Capacitive sweat detection sensor and preparation method thereof

Abstract

The invention provides a capacitive sweat detection sensor and a preparation method thereof. The method comprises the following steps: respectively preparing a hydrophobic film layer, a micro-channel layer and an electrode layer; sequentially pasting and assembling the hydrophobic film layer, the micro-channel layer and the electrode layer from top to bottom to form the capacitive sweat detection sensor, wherein the hydrophobic thin film layer comprises a super-hydrophobic nanowire thin film, an MA layer and a super-hydrophilic nanowire thin film formed on one side, far away from the super-hydrophobic nanowire thin film, of the MA layer; the electrode layer comprises an electrode substrate, an interdigital electrode and a separation layer which are arranged in sequence. The interference of external stress and ions in sweat on the detection result can be reduced, the detection precision of the sensor is improved, and the application scene is expanded.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and more particularly, to a capacitive sweat detection sensor and a preparation method thereof. Background Art

[0002] During exercise or extreme working environments, continuous and real-time monitoring of sweat loss is crucial for developing an appropriate hydration plan. Currently, sweat sensors used for sweat measurement primarily include capacitive and conductive types. However, microfluidic sensors with cross-electrodes based on conductivity have a simple structure and sensing mechanism, but the output comes from sweat passing through the leading edge of the electrode, making it discrete rather than continuous. Furthermore, the ion concentration in sweat can affect the sweat signal, leading to inaccurate measurements. Capacitive sweat sensors based on a vertical structure detect sweat flow between electrodes, where the medium changes from air to sweat, causing capacitance changes. However, these sensors are prone to errors under external stress.

[0003] As can be seen, both of the aforementioned sweat volume sensors have certain drawbacks. The capacitive type is easily affected by external forces, while the conductive type is easily affected by ions in sweat and produces discrete data. Therefore, accurately monitoring sweat volume without contact is a technical challenge that urgently needs to be addressed. Summary of the Invention

[0004] In view of the above problems, the purpose of the present invention is to provide a capacitive sweat detection sensor and a preparation method thereof to solve the problems existing in the existing sweat amount sensor detection, such as being easily affected by sweat ions or external forces, resulting in poor measurement accuracy.

[0005] The method for preparing a capacitive sweat detection sensor provided by the present invention comprises separately preparing a hydrophobic film layer, a microchannel layer, and an electrode layer;

[0006] The hydrophobic film layer, the microchannel layer and the electrode layer are sequentially pasted and assembled from top to bottom to form the capacitive sweat detection sensor; wherein,

[0007] The hydrophobic film layer includes a super-hydrophobic nanowire film, an MA layer, and a super-hydrophilic nanowire film formed on a side of the MA layer away from the super-hydrophobic nanowire film;

[0008] The electrode layer includes an electrode substrate, interdigital electrodes and a separation layer which are arranged in sequence.

[0009] In addition, an optional technical solution is that the preparation process of the hydrophobic film layer includes:

[0010] Preparing a P(VDF-HFP) precursor solution for forming the super-hydrophobic nanowire film, and forming the super-hydrophobic nanowire film based on an electrospinning method;

[0011] In-situ spinning of a MA layer using methyl acrylate on the super-hydrophobic nanowire film;

[0012] An SF precursor solution for forming the super-hydrophilic nanowire film is prepared, and the super-hydrophilic nanowire film is formed on the MA layer based on an electrospinning method.

[0013] In addition, an optional technical solution is that the preparation process of the SF precursor solution includes:

[0014] Cut the cocoons into pieces and add them into NaCO3 solution and boil for a preset time;

[0015] The boiled silk is washed with deionized water and dried;

[0016] The cleaned and dried silk was added to the degummed silk, formic acid and CaCl2 and mechanically stirred. The excess solution was removed and the silk was placed in a fume hood to dry naturally.

[0017] The air-dried silk was placed in a preset dialysis bag, dialyzed with deionized water for a preset time, and then taken out and air-dried to obtain silk protein;

[0018] The silk protein, formic acid and polyethylene oxide are stirred until the silk protein particles are completely dissolved to form the SF precursor solution.

[0019] In addition, an optional technical solution is that the preparation process of the microfluidic layer includes:

[0020] Prepare a microfluidic template, and mix PDMS and a curing agent according to a preset ratio to obtain a PDMS liquid;

[0021] Pour the PDMS liquid into the microfluidic channel template and apply scraping to obtain a basic microfluidic channel;

[0022] The basic microfluidic channel is pretreated to form the microfluidic channel layer.

