Conductive hydrogel fiber membrane, method for manufacturing same, and system for

Abstract

The invention provides a conductive hydrogel fiber membrane, a manufacturing method thereof and a body signal measuring system. The conductive hydrogel fiber membrane is formed by swelling hydrogel fibers containing conductive components in water, and the conductive hydrogel fiber membrane is prepared by a'spinning-crosslinking-soaking 'method. The prepared conductive hydrogel fiber membrane has good air permeability and water-retaining property, has relatively low electrode-skin interface impedance, can be activated and reused through an ionic solution in the use process, can realize high-fidelity, continuous and long-term body signal acquisition, and realizes diversified interaction centered by human beings.

Description

Technical Field

[0001] The present invention belongs to the field of flexible electronic technology, and in particular relates to a conductive hydrogel fiber electrode and a preparation method thereof, and a body signal measuring system formed by using the conductive hydrogel fiber electrode. Background Art

[0002] The development of breathable, reusable, ultrathin bioelectrodes and sensors for comfortable and continuous monitoring of physiological data is essential for long-term health tracking. The current common strategy is to use dry electrodes and sensors with ultrathin polymer substrates, such as graphene, conductive polymers, metal nanowires, and metal films. These electrodes and sensors have a thickness of several microns and nanometers, can fit with human skin through van der Waals forces / adhesion interfaces, and show good breathability without obvious skin inflammation. Another approach is to create porous structures to achieve breathability and promote sweat evaporation. Microfabrication, sugar templates, breath maps, phase separation, and electrospinning methods have been developed to form these porous electrodes. For example, patent CN113614906 A reports polymer-based fiber meshes with good surface conformability, stretchability, gas and moisture permeability, and stability.

[0003] Due to the different electrochemical properties between the skin and the electrode, there is a half-cell potential between them, which can significantly affect the quality and accuracy of physiological signals, as well as electrode polarization and skin irritation. In order to mitigate the impact, electrode materials with lower half-cell potentials, such as silver / silver chloride (Ag / AgCl), are selected in combination with hydrogel electrodes to help minimize potential interference and polarization effects. However, the reported block hydrogel materials can be tightly attached to the surface of skin tissue, have poor air permeability, do not allow gas and liquid to penetrate, can cause varying degrees of itching or inflammation, and are easily dehydrated and displaced during daily activities, making them unsuitable for long-term wear. Summary of the invention

[0004] The present invention proposes an ultra-thin, breathable and conductive hydrogel fiber membrane manufactured by spinning-crosslinking-immersion technology. The conductive hydrogel fiber membrane has surface conformability, low interface impedance, air and water permeability, moisture retention, biocompatibility and reusability. Further, it is used for body signal monitoring and interactive interface. The technical problems of poor air permeability and water retention of conductive hydrogel materials and high half-battery potential between flexible dry electrodes and skin in the prior art are solved.

[0005] In order to solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0006] A conductive hydrogel fiber membrane comprises hydrogel fibers, a water retaining agent and a conductive component; the water retaining agent and the conductive component are dispersed in the hydrogel fibers; the fiber membrane formed by connecting the hydrogel fibers is a porous structure with air and water permeability.

[0007] Furthermore, the material of the hydrogel fiber is one or more combinations of polyvinyl alcohol and its derivatives, gelatin and its derivatives, polymethacrylated gelatin, cellulose, chitosan and its derivatives, collagen and its derivatives, methacrylated polylysine or silk fibroin and its derivatives.

[0008] Furthermore, the water retaining agent is one or a combination of panthenol, glycerin, betaine, hyaluronic acid or calcium chloride; the mass fraction of the water retaining agent ranges from 0 to 50wt%.

[0009] Furthermore, the hydrogel fiber contains ions, electronic conductors or a combination of ions and electronic conductors to make the hydrogel conductive; the ions are one or more combinations of hydrogen ions, sodium ions, chloride ions, potassium ions, calcium ions, magnesium ions, silver ions, ammonium ions, phosphate ions, oxygen ions, nitrate ions or carbonate ions; the electronic conductor is one or more combinations of graphene, carbon nanotubes, carbon black, silver nanowires, gold nanowires, conductive polymers, transition metal carbides, transition metal nitrides or transition metal carbonitrides.

