aptamer adapted to the labeled antibody, and the control band contains an anti-antibody.

[0025] The method for preparing the sweat microfluidic sensor according to the present invention further includes the following steps:

[0026] Step 7: Prepare an absorbent layer in each of the side flow control cavities, wherein the absorbent layer is located at the end of the side flow control cavity away from the flow control channel, and the absorbent layer overlaps with at least a portion of the detection electrode and / or the test strip.

[0027] According to the method for preparing a sweat microfluidic sensor provided by the present invention, in step 2, the electrode layer formed further includes a permeation-enhancing electrode located in the sweat collection area, and the preparation method further includes the following steps:

[0028] Step 8: Prepare a permeation-enhancing gel layer in the sweat collection area. The permeation-enhancing gel layer is located on the surface of the permeation-enhancing electrode. The permeation-enhancing gel layer includes a gel material and a permeation-enhancing agent.

[0029] The above-described technical solution of the present invention has the following beneficial effects:

[0030] The present invention provides a sweat microfluidic sensor and its preparation method, which sets N side flow control cavities and N+1 flow control channels between a sweat collection area and a waste liquid collection area, where N is a positive integer greater than or equal to 2. The sweat collection area and the waste liquid collection area are connected by N+1 flow control channels connected end to end in sequence. The first N flow control channels near the sweat collection area are connected to the N side flow control cavities respectively. A buffer barrier area is set at the beginning of each of the second to the N+1th flow control channels. A hydrophilic area is set in the part of the N+1 flow control channels other than the buffer barrier area and in the N side flow control cavities. By designing the buffer barrier area to be hydrophobic, or by setting a heating electrode and a thermosensitive gel layer in the buffer barrier area, the thermosensitive gel layer dissolves when heated to make the corresponding flow control channel conductive. By using hydrophilic and hydrophobic interactions or controlling the opening sequence of the heating electrodes, the sequential flow control of sweat is achieved, avoiding the mixing of new and old sweat, thereby improving the accuracy of the detection results. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the structure of a sweat microfluidic sensor provided in one embodiment of the present invention;

[0033] Figure 2 for Figure 1 A schematic diagram of the side flow control cavity shown;

[0034] Figure 3 This is a schematic diagram of the structure of a sweat microfluidic sensor provided in another embodiment of the present invention;

[0035] Figure 4 for Figure 3 A schematic cross-sectional view of the flow control channel in the buffer barrier area shown;

[0036] Figure 5 This is a schematic diagram of the structure of the test strip provided in an embodiment of the present invention;

[0037] Figure 6 A plan view of the sweat drug electro-permeation enhancement module provided in an embodiment of the present invention;

[0038] Figure 7 A cross-sectional schematic diagram of the sweat drug electro-permeation module provided in an embodiment of the present invention;

[0039] Figure 8A flowchart illustrating the fabrication method of the sweat microfluidic sensor provided in this embodiment of the invention;

[0040] Figure 9 This is a schematic cross-sectional view of two flow control channels in the buffer barrier area provided in one embodiment of the present invention;

[0041] Figure 10 This is a schematic diagram of the side flow control cavity for multi-parameter sweat detection provided in an embodiment of the present invention.

[0042] Figure label:

[0043] 1. Base layer; 2. Electrode layer; 3. Sweat collection area; 4. Waste liquid collection area; 5. Side flow control cavity; 6. Flow control channel; 6'. Inner pipe of flow control channel; 7. Absorbent layer; 8. Electrode interface; 9. Lead wire; 10. Test strip; 11. Penetration-enhancing gel layer; 12. Penetration-enhancing electrode; 13. Sweat-guiding groove; 14. Thermosensitive gel layer; 100. Side flow control cavity area; 101. Sample pad; 102. Detection strip; 103. Quality control strip; 201. Detection electrode; 202. Counter electrode; 203. Reference electrode; 204. Sweat rate electrode; 205. Heating electrode; 601. Buffer barrier area; 601'. Hydrophobic membrane; 201-1. First detection electrode; 201-2. Second detection electrode. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0045] Please see Figure 1 An embodiment of the present invention provides a sweat microfluidic sensor, including a base layer 1 and an electrode layer 2 located on the base layer 1. The electrode layer 2 includes a plurality of detection electrodes 201, which are used to detect parameters of sweat.

[0046] The substrate 1 comprises a sweat collection area 3, a waste liquid collection area 4, N side flow control chambers 5, and N+1 flow control channels 6, where N is a positive integer greater than or equal to 2. The sweat collection area 3 and the waste liquid collection area 4 are positioned opposite each other at one end of the substrate 1. The N side flow control chambers 5 are spaced apart between the sweat collection area 3 and the waste liquid collection area 4, and are connected by the N+1 flow control channels 6 connected end-to-end. The first N flow control channels 6 closest to the sweat collection area 3 are connected to the N side flow control chambers 5. Each flow control channel 6 from the second to the N+1th flow control channel 6 has a buffer barrier area 601 at its beginning. This buffer barrier area 601 is hydrophobic and can buffer and block a certain flow rate of sweat. The portions of the N+1 flow control channels 6, excluding the buffer barrier area 601, and the N side flow control chambers 5 are all hydrophilic areas, which are hydrophilic through hydrophilic treatment.

[0047] In this system, N side flow control cavities 5 are arranged sequentially from the sweat collection area 3 to the waste liquid collection area 4. Similarly, N+1 flow control channels 6 are arranged sequentially from the sweat collection area 3 to the waste liquid collection area 4. Each side flow control cavity 5 is equipped with a corresponding detection electrode 201. Under the buffering and blocking effect of the buffer barrier area 601 of the flow control channel 6 and the hydrophilic effect of the side flow control cavity 5, sweat automatically flows from the sweat collection area 3 through the flow control channel 6 in sequence and enters the corresponding side flow control cavity 5. The detection electrode 201 is used to detect sweat parameters. For example, when sweat flows from sweat collection area 3 into the first flow control channel 6, the buffering effect of the buffer barrier area 601 in the second flow control channel 6 and the hydrophilic effect of the side flow control cavity 5 cause the sweat to preferentially flow into the first side flow control cavity 5. After the first side flow control cavity 5 is full, the newly secreted sweat flowing into the flow control channel 6 will pass through the buffer barrier area 601 of the second flow control channel 6 as the flow rate accumulates. Furthermore, under the buffering effect of the buffer barrier area 601 in the third flow control channel 6 and the hydrophilic effect of the side flow control cavity 5, the sweat will automatically and sequentially flow into the second side flow control cavity 5, and so on, until the newly secreted sweat flows into the Nth side flow control cavity 5. After the Nth side flow control cavity 5 is full, the remaining sweat flows into the waste liquid collection area 4. In this way, sequential flow control of sweat can be achieved, and each side flow control cavity 5 contains newly generated sweat that reacts with the corresponding detection electrode 201, avoiding the mixing of new and old sweat, thereby improving the accuracy of the detection results.

[0048] Furthermore, in combination Figure 1 and Figure 2 As shown, each side flow control cavity 5 is also provided with a water-absorbing layer 7. The water-absorbing layer 7 plays a similar role to locking water. The water-absorbing layer 7 can lock the sweat entering the side flow control cavity 5 in the side flow control cavity 5 through its own adsorption capacity, so as to prevent the sweat entering the side flow control cavity 5 from flowing back or flowing back, thereby further preventing the problem of mixing of new and old sweat.