[0023] In addition, an optional technical solution is that the pretreatment includes: performing oxygen plasma treatment on the basic microchannel, and performing hydrophilic treatment on the channels of the treated basic microchannel to make the channels inside the microchannel layer hydrophilic and the channels outside hydrophobic.

[0024] In addition, an optional technical solution is that the preparation process of the electrode layer includes:

[0025] preparing an electrode substrate and screen printing ink, and placing a preset screen plate on the electrode substrate;

[0026] Printing the screen printing ink on the electrode substrate through the screen plate to form the interdigitated electrodes;

[0027] The interdigital electrodes are cleaned with deionized water and dried, and a separation layer is attached to the surface of the interdigital electrodes to form the electrode layer.

[0028] In addition, an optional technical solution is that the preparation process of the screen printing ink includes:

[0029] Mixing polyethylene oxide, anhydrous ethanol and deionized water in a preset ratio to form a mixed solution;

[0030] Silver nanowires are added to the mixed solution and stirring is continued until the screen printing ink is formed.

[0031] In addition, an optional technical solution is that the microfluidic layer is provided with a liquid inlet, a liquid storage tank and a liquid outlet that are interconnected, and at least one of the liquid inlet and the liquid outlet is provided;

[0032] The non-channel position of the micro-channel layer is attached to the interdigital electrodes, and the channel position of the micro-channel layer corresponds to the inter-electrode gap of the interdigital electrodes in a vertical direction.

[0033] In addition, an optional technical solution is that the thickness of the microfluidic layer ranges from 400 to 800 μm;

[0034] The depth range of the flow channel is: 100 to 300 μm;

[0035] The width of the flow channel ranges from 1 to 1.5 cm.

[0036] In another aspect, the present invention further provides a capacitive sweat detection sensor, which is prepared using the above-mentioned capacitive sweat detection sensor preparation method; wherein the capacitive sweat detection sensor comprises a hydrophobic film layer, a microchannel layer, and an electrode layer stacked together;

[0037] The hydrophobic film layer includes a super-hydrophobic nanowire film, an MA layer disposed on the super-hydrophobic nanowire film, and a super-hydrophilic nanowire film formed on a side of the MA layer away from the super-hydrophobic nanowire film;

[0038] The electrode layer includes an electrode substrate, an interdigitated electrode and a separation layer arranged in sequence;

[0039] The microfluidic channel layer is located between the super-hydrophilic nanowire film and the separation layer;

[0040] The interdigital electrodes are used to detect the amount of sweat flowing through the microchannel layer.

[0041] The above-mentioned capacitive sweat detection sensor and its preparation method are used to solve the problem that the capacitance signal of the vertical structure sweat sensor is easily affected by strain by combining planar interdigitated electrodes with microchannels. At the same time, the ultra-thin separation layer and microchannels are used to avoid the interference of ions in sweat on signal detection, and the capacitance measurement of non-contact electrodes and sweat flowing in the microfluidic is realized, thereby achieving the effect of sweat amount detection.

[0042] In order to achieve the above and related purposes, one or more aspects of the present invention include the features that will be described in detail later. The following description and the accompanying drawings describe some exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all of these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] By referring to the following description in conjunction with the accompanying drawings, and with a more complete understanding of the present invention, other objects and results of the present invention will become more clear and easy to understand. In the accompanying drawings:

[0044] Figure 1 2 is a schematic structural diagram of a capacitive sweat detection sensor according to an embodiment of the present invention;

[0045] Figure 2 is a schematic structural diagram of a microfluidic layer according to an embodiment of the present invention;

[0046] Figure 3 Schematic diagram of the structure of the combination of interdigitated electrodes and a microfluidic layer according to an embodiment of the present invention;

[0047] Figure 4 is a graph showing the relationship between sweat volume and capacitance change according to an embodiment of the present invention;

[0048] Figure 5 is a diagram showing a relationship between stress capacitance changes according to an embodiment of the present invention;

[0049] Figure 6 Graph showing the relationship between different sweat ion concentrations and capacitance changes according to an embodiment of the present invention.