[0010] Furthermore, the water content of the hydrogel fiber is higher than 80%; the diameter of the hydrogel fiber is distributed between 50 nanometers and 2 micrometers; and the thickness of the conductive hydrogel fiber membrane is between 5 and 100 micrometers.

[0011] Furthermore, the conductivity of the hydrogel fiber membrane is activated by infiltrating an ion-containing aqueous solution to achieve long-term repeated use.

[0012] Furthermore, the elongation at break of the conductive hydrogel fiber membrane is 20%-160%.

[0013] Furthermore, the impedance between the conductive hydrogel fiber membrane and the skin at 10Hz ranges from 10 to 100 kΩ / cm2; and the half-cell potential formed with Ag / AgCl is less than 0.05V.

[0014] The present invention also discloses a method for preparing a conductive hydrogel fiber membrane, which comprises three steps of spinning-crosslinking-immersing:

[0015] Step 1, a spinning method is to form a fiber membrane composed of gel material fibers containing a conductive component and a water-retaining agent, the method comprising one or more combinations of electrospinning, blow spinning, wet spinning, dry spinning or dry-jet wet spinning;

[0016] Step 2: The cross-linking method is to make the fiber membrane insoluble in water, and the method includes one or more combinations of thermal crystallization, cold cross-linking, thermal cross-linking, chemical cross-linking or photo cross-linking;

[0017] Step 3: The immersion method is to transform the fiber membrane into a conductive hydrogel fiber membrane, and the method comprises immersing the fiber membrane in an aqueous solution containing a water retaining agent, ions or a combination thereof.

[0018] The present invention also discloses a body signal measuring system of a conductive hydrogel fiber membrane, comprising:

[0019] one or more conductive hydrogel fiber membranes;

[0020] Signal acquisition and measurement module;

[0021] A connection circuit provided between the signal acquisition and measurement module and the conductive hydrogel fiber membrane;

[0022] The conductive hydrogel fiber membrane is attached to the surface of the measurement object.

[0023] Furthermore, the body signal includes one or a combination of electrocardiogram, electromyogram, electroencephalogram, electrooculogram, strain, temperature, pressure or sweat.

[0024] Furthermore, the signal acquisition and measurement module includes wired signal transmission, wireless signal transmission and a combination thereof.

[0025] Furthermore, the uses of the physiological electrical signal system include human body signal monitoring, animal body signal monitoring, and plant body signal monitoring.

[0026] Furthermore, the uses of the physiological electrical signal system include but are not limited to human-computer interaction, human-plant interaction, human-human interaction, and any two or more combinations thereof.

[0027] The conductive hydrogel fiber membrane and its manufacturing method and body signal measurement system of the present invention have the following advantages:

[0028] 1. The conductive hydrogel fiber membrane provided by the present invention has the advantages of both conductive hydrogel materials and porous structures, and has the advantages of being ultra-thin, breathable, water-permeable, moisturizing, good biocompatibility, low half-cell potential and reusable.

[0029] 2. The "spinning-crosslinking-immersion" technology provided by the present invention for the manufacture of conductive hydrogel fiber membranes has universal applicability for forming hydrogel fibers from a variety of hydrogel materials, has low manufacturing costs, and is suitable for large-scale production.

[0030] 3. The conductive hydrogel fiber membrane electrodes and sensors provided by the present invention can be well attached to the skin, can obtain body signal characteristics in a long-term and high-fidelity manner, and can be used in a variety of interactive interfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1It is a schematic diagram used to illustrate the preparation of conductive hydrogel fiber membrane using the "spinning-crosslinking-immersion" technology.

[0032] Figure 2 is a schematic diagram for illustrating conductive hydrogel fibers.

[0033] Figure 3 It is a schematic diagram used to illustrate the characteristics of conductive polyvinyl alcohol hydrogel fiber membrane.

[0034] Figure 4 Scanning electron microscopy images illustrating the evolution of nanofiber morphology during the preparation of polyvinyl alcohol hydrogel fiber membranes.

