CN118614914A - A wearable sweat sensor for real-time sports health monitoring - Google Patents

Abstract

The invention relates to a wearable sweat sensor for real-time monitoring of sports health, which comprises a microfluidic chip, an electrochemical sensing module, a photoelectric detection module and a circuit control system. The electrochemical sensing module is arranged in the microfluidic chip, can be contacted with the sweat sample and is excited by target components in the sweat sample to generate an electric signal; the photoelectric detection module can record the light transmittance change caused by arterial pulsation hyperemia volumization; the electrochemical sensing module and the photoelectric detection module are both connected with the circuit control system, and are used for receiving instructions of the circuit control system and transmitting information to the circuit control system. The electrochemical sensing module can detect the concentration change of sweat ions and the concentration change of lactic acid; the photoelectric detection module can detect heart rate and maximum oxygen uptake, so that the continuous monitoring of sweat ion state, lactic acid state, heart rate and maximum oxygen uptake of a wearer can be realized simultaneously through the wearable sweat sensor, and scientific research or daily health care use is facilitated.

Description

A wearable sweat sensor for real-time sports health monitoring

Technical Field

The present invention belongs to the technical field of electrochemical method testing, and in particular relates to a wearable sensor comprising an ion selective electrode.

Background Art

As people pay more attention to health management, real-time monitoring and evaluation of individual physiological health parameters has become a key issue. The concentration of electrolytes and metabolites in sweat, as well as heart rate and maximum oxygen uptake, are one of the important indicators for measuring physical health and exercise performance. Real-time monitoring of these parameters through wearable devices can provide personalized health assessment and guidance to help people achieve better health and exercise goals. Sweat electrolyte monitoring can help people understand the loss of water and electrolytes during exercise, thereby guiding strategies for replenishing water and electrolytes and preventing exercise-induced dehydration and electrolyte disorders. Lactate concentration monitoring can assess the degree of muscle fatigue during exercise, help formulate reasonable training plans and adjust exercise intensity. Heart rate and maximum oxygen uptake monitoring can assess cardiovascular and pulmonary function, guide individual exercise intensity and training plans, and assess exercise effectiveness and health status. Real-time monitoring of these parameters can provide valuable information about physical condition and exercise load.

There are already some commercial wearable devices that can monitor parameters such as heart rate and blood oxygen saturation, such as the invention patent with patent number 2020800921679, and some wearable devices that detect sweating, such as the invention patents with patent numbers 2020204770675 and 2021109219508, but few devices can simultaneously monitor sweat electrolyte and metabolite concentrations. Therefore, the development of a multi-module wearable sensor device that simultaneously monitors health parameters such as electrolyte and metabolite concentrations in sweat, heart rate, and maximum oxygen uptake has broad application prospects and market demand.

Summary of the invention

In order to solve the above technical problems, the present invention provides a wearable sweat sensor for real-time monitoring of sports health.

The technical solution adopted by the present invention is: a wearable sweat sensor for real-time monitoring of sports health, comprising:

The microfluidic chip comprises a flexible base layer, a channel layer and a chip cover layer which are laminated in sequence, wherein a collection and detection chamber is provided in the channel layer, and sweat can pass through the flexible base layer and enter the collection and detection chamber;

The electrochemical sensing module is arranged on the flexible substrate layer, and includes electrically connected electrode points and connecting wires, wherein the electrode points are arranged to be exposed in the collection and detection chamber;

A photoelectric detection module, configured to record changes in light transmittance caused by arterial pulsation and hyperemia;

The circuit control system, the electrochemical sensing module and the photoelectric detection module are all connected to the power management circuit.

Preferably, the electrode points include a counter electrode, a reference electrode, an ion selective electrode and a lactate selective electrode;

Preferably, the ion selective electrode comprises one or more of a sodium ion solid selective electrode, a potassium ion solid selective electrode and a calcium ion solid selective electrode.

Preferably, the ion selective electrode comprises an electrode point and an ion selective membrane covering the electrode point; and the lactate selective electrode comprises an electrode point and a lactate selective membrane covering the electrode point.

Preferably, one or more sweat inlets are provided in the channel layer, and the sweat inlets are connected to the collection and detection chamber through the chip microchannel; sweat inlets are provided on the flexible base layer, and the number and position of the sweat inlets correspond to the sweat inlets.

Preferably, a waste liquid outlet is provided on the chip cover layer, and a waste liquid outlet is also provided at the channel layer corresponding to the position of the sweat waste liquid outlet, and the waste liquid outlet is connected to the collection and detection chamber through the chip microchannel.

