CN113425864A

CN113425864A - Flexible and breathable MXene-based biomass skin electrode and preparation method and application thereof

Info

Publication number: CN113425864A
Application number: CN202110748567.7A
Authority: CN
Inventors: 刘楠; 宋德魁; 张岩; 赵艳
Original assignee: Beijing Normal University
Current assignee: Beijing Normal University
Priority date: 2021-07-02
Filing date: 2021-07-02
Publication date: 2021-09-24

Abstract

The invention relates to a flexible and breathable MXene-based biomass skin electrode and a preparation method and application thereof. The concentration, the reaction time and the temperature of a chemical reagent in the process of preparing the cellulose framework are regulated and controlled to completely remove lignin and hemicellulose in the herbaceous plant leaves, so that the cellulose framework with natural plant pore canals is obtained, the concentration of MXene nanosheets in the electrode preparation process is optimized, and the flexible breathable MXene-based biomass skin electrode is obtained. The flexible wearable MXene-based biomass electrode prepared by the invention has good conductivity and air permeability, can realize the acquisition of electrophysiological signals on the surface of human skin, and avoids the damage to the skin caused by air impermeability in the long-time real-time wearing process.

Description

Flexible and breathable MXene-based biomass skin electrode and preparation method and application thereof

The invention belongs to the technical field of flexible wearable electronic equipment and new materials, and particularly relates to a flexible breathable MXene-based biomass epidermal electrode, a preparation method and application thereof, in particular to an electrophysiological electrode patch assembled by using the breathable electrode.

Background

In recent years, with the increasing attention of people to human body skin movement detection and artificial limb control, biomedical research and personalized treatment, intelligent robots and human-computer interfaces, and global energy, research on wearable, portable and intelligent devices, especially electrophysiological electrodes, has been achieved. Real-time monitoring and feedback of human physiological signals, such as Electrocardiogram (ECG), Electrooculogram (EOG), Electromyogram (EMG), and electroencephalogram (EEG), are of great importance to health monitoring, individual treatment, and artificial intelligence devices. To obtain good signals, many researchers are interested in utilizing new materials (e.g., metal nanomembranes, metal nanowires and the like, carbon nanotubes and graphene, MXene, transition metal disulfides, conductive polymers, ionically conductive hydrogels, etc.) and structural design aspects (e.g., filamentous serpentine structures, porous structures, and ultra-thin electronic tattoos). However, long-term and non-irritating skin coupling is one of the main challenges of a satisfactory wearable device.

Although there has been a lot of research on fabrics to obtain intelligent long-term wearable breathable electronic fabrics, the quality of electrophysiological signals is not satisfactory. The natural, incredible process produces plants with their own unique structural arrangements. Millions of years of evolution have given plants excellent properties to adapt to the environment. Understanding the unique structure-function relationships of plants has stimulated researchers to explore the potential to learn materials from nature to meet the urgent needs of current energy and environmental technologies. In addition, highly conductive materials have a higher carrier density and surface electric field. The electrode has obvious conductivity, is beneficial to reducing ohmic loss, reducing noise, obtaining high-quality signals and improving the signal-to-noise ratio of measurement. Therefore, it is important to improve the conductivity of the electrode. Conventional rigid metal electrodes (Ag/AgCl or stainless steel electrodes) have excellent electrical conductivity but do not perform wearable functions, while flexible or stretchable electrodes typically have relatively low electrical conductivity. Therefore, it is imperative to develop highly conductive electrode materials to make flexible or stretchable skin electrodes.

Transition metal carbides and/or nitrides (MXenes) are a new class of two-dimensional materials that have received increasing attention in many respects, being the leading materials of two-dimensional materials. MXenes have abundant surface terminal functional groups (hydroxyl (OH), oxygen (O) or fluorine (F)) to impart excellent hydrophilicity, surface modification and functionalization (see documents 1 and 2). However, there are few reports of MXene implementation in electrophysiological electrodes (see documents 3, 4, 5), which are widely required by wearable devices for brain activity, heart health, muscle function and human-machine interaction. In order to prepare the electrophysiological electrode patch with high sensitivity and excellent air permeability, the invention selects a novel nano conductive material MXene, takes energy grass as an initial raw material, obtains a porous cellulose framework by treatment, and then loads MXene nanosheets to prepare the flexible air-permeable MXene electrophysiological electrode patch.