[0035] Figure 5 It is a schematic diagram used to illustrate the comparative effects of conductive hydrogel fiber membrane and commercial electrodes attached to the skin on the skin surface.

[0036] Figure 6 Schematic diagram for illustrating the skin interface impedance of the conductive hydrogel fiber membrane as an electrode and the half-cell potential difference between it and the commercial electrode.

[0037] Figure 7 It is a schematic diagram for illustrating the detection of human electrocardiographic and electromyographic signals based on conductive hydrogel fiber electrodes. DETAILED DESCRIPTION

[0038] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of a conductive hydrogel fiber membrane and a manufacturing method thereof and a body signal measurement system of the present invention in conjunction with the accompanying drawings.

[0039] The invention discloses a conductive hydrogel fiber membrane, comprising hydrogel fibers, a water retaining agent and a conductive component; the water retaining agent and the conductive component are dispersed in the hydrogel fibers; the fiber membrane formed by connecting the hydrogel fibers is a porous structure with air and water permeability.

[0040] The material of the hydrogel fiber is one or a combination of polyvinyl alcohol and its derivatives, gelatin and its derivatives, polymethacrylated gelatin, cellulose, chitosan and its derivatives, collagen and its derivatives, methacrylated polylysine or silk fibroin and its derivatives.

[0041] The type of the water retaining agent is one or a combination of panthenol, glycerin, betaine, hyaluronic acid or calcium chloride; the mass fraction of the water retaining agent ranges from 0 to 50wt%.

[0042] The hydrogel fiber contains ions, electronic conductors or a combination of ions and electronic conductors to make the hydrogel conductive; the ions are one or more combinations of hydrogen ions, sodium ions, chloride ions, potassium ions, calcium ions, magnesium ions, silver ions, ammonium ions, phosphate ions, oxygen ions, nitrate ions or carbonate ions; the electronic conductor is one or more combinations of graphene, carbon nanotubes, carbon black, silver nanowires, gold nanowires, conductive polymers, transition metal carbides, transition metal nitrides or transition metal carbonitrides.

[0043] The water content in the hydrogel fiber is higher than 80%; the diameter of the hydrogel fiber is distributed between 50 nanometers and 2 micrometers; and the thickness of the conductive hydrogel fiber film is between 5 and 100 micrometers.

[0044] The conductivity of the hydrogel fiber membrane is activated by infiltration with an ion-containing aqueous solution to achieve long-term repeated use.

[0045] The elongation at break of the conductive hydrogel fiber membrane is 20%-160%.

[0046] The impedance between the conductive hydrogel fiber membrane and the skin at 10Hz ranges from 10 to 100 kΩ / cm2; the half-cell potential formed with Ag / AgCl is less than 0.05V.

[0047] The present invention also discloses a method for preparing a conductive hydrogel fiber membrane, which comprises three steps of spinning-crosslinking-immersing:

[0048] Step 1, a spinning method is to form a fiber membrane composed of gel material fibers containing a conductive component and a water-retaining agent, the method comprising one or more combinations of electrospinning, blow spinning, wet spinning, dry spinning or dry-jet wet spinning;

[0049] Step 2: The cross-linking method is to make the fiber membrane insoluble in water, and the method includes one or more combinations of thermal crystallization, cold cross-linking, thermal cross-linking, chemical cross-linking or photo cross-linking;

[0050] Step 3: The immersion method is to transform the fiber membrane into a conductive hydrogel fiber membrane, and the method comprises immersing the fiber membrane in an aqueous solution containing a water retaining agent, ions or a combination thereof.

[0051] The present invention also discloses a body signal measuring system of a conductive hydrogel fiber membrane, comprising:

[0052] one or more conductive hydrogel fiber membranes;

[0053] Signal acquisition and measurement module;

[0054] A connection circuit provided between the signal acquisition and measurement module and the conductive hydrogel fiber membrane;

[0055] The conductive hydrogel fiber membrane is attached to the surface of the measurement object.