Preferably, the circuit control system includes a front-end analog circuit, a first conversion circuit, a microcontroller circuit, a second conversion circuit and a power management circuit. The power management circuit is electrically connected to the front-end analog circuit, the first conversion circuit, the second conversion circuit and the microcontroller circuit. The front-end analog circuit is connected to the connecting wire in the electrochemical sensor module, the front-end analog circuit is connected to the first conversion circuit, and the photoelectric detection module is connected to the second conversion circuit; the first conversion circuit and the second conversion circuit are both connected to the microcontroller circuit.

Preferably, the received optical signal is converted into an electrical signal by a photoelectric conversion circuit, and the electrical signal is converted into a digital signal by an AD conversion circuit to obtain a pulse wave waveform, and the heart rate and/or maximum oxygen uptake are calculated based on the pulse wave waveform.

Preferably, it also includes a host shell, in which the microfluidic chip, electrochemical sensor module, photoelectric detection module and circuit control system are all placed; a detection hole is provided at the bottom of the host shell, and the photoelectric detection module is arranged at the detection hole; the microfluidic chip is arranged outside the bottom of the host shell.

Preferably, metal spring pins are provided at the bottom of the host housing, some of which connect the electrochemical sensor module to the circuit control system; and other metal spring pins can be used to charge the circuit control system.

The application of wearable sweat sensors for real-time monitoring of sports health in continuously monitoring changes in physiological parameters during exercise.

The advantages and positive effects of the present invention are: sweat samples are detected by a microfluidic chip, and sweat continuously flows through the electrochemical sensor interface during the flow in the microchannel, so that real-time and continuous detection of sweat electrolyte concentration and lactic acid concentration can be achieved; the sweat sample is small in volume, and the sweat after detection can be quickly discharged through the waste liquid discharge area through the microchannel, and there will be no sweat accumulation, thereby ensuring the accuracy of the test and the sensitivity to the changes in the composition of the flowing sweat, and achieving continuous and accurate monitoring;

The sensor device integrates multiple physiological parameter monitoring functions, including electrochemical sensors for monitoring sweat electrolyte and metabolite concentrations and photoelectric sensors for monitoring heart rate and maximum oxygen uptake. It can detect changes in body state during exercise from multiple angles and obtain information such as electrolytes and lactate concentrations in sweat as well as heart rate, maximum oxygen uptake, etc. on the mobile terminal. The wearable sensor device can monitor changes in multiple physiological parameters over a period of time, which is convenient for scientific research or daily health care use.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic diagram of the assembly structure of a microfluidic chip;

Figure 2 Schematic diagram of a flexible substrate layer containing an electrochemical electrode array;

Figure 3 is a schematic diagram of a wearable sports health monitoring circuit control system;

Figure 4 is a schematic diagram of the mainframe housing structure;

Among them, 1. flexible base layer, 11. sweat inlet, 2. channel layer, 21. collection and detection chamber, 22. sweat inlet, 23. waste liquid outlet, 24. microchannel, 3. chip cover layer, 31. waste liquid outlet, 32. electrode leakage through hole, 4. electrochemical sensor module, 41. counter electrode, 42. reference electrode, 43. sodium ion solid selective electrode, 44. potassium ion solid selective electrode, 45. calcium ion solid selective electrode, 46. lactic acid selective electrode, 47. connecting wire, 48. insulating layer, 5. host housing, 51. photodetector, 52. metal spring needle.

DETAILED DESCRIPTION

The embodiments of the present invention are described below with reference to the accompanying drawings.

The present invention relates to a wearable sweat sensor for real-time monitoring of sports health, including a microfluidic chip, an electrochemical sensor module, a photoelectric detection module and a circuit control system. The electrochemical sensor module is arranged in the microfluidic chip, can contact with a sweat sample and be excited by a target component in the sweat sample to generate an electrical signal; the photoelectric detection module can record the change in light transmittance caused by the pulsation of arterial congestion and volume; the electrochemical sensor module and the photoelectric detection module are both connected to the circuit control system, receive instructions from the circuit control system and transmit information to the circuit control system. The electrochemical sensor module is arranged to detect changes in sweat ion concentration and lactic acid concentration; the photoelectric detection module is arranged to detect heart rate and maximum oxygen uptake, thereby realizing continuous monitoring of the wearer's sweat ion state, lactic acid state, heart rate and maximum oxygen uptake through a wearable sweat sensor, which is convenient for scientific research or daily health care use.