[0050] The reference numerals in the above figures include: electrode substrate 1 , interdigitated electrode 2 , separation layer 3 , microchannel layer 4 , super-hydrophilic nanowire film 5 , MA layer 6 , super-hydrophobic nanowire film 7 .

[0051] The same reference numerals throughout the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0052] In the following description, for illustrative purposes, numerous specific details are set forth to provide a comprehensive understanding of one or more embodiments. However, it will be apparent that the embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form to facilitate description of one or more embodiments.

[0053] It will be understood by those skilled in the art that, unless otherwise stated, the singular forms "a," "an," "said," and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the stated features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that the term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0054] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including material terms and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art in the art to which the present invention pertains. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless defined as such herein, will not be interpreted in an idealized or overly formal sense.

[0055] To describe the capacitive sweat detection sensor and its manufacturing method in detail, the following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings.

[0056] Figure 1 and Figure 3 The schematic structure of the capacitive sweat detection sensor according to an embodiment of the present invention is shown from different angles.

[0057] like Figures 1 to 3 As shown together, the capacitive sweat detection sensor (referred to as the sensor, the same below) of the embodiment of the present invention includes: first, preparing a hydrophobic film layer, a microfluidic layer 4 and an electrode layer respectively; then, in order from top to bottom, the hydrophobic film layer, the microfluidic layer 4 and the electrode layer are sequentially pasted and assembled to form a capacitive sweat detection sensor; wherein, the hydrophobic film layer includes a super-hydrophobic nanowire film 7, an MA layer 6, and a super-hydrophilic nanowire film 5 formed on the side of the MA layer 6 away from the super-hydrophobic nanowire film 7; the electrode layer includes an electrode substrate 1, interdigitated electrodes 2 and a separation layer 3 arranged in sequence. During the detection process, when liquids such as sweat are transmitted through the microfluidic layer 4, the separation layer 3 can eliminate the interference of the ion concentration in the sweat on the capacitive signal of the interdigitated electrode 2, thereby realizing non-contact sweat detection.

[0058] The preparation process of the hydrophobic film layer includes:

[0059] S101: preparing a P(VDF-HFP) precursor solution for forming a super-hydrophobic nanowire film, and forming the super-hydrophobic nanowire film based on an electrospinning method;

[0060] S102: In situ spinning of MA layer using methyl acrylate on superhydrophobic nanowire film;

[0061] S103: preparing an SF precursor solution for forming a super-hydrophilic nanowire film, and forming a super-hydrophilic nanowire film on the MA layer based on an electrospinning method.

[0062] Specifically, the P(VDF-HFP) precursor solution can be prepared by mixing P(VDF-HFP) and N,N-dimethylformamide (DMF) in a mass ratio of 1:4 and heating and stirring them uniformly, and the MA layer is obtained by electrospinning methyl acrylate.

[0063] In a specific embodiment of the present invention, the preparation process of the SF precursor solution includes:

[0064] S1031: Cut the cocoons into pieces and add them into a NaCO3 solution and continue boiling for a preset time;

[0065] S1032: washing the boiled silk with deionized water and drying it;

[0066] S1033: adding the cleaned and dried silk to the degummed silk, formic acid and CaCl2, mechanically stirring, removing excess solution and placing the silk in a fume hood to dry naturally;

[0067] S1034: placing the air-dried silk into a preset dialysis bag, dialyzing the silk with deionized water for a preset time, and then taking it out and air-drying it to obtain silk protein;

[0068] S1035: Stir the silk protein, formic acid and polyethylene oxide until all the silk protein particles are dissolved to form a SF precursor solution.

[0069] Specifically, the cocoons were chopped into pieces and added to a 5wt% NaCO3 solution with a water-bath ratio of 50:1, and boiled at 100°C for at least 30 minutes. The silk was then washed with deionized water and dried. After washing and drying, 5wt% degummed silk, 92wt% formic acid and 3wt% CaCl2 were added. After mechanical stirring for four hours, the excess solution was removed and the solution was placed in a fume hood to dry naturally.

[0070] Then, the dialysis bag was placed in boiling deionized water for 10 minutes, and then the air-dried silk protein was placed in the dialysis bag, dialyzed with deionized water for 24 hours, and then taken out and air-dried to obtain silk protein; finally, 15wt% of the obtained silk protein, 85wt% of formic acid, and 2wt% of polyethylene oxide (PEO) of the silk protein were added and stirred until all the silk protein particles were dissolved to prepare the SF precursor solution.

