Wearable microfluidic sweat detection system

Abstract

The invention discloses a wearable micro-fluidic sweat detection system which comprises a bionic micro-fluidic chip which comprises a chip body, a sweat inlet, a sweat outlet and a plurality of bionic detection cavities, the sweat inlet, the sweat outlet and the bionic detection cavities are formed in the chip body, and the bionic detection cavities are communicated end to end. Each bionic detection chamber comprises a bionic detection chamber body, an outer side micro-column array and an inner side micro-column array, the outer side micro-column array and the inner side micro-column array are concentrically arranged in the bionic detection chamber body, the outer side micro-column array comprises a plurality of outer side micro-columns which are uniformly arranged at intervals in the circumferential direction, and the inner side micro-column array comprises a plurality of inner side micro-columns which are uniformly arranged at intervals in the circumferential direction; the multi-parameter electrochemical sensor comprises a substrate and a plurality of detection electrodes arranged on the substrate, and one ends of the plurality of detection electrodes are in one-to-one correspondence contact with the plurality of bionic detection chambers respectively; and the wearable equipment is connected with the other ends of the plurality of detection electrodes. According to the invention, uniform and stable liquid supply can be provided, the accuracy of a detection signal is ensured, and high-precision detection of Na < + >, K < + > and Cl <-> can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of sweat detection, and in particular to a wearable microfluidic sweat detection system. Background Art

[0002] With the growth of the demand for personalized health monitoring, wearable detection devices have become a new requirement for the development of medical health. As a metabolite of the human physiological process, sweat contains many biomarkers closely related to human health. For example, the concentration of chloride ions in sweat can be used as a monitoring index for dehydration and heat stroke risks; the monitoring of the concentrations of sodium ions and potassium ions can be used as a basis for judging muscle cramps or dehydration. Monitoring the changes of these ions is crucial for sports health and disease prevention.

[0003] Various electrochemical sensors based on microfluidic channels have been developed to effectively collect and transport sweat. Although these microfluidic systems can effectively isolate the epidermis and transport sweat, there is still a lack of effective control over sweat. Some common micro-pump and micro-valve structures are applied to the microfluidic system, such as capillary burst valves (CBV) or self-driven valves, to achieve time-series sweat sampling. However, most of the micro-pump and micro-valve structures mainly control the motion state of the fluid and lack effective control over the internal flow field of the microfluid. However, Taylor dispersion phenomenon is caused by the speed difference during the transportation of sweat in the microfluidic channel, resulting in the concentration diffusion of the fluid and detection errors, thus making the accuracy of sweat detection poor and restricting the development of wearable sweat detection systems. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a wearable microfluidic sweat detection system.

[0005] In order to achieve the above purpose, the technical solution provided by an embodiment of the present invention is as follows:

[0006] A wearable microfluidic sweat detection system, comprising:

[0007] A bionic microfluidic chip, the bionic microfluidic chip includes a chip body, a sweat inlet, a sweat outlet and a plurality of bionic detection chambers arranged on the chip body. The plurality of bionic detection chambers are connected in series. The bionic detection chamber at the head end is connected to the sweat inlet, and the bionic detection chamber at the tail end is connected to the sweat outlet. Each bionic detection chamber includes a bionic detection chamber body, an outer micro-column array and an inner micro-column array concentrically arranged in the bionic detection chamber body. The outer micro-column array includes a plurality of outer micro-columns evenly spaced along the circumferential direction, and the inner micro-column array includes a plurality of inner micro-columns evenly spaced along the circumferential direction;

[0008] Multi-parameter electrochemical sensor, including a substrate and a plurality of detection electrodes disposed on the substrate, one ends of the plurality of detection electrodes are respectively in contact with a plurality of the bionic detection chambers one by one;

[0009] A wearable device is connected to the other ends of the plurality of detection electrodes, and is configured to receive and process a plurality of detection signals transmitted by the multi-parameter electrochemical sensor.

[0010] As a further improvement of the present invention, both the outer micro-columns and the inner micro-columns are in an arc shape protruding towards the inner wall of the bionic detection chamber body.

[0011] As a further improvement of the present invention, a main channel is communicated between the bionic detection chamber at the head end and the sweat inlet, a transition channel is communicated between adjacent bionic detection chambers, and an outlet channel is communicated between the bionic detection chamber at the tail end and the sweat outlet.

[0012] As a further improvement of the present invention, the width of the main channel is greater than the gap between the inner wall of the bionic detection chamber body and the outer micro-column, and the gap between the inner wall of the bionic detection chamber body and the outer micro-column is equal to the gap between the outer micro-column and the inner micro-column.