The above documents are as follows:

document 1: naguib M, Kurtoglu M, Presser V, et al, Two-dimensional nanocrystals produced by enhancement of Ti₃AlC₂. Adv Mater. 2011, 23 (37), 4248-4253。

Document 2: ZHao X, Wang L Y, Tang C, et al Smart Ti₃C₂T_x MXene Fabric with Fast Humidity Response and Joule Heating for Healthcare and Medical Therapy Applications. ACS Nano. 2020, 14 (7), 8793-8805。

Document 3: murphy B, Mulcahey P J, Driscoll N, et al. A Gel-Free Ti₃C₂T_x-Based Electrode Array for High-Density, High-Resolution Surface Electromyography. Adv Mater Technol. 2020, 5 (8): 2000325。

Document 4: driscoll N, Richardson A G, Maleski K, et al, Two-Dimensional Ti₃C₂ MXene for High-Resolution Neural Interfaces. ACS Nano. 2018, 12 (10): 10419-10429。

Document 5: wang Q, Pan X, Lin C, et al, Modified Ti₃C₂T_X (MXene) nanosheet-catalyzed self-assembled, anti-aggregated, ultra-stretchable, conductive hydrogels for wearable bioelectronics. Chemical Engineering Journal. 2020, 401: 126129。

Disclosure of Invention

Aiming at the defects of the prior art or the defects of the research content, the invention aims to provide a flexible and breathable MXene-based biomass skin electrode and a preparation method and application thereof, wherein MXene is dispersed on the surface of a cellulose skeleton in the MXene-based biomass skin electrode. The MXene sheet layer is lapped on the cellulose framework, and the natural porous structure of the plant can greatly improve the long-term wearing property and the air permeability of the electrode paste. And the concentration of the MXene nanosheets is adjusted (the concentration is 2-6 mg/ml, preferably 4 mg/ml) and the treatment steps of the chemical reagent sodium chlorite and sodium hydroxide etching process required in the preparation process are optimized, so that the MXene-cellulose electrode with an excellent air permeability and a porous structure can be obtained, wherein MXene lamella is overlapped on the surface of the framework, the high conductivity of the electrode is guaranteed, and the stability of the electrode in electromyographic signal detection is guaranteed. Natural porous structure, so that stable signal monitoring capability is exhibited in terms of long-term wear and breathability.

In order to achieve the purpose, the invention provides a flexible and breathable MXene-based biomass skin electrode which has a natural porous structure, wherein MXene sheet layers are overlapped on the surface of a cellulose skeleton.

As a further preferred aspect of the present invention, the cellulose skeleton is derived from leaves of an energy source herbaceous plant.

On the other hand, the invention also provides a preparation method of the MXene-based biomass skin electrode, which comprises the steps of taking an energy grass blade as a starting material, removing lignin and hemicellulose components to obtain a flexible porous cellulose framework, and then loading MXene nanosheets on the cellulose framework in a dipping mode to obtain the porous breathable MXene-based biomass skin electrode.

In a further preferred embodiment of the present invention, the process for preparing the flexible cellulose skeleton comprises using plant leaves as raw materials, and selectively removing lignin and hemicellulose components from plant cell walls by using a chemical solvent to obtain the cellulose skeleton.

As a further preferred aspect of the present invention, the chemical solvents are sodium chlorite and sodium hydroxide, respectively, and lignin and hemicellulose components are removed by a two-step process; wherein the sodium chlorite is dissolved in the weak acid acetic acid buffer solution, the concentration is 8-12 wt%, and more preferably, the pH value of the acetic acid buffer solution is 5, and the concentration is 10 wt%; the reaction temperature in sodium chlorite is 80-120 ℃, the reaction time is 4-6 hours, more preferably, the reaction temperature is 100 ℃, and the reaction time is 5 hours; the sodium hydroxide is in the form of aqueous solution, and the concentration of the sodium hydroxide is 6-10 wt%, and more preferably, the concentration of the sodium hydroxide is 8 wt%; the reaction temperature in sodium hydroxide is 60 to 90 ℃ and the reaction time is 1 to 3 hours, more preferably 80 ℃ and the reaction time is 2 hours.

