A flexible electrode device for detecting liquid K ions

Abstract

The present invention discloses a flexible electrode device for detecting liquid K ions, comprising a flexible electrochemical sensor and a microfluidic liquid flow channel. The flexible electrochemical sensor and the microfluidic liquid flow channel are connected by PDMS curing. The flexible electrochemical sensor is composed of a three-electrode system, including a working electrode, a reference electrode and a counter electrode. By modifying a sensitive membrane on the surface of the working electrode for ion selection, K ions are sensitively identified, causing potential changes, and are not affected by other ions. When the detected liquid is sweat, the sweat collection device on the electrode collects sweat produced by human sweat glands in real time; when the detected liquid is blood or urine, by adding a columnar structure in the microchannel, cells and impurities in the liquid are filtered, providing a new idea for detecting ion concentrations in body fluids. It is used for people doing outdoor sports to provide a reference for electrolyte replenishment after exercise, and human health monitoring can be achieved anytime and anywhere, which is more free and convenient.

Description

Technical Field

[0001] The present invention relates to the field of potential-type electrochemical detection technology. By combining it with the field of sports medicine, the concentration of K ions in human body fluids is detected in real time, and a flexible wearable electrochemical detection electrode device is developed.

[0002] Globally, overweight and obesity are significant risk factors for chronic non-communicable diseases, such as cardiovascular disease, cancer, and type 2 diabetes, and contribute to premature death. The diagnosis of obesity is closely linked to abnormal fat metabolism and distribution. During high-intensity exercise and disease diagnosis, sweat biomarkers related to physiological processes are often the primary targets of testing. Sweat is the primary means by which the human body regulates body temperature and excretes toxins. It is also the second-largest method of salt excretion after urine, and contains a rich source of electrolytes and metabolic molecules, offering enormous potential for disease diagnosis and health monitoring.

[0003] Electrolytes such as potassium ions in blood and sweat are related to hydration status and can be used to diagnose, track, and predict the effectiveness of exercise therapy for conditions such as obesity. The body's potassium concentration can predict muscle activity and is closely linked to various causes of hypokalemia and hyperkalemia. It can provide early warning of sudden cardiovascular and cerebrovascular events that may occur during exercise in obese patients. The body's potassium concentration can be determined by monitoring the concentration of potassium in sweat or blood. Compared to other body fluids (such as urine, blood, and saliva), sweat is readily available and amenable to non-invasive testing, making it an increasingly important diagnostic tool.

[0004] As an important analytical tool, electrochemical sensors have broad application prospects in research fields both domestically and internationally. They have important applications in environmental monitoring, medical diagnosis, and food safety. Current electrochemical sensor technology offers numerous advantages, including high sensitivity, high selectivity, good stability, low cost, and the ability to achieve continuous online monitoring. A flexible electrode device for detecting K ions in liquids has been developed. It measures K ion concentrations in various human body fluids. It features two flexible flow channel designs: one channel enables self-absorption of sweat during perspiration, while the other channel filters blood cells and impurities from blood or urine. Both channels are suitable for the dual-channel electrochemical sensor of the present invention. Absorbed sweat or filtered blood flows through the channel into the reaction chamber, where it reacts chemically upon contact with the sensor, causing a potential change. The electrochemical sensor utilizes a three-electrode configuration, primarily achieving ion selection by modifying the working electrode surface with a K ion-sensitive membrane or other substance. The dual-channel design allows the sensor to have two working electrodes, allowing the redundant working electrode to be used for other ion-selective membranes or for detecting substances such as glucose and lactate, thereby achieving efficient and rapid detection and analysis. This innovative, small, flexible electrochemical sweat ion detection device not only enables real-time detection of ions in sweat during exercise, but also measures ion concentrations in blood. Its compact design makes it more portable and suitable for outdoor exercisers, offering greater freedom and convenience. Detecting ions in body fluids holds promise for assessing human health. Summary of the Invention

[0005] Technical Purpose

[0006] The present invention proposes a potassium ion detection device. It involves two major contents: concentration monitoring and liquid collection through a small electrochemical sensor. The present invention selects a three-electrode chip as a detection sensor. The integration of the working electrode, auxiliary electrode and reference electrode can provide accurate potential control and monitoring. The designed three-electrode chip needs to complete the detection of K ions, and the measurement process will not be affected by sweat or other complex components in the blood. Traditional electrochemical sensors are rigid materials and need to meet the requirements of wear resistance and high temperature resistance. The present invention needs to design a flexible sensor that needs to fit the skin smoothly and be small and comfortable. Human sweat glands are distributed in various areas. In order to meet the needs of sweat detection, during the sensor detection process, sweat liquid needs to contact the electrode surface, so a microfluidic flow pool is designed to collect and lock the current sweat covering the electrode to facilitate measurement.

