Microfluidic sweat sensor and application

Abstract

The invention provides a microfluidic sweat sensor, and relates to the technical field of wearable sensors. The sensor comprises a base plate and a top plate which are oppositely arranged, a through hole is formed in the top of the base plate, a sweat channel is arranged between the base plate and the top plate, the sweat channel is connected with the through hole, and a sweat outlet is formed in the other end of the sweat channel; a plurality of parallel electrodes which are electrically connected with an external sensing circuit are arranged in the sweat channel of the substrate, an adsorption block is further arranged at the sweat outlet of the substrate, and the adsorption block is used for adsorbing and removing sweat in the sweat channel. The device can realize real-time sustainable measurement of sweat, and has the characteristics of quick response, high sensitivity, wide application and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of wearable sensors, and in particular to a microfluidic sweat sensor and its application. Background Art

[0002] Wearable sensors have attracted extensive research interest due to their portability and comfort. By measuring body fluids secreted by the human body, they can monitor human health in real time, showing broad application prospects. Among all body fluids secreted by the human body, sweat has the advantages of high secretion volume and rich biomarkers, making it an ideal object for human health monitoring. Portable sweat sensors have important research and application value. Among all body fluids secreted by the human body, sweat has the advantages of high secretion volume and rich biomarkers, such as Na + 、Cl - , K + , metabolites (such as glucose, lactic acid, uric acid, dopamine), as well as nitrogen-containing compounds such as amino acids and urea, can be used as ideal objects for human health monitoring. Portable sweat sensors have important research and application value.

[0003] In recent years, sweat detection has made significant progress, with key measurement methods including colorimetry, fluorescence, and electrochemistry. With the advancement of microelectronics and flexible materials, wearable sweat sensors have become a research hotspot. Wearable sensors, attached to the skin surface, can non-invasively and in real time monitor biomarkers in sweat, providing a convenient solution for health monitoring. However, in health monitoring applications, achieving sustainable sweat measurement and preventing the impact of sweat accumulation on sensor test accuracy remain challenges for wearable sweat sensors. Summary of the Invention

[0004] The object of the present invention is to provide a microfluidic sweat sensor.

[0005] The present invention provides a microfluidic sweat sensor, comprising a substrate and a top plate arranged opposite to each other, a through hole provided on the top of the substrate, and a sweat channel provided between the substrate and the top plate, the sweat channel being connected to the through hole and having a sweat outlet provided at the other end; the substrate is provided with a plurality of parallel electrodes electrically connected to an external sensing circuit in the sweat channel, and an adsorption block is also provided on the substrate at the sweat outlet, the adsorption block being used to adsorb and remove sweat in the sweat channel.

[0006] Optionally, the substrate is provided with a substrate in the sweat channel, a plurality of parallel electrodes are deposited on the surface of the substrate and are parallel to each other, and gaps exist between adjacent parallel electrodes.

[0007] Optionally, the substrate comprises a hard carrier or a flexible film, and the hard carrier comprises glass or a silicon wafer.

[0008] Optionally, the flexible film comprises a polymer film made of polyimide, polytetrafluoroethylene or polyethylene terephthalate.

[0009] Optionally, the parallel electrodes include a plurality of functional test electrodes and a reference electrode, and the functional test electrodes include metal oxide electrodes and / or metal electrodes coated with enzymes or nucleic acid aptamers, and the reference electrode includes an Ag / AgCl electrode.

[0010] Optionally, the materials of the substrate and the top plate independently include polydimethylsiloxane, polymethyl methacrylate or cycloolefin polymer.

[0011] Optionally, the adsorption block is made of sponge or cotton.

[0012] Optionally, a slide rail is provided on one side of the substrate located at the sweat outlet, and the adsorption block is slidably arranged on the slide rail in a direction approaching to / away from the sweat outlet.