[0013] As a further improvement of the present invention, the number of the outer micro-columns is ten, the gap angle between adjacent outer micro-columns is 12°, the number of the inner micro-columns is four, the gap angle between adjacent inner micro-columns is 30°, and the gap between the outer micro-column and the inner micro-column is 200 μm.

[0014] As a further improvement of the present invention, the diameter of the bionic detection chamber body is 4000 μm and the height is 200 μm.

[0015] As a further improvement of the present invention, the width of the main channel is 250 μm.

[0016] As a further improvement of the present invention, the number of the bionic detection chambers is four, the multi-parameter electrochemical sensor includes four detection electrodes, and the four detection electrodes are a reference electrode, a chloride ion selective working electrode, a potassium ion selective working electrode, and a sodium ion selective working electrode respectively.

[0017] As a further improvement of the present invention, the reference electrode includes a first Ag / AgCl layer and a PVB / CNT layer stacked and connected to the first Ag / AgCl layer. The chloride ion selective working electrode includes a second Ag / AgCl layer. The potassium ion selective working electrode includes a first LIG electrode, a first ion-electron transfer layer stacked and connected to the first LIG electrode, and a potassium ion selective membrane stacked and connected to the first ion-electron transfer layer. The sodium ion selective working electrode includes a second LIG electrode, a second ion-electron transfer layer stacked and connected to the second LIG electrode, and a sodium ion selective membrane stacked and connected to the second ion-electron transfer layer.

[0018] As a further improvement of the present invention, the wearable device includes a watch. The bionic microfluidic chip and the watch are respectively bonded to opposite sides of the substrate of the multi-parameter electrochemical sensor. The sweat inlet of the bionic microfluidic chip is attached to the skin, and the plurality of receiving electrodes of the watch are respectively connected to the other ends of the plurality of detection electrodes of the multi-parameter electrochemical sensor.

[0019] The beneficial effects of the present invention are as follows:

[0020] (1) The unique structure of the micro-column arrays on the inner and outer sides of the bionic detection chamber of the present invention improves the uneven concentration distribution caused by the velocity difference inside the existing chamber. The bionic detection chamber of the present invention can provide a uniform and stable flow field, avoid concentration accumulation, and has high detection result accuracy. It can realize high-precision detection of Na + , K + and Cl - . This system has high precision, fast response and good repeatability, significantly improving the reliability of the sweat-based health monitoring system.

[0021] (2) The flow channel of the bionic microfluidic chip of the present invention is short, requiring less sweat volume, and the detection is faster and easier.

[0022] (3) The bionic detection chambers of the present invention are connected in series, and the same batch of sweat can be detected, and the sweat volume is the same, so the detection results are more accurate.

[0023] (4) The present invention provides a reference bionic chamber for reference electrode detection, avoiding integrating the reference electrode and the ion detection electrode in the same chamber for detection. The electrode manufacturing process is simple, which not only optimizes the manufacturing process but also improves the detection accuracy.

[0024] (5) By setting up a wearable device, it is convenient to carry and exercise, and the sweat generated during exercise can be detected in real time, so as to be able to monitor one's own physical state during exercise in real time. Description of the Drawings

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0026] Figure 1 Schematic structural diagram of the bionic microfluidic chip of the preferred embodiment of the present invention;

[0027] Figure 2 Schematic structural diagram of a single bionic detection chamber of the preferred embodiment of the present invention;

[0028] Figure 3 Schematic structural diagram of the multi-parameter electrochemical sensor of the preferred embodiment of the present invention;

[0029] Figure 4 Cross-sectional view of the potassium ion selective working electrode, sodium ion selective working electrode, chloride ion selective working electrode and reference electrode of the preferred embodiment of the present invention;

[0030] Figure 5 Top view structural diagram of the watch of the preferred embodiment of the present invention;

[0031] Figure 6 Bottom view structural diagram of the watch of the preferred embodiment of the present invention;

[0032] Figure 7 Schematic diagram of the principle for processing the detected electrical signal of the preferred embodiment of the present invention;

[0033] Figure 8 Velocity distribution curve of the microfluid at the center cross-section of the bionic detection chamber of the preferred embodiment of the present invention;

[0034] Figure 9 Simulation diagram of the existing simple chamber and the bionic detection chamber of the preferred embodiment of the present invention;

[0035] Figure 10 Velocity distribution curves of the simple chamber and the bionic detection chamber of the present invention;

[0036] Figure 11 Velocity distribution curves under different numbers of outer micro-columns;

[0037] Figure 12 Velocity distribution curves under different gaps between the inner and outer micro-columns;

[0038] Figure 13 Velocity distribution curves under different numbers of inner micro-columns;

[0039] Figure 14 Velocity distribution curves at different outer micro-column gap angles;

[0040] Figure 15 Velocity distribution curves at different inner micro-column gap angles;