[0007] The liquid device of the present invention is suitable for detecting solutions containing human bodily fluids (blood, sweat, and urine). Microfluidics are required to filter out cells and impurities from these fluids. The microfluidic channels can also collect sweat in real time, collecting trace amounts of sweat from individual eccrine glands. Sweat from multiple regions is then pooled and transferred to a reaction chamber where electrodes are located. For blood or urine, microcolumns are designed into the flow channel to filter out blood cells and impurities. The flow cell also needs to meet flexibility requirements, combining it with the sensor to form a flexible detection device. All of these contribute to more accurate and reliable experimental results.

[0008] Technical Solution

[0009] To achieve the above object, the present invention is implemented using the following scheme:

[0010] The flexible electrochemical device for detecting ions mainly comprises a flexible electrochemical sensor and a microfluidic liquid flow channel. The flexible electrochemical sensor and the microfluidic liquid flow channel are connected together by PDMS curing.

[0011] The flexible electrochemical sensor is composed of a three-electrode system, including a working electrode, a reference electrode, and a counter electrode. The working electrode is primarily responsible for reacting with the analyte; the counter electrode forms a circuit with the working electrode; and the reference electrode forms a film that covers the surface of the electrically conductive metal after solidification, helping to improve the stability of the flexible electrochemical sensor's output signal. The entire flexible electrochemical sensor is designed in an "∞ shape," consisting of two large, connected arcs serving as counter electrodes, two complete small circles below the large arcs serving as the two working electrodes, and a rectangle between the two circles (working electrodes) serving as the reference electrode. The rectangular portions extending downward from the working, reference, and counter electrodes serve as current sensors and are connected to the detection circuit device.

[0012] The microfluidic liquid flow channel comprises four parts: a liquid collection chamber, a liquid filtration chamber, a liquid reaction chamber, and a liquid discharge chamber. The microfluidic liquid flow channel is rectangular in shape, with the liquid reaction chamber at its center. The outline of the microfluidic liquid flow channel is the same as the outer outline of the counter electrode in the electrochemical sensor, both of which are "∞-shaped," with the middle part hollowed out to form a chamber for storing liquid. The liquid filtration chamber is connected to the liquid collection chamber via a filtration channel. The microfluidic liquid filtration channel is arranged with a microcolumn structure, which is used to shield and filter cells and impurities, so that the liquid flowing into the reaction chamber is not affected by cells or impurities; the liquid collection chamber is connected to the liquid reaction chamber via a microchannel, and the liquid reaction chamber is connected to the liquid discharge chamber via a microfluidic liquid discharge channel.

[0013] The two working electrodes are capable of simultaneous multi-parameter detection, depending on the different modified materials on the working electrodes. Modifying one working electrode leaves the other as a redundant channel. The three-electrode sensor chip is first coated with a gold film for current sensing. The working electrode is then covered with a PEDOT:PSS membrane, followed by a K ion-selective membrane, giving the flexible electrochemical sensor K ion-selective permeability. The reference electrode is first coated with silver chloride, followed by a PVB membrane, to increase detection sensitivity and stability.

[0014] Furthermore, the electrode materials of the working electrode and the counter electrode are inert solid materials such as gold, platinum, carbon, etc.; the reference electrode is selected from the inert liquid material Ag / AgCl.

[0015] Furthermore, the microchannel and the microchannel liquid discharge channel are both slender channels, distributed around the liquid reaction chamber. The liquid collection chamber is directly connected to the liquid collection chamber to be tested; the liquid first enters the device through the collection channel, and then enters the liquid collection chamber through the filtration channel. As the microchannel flows into the liquid reaction chamber, as the liquid collection chamber continuously collects liquid, the liquid reaction chamber is gradually filled. Directly above the liquid reaction chamber is the electrochemical sensor, and the liquid will contact the electrochemical sensor in the liquid reaction chamber, forming a voltage change. After the liquid reaction chamber is filled, as the liquid in the liquid collection chamber continues to enter, the excess liquid will be discharged from the liquid discharge chamber channel.