[0013] Optionally, the material of the slide rail includes polylactic acid, acrylonitrile-butadiene-styrene copolymer or photosensitive resin

[0014] In a second aspect, the present invention provides a sensor detection method, comprising: after the microfluidic sweat sensor is attached to the human skin and worn, the sweat to be tested enters the sweat channel and the potential, conductivity and AC impedance are measured through parallel electrodes to realize the identification of sweat components; after the measurement, the adsorption block is moved close to the sweat outlet to adsorb and remove the sweat in the sweat channel. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a partial structural diagram of a microfluidic sweat sensor provided by the present invention;

[0016] Figure 2 1 is a top view and a cross-sectional view of a microfluidic sweat sensor provided by the present invention;

[0017] Figure 3 This is a three-dimensional scatter plot of potential, conductance, and AC impedance of a microfluidic sweat sensor provided by the present invention when measuring a test solution with a concentration of 10 mM;

[0018] Figure 4 A microfluidic sweat sensor provided by the present invention measures the potential, conductance and AC impedance of sweat of two people under different exercise states;

[0019] Figure 5An electrical response diagram of a microfluidic sweat sensor provided by the present invention when measuring human sweat.

[0020] Description of reference numerals:

[0021] 1. Substrate; 2. Parallel electrodes; 3. Top plate; 4. Slide rail; 5. Slide block; 6. Adsorption block. Detailed implementation manners

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings as understood by those of ordinary skill in the art to which the present invention pertains.

[0023] Refer to Figure 1 , a microfluidic sweat sensor provided by the present invention includes a substrate and a top plate 3 arranged opposite to each other. A through hole is formed at the top of the substrate, and a sweat channel is formed between the substrate and the top plate 3. One end of the sweat channel is connected to the through hole, and the other end is provided with a sweat outlet. During the actual measurement process, after sweat enters the sweat channel, the entering sweat is sealed in the sweat channel by the air pressure acting through the through hole communicating with the atmosphere, and the sweat that has completed the measurement is discharged through the sweat outlet.

[0024] Actually, multiple parallel electrodes 2 electrically connected to an external sensing circuit are arranged in the substrate within the sweat channel. Specifically, a substrate 1 is arranged in the substrate within the sweat channel, and multiple parallel electrodes 2 are deposited on the surface of the substrate 1. The multiple parallel electrodes 2 cooperate with each other to measure the potential, conductivity, and AC impedance in the sweat, so as to realize the determination of the components in the sweat. Further, the top plate 3 can be in a "C" shape and embedded in the substrate 1 to form a sweat channel. At the same time, the end of the top plate 3 intersects with the parallel electrodes 2, so that the parallel electrodes 2 can be electrically connected to an external sensing circuit.

[0025] Actually, there are gaps between adjacent parallel electrodes 2 on the surface of the substrate 1, so that the parallel electrodes 2 are in an electrically isolated state, so that a path is formed when the sweat to be measured flows between two adjacent parallel electrodes 2, and then the change in the components in the sweat to be measured is detected through the change in the electrical signal.

[0026] In some embodiments, the substrate 1 in the sweat channel comprises a rigid substrate or a flexible film. Specifically, the rigid substrate comprises glass or silicon, and the flexible film comprises a polymer film made of polyimide, polytetrafluoroethylene, or polyethylene terephthalate. In practice, the substrate 1 can be bonded to the substrate surface and participate in the formation of the sweat channel, allowing a gap for sweat flow between the substrate 1 and the top plate 3. Specifically, the spacing between the substrate 1 and the top plate 3 is sufficient to allow sweat flow, for example, 0.5 mm to 1.5 mm.

[0027] In practice, the overall material of the microfluidic sweat sensor can be made of a flexible material, allowing it to bend, thereby better fitting the human skin and improving wearer comfort. Furthermore, the parallel electrodes 2 can be patterned on the surface of the substrate 1 using a mask or photolithography process, facilitating customization of the parallel electrodes 2 and achieving specific functions. In fact, the substrate 1 can be directly used as a base.

[0028] In some embodiments, the parallel electrodes 2 on the surface of the substrate 1 include multiple functional test electrodes and a reference electrode. Specifically, the functional test electrodes include metal oxide electrodes and / or metal electrodes coated with enzymes or nucleic acid aptamers, and the reference electrode includes an Ag / AgCl electrode. In addition, the materials of the substrate and the top plate 3 independently include polydimethylsiloxane, polymethyl methacrylate, or cycloolefin polymer. Specifically, the metal electrodes may include NiOx, TiOx, or IrOx. In addition, different types of metal electrodes can be selected according to different test requirements.