[0041] Figure 16 Mechanical property test diagram of the microfluidic chip according to the preferred embodiment of the present invention;

[0042] Figure 17 Structure characterization diagram of the bionic detection chamber according to the preferred embodiment of the present invention;

[0043] Figure 18 Polystyrene microsphere concentration test diagrams for different chambers and experimental diagrams of polystyrene microsphere trajectories in different structured chambers;

[0044] Figure 19 Scanning electron microscope (SEM) image of the LIG electrode of the present invention;

[0045] Figure 20 Raman spectrum diagram of the multi-parameter electrochemical sensor of the present invention and comparison diagram of cyclic voltammetry scans at different laser scanning powers;

[0046] Figure 21 Relevant result diagram of potassium ion test of the present invention;

[0047] Figure 22 Relevant result diagram of sodium ion test of the present invention;

[0048] Figure 23 Relevant result diagram of chloride ion test of the present invention;

[0049] Figure 24 Detection result diagram displayed on the watch during actual movement;

[0050] Figure 25 Preparation flow chart of the multi-parameter electrochemical sensor according to the preferred embodiment of the present invention. Detailed implementation manners

[0051] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0052] Please refer to Figure 1 、 Figure 2 、Figure 3 , an embodiment of the present application discloses a wearable sweat detection system based on a bionic steady-flow structure microfluidics, including a bionic microfluidic chip 1, a multi-parameter electrochemical sensor 2, and a wearable device. The bionic microfluidic chip 1 includes a chip body 11, a sweat inlet 12, a sweat outlet 13, and a plurality of bionic detection chambers provided on the chip body 11. The plurality of bionic detection chambers are connected end to end, the bionic detection chamber at the head end is connected to the sweat inlet 12, and the bionic detection chamber at the tail end is connected to the sweat outlet 13. Each bionic detection chamber includes a bionic detection chamber body 141, an outer micro-column array and an inner micro-column array concentrically arranged within the bionic detection chamber body 141. The outer micro-column array includes a plurality of outer micro-columns 142 uniformly spaced along the circumferential direction, and the inner micro-column array includes a plurality of inner micro-columns 143 uniformly spaced along the circumferential direction. The multi-parameter electrochemical sensor 2 includes a substrate 21 and a plurality of detection electrodes provided on the substrate 21. One ends of the plurality of detection electrodes are respectively in contact with the plurality of bionic detection chambers in a one-to-one correspondence. The wearable device is connected to the other ends of the plurality of detection electrodes for receiving and processing the detection signals transmitted by the multi-parameter electrochemical sensor 2.

[0053] Please refer to Figure 1 , Figure 2 , sweat flows through the bionic detection chamber at the head end, the bionic detection chambers in the middle, and the bionic detection chamber at the tail end respectively through the sweat inlet 12. When entering the bionic detection chamber, the sweat sequentially flows through the gap 144 between the inner wall of the bionic detection chamber body 141 and the outer micro-column 142, the gap 145 between adjacent outer micro-columns 142, the gap 146 between the outer micro-column 142 and the inner micro-column 143, and the gap 147 between adjacent inner micro-columns 143 and enters the center of the bionic detection chamber body 141. Through the unique structural arrangement of the bionic detection chamber, the Taylor dispersion phenomenon of solute diffusion and concentration non-uniformity caused by the velocity gradient in laminar flow is solved, and it can ensure that the microfluidic flow field in the bionic detection chamber is uniform and stable, making the detection of the multi-parameter electrochemical sensor 2 more sensitive and accurate.

[0054] Please refer to Figure 1 , a main channel 15 is connected between the bionic detection chamber at the head end and the sweat inlet 12, a transition channel 16 is connected between adjacent bionic detection chambers, and an outlet channel 17 is connected between the bionic detection chamber at the tail end and the sweat outlet 13.

[0055] In this embodiment, the number of bionic detection chambers is four. The four bionic detection chambers are a reference bionic detection chamber 181, a chloride ion bionic detection chamber 182, a potassium ion bionic detection chamber 183, and a sodium ion bionic detection chamber 184. The reference bionic detection chamber 181 is located at the head end, and a main channel 15 is connected between the reference bionic detection chamber 181 and the sweat inlet 12. The sodium ion bionic detection chamber 184 is located at the tail end, and a liquid outlet channel 17 is connected between the sodium ion bionic detection chamber 184 and the sweat outlet 13. The reference bionic detection chamber 181, the chloride ion bionic detection chamber 182, the potassium ion bionic detection chamber 183, and the sodium ion bionic detection chamber 184 are connected in sequence. The multi-parameter electrochemical sensor 2 includes four detection electrodes, which are a reference electrode 22, a chloride ion selective working electrode 23, a potassium ion selective working electrode 24, and a sodium ion selective working electrode 25.