[0049] Furthermore, the absorbent layer 7 is located at the end of the side flow control cavity 5 away from the flow control channel 6, and the orthographic projection of the absorbent layer 7 on the base layer 1 at least partially overlaps with the orthographic projection of the detection electrode 201 on the base layer 1. Thus, when sweat flows into the corresponding side flow control cavity 5 due to capillary action and hydrophilicity, the sweat flows through the detection electrode 201 and reacts with the specific recognition material on the detection electrode 201. The reacted sweat then flows towards the absorbent layer 7, and the adsorption of the absorbent layer 7 prevents the reacted sweat from flowing back and mixing with newly secreted sweat.

[0050] Please continue reading. Figure 1 The electrode layer 2 also includes multiple counter electrodes 202 and a reference electrode 203. The reference electrode 203 is correspondingly disposed within the sweat collection area 3, and the multiple counter electrodes 202 are disposed one-to-one within N side flow control cavities 5. In the electrochemical system, the detection electrode 201 serves as the working electrode. The counter electrodes 202 and the working electrode form a circuit, ensuring the smooth flow of current to the working electrode and guaranteeing that the studied reaction occurs on the working electrode. The reference electrode 203 provides a stable standard potential and a constant current, serving as a reference point for measuring the potential and current of the working electrode.

[0051] The substrate layer 1 has multiple electrode interfaces 8 and multiple leads 9 at its other end. The detection electrode 201, counter electrode 202, and reference electrode 203 are connected to the multiple electrode interfaces 8 one-to-one via the leads 9. This sweat microfluidic sensor is connected to a wearable detector or electrochemical workstation via the electrode interfaces 8 to achieve the corresponding detection function. The detection method can be current detection, pulse voltammetry, open circuit potential method, potential detection, or impedance spectroscopy.

[0052] The electrode layer 2 further includes multiple sweat rate electrodes 204, which are disposed one-to-one within N side flow control cavities 5. The sweat rate electrodes 204 are used to monitor the amount and rate of sweat secretion. The sweat rate electrodes 204 are located at the end of the side flow control cavity 5 near the flow control channel 6 to monitor the amount and rate of sweat secretion. The multiple sweat rate electrodes 204 are connected in series and connected to corresponding electrode interfaces 8 via leads 9.

[0053] The sweat rate electrode 204 uses resistance detection to detect the amount and rate of sweat secretion. For example, when sweat enters the first side flow control chamber 5, the sweat rate electrode 204 in the first side flow control chamber 5 is turned on, and the sweat rate electrode 204 will generate a resistance change after the sweat flows through it; when new sweat enters the second side flow control chamber 5, the sweat rate electrode 204 in the second side flow control chamber 5 is turned on, which further reduces the total resistance of the multiple sweat rate electrodes 204. The change in total resistance can be used to analyze the rate of sweat secretion.

[0054] It is understandable that the electrode layer 2, the electrode interface 8, and the lead wire 9 can be fabricated using the same material in the same layer, but of course, this is not a limitation.

[0055] Please see Figure 3 and Figure 4 Another embodiment of the present invention provides a sweat microfluidic sensor. This sweat microfluidic sensor is similar to the one described above, except that: this embodiment does not require hydrophobic treatment of the buffer barrier region 601. The electrode layer 2 of this embodiment also includes multiple heating electrodes 205, which are correspondingly disposed in the buffer barrier region 601. Each heating electrode 205 has a thermosensitive gel layer 14, which can form a temporary barrier structure in the flow control channel 6. When the heating electrode 205 is energized, it heats the thermosensitive gel layer 14, causing it to dissolve and thus opening the corresponding flow control channel 6. In this embodiment, electrode interfaces 8 are formed at both ends of the substrate layer 1. Multiple heating electrodes 205 are connected to multiple electrode interfaces 8 near one end of the heating electrode 205 via multiple leads. By controlling multiple heating electrodes 205 to be turned on sequentially, the corresponding thermosensitive gel layers 14 can also be dissolved sequentially, thereby opening the corresponding flow control channels 6 sequentially and achieving sequential flow control of sweat. For example, sweat flows from the sweat collection area 3 into the first flow control channel 6. Due to the obstruction of the thermosensitive gel layer 14 in the second flow control channel 6, the sweat preferentially flows into the first side flow control cavity 5. After the first side flow control cavity 5 is full, the heating electrode 205 in the second flow control channel 6 is turned on and the thermosensitive gel layer 14 above it is dissolved, making the second flow control channel 6 open. Due to the obstruction of the thermosensitive gel layer 14 in the third flow control channel 6, newly secreted sweat then flows into the second side flow control cavity 5. After the second side flow control cavity 5 is full, the heating electrode 205 in the third flow control channel 6 is turned on and the thermosensitive gel layer 14 above it is dissolved, making the third flow control channel 6 open, and newly secreted sweat then flows into the third side flow control cavity 5, and so on, to achieve sequential flow control of sweat and prevent the mixing of new and old sweat.

[0056] The other structures of the sweat microfluidic sensor in this embodiment are the same as those in the sweat microfluidic sensor in the above embodiments, and will not be described again here.

[0057] Please see Figure 5Based on the above embodiments, at least a portion of the side flow control cavity 5 is further provided with a test strip 10, which is used to detect corresponding parameters of sweat. The test strip 10 is arranged in the same layer as the detection electrode 201 and spaced apart. The test strip 10 includes a sample pad 101, a detection band 102, and a control band 103. The sample pad 101 is provided with a labeled antibody, the detection band 102 is provided with an aptamer adapted to the labeled antibody, and the control band 103 is provided with an anti-antibody. The test strip 10 can be a small gold-labeled test strip, which can be used to detect sweat proteins and sweat hormones. The concentration is determined by the color change produced by the immune reaction aggregation of nano-gold particles in the reaction area.

[0058] The orthographic projection of the absorbent layer 7 onto the base layer 1 at least partially overlaps with the orthographic projection of the test strip 10 onto the base layer 1. The absorbent layer 7 can directly contact the end of the detection electrode 201 and the test strip 10 away from the flow control channel 6, so that the sweat after being detected by the detection electrode 201 and the test strip 10 flows into the absorbent layer 7. The adsorption of the absorbent layer 7 can prevent the sweat after the reaction from flowing back and mixing with the newly secreted sweat.

[0059] Combination Figure 1 , Figure 3 , Figure 6 and Figure 7 As shown, based on the above embodiments, a sweat drug electropermeation-enhancing module can also be provided on the base layer 1 of the present invention, and the sweat drug electropermeation-enhancing module is located in the sweat collection area 3. In cases where the body does not sweat naturally, the sweat drug electropermeation-enhancing module can stimulate sweat secretion. The sweat drug electropermeation-enhancing module includes a permeation-enhancing gel layer 11 and a permeation-enhancing electrode 12. The permeation-enhancing gel layer 11 includes a gel material and a permeation-enhancing agent. When the permeation-enhancing electrode 12 is conductive, it can introduce the permeation-enhancing agent in the permeation-enhancing gel layer 11 into the skin pores, thereby stimulating sweat secretion. The permeation-enhancing electrode 12 can be prepared in the same layer as the detection electrode 201, the counter electrode 202, and the reference electrode 203. The permeation-enhancing electrode 12 can be made of a stable metal material (such as gold, platinum, titanium, etc.) or a carbon material; alternatively, the reference electrode 203 can also be time-divisionally reused as a permeation-enhancing electrode.