[0071] Among them, based on the SF precursor solution, a superhydrophilic nanowire film (SF film for short) is formed on the MA layer by electrospinning. It can also be processed, that is, the spun SF membrane is placed in glycerol and placed in a 60°C oven for one hour. After treatment, it is washed with deionized water, and then the SF membrane is soaked in deionized water for 12 hours to remove PEO, thereby obtaining a high-quality hydrophilic film.

[0072] In addition, the preparation process of the microfluidic layer 4 in the embodiment of the present invention includes:

[0073] S201: preparing a microfluidic template, and mixing PDMS and a curing agent according to a preset ratio to obtain a PDMS liquid; wherein, a photosensitive resin can be used to 3D print the microfluidic template.

[0074] S202: Pour PDMS liquid into the microfluidic channel template and apply scraping to obtain a basic microfluidic channel;

[0075] S203: Pre-treating the basic microfluidic channel to form a microfluidic channel layer.

[0076] Specifically, the pretreatment may include: performing oxygen plasma treatment on the basic microfluidic channel, and performing hydrophilic treatment on the treated channels of the basic microfluidic channel, so as to make the inside of the channels of the microfluidic channel layer hydrophilic and the outside of the channels hydrophobic.

[0077] In addition, the preparation process of the electrode layer in the embodiment of the present invention includes:

[0078] S301: preparing an electrode substrate and screen printing ink, and placing a screen plate with a preset structure on the electrode substrate;

[0079] S302: Printing screen printing ink on the electrode substrate through a screen plate to form interdigitated electrodes;

[0080] S303: Cleaning and drying the interdigital electrodes with deionized water, and attaching a separator layer to the surface of the interdigital electrodes to form an electrode layer.

[0081] The preparation process of the screen printing ink includes:

[0082] S3011: Mixing and stirring polyethylene oxide, anhydrous ethanol, and deionized water according to a preset ratio to form a mixed solution;

[0083] S3012: Add silver nanowires to the mixed solution and continue stirring until screen printing ink is formed.

[0084] Specifically, the screen printing ink can be prepared by mixing polyethylene oxide (PEO), anhydrous ethanol, and deionized water in a mass ratio of 1:10:10 and stirring until the solution is uniformly mixed, and then adding AgNWs, wherein the mass ratio of AgNWs to PEO mixed solution (i.e., polyethylene oxide (PEO), anhydrous ethanol, and deionized water mixed and stirred in a mass ratio of 1:10:10) is 3:1.

[0085] In the sensor of the present invention, the microfluidic layer is provided with a liquid inlet, a liquid reservoir, and a liquid outlet that are interconnected, with at least one liquid inlet and outlet provided. The non-fluidic portion of the microfluidic layer is attached to the interdigitated electrodes, and the flow channel portion of the microfluidic layer corresponds vertically to the inter-electrode gaps of the interdigitated electrodes. Furthermore, the thickness of the microfluidic layer ranges from 400 to 800 μm; the depth of the flow channel ranges from 100 to 300 μm; and the width of the flow channel ranges from 1 to 1.5 cm.

[0086] Specifically, the electrode substrate can be prepared using the method for preparing a superhydrophobic nanowire film. In other words, the electrode substrate can be prepared at the same time as the superhydrophobic nanowire film is prepared, and then used as the electrode substrate to arrange the interdigitated electrodes; or the electrode substrate can be re-prepared using the method for preparing a superhydrophobic nanowire film during the preparation of the electrode layer.

[0087] As a specific example, the thickness of the electrode base is 2000μm, the interdigital electrode includes: five pairs of fingers, with a finger width of 1mm and a finger spacing of 1.5mm. The electrode thickness is 50μm, and the separating layer is made of 8μm PE film, which is attached to the surface of the interdigital electrode to isolate the influence of sweat on the detection quotation marks.

[0088] In a specific embodiment of the present invention, step S101 and step S102 may specifically include:

[0089] 1. Mix 2 g of P(VDF-HFP) and 8 g of DMF and stir at 70°C and 600 rpm (revolutions per minute) for 4 to 6 hours to obtain a P(VDF-HFP) precursor solution.