[0056] Please refer to Figure 3 , Figure 4 , the reference electrode 22 includes a first Ag / AgCl layer 221 and a PVB / CNT layer 222 stacked and connected to the first Ag / AgCl layer 221. The chloride ion selective working electrode 23 includes a second Ag / AgCl layer 231. The potassium ion selective working electrode 24 includes a first LIG electrode 241, a first ion-electron transfer layer 242 stacked and connected to the first LIG electrode 241, and a potassium ion selective membrane 244 stacked and connected to the first ion-electron transfer layer 243. The sodium ion selective working electrode 25 includes a second LIG electrode 251, a second ion-electron transfer layer 252 stacked and connected to the second LIG electrode 251, and a sodium ion selective membrane 253 stacked and connected to the second ion-electron transfer layer 252.

[0057] To further improve the stability of the flow field, it is preferred that both the outer micro-columns 142 and the inner micro-columns 143 are in a circular arc shape protruding towards the inner wall of the bionic detection chamber body 141.

[0058] Please refer to Figure 2 , the width W of the main channel 15 is greater than the gap 144 between the inner wall of the bionic detection chamber body 141 and the outer micro-columns 142. The gap 144 between the inner wall of the bionic detection chamber body 141 and the outer micro-columns 142 is equal to the gap 146 between the outer micro-columns 142 and the inner micro-columns 143. The number of outer micro-columns 142 is greater than the number of inner micro-columns 143. The adjacent outer micro-column gap angle is smaller than the adjacent inner micro-column gap angle.

[0059] The diameter of the bionic detection chamber body 141 is 4000 μm, and the height is 200 μm. The width W of the main channel 15 is 250 μm.

[0060] The number of outer micro-columns 142 is ten, the gap angle between adjacent outer micro-columns 142 is 12°, the number of inner micro-columns 143 is four, the gap angle between adjacent inner micro-columns 143 is 30°, and the gap 146 between the outer micro-columns 142 and the inner micro-columns 143 is 200 μm.

[0061] Specifically, the wearable device includes a watch 3. The bionic microfluidic chip 1 and the watch 3 are respectively bonded to opposite sides of the substrate 21 of the multi-parameter electrochemical sensor 2. The sweat inlet 12 of the bionic microfluidic chip 1 is attached to the skin. The multiple receiving electrodes (not shown in the figure) of the watch 3 are respectively connected to the other ends of the multiple detection electrodes of the multi-parameter electrochemical sensor 2. Please refer to Figure 6 , preferably, four electrode connection ports 31 are provided on the back of the watch 3, facilitating the one-to-one connection of the other ends of the reference electrode 22, the chloride ion selective working electrode 23, the potassium ion selective working electrode 24, and the sodium ion selective working electrode 25 to the four receiving electrodes of the watch 3. Please refer to Figure 5 , the front of the watch 3 is the dial 32. Please refer to Figure 7 , the electrical signal V Ref detected by the multi-parameter electrochemical sensor 2

[0062] flows through the main channel 15 and first enters the reference bionic detection chamber 181, then sequentially flows into the chloride ion bionic detection chamber 182, the potassium ion bionic detection chamber 183, and the sodium ion bionic detection chamber 184, and is in full contact with the corresponding reference electrode 22, chloride ion selective working electrode 23, potassium ion selective working electrode 24, and sodium ion selective working electrode 25 one by one, so as to realize the detection of Cl - , K + and Na + . The multi-parameter electrochemical sensor 2 can continuously and specifically monitor the concentrations of the above ions in sweat. In addition, the LIG electrode used in the multi-parameter electrochemical sensor 2, with its high conductivity and porous three-dimensional structure, significantly improves the active area and electron transfer efficiency, and realizes the high-precision detection of ions.

[0063] To better illustrate the reliability of the sweat detection system of the present invention, in this embodiment, a systematic study will be conducted on five parameters: the number of outer microcolumns, the gap between the inner and outer microcolumns (i.e., the gap between the inner microcolumns and the outer microcolumns), the number of inner microcolumns, the angle of the outer microcolumn gap, and the angle of the inner microcolumn gap. In order to evaluate the influence of different parameters on the microfluidic flow field, the method of controlling variables is used for the structural design of the bionic detection chamber. The COMSOL Multiphysics software is used for fluid dynamics simulation. The simulation analysis adopts the laminar flow model and combines the Navier-Stokes equation to simulate the influence of different design parameters on the flow field, taking the velocity distribution curve of the microfluid at the central cross-section of the bionic detection chamber, as Figure 8 shown, as the key index for evaluating the performance of the bionic detection chamber, where the marked central average flow velocity, equal velocity width, and gap flow velocity are used as parameters for evaluating the performance of the bionic detection chamber.