[0060] The sweat-dispensing electro-permeability enhancement module can be used selectively depending on the application scenario. For example, it may not be necessary in sports or hot and humid environments. However, it is required in scenarios where sweating is minimal. This module uses a microcurrent (constant current 0.1–2 mA) to introduce the permeation enhancer in the permeation gel layer 11 into the skin pores, stimulating sweat secretion.

[0061] Furthermore, the permeation-enhancing gel layer 11 is provided with multiple sweat-guiding grooves 13, one end of each of the multiple sweat-guiding grooves 13 extending towards the flow control channel 6, which facilitates the concentrated flow of secreted sweat towards the flow control channel 6. The sweat-guiding grooves 13 can be formed directly on the permeation-enhancing gel layer 11 during its preparation, or they can be achieved by placing a thin layer of plastic or polymer pattern on the permeation-enhancing gel layer 11.

[0062] In addition, the sweat microfluidic sensor of the present invention may also include an encapsulation layer for encapsulating the sweat microfluidic sensor, and the encapsulation layer exposes the electrode interface 8.

[0063] In one embodiment, the encapsulation layer is a PE / PI material with a single-sided pressure-sensitive adhesive.

[0064] This invention also provides a method for preparing a sweat microfluidic sensor, which is described below in conjunction with... Figure 1 , Figure 3 , Figure 4 and Figure 8 The preparation method of the sweat microfluidic sensor of the present invention will be described in detail, and the preparation method includes the following steps:

[0065] Step 1: Provide a base layer 1, on which a sweat collection area 3 and a waste liquid collection area 4 are provided opposite to each other, and N side flow control chambers 100 located between the sweat collection area 3 and the waste liquid collection area 4, where N is a positive integer greater than or equal to 2.

[0066] Among them, the sweat collection area 3 is mainly used to collect the sweat produced by the body, and the waste liquid collection area 4 is mainly used to collect the excess sweat after the test is completed.

[0067] The substrate 1 can be a rigid substrate or a flexible substrate. Flexible substrate materials have a certain degree of flexibility, can be bent, can withstand the high temperatures during electrode fabrication, and are easy to cut and process.

[0068] Step 2: Electrode layer 2 and insulating layer (not shown) are sequentially prepared on substrate layer 1. Electrode layer 2 includes detection electrode 201 located in each side flow control cavity region 100. Insulating layer exposes electrode layer 2.

[0069] The electrode layer 2 may also include a counter electrode 202, a reference electrode 203, and a sweat rate electrode 204. The counter electrode 202 and the sweat rate electrode 204 are prepared in N side flow control cavity regions 100 in a one-to-one correspondence, and the reference electrode 203 is prepared in the sweat collection region 3.

[0070] Electrode layer 2 can be prepared by sputtering or vapor deposition of metals such as gold, platinum, and titanium, or by printing with carbon materials, or by using diamond electrodes.

[0071] After the electrode layer is prepared in step 2 above, step 2 may further include surface modification treatment of electrode layer 2. Specifically, surface modification treatment may be performed on some or all of the electrodes in electrode layer 2 according to actual detection requirements, so that the corresponding electrodes can achieve the corresponding detection function.

[0072] Specifically, the surface of the reference electrode 203 needs to be further modified with Ag / AgCl to maintain the stability of the reference during circuit detection. Ag / AgCl can be prepared by printing commercially available Ag / AgCl paste; alternatively, a silver layer can be modified on the metal electrode first, and then the surface of the silver layer can be chlorinated to form an Ag / AgCl modified layer.

[0073] The detection electrode 201 includes a conductive electrode layer and a modification layer located on the surface of the conductive electrode layer. The conductive electrode layer can be at least one metallic material selected from gold, platinum, and titanium, or it can be a carbon material, or it can be a diamond electrode material. The modification layer includes, but is not limited to, at least one of a mediator layer, a nano-modification layer, and a specific modification layer. The detection electrode 201 can be a single-parameter electrode, or it can be extended to a multi-parameter electrode.

[0074] The mediator layer can be modified with at least one of polypyrrole, Prussian blue, poly(3,4-ethylenedioxythiophene / polystyrene sulfonate) (PEDOT-PSS), polythionine and polyaniline to improve the electron transport efficiency of the electrode.

[0075] The nano-modification layer is used to improve the sensitivity of the electrode, and can be modified with highly conductive nanomaterials such as gold nanoparticles, platinum black nanoparticles, carbon nanotubes or graphene.

[0076] Specific modification layers require modification using aptamers or molecularly imprinted polymers (MIPs).

[0077] When the detection electrode 201 is required to detect proteins in sweat, its surface is modified with an aptamer at a concentration of 1 μM to 1000 μM. Preferably, the aptamer concentration is 10 μM. Protein detection using the detection electrode 201 can be performed using differential pulse voltammetry (DPV), cyclic voltammetry (CV), or electrochemical impedance spectroscopy (EIS) to determine protein concentration.

[0078] When the detection electrode 201 is used to detect hormones in sweat, its surface can be modified with a corresponding aptamer or with a molecularly imprinted polymer film. The concentration of the corresponding aptamer modification is 1 μM-1000 μM. Preferably, the aptamer modification concentration is 10 μM. The molecularly imprinted polymer film can be co-deposited with polypyrrole, Prussian blue, and other molecules. The hormone concentration in sweat is detected using electrochemical chronoamperometry or IT chronoamperometry.

[0079] Step 3: Prepare N side flow control cavities 5 corresponding to N side flow control cavity regions 100, and prepare N+1 flow control channels 6 connected end to end between sweat collection region 3 and waste liquid collection region 4. The sweat collection region 3 and waste liquid collection region 4 are connected through N+1 flow control channels 6, and the first N flow control channels 6 closest to the sweat collection region 3 are connected to the N side flow control cavities 5 respectively.

[0080] In this process, materials such as polydimethylsiloxane (PDMS), polycarbonate (PC), or polyethylene (PE) are used to form flow control channels 6 and side flow control cavities 5 by laser cutting or molding and attaching them to the substrate layer 1. The side flow control cavities 5 surround the side flow control cavity region 100 and expose the electrodes within the side flow control cavity region 100.

[0081] Step 4: The first ends of the second flow control channel to the N+1th flow control channel all include a buffer barrier area. The parts of the N+1 flow control channels excluding the buffer barrier area and the N side flow control cavities are hydrophilically modified.

[0082] Specifically, before hydrophilic treatment, a protective film is first applied to cover the hydrophobic portion and the electrode layer to eliminate hydrophilic effects. Then, the entire flow control channel 6 and the side flow control cavity 5 are hydrophilically modified. The substrate layer to be hydrophilically treated is cleaned using plasma. Afterward, hydrophilic treatment is performed using surfactants such as Triton X-100 (polyethylene glycol octylphenyl ether), Tween 20 (polyoxyethylene sorbitan monolaurate), SDS (sodium dodecyl sulfate), CTAB (hexadecyltrimethylammonium bromide), or sodium lauryl sulfate. Commonly used hydrophilic molecules include hydroxyl compounds, polyvinyl alcohol (PVA), and polyacrylic acid (PAA).