[0016] Furthermore, the flexible electrochemical sensor is made of bendable PET, and the microfluidic channel is made of PDMS. A curing agent and liquid PDMS are added to a mold, and the flexible electrochemical sensor is placed on the PDMS. The mold's liquid reaction chamber aligns perpendicularly with the electrode portion of the flexible electrochemical sensor. After heating and curing, the flexible electrochemical sensor and microfluidic liquid channel are integrated.

[0017] Furthermore, for testing samples like blood and urine, the microfluidic liquid filtration channel features a micropillar structure with a spacing of 5µm. Liquid transfer is accomplished by adding a pressure pump, filtering out impurities like blood cells and dandruff through the micropillars. For sweat testing, the microfluidic liquid filtration channel does not require a micropillar structure. The channel diameter is less than 100 microns, generating capillary force and eliminating the need for a pressure pump. The collection channel is self-propulsive, using capillary force to transfer sweat from the skin to the electrode detection area.

[0018] Furthermore, the microfluidic liquid flow channel is made soft by PDMS, which can meet the needs of wearable detection.

[0019] Furthermore, the flexible electrochemical sensor is shaped to match the microchannel and is located directly above the microchannel, forming a reaction chamber with the channel. The electrical conductor is located directly above the reaction chamber and contacts the liquid to be tested.

[0020] The present invention provides a method for preparing and modifying a device and a sensor sensitive membrane

[0021] 1. Preparation of Flexible Electrochemical Sensors

[0022] 1) Mask fabrication: Remove the A side of the double-sided tape (300Lse) and stick it to cardboard as the mask base. Use a laser to cut the sensor mask.

[0023] 2) Three-electrode Fabrication: Peel off the double-sided tape (a) on the cardboard, attach the double-sided tape mask (a) to a transparent PET film, use PI tape to cover the reference electrode, and then place the cardboard in a magnetron sputtering apparatus for sputtering. Sputtering metal films (gold, platinum, carbon);

[0024] 3) Working electrode modification:

[0025] Poly(4-styrenesulfonic acid) PEDOT:PSS was dropped onto the working electrode, and the solution was allowed to stand for 20 minutes. The addition was repeated 2 to 3 times.

[0026] Take 5-10µl of the K ion selective membrane solution and drop it onto the surface of the gold working electrode. Allow it to dry naturally at room temperature. This will produce a K ion selective electrode.

[0027] 4) Reference electrode modification: Tear off the PI tape covering the reference electrode in (2), apply Ag paste to the reference electrode position, place in an oven, and dry at 70°C for 1 hour. Dissolve PVB and NaCl in anhydrous methanol to prepare a mixture, apply the mixture to the Ag / AgCl reference electrode, and dry at room temperature.

[0028] In step (2), PET is polyethylene terephthalate, which has excellent mechanical properties, an operating temperature of up to 120° C., and a low price. The thicker the material, the higher the hardness. Preferably, the thickness is 0.075 mm to 0.125 mm.

[0029] In step (2), the conductive layer material sputtered is preferably gold (Au) with a thickness of 100 nm to 200 nm.

[0030] In step (3), PEDOT:PSS is a hydrogel that acts as an ion-electron conversion mediator to reduce potential drift. Preferably, 0.4-1.0 µl is added dropwise each time.

[0031] The role of the K ion selective membrane in step (3) is to achieve selective recognition of K ions by the electrode, and to be insensitive to other ions (Na, Ca, Mg), thereby increasing detection accuracy.

[0032] In step (4), the PVB film will wrap the electrode to maintain the stability of the reference electrode. The PVB is preferably 50-100 mg, the NaCl is preferably 20-70 mg, and the methanol is preferably 0.6-1 ml.

[0033] 2. Microfluidic Flow Cell Preparation

[0034] 1) Milling machine cuts transparent PMMA molds; photolithography is used to make flow channel molds;

[0035] The flow cell is designed and matched according to the shape of the sensor.

[0036] 2) Casting PDMS: Mix PDMS and curing agent, pour into the mold, and then evacuate (vacuum gauge reading 0.07-0.09) for 20-40 minutes until no bubbles are generated. Place on a hot plate to heat and cure.

[0037] 3) Peel the flow cell from the mold.