[0029] In practice, the top plate 3, base plate, and substrate 1 of the microfluidic sweat sensor can be designed using template graphics to create sweat channel structures of varying shapes. This facilitates the realization of different functions of the microfluidic sweat sensor and its wearability in different locations. Furthermore, different materials can be selected depending on the location where the microfluidic sweat sensor is worn.

[0030] In fact, the base plate is further provided with a guide rail at the sweat outlet, and an adsorption block 6 is slidably provided on the base plate. The adsorption block 6 is slidably provided on the slide rail 4 in a direction approaching or moving away from the sweat outlet. In addition, when the adsorption block 6 moves to the sweat outlet, it can completely close the sweat outlet, so that the adsorption block 6 can absorb and remove sweat in the sweat channel.

[0031] In some embodiments, the material of the slide rail 4 may include polylactic acid, acrylonitrile-butadiene-styrene copolymer, or photosensitive resin, and the material of the adsorption block 6 may include sponge or cotton. In practice, at least the portion of the adsorption block 6 that contacts the sweat outlet is made of sponge or cotton, thereby adsorbing sweat in the sweat channel.

[0032] In fact, the present invention also provides a detection method for a microfluidic sweat sensor, including: after the microfluidic sweat sensor is attached to the human skin and worn, the sweat to be tested enters the sweat channel and the potential, conductivity and AC impedance are measured through parallel electrodes 2 to realize the identification of sweat components; after measurement, the adsorption block 6 is moved close to the sweat outlet to adsorb and remove the sweat in the sweat channel.

[0033] In some embodiments, the substrate 1 can be made of polyimide, with four parallel electrodes 2 deposited on the polyimide substrate 1: one TiO2 / Ti electrode and three AgCl / Ag electrodes. Both the top plate 3 and the base plate can be supported by polydimethylsiloxane, with a circular through-hole formed at one end of the top plate 3. Furthermore, the slide rail 4 and slider 5 connected to the base plate can be molded from photosensitive resin. The slider 5 can be slidably mounted on the slider 5, and an adsorption block 6 made of a sponge material can be attached to the slider 5.

[0034] In some embodiments, when the microfluidic sweat sensor is working, it needs to be worn in contact with the skin, and after the sweat enters the sweat channel, it flows and transmits in the sweat channel. After contacting the parallel electrodes 2, the potential difference between the TiO2 / Ti electrode and the AgCl / Ag electrode, as well as the conductivity and AC impedance between the two AgCl / Ag electrodes are measured to obtain electrical signals and then perform external analysis to realize the identification of sweat components.

[0035] In some embodiments, a method for manufacturing a microfluidic sweat sensor includes the following steps:

[0036] S1. Using a polyimide film as a substrate 1, forming parallel metal Ti electrodes and Ag electrodes with a length of 100 nm on the surface of the substrate 1 by electron beam evaporation, immersing the substrate in a mixed solution of NaF and Na2SO4 at a voltage of 1 V to obtain a TiO2 / Ti working electrode by an electrochemical method, and then immersing the substrate in 1 mol / L hydrochloric acid at a voltage of 1 V to obtain an AgCl / Ag working electrode by an electrochemical method;

[0037] S2, polydimethylsiloxane and a catalyst were mixed in a volume ratio of 10:1 and poured into the template, dried and cured at 70°C for 1 hour, and then peeled off to obtain a top plate 3; the substrate 1 deposited with the working electrode in S1 was soaked in a 3 mol / L potassium hydroxide solution for 1 minute, then transferred to 0.3 mol / L 3-mercaptopropyltrimethoxysilane and soaked for 1 hour, and then the soaked substrate 1 and the top plate were simultaneously treated with oxygen plasma for 310 seconds, and then the two were bonded and fixed under the action of mechanical force;

[0038] S3. Use 3D printing technology and photosensitive resin to print the slide rail 4 and the slider 5. After assembling the slide rail 4 and the slider 5, install the slide rail 4 on the bottom of the substrate 1 and make the slider 5 located at the sweat outlet of the sweat channel. After the adsorption block 6 made of sponge material is glued and fixed on the side of the slider 5, the construction of the microfluidic sweat sensor is completed.