[0083] Step 5: Perform hydrophobic modification on the buffer barrier region; or, the electrode layer may also include a heating electrode disposed on the corresponding buffer barrier region, and prepare a thermosensitive gel layer on the heating electrode.

[0084] Specifically, hydrophobic modification is performed using octadecanethiol (OTS) or dodecylmercaptan (DDM). For example, a 95% concentration of dodecylmercaptan is used to modify the hydrophobic portion for 30 seconds, thereby forming a hydrophobic film 601' on the surface of the hydrophobic portion of the flow channel 6. Figure 9 As shown in (a) and (b) in the figure. The hydrophobic membrane 601' will form a step barrier in the channel 6' within the flow control channel. Due to the hydrophobic effect and the step barrier effect, the hydrophobic membrane 601' forms an obstruction in the flow control channel 6, causing sweat to preferentially flow into the hydrophilic side flow control cavity 5.

[0085] The hydrophobic membrane 601' can be formed into a U-shaped stepped structure using polyvinyl chloride (PVC) or polydimethylsiloxane (PDMS) materials. When PVC is used for the hydrophobic membrane 601', the PVC material is dissolved in cyclohexanone and then coated onto the position of the buffer barrier region 601 corresponding to the flow control channel 6 to form a U-shaped stepped hydrophobic membrane 601'.

[0086] After the above-mentioned hydrophilic and hydrophobic modifications, sweat can automatically and sequentially enter the side flow control cavity 5 through the hydrophilic / hydrophobic effect of the flow control channel 6, thereby realizing sequential flow control of sweat, avoiding the mixing of new and old sweat, and thus improving the accuracy of the test results.

[0087] Alternatively, during the preparation of the electrode layer in step 2 above, a heating electrode 205 is also formed at the position corresponding to the buffer barrier region 601. Step 5 above forms a temporary barrier structure in the flow control channel 6 by preparing a thermosensitive gel layer 14 on the heating electrode 205, thereby creating a temporary barrier against sweat.

[0088] Combination Figure 1 , Figure 3 and Figure 5 Furthermore, the above-mentioned method for preparing the sweat microfluidic sensor also includes the following steps:

[0089] Step 6: Place the test strip 10 in the side flow control cavity 5 and fix it. The test strip 10 is in the same layer as the detection electrode 201 and is spaced apart from each other. The test strip 10 includes a sample pad 101, a detection band 102 and a control band 103. The sample pad 101 contains labeled antibodies, the detection band 102 contains aptamers adapted to the labeled antibodies, and the control band 103 contains anti-antibodies.

[0090] Among them, the test strip 10 can detect sweat proteins and sweat hormones, and the concentration can be determined by the color change produced by the immune reaction aggregation of nano-gold particles in the reaction area.

[0091] Furthermore, based on the above embodiments, the method for preparing the sweat microfluidic sensor of the present invention further includes the following steps:

[0092] Step 7: Prepare a water-absorbing layer 7 in each side flow control cavity 5. The water-absorbing layer 7 is located at the end of the side flow control cavity 5 away from the flow control channel 6, and the water-absorbing layer 7 overlaps with at least a portion of the detection electrode 201 and / or the test strip 10.

[0093] The absorbent layer 7 can directly contact the end of the detection electrode 201 and the test strip 10 away from the flow control channel 6, so that the sweat after being detected by the detection electrode 201 and the test strip 10 flows into the absorbent layer 7. The adsorption of the absorbent layer 7 can prevent the sweat after the reaction from flowing back and mixing with the newly secreted sweat.

[0094] In one embodiment of the present invention, the electrode layer 2 formed in step 2 above further includes a permeation-enhancing electrode 12, which is located in the sweat collection area 3. When the body does not sweat naturally, the combination of the permeation-enhancing electrode 12 and the permeation-enhancing gel layer 11 can stimulate sweat secretion. Specifically, the preparation method further includes the following steps:

[0095] Step 8: Prepare a permeation-enhancing gel layer 11 in the sweat collection area 3. The permeation-enhancing gel layer 11 is located on the surface of the permeation-enhancing electrode 12. The permeation-enhancing gel layer 11 includes a gel material and a permeation-enhancing agent.

[0096] Among them, the permeation-enhancing electrode 12 can introduce the permeation-enhancing agent in the permeation-enhancing gel layer 11 into the skin pores under the action of microcurrent, thereby stimulating sweat secretion and realizing long-term continuous detection of sweat.

[0097] The following combination Figures 1 to 10 The preparation method of the sweat microfluidic sensor of the present invention will be described in detail from different embodiments, as follows.

[0098] Example 1

[0099] Combination Figure 1 , Figure 2 as well as Figures 6-10 As shown, in this embodiment, polyimide (PI) is used as the substrate layer 1 of the sweat microfluidic sensor, and the thickness of the substrate layer 1 is 20 micrometers to 500 micrometers. The substrate layer 1 is provided with a sweat collection area 3 and a waste liquid collection area 4 arranged opposite to each other, as well as N side flow control chambers 100 located between the sweat collection area 3 and the waste liquid collection area 4, where N is a positive integer greater than or equal to 2.

[0100] First, the electrode layer 2, electrode interface 8, and lead wire 9 are fabricated on the substrate layer 1 by sputtering, evaporation, or electrodeposition of a metallic material (such as platinum, gold, or titanium); or, the electrode layer 2, electrode interface 8, and lead wire 9 are fabricated on the substrate layer 1 by printing carbon paste or silver paste. The electrode layer 2 includes, but is not limited to, a detection electrode (i.e., working electrode) 201, a counter electrode 202, a reference electrode 203, and a sweat rate electrode 204. Depending on the single-parameter or multi-parameter detection requirements of the sweat microfluidic sensor, the number of detection electrodes 201 in each side flow control cavity region 100 can be one, two, or more.

[0101] Next, an insulating layer is prepared on electrode layer 2, exposing reference electrode 203, counter electrode 202, detection electrode 201, sweat rate electrode 204 and electrode interface 8.

[0102] Next, the surface of the reference electrode 203 is modified with Ag / AgCl to maintain the stability of the reference during circuit detection.

[0103] Next, the detection electrode 201 is modified as follows:

[0104] First, the medium is fixed and modified, that is, the detection electrode 201 is modified with polypyrrole, Prussian blue, PEDOT-PSS, polythionine or polyaniline to improve the electron transport efficiency of the detection electrode 201.

[0105] Then, Prussian blue was fixed by electrodeposition. A 5 mM Prussian blue (PB) solution (10 mM FeCl3, 10 mM K3[Fe(CN)6], and 1 mM–100 mM HCl, 1 mM KCl) was used with pH 7.4 PBS as the supporting electrolyte. Electropolymerization was performed for 10–50 cycles at a scan rate of 50 mV / s within the range of -0.2 V to 0.9 V. The deposition of Prussian blue facilitated electron transport.