[0090] 2. Use a 5ml disposable syringe to draw 5ml of the solution obtained in step 1. Install a 20G electrospinning metal needle in the syringe and place the syringe on the fixed stage of the electrospinning machine. Use aluminum foil to collect the sample at the roller collector end. Adjust the distance between the needle and the roller collector to 10cm. Set the front dead center and displacement midpoint, respectively. The injection speed is 0.3mm / min, the roller receiver speed is 100r / min, and the voltage is 1.4kV / cm. After spinning begins, a Taylor cone-shaped microjet can be observed under direct light. Once the jet stabilizes, turn off the direct light and electrospin for 5 hours at room temperature to obtain a superhydrophobic nanowire film 7. Subsequently, a MA layer is in situ spun on top of the film using methyl acrylate. The electrospinning parameters for the MA layer are 1kV / cm, a needle distance of 10cm, a propulsion speed of 0.01mm / min, a temperature of 25°C to 30°C, and a humidity of 40% to 60%. The needle is a 5ml syringe with a 23G needle.

[0091] The step S103 of preparing the super-hydrophilic nanowire film may specifically include:

[0092] 1. Prepare the silk fibroin film (SF) precursor solution: Shred silkworm cocoons and add them to a 5wt% NaCO3 solution at a water-bath ratio of 50:1. Boil at 100°C for 30 minutes, then rinse the silk three times with deionized water. After drying, add 5wt% of the degummed silk to 92wt% formic acid and 3wt% CaCl2 and mechanically stir for four hours. Pour the stirred solution into a Petri dish and air-dry in a fume hood for 24 hours. Dialysis: Place a dialysis bag in boiling deionized water for 10 minutes, then place the air-dried silk fibroin into a dialysis bag and dialyze it with deionized water for 24 hours. Then, pour the dialyzed silk fibroin out and air-dry. Prepare the spinning solution: Stir silk fibroin (15wt%), formic acid (85wt%), and polyethylene oxide (PEO = 2wt% of the silk fibroin) until all the silk fibroin particles are dissolved to create the SF precursor solution.

[0093] 2. Use a 5ml disposable syringe to draw 10ml of SF precursor solution, install a 23G electrospinning metal needle on the syringe, place the syringe on the fixed table of the electrospinning machine, use aluminum foil to collect the roller collector end, adjust the distance between the needle and the roller collector to 10cm, set the front dead point and displacement midpoint respectively, the injection speed is 0.11mm / min, the roller receiver speed is 100r / min, the voltage is 1.4kV / cm, and after starting spinning, a Taylor cone-shaped microjet can be observed under direct light. After the jet stabilizes, turn off the direct light and electrospin for 8 hours at room temperature to obtain a superhydrophilic nanowire film.

[0094] In addition, the preparation process of the microfluidic layer may specifically include:

[0095] 1. Use photosensitive resin as 3D printing material to 3D print the microfluidic template. Add isopropyl alcohol to the printed template and ultrasonically clean it for 30 minutes. After ultrasonic cleaning, put it into a UV curing machine and irradiate it with UV light to completely cure the template surface.

[0096] 2. Mix PDMS and curing agent in a ratio of 10:1 and stir for 10 minutes. After stirring, vacuum it to remove bubbles, and pour the vacuumed PDMS into the microfluidic template for scraping. After scraping, put it in a 60℃ oven to cure for 6 hours. Finally, peel off the microfluidic channel to obtain the PDMS microfluidic film (i.e., microfluidic layer), whose size is as follows: Figure 2 shown.

[0097] 3. The microchannels prepared in step 2 were treated with oxygen plasma at 200W for 3 minutes at 600 mtorr. After treatment, a hydrophilic material (10-20 wt% PVP) was pipetted into the channels, making the interior hydrophilic and the exterior hydrophobic, allowing sweat to flow between the interdigitated electrodes.

[0098] In addition, the preparation process of the electrode layer may specifically include:

[0099] 1. Prepare screen printing ink: The screen printing ink is made by mixing polyethylene oxide (PEO), anhydrous ethanol, and deionized water in a mass ratio of 1:10:10. Stir for 24 hours until the solution is uniformly mixed. Then add AgNWs (silver nanowires). The AgNWs:PEO mixed solution is 3:1. Stir for 30 minutes before printing.