[0064] First of all, the simulation analysis was carried out on the simple chamber model shown in Figure 9 -(a) and the bionic detection chamber model shown in Figure 9 -(b). It can be seen from Figure 9 that the velocity distribution of the simple chamber model is peak-shaped, and the central velocity is about 110 μm / s, resulting in concentration diffusion. In the bionic detection chamber model, the velocity distribution in the central region is relatively uniform and concentrated, and the velocity in more than 60% of the region is 110 μm / s, and the stability of the flow field is significantly improved. Secondly, the simulation analysis was carried out on the five parameters respectively, and the velocity distribution curves are shown in Figure 10 respectively. It can be seen that when the number of outer microcolumns is 10, the angle of the outer microcolumn gap is 12°, the number of inner microcolumns is 4, the angle of the inner microcolumn gap is 30°, and the gap between the inner and outer microcolumns is 200 μm, the flow field distribution in the bionic detection chamber reaches the optimal. Figures 11 - 15 shown.

[0065] Due to its transparency, flexibility, biocompatibility and other characteristics, PDMS has become the preferred material for making microfluidic chips. The bionic microfluidic chip made of PDMS after preparation was subjected to tensile, bending and twisting tests. It can be seen from Figure 16 that the bionic microfluidic chip prepared by PDMS has excellent mechanical robustness and flexibility, which is sufficient to meet the needs of human wear.

[0066] Subsequently, the surface of PDMS was characterized by SEM electron microscopy scanning, and the overall morphology is shown in Figure 17As shown. It was observed that the diameters L1 and L2 of the bionic detection chamber were 3937 μm and 3933 μm respectively, the outer micro-column gap angle β2 was 12°52′, and the inner micro-column gap angle β1 was 31°47′. There were small deviations compared with the pre-designed diameter of 4000 μm, the outer micro-column gap angle of 12°, and the inner micro-column gap angle of 30°. This indicates that the precision of micro-nano 3D printing is sufficient to meet the usage requirements.

[0067] To verify the internal flow field performance of the bionic detection chamber, this embodiment conducts experimental verification in three aspects. First, polystyrene microspheres are injected into the bionic microfluidic chip, and the distribution of microspheres in the bionic detection chamber is observed. The experimental results are as Figure 18 shown. In Figure 18 -(a) the simple chamber shown, the number of microspheres in the upper part of the simple chamber is 114, and only 46 in the central region. This phenomenon is due to the concentration diffusion caused by the flow rate, resulting in a lower concentration in the central region and a higher concentration in the periphery. In contrast, in the bionic detection chamber of the present invention Figure 18 -(b) shown, there are about 23 microspheres in the central region and about 22 in the upper region. The microspheres are evenly distributed, effectively reducing the concentration change, thereby improving the detection accuracy. Although the microsphere distribution can be used to infer the flow field, over time, the accumulation of attached microspheres may affect the experimental judgment. Therefore, this embodiment also designs a microsphere trajectory tracking experiment to dynamically evaluate the flow field distribution. The results are as Figure 18 -(c) shown. In the simple chamber, the microsphere movement trajectories are discretely distributed, and the flow rate in the central region is much higher than that of the side wall, resulting in concentration diffusion. In the bionic detection chamber, the microspheres move synchronously, with no obvious velocity gradient, and the flow field is uniform and stable. This proves that the bionic detection chamber structure of the present invention can effectively avoid concentration diffusion.

[0068] Finally, in combination with a sodium ion sensor for actual signal measurement, 1 mM / L sodium chloride solution is injected into the simple chamber and the bionic detection chamber respectively. After the signal is stable, 100 mM / L and 10 mM / L sodium chloride standard solutions are injected for detection respectively, as Figure 18 -(d) shown. Figure 18 At position ① in -(d), it shows that in the simple chamber, the solvent enters the cavity in a ray flow without obstruction, and the electrical signal response is faster. In the bionic detection chamber, the internal structure inhibits the flow rate, resulting in a delayed initial response. However, after the cavity is wetted, the response time is significantly improved. Figure 18 At position ② in -(d), it shows that there are obvious spike signals during the test of the simple chamber, which will interfere with the detection results, while the test signal of the bionic detection chamber is relatively stable. Figure 18- The third position in (d) shows that the bionic detection chamber stabilizes within 15 s, while the simple chamber takes nearly 50 s to stabilize. This is because after the chamber is wetted, the bionic detection chamber makes the axial flow rate of the new reagent uniform, quickly replaces the old solution, and reduces diffusion. In the unstructured simple chamber, the old and new solvents mix slowly and it takes longer to stabilize. Through the above three experiments, it is fully demonstrated that the bionic detection chamber significantly improves the internal flow field.