[0106] Subsequent nanoparticle modification was performed, which could be achieved through the electrodeposition of gold nanoparticles. A 1 mM solution of chloroauric acid (HAuCl4) was prepared using deionized water. Then, an electrochemical deposition technique was employed using a three-electrode system (Pt wire electrode - counter electrode, silver / silver chloride (Ag / AgCl) electrode - reference electrode, and carbon electrode - working electrode) to deposit AuNPs on the surface of the detection electrode. The deposition potential was set to -0.3 V, and the electrodeposition time was 500 s.

[0107] Combination Figure 8As shown, 2 μL-10 μM IL-6 aptamer solution was then added dropwise to the first detection electrode 201-1 modified with gold nanoparticles, and 2 μL-10 μM cortisol aptamer solution was added dropwise to the second detection electrode 201-2 modified with gold nanoparticles. The reaction was carried out at 4 °C for 7 hours. Afterwards, unbound aptamer solution was rinsed off with deionized water, and the electrode surfaces were allowed to dry, resulting in aptamer-modified detection electrodes. Finally, 5 μL-1 mM 6-mercapto-1-hexanol (MCH) solution was pipetted onto the first and second detection electrodes 201-1 and 201-2, and the reaction was allowed to proceed at room temperature for 1.5 hours to block the remaining active sites on the gold nanoparticles. The unbound MCH solution was then rinsed off with deionized water. The modified detection electrodes are capable of aptamer reactions, thus improving their detection sensitivity.

[0108] After the electrode layer is modified, flow control channels 6 and side flow control cavities 5 are formed on the substrate layer 1 using materials such as PDMS, PC, or PE through laser cutting or molding. The side flow control cavities 5 surround the side flow control cavity region 100 and expose the electrodes within the side flow control cavity region 100. Alternatively, flow control channels 6 and side flow control cavities 5 can be formed on the insulating layer through an etching process, with the side flow control cavities 5 exposing the electrodes within the side flow control cavity region 100.

[0109] Next, the flow control channel 6 and the side flow control cavity 5 are subjected to hydrophilic and hydrophobic modifications, as detailed below:

[0110] Before hydrophilic modification, a protective film is first used to cover the hydrophobic part of the flow control channel 6 and the electrode layer 2 to eliminate hydrophilic effects. Then, plasma oxygenation modification is used to increase hydrophilicity, and 1% Triton X-100 diluted liquid is used for further hydrophilic modification.

[0111] The protective film is then removed, and hydrophobic modification is performed using PVC or PDMS. The PVC is dissolved in cyclohexanone, and an appropriate amount (0.1-2 μL) is added dropwise to the hydrophobic portion of the flow control channel 6 using a pipette. After drying overnight, a U-shaped stepped hydrophobic film 601' is formed. It can be understood that the hydrophobic portion refers to the part corresponding to the buffer barrier region 601.

[0112] In addition, the hydrophobic portion can be further modified with 95% OTS for 30 seconds.

[0113] Furthermore, an absorbent layer 7 can be prepared in each side flow control cavity 5 to absorb the sweat after the reaction, which can prevent the sweat from flowing out of the side flow control cavity 5 and mixing with the newly secreted sweat.

[0114] Furthermore, a permeation-enhancing electrode 12 and a permeation-enhancing gel layer 11 can be prepared in the sweat collection area 3. The permeation-enhancing gel layer 11 is located on the surface of the permeation-enhancing electrode 12 and includes a gel material and a permeation-enhancing agent. When the permeation-enhancing electrode 12 is in a conductive state, the permeation-enhancing agent in the permeation-enhancing gel layer 11 can be introduced into the skin pores, thereby stimulating sweat secretion. The permeation-enhancing electrode 12 can be prepared in the same layer as the detection electrode 201, the counter electrode 202, and the reference electrode 203. The permeation-enhancing electrode 12 can be made of a stable metal material (such as gold, platinum, titanium, etc.) or a carbon material; alternatively, the reference electrode 203 can also be time-divisionally reused as a permeation-enhancing electrode.

[0115] Furthermore, multiple sweat-guiding grooves 13 can be formed on the permeation-enhancing gel layer 11 during its preparation. One end of each sweat-guiding groove 13 extends towards the flow control channel 6, which facilitates the concentrated flow of secreted sweat into the flow control channel 6. Alternatively, the sweat-guiding grooves 13 can also be achieved by placing a thin layer of plastic or polymer pattern on the permeation-enhancing gel layer 11.

[0116] Finally, the entire structure is encapsulated with a single-sided adhesive pressure-sensitive adhesive (PE / PI material), exposing the electrode interface 8.

[0117] In this embodiment, the sweat microfluidic sensor was tested using DPV, Square Wave Voltmetry (SWV), or EIS. Specifically, DPV had a potential of -0.4V to 0.6V, an amplitude of 0.05V, a pulse width of 0.06s, a potential increment of 0.004V, a sampling width of 0.02s, and a pulse period of 0.5s. SWV had a potential of -0.4V to 0.4V, a frequency of 30Hz, a step potential of 4mV, and an amplitude of 25mV. EIS had an amplitude of 5mV and a frequency range of 0.1Hz to 0.1MHz.

[0118] Example 2

[0119] Combination Figure 3 , Figure 4 as well as Figures 6-10 As shown, the preparation method of the sweat microfluidic sensor in this embodiment is similar to the preparation method of the sweat microfluidic sensor in Embodiment 1 above, as detailed below.

[0120] First, the electrode layer 2, electrode interface 8, and lead wire 9 are fabricated on the substrate layer 1 by sputtering, evaporation, or electrodeposition of a metallic material (such as platinum, gold, or titanium); or, the electrode layer 2, electrode interface 8, and lead wire 9 are fabricated on the substrate layer 1 by printing carbon paste or silver paste. The electrode layer 2 includes, but is not limited to, a detection electrode (i.e., working electrode) 201, a counter electrode 202, a reference electrode 203, a sweat rate electrode 204, and a heating electrode 205. Depending on the single-parameter or multi-parameter detection requirements of the sweat microfluidic sensor, the number of detection electrodes 201 in each side flow control cavity region 100 can be one, two, or more.

[0121] Next, an insulating layer is prepared on electrode layer 2, exposing reference electrode 203, counter electrode 202, detection electrode 201, sweat rate electrode 204, heating electrode 205 and electrode interface 8.

[0122] Next, the surface of the reference electrode 203 is modified with Ag / AgCl to maintain the stability of the reference during circuit detection.

[0123] Next, the detection electrode 201 is modified as follows:

[0124] First, the detection electrode 201 was modified with nanoparticles, which can be achieved through the electrodeposition of gold nanoparticles. A 1 mM chloroauric acid (HAuCl4) solution was prepared using deionized water. Then, an electrochemical deposition technique was employed using a three-electrode system (Pt wire electrode - counter electrode, silver / silver chloride (Ag / AgCl) electrode - reference electrode, carbon electrode - working electrode) to deposit AuNPs on the surface of the detection electrode. The deposition potential was set to -0.3 V, and the electrodeposition time was 500 s.

[0125] Then, the detection electrode 201 is modified by immobilizing and modifying the medium, conductive medium, and template molecules, specifically as follows:

[0126] Polypyrrole, Prussian blue, and cortisol were co-electrodeposited onto the surface of the detection electrode 201. A mixture of 20 mM pyrrole, 5 mM Prussian blue (PB) solution (10 mM FeCl3, 10 mM K3[Fe(CN)6], 1 mM to 100 mM HCl and 1 mM KCl) and 1 mM to 10 mM cortisol was prepared. PBS at pH 7.4 was used as the supporting electrolyte solution. Electrodeposition was performed in the range of -0.2 V to 0.9 V, and electropolymerization was carried out at a scan rate of 50 mV / s for 10 to 30 cycles to form a molecularly imprinted film.