The microfluidic chip includes a flexible substrate layer 1, a channel layer 2 and a chip cover layer 3 from bottom to top. The material of the flexible substrate layer 1 is hydrophobic release paper, and the materials of the channel layer 2 and the chip cover layer 3 are both pressure-sensitive adhesives; an electrochemical electrode array is printed on the flexible substrate layer 1 to form an electrochemical sensor module 4. A collection and detection chamber 21 and one or more sweat inlets 22 are provided in the channel layer 2. The sweat inlet 22 is connected to the collection and detection chamber 21 through a chip microchannel 24; the collection and detection chamber 21 can be semi-cylindrical, and the arc side is connected to the sweat inlet 22. The sweat inlet 22 can be arranged in a circle, and the circle can be set arbitrarily, or it can be concentric with the semicircle where the collection and detection chamber 21 is located. Such a setting can make the sweat collected in multiple sweat inlets 22 be uniformly introduced into the collection and detection chamber 21. Corresponding to the sweat inlet 22, a sweat inlet 11 is provided on the flexible base layer 1. The number and position of the sweat inlet 11 correspond to the sweat inlet 22. The flexible base layer 1 is in contact with the skin surface. The sweat on the skin surface passes through the sweat inlet 11 and the sweat inlet 22 in turn, and then enters the collection and detection chamber 21 through the chip microchannel.

In order to ensure that sweat can be detected in real time, the problem of sweat discharge must also be solved to avoid excessive sweat accumulation affecting the detection accuracy. A waste liquid discharge port 31 is provided on the chip cover layer 3, and the position of the waste liquid discharge port 31 does not correspond to the sweat inlet 22 to prevent sweat from being discharged directly without detection. The channel layer 2 is also provided with a waste liquid outlet 23 corresponding to the position of the waste liquid discharge port 31. The waste liquid outlet 23 is connected to the collection and detection chamber 21 through the chip microchannel. In some embodiments of the present invention, the waste liquid outlet 23 can be connected to the straight side of the collection and detection chamber 21. When in use, the sweat on the skin surface passes through the sweat inlet 11 on the flexible base layer 1, the sweat inlet 22 in the channel layer 2, and the chip microchannel 24 in turn into the collection and detection chamber 21, and after contacting the electrochemical sensor module 4, it passes through the chip microchannel, the waste liquid outlet 23, and is discharged from the waste liquid discharge port 31.

The flexible base layer 1, the channel layer 2 and the chip cover layer 3 are bonded to each other to form a microfluidic chip; in some embodiments of the present invention, they can be bonded to each other through double-sided tape, and in order to avoid affecting the intercommunication between the channels, the shape of the double-sided tape is consistent with the channel layer 2. The wearable sensor device can be bonded to the skin through the medical double-sided tape on the outside of the flexible base layer 1, and the opening of the medical double-sided tape is provided with a through hole, and the range of the through hole is not less than the range of the sweat inlet 11 to avoid affecting the sweat entering the sweat inlet 11.

The electrochemical sensing module 4 on the flexible substrate layer 1 can be made on the flexible substrate layer 1 by screen printing technology, and the electrode circuit is at least partially exposed in the collection detection chamber 21, and can contact the sweat in the collection detection chamber 21. The electrode circuit includes a dot or arc-shaped electrode point, and a long strip connecting line 47 connecting the electrode points. The connecting line 47 is made by screen printing Ag/AgCl slurry on the flexible substrate; the electrode point is made by printing Ag/AgCl slurry and then superimposing conductive carbon slurry. The arc-shaped electrode points on both sides are respectively a counter electrode 41 and a reference electrode 42, and each origin electrode point can be used to detect the real-time concentration of a component in sweat. In a certain embodiment of the present invention, the multiple origin electrode points in the middle are respectively a sodium ion solid selective electrode 43, a potassium ion solid selective electrode 44, a calcium ion solid selective electrode 45 and a lactic acid selective electrode 46, and all working electrodes share a pair of counter electrodes 41 and a reference electrode 42.

The working electrodes are covered by different types of component selective membranes. The ion solid selective electrodes are obtained by dripping ion selective membrane solutions. First, a polyaniline solid transduction layer is prepared, and then an ion selective membrane solution is dripped onto the polyaniline solid transduction layer to obtain different types of ion solid selective electrodes. Among them, the ion selective membrane solution includes 1%-2% ion carrier, 0.5%-1% ion exchanger, 20%-40% polyvinyl chloride, 45%-70% dioctyl sebacate or 2-nitrophenyl octyl ether by mass fraction, which are evenly mixed in an organic solvent and can be used for drip coating to prepare ion solid selective electrodes. Lactate oxidase, chitosan and multi-walled carbon nanotubes are mixed to obtain a mixed solution, which is dripped on the working electrode point to obtain a lactic acid selective electrode. The prepared ion selective electrode or lactic acid selective electrode can detect the sodium ion, potassium ion, calcium ion or lactic acid content in sweat in a targeted manner, form a current signal or voltage signal to be transmitted to the circuit control system, and convert the electrochemical signal into a digital signal through a signal conversion module.

An insulating layer 48 is covered above the portion where the electrode array connection wire 47 is located to prevent the connection wire 47 in the electrode circuit from being electrically connected to the outside. The ends of the connection wires 47 of the electrode circuit are not covered by the insulating layer 48, so that the ends of some of the connection wires 47 of the electrode circuit can be connected to the front-end analog circuit of the circuit control system, which is used to receive current signals or voltage signals regularly or irregularly to achieve signal conduction.