In a further preferred embodiment of the present invention, the cellulose skeleton is immersed in an MXene aqueous dispersion having a concentration of 2 to 6 mg/ml, preferably 4 mg/ml. The concentration of the MXene aqueous dispersion has important influence on the conductivity of the flexible breathable MXene-based biomass skin electrode.

As a further preferable aspect of the present invention, the MXene aqueous dispersion contains MXene nanosheets, and the MXene nanosheets are obtained by selectively etching an a phase in a MAX phase with a mixed solution of hydrochloric acid and lithium fluoride; in the MAX phase, M is an early transition metal, A is a group III element or a group IV element, and X is mainly a C or N element; the MAX phase is preferably Ti₃AlC₂Selectively etching to remove intermediate phase Al phase, wherein MXene nanosheet isTi₃C₂T_xA sheet layer with the size of 800-1500 nm.

As a further optimization of the invention, the selective etching solution adopted by the selective etching is a mixed solution of hydrochloric acid and lithium fluoride, the etching time is 1 day, and finally, centrifugal washing is carried out at 3500 revolutions until the pH value is close to 6, and the monolayer MXene is obtained by ultrasonic stripping; a mixed solution was prepared using 20 ml of 9M hydrochloric acid and 1 g of lithium fluoride.

As a further preference of the present invention, after each step of preparing the flexible cellulose matrix, dialysis in deionized water is required to remove residual solvent. Freezing in refrigerator for 0.5 days, and lyophilizing for 2 days.

According to another aspect of the invention, the invention also protects the application of the flexible breathable MXene-based biomass epidermal electrode in preparing an electrode paste, wherein the electrode is a breathable electrode paste, and preferably a breathable electrophysiological electrode paste.

According to another aspect of the invention, the invention also protects a biomass raw material breathable electrophysiological electrode patch, wherein an active component of the electrophysiological electrode is the flexible breathable MXene-based biomass skin electrode, and MXene sheet layers are overlapped on the surface of the cellulose skeleton, so that the high conductivity and myoelectric signal detection stability of the electrode are ensured; natural porous structure, so that stable signal monitoring capability is exhibited in terms of long-term wear and breathability.

As a further preferred feature of the present invention, the air-permeable electrophysiological electrode patch further comprises a copper foil with the back surface bonded with a conductive silver adhesive as a current collector, and the electrode patch needs to be bandaged on the skin to achieve good electrophysiological signal detection.

In general, compared with the prior art, the flexible breathable MXene-based biomass skin electrode disclosed by the invention comprises a flexible cellulose skeleton and a conductive MXene nano-network loaded on the flexible cellulose skeleton in an impregnation mode. The concentration, the reaction time and the temperature of a chemical reagent in the process of preparing the cellulose framework are regulated and controlled to completely remove lignin and hemicellulose in the herbaceous plant leaves, so that the cellulose framework with natural plant pore canals is obtained, the concentration of MXene nanosheets in the electrode preparation process is optimized, and the flexible breathable MXene-based biomass skin electrode is obtained. The flexible wearable MXene-based biomass electrode prepared by the invention has good conductivity and air permeability, can realize the acquisition of electrophysiological signals on the surface of human skin, and avoids the damage to the skin caused by air impermeability in the long-time real-time wearing process.

The electrophysiological electrode paste prepared by the invention has high air permeability and long-term monitoring signal stability, wherein the active component is the flexible and air permeable MXene-based biomass epidermal electrode, the preparation process is simple, and large-area production can be realized. In addition, the plant leaves are used as raw materials, after lignin and cellulose are removed, MXene nanosheets are loaded, and the finally prepared electrode paste can be endowed with excellent conductivity and excellent air permeability.