[0056] The body signal includes one or a combination of electrocardiogram, electromyogram, electroencephalogram, electrooculogram, strain, temperature, pressure or sweat.

[0057] The signal acquisition and measurement module includes wired signal transmission, wireless signal transmission and their combination.

[0058] The uses of physiological electrical signal systems include human body signal monitoring, animal body signal monitoring, and plant body signal monitoring.

[0059] The uses of the physiological electrical signal system include but are not limited to human-computer interaction, human-plant interaction, human-human interaction, and any two or more combinations thereof.

[0060] Figure 1 It is a schematic diagram used to illustrate the preparation of conductive hydrogel fiber membrane using the "spinning-crosslinking-immersion" technology.

[0061] The first embodiment of the method for preparing the conductive hydrogel fiber membrane:

[0062] (1) 0.5 g of polyvinyl alcohol (PVA) was dissolved in 5 mL of deionized water, and then stirred at 95°C and 600 rpm for 4 h to obtain a uniform 10 wt% PVA solution. 20% of panthenol was added to the PVA polymer solution and dispersed therein, and then stirred at 600 rpm for 2 h to dissolve it, and then the PVA / panthenol electrospinning solution was obtained after standing and degassing.

[0063] (2) extracting the prepared spinning solution with a syringe, setting the distance between the syringe needle and the fiber collector to 15 cm, applying a voltage of 30 kV, and the solution advancing speed of 10 mm / h, and collecting the solution on a roll covered with oil paper to obtain an electrospun fiber membrane with uniform and controllable thickness;

[0064] (3) covering the fiber membrane with a layer of silicone oil paper, heating the nanofiber mat at 150° C. for 5 minutes using a hot press, and peeling the heat-crosslinked fiber membrane from the silicone oil paper to obtain a PVA-panthenol (P-PVA) composite nanofiber membrane;

[0065] (4) The P-PVA fiber membrane was immersed in an aqueous solution containing 2 M NaCl for 4 hours to swell and obtain a conductive polyvinyl alcohol hydrogel fiber membrane.

[0066] Figure 2 is a schematic diagram for illustrating conductive hydrogel fibers. Figure 2 A is a schematic diagram of conductive polyvinyl alcohol hydrogel fiber. Figure 2 B is a schematic diagram of conductive gelatin hydrogel fiber. Figure 2C is a schematic diagram of conductive GelMA hydrogel fiber.

[0067] Figure 3 It is a schematic diagram used to illustrate the characteristics of conductive polyvinyl alcohol hydrogel fiber membrane. Figure 3 A is a schematic diagram of the thickness of the hydrogel fiber membrane after freeze drying. Figure 3 B is a schematic diagram of the hydrogel fiber membrane adhered to the skin surface. Figure 3 C is a schematic diagram of the load-bearing and water permeability of the hydrogel fiber membrane. Figure 3 D is a schematic diagram of the compatibility of the hydrogel fiber membrane with human umbilical vein endothelial cells.

[0068] Figure 4 This is a schematic diagram to illustrate the evolution of nanofiber morphology during the preparation of polyvinyl alcohol hydrogel fiber membranes. The diameter of electrospun polyvinyl alcohol fibers is about 330 nanometers, and the diameter of freeze-dried polyvinyl alcohol hydrogel fibers is about 400 nanometers.

[0069] Second embodiment of the method for preparing the conductive hydrogel fiber membrane:

[0070] (1) Add 2 g of acetic acid, 1 g of gelatin, and 1 g of glycerol into 2 mL of deionized water, respectively, and stir at 85 °C for 2 h to prepare a gelatin spinning solution.

[0071] (2) extracting the prepared spinning solution with a syringe, setting the distance between the syringe needle and the fiber collector to 15 cm, applying a voltage of 30 kV, and the solution advancing speed of 10 mm / h, and collecting the solution on a roll covered with oil paper to obtain an electrospun fiber membrane with uniform and controllable thickness;

[0072] (3) The gelatin fiber membrane was peeled off from the oil paper using a resin frame, and then a gelatin composite nanofiber membrane was prepared by chemical crosslinking. Specifically, an ethanol solution containing a 0.5 wt% 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride / N-hydroxysuccinimide (EDC / NHS) mixture was prepared, with a mass ratio of EDC to NHS of 4:1. Then, the gelatin fiber membrane was immersed in the solution for 24 hours and then washed with PBS buffer.