[0038] The PDMS described in step (2) is the most widely used silicon-based organic polymer. The larger the ratio of PDMS to curing agent, the smaller the hardness and the softer the flow cell. The preferred ratio is 7:1 to 15:1.

[0039] Preferably, the higher the vacuum gauge reading in step (3), the shorter the vacuuming time. The heating time should not be too long, as it will affect the hardness of the flow channel.

[0040] In the electrochemical sensor preparation process, the electrochemical sensor is placed on the mold before curing in step (2), in contact with the uncured liquid PDMS, and then removed after heating and curing. The electrochemical sensor is then combined with the flow channel. This completes the preparation of the entire device. Preferably, the wearable device for human experiments is attached to the human body using an elastic strap.

[0041] 3. Preparation of K ion selective sensitive membrane in step (3)

[0042] 1) Dissolve valinomycin, potassium tetrakis(4-chlorophenyl)borate (KTClPB), and dioctyl sebacate (DOS) in tetrahydrofuran (THF) in sequence, stir with a vortex mixer for 5 minutes, and then ultrasonicate for 30 minutes to completely dissolve.

[0043] 2) Add high molecular weight polymer polyvinyl chloride (PVC) to the above solution and stir with a vortex mixer to dissolve it to obtain a K ion selective membrane solution.

[0044] The potassium ion carrier in the potassium ion sensitive membrane solution of step (1) is valinomycin, a special compound that extracts potassium ions from the solution (water) interface into the polymer sensitive membrane. It has the ability to selectively recognize potassium ions and can ensure the smooth completion of polymerization. The concentration of valinomycin in the tetrahydrofuran solution is preferably 0.002g / ml~0.01g / ml. The reagent amount of potassium tetrakis(4-chlorophenyl)borate (KTClPB) is preferably 0.0002 g / ml-0.0010 g / ml. Dioctyl sebacate (DOS) is a plasticizer for the sensitive membrane solution, which can enhance the fluidity of the compound. The concentration in the tetrahydrofuran solution is preferably 5.98g / ml~6.87g / ml.

[0045] The solvent for preparing the solution is tetrahydrofuran (THF), and the reagent volume is preferably 0.5-1 mL.

[0046] The non-conductive high molecular polymer (polyacrylate, polybutylacrylate, polyurethane, polysiloxane) described in step (2) is used as a base material to enhance the chemical stability of the reagent, preferably polyvinyl chloride (PVC), and the preferred mass percentage of the PVC is 30.5% to 48.6%.

[0047] Preferably, the PVC in step (2) has a high viscosity and is finally dissolved in the solution described in step (1).

[0048] Preferably, the potassium ion selective membrane solution obtained in step (2) has a volatile solvent, tetrahydrofuran (THF), and the reagent needs to be sealed in a vacuum and stored in a freezer at a low temperature of -4°C. Beneficial effects

[0049] It can be seen from the above technical solution that the present invention has the following beneficial effects:

[0050] The present invention designs a small electrochemical sensor unit with small size and good electrode ion selectivity. The manufacturing process is simple and requires few consumable materials and reagents. The use of the sensor electrode of the present invention can solve the problems of large instruments and complex operations.

[0051] The three-electrode system of the present invention has dual-channel characteristics. In addition to the working electrode modified with the sensitive membrane, a redundant working electrode is also designed to facilitate the measurement of other substances in the future. The dual-channel design allows for the simultaneous detection of two substances, which is more efficient and convenient than a single-channel design.

[0052] The electrochemical sensor device of the present invention is soft and flexible, and can meet the condition of still closely adhering to the skin when the skin of the human body stretches and deforms during exercise, so that the entire detection process can be continuous in real time, and the detection signal will not be interrupted or affected by poor contact of the sensor.

[0053] The microfluidic device of the present invention not only conforms softly to the skin but also incorporates multiple microchannels designed to absorb sweat, concentrating the sweat absorbed from all directions into a single large chamber, which corresponds to the three electrodes of the sensor. Because sweat during exercise flows under the influence of gravity or the inertial force generated by running, real-time collection of sweat during exercise is a challenge. The microfluidic device of the present invention effectively solves this problem. After being collected in the large chamber, old sweat is discharged through the sweat channel as new sweat is injected, thus solving the problem of real-time sweat collection.