[0069] The fabrication of a multi-parameter electrochemical sensor composed of a working electrode and a reference electrode starts with the direct laser writing of a 3D porous graphene electrode. Scanning electron microscope (SEM) images show the appearance of the porous electrode based on laser-induced graphene, i.e., the LIG electrode, as Figure 19 shown. In addition, the characterization of LIG was also studied using Raman spectroscopy, as Figure 20 shown. Figure 20 - The three characteristic peaks shown in (a), the G peak at 1572 cm -1 , the D peak at 1350 cm -1 , and the 2D peak at 2680 cm -1 , confirm that the laser direct writing technology can convert the PI material into graphene.

[0070] Laser power is an important factor affecting the microscopic morphology and electroanalysis characteristics of porous LIG. Considering the CV response of LIG at different powers, as Figure 20 shown in (b), 7.5 W is selected as the optimal power. Figure 20 - The corresponding BET images shown in (c) also prove that the specific surface area of the laser-induced graphene with a power of 7.5 W is larger, which can provide more active sites and is thus very beneficial for electrochemical sensing. Figure 20 - (d) shows the cyclic voltammograms at different scan rates. Figure 20 - (e) shows that after 300 consecutive CV scans, the redox peaks of LIG show no obvious change. The relative standard deviations (RSDs) of the cathodic current and anodic current are 0.87% and 0.54% respectively, indicating that LIG has good electrochemical detection stability.

[0071] Then, after completing the complete electrode preparation steps, the relevant performances of potassium ions, sodium ions, and chloride ions are evaluated respectively to verify the performance of the electrode, as Figure 21 , Figure 22 , Figure 23 shown. First, the potassium ion test is carried out. The K + working electrode is placed in a low-concentration KCl standard solution of 0.1 mM / L for electrode activation. Then, potassium chloride solutions with different concentrations are dropped onto the electrode surface, and the changes in the electrode potential and potassium ion concentration are recorded in real time. The experimental results are as Figure 21As shown in -(a), the electrode potential increases stepwise with the increase of potassium ion concentration. At the same time, no significant drift phenomenon occurs, indicating that the electrode has good stability. Secondly, as can be seen from Figure 21 -(b), the electrode potential has a linear relationship with Log[K + in the concentration range of 1 - 32 mM / L, meeting the test requirements of 5 - 20 mM / L for human sweat. Then, an anti-interference test is carried out. In this embodiment, special membrane materials and surface modification technologies are adopted. Valinomycin doped in the potassium ion selective membrane mixture can improve the preferential adsorption of potassium ions in sweat, thus realizing the specific recognition of potassium ions. During the test, first add a certain concentration of potassium chloride solution to the measuring cup. After the signal is stable, successively add glucose, lactic acid, calcium chloride, urea and sodium chloride drop by drop. As Figure 21 shown in -(c), it can be clearly observed that the sensor only has obvious stepwise fluctuations when adding a solution containing potassium ions, and has no significant response to the remaining interfering ions. Finally, the return performance is also investigated. High-concentration K + solution is successively dropped on the electrode surface and then low-concentration solution is dropped successively. As can be observed from Figure 21 -(d), the return error of the sensor is small.

[0072] Similarly, for sodium ion testing, first place the Na + electrode in a low-concentration solution for activation. And successively add sodium chloride solutions with different concentrations, and record the change of electrode potential. As Figure 22 shown in -(a). The test results show that the sensor shows a rapid response to Na + , and the potential signal is stable. Further analysis shows that, as Figure 22 shown in -(b), the sensor meets the detection requirements in the range of 10 - 70 mM / L for human sweat. The sodium ion carrier X doped in the sodium ion selective membrane mixture can improve the adsorption of sodium ions in sweat, thus enhancing the recognition of specific ions by the membrane layer. Figure 22 The anti-interference test in -(c) verifies that the sensor has good selectivity and anti-interference ability. Figure 22 The repeatability test in -(d) shows that the return error of the sensor is small.

[0073] Different from the above modification based on the selective membrane, the detection of chloride ions uses an Ag / AgCl electrode. In the experiment, sodium chloride solutions with different concentrations are successively dropped on the chloride ion sensor, and the change of the detected potential with the concentration is recorded. As Figure 23 shown, the results show that the sensor shows a rapid and stable EMF response to different concentrations of NaCl. In addition, as can be seen from Figure 23It can be seen that the sensor is applicable to the detection range of 10 - 50 mM / L of human sweat. Both the anti-interference test and the repeatability test show good performance, further verifying the reliability and stability of the sensor.

[0074] To further verify the actual detection effect under wearable conditions, in this embodiment, the wearable sweat detection system is used to monitor the sweat of a subject riding an elliptical trainer in a 25°C indoor environment for 40 minutes. During the entire test process, the system is fixed on the subject's arm for continuous testing. The results are as Figure 24 shown. The system can stably and continuously detect the information of Na + , K + and Cl - concentrations in sweat, which also proves that the system can meet the requirements of real-time continuous sweat monitoring and has great potential in health monitoring.