[0127] After forming the molecularly imprinted film, cortisol was eluted by overpolymerization for 20 cycles in PBS solution at pH 7.4 at a scan rate of 50 mV / s within the range of -0.2 V to 0.8 V. Alternatively, ethanol immersion can be used to elute the cortisol template molecules, thereby forming a molecularly imprinted template for cortisol.

[0128] Traditional sensors used for sweat detection suffer from short lifespans with prolonged wear. Conventional biochemical monitoring and specific identification of biosensitive membranes (such as enzymes or antibodies) loses activity over extended periods, necessitating more suitable analyte-sensitive identification methods. However, the detection electrode in this embodiment, after the aforementioned modification, can undergo molecular imprinting reactions, extending the lifespan of the sweat microfluidic sensor.

[0129] After the electrode layer is modified, a flow control channel 6 and a side flow control cavity 5 are formed on the substrate layer 1. Please refer to the description in Example 1 above for details, which will not be repeated here.

[0130] Next, the flow control channel 6 and the side flow control cavity 5 are hydrophilically modified. Before hydrophilic modification, a protective film can be used to cover the electrode layer 2 to eliminate hydrophilicity. Plasma oxygenation modification is used to increase hydrophilicity, and further hydrophilic modification is performed with 0.1% Tween 20 diluted liquid. After hydrophilic modification, the protective film is removed. Then, a thermosensitive gel layer 14 is modified on each heating electrode 205, such as... Figure 4 As shown. The thermosensitive gel hydrolyzes at 40-45 degrees Celsius and solidifies at room temperature. Therefore, the heating electrode 205 can be heated sequentially according to flow control needs, so that the flow control channel 6 is opened as needed. This heating procedure will increase energy consumption to some extent, but since the flow control channel is on the micrometer to millimeter scale, the required energy consumption is not significant. The thermosensitive gel can be azo hydrogel, etc., with a critical decomposition temperature of about 40-45 degrees Celsius, which is very gentle and will not cause skin damage.

[0131] The subsequent steps in the preparation method of the sweat microfluidic sensor in this embodiment are the same as those in the preparation method in Embodiment 1 above, and will not be repeated here.

[0132] In this embodiment, the sweat microfluidic sensor was tested using electrochemical DPV and IT methods. DPV: potential ranges from -0.4V to 0.6V, amplitude is 0.05V, pulse width is 0.06s, and potential increment is 0.004V.

[0133] Example 3

[0134] Combination Figure 1 , Figure 2 as well as Figures 6-10 As shown, the preparation method of the sweat microfluidic sensor in this embodiment is similar to that of the sweat microfluidic sensor in Embodiment 1 above, except that the modification method of the detection electrode is different, and the hydrophilic and hydrophobic modification methods of the flow control channel and the side flow control cavity are different.

[0135] Specifically, the modification method for the detection electrode 201 in this embodiment includes the following steps:

[0136] First, the detection electrode 201 was modified with nanoparticles, which can be achieved through the electrodeposition of gold nanoparticles. A 1 mM solution of chloroauric acid (HAuCl4) was prepared using deionized water. Then, using a three-electrode system (Pt wire electrode - counter electrode, silver / silver chloride (Ag / AgCl) electrode - reference electrode, carbon electrode - working electrode (i.e., detection electrode)), AuNPs were deposited on the surface of the detection electrode using electrochemical deposition technology. The deposition potential was set to -0.3 V, and the electrodeposition time was 500 s.

[0137] Then, the detection electrode 201 is modified with a mediator, a conductive medium, and template molecules. The mediator modification uses polypyrrole, Prussian blue, PEDOT-PSS, polythionine, or polyaniline to modify the detection electrode 201 to improve the electron transport efficiency of the detection electrode 201.

[0138] In this embodiment, the sweat microfluidic sensor is a multi-parameter detection sensor, meaning that each side flow control cavity region 100 is provided with a first detection electrode 201-1 and a second detection electrode 201-2, such as... Figure 8 As shown. The modification method for the first detection electrode 201-1 includes:

[0139] Polypyrrole, Prussian blue, and cortisol were co-electrodeposited onto the surface of the first detection electrode 201-1. A mixture of 20 mM pyrrole, 5 mM Prussian blue solution (10 mM FeCl3, 10 mM K3[Fe(CN)6], 1 mM to 100 mM HCl and 1 mM KCl) and 1 mM to 10 mM cortisol was formed. PBS at pH 7.4 was used as the supporting electrolyte solution, and electrodeposition was performed in the range of -0.2 V to 0.9 V. Electropolymerization was carried out at a scan rate of 50 mV / s for 10 to 30 cycles to form a molecularly imprinted film.

[0140] After forming the molecularly imprinted film, cortisol was eluted by using PBS at pH 7.4 as the supporting electrolyte solution and undergoing overpolymerization for 20 cycles at a scan rate of 50 mV / s within the range of -0.2V to 0.8V, thereby forming a molecularly imprinted template for cortisol.

[0141] When testing cortisol, electrochemical DPV and IT methods are used.

[0142] The modification method for the second detection electrode 201-2 includes:

[0143] First, the second detection electrode 201-2 was modified with nanoparticles, which could be achieved by electrodeposition using gold nanoparticles. A 1 mM chloroauric acid (HAuCl4) solution was prepared using deionized water. Then, an electrochemical deposition technique was used to deposit AuNPs on the surface of the second detection electrode 201-2 using a three-electrode system (Pt wire electrode - counter electrode, silver / silver chloride (Ag / AgCl) electrode - reference electrode, and carbon electrode - working electrode (i.e., detection electrode)). The deposition potential was -0.3 V, and the electrodeposition time was 500 s.

[0144] Then, 2 μL-10 μM of the first IL-6 aptamer solution was added dropwise to the detection electrode modified with gold nanoparticles, and the reaction was carried out at 4 °C for 7 hours. Afterward, the unbound aptamer solution was washed away with deionized water, and the detection electrode surface was allowed to dry to obtain the aptamer-modified detection electrode. Finally, 20 μL-1 mM of MCH solution was transferred to the second detection electrode 201-2 using a pipette, and the binding reaction was carried out at room temperature for 1.5 hours to block the remaining active sites on the gold nanoparticles. The unbound MCH was then washed away with deionized water.

[0145] In addition, a second IL-6 aptamer is pre-immobilized in the sweat collection area 3 to pre-react with IL-6 in the sweat. When the sweat flows into the side flow control cavity 5, it binds with the first IL-6 aptamer immobilized on the second detection electrode 201-2 to form a sandwich reaction, thereby improving the sensitivity of the sweat microfluidic sensor in detecting IL-6 protein.

[0146] In this embodiment, two modification methods, molecular imprinting and aptamer, were used for the first detection electrode 201-1 and the second detection electrode 201-2, respectively, so that the prepared sweat microfluidic sensor has the characteristics of high sensitivity, long service life and high temperature storage resistance.