[0100] 2. The electrode substrate can be made of a superhydrophobic nanowire film. The printing process involves placing a screen plate on P(VDF-HFP), tilting the squeegee at 45°, and screen printing at a speed of 1 cm / s. After 10 back-and-forth strokes, an interdigitated electrode with a thickness of 50 μm is obtained.

[0101] 3. Rinse the interdigitated electrodes obtained in step 2 with deionized water for 30 minutes to remove PEO, thereby improving the electrode's conductivity. After rinsing, dry the electrodes and apply 8μm PE film (polyethylene film) to the interdigitated electrodes to isolate the capacitive signal from the effects of sweat.

[0102] Finally, the prepared parts are assembled in sequence, from bottom to top: hydrophobic film layer, microfluidic layer and electrode layer, to form a capacitive sweat detection sensor.

[0103] During the application process, the amount of sweat is measured by the assembled capacitive sweat detection sensor. Different sweat amounts are measured to obtain the law of sweat amount and capacitance change. Figure 4It can be seen that the capacitive sweat detection sensor prepared by the present invention has obvious responses to different sweat amounts (sweat is replaced by artificial sweat).

[0104] In addition, in order to verify that the capacitive sweat detection sensor is not affected by stress, the sweat sensor is placed under a universal test tensile machine and compressed with a force of 100N to measure its capacitance change. The results are as follows: Figure 5 As shown, the sensor performance is stable.

[0105] In addition, to verify that the sensor is not affected by the ion concentration in sweat, the capacitance signal was measured in deionized water and artificial sweat. A high-precision injection pump was used to simulate a sweat flow rate of 2μL / min, and the signal was measured at this speed. The results are as follows: Figure 6 It can be seen that the capacitive sweat detection sensor designed and prepared by the present invention is not affected by stress and ion concentration in sweat, and has a significant response to different sweat volumes. It is expected to be widely used in the fields of athlete health monitoring, heat stroke prevention, non-invasive medical monitoring, etc.

[0106] Corresponding to the above-mentioned method for preparing a capacitive sweat detection sensor, the present invention further provides a capacitive sweat detection sensor, which is prepared using the above-mentioned method for preparing a capacitive sweat detection sensor.

[0107] Specifically, the capacitive sweat detection sensor includes a stacked hydrophobic film layer, a microfluidic layer and an electrode layer; the hydrophobic film layer includes a superhydrophobic nanowire film, an MA layer arranged on the superhydrophobic nanowire film, and a superhydrophilic nanowire film formed on the side of the MA layer away from the superhydrophobic nanowire film; the electrode layer includes an electrode base, interdigitated electrodes and a separation layer arranged in sequence; the microfluidic layer is located between the superhydrophilic nanowire film and the separation layer; the interdigitated electrodes are used to detect the amount of sweat flowing through the microfluidic layer.

[0108] It should be noted that the embodiments of the above-mentioned capacitive sweat detection sensor can refer to the description in the embodiment of the method for preparing the capacitive sweat detection sensor, that is, the contents in the method and device embodiments can refer to each other and will not be repeated here.

[0109] According to the capacitive sweat detection sensor and its preparation method of the present invention, combined with a directional transport film, planar interdigitated electrodes are designed on a hydrophobic electrode substrate to eliminate the problem that the vertical structure is easily affected by external forces. At the same time, microchannels and separation layers are used to eliminate the influence of ion concentration in sweat on the capacitive signal. The sensor has a significant response to different sweat volumes, a simple preparation process, and strong anti-interference ability. It can be widely used in multiple fields such as athlete health monitoring, heat stroke prevention, and non-invasive medical monitoring.

[0110] The capacitive sweat detection sensor and its manufacturing method according to the present invention are described above by way of example with reference to the accompanying drawings. However, those skilled in the art will appreciate that various improvements may be made to the capacitive sweat detection sensor and its manufacturing method as described above without departing from the scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the contents of the appended claims.

Claims

1. A method for preparing a capacitive sweat detection sensor, characterized in that: include: preparing a hydrophobic film layer, a microfluidic channel layer and an electrode layer respectively; The hydrophobic film layer, the microchannel layer and the electrode layer are sequentially pasted and assembled from top to bottom to form the capacitive sweat detection sensor; wherein, The hydrophobic film layer includes a super-hydrophobic nanowire film, an MA layer, and a super-hydrophilic nanowire film formed on a side of the MA layer away from the super-hydrophobic nanowire film; The electrode layer includes an electrode substrate, interdigital electrodes and a separation layer which are arranged in sequence.