[0054] This invention enables wearable monitoring of potassium ions in sweat during perspiration. The entire device can be worn with a strap on the forehead or other areas with a high number of sweat glands (such as the arms or back). This not only increases user comfort during the monitoring process but also expands its scope beyond treadmills, meeting the real-time measurement needs of outdoor athletes and providing a reference for post-exercise electrolyte replenishment.

[0055] The present invention can realize the detection of K ions in blood and urine. The collected body fluids (blood, urine) are transported to the microfluidic device through a pump. A micro-column structure filtration channel is added to the microfluidic channel. After the body fluid is transported to the filtration channel, blood cells and impurities are filtered, and then it enters the reaction chamber to react with the sensor. The present invention can successfully avoid the influence of blood cells and impurities in body fluids on the sensor, which helps to improve the detection accuracy and stability. The integrated design successfully reduces the extra filtration steps, making the detection process convenient and efficient.

[0056] The present invention combines the electrode detection part and the liquid collection part together, and the integrated design greatly reduces the volume of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a system block diagram of the device of the present invention.

[0058] Figure 2 This is a sensor design diagram of the present invention. 1- counter electrode of the flexible electrochemical three-electrode sensor, 2- first working electrode of the flexible electrochemical three-electrode sensor, 3- second working electrode of the flexible electrochemical three-electrode sensor, 4- reference electrode of the flexible electrochemical three-electrode sensor, 24- PET flexible substrate of the flexible electrochemical three-electrode sensor,

[0059] Figure 3This is a front view of the microfluidic liquid collection system of the present invention. Figures 5, 6, 7, 8, 9, 10, and 11 are microfluidic liquid collection chambers. Figures 12, 13, 14, 15, 16, 17, and 18 are microfluidic channels connecting the microfluidic liquid collection chamber and the reaction chamber. Figure 19 is the microfluidic reaction chamber. Figures 20, 21, and 22 are microfluidic liquid discharge channels. Figure 23 is the microfluidic PDMS flexible substrate.

[0060] Figure 4 This is a cross-sectional view of the liquid collection microchannel of the present invention. 5, 6, 7, 8, 9, 10, 11 - liquid collection chambers, 25 - PDMS flexible substrate.

[0061] Figure 5 It is a schematic diagram of the microchannel liquid filtration part of the present invention.

[0062] Figure 6 It is a front view of the device of the present invention.

[0063] Figure 7 It is a side view of the device of the present invention.

[0064] Figure 8 It is a detection flow chart of the device of the present invention.

[0065] Figure 9 The detection equipment detects data to obtain a K+ concentration gradient diagram. DETAILED DESCRIPTION

[0066] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0067] like Figure 1 The figure shows a system block diagram of the device of the present invention. The flexible electrochemical device for ion detection primarily comprises a flexible electrochemical sensor and a microfluidic fluid channel. The flexible electrochemical sensor comprises a three-electrode system, including a working electrode, a reference electrode, and a counter electrode. The microfluidic fluid channel comprises four components: liquid collection, liquid filtration, liquid reaction, and liquid discharge.

[0068] like Figure 2This is the electrochemical sensor part of the present invention. The entire sensor PET film is a rectangle of 30mm*40mm. The three electrodes are composed of two circular arcs with a radius of 4mm. The working electrode (2) is covered with an ion selective membrane, forming a loop with the counter electrode (1). When the liquid fully covers the electrode, a series of reactions will occur with the working electrode, causing a change in potential. The reference electrode (4) is coated with Ag paste, which can stabilize the voltage during the reaction process and is not affected by other environments and small currents. The working electrode (3) serves as the second electrode, which is the superior characteristic of the entire electrochemical sensor in the simultaneous measurement of multiple parameters. The working electrode serves as a redundant channel, and its surface can be covered with an ion detection membrane different from (2), thereby achieving the purpose of dual-channel simultaneous measurement and greatly improving the detection efficiency.

[0069] like Figure 3 The figure shows the front view of the microfluidic liquid collection of the present invention. The entire PDMS flow channel is a rectangle of 30mm*40mm. The thickness is 3mm. The liquid collection chamber (5, 6, 7, 8, 9, 10, 11) runs through the entire device (23) made of PDMS, and the chamber height is 3mm and the radius is 1mm. The liquid is transmitted from the back to the front and is transmitted to the liquid filtration channel (12, 13, 14, 15, 16, 17, 18). The microchannel only exists on the front of the device. The channel is 0.3mm wide and concave 0.5mm downward. There are microcolumns in the liquid filtration channel (12, 13, 14, 15, 16, 17, 18). When the liquid flows, cells, impurities and other substances are filtered out. The liquid is then transmitted to the reaction chamber (19), and the reaction chamber is connected to the reaction chamber. Figure 2 The two arc shapes and sizes of the electrodes are the same, the depth of the reaction chamber is 0.5 mm, and when the liquid fills the reaction chamber, it will be discharged from the discharge channel (20, 21, 22).