[0073] (4) The gelatin hydrogel fiber membrane was immersed in an aqueous solution containing 2M KCl and 20% panthenol for 4 hours to swell and obtain a conductive gelatin hydrogel fiber membrane.

[0074] The third embodiment of the method for preparing the conductive hydrogel fiber membrane:

[0075] (1) 30 wt % of acrylic acid, 10 wt % of gelatin, 1 wt % of polymethacrylylated gelatin (GelMA), 1 wt % of N-hydroxysuccinimide acrylic acid ester and 0.2 wt % of α-ketoglutaric acid were added to deionized water and stirred to prepare a spinning solution.

[0076] (2) The prepared spinning solution was extracted with a 2 mL syringe, the distance between the syringe needle and the fiber collector was set to 15 cm, a voltage of 30 kV was applied, the solution was pushed at a speed of 10 mm / h, and the solution was collected by covering the roll with oil paper to obtain an electrospun fiber membrane with uniform and controllable thickness;

[0077] (3) The gelatin fiber membrane was peeled off from the oil paper using a resin frame, and then the gelatin composite nanofiber membrane was prepared by a photocrosslinking method. Specifically, the GelMA fiber membrane was partially immersed in an anhydrous ethanol solution containing 2% photoinitiator, and then exposed to a 365 nm ultraviolet lamp for photocrosslinking.

[0078] (4) The GelMA hydrogel fiber membrane was immersed in an aqueous solution containing 2M NaCl and 20% panthenol for 4 hours to swell and obtain a conductive GelMA hydrogel fiber membrane.

[0079] Figure 5 It is a schematic diagram used to illustrate the effects of conductive hydrogel fiber membrane and commercial electrodes attached to the skin on the skin surface. Figure 5 A is a schematic diagram of two types of electrodes just attached to the skin; Figure 5 B is a schematic diagram of the skin surface after the two electrodes were attached to the skin for 6 hours and then removed. Long-term wearing of non-breathable commercial electrodes can cause skin redness.

[0080] Figure 6 It is a schematic diagram used to illustrate the impedance and electrode potential of the conductive hydrogel fiber membrane as an electrode. Figure 5 A is a schematic diagram of the impedance of the interface between different electrodes and skin at frequencies of 1-106 Hz. Figure 5 B is a schematic diagram of the half-cell potential difference between different electrodes and commercial electrodes.

[0081] For wireless human ECG signal monitoring, flexible conductive Ag / AgCl / polyester sheets were first attached to the back of the right and left hands, and then the conductive hydrogel fiber membranes were covered on the flexible conductive sheets, and the reference electrode was also attached to the left forearm. The three electrodes were then connected to a wireless miniaturized data acquisition system to record electrophysiological signals. The physiological potential module consists of a programmable gain amplifier and a digital filter. The signal is smoothed by a low-pass filter and converted by an analog-to-digital converter for further processing in a digital signal processor. The processed data / charts are wirelessly transmitted to a smartphone via low-power Bluetooth for real-time monitoring. For long-term ECG monitoring, the subjects wore the conductive hydrogel fiber membrane during the measurement and then peeled it off for storage. Before the next test, 100 microliters of sodium chloride solution were dropped on the conductive hydrogel fiber membrane to activate the hydrogel fiber membrane electrodes.

[0082] For wireless human electromyographic signal monitoring, two conductive hydrogel fiber membranes with flexible conductive Ag / AgCl / polyester sheets are attached to the brachioradialis muscle with a spacing of 5 cm, and a reference electrode is attached to the wrist. The wireless miniaturized data acquisition system is the same as that in Example 4, so repeated descriptions are omitted. Electromyographic signals are generated when the subject opens and clenches his fist. Different fist clenching strengths will produce electromyographic signals of different amplitudes and widths. These signals can be transmitted wirelessly to the client circuit, and the client circuit analyzes the electromyographic signal data in real time. When the signal amplitude exceeds the threshold of 0.8mV, the circuit activates devices such as displays, manipulators or electrical stimulators to achieve remote interaction.