[0147] The method for hydrophilic and hydrophobic modification of the flow control channel 6 and the side flow control cavity 5 in this embodiment includes the following steps:

[0148] Before hydrophilic modification, a protective film is first used to cover the hydrophobic part of the flow control channel 6 and the electrode layer 2 to eliminate hydrophilic effects. Then, plasma oxygenation modification is used to increase hydrophilicity, and SDS diluted liquid is used for further hydrophilic modification.

[0149] The protective film is then removed, and hydrophobic modification is performed using PDMS. The PDMS is premixed to form a liquid, and an appropriate amount of 0.1-2 μL is added to the hydrophobic part of the flow channel 6 using a pipette. After drying overnight, it becomes a U-shaped stepped hydrophobic film 601'.

[0150] In addition, the hydrophobic portion can be further modified with 95% DDM for 30 seconds.

[0151] The other steps in the preparation method of the sweat microfluidic sensor in this embodiment are the same as those in the preparation method in Embodiment 1 above, and will not be repeated here.

[0152] When using the sweat microfluidic sensor of this embodiment to test IL-6 protein, the electrochemical DPV method is used for testing. Specifically, the DPV has a potential of -0.4V to 0.6V, an amplitude of 0.05V, a pulse width of 0.06s, and a potential increment of 0.004V.

[0153] The sweat microfluidic sensor in this embodiment features a low detection limit and a wide linear range, achieving a detection limit of 1 pM to 10 μM for cortisol and 1 pM for IL-6. This sweat microfluidic sensor is suitable for detecting substances at extremely low concentrations.

[0154] Example 4

[0155] Combination Figures 1-10 As shown, the preparation method of the sweat microfluidic sensor in this embodiment is similar to that of the sweat microfluidic sensor in Embodiment 1 or Embodiment 2 above. The only difference is that, based on Embodiment 1 or Embodiment 2 above, this embodiment also has a test strip 10 fixed in at least a portion of the side flow control cavity 5 for detecting the corresponding parameters in the sweat.

[0156] Specifically, after hydrophilic / hydrophobic modification of the flow control channel 6 and the side flow control cavity 5, two test strips 10 are placed in each side flow control cavity 5. The test strips 10 are on the same layer as the detection electrode 201 and spaced apart from each other. Each test strip 10 includes a sample pad 101, a detection band 102 and a quality control band 103. The sample pad 101 contains labeled antibodies, the detection band 102 contains aptamers adapted to the labeled antibodies, and the quality control band 103 contains anti-antibodies.

[0157] The test strip 10 is prepared using a standard gold-labeled test strip preparation method. Due to the low amount of sweat secretion, the size of the gold-labeled test strip is proportionally reduced to one-third to one-tenth of the normal size. However, the height of the test band 102 and the control band 103 remains normal to facilitate sufficient binding reaction and observation. An aptamer is used instead of an antibody on the test band 102. Aptamers have better temperature stability than antibodies, thus improving temperature stability and reducing preparation costs.

[0158] Cortisol antibody and IL-6 antibody are immobilized on the sample pads (colloidal gold binding pads) 101 of the two test strips 10 to bind to the analyte. Cortisol aptamers and IL-6 aptamers are immobilized on the detection bands 102 of the two test strips 10 to capture the analyte. Anti-antibodies are pre-immobilized on the control bands 103 of both test strips 10 to detect the effectiveness of the labeled antibodies. In this embodiment, detection is performed using the test strips 10, and the concentration of the analyte can be reflected by visually observing color changes.

[0159] The other steps in the preparation method of the sweat microfluidic sensor in this embodiment are the same as those in the preparation methods of Embodiment 1 or Embodiment 2 above, and will not be repeated here.

[0160] Example 5

[0161] Combination Figure 1 , Figure 2 as well as Figures 6-9 As shown, the preparation method of the sweat microfluidic sensor in this embodiment is similar to that of the sweat microfluidic sensor in Embodiment 1 above, except that the modification method of the detection electrode is different, and the hydrophilic and hydrophobic modification methods of the flow control channel and the side flow control cavity are different.

[0162] Specifically, the modification method for the detection electrode 201 in this embodiment includes the following steps:

[0163] First, the detection electrode 201 was modified with nanoparticles, which can be achieved through the electrodeposition of gold nanoparticles. A 1 mM chloroauric acid (HAuCl4) solution was prepared using deionized water. Then, using a three-electrode system (Pt wire electrode - counter electrode, silver / silver chloride (Ag / AgCl) electrode - reference electrode, carbon electrode - working electrode (i.e., detection electrode)), AuNPs were deposited on the surface of the detection electrode 201 using electrochemical deposition technology. The deposition potential was set to -0.3 V, and the electrodeposition time was 500 s.

[0164] Then, the detection electrode 201 is modified with a mediator, a conductive medium, and template molecules. For mediator modification, polypyrrole, Prussian blue, PEDOT-PSS, polythionine, or polyaniline are used to modify the detection electrode 201 to improve its electron transport efficiency.

[0165] Add 1 μL of Tween-20 to 1 mL of PEDOT:PSS solution, add 1 μL of PEDOT:PSS / Tween-20 mixed solution to each detection electrode 201, and dry at room temperature for 12 h.

[0166] The detection electrode 201 was modified with ion-selective reagents. For sodium ion detection, the sodium ion carrier consisted of deionized water (1% wt / wt), NaTFPB (0.55% wt / wt), PVC (33% wt / wt), and DOS (65.45% wt / wt). The potassium ion-selective membrane mixture consisted of valine (2.4% wt / wt), potassium tetraborate KTCIPB (0.5% wt / wt) as the ion exchanger, PVC (32.5% wt / wt) as the polymer, and DOS (64.6% wt / wt) as the plasticizer.

[0167] Dissolve 100 mg of the membrane mixture in 360 μL of cyclohexanone, stir for 30 min, and then sonicate for 30 min to ensure complete dissolution. Add 1 μL of the mixed sodium ion-selective membrane mixture to the corresponding position on the detection electrode and bake in an oven at 90 °C for 2 hours. Before measurement, covering the detection electrode with a solution containing 0.1 mol / L NaCl for 1 hour can effectively reduce the occurrence of measurement potential drift.

[0168] The detection electrode in this embodiment can have its detection parameter range broadened by the above-mentioned modifications such as ion detection.

[0169] The method for hydrophilic and hydrophobic modification of the flow control channel 6 and the side flow control cavity 5 in this embodiment includes the following steps:

[0170] Before hydrophilic modification, a protective film is first used to cover the hydrophobic part of the flow control channel 6 and the electrode layer 2 to eliminate hydrophilic effects. Then, plasma oxygenation modification is used to increase hydrophilicity, and 0.1% Tween 20 diluted liquid is used for further hydrophilic modification.

[0171] The protective film is then removed, and hydrophobic modification is performed using PDMS. The PDMS is premixed to form a liquid, and an appropriate amount of 0.1-2 μL is added to the hydrophobic part of the flow channel 6 using a pipette. After drying overnight, it becomes a U-shaped stepped hydrophobic film 601'.

[0172] In addition, the hydrophobic portion can be further modified with 95% DDM for 30 seconds.

[0173] The other steps in the preparation method of the sweat microfluidic sensor in this embodiment are the same as those in the preparation method in Embodiment 1 above, and will not be repeated here.