[0070] like Figure 4 The figure shows a cross-sectional view of the microfluidic liquid collection of the present invention. The cross-section shows the liquid collection chambers (5, 6, 7, 8, 9, 10, 11), which extend longitudinally to the bottom of the circulation pool. Cells and impurities filtered from the liquid filtration channels (12, 13, 14, 15, 16, 17, 18) are collected from the waste liquid collection chambers (26, 27, 28, 29, 30, 31, 32) to the waste liquid outflow channel (33) and then discharged. The cross-sectional microfluidic channel (25) is PDMS. The bottom of the microfluidic channel is directly attached to the surface of the object where the liquid needs to be collected. Due to capillary action, the liquid is transported from the back (25) to the front (23). The entire device is made of PDMS, which can be bent and stretched, and is easy to attach to objects with rough surfaces and complex shapes. For example, to detect the concentration of K ions in sweat, the back side (25) can be covered on human skin through a strap. Due to the flexible nature of the flow channel, liquid will not leak from the side.

[0071] like Figure 5 The figure shows a schematic diagram of the microfluidic liquid filtration part of the present invention. Among them, Figure (a) shows the micro-column structure design for blood and urine testing. The spacing between the array micro-columns (34) is 5μm. Through the external force of the pump, the liquid is pumped from the liquid collection chamber (8) into the liquid filtration channel (15). The filtration channel (15) is 150μm wide. The presence of the array micro-columns (34) prevents blood cells (7-10μm) and other substances from flowing to the edge of the liquid filtration channel (15). The liquid flows to the left, and the liquid that has filtered out impurities flows from the edge of the liquid filtration channel (15) into the reaction chamber (19) for reaction. The liquid with impurities left between the two rows of array micro-columns (34) is discharged downward from the waste liquid collection chamber (29). Figure (b) shows the 3D structure of Figure (a). Figure (c) shows the flow channel structure design for sweat testing. The micro-column structure and the waste liquid collection hole are removed, and only the filtration channel (15) is retained. The filtration channel (15) is 100µm wide. When the human body secretes sweat, it will gradually fill the liquid collection chamber (8). After the liquid collection chamber is filled, the sweat will be absorbed into the reaction chamber (19) through the capillary action of the filtration channel (15).

[0072] like Figure 6 The figure shows the front view of the device of the present invention. The flexible electrochemical sensor (24) is bonded to both sides of the microfluidic liquid flow channel (23). The three electrodes (1, 2, 3, 4) of the electrochemical sensor are just above the microfluidic reaction chamber (19). The space between the two electrodes can accommodate liquid to enter the reaction. The volume of liquid required to cover the entire reaction chamber is small, which increases the detection speed and efficiency. After the device is assembled, the PET film of the flexible electrochemical sensor (24) is only 0.075mm thick and serves as a cover for the microfluidic liquid flow channel (23) to close the entire device, so that the microfluidic channel and chamber will not be exposed to the outside environment, causing experimental contamination and interference. This not only makes the device structure simpler, but also increases environmental safety.