The wearable sensor device including the microfluidic chip can monitor the metabolic level in real time. The sweat enters the collection and detection chamber 21 for detection and then is discharged through the waste liquid discharge port 31. New sweat can continue to enter the collection and detection chamber 21, so that the wearable sensor device can continuously monitor the sweat secreted from the skin surface. According to the open circuit voltage signal collected between the connection line of the all-solid sodium ion working electrode and the reference electrode connection line, the concentration of sodium ions in the sweat is determined; according to the open circuit voltage signal collected between the connection line of the all-solid potassium ion working electrode and the reference electrode connection line, the concentration of potassium ions in the sweat is determined; according to the open circuit voltage signal collected between the connection line of the all-solid calcium ion working electrode and the reference electrode connection line, the concentration of sodium ions in the sweat is determined; wherein, the open circuit voltage changes continuously, and the sudden change of the open circuit voltage signal indicates that the human skin begins to secrete sweat, and the value of the voltage signal is positively correlated with the real-time sodium ion/potassium ion/calcium ion concentration of the sweat. The concentration of lactic acid in sweat is determined based on the current signal collected from the connection line of the lactic acid electrode and the connection line of the counter electrode; the current signal changes continuously, and the current signal begins to change suddenly, indicating that the human skin begins to secrete sweat, and the value of the current signal is positively correlated with the real-time lactic acid concentration of sweat. By obtaining a real-time voltage or current signal through the wearable sweat sensor device provided by the present invention, the information on the changes in the real-time concentrations of sodium ions, potassium ions, and lactic acid in sweat can be obtained, and the detection results are not affected by the mixing of new and old sweat, and the accuracy is high.

The photoelectric detection module can be specifically a light detector, which can record the changes in light transmittance caused by the pulsation of arterial congestion and volumetric change, and is used for monitoring heart rate, blood oxygen, etc. The photoelectric detection module uses a light-emitting diode of a specific wavelength that is selective for oxygenated hemoglobin and hemoglobin in arterial blood as a light source. The photoelectric detector records the changes in light transmittance caused by the pulsation of arterial congestion and volumetric change, and the photoelectric conversion module receives the light signal, converts the light signal into an electrical signal, and amplifies and outputs it. The photoelectric detection module receives and stores the pulse wave signal through the main control processor module, and converts the pulse signal into a digital analog signal to obtain a pulse wave waveform, and calculates the heart rate (HR) and maximum oxygen uptake ( _VO2max ) based on the pulse wave waveform.

The method for calculating HR based on the pulse waveform is: first extract the peak point of the pulse waveform; then count the number of interval points N between adjacent peak points, where the number of interval points N is the number of sampling points contained in the time interval between adjacent peak points in the waveform; finally calculate the heart rate according to the following formula; Heart rate = 60 x Fs /N; where Fs represents the sampling frequency, that is, the number of data points collected per second; the method for calculating VO _2max based on the heart rate signal is: VO _2max = 15 x (HR _max / HR _rest ). Where HR _rest is the heart rate in the resting state, HR _max = 205.8 - (0.685 x age).

The photoelectric detection module and the electrochemical sensor module 4 are both connected to the circuit control system. The circuit control system includes a front-end analog circuit, a first conversion circuit, a microcontroller circuit, a second conversion circuit and a power management circuit, the power management circuit is electrically connected to the front-end analog circuit, the first conversion circuit, the second conversion circuit and the microcontroller circuit, the front-end analog circuit is connected to the connecting line 47 in the electrochemical sensor module 4, the front-end analog circuit is connected to the first conversion circuit, and the photoelectric detection module is connected to the second conversion circuit.

Among them, the front-end analog circuit includes a voltage follower circuit and a constant potentiostat circuit, and the voltage follower circuit and the constant potentiostat circuit are electrically connected to the first conversion circuit, and the first conversion circuit includes an A/D conversion circuit and a D/A conversion circuit; the microcontroller circuit includes an MCU, which can be used to send or receive signal information transmitted by each circuit module; the microcontroller circuit also includes a Bluetooth module, which can transmit information to the terminal device through Bluetooth, thereby realizing information interaction; for example, a smart phone is used to electrically connect the microcontroller through the Bluetooth module to realize signal transmission and control. The second conversion circuit connected to the light detection module includes a photoelectric conversion circuit and an A/D conversion circuit, and the second conversion circuit is also electrically connected to the microcontroller circuit. The power management circuit is electrically connected to the front-end analog circuit, the first conversion circuit, the second conversion circuit and the microcontroller circuit to provide power for each module circuit.