[0174] In this embodiment, the sweat microfluidic sensor uses the open-circuit potential method for detection.

[0175] In addition, the detection electrode can also be modified with glucose oxidase, lactate oxidase / lactate dehydrogenase, etc., to detect glucose, lactate, etc. in sweat. The detection is performed using the electrochemical chronoamperometry method.

[0176] The sweat microfluidic sensor of this invention enables sequential flow control of sweat, thereby avoiding the mixing of new and old sweat. The sequentially collected sweat flows successively onto multiple detection electrodes and / or test strips, enabling in-situ detection of sweat hormones and proteins at different time points. Simultaneously, the sweat rate electrode can monitor sweat secretion rate in real time. In non-natural sweating conditions, combined with a sweat drug electro-osmosis enhancement module, it can stimulate sweat secretion and achieve sequential collection.

[0177] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sweat microfluidic sensor, characterized in that, It includes a substrate layer and an electrode layer located on the substrate layer, the electrode layer including detection electrodes; The substrate layer is provided with a sweat collection area, a waste liquid collection area, N side flow control cavities, and N+1 flow control channels, where N is a positive integer greater than or equal to 2. The sweat collection area and the waste liquid collection area are arranged opposite each other at one end of the substrate layer. The N side flow control cavities are distributed at intervals between the sweat collection area and the waste liquid collection area, and the detection electrode is correspondingly arranged in each side flow control cavity. The sweat collection area and the waste liquid collection area are connected by N+1 flow control channels connected end to end in sequence. The first N flow control channels near the sweat collection area are respectively connected to the N side flow control cavities. The first ends of the second flow control channel to the N+1 flow control channel are provided with buffer barriers. The parts of the N+1 flow control channels other than the buffer barriers and the N side flow control cavities are all hydrophilic areas. The buffer barrier region is hydrophobic. Under the hydrophilic-hydrophobic interaction, sweat flows sequentially from the sweat collection area through the flow control channel and enters the corresponding side flow control cavity. The sweat parameters are detected by the detection electrode. Alternatively, the buffer barrier region is provided with a heating electrode and a thermosensitive gel layer. The heating electrode is located on the electrode layer, and the thermosensitive gel layer is located on the heating electrode. Multiple heating electrodes are turned on sequentially. The corresponding thermosensitive gel layer dissolves upon heating, thereby opening the corresponding flow control channel. Sweat flows sequentially from the sweat collection area through the flow control channel and enters the corresponding side flow control cavity. The sweat parameters are detected by the detection electrode.

2. The sweat microfluidic sensor according to claim 1, characterized in that, Each of the side flow control cavities is further provided with a water-absorbing layer, which is located at the end of the side flow control cavity away from the flow control channel, and the orthographic projection of the water-absorbing layer on the substrate layer at least partially overlaps with the orthographic projection of the detection electrode on the substrate layer.

3. The sweat microfluidic sensor according to claim 2, characterized in that, At least a portion of the side flow control cavity is further provided with a test strip, which is used to detect parameters of sweat. The test strip includes a sample pad, a test strip and a control strip. The sample pad is provided with a labeled antibody, the test strip is provided with an aptamer adapted to the labeled antibody, and the control strip is provided with an anti-antibody. The test strip is disposed in the same layer as the detection electrode, and the orthographic projection of the absorbent layer on the substrate layer at least partially overlaps with the orthographic projection of the test strip on the substrate layer.

4. The sweat microfluidic sensor according to claim 1, characterized in that, The electrode layer also includes multiple counter electrodes and a reference electrode. The reference electrode is disposed in the sweat collection area, and the multiple counter electrodes are disposed in the N side flow control cavities in a one-to-one correspondence. The other end of the substrate layer is provided with multiple electrode interfaces, and the detection electrode, the counter electrode and the reference electrode are respectively connected to the multiple electrode interfaces one by one.

5. The sweat microfluidic sensor according to claim 4, characterized in that, The electrode layer also includes multiple sweat rate electrodes, which are disposed one-to-one in the N side flow control cavities. The sweat rate electrodes are used to monitor the amount and rate of sweat secretion. The sweat rate electrodes are located at one end of the side flow control cavity near the flow control channel, and the multiple sweat rate electrodes are connected in series with each other and connected to the corresponding electrode interface.

6. The sweat microfluidic sensor according to any one of claims 1-5, characterized in that, A sweat drug electro-permeability enhancement module is also provided on the base layer. The sweat drug electro-permeability enhancement module is located in the sweat collection area. The sweat drug electro-permeability enhancement module includes a permeability enhancement gel layer and a permeability enhancement electrode. The permeability enhancement gel layer includes a gel material and a permeability enhancement agent. The permeation-promoting gel layer is provided with multiple sweat-guiding grooves, one end of each of the multiple sweat-guiding grooves extending toward the flow control channel.

7. A method for preparing a sweat microfluidic sensor, characterized in that, Includes the following steps: Step 1, provide a base layer, on which a sweat collection area and a waste liquid collection area are provided opposite to each other, and N side flow control chambers are located between the sweat collection area and the waste liquid collection area, where N is a positive integer greater than or equal to 2; Step 2: An electrode layer and an insulating layer are sequentially fabricated on the substrate layer. The electrode layer includes a detection electrode located in each of the side flow control cavity regions. The insulating layer exposes the electrode layer. Step 3: Prepare N side flow control cavities corresponding to the N side flow control cavity areas, and prepare N+1 flow control channels connected end to end between the sweat collection area and the waste liquid collection area. The sweat collection area and the waste liquid collection area are connected through the N+1 flow control channels, and the first N flow control channels near the sweat collection area are respectively connected to the N side flow control cavities. Step 4: The first ends of the second flow control channel to the N+1th flow control channel all include a buffer barrier area. The N+1 flow control channels, excluding the buffer barrier area, and the N side flow control cavities are hydrophilically modified. Step 5: Perform hydrophobic modification on the buffer barrier region; or, the electrode layer may further include a heating electrode disposed corresponding to the buffer barrier region, and prepare a thermosensitive gel layer on the heating electrode.

8. The method for preparing the sweat microfluidic sensor according to claim 7, characterized in that, It also includes the following steps: Step 6: Place the test strip in the side flow control cavity and fix it. The test strip is in the same layer as the detection electrode and is spaced apart from each other. The test strip includes a sample pad, a detection band and a control band. The sample pad contains a labeled antibody, the detection band contains an aptamer adapted to the labeled antibody, and the control band contains an anti-antibody.

9. The method for preparing the sweat microfluidic sensor according to claim 8, characterized in that, It also includes the following steps: Step 7: Prepare an absorbent layer in each of the side flow control cavities, wherein the absorbent layer is located at the end of the side flow control cavity away from the flow control channel, and the absorbent layer overlaps with at least a portion of the detection electrode and / or the test strip.

10. The method for preparing the sweat microfluidic sensor according to claim 9, characterized in that, In step 2, the formed electrode layer further includes a permeation-enhancing electrode located in the sweat collection area. The preparation method further includes the following steps: Step 8: Prepare a permeation-enhancing gel layer in the sweat collection area. The permeation-enhancing gel layer is located on the surface of the permeation-enhancing electrode. The permeation-enhancing gel layer includes a gel material and a permeation-enhancing agent.

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