[0083] Figure 7 It is a schematic diagram for illustrating the detection of human electrocardiographic and electromyographic signals based on conductive hydrogel fiber electrodes. Figure 7 A is a schematic diagram of human ECG signal; Figure 7 B is a schematic diagram of human electromyographic signals.

[0084] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A conductive hydrogel fiber membrane, characterized in that: It includes hydrogel fiber, water retaining agent and conductive component; the water retaining agent and conductive component are dispersed in the hydrogel fiber; the fiber membrane formed by connecting the hydrogel fibers is a porous structure with air permeability and water permeability.

2. The conductive hydrogel fiber membrane according to claim 1, characterized in that: The material of the hydrogel fiber is one or a combination of polyvinyl alcohol and its derivatives, gelatin and its derivatives, polymethacrylated gelatin, cellulose, chitosan and its derivatives, collagen and its derivatives, methacrylated polylysine or silk fibroin and its derivatives.

3. The conductive hydrogel fiber membrane according to claim 1, characterized in that: The type of the water retaining agent is one or a combination of panthenol, glycerin, betaine, hyaluronic acid or calcium chloride; the mass fraction of the water retaining agent ranges from 0 to 50wt%.

4. The conductive hydrogel fiber membrane according to claim 1, characterized in that: The hydrogel fiber contains ions, electronic conductors or a combination of ions and electronic conductors to make the hydrogel conductive; the ions are one or more combinations of hydrogen ions, sodium ions, chloride ions, potassium ions, calcium ions, magnesium ions, silver ions, ammonium ions, phosphate ions, oxygen ions, nitrate ions or carbonate ions; the electronic conductor is one or more combinations of graphene, carbon nanotubes, carbon black, silver nanowires, gold nanowires, conductive polymers, transition metal carbides, transition metal nitrides or transition metal carbonitrides.

5. The conductive hydrogel fiber membrane according to claim 1, characterized in that: The water content in the hydrogel fiber is higher than 80%; the diameter of the hydrogel fiber is distributed between 50 nanometers and 2 micrometers; and the thickness of the conductive hydrogel fiber film is between 5 and 100 micrometers.

6. The conductive hydrogel fiber membrane according to claim 1, characterized in that: The conductivity of the hydrogel fiber membrane is activated by infiltration with an ion-containing aqueous solution to achieve long-term repeated use.

7. A method for preparing the conductive hydrogel fiber membrane according to claim 1, characterized in that: It includes three steps: spinning-crosslinking-immersion: Step 1, a spinning method is to form a fiber membrane composed of gel material fibers containing a conductive component and a water-retaining agent, the method comprising one or more combinations of electrospinning, blow spinning, wet spinning, dry spinning or dry-jet wet spinning; Step 2: The cross-linking method is to make the fiber membrane insoluble in water, and the method includes one or more combinations of thermal crystallization, cold cross-linking, thermal cross-linking, chemical cross-linking or photo cross-linking; Step 3: The immersion method is to transform the fiber membrane into a conductive hydrogel fiber membrane, and the method comprises immersing the fiber membrane in an aqueous solution containing a water retaining agent, ions or a combination thereof.

8. A body signal measurement system for the conductive hydrogel fiber membrane according to claim 1, characterized in that: include: one or more conductive hydrogel fiber membranes; Signal acquisition and measurement module; A connection circuit provided between the signal acquisition and measurement module and the conductive hydrogel fiber membrane; The conductive hydrogel fiber membrane is attached to the surface of the measurement object.

9. The body signal measuring system of the conductive hydrogel fiber membrane according to claim 8, characterized in that: The body signal includes one or a combination of electrocardiogram, electromyogram, electroencephalogram, electrooculogram, strain, temperature, pressure or sweat.

10. The body signal measuring system of the conductive hydrogel fiber membrane according to claim 8, characterized in that: The signal acquisition and measurement module includes wired signal transmission, wireless signal transmission and a combination thereof.

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