In order to facilitate wearing, in some embodiments of the present invention, a host housing 5 is further included, which may be cylindrical; the microfluidic chip, the electrochemical sensor module 4, the photoelectric detection module and the circuit control system are all placed in the host housing 5; the electrochemical sensor module 4 is arranged in the microfluidic chip, and the microfluidic chip is arranged on the outer side of the bottom of the host housing 5; in some embodiments of the present invention, the microfluidic chip is adhered to the outer side of the bottom of the host housing by double-sided adhesive, and the double-sided adhesive bonding method is used to facilitate the replacement of the microfluidic chip; eight metal spring pins 52 are fixed at the bottom of the host housing 5, six of which vertically pass through the electrode leakage through-holes 32 on the chip cover layer 3 and the channel layer 2, and contact the electrochemical electrode array connection line 47 in the microfluidic chip, and the other end thereof is connected to the front-end analog circuit of the circuit control system in the host housing 5 to realize the collection and transmission of electrical signals; the other two metal spring pins can be used to charge the circuit control system; a circuit board is also fixed inside the host housing 5, and the electrochemical sensor module circuit control system is assembled on the circuit board to realize the collection, conversion, processing and transmission of electrical signals and photoelectric signals. The photoelectric detection module is fixed at the bottom opening of the host housing 5 so that the photoelectric detector can directly contact the skin surface. When in use, the microfluidic chip can be replaced according to the usage. The old microfluidic chip is removed from the bottom of the host housing 5 and a new microfluidic chip is pasted at the corresponding metal spring pin position.

The wearable device is based on microfluidic chips, electrochemical sensors and photoelectric sensors. By using microfluidic chips to collect sweat, it effectively avoids the problems of sweat pollution, volatilization, cross-mixing of new and old sweat, and realizes the timely update of sweat in the channel, ensuring the timeliness of detection; the built-in electrochemical sensor module can detect the sweat entering the microfluidic chip and obtain the content changes of sweat components over a period of time; the photoelectric sensor module can record the vascular pulse signal and obtain the heart rate, maximum oxygen uptake and other signals according to the pulse waveform; the electrical signals and photoelectric signals related to physiological parameters can be transmitted to the mobile terminal via the data processing and transmission module, and finally realize the real-time monitoring of the concentration of electrolytes and metabolites in sweat, as well as heart rate, maximum oxygen uptake and other information. In this way, the multi-module wearable sensor device can provide a comprehensive and individualized health assessment, help individuals better understand their own physical condition, and provide a scientific basis for health management, sports training and rehabilitation. In addition, for researchers, the device can also collect a large amount of real-time physiological data, providing valuable information for research in the fields of exercise physiology, human metabolism and health science.

The scheme of the present invention is described below in conjunction with the accompanying drawings, wherein the experimental methods without specific operating steps are all carried out in accordance with the corresponding product instructions, and the instruments, reagents, and consumables used in the examples can all be purchased from commercial companies unless otherwise specified.

Sources of reagents and instruments: Sodium ion carrier X (4-tert-butylcalix[4]arene-tetraacetic acid tetraethyl ester), sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB), dioctyl sebacate (DOS), polyvinyl chloride (PVC), potassium ion carrier (valinomycin), potassium tetrakis(pentafluorophenyl)borate (C ₂₄ BF ₂₀ K), calcium ion carrier IV (ETH4324, tert-butyl-calix[4]arene tetrakis[2-(diphenylphosphoryl)ethyl ether), sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB), 2-nitrophenyl octyl ether, lactate oxidase and lactic acid were purchased from Shanghai Aladdin Reagent Company; sodium chloride, potassium chloride, ferric chloride, potassium ferrocyanide (K ₄ [Fe(CN) ₆ ]) were from Sinopharm Chemical Reagent Co., Ltd. Nafion solution (5 wt %) was purchased from Yuanye Biotechnology Co., Ltd.; multi-walled carbon nanotubes were purchased from Beijing Solebow Company; electrochemical workstation: CHI1040C, Shanghai Chenhua Instrument Co., Ltd.

Example 1: Preparation and assembly of microfluidic chip

1.1 Preparation of microfluidic chip

The microfluidic chip comprises a flexible substrate layer 1, a channel layer 2 and a chip cover layer 3, wherein the flexible substrate layer 1 is a release paper printed with an electrochemical electrode array, and the channel layer 2 and the chip cover layer 3 are made of pressure-sensitive adhesive.