2. The method for preparing a capacitive sweat detection sensor according to claim 1, wherein: The preparation process of the hydrophobic film layer includes: Preparing a P(VDF-HFP) precursor solution for forming the super-hydrophobic nanowire film, and forming the super-hydrophobic nanowire film based on an electrospinning method; In-situ spinning of a MA layer using methyl acrylate on the super-hydrophobic nanowire film; An SF precursor solution for forming the super-hydrophilic nanowire film is prepared, and the super-hydrophilic nanowire film is formed on the MA layer based on an electrospinning method.

3. The method for preparing a capacitive sweat detection sensor according to claim 2, wherein: The preparation process of the SF precursor solution includes: Cut the cocoons into pieces and add them into NaCO3 solution and boil for a preset time; The boiled silk is washed with deionized water and dried; The cleaned and dried silk was added to the degummed silk, formic acid and CaCl2 and mechanically stirred. The excess solution was removed and the silk was placed in a fume hood to dry naturally. The air-dried silk was placed in a preset dialysis bag, dialyzed with deionized water for a preset time, and then taken out and air-dried to obtain silk protein; The silk protein, formic acid and polyethylene oxide are stirred until the silk protein particles are completely dissolved to form the SF precursor solution.

4. The method for preparing a capacitive sweat detection sensor according to claim 1, wherein: The preparation process of the microfluidic layer includes: Prepare a microfluidic template, and mix PDMS and a curing agent in a preset ratio to obtain a PDMS liquid; Pour the PDMS liquid into the microfluidic channel template and apply scraping to obtain a basic microfluidic channel; The basic microfluidic channel is pretreated to form the microfluidic channel layer.

5. The method for preparing a capacitive sweat detection sensor according to claim 4, wherein: The pretreatment includes: performing oxygen plasma treatment on the basic microfluidic channel, and performing hydrophilic treatment on the channels of the treated basic microfluidic channel, so as to make the channels inside the microfluidic channel layer hydrophilic and the channels outside hydrophobic.

6. The method for preparing a capacitive sweat detection sensor according to claim 1, wherein: The preparation process of the electrode layer includes: preparing an electrode substrate and screen printing ink, and placing a preset screen plate on the electrode substrate; Printing the screen printing ink on the electrode substrate through the screen plate to form the interdigitated electrodes; The interdigital electrodes are cleaned with deionized water and dried, and a separation layer is attached to the surface of the interdigital electrodes to form the electrode layer.

7. The method for preparing a capacitive sweat detection sensor according to claim 6, wherein: The preparation process of the screen printing ink comprises: Mixing polyethylene oxide, anhydrous ethanol and deionized water in a preset ratio to form a mixed solution; Silver nanowires are added to the mixed solution and stirring is continued until the screen printing ink is formed.

8. The method for preparing a capacitive sweat detection sensor according to claim 1, wherein: The microfluidic layer is provided with a liquid inlet, a liquid storage tank and a liquid outlet that are interconnected, and each of the liquid inlet and the liquid outlet is provided with at least one; The non-channel position of the micro-channel layer is attached to the interdigital electrodes, and the channel position of the micro-channel layer corresponds to the inter-electrode gap of the interdigital electrodes in a vertical direction.

9. The method for preparing a capacitive sweat detection sensor according to claim 8, wherein: The thickness of the microchannel layer is in the range of 400 to 800 μm; The depth range of the flow channel is: 100 to 300 μm; The width of the flow channel ranges from 1 to 1.5 cm.

10. A capacitive sweat detection sensor, characterized in that: It is prepared using the method for preparing a capacitive sweat detection sensor according to any one of claims 1 to 9; wherein, The capacitive sweat detection sensor comprises a hydrophobic film layer, a microchannel layer and an electrode layer which are stacked; The hydrophobic film layer includes a super-hydrophobic nanowire film, an MA layer disposed on the super-hydrophobic nanowire film, and a super-hydrophilic nanowire film formed on a side of the MA layer away from the super-hydrophobic nanowire film; The electrode layer includes an electrode substrate, an interdigitated electrode and a separation layer arranged in sequence; The microfluidic channel layer is located between the super-hydrophilic nanowire film and the separation layer; The interdigital electrodes are used to detect the amount of sweat flowing through the microchannel layer.

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