The invention provides a novel material of an electrophysiological electrode paste capable of obtaining high air permeability and long-term wearing capacity, namely a flexible and air-permeable MXene-based biomass skin electrode with a natural porous structure. The obtained electrode has the capability of long-term stable acquisition of myoelectric and electrocardiosignal, the signal-to-noise ratio of the myoelectric signal is close to that of a commercial Ag/AgCl gel electrode, and the detection of the myoelectric signal of a normal human body can be realized. The detected electrocardiosignals also have normal P waves, QRS waves and T waves, and the states of atria and ventricles of the human body can be accurately reflected.

The flexible breathable MXene-based biomass epidermal electrode with the porous structure can effectively avoid complicated operation processes, finally forms a three-dimensional porous structure by utilizing the porous skeleton structure of the original natural plant, and can be simply assembled to prepare the breathable electrode paste with high conductivity and high air permeability.

Drawings

The following is further described with reference to the accompanying drawings:

FIG. 1 is a process flow diagram of the present invention;

FIG. 2 is a diagram of the microstructure of MXene preparation;

FIG. 3 is a scanning electron microscope image of a porous MXene-based biomass electrode;

fig. 4 is an MXene-based biomass electrode conductivity characterization;

FIG. 5 is a representation of the breathability of MXene-based biomass electrodes;

fig. 6 is an electrophysiological signal acquisition diagram of the MXene-based biomass electrode.

Detailed Description

In order to make the objects, embodiments and advantages of the present invention more clear and clearer, the following description is specifically illustrated with reference to the accompanying drawings. It is to be noted that the following description is only intended to illustrate the present invention, but not to limit the present invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention adopts a flexible and breathable MXene-based biomass skin electrode as an active material of an electrophysiological electrode, preferably selects a copper foil as a current collector, and detects a series of human physiological signals through electric signals.

The MXene nanosheet is obtained by selectively etching MAX phase by using a hydrochloric acid-lithium fluoride mixed solution; the MAX phase is preferably Ti₃AlC₂And etching to remove the intermediate phase Al phase.

Adding HCl (20 ml, 9M) and LiF (1 g) into a polytetrafluoroethylene cylindrical container, and uniformly stirring; then slowly adding the MAX phase into the mixed solution, naturally heating to room temperature for reaction for half an hour after the addition is finished, and then heating to 35 ℃ for reaction for 25 hours; centrifuging the product after reaction at 3500 rpm, and repeating for multiple times until the pH value of the supernatant is close to 6; collecting the final nearly neutral suspension, and ultrasonically stripping for one hour under the protection of argon; centrifuging the suspension obtained by ultrasonic stripping again for one hour at 3500 rpm, and collecting the centrifuged upper suspension to obtain MXene nanosheet dispersion liquid; the microstructure of the MAX phase and MXene is shown in FIG. 2.

The fiber framework obtained after the etching by the chemical solvent is immersed in the aqueous dispersion of the MXene nanosheet, and then the MXene-based biomass electrode is obtained by freeze drying, wherein a porous MXene-based biomass electrode electron microscope photo is shown in FIG. 3.

The prepared MXene-based biomass electrode has satisfactory conductivity, and as shown in FIG. 4, the electrodes are connected in series in a circuit with an LED lamp, so that the LED lamp can be found to have stable brightness in different environments, and the MXene-based biomass electrode is proved to have excellent stable conductivity. As shown in fig. 5, when an MXene-based biomass electrode was placed on the mouth of a glass bottle containing hydrochloric acid and a bottle of an aqueous ammonia solution was placed beside the electrode, it was found that the electrode had excellent gas permeability.

As shown in fig. 6, the electrode was used for detecting electrocardio-and myo-electric signals of a human body, and it was found that the electrode had electrophysiological signal detection quality comparable to that of a commercial electrode. And because of higher conductivity and excellent air permeability, the electrode can not generate heat and sweat accumulation when being stuck on the surface of the skin for a long time, is more comfortable to wear, and is a preparation method of the structure and the material of the air-permeable electrophysiological electrode.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. The flexible and breathable MXene-based biomass skin electrode is characterized by having a natural porous structure, wherein MXene sheets are lapped on the surface of a cellulose skeleton in the MXene-based biomass skin electrode.