The microfluidic chip structure was designed using AutoCAD drawing software, as shown in Figure 1, wherein the flexible substrate layer 1 is provided with 8 circular sweat inlets 11 arranged in a semicircular shape with an unfolding angle of 180 degrees; the channel layer 2 includes 8 sweat inlets 22 (aperture of 1 mm) and a collection detection chamber 21, and the 8 sweat inlets 22 (aperture of 1 mm) are respectively connected to the collection detection chamber 21 through a chip microchannel 24 (depth of 0.3 mm, width of 0.4 mm), and the sweat inlet 22 corresponds to the position of the sweat inlet 11, and the collection detection chamber 21 is semi-cylindrical (radius of 5 mm, height of 0.3 mm); a waste liquid outlet 31 is provided on the chip cover layer 3, and the position does not correspond to the sweat inlet 22 or the collection detection chamber 21, and a waste liquid outlet 23 is also provided on the channel layer 2 corresponding to the position of the waste liquid outlet 31, and the waste liquid outlet 23 is also connected to the collection detection chamber 21 through the chip microchannel. Six electrode leakage through holes 32 (with a radius of 4 mm) are provided on the channel layer 2 and the chip cover layer 3 in a direction perpendicular to the electrochemical electrode array connection lines.

Each functional structure on the flexible substrate layer 1, the channel layer 2 and the chip cover layer 3 is formed by _CO2 laser engraving with a laser power of 50 W.

The flexible base layer 1, the channel layer 2 and the chip cover layer 3 are bonded in sequence to assemble into the flexible base layer 1 of the microfluidic chip module of the wearable sweat sensor device.

An electrode array is provided on the flexible substrate layer 1 to form an electrochemical sensing module 4, and the electrode array is made by screen printing technology; as shown in FIG2 , the electrode circuit includes circular or arc-shaped electrode points, and long strip-shaped line foot connection lines 47, and the connection lines 47 are made by screen printing Ag/AgCl slurry on the flexible substrate; the electrode points are made by printing Ag/AgCl slurry and then printing conductive carbon slurry. The arc-shaped electrode points on both sides are the counter electrode 41 and the reference electrode 42, respectively, and the three origin electrode points in the middle are respectively covered with ion selective membranes to form solid ion selective electrodes, which selectively allow the target ions to pass through and prevent other components in sweat from passing through. Only the target ions can affect the potential difference of the electrode points, and specific ions in the sweat sample can be detected; another origin electrode point is covered with lactate oxidase, which can catalyze the oxidation of lactic acid to produce current changes to indirectly detect the concentration of lactic acid; all working electrodes share a pair of counter electrodes 41 and reference electrodes 42. The insulating layer 48 is covered above the portion where the electrode array connection wire 47 is located to prevent the connection wire 47 in the electrode circuit from being electrically connected to the outside. The end of the connection wire 47 of the electrode circuit is not covered by the insulating layer 48, so that the end of the connection wire of the electrode circuit can contact the metal spring pin 52 in the host housing 5 to achieve the conduction of electrical signals.

1.2 Preparation of ion-selective electrodes

The method for preparing a sodium ion selective membrane comprises the following steps: dissolving 1% sodium ion carrier X by mass, 0.55% NaTFPB, 33% PVC, and 65.45% DOS in 1 mL of tetrahydrofuran. The method for preparing a potassium ion selective membrane comprises the following steps: dissolving 2% potassium ion carrier by mass, 1% C ₂₄ BF ₂₀ K, 32.7% PVC, and 64.7% DOS in 1 mL of tetrahydrofuran. The method for preparing a calcium ion selective membrane comprises the following steps: dissolving 1% calcium ion carrier IV by mass, 0.55% NaTFPB, 33% PVC, and 65.45% 2-nitrophenyl octyl ether in 1 mL of tetrahydrofuran.

Before adding the ion selective membrane, the electrochemical electrode was immersed in a mixed solution containing 5 mM FeCl ₃ , 5 mM K ₃ [Fe(CN) ₆ ] and 0.1 M KCl, and Prussian blue was electrodeposited at a scan rate of 100 mV s ^-1 between 0 and 1.0 V. After 30 cyclic voltammetry, a Prussian blue solid-state transduction layer was obtained. After washing with deionized water and drying, 10 μL of different types of ion selective membrane solutions were added respectively, and different types of ion selective electrodes were formed after drying.

The components of the lactate selective membrane are lactate oxidase, chitosan and multi-walled carbon nanotubes. The preparation method of the lactate detection electrode includes the following steps: mixing a chitosan solution with a mass fraction of 1% with an acetic acid solution with a mass fraction of 2%, placing the mixture on a magnetic stirrer and stirring for 1 hour, adding (2 mg/mL) multi-walled carbon nanotubes and continuing to stir for 30 minutes to obtain a mixed solution A. A 10 mg/mL lactate oxidase solution B is prepared with 10 × PBS buffer. Solution A and solution B are mixed in a volume ratio of 2:1, stirred for 20 minutes, and ultrasonicated for 10 minutes to obtain the final solution C. Take 10 μL of solution C and drop it on the working electrode point and dry it at room temperature for 12 h. Add 3 μL of Nafion (0.5 wt%) solution dropwise on the dried mixed solution and dry it at room temperature.