[0073] like Figure 7The device of the present invention is shown in a side view. The bottom layer is blood, urine, or the upper layer of human sweat glands when wearable. When the test substance is blood or urine, the liquid enters the liquid filtration channel (12, 13, 14, 15, 16, 17, 18) from the liquid collection chamber (5, 6, 7, 8, 9, 10, 11), and after being filtered by the array micro-columns (34), the filtered liquid directly enters the microfluidic reaction chamber (19). The three-electrode chip corresponds to the microfluidic reaction chamber (19). The reference electrode (4) is first covered with silver chloride and then covered with a PVB film. The working electrode (2) has a PEDOT:PSS membrane and then a K ion selective membrane. The filtered liquid contacts the chip in the reaction chamber, reacts, and generates a potential change. The liquid is discharged from the discharge channel (20, 21, 22). The waste liquid filtered by the liquid filtration flow channel (12, 13, 14, 15, 16, 17, 18) enters the waste liquid collection chamber (26, 27, 28, 29, 30, 31, 32) and is collected in the waste liquid outflow channel (33) for discharge. When the test substance is sweat, the bottom will contact the human skin layer. After the skin sweats, the sweat fills the liquid collection chamber (5, 6, 7, 8, 9, 10, 11) and is then directly sucked into the microfluidic reaction chamber (19) through the capillary self-priming effect of the liquid filtration flow channel (12, 13, 14, 15, 16, 17, 18). When performing sweat detection, since the flow channel self-priming effect is required and sweat is usually clean and free of large impurities, the array microcolumns (34), the waste liquid collection chamber (26, 27, 28, 29, 30, 31, 32), and the waste liquid outflow channel (33) are removed. The liquid is discharged only from the discharge flow channels (20, 21, 22).

[0074] like Figure 8 The figure shows a flow chart for the detection process of the device of the present invention. In this example, a prepared flexible electrochemical sensor is covered with a selective membrane to form a potassium ion-selective electrode. The electrode is then bonded to a microfluidic channel for electrochemical detection of potassium ions. After the potassium ion-selective electrode is fabricated and the reference electrode is modified, the electrochemical sensor is tested for sensitivity, detection limit, and gradient display using a KCl solution with a defined concentration gradient. Example

[0075] Use deionized water and solid KCl reagent to prepare KCl solutions with concentrations of 1mM, 2mM, 4mM, 8mM, 16mM, and 32mM as sample reagents for testing;

[0076] See also Figure 9, select the function module of the open circuit voltage-time curve in the experimental parameter setting part of the control software, set the following parameters respectively: upper limit voltage: 0.5V, lower limit voltage: -0.5V, acquisition rate: 1s, running time: 250s, and complete the parameter setting before the experiment. Divide the running time into six segments, replace the KCl solution every 50s, use a pinhole to inject the liquid into the sweat collection port until the liquid fills the reaction chamber, and rinse with deionized water three times each time the liquid is replaced. The KCl solution (1mM, 2mM, 4mM, 8mM, 16mM, 32mM) is added in an order from low to high concentration. Run an experimental cycle, collect the open circuit voltage-time curves of six concentrations of KCl solution, and save the relevant data; this shows that the experimental stability is good;

[0077] In summary, the flexible electrochemical sensing detection device design for potassium ion detection proposed in the present invention can be widely used in the detection of potassium ion concentration, is easy to detect, has a good sensitivity detection limit, can realize human health monitoring anytime and anywhere, and realizes sweat detection, the whole device only needs to be worn on the body (forehead, wristband, back) using a strap. Not only has real-time self-absorption sweat detection been achieved, the comfort of the user during the detection process has been increased, the scope of use can also be expanded, and real-time measurement requirements can be provided for outdoor sports people, and a certain reference is provided for post-exercise electrolyte supplementation. When realizing blood and urine detection, liquid cell impurity filtration is achieved by adding microchannels, which provides a new approach for body fluid detection ion concentration.

Claims

1. A flexible electrode device for detecting liquid K ions, characterized in that: It includes two parts: a flexible electrochemical sensor and a microfluidic liquid flow channel; the flexible electrochemical sensor and the microfluidic liquid flow channel are connected together by PDMS curing; The flexible electrochemical sensor is composed of a three-electrode system, including a working electrode, a reference electrode, and a counter electrode. The working electrode is responsible for reacting with the analyte. The counter electrode and the working electrode form a circuit. After the reference electrode solidifies, it forms a film covering the surface of the electrically conductive metal, which helps to improve the stability of the output signal of the flexible electrochemical sensor. The entire flexible electrochemical sensor is designed in an "∞ shape", including two large arcs connected together as counter electrodes, two complete small circles below the large arcs, serving as two working electrodes, and a rectangle between the two working electrodes as a reference electrode. The rectangular portion extending downward from the working electrode, reference electrode, and counter electrode serves as a current sensor and is connected to the detection circuit device. The microfluidic liquid flow channel comprises four parts: a liquid collection chamber, a liquid filtration chamber, a liquid reaction chamber, and a liquid discharge chamber. The microfluidic liquid flow channel is rectangular in shape, with the liquid reaction chamber at its center. The outline of the microfluidic liquid flow channel is the same as the outer outline of the counter electrode in the electrochemical sensor, both of which are "∞-shaped," with the middle portion hollowed out to form a chamber for storing liquid. The liquid filtration chamber is connected to the liquid collection chamber via the filtration channel; the liquid collection chamber is connected to the liquid reaction chamber via the microfluidic channel, and the liquid reaction chamber is connected to the liquid discharge chamber via the microfluidic liquid discharge channel. There are two working electrodes. Depending on the different modified substances on the working electrodes, multi-parameter detection can be completed simultaneously. One of the working electrodes is selected for modification, and the other working electrode is used as a redundant channel. On the flexible electrochemical sensor, a gold film is covered as a current sensor, and the working electrode is covered with a PEDOT:PSS film, and then covered with a K ion selective membrane, so that the flexible electrochemical sensor has K ion selective permeability. The reference electrode is first covered with silver chloride and then with a PVB film.