[0075] The wearable microfluidic sweat detection system of the present invention can stably and continuously detect Na + , K + , Cl - . By referring to the vein network structure to optimize the microfluidic cavity design, the stability of the flow field is improved, thus significantly enhancing the detection accuracy. At the same time, the three-dimensional conductive porous structure of LIG can quickly transfer electrons and enhance the reaction, making the multi-parameter electrochemical sensor detect ions more sensitively and accurately. Finally, it is integrated into a watch to achieve real-time transmission and dynamic display of detection data. The in vivo test results show that the system has good performance and can meet the requirements of wearable sweat detection. Compared with the traditional sweat detection system, the system shows higher detection accuracy and plays a positive role in promoting the development of wearable sweat detection sensors.

[0076] The following introduces the preparation steps of the sweat detection system of the present invention.

[0077] Step 1: Prepare a bionic microfluidic chip. First, perform three-dimensional modeling on the bionic microfluidic chip mold through Solidworks software. Secondly, according to the designed model, use a micro-nano 3D printer to make a resin template. Subsequently, when the PDMS prepolymer and the curing agent are mixed at a mass ratio of 10:1, add 10% wt of n-hexane, pour the mixture onto the resin template, and cure it at room temperature for 48 h to form a PDMS layer with bionic microfluidic channels. Finally, peel the PDMS layer from the resin template for subsequent use.

[0078] Step 2: Prepare the LIG electrode. After designing the electrode using commercial graphic software (CorelDraw) on a computer, a pre-designed pattern is rapidly engraved onto the surface of the PI film using a commercial 10.6 μm carbon dioxide pulsed laser to create a porous graphene pattern. The laser power and speed are set at 7.5 W and 150 mm / s respectively. The thickness of the PI film is approximately 75 μm.

[0079] Step 3: Prepare the electrode modification solution. The sodium ion-selective membrane mixture consists of 1 wt% Sodium ionophore X, 0.55 wt% Na-TFPB, 33 wt% PVC, and 65.45 wt% DOS, with tetrahydrofuran as the solvent. To avoid solution volatilization, 100 mg of the sodium ion-selective membrane mixture and 660 μl of tetrahydrofuran are placed in a sealed container and magnetically stirred to mix thoroughly. The potassium ion-selective membrane mixture consists of 2 wt% valinomycin, 0.5 wt% NaTPB, 32.7 wt% PVC, and 64.7 wt% DOS, with cyclohexanone as the solvent. Similarly, 100 mg of the potassium ion-selective membrane mixture and 350 μl of cyclohexanone are placed in a sealed container and magnetically stirred to mix thoroughly. The chloride ion working electrode consists of Ag / AgCl, where the ratio of Ag / AgCl is 60:40, and is used to detect the chloride ion concentration in sweat. The reference membrane mixture is composed of 395.5 mg of PVB (B-98), 250 mg of NaCl, 250 mg of AgNO3, 10 mg of F127, 1 mg of multi-walled carbon nanotubes, and 5 mL of methanol. Before preparation, 395.5 mg of PVB is dissolved in 5 mL of methanol, and a 10 wt% PVB solution is prepared under ultrasonic treatment. Subsequently, 250 mg of NaCl and 250 mg of AgNO3 are added to the 5 mL 10 wt% PVB solution to obtain a milky white mixture. After ultrasonic treatment for approximately 30 min, the membrane mixture is placed under a high-power light source (120 V / 15 w) for 10 minutes, and the solution gradually turns light purple. Finally, 10 mg of F127 and 1 mg of multi-walled carbon nanotubes are added, and the mixture is magnetically stirred until thoroughly mixed. The sealed bottle is wrapped with copper foil for later use. Through the above preparation process, sodium ion-selective modification solution, potassium ion-selective modification solution, chloride ion detection modification solution, and reference modification solution are finally obtained. After completing the flexible electrode array, just spin-coat an appropriate amount of the modification solution on the specific working area, and an ion-selective electrode can be obtained after drying.