Example 2: Health Monitoring Wearable Device

The wearable device includes the microfluidic chip prepared and assembled in Example 1, and also includes a light detector and a circuit control system. The electrochemical sensor module and the light detector are both connected to the circuit control system, receive control instructions from the circuit control system, and feed back information to the circuit control system.

The circuit control system includes a front-end analog circuit, a first conversion circuit, a controller circuit and a second conversion circuit. The electrochemical electrodes are connected to the microcontroller circuit via the front-end analog circuit and the first conversion circuit in sequence, and the light detector is connected to the microcontroller circuit via the second conversion circuit.

The circuit control system is shown in FIG3 . The front-end analog circuit is connected to the end of the connection line 47 of the electrochemical electrode through a metal spring pin 52, including a voltage follower circuit and a constant potential meter circuit; the voltage signal and the current signal are collected and sent to the conversion circuit. The conversion circuit will generate the reference voltage required for electrochemical measurement and perform differential processing on the collected voltage signal and current signal, and send the differentially processed data to the microcontroller circuit; including an A/D conversion circuit and a D/A conversion circuit. The microcontroller circuit includes an MCU and a Bluetooth module, wherein the MCU and the Bluetooth module are connected, and the MCU is used to control the A/D conversion circuit and the D/A conversion circuit to process the data collected by the front end, and to control the power management to power the front-end analog circuit and the conversion circuit. The MCU is also used to run the protocol stack program required for Bluetooth communication; the Bluetooth module is used to transmit the data to the mobile terminal, and the mobile terminal receives the signal and outputs the sweat detection result corresponding to the signal.

The second conversion circuit includes a photoelectric conversion circuit and an AD conversion circuit. The photoelectric detection module records the light transmittance change caused by the arterial pulsation and congestion volume through the photodetector, receives the light signal through the photoelectric conversion circuit and converts the light signal into an electrical signal, and then converts the electrical signal into a digital signal through the AD conversion circuit to obtain a pulse wave waveform, and calculates the heart rate (HR) and maximum oxygen uptake (VO _2max ) according to the pulse wave waveform. The method for calculating HR according to the pulse wave waveform is: first extract the peak point of the pulse wave waveform; then count the number of interval points N between adjacent peak points, and the number of interval points N is the number of sampling points contained in the time interval between adjacent peak points in the waveform; finally, calculate the heart rate according to the following formula; heart rate = 60 x Fs /N; where Fs represents the sampling frequency, that is, the number of data points collected per second; the method for calculating VO _2max according to the heart rate signal is: VO _2max = 15 x (HR _max / HR _rest ). Where HR _rest is the heart rate in the resting state, HR _max = 205.8 - (0.685 x age).

Through the mutual cooperation between the above modules, the wearable device can monitor electrolytes, lactic acid, heart rate and maximum oxygen uptake at the same time.

Example 3: Wearable sweat sensor for real-time sports health monitoring

The wearable sensor device includes the assembled wearable sensor device of Example 2, and also includes a host housing 5 as shown in FIG4. The circuit control system and the photoelectric detection module are both placed in the host housing 5. The microfluidic chip is adhered to the outside of the bottom of the host housing by double-sided adhesive. The six metal spring needles 52 at the bottom of the host housing 5 are respectively connected to the ends of the six connecting wires of the electrode array in the microfluidic chip through the electrode leakage through-holes 32. The other end of the metal spring needle 52 is connected to the front-end analog circuit of the circuit control system in the host housing to realize the collection and transmission of electrochemical signals. The other two metal spring needles 52 at the bottom of the host housing 5 are used for charging the host, and the other end thereof is connected to the power management module of the circuit control system in the host housing. A hole is opened at the bottom of the host, and a light detector 51 of the photoelectric detection module is built in the hole position, which is used to directly contact the skin and record the light transmittance change caused by the congestion and volume of the arterial pulsation.

By using microfluidic chips to collect sweat, problems such as sweat contamination, volatilization, and cross-mixing of new and old sweat can be effectively avoided, and the sweat in the channel can be updated in a timely manner, ensuring the timeliness of the detection. The built-in electrochemical sensor module can detect the sweat entering the microfluidic chip and obtain the changes in the content of each component of sweat over a period of time. The photoelectric sensor module can record vascular pulse signals and obtain signals such as heart rate and maximum oxygen uptake based on the pulse waveform. Electrical signals and photoelectric signals related to physiological parameters can be transmitted to the mobile terminal via the data processing and transmission module, ultimately realizing real-time monitoring of the concentration of electrolytes and metabolites in sweat, as well as heart rate, maximum oxygen uptake and other information.