2. A flexible electrode device for detecting liquid K ions according to claim 1, characterized in that: The electrode materials of the working electrode and the counter electrode are gold, platinum, and carbon inert solid materials; the reference electrode is Ag / AgCl inert liquid material.

3. The flexible electrode device for detecting liquid K ions according to claim 1, characterized in that: Both the microchannel and the microchannel liquid discharge channel are long and thin channels, distributed around the liquid reaction chamber; the liquid collection chamber is directly connected to the liquid collection chamber to be tested; the liquid first enters the device through the collection channel, and then enters the liquid collection chamber through the filtration channel, and flows into the liquid reaction chamber as the microchannel. When the liquid collection chamber continuously collects liquid, the liquid reaction chamber is gradually filled. The electrochemical sensor is directly above the liquid reaction chamber. The liquid will contact the electrochemical sensor in the liquid reaction chamber to form a voltage change; after the liquid reaction chamber is filled, as the liquid in the liquid collection chamber continues to enter, the excess liquid will be discharged from the liquid discharge chamber channel.

4. The flexible electrode device for detecting liquid K ions according to claim 1, characterized in that: The flexible electrochemical sensor is made of bendable PET, and the microfluidic channel is made of PDMS. A curing agent and liquid PDMS are added to a mold, and the flexible electrochemical sensor is placed on the PDMS. The liquid reaction cavity of the mold is perpendicular to the electrode part of the flexible electrochemical sensor. After heating and curing, the flexible electrochemical sensor and the microfluidic liquid channel are combined into one.

5. The flexible electrode device for detecting liquid K ions according to claim 1, characterized in that: The shape of the flexible electrochemical sensor matches the microchannel, and is located directly above the microchannel, forming a reaction chamber with the channel; the electrical conductor is located directly above the reaction chamber, contacting the liquid to be tested.

6. The flexible electrode device for detecting liquid K ions according to claim 1, characterized in that: The preparation process of the flexible electrochemical sensor is as follows: Step 1) Mask fabrication: Remove the double-sided tape and stick it to cardboard as the mask base. Use a laser to cut the sensor mask. Step 2) Fabrication of three electrodes: Peel off the double-sided tape (a) from the cardboard, attach the double-sided tape mask (a) to the transparent PET film, use PI tape to cover the reference electrode, and then place the cardboard in a magnetron sputtering instrument for sputtering; sputtering the metal film; Step 3) Working electrode modification: Poly(4-styrenesulfonic acid) PEDOT:PSS was dropped onto the working electrode, and the solution was allowed to stand for 20 minutes. The addition was repeated 2 to 3 times. Take 5-10µl of the K ion selective membrane solution and drop it onto the surface of the gold electrode of the working electrode. Let it dry naturally at room temperature to prepare the K ion selective electrode. Step 4) Reference electrode modification: Remove the PI tape covering the reference electrode in step 2), apply Ag paste to the reference electrode position, and place in an oven to dry at 70°C for 1 hour. Dissolve PVB and NaCl in anhydrous methanol to prepare a mixture, apply the mixture to the Ag / AgCl reference electrode, and dry at room temperature.

7. The flexible electrode device for detecting liquid K ions according to claim 6, characterized in that: In step 2), the sputtered conductive layer is made of gold with a thickness of 100 nm to 200 nm. In step 3), the K ion selective membrane is used to realize the selective recognition of K ions by the electrode and is insensitive to Na, Ca, and Mg ions.

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