2. The flexible breathable MXene-based biomass skin electrode of claim 1, wherein the cellulose matrix is derived from an energy grass blade.

3. The preparation method of the MXene-based biomass skin electrode as claimed in claim 1 or 2, wherein the MXene-based biomass skin electrode is obtained by taking an energy grass blade as a starting material, removing lignin and hemicellulose components to obtain a flexible porous cellulose skeleton, and then loading MXene nanosheets on the cellulose skeleton by means of impregnation.

4. The method according to claim 3, wherein the flexible cellulose skeleton is prepared by using plant leaves as raw materials and selectively removing lignin and hemicellulose components from plant cell walls by using a chemical solvent.

5. The method of claim 4, wherein the chemical solvent is sodium chlorite and sodium hydroxide, and lignin and hemicellulose components are removed by a two-step process; wherein the sodium chlorite is dissolved in the weak acid acetic acid buffer solution, the concentration is 8-12 wt%, and more preferably, the pH value of the acetic acid buffer solution is 5, and the concentration is 10 wt%; the reaction temperature in sodium chlorite is 80-120 ℃, the reaction time is 4-6 hours, more preferably, the reaction temperature is 100 ℃, and the reaction time is 5 hours; the sodium hydroxide is in the form of aqueous solution, and the concentration of the sodium hydroxide is 6-10 wt%, and more preferably, the concentration of the sodium hydroxide is 8 wt%; the reaction temperature in sodium hydroxide is 60 to 90 ℃ and the reaction time is 1 to 3 hours, more preferably 80 ℃ and the reaction time is 2 hours.

6. The method according to claim 3, characterized in that the cellulose matrix is immersed in an aqueous MXene dispersion having a concentration of 2-6 mg/ml, preferably 4 mg/ml.

7. The preparation method of claim 6, wherein the MXene aqueous dispersion contains MXene nanosheets obtained by selectively etching an A phase in a MAX phase with a mixed solution of hydrochloric acid and lithium fluoride; in the MAX phase, M is an early transition metal, A is a group III element or a group IV element, and X is mainly a C or N element; the MAX phase is preferably Ti₃AlC₂Selectively etching to remove intermediate phase Al phase, MXene NaThe rice flakes are Ti₃C₂T_xA sheet layer with the size of 800-1500 nm; more preferably, the selective etching solution adopted by the selective etching is a mixed solution of hydrochloric acid and lithium fluoride, the etching time is 1 day, and finally, centrifugal washing is carried out at 3500 revolutions until the pH value is close to 6, and the monolayer MXene is obtained by ultrasonic stripping; a mixed solution was prepared using 20 ml of 9M hydrochloric acid and 1 g of lithium fluoride.

8. The method of claim 5, wherein each step of preparing the flexible cellulosic scaffold is followed by dialysis against deionized water to remove residual solvent; freezing in refrigerator for 0.5 days, and lyophilizing for 2 days.

9. The use of the flexible breathable MXene-based biomass skin electrode of claim 1 or 2 or the flexible breathable MXene-based biomass skin electrode prepared by the preparation method of any one of claims 3-8 in preparing an electrode patch, wherein the electrode is a breathable electrode patch; preferably a breathable electrophysiological electrode patch.

10. A biomass raw material breathable electrophysiological electrode patch is characterized in that an active component of an electrophysiological electrode is the flexible breathable MXene-based biomass skin electrode of claim 1 or 2 or the flexible breathable MXene-based biomass skin electrode prepared by the preparation method of any one of claims 3 to 8, and in an electrode structure, MXene sheet layers are overlapped on the surface of a cellulose skeleton; preferably, the air-permeable electrophysiological electrode patch further comprises a copper foil bonded with conductive silver adhesive on the back surface as a current collector, and the electrode patch needs to be bound on the skin by a bandage to realize good electrophysiological signal detection.