[0039] In some embodiments, the microfluidic sweat sensor provided by the present invention is used to measure 10mmol / L NaCl solution, KCl solution, MgCl2 solution, CaCl2 solution, lactic acid solution, glucose solution, and urea solution. During the measurement, the phase is obtained by the potential difference between the TiO2 / Ti electrode and one AgCl / Ag electrode, and the conductance and 100Hz AC impedance signal are measured by applying DC and AC voltages between the other two AgCl / Ag electrodes. This can achieve the identification of NaCl, KCl, MgCl2, CaCl2, lactic acid, glucose, and urea, such as Figure 4 shown.

[0040] In some embodiments, the microfluidic sweat sensor provided by the present invention was used to conduct sweat tests on two volunteers. The microfluidic sweat sensors were worn on the backs of the volunteers' arms, and the potential, conductance, and AC impedance were measured in three exercise states: walking, jogging, and sprinting. Figure 5 As shown. Figure 5 It can be seen that there are significant differences in the sweat composition in the three exercise states, and during the reset time period of the three exercise states during the measurement process, the sweat in the sweat channel can be removed by the adsorption block 6 to avoid the influence of sweat residue on the accuracy of the results during the measurement process.

[0041] While the embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations of these embodiments are possible. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the claims. Furthermore, the invention described herein is susceptible to other embodiments and may be practiced or implemented in a variety of ways.

Claims

1. A microfluidic sweat sensor, characterized in that: The invention comprises a base plate and a top plate arranged opposite to each other, a through hole being provided on the top of the base plate, and a sweat channel being provided between the base plate and the top plate, the sweat channel being connected to the through hole and having a sweat outlet at the other end; the base plate is provided with a plurality of parallel electrodes electrically connected to an external sensing circuit in the sweat channel, and an adsorption block is further provided on the base plate at the sweat outlet, and the adsorption block is used to adsorb and remove sweat in the sweat channel.

2. The microfluidic sweat sensor according to claim 1, characterized in that The substrate is located in the sweat channel and is provided with a substrate, and a plurality of parallel electrodes are deposited on the surface of the substrate and are parallel to each other, and there are gaps between adjacent parallel electrodes; wherein, the substrate includes a hard carrier or a flexible film, and the hard carrier includes glass or silicon wafer, and the flexible film includes a polymer film made of polyimide, polytetrafluoroethylene or polyethylene terephthalate.

3. The microfluidic sweat sensor according to claim 1, characterized in that The parallel electrodes include a plurality of functional test electrodes and a reference electrode, wherein the functional test electrodes include metal oxide electrodes and / or metal electrodes coated with enzymes or nucleic acid aptamers, and the reference electrode includes an Ag / AgCl electrode.

4. The microfluidic sweat sensor according to claim 1, characterized in that The materials of the base plate and the top plate independently include polydimethylsiloxane, polymethyl methacrylate or cycloolefin polymer; and / or the material of the adsorption block includes sponge or cotton.

5. The microfluidic sweat sensor according to claim 1, characterized in that The substrate is provided with a slide rail on one side of the sweat outlet, and the adsorption block is slidably arranged on the slide rail in a direction approaching / moving away from the sweat outlet; wherein the material of the slide rail includes polylactic acid, acrylonitrile-butadiene-styrene copolymer or photosensitive resin.

6. A detection method for a microfluidic sweat sensor according to any one of claims 1 to 5, characterized in that: include: After the microfluidic sweat sensor is attached to human skin and worn, the sweat to be tested enters the sweat channel and the potential, conductance and AC impedance are measured through parallel electrodes to identify the sweat components; After measurement, the adsorption block is moved close to the sweat outlet to adsorb and remove the sweat in the sweat channel.

Images