Example 4: Application of wearable sweat sensor for real-time sports health monitoring in continuous monitoring of exercise process

The wearable sweat sensor involved in Example 3 is worn on the subject. During exercise, the sweat secreted from the skin surface is pumped into the microfluidic chip through the sweat inlet. After flowing into the detection chamber through the microchannel, the electrode array printed on the back of the microfluidic chip cover plate can generate a corresponding electrical signal, which is expressed in the form of an open circuit voltage or current value. The circuit signal is collected and data processed by the circuit control system, and the concentration information of each metabolite in the sweat is obtained in the mobile terminal. The subject's vascular pulse signal is monitored by the photoelectric detection module, transmitted to the circuit control system, converted into heart rate information and maximum oxygen consumption information and transmitted to the collection terminal. The subject can view the ion concentration and/or lactic acid concentration, heart rate and/or oxygen consumption in the real-time sweat sample in the mobile terminal. After wearing it for a period of time, the subject's metabolic condition and heart rate condition can be presented through a trend chart composed of several data.

The embodiments of the present invention are described in detail above, but the contents are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of application of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims (10)

1. A wearable sweat sensor for sports health real-time supervision, its characterized in that: comprising the steps of (a) a step of,

The microfluidic chip comprises a flexible substrate layer, a channel layer and a chip cover layer which are sequentially attached, wherein a collection and detection cavity is formed in the channel layer, and sweat can penetrate through the flexible substrate layer and enter the collection and detection cavity;

an electrochemical sensing module disposed on the flexible substrate layer, comprising electrically connected electrode points and connecting wires, the electrode points being disposed to be exposed in the collection detection chamber;

the photoelectric detection module is used for recording the light transmittance change of the light caused by arterial pulsation hyperemia volumization;

And the electrochemical sensing module and the photoelectric detection module are both connected with the circuit control system.

2. The wearable sweat sensor for real-time athletic health monitoring of claim 1, wherein: the electrode points comprise a counter electrode, a reference electrode, an ion-selective electrode and a lactic acid-selective electrode;

The ion-selective electrode comprises one or more of a sodium ion solid-state selective electrode, a potassium ion solid-state selective electrode, and a calcium ion solid-state selective electrode.

3. The wearable sweat sensor for real-time athletic health monitoring of claim 2, wherein: the ion selective electrode comprises an electrode point and an ion selective membrane covered on the electrode point; the lactic acid selective electrode includes an electrode point and a lactic acid selective membrane covering the electrode point.

4. A wearable sweat sensor for sports health real-time monitoring according to any one of claims 1-3, characterized in that: one or more sweat inlets are also arranged in the channel layer, and the sweat inlets are communicated with the collection and detection chamber through a chip micro-channel; the sweat inlets are arranged on the flexible substrate layer, and the sweat inlets correspond to the sweat inlets in number and in position.

5. The wearable sweat sensor for real-time athletic health monitoring of claim 4, wherein: the chip cover layer is provided with a waste liquid outlet, the channel layer is also provided with a waste liquid outlet corresponding to the sweat waste liquid outlet, and the waste liquid outlet is communicated with the collecting and detecting chamber through a chip micro-channel.

6. The wearable sweat sensor for real-time athletic health monitoring of claim 1, wherein: the circuit control system comprises a front-end analog circuit, a first conversion circuit, a microcontroller circuit, a second conversion circuit and a power management circuit, wherein the power management circuit is electrically connected with the front-end analog circuit, the first conversion circuit, the second conversion circuit and the microcontroller circuit, the front-end analog circuit is connected with the connecting wire in the electrochemical sensing module, the front-end analog circuit is connected with the first conversion circuit, and the photoelectric detection module is connected with the second conversion circuit; the first conversion circuit and the second conversion circuit are both connected with the microcontroller circuit.

7. The wearable sweat sensor for real-time athletic health monitoring of claim 6, wherein: the photoelectric conversion circuit converts the received optical signals into electric signals, the AD conversion circuit converts the electric signals into digital signals to obtain pulse wave waveforms, and the heart rate and/or the maximum oxygen uptake are calculated according to the pulse wave waveforms.

8. The wearable sweat sensor for real-time athletic health monitoring of any of claims 1-3, 5-7, wherein: the micro-fluidic chip, the electrochemical sensing module, the photoelectric detection module and the circuit control system are all arranged in the host shell; the bottom of the host shell is provided with a detection hole, and the photoelectric detection module is arranged at the detection hole; the microfluidic chip is arranged outside the bottom of the host shell.

9. The wearable sweat sensor for real-time athletic health monitoring of claim 8, wherein: the bottom of the host shell is provided with a metal spring needle, and part of the metal spring needle connects the electrochemical sensing module with the circuit control system; additional of the metallic pogo pins can be used to charge the circuit control system.

10. Use of a wearable sweat sensor for real-time monitoring of sports health according to any of claims 1-9 for continuous monitoring of physiological parameter changes during sports.