[0080] Step 4: Prepare the multi-parameter electrochemical sensor. The preparation steps are as Figure 25As shown below. First, a commercially available 10.6 μm carbon dioxide pulsed laser is used to quickly engrave a pre-designed pattern onto the surface of the PI film to create a porous graphene pattern. Then, an Ag / AgCl paste is spin-coated onto the chloride ion selective working electrode and the reference electrode. The diameters of both the working electrode and the reference electrode are 3 mm. After complete drying, a layer of PEDOT:PSS is electroplated onto the sodium ion working electrode and the potassium ion working electrode using the constant current method, with a current density of 2 mA cm -2 , and the total charge is 10 mC. As an ion-electron transfer layer in the electrochemical sensor, PEDOT:PSS can enhance the ion exchange between the sensor and the ions in the surrounding solution, thereby improving the sensitivity and response speed of the sensor. After electroplating, 2 μL of the sodium ion selective membrane mixture and the potassium ion selective membrane mixture are dropped onto the corresponding electrodes to prepare the ion selective membranes. Finally, the common reference electrode is modified by spin-coating 2 μL of the reference modification solution onto the Ag / AgCl electrode, and the electrode surface is allowed to dry. The cross-sectional view of the obtained multi-parameter electrochemical sensor electrode is as shown in Figure 4 .

[0081] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0082] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A wearable microfluidic sweat detection system, characterized in that, Comprising: A bionic microfluidic chip, the bionic microfluidic chip includes a chip body, a sweat inlet, a sweat outlet and a plurality of bionic detection chambers provided on the chip body. The plurality of bionic detection chambers are connected end to end, the bionic detection chamber at the first end is connected to the sweat inlet, and the bionic detection chamber at the last end is connected to the sweat outlet. Each bionic detection chamber includes a bionic detection chamber body, an outer microcolumn array and an inner microcolumn array concentrically arranged inside the bionic detection chamber body. The outer microcolumn array includes a plurality of outer microcolumns evenly spaced along the circumferential direction, and the inner microcolumn array includes a plurality of inner microcolumns evenly spaced along the circumferential direction; A multi-parameter electrochemical sensor, including a substrate and a plurality of detection electrodes provided on the substrate. One ends of the plurality of detection electrodes are respectively in contact with the plurality of bionic detection chambers one by one; A wearable device, connected to the other ends of the plurality of detection electrodes, for receiving and processing a plurality of detection signals transmitted by the multi-parameter electrochemical sensor.

2. The wearable microfluidic sweat detection system according to claim 1, wherein, Both the outer microcolumns and the inner microcolumns are arc-shaped protruding towards the inner wall of the bionic detection chamber body.

3. The wearable microfluidic sweat detection system according to claim 1, characterized in that, A main channel is connected between the bionic detection chamber at the first end and the sweat inlet, a transition channel is connected between adjacent bionic detection chambers, and an outlet channel is connected between the bionic detection chamber at the last end and the sweat outlet.

4. The wearable microfluidic sweat detection system according to claim 3, wherein The width of the main channel is greater than the gap between the inner wall of the bionic detection chamber body and the outer microcolumns, and the gap between the inner wall of the bionic detection chamber body and the outer microcolumns is equal to the gap between the outer microcolumns and the inner microcolumns.

5. The wearable microfluidic sweat detection system according to claim 1, wherein The number of the outer microcolumns is ten, the gap angle between adjacent outer microcolumns is 12°, the number of the inner microcolumns is four, the gap angle between adjacent inner microcolumns is 30°, and the gap between the outer microcolumns and the inner microcolumns is 200μm.

6. The wearable microfluidic sweat detection system according to claim 1, wherein The diameter of the bionic detection chamber body is 4000μm and the height is 200μm.

7. The wearable microfluidic sweat detection system according to claim 3 or 4, characterized in that The width of the main channel is 250μm.

8. The wearable microfluidic sweat detection system according to claim 1, characterized in that, The number of the bionic detection chambers is four, the multi-parameter electrochemical sensor includes four detection electrodes, and the four detection electrodes are a reference electrode, a chloride ion selective working electrode, a potassium ion selective working electrode and a sodium ion selective working electrode respectively.

9. The wearable microfluidic sweat detection system according to claim 8, wherein, The reference electrode includes a first Ag / AgCl layer and a PVB / CNT layer stacked on the first Ag / AgCl layer. The chloride ion selective working electrode includes a second Ag / AgCl layer. The potassium ion selective working electrode includes a first LIG electrode, a first ion-electron transfer layer stacked on the first LIG electrode, and a potassium ion selective membrane stacked on the first ion-electron transfer layer. The sodium ion selective working electrode includes a second LIG electrode, a second ion-electron transfer layer stacked on the second LIG electrode, and a sodium ion selective membrane stacked on the second ion-electron transfer layer.

10. The wearable microfluidic sweat detection system according to claim 1, wherein The wearable device includes a watch. The bionic microfluidic chip and the watch are respectively bonded to opposite sides of the substrate of the multi-parameter electrochemical sensor. The sweat inlet of the bionic microfluidic chip is in contact with the skin, and the plurality of receiving electrodes of the watch are respectively connected to the other ends of the plurality of detection electrodes of the multi-parameter electrochemical